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Case Studies (329)

Monday, 16 October 2017 08:46

Primary Production in the Arctic Ocean

Written by Juan Carlos

Primary Production in the Arctic Ocean

Main Contributors:

Patricia Villarrubia Gomez, Helene Albinus Søgaard, Karl Samuelsson, Sophie Laggan

Other Contributors:

Thorsten Blenckner

Summary

 A shift from polar to temperate primary production (PP) patterns has been detected in the Arctic Ocean. Following a regime shift in the North Atlantic in 1995, similar structural changes are now occurring in Arctic waters. Rapid warming of atmospheric and oceanic temperatures has caused a near year-on-year decline in the extent and thickness of summer sea ice since 1979 (NSIDC 2014). Anthropogenic climatic change has extended the growing season and delayed August freeze-up through a decline in albedo reflectivity and enhanced wind-driven vertical mixing. Natural modes of variability at the lower latitudes has also led to poleward shifts of temperate marine species and caused pronounced phenological changes to primary producers. The difference in the temporal scale of these forcing mechanisms makes it hard to predict which event is causing changes to PP. It is uncertain what impact this change will have on the food web of this ecosystem.

Type of regime shift

Ecosystem type

  • Marine & coastal
  • Polar

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Arctic Ocean

Region

  • Arctic ocean

Countries

  • Norway
  • United Kingdom
  • Canada
  • Iceland

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Aagaard, K., Carmarck, E.C., 1989. The Role of Sea Ice and other Fresh Water in the Arctic Circulation, Journal of Geophysical Research, 94, C10, pp. 14485-14498.
  2. Arctic Council, 2013. Arctic Resilience Interim Report 2013. Stockholm Environment Institute and Stockholm Resilience Centre, Stockholm.
  3. Ardyna M., Babin M., Gosselin M., Devred E., Rainville L., and Tremblay A-É., 2014. Recent Arctic Ocean sea ice loss triggers novel fall phytoplankton blooms. Geophysical Research Letters, 41, 17, pp. 6207–6212.
  4. Bascompte, J., C. Melian, and Sala E., 2005. Interaction strength combinations and the overfishing of a marine food web. Proceedings Of The National Academy Of Sciences Of The United States Of America, 102, pp. 5443–5447.
  5. Bates, N.R., and Mathis, J.T., 2009. The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks, Biogeosciences, 6, pp. 2433-2459.
  6. Butler, C.D., and Oluoch-Kosura, W., 2011. Linking Future Ecosystem Services and Future Human Well-being, Ecology and Society,11
  7. Chylek, P., Folland, C.K., Lesins, G., Dubey, M.K., and Wang, M., 2009. Arctic air temperature change amplification and the Atlantic Multidecadal Oscillation, Geophysical Research Letters, 36, 14, L14801, doi:10.1029/2009GL038777.
  8. Curry, J.A., Schramm, J.L., and Ebert, E.E., 1995. Sea Ice-Albedo Climate Feedback Mechanism. J. Climate, 8, 240–247.
  9. Dicks L., Almond R., and McIvor A., 2011 (eds.) Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost, Arctic Monitoring and Assessment Programme (AMAP) Arctic SWIPA Overview Report. DOI: 10.1088/1748-9326/4/4/045108
  10. Falk-Petersen S., Timofeev S., Pavlov V., Sargent J.R., 2007, Climate variability and possible effects on arctic food chains: The role of Calanus. In: Ørbæk J.B.,Tombre T., Kallenborn R., Hegseth E., Falk-Petersen S., Hoel A.H. (eds.), Arctic Alpine Ecosystems and People in a Changing Environment, Springer Verlag, Berlin. 433 p
  11. Frey, K.E., Arrigo, K.R., Gradiner, R.R., Arctic Ocean Primary Productivity, 2011. Arctic Report Card: Update for 2011. www.arctic.noaa.gov/report11/primary_productivity.html
  12. Greene, Charles H., Pershing, Andrew J., Cronin, Thomas M., and Ceci, N., 2008. Arctic climate change and its impacts on the ecology of the north Atlantic. Ecology 89, 11, pp. 24 - 38.
  13. Hassan, R.M., Scholes, R., Ash, N., (eds.) 2005. Ecosystems and Human Wellbeing: Current State and Trends: Findings of the Conditions and Trends Working Group. Island Press
  14. Hátún, H., Payne M.R., Beaugrandd G., Reide P.C., Sandøb A.B., Drangeg H., Hansena B., Jacobsena J.A., and Blochi D., 2009. Large bio-geographical shifts in the north-eastern Atlantic Ocean: From the subpolar gyre, via plankton, to blue whiting and pilot whales. Progress in Oceanography 80, 3-4, 149–162.
  15. Hátún, H., Sando, A.B., Drange, H., Hansen, B., and Valdimarsson, H., 2005. Influence of the Atlantic subpolar gyre on the thermohaline circulation. Science 309, 1841– 1844.
  16. Hawkins, E., and R. Sutton, 2009. The potential to narrow uncertainty in regional climate predictions. Bulletin of the American Meteorological Society, 90, 1095-1107, doi:10.1175/2009BAMS2607.1.
  17. Heckendorn, P., Weisenstein, D., Fueglistaler, S., Luo, B. P., Rozanov, E., Schraner, M., Thomason L. W., and Peter, T., 2009. The impact of geoengineering aerosols on stratospheric temperature and ozone. Environmental Research Letters 4 045108.
  18. Henson, S.A., Dunne, J.P. and Sarmiento, J.L., 2009. Decadal variability in North Atlantic phytoplankton blooms. Journal of Geophysical Research: Oceans (1978–2012), 114, C4, DOI: 10.1029/2008JC005139.
  19. Hinzman, L.D., Bettez, N.D., Bolton, W. R., Chapin, F. S., Dyurgerov, M. B., Fastie, C. L., and Yoshikawa, K., 2005. Evidence and implications of recent climate change in northern Alaska and other arctic regions. Climatic Change,72, 3, pp. 251-298.
  20. Hjarnmann, D.Ø., Bogstad, B., Eikeset, A.M., Ottersen, G., Gjøsæter, H., Stenseth, N.C., 2006. Food web dynamics affect Northeast Arctic cod recruitment. Proceedings of Royal Society B 274, pp. 661–669.
  21. Kriegsmann, A., Brümmer B., 2014. Cyclone impact on sea ice in the central Arctic Ocean: a statistical study. The Cryosphere, 8, pp. 303–317.
  22. Lenaerts, J.T.M., van Angelen, J.H., van den Broeke, M.R., Gardner, A.S., Wouters, B., van Meijgaard, E., 2013. Irreversible mass loss of Canadian Arctic Archipelago glaciers. Geophysical Research Letters, 40, pp. 1-5.
  23. Li, W.K.W., McLaughlin, F.A., Lovejoy, C., and Carmack, E.C., 2009. Smallest algae thrive as the Arctic Ocean freshens. Science, 326, 539.
  24. Masson-Delmotte, V., Swingedouw, D., Landais, A., Seidenkrantz, M-S., Gauthier, E., Bichet, V., Massa C., Perren, B., Jomelli, V., Adalgeirsdottir G., Hesselbjerg Christensen, J., Arneborg, J., Bhatt, U., Walker, D.A., Elberling, B., Gillet-Chaulet, F., Ritz, C., Gallée, H., van den Broeke, M., Fettweis, X., de Vernal, A., and Vinther, B., 2012, Greenland climate change: from the past to the future. Wiley Interdisciplinary Reviews: Climate Change, 3, 5, pp. 427–449.
  25. Moore, S. E. & Huntington, H. P., 2008. Arctic marine mammals and climate change: Impacts and resilience. Ecological Applications 18, pp. 157-165.
  26. Niiranen, S., Peterson, G., Biggs, R., Rocha, J.C., and Österblom, H. Marine food webs: community change and trophic level decline. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2014-10-15 03:05:20 GMT. NSIDC 2014. http://nsidc.org
  27. Post, E., Mads C. Forchhammer, M.C., Bret-Harte, M.S., Callaghan, T.V., Christensen, T.R., Elberling, B., Fox, A.D., Olivier Gilg, O., Hik, D.S., T. Høye, T.T., Ims, R.A., Jeppesen, E., R. Klein, D.R., Madsen, J., McGuire, A.D., Rysgaard, S., Schindler, D.E., Ian Stirling, I., Tamstorf, M.P., Tyler, N.J.C., van der Wal, R., Welker, J., Wookey, P.W., Schmidt, N.M., and Aastrup, P., 2009. Ecological Dynamics Across the Arctic Associated with Recent Climate Change Eric Post et al. Science 325, 1355, doi: 10.1126/science.1173113.
  28. Rahmstorf, S. and Ganopolski, A., 1999. Long-term global warming scenarios computed with an efficient coupled climate model. Climatic Change 43, pp. 353 - 367.
  29. Schlesinger M.E., and Ramankutty N., 1994. An oscillation in the global climate system of period 65–70 years. Nature, 367, pp. 723–726.
  30. Shadwick, E.H, Trull, T.W., Thomas, H., and Gibson J.A.E, 2013. Vulnerability of Polar Oceans to Anthropogenic Acidification: Comparison of Arctic and Antarctic Seasonal Cycles. Scientific Reports 3, 2339 doi:10.1038/srep02339.
  31. Shimada, K., Kamoshida, T., Itoh, M., Nishino, S., Carmack, E., Mclaughlin, F., Zimmermann, S., Proshotinsky, A., 2006. Pacific Ocean inflow: Influence on catastrophic reduction of sea ice cover in the Arctic Ocean. Geophysical Research Letters. 33, L08605.
  32. Sirevaag, A., de la Rosa, S., Fer, I., Nicolaus, M., Tjernström N., McFee, M.G., 2011. Mixing, heat fluxes and heat content evolution of the Arctic Ocean mixed layer. Ocean Sci., 7, 335–349.
  33. Stein, R., and Macdonald, R.W., 2004. The Organic Carbon Cycle in the Arctic Ocean. Springer Science & Business Media.
  34. Straneo, F., and Heimbach, P., 2013. North Atlantic warming and the retreat of Greenland's outlet glaciers Nature 504, pp. 36–43 doi:10.1038/nature12854.
  35. Stroeve, J., Holland, M.M., Meier W., Scambos T., and Serreze, M., 2007. Arctic sea ice decline: Faster than forecast. Geophysical Research Letters, 34, L09501, doi:10.1029/2007GL029703.
  36. Tremblay, J.É., S. Bélanger, D. G. Barber, M. Asplin, J. Martin, G. Darnis, L. Fortier, Y. Gratton, H. Link, P. Archambault, A. Sallon, C. Michel, W. J. Williams, B. Philippe, and M. Gosselin (2011), Climate forcing multiplies biological productivity in the coastal Arctic Ocean, Geophys. Res. Lett., 38, L18604, doi:10.1029/2011GL048825.
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  38. Wassmann, P., Duarte, C.M. Agustí, S., Sejr, M.K., 2011. Footprints of climate change in the Arctic marine ecosystem. Global Change Biology, 17, pp. 1235–1249, doi:10.1111/j.1365-2486.2010.02311.
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Citation

Patricia Villarrubia Gomez, Helene Albinus Søgaard, Karl Samuelsson, Sophie Laggan, Thorsten Blenckner. Primary Production in the Arctic Ocean. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-10-16 18:30:40 GMT.
Monday, 16 October 2017 08:12

Arctic Benthos Borealisation

Written by Juan Carlos

Arctic Benthos Borealisation

Main Contributors:

Sara Andersson, Noah Linder, Katharina Fryers Hellquist, Linn Järnberg

Other Contributors:

Thorsten Blenckner, Juan Carlos Rocha

Summary

A regime shift occurred on the west coast of Svalbard in 1996 and 2000; the former Arctic benthos was mainly constituted by red calcareous algae and filter feeders whereas the present subarctic benthos is dominated by macroalgae. The main drivers of this shift are increases in sea surface temperature and inflow of light that are both due to global warming and changes in the North Atlantic Oscillation. Changes in benthos could impact other trophic levels, potentially affecting commercial fisheries as well as tourism. The implications for ecosystem services and human well-being are highly uncertain. Management options are mainly to reduce greenhouse gases to combat global warming and an adaptive management approach is also proposed on a local scale. 

Type of regime shift

Ecosystem type

  • Marine & coastal
  • Polar

Land uses

  • Fisheries
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Arctic Ocean

Region

  • Svalvard

Countries

  • Svalbard

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Holling, C. S. 1978. Adaptive Enviromental Assessment and Management. New York: John Wiley & Sons.
  2. Beuchel, Frank, Bjørn Gulliksen, and Michael L. Carroll. 2006. “Long-Term Patterns of Rocky Bottom Macrobenthic Community Structure in an Arctic Fjord (Kongsfjorden, Svalbard) in Relation to Climate Variability (1980–2003).” Journal of Marine Systems 63(1-2):35–48.
  3. Bischoff, B., and C. Wiencke. 1993. “Temperature Requirements for Growth and Survival of Macroalgae from Disko Island (Greenland).” Helgoländer Meeresuntersuchungen 47(2):167–91.
  4. Drinkwater, Kenneth F. 2006. “The Regime Shift of the 1920s and 1930s in the North Atlantic.” Progress in Oceanography 68(2-4):134–51.
  5. Grebmeier, Jacqueline M. et al. 2006. “A Major Ecosystem Shift in the Northern Bering Sea.” Science (New York, N.Y.) 311(5766):1461–64.
  6. IPCC. 2013. Climate Change 2013: The Physical Science Basis. Cambridge, United Kingdom andNew York, NY, USA: Cambridge University Press.
  7. Johansen, H. W. 1981. Coralline Algae, A First Synthesis. CRC Press.
  8. Johansen, H. W. 1981. Coralline Algae, A First Synthesis. CRC Press. Kortsch, Susanne et al. 2012. “Climate-Driven Regime Shifts in Arctic Marine Benthos.” Proceedings of the National Academy of Sciences of the United States of America 109(35):14052–57. Snelgrove, Paul V. R. 1999. “Getting to the Bottom of Marine Biodiversity : Sedimentary Habitats Ocean Bottoms Are the Most Widespread Habitat on Earth and Support High Biodiversity and Key Ecosystem Services.” BioScience 49(2):129–38. Viken, Arvid. 2010. “Tourism, Research, and Governance on Svalbard: A Symbiotic Relationship.” Polar Record 47(04):335–47. Weslawski, Jan M. et al. 2011. “Climate Change Effects on Arctic Fjord and Coastal Macrobenthic Diversity—observations and Predictions.” Marine Biodiversity 41(1):71–85.
  9. Kortsch, Susanne et al. 2012. “Climate-Driven Regime Shifts in Arctic Marine Benthos.” Proceedings of the National Academy of Sciences of the United States of America 109(35):14052–57.
  10. Snelgrove, Paul V. R. 1999. “Getting to the Bottom of Marine Biodiversity : Sedimentary Habitats Ocean Bottoms Are the Most Widespread Habitat on Earth and Support High Biodiversity and Key Ecosystem Services.” BioScience 49(2):129–38. Viken, Arvid. 2010. “Tourism, Research, and Governance on Svalbard: A Symbiotic Relationship.” Polar Record 47(04):335–47.
  11. Snelgrove, Paul V. R. 1999. “Getting to the Bottom of Marine Biodiversity : Sedimentary Habitats Ocean Bottoms Are the Most Widespread Habitat on Earth and Support High Biodiversity and Key Ecosystem Services.” BioScience 49(2):129–38. Viken, Arvid. 2010. “Tourism, Research, and Governance on Svalbard: A Symbiotic Relationship.” Polar Record 47(04):335–47. Weslawski, Jan M. et al. 2011. “Climate Change Effects on Arctic Fjord and Coastal Macrobenthic Diversity—observations and Predictions.” Marine Biodiversity 41(1):71–85.
  12. Weslawski, Jan M. et al. 2011. “Climate Change Effects on Arctic Fjord and Coastal Macrobenthic Diversity—observations and Predictions.” Marine Biodiversity 41(1):71–85.

Citation

Sara Andersson, Noah Linder, Katharina Fryers Hellquist, Linn Järnberg, Thorsten Blenckner, Juan Carlos Rocha. Arctic Benthos Borealisation. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-10-16 18:30:19 GMT.

Invasive floating plant dominance to invasive submerged plant dominance in South African freshwater systems

Main Contributors:

Emily Strange

Other Contributors:

Julie Coetzee, Julie Coetzee

Summary

As naturally occurring large bodies of freshwater are rare in South Africa there are numerous man-made dams and lakes, these systems are highly vulnerable to colonization from non-native invasive plants due to multiple factors. Firstly, there is a lack of native aquatic plant species to occupy the water column and compete for resources. Secondly they are often eutrophic systems, caused by anthropogenic activity such as intensive agriculture and improper human waste disposal, and nutrient loading is a known driver of invasive plants. Also, it has been argued that the intrinsic nature of freshwater systems leads them to be disproportionately affected by non native invasive species when compared with terrestrial systems (Moorhouse and McDonald 2015).

This combination has lead to a long battle against floating invasive plants that dominate many of South Africa’s freshwater resources.. These plants form dense mats on the waters surface, restricting light to other species, damaging hydroelectric equipment, limiting water quality and reducing biodiversity. They can also play host to vectors of disease such as malari and schistosomiasis (Mack and Smith, 2011). The implementation of classical biological control programs, using the natural enemies of the invasive plants, has proven to be a huge success when controlling detrimental invasive plants such as water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes L. (Araceae)), Kariba weed (Salvinia molesta D.S. Mitchell (Salviniaceae)), parrots feather (Myriophyllum aquaticum (Vellozo Conceição) Verdcourt) and red water fern (Azolla filiculoides Lamarck (Azollaceae)) (Hill 2002)

The host-specific biological control agents (BCAs), typically insects and mites, have coevolved with the plants in their natural range and are intentionally introduced to manage invasive plant populations.

The overall aim of this is to induce a regime shift into a functioning system with high native biodiversity and freshwater access. However, we propose that whilst the BCAs do lead to a dramatic reduction in the biomass and health of the floating plant, it can also act as a catalyst inducing a shift into a second degraded stable regime. This second regime is one that is dominated by submerged invasive plants. The establishment of the BCAs on the floating plants can lead to a rapid plant population crash and the nutrients they were locking up are released. At the same time submerged light levels are restored in the water column, enabling a new suite of submerged invasive plants to flourish. The increase in space, light and nutrients promotes the submerged plant growth and as they continue to photosynthesize the levels of dissolved oxygen in the water rise. This improvement in water quality, alongside a limited number of native submerged plants to compete with, helps to establish and maintain this second stable regime (invasive submerged plant dominance). These rooted plants can alter water flow, turbidity and sediment stabilization (Yarrow et al. 2009). They can also degrade water quality and biodiversity, restrict access to freshwater and damage hydro-electrical equipment.

Type of regime shift

Ecosystem type

  • Freshwater lakes & rivers

Land uses

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots, dairies)
  • Extensive livestock production (natural rangelands)
  • Conservation
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Africa

Region

  • South Africa

Countries

  • South Africa

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Charles H & Dukes JS. 2007. Impacts of invasive species on ecosystem services. Biological Invasions; Ecological Studies 193.
  2. Coetzee et al. 2011 Prospects for the biological control of submerged macrophytes in South Africa. African Entomology : Biological control of invasive alien plants in South Africa (1999 - 2010): Special Issue 2.
  3. Coetzee J & Hill MP. 2012. The role of eutrophication in the biological control of water hyacinth, Eichhornia crassipes, in South Africa. BioControl 57, 247-261.
  4. Hill MP. 2002. The impact and control of alien aquatic vegetation in South African aquatic ecosystems. African Journal of Aquatic Science 28, 19-24
  5. Mack RN & Smith MC. 2011. Invasive plants as catylsts for the spread of human parasites. NeoBiota 9, 13-29.
  6. Martin GD & Coetzee JA. 2011. Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa. Water SA [online] 37, pp. 371-380. ISSN 0378-4738
  7. McConnachie J, de Wit, MP, Hill MP, Byrne MJ. Economic evaluation of the successful biological control of Azolla filiculoides in South Africa, Biological Control, 28 (1) ISSN 1049-9644.
  8. Moorhouse and McDonald. 2015. Are invasives worse in freshwater than terrestrial ecosystems? Wiley Periodicals
  9. Yarrow M, Marin VH, Finlayson M, Tironi A, Delgado LE & Fishcher F. 2009. The ecology of Egeria densa Planchon (Liliopsida: Alismatales): A wetland ecosystem engineer? Revista Chilena de Historia Natural 82, 299-313.

Citation

Emily Strange, Julie Coetzee, Julie Coetzee. Invasive floating plant dominance to invasive submerged plant dominance in South African freshwater systems. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-08-27 10:46:02 GMT.

Megadiverse fynbos shrublands to invasive wattle tree monoculture.

Main Contributors:

Ross Shackleton

Other Contributors:

Reinette (Oonsie) Biggs, Dave Richardson

Summary

The southwestern tip of Africa is home to the Fynbos biome (Cape Floristic Region), which is characterised by highly diverse plant groups, many of which are endemic and occur nowhere else in the world. Numerous species of Australian acacia (wattles) were introduced to South Africa for multiple reasons, including sand/dune stabilisation, ornamental purposes, and forestry. Many species have subsequently naturalised and some are widespread invaders. The Australian wattles have filled an empty niche (trees in a virtually treeless system) causing a regime shift. This shift has induced many negative impacts to the social-ecological system in the area. These include alterations to fire and hydrological systems, changes in soil nutrient cycles, biodiversity loss, and negative impacts on local livelihoods and human well-being through loss of grazing, water supply, ecotourism and increased exposure to natural hazards. Ongoing management interventions include mechanical and chemical control and the use of biological control agents.

Type of regime shift

  • Introduction of aline species (Biological invasions)

Ecosystem type

  • Mediterranean shrubs (egFynbos)

Land uses

  • Urban
  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Extensive livestock production (natural rangelands)
  • Timber production
  • Conservation
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Africa

Region

  • Western Cape, South Africa

Countries

  • South Africa

Locate with Google Map

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Allsopp N. 2014. Fynbos: ecology, evolution and conservation of a megadiverse region. Oxford University Press, USA.
  2. Blackburn T, et al. 2011. A proposed unified framework for biological invasions. Trends in Ecology and Evolution, 26, 333-339.
  3. Charles H, and Dukes JS. 2008. Impacts of invasive species on ecosystem services. In: Biological Invasions, Nentwig, W. (ed). Springer, Berlin. pp 217-237.
  4. Gaertner M, et al. 2014. Invasive plants as drivers of regime shifts: identifying high-priority invaders that alter feedback relationships. Diversity and Distributions 20,733-744.
  5. Le Maitre D, et al 1996. Invasive plants and water resources in the Western Cape province, South Africa; Modeling and the consequences of a lack of management. Journal of Applied Ecology 33, 161-172.
  6. Le Maitre D, et al. 2011 Impacts of invasive Australian acacias: implications for management and restoration. Diversity and Distributions 17, 1015-1029.
  7. Richardson DM, et al. 1989. Reductions in plant species richness under stands of alien trees and shrubs in the fynbos biome. South African Forestry Journal 149,1-8.
  8. Shackleton CM, et al 2007. Assessing the effects of alien species on rural livelihoods; case examples and a framework from South Africa. Human Ecology 35, 113-127.
  9. Turpie J, et al. 2003. Economic value of terrestrial and marine biodiversity in the Cape Floristic Region: implications for defining effective and socially optimal conservation strategies. Biological Conservation 122, 233-251.
  10. van Wilgen BW, et al 2012. An assessment of the effectiveness of a large national-scale invasive alien plant control strategy in South Africa. Biological Conservation 148, 28-38.
  11. van Wilgen BW, et al. 2011. National-scale strategic approaches for managing introduced plants: Insights from Australian acacias in South Africa. Diversity and Distributions 17, 1060-1075.
  12. Wilson JRU, et al. 2013. A new national unite for invasive species detection, assessment and eradication planning. South African Journal of Science 109, 1-13.

Citation

Ross Shackleton, Reinette (Oonsie) Biggs, Dave Richardson. Megadiverse fynbos shrublands to invasive wattle tree monoculture. . In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-07-25 05:17:24 GMT.
Sunday, 05 March 2017 16:28

Mediterranean Basin

Written by Juli Pausas

Mediterranean Basin

Main Contributors:

Juli Pausas

Other Contributors:

Summary

In the European region of the Mediterranea Basin there was an abrupt fire regime shift in such a way that fires increased in annual frequency (doubled) and area burned (by about an order of magnitude). The main driver of this shift was the increase in fuel amount and continuity due to rural depopulation (vegetation and fuel build-up after farm abandonment) suggesting that fires were fuel-limited previous to the shift. Climatic conditions are poorly related to wildfire activity during the pre-shift period and strongly related during the to post-shift period, suggesting that fires are currently less fuel limited and more drought-driven than before. Thus, the fire regime shift implies also a shift in the main driver for fire activity. This shift was dated in the 1970s in Spain but this may varies in other countries.




Type of regime shift

  • Fire regime shift

Ecosystem type

  • Mediterranean shrubs (egFynbos)

Land uses

  • Small-scale subsistence crop cultivation

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Europe

Region

  • Mediterranean Basin

Countries

  • Spain
  • Greece

Locate with Google Map

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226.
  2. Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. http://dx.doi.org/10.1007/s10584-011-0060-6

Citation

Juli Pausas. Mediterranean Basin. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-03-09 16:22:33 GMT.
Friday, 08 January 2016 16:52

Vegetation regime shifts in Yamal-Nenets

Written by Hanna Ahlström

Vegetation regime shifts in Yamal-Nenets

Main Contributors:

Hanna Ahlström, Jonas Gren, Ashley Perl, Fernando Remolina, Fernando Remolina, Ashley Perl, Jonas Gren

Other Contributors:

Summary

The Yamal-Nenets social-ecological system comprises about 5000 nomadic reindeer herders and 300 000 semi-domestic reindeers, moving with the seasons in 21 different brigades from the southern tree limit up north, across the Arctic tundra. Shrub encroachment has been observed during the last three decades, but has been controlled by reindeer grazing. These changes have produced two regime states: shrubland without reindeer herding, and open land with reindeer herding. The first regime is mainly caused by temperature increase, which has produced warmer winters, summers and extended growing seasons. These temperature changes have altered the controlling feedbacks of the tundra, such as slow growth of shrubs, microbial activity, and decomposition litter rates. This regime is hence seen as the undesirable regime for the Yamal-Nenets social-ecological system.

Type of regime shift

Ecosystem type

  • Grasslands
  • Tundra
  • Polar
  • Agro-ecosystems

Land uses

  • Extensive livestock production (natural rangelands)

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Asia
  • Europe

Region

  • Yamal Peninsula, Northwest Siberia

Countries

  • Russia

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Aune, S., Hofgaard, A., & Söderström, L. 2011. Contrasting climate- and land-use-driven tree encroachment patterns of subarctic tundra in northern Norway and the Kola. Canadian Journal of Forest Research, 41(3), 437–449.
  2. Bråthen, K. A., Ims, R. a., Yoccoz, N. G., Fauchald, P., Tveraa, T., & Hausner, V. H. 2007. Induced Shift in Ecosystem Productivity? Extensive Scale Effects of Abundant Large Herbivores. Ecosystems, 10(5), 773–789.
  3. Couture, T., and Gagnon, Y. 2010. An analysis of feed-in tariff remuneration models: Implications for renewable energy investment. Energy policy 38 (10), 955-965. Degteva, A., & Nellemann, C. (2013). Nenets migration in the landscape: impacts of industrial development in Yamal peninsula, Russia. Pastoralism: Research, Policy and Practice, 3(1), 15.
  4. Forbes, B. C., Stammler, F., Kumpula, T., Meschtyb, N., Pajunen, A., & Kaarlejärvi, E. 2009. High resilience in the Yamal-Nenets social-ecological system, West Siberian Arctic, Russia. Proceedings of the National Academy of Sciences of the United States of America, 106(52), 22041–8.
  5. Golovatin, M. G., Morozova, L. M., & Ektova, S. N. 2012. Effect of reindeer overgrazing on vegetation and animals of tundra ecosystems of the Yamal peninsula, Czech Polar reports, 2(12), 80–91
  6. Grace, J., Berninger, F., & Nagy, L. 2002. Impacts of Climate Change on the Tree Line. Annals of Botany, 90(4), 537–544.
  7. Henden, J.-A., Yoccoz, N. G., Ims, R. a, & Langeland, K. 2013. How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra. PloS one, 8(5),1-10.
  8. Kullman, L. 2002. Rapid recent range-margin rise of tree and shrub species in the Swedish Scandes. Journal of Ecology, 90(1), 68–77.
  9. Kumpula, T., Forbes, B. C., Stammler, F., & Meschtyb, N. 2012. Dynamics of a Coupled System: Multi-Resolution Remote Sensing in Assessing Social-Ecological Responses during 25 Years of Gas Field Development in Arctic Russia. Remote Sensing, 4(12), 1046–1068.
  10. Kumpula, T., Pajunen, A., Kaarlejärvi, E., Forbes, B. C., & Stammler, F. 2011. Land use and land cover change in Arctic Russia: Ecological and social implications of industrial development. Global Environmental Change, 21(2), 550–562.
  11. Macias-Fauria M, Forbes BC, Zetterberg P, Kumpula T. 2012. Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems. Nature Climate Change 2, 613–618.
  12. Myers-Smith, I. H. 2007. Shrub Line Advance in Alpine Tundra of the Kluane Region: Mechanisms of Expansion and Ecosystem Impacts. Arctic, 60(4), 447-451.
  13. Olofsson, J., Oksanen, L., Callaghan, T., Hulme, P. E., Oksanen, T., & Suominen, O. 2009. Herbivores inhibit climate-driven shrub expansion on the tundra. Global Change Biology, 15(11), 2681–2693.
  14. Strum, M., Douglas, T., Racine, C., & Liston, G. E. 2005. Chagning snow and shrub conditions affect albedo with global implications. Journal of Geophysical Research, 110, 2156-2202.
  15. Sturm, M., Schimel, J., Michaelson, G., Welker, J. M., Oberbauer, S. F., Liston, G. E., … Romanovsky, V. E. 2005. Winter Biological Processes Could Help Convert Arctic Tundra to Shrubland. BioScience, 55(1), 17-26.
  16. Tape, K., Sturm, M., & Racine, C. 2006. The evidence for shrub expansion in Northern Alaska and the Pan-Arctic. Global Change Biology, 12(4), 686–702.
  17. Wal, V. D. R., 2006. Do herbivores cause habitat degradation or vegetation state transition ? Evidence from the tundra. Oikos, 114:1, 177–186.
  18. Walker, D. A., Forbes, B. C., Leibman, M. O., Epstein, H. E., Bhatt, U. S., Comiso, J. C., … Yu, Q. 2011. Eurasian Arctic Land Cover and Land Use in a Changing Climate. (G. Gutman & A. Reissell, Eds.), 207–236.
  19. Walker, M. D., C. Wahren, H., Hollister, R. D., Henry, G. H. R., Ahlquist, L. E., Alatalo, J., … Wookey, P. A. 2006. Plant community responses to experimental warming across the tundra biome PNAS, 103(5), 1342-1346.
  20. Yu, Q., Epstein, H. E., Walker, D. a, Frost, G. V, & Forbes, B. C. 2011. Modeling dynamics of tundra plant communities on the Yamal Peninsula, Russia, in response to climate change and grazing pressure. Environmental Research Letters, 6(4),1-12.
  21. Zeng, H., Jia, G., & Forbes, B. C. 2013. Shifts in Arctic phenology in response to climate and anthropogenic factors as detected from multiple satellite time series. Env. Rev. Lett., 8, 1–12.
  22. Zimov, A. S. A., Chuprynin, V. I., Oreshko, A. P., Iii, F. S. C., & Reynolds, J. F. 1995. Steppe-Tundra Transition : A Herbivore-Driven Biome Shift at the End of the Pleistocene American Naturalist 146(5), 765–794.

Citation

Hanna Ahlström, Jonas Gren, Ashley Perl, Fernando Remolina, Fernando Remolina, Ashley Perl, Jonas Gren. Vegetation regime shifts in Yamal-Nenets. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-08 10:45:18 GMT.

Collapse of Newfoundland cod fisheries, Northwest Atlantic

Main Contributors:

Roweena Patel, Kate Williman, Viveca Mellegard, Philipp Siegel, Kate Williman, Viveca Mellegard, Philipp Siegel

Other Contributors:

Reinette (Oonsie) Biggs, Juan Carlos Rocha

Summary

The Newfoundland cod fishery is a social-ecological system that is centered upon Arctic cod, Gadus morhua populations in the waters off Newfoundland and Labrador in the Northwest Atlantic. High fishing pressure, along with regional climatic variability that delivered colder water to the Northwest Atlantic ocean, disturbed the cod spawning grounds and led to a dramatic cod fishery collapse. Recovery in the fishery has been minimal and very slow, partly because cod population growth will take time to replenish the amount of stock that was lost. This regime shift has impacted ecosystem services by reducing the food source both at the local and the global scale. There has also been a loss of income from cod fishing at the local scale that affects human wellbeing among Newfoundland fishers and the communities relying directly and indirectly on the fishing industry. Actions taken to restore the cod regime shift includes banning of the commercial fisheries in the Northwest Atlantic, tighter regulations and dock-side monitoring programs.

Type of regime shift

Ecosystem type

  • Marine & coastal

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • North America
  • Atlantic Ocean

Region

  • Northern North Atlantic

Countries

  • Canada

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Arnason, R., Sandal, L. K., Steinshamn, S. I., & Vestergaard, N. (2004). Optimal Feedback Controls: Comparative Evaluation of the Cod Fisheries in Denmark, Iceland, and Norway. American Journal of Agricultural Economics, 86(2): 531-542.
  2. Bavington, D. (2010). From hunting fish to managing populations: fisheries science and the destruction of Newfoundland cod fisheries. Science as Culture, 19(4), 509-528.
  3. Berec, L., Angulo, E., & Courchamp, F. (2007). Multiple Allee effects and population management. Trends in Ecology and Evolution, 22(4): 185-191.
  4. Caddy, J.F., and Agnew, D.J., (2005). An overview of recent global experiences with recovery plans for depleted marine resources and suggested guidelines for recovery planning. Reviews in Fish Biology and Fisheries 14: 43–112.
  5. Canada-Newfoundland and Labrador. (2003). A strategy for the recovery and management of cod stocks in Newfoundland and Labrador. Action Team for Cod Recovery Report, Department of Fisheries and Oceans, Department of Fisheries and Aquaculture, St. John’s, NL, Canada.
  6. Canada-Quebec. (2005). Towards a recovery strategy for Gulf of St. Lawrence cod stocks. Canada-Quebec Cod Action Team Cod Rebuilding Strategy. Department of Fisheries and Oceans, Moncton, Quebec, Canada.
  7. Clark, R.A., Fox, C. J.,Viner, D., Livermore, M. (2003). North Sea cod and climate change – modelling the effects of temperature on population dynamics. Global Change Biology, 9(11): 1669–1680.
  8. Cohen, J., & Barlow, M. (2005). The NAO, the AO, and Global Warming: How Closely Related?. Journal of Climate, 18: 4498-4513.
  9. Colbourne, E., Craig, J., Fitzpatrick, C., Senciall, D., Stead, P., Bailey, W., & Department of Fisheries and Oceans, Ottawa, ON(Canada); Canadian Science Advisory Secretariat, Ottawa, ON(Canada). (2011). An assessment of the physical oceanographic environment on the Newfoundland and Labrador Shelf during 2010 (No. 2011/089). DFO, Ottawa, ON(Canada).
  10. Cox, K. (1994). Why the cold killed the cod. [ Toronto] Globe and Mail, 31 January.
  11. DFO. (2010). Economic overview of the groundfish industry. Economic analysis and statistics, policy sector. Presentation at the Fisheries Resource Conservation Council Meeting. Feb 17–20, 2010, Montreal, Quebec, Canada.
  12. Drinkwater, K. F. (2002). A review of the role of climate variability in the decline of northern cod. Fisheries in a Changing Climate, 113-130.
  13. Drinkwater, K. F. (2005). The response of Atlantic cod (Gadus morhua) to future climate change. ICES Journal of Marine Science: Journal du Conseil, 62(7), 1327-1337.
  14. Drinkwater, K. F. (2006). The regime shift of the 1920s and 1930s in the North Atlantic. Progress in Oceanography, 68(2), 134-151.
  15. Dutil, J.-D., & Brander, K. (2003). Comparing productivity of North Atlantic cod (Gadus morhua) stocks and limits to growth production. Fisheries Oceanography, 12(4/5): 502–512.
  16. Eide, A., Heen, K., Armstrong, C., Flaaten, O., & Vasiliev, A. (2013). Challenges and Successes in the Management of a Shared Fish Stock–The Case of the Russian–Norwegian Barents Sea Cod Fishery. Acta Borealia,30(1), 1-20.
  17. Fromentin,J.-M., & Planque, B. (1996). Calanus and environment in the eastern North Atlantic. II. Influence of the North Atlantic Oscillation on C. finmarchicus and C. helgolandicus. Marine Ecology Progress Series, 134: 111-118.
  18. Greene, C. H., & Pershing, A. J (2000). The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: basin-scale forcing associated with the North Atlantic Oscillation. Journal of Marine Science, 57: 1536–1544.
  19. Greene, C. H., Pershing, A. J., Cronin, T. M., & Ceci, N. (2008). Arctic climate change and its impacts on the ecology of the North Atlantic. Ecology, 89(11): 24-38.
  20. Haedrich, R. L., & Hamilton, L. C. (2000). The fall and future of Newfoundland's cod fishery. Society & Natural Resources, 13(4), 359-372.
  21. Hamilton, L. (2010). Footprints: Demographic effects of outmigration. Migration in the Circumpolar North: Issues and Contexts. L. Husky and C. Southcott (Eds). Edmonton, Alberta: Canadian Circumpolar Institute, 1-14.
  22. Hamilton, L. C., & Butler, M. J. (2001). Outport adaptations: Social indicators through Newfoundland's cod crisis. Human Ecology Review, 8(2), 1-11.
  23. Hátún, H. , Payne, M.R., Beaugrand, G., Reid, P.C., Sandø, A.B., Drange, H., Hansen, B., Jacobsen, J.A, & Bloch, D. (2009). Large bio-geographical shifts in the north-eastern Atlantic Ocean: From the subpolar gyre, via plankton, to blue whiting and pilot whales. Progress in Oceanography, 80: 149–162.
  24. Howard, M. (2003). When fishing grounds are closed: Developing alternative livelihoods for fishing communities. Secretariat for the Pacific Community Women in Fisheries Information Bulletin, 13, 19-22.
  25. Khan, A., & Chuenpagdee, R. (2013). An Interactive Governance and Fish Chain Approach to Fisheries Rebuilding: A Case Study of the Northern Gulf Cod in Eastern Canada. Ambio, 1-14.
  26. Krohn, M., Reidy, S., & Kerr, S. (1997). Bioenergetic analysis of the effects of temperature and prey availability on growth and condition of northern cod (Gadus morhua). Canadian Journal of Fisheries and Aquatic Sciences, 54(1): 113-121.
  27. Lilly, G. R., Nakken, O., & Brattey, J. (2013). A review of the contributions of fisheries and climate variability to contrasting dynamics in two Arcto-boreal Atlantic cod (Gadus morhua) stocks: persistent high productivity in the Barents Sea and collapse on the Newfoundland and Labrador Shelf. Progress in Oceanography.
  28. Mason, F. (2002). The Newfoundland Cod Stock Collapse: A Review and Analysis of Social Factors. Electronic Green Journal, 1(17), Article 2.
  29. McCay, B. J., & Finlayson, A. C., (1995). The political ecology of crisis and institutional change: the case of the northern cod. Annual Meeting of the American Anthropological Association, Washington, DC.
  30. Milich, L. (1999). Resource mismanagement versus sustainable livelihoods: The collapse of the Newfoundland cod fishery. Society & Natural Resources,12(7), 625-642.
  31. Morgan, M. J., DeBlois, E. M., & Rose, G. A. (1997). An observation on the reaction of Atlantic cod (Gadus morhua) in a spawning shoal to bottom trawling. Canadian Journal of Fisheries and Aquatic Sciences, 54(S1), 217-223.
  32. Myers, R. A., Hutchings, J. A., & Barrowman, N. J. (1996). Hypothesis for the decline of cod in the North Atlantic. Marine Ecology Progress Series, 138: 293-308.
  33. Myers, R. A., Hutchings, J. A., & Barrowman, N. J. (1997). Why do Fish Stocks Collapse? The Example of Cod in Atlantic Canada. Ecological Applications, 7(1): 91-106.
  34. Nafo.int. (2013). NAFO Fishery. [online] Available at: http://www.nafo.int/fisheries/frames/tac.html [Accessed: 1 Dec 2013].
  35. Rose, G. A. (2004). Reconciling overfishing and climate change with stock dynamics of Atlantic cod (Gadus morhua) over 500 years. Canadian Journal of Fisheries and Aquatic Sciences, 61, 1553–1557.
  36. Rose, G. A., DeYoung, B., Kulka, D. W., Goddard, S. V., & Fletcher, G. L. (2000). Distribution shifts and overfishing the northern cod (Gadus morhua): a view from the ocean. Canadian Journal of Fisheries and Aquatic Sciences,57(3), 644-663.
  37. Rose,G.A., deYoung, B., Kulka, D.W., Goddard, S.V., & Fletcher G.L. (2000). Distribution shifts and overfishing the northern cod (Gadus morhua): a view from the ocean. Canadian Journal of Fisheries and Aquatic Sciences, 57: 644–663.
  38. Schrank, William E. (2005). The Newfoundland fishery: ten years after the moratorium. Marine Policy 29.5: 407-420.
  39. Song, A.M., Chuenpagdee, R., and Jentoft, S. (2013). Values, images, and principles: What they represent and how they may improve fisheries governance. Marine Policy 40: 167–175.
  40. Sundby, S. (2000). Recruitment of Atlantic cod stocks in relation to temperature and advection of copepod populations. Sarsia, 85: 277-298.
  41. Vilhjalmsson, H. (1983). Biology, abundance estimates and managements of the Icelandic stock of capelin. Rit. Fiskideild. 3: 153-181.
  42. Worm, B., & Myers, R. A. (2003). Meta-analysis of cod-shrimp interactions reveals top-down control in oceanic food webs. Ecology, 84(1), 162-173.

Citation

Roweena Patel, Kate Williman, Viveca Mellegard, Philipp Siegel, Kate Williman, Viveca Mellegard, Philipp Siegel, Reinette (Oonsie) Biggs, Juan Carlos Rocha. Collapse of Newfoundland cod fisheries, Northwest Atlantic. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:18:06 GMT.
Monday, 08 June 2015 19:53

Arctic mobility

Written by Cláudia Florêncio

Arctic mobility

Main Contributors:

Tove Björklund, Cláudia Florêncio, Rawaf al Rawaf, Tove Björklund, Rawaf al Rawaf

Other Contributors:

Juan Carlos Rocha

Summary

Due to anthropogenic climate change and diminishing navigable ice, the Inuit’s mobility and available livelihoods are currently undergoing a regime shift. Inuit communities are increasingly relying on both wage employment and traditional subsistence harvesting, indicating we are probably witnessing the transition between these two livelihood regimes. The main drivers for this transition are anthropogenic climate change and increasing access to store-bought goods through trade and import. The necessity to secure access to food (either traditional or store-bought), and the erosion of traditional knowledge and shifting cultural norms are the key processes impacted by these drivers, as evidenced by the state of human well-being and ecosystem services in Inuit communities today.

Type of regime shift

Ecosystem type

  • Tundra
  • Polar

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • Europe
  • North America
  • Arctic Ocean

Region

  • Arctic Region

Countries

  • Russia
  • Sweden
  • United States
  • Canada
  • Denmark
  • Finland

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. Aporta, C. (2004) Routes, trails and tracks: trail breaking among the Inuit of Igloolik. Etudes/Inuit/Studies 28:9–38.
  2. Dicks, L. Arctic Climate Issues (2011) Changes in Arctic Snow, Water, Ice and Permafrost. Arctic Monitoring and Assessment Programme (AMAP).
  3. Ford, J. (2008) Vulnerability of Inuit food systems to food insecurity as a consequence of climate change: a case study from Igloolik, Nunavut. Regional Environmental Change. Springer.
  4. Ford, J. et al (2010) Climate change policy responses for Canada’s Inuit population: The importance of and opportunities for adaptation. Global Environmental Change 20, issue 1: p.177–191.
  5. Gearheard, S. Matumeak, W. Angutikjuaq, I. Maslanik, J.A. Huntington, H.J.L. Matumeak, D.G.T. Barry, R.G. (2006) It’s not that simple: comparison of sea ice environments, observed changes, and adaptations in Barrow Alaska, USA, and Clyde River, Nunavut, Canada. Ambio 35:203–211. doi:10.1579/0044-7447(2006)35 [203:INTSAC]2.0.CO;2
  6. Hastrup, K. (2009) Arctic hunters: climate variability and social flexibility. Chapter 12 in Hastrup, Kirsten. The Question of Resilience, Social Responses to Climate Change. The Royal Danish Academy of Science and Letters. 362p.
  7. Hastrup, K. (2013) The nomadic landscape: People in a changing Arctic environment. Geografisk Tidsskrift-Danish Journal of Geography, 109:2, 181-189, DOI: 10.1080/00167223.2009.10649606
  8. Hinzman, L.D. et al (2005) Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions. Climatic Change 72: 251–298 DOI: 10.1007/s10584-005-5352-2
  9. Huntington, H. & Fox, S. (2007) ACIA Secretariat and Cooperative Institute for Arctic Research University of Alaska Fairbanks, chapter 3, accessed on 2014-11-25 http://www.acia.uaf.edu/PDFs/ACIA_Science_Chapters_Final/ACIA_Ch03_Final.pdf
  10. ICC (2008) The Sea Ice is Our Highway - An Inuit Perspective on Transportation in the Arctic. A Contribution to the Arctic Marine Shipping Assessment. Inuit Circumpolar Council, Canada.
  11. ICC (2009) Circumpolar Inuit Health Summit. Yellowknife, Canada. Accessed on 2014-11-25 http://www.inuitcircumpolar.com/uploads/3/0/5/4/30542564/2009_healthsummitreport_final.pdf
  12. IPCC (2007) 4th assessment report, Climate change 2007: synthesis report. Accessed on 2014-11-20 http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf
  13. IPCC (2014) 5th assessment report 2013: AR5 Synthesis report. http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_LONGERREPORT.pdf
  14. Kral, M. (2003) Unikkaartuit: meanings of well-being, sadness, suicide, and change in two Inuit communities. Final Report to the National Health Research and Development Programs. Health Canada, Ottawa.
  15. Laidler et al (2009) Travelling and hunting in a changing Arctic: assessing Inuit vulnerability to sea ice change in Igloolik, Nunavut. Climatic Change 94:363–397 DOI 10.1007/s10584-008-9512-z
  16. Nuttall, M. Berkes, F. Forbes, B.C. Kofinas, G. Vlassova, T. & Wenzel, G. (2005) Hunting, Herding, Fishing, and Gathering: Indigenous Peoples and Renewable Resource Use in the Arctic. Pp. 649-690 in: Arctic Climate Impact Assessment. Cambridge, Cambridge University Press.
  17. Sørensen, M. (2010) Inuit landscape use and responses to climate change in the Wollaston Forland—Clavering Ø region, Northeast Greenland. Geografisk Tidsskrift-Danish Journal of Geography 110:155–174.
  18. Takano, T. (2004) Connections with the land: land skills courses in Igloolik, Nunavut. Ethnography 6:463–486.
  19. UNESCO (2009) Climate Change and Arctic Sustainable Development: scientific, social, cultural and educational challenges. UNESCO: Paris, 376 pp.
  20. Willox, A. et al (2013) The land enriches the soul: On climatic and environmental change, affect, and emotional health and well-being in Rigolet, Nunatsiavut, Canada. Emotion, Space and Society 6, 14-24.

Citation

Tove Björklund, Cláudia Florêncio, Rawaf al Rawaf, Tove Björklund, Rawaf al Rawaf , Juan Carlos Rocha. Arctic mobility. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 11:30:32 GMT.
Tuesday, 19 May 2015 19:51

Potential Salmon Collapse

Written by Linnéa Joandi

Potential Salmon Collapse

Main Contributors:

Daniele Crimella, Linnéa Joandi, Hanna Kylin, Kavita Oehme, Hanna Kylin

Other Contributors:

Reinette (Oonsie) Biggs, Jennifer Griffiths, Garry Peterson, Juan Carlos Rocha, Jennifer Griffiths

Summary

The potential regime shift in Alaska occurs in the marine system of the North Pacific Ocean. The present regime is characterised by a high abundance of salmon while a potential regime would be characterised by a low abundance of salmon. This is a speculative shift that has not yet occurred. The key feedbacks that maintains the current regime is the reinforcing loop of salmon population dynamics. Feedback mechanism are also present between the local communities´ needs, fishery regulation, salmon population and hatcheries´ effect. The key drivers that could cause the regime shift include climatic anomalies and extremes, fishing pressure, reduced population heterogeneity, variations in primary production, demand for food, the use of hatcheries, global warming, and changes in salmon population structure. Some possible leverage points for intervention to prevent this regime shift involves management concerned with fisheries, hatcheries and global warming.

Type of regime shift

  • Potential salmon fishery collapse

Ecosystem type

  • Marine & coastal

Land uses

  • Fisheries

Spatial scale of the case study

  • Sub-continental/regional (e.g. southern Africa, Amazon basin)

Continent or Ocean

  • North America
  • Pacific Ocean

Region

  • Alaska, North East Pacific Ocean

Countries

  • United States

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

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Citation

Daniele Crimella, Linnéa Joandi, Hanna Kylin, Kavita Oehme, Hanna Kylin, Reinette (Oonsie) Biggs, Jennifer Griffiths, Garry Peterson, Juan Carlos Rocha, Jennifer Griffiths. Potential Salmon Collapse. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:43:18 GMT.
Saturday, 25 January 2014 17:29

Tokaj wine region socialization

Written by Béla Kuslits

Tokaj wine region socialization

Main Contributors:

Béla Kuslits

Other Contributors:

Reinette (Oonsie) Biggs, Juan Carlos Rocha

Summary

Tokaj-Hegyalja, a wine region in north-eastern Hungary has undergone a regime shift from small-scale and high-quality wine producing strategy to a low-quality industrialized strategy. For centuries before the regime shift, mostly local families and wealthy individuals owned and operated the vineyards. The high-quality regime was maintained by the high number of wineries, the high level of local ecological knowledge and the access to the European markets where the wines were sold for good prices. After the Second World War Hungary remained under the Soviet influence, and a socialist, authoritarian regime started to govern the country. The vineyards and wineries in the Tokaj region were socialized and became parts of a large, state-operated winemaking company following a highly quantity-oriented strategy in wine-production and selling the wines in the socialist (Comcon) countries. First, the industrialized regime was forced by an external power, but later, the regime became stable as the number of wineries decreased, the local knowledge wasn't used any more and the vineyards were transformed to produce large quantities. Many high-quality but low productivity vineyards have been abandoned and became high biodiversity areas (mostly forests). Even after the political changes in 1989 the stable state remained intact as the most important factors sustaining the high-quality regime were lacking. This regime is maintained by a high demand for cheap wine, state subsidies and the missing contacts to the quality sensitive markets. Today, as the former Soviet market collapsed, the region is facing a poverty trap. As Hungary joined the European Union in 2004, the abandoned vineyards became Natura 2000 conservation areas, thus it is difficult to use them for agriculture. However, after the political changes in 1989 the state owned vineyards were privatized and there are more and more private wineries producing high-quality wines. Some of them have gained access to quality sensitive markets and started to operate in a new quality-oriented regime. It's however uncertain whether the region will flip back in the near future to a quality-oriented scheme or if it will remain a marginal strategy.

Type of regime shift

  • Governance change

Ecosystem type

  • Agro-ecosystems

Land uses

  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Conservation

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Europe

Region

  • North-eastern Hungary, Tokaj-Hegyalja World Heritage Region

Countries

  • Hungary

Locate with Google Map

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Fisheries

Impacts

Ecosystem type

  • Marine & coastal
  • Polar

Key Ecosystem Processes

  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Fisheries
  • Wild animal and plant products

Regulating services

  • Climate regulation
  • Natural hazard regulation

Cultural services

  • Recreation
  • Aesthetic values
  • Knowledge and educational values

Human Well-being

  • Food and nutrition
  • Health (eg toxins, disease)
  • Livelihoods and economic activity
  • Cultural, aesthetic and recreational values

Key Attributes

Spatial scale of RS

  • Sub-continental/regional

Time scale of RS

  • Unknown

Reversibility

  • Irreversible (on 100 year time scale)

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Contested – Reasonable evidence both for and against the existence of RS

Confidence: Mechanism underlying RS

  • Contested – Multiple proposed mechanisms, reasonable evidence both for and against different mechanisms

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Alternate regimes

Anthropogenic climate change is largely responsible for the observed changes in the Arctic Ocean over the last few decades (Dicks et al. 2011). The Arctic thermal, hydrological, climatological and biological changes are highly interconnected and the system dynamics are poorly understood insulated from each other (Hinzman et al. 2005). Precisely how the changes in the biological conditions will affect the food web system in the Arctic Ocean is unknown; however, it is evident that people depending on Arctic fish for their livelihoods will be effected in the short term (ibid), while in the longer term, changes might profoundly affect commercial fish stocks in the lower latitudes (Hassan et al. 2005).

Polar regime

The polar regime is characterized by long winters of 7-10 months (Hinzman et al. 2005). The large extent of year-round sea ice reinforce the albedo effect exhibited at these latitudes, keeping the system in a state of low primary productivity. The ice melt in summer allows phytoplankton to reproduce and provide energy for the dominant cold-loving zooplankton species Calanus hyperboreus and C. glacialis (Ardyna et al. 2014).

Temperate regime

Summer air temperatures over the Arctic have continued to increase since 1800 (Dicks et al. 2011). The associated decline in sea ice extent and thickness has allowed light to penetrate the upper water column, while the exposure of year-round sea water has increased storminess and the upwelling of nutrients. In some cases, this has led to two annual bloom events and an extent of single annual blooms in areas previously characterized by flat patterns at the sea-ice boundary (Ardyna et al. 2014).

Drivers and causes of the regime shift

Global warming is well documented as the main driver of warmer air temperatures over the Arctic (Dicks et al. 2011). Warming is causing sea ice to melt and is extending the amount of year-round and seasonal open water (Ardyna et al. 2014). This darker surface is reducing albedo reflexivity and increasing sea surface temperatures (SST). The IPCC AR5 states that warming must be kept below 1°C to prevent irreversible changes of the Arctic system.

Natural variations in Arctic SST are observed through Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) internal forcing mechanisms, both modes of climate variability that originate in the lower latitudes. The latter enhances westerly winds, while the combination of both the NAO and a positive AMO enhance ocean advection and storm events (Schlesinger & Ramankutty 1994). This phase of activity has been observed since the mid-1990s, enhancing the poleward movement of warm, saline waters to the eastern Arctic (Chylek et al. 2009).

The amount of water masses entering into the Arctic is highly influenced by the strength of Subpolar gyre (Hátún et al. 2009), which itself is influenced by the AMO mode. Since 1995, the North Atlantic Subpolar gyre has been weakening (Häkkinen & Rhines 2004). Together, the AMO and Subpolar gyre have enhanced the observed melting of sea ice in the Arctic and the calving events of the Greenland Ice Sheet (GIS) (Straneo & Heinback 2009). However, freshwater inflow from Greenland and Siberian runoff reduces the density of the water column and enhances stratification with the denser saline layer below. It is uncertain how this inflow might counter the observed increase in bloom events, but a change in Siberian forest cover could enhance nutrient inputs and thus promote further PP, where rates of PP have already increased by 135% from 1998 to 2009 (Frey et al. 2007).

How the regime shift worked

The polar region is characterized by relatively low rates of precipitation and two distinct seasons (Hinzman et al. 2005). The winter season, lasting for 7-10 months, displays a large sea-ice extent, maintained through an ice-albedo feedback (Curry et al. 1995). During the summer, the sea ice retreats and allows for PP to occur in areas where light can penetrate the water column (Ardyna et al. 2014). These conditions are especially beneficial for the cold-loving zooplankton species Calanus hyperboreus and C. glacialis. They successfully convert phytoplankton into energy-dense marine lipid, and thus play a vital role in sustaining the higher trophic levels of the Arctic ecosystem (Falk-Petersen et al. 2007). In September the annual freeze-up begins.

The ocean and atmosphere work together to drive currents around the planet. At the interface, this heat flux causes the development of trade winds and storm events. This interaction is amplified as the sea ice melts and - coupled with warmer air temperatures - it increases storminess and vertical mixing in the upper layers of the water column. Such turbulence brings nutrients and heavier phytoplankton to the surface, promoting suitable conditions for PP. This coupling has intensified with more ice-free waters in the summer months and led to an upward trend in the length of the growing season (Frey et al. 2007). Since 1995, the positive modes of variation along with a weak Subpolar gyre and strong density-driven Thermohaline conveyor (THC), have favoured the poleward movement of warmer waters (Hátún et al. 2009), bringing warm-water-loving species (eg. herring) north and contracting the range of cold-water-loving species, such as the zooplankton C. finimarchicus, northwards. These mechanisms are amplifying the effect of anthropogenic forcing in the Arctic Ocean but it is unsure how they, in turn, will be affected by climate change in the future (Hátún et al. 2005).

The temperate regime is characterised by two annual phytoplankton bloom events. The Arctic Ocean is the least productive of all the oceans, but as permanent ice cover and stratification has declined, primary productivity has increased (Ardyna et al. 2014). A delay in the annual freeze-up event due to warmer SST has lengthened the growing season. Phenological changes in the timing of blooms, advancing by as much as 50 days between 1997 to 2009, has allowed for double bloom events characteristic of more temperate climates and a compositional shift towards the dominance of smaller phytoplankton species (Li et al. 2009). Earlier melting is increasing nutrient-rich freshwater inputs from coastal shelves, such as Siberia and Greenland, while oceanic systems are driving nutrient-rich waters from the lower latitudes (Ardyna et al. 2014). Together, these processes act to maintain the Arctic in a temperate state.

Impacts on ecosystem services and human well-being

Shift from polar regime to temperate regime

Ice-dependent species with limited distribution, specialised feeding habits and predator avoidance (Post et al. 2009), such as cod, shrimp, marine mammals and seabirds, have seen changes in abundance due to warmer temperatures and changes in their ecosystems (Wasmann 2011). In contrast, warm-loving species are thriving due to rising SST and food abundance (Hátún et al. 2009). Nevertheless, in the long term a shift in food-web composition and diversity could diminish the resilience of the Arctic system by the invasion of non-native species, eutrophication or the spread of disease thus decreasing the recreational and aesthetic value of these ecosystems (Niiranen et al. 2014).


Due to their highly adapted way of life, the loss of provisioning ES could indirectly impact indigenous wellbeing and livelihoods (Arctic Council 2013). Contrarily, this shift to a temperate regime could bring shorter-term gains to tourism (eg. whale watching) and commercial fishing, helped by easier navigation in ice-free waters, although the benefit will be felt by mainly non-Arctic residents (Hassan et al. 2005). Human health is at risk due to the consumption of high level fish and mammal from the Arctic by the bioaccumulation of pollutants (Butler and Oluoch-Kosura 2006). Changes in the Arctic will also have spillover effects in Atlantic waters, reducing PP and food provisioning (Arctic Council 2013).

Management options

From the point of view of PP, it is unclear how the regime shift would affect the ecosystem and the services people derive from it (Moore & Huntington 2008; Greene et al. 2008; Li et al. 2011). However, the regime shift is connected to other changes with possibly catastrophic implications, such as reduced Albedo negatively influencing the Arctic Ocean’s temperature regulating ability, or the loss of habitat for Arctic-specific species. Considering these implications of a regime shift, from a global perspective polar conditions are clearly preferable.

It is essential to cut global emissions of greenhouse gases (GHG) in order to prevent further sea ice loss and the kicking-in of feedback mechanisms that risk putting the Arctic in a permanent temperate state. Equally important is to prevent deforestation, as this reduces the biosphere’s ability to sequester atmospheric carbon. Especially important, in the polar region, ceased deforestation could reduce primary production by decreasing the discharge of nutrients into the Arctic Ocean. For carrying this out, international agreements on emissions and land use are necessary. However, it might not be enough to prevent a regime shift considering observed changes and the time lag of global climate processes. Management options for reversing the regime shift are essentially the same as for preventing it, but a reversal is likely to take a long time, as several feedback mechanisms will drive the system towards temperate conditions.

Although highly criticised, geoengineering has been proposed as a way to speed up the reversal of the regime shift (Heckendorn et al. 2009). A scheme often put forward is to reflect some solar radiation back into space by introducing aerosols into the stratosphere. Though economically viable, this is highly controversial due to its ethically challenging nature, the many possible ecological side effects and the impossibility to reverse action once implemented.

Key References

  1. EEA. (2013). Natura 2000 data - the European network of protected sites. 03.09.2013. Retrieved from http://www.eea.europa.eu/data-and-maps/data/natura-4
  2. Hegedűs, S. (1908). Kimutatás a Tokaji borvidékhez tartozó községek szőlőterületéről és borterméséről az 1900-1907 években. In Királyok Boráról Borok Királyáról Tokaji Nektárról Folyékony Aranyról. Tokaj: Frankel Dezső Villanyerőre Berendezett Könyvnyomdája.
  3. ICOMOS. (2002). Tokaji Wine Region (Hungary).
  4. Nyizsalovszki, R., & Virók, V. (2001). Területhasználat időbeli változásai és következményei egy tokaj-hegyaljai településen. In Földrajzi Konferencia. Szeged.
  5. UNESCO. (2002). Decisions Adopted by the 26th Session of the World Heritage Committee.

Citation

Béla Kuslits, Reinette (Oonsie) Biggs, Juan Carlos Rocha. Tokaj wine region socialization. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 12:46:05 GMT.
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