Global Warming Effects Around the World

South Orkney Islands, Antarctica

Top Impact

Ecosystems (Salt water)

Other Impacts

Oceans (Sea ice)

Temperature (Air)

Adélie penguins living on Signy Island

Climate change is one factor curbing the abundance of krill—the primary food source for Adélie penguins living on Signy Island. As their food supply has declined, so has the number of breeding penguin pairs on the island. Future warming and reductions in sea ice could prevent Adélies from successfully breeding here.1

Key Facts

Signy Island is an important breeding ground for the large penguin populations of the South Orkney Islands archipelago.7 Rapidly warming temperatures,2 an associated decrease in sea ice,4 and shifts in the abundance of predator species are causing declines in krill, the small, shrimplike crustacean that now constitutes the bulk of the diet for Adélie and chinstrap penguins.10 Continued reductions in sea ice may threaten the penguins' ability to thrive in the South Orkney Islands.7

  • The Orcadas research station near Signy Island has recorded a warming in the average surface air temperature of about 3.6° F (2° C) since 19042—more than double the average warming the Earth has experienced during the last century.8
  • In response to rising temperatures, declining sea ice, and other factors, krill density in the South Orkney Islands region has declined by up to 50 percent since 1976.10
  • From 1987 to 2004, the number of breeding Adélie and chinstrap penguins declined by or over 47 percent and around 22 percent, respectively.7

Details

The South Orkney Islands, located within the Scotia Sea, are home to some of the northernmost colonies of Adélie penguins, as well as significant numbers of chinstrap penguins. Among other factors, rising temperatures2,3and reductions in regional sea ice4 lead to declines in the abundance of krill, the small, shrimplike crustaceans that constitute the bulk of Adélie and chinstrap diets.5

Adélie and chinstrap penguins have very different relationships with sea ice.6 Adélie penguins are an ice–loving species that prefers habitats with extensive sea ice.6,7 In contrast, chinstrap penguins avoid the ice, and are relatively unaffected by its extent.6,7 Because they are less dependent on sea ice, chinstrap penguins were long considered potential beneficiaries of rising temperatures.6 Recent studies have found, however, that numbers of both penguin species are declining throughout the Antarctic Peninsula and nearby islands.6,7

The average air temperature in the Scotia Sea region has been rising rapidly over the last century. The Orcadas research station near Signy Island has recorded a warming of about 3.6° F (2° C) since 1904—more than double the global average warming during the last century.2,8

Because temperatures have been rising, the extent and duration of sea ice in the Scotia Sea have been declining.3,6,9 A 92–year record of fast ice—sea ice that has frozen along the coast and "fastened" to the land—from Signy Island shows a long–term decline since 1903.4

Despite their different relationships to sea ice, variations in the abundance of both Adélies and chinstraps are closely related to sea ice extent, with low breeding populations coinciding with minimal sea ice occurring the same or previous year.7 The similarity in their responses reflects the fact that both penguin species depend primarily on krill as their food source.

Reductions in winter and spring sea ice curb the reproductive success of krill, decreasing the krill biomass available for penguins to eat.10 In response to rising temperatures and declining sea ice, krill density in the South Orkney Islands region has been reduced by up to half since 1976.10

The response of penguins to the declining krill supply is clear. From 1987 to 2004, the number of breeding Adélie and chinstrap penguins fell annually by 2.8 percent and 1.3 percent, respectively or over 47 percent and around 22 percent respectively for the entire study period.7

In addition to seeing population declines stemming from changes in climate, krill have been increasingly harvested for human consumption. Krill catches in the South Orkney Islands region have recently increased 10-fold—from 5,479 tons (4,981 tonnes) in the 2000–2001 season to 54,999 tons (49,999 tonnes) in the 2009–2010 season.11

Penguins have been relying on krill as their primary food source only for the past 200 years.12 Starting in the late 1700s, extensive hunting of Antarctic fur seals and whales reduced the number of marine predators feeding on krill, causing a surplus of krill. At that time, penguins began to rely less on fish and more on krill for food.12 As the populations of fur seals and whales recover from a long period of overexploitation, these marine mammals are consuming more krill, leaving less available for penguins.10

Part of a Larger Pattern

The South Orkney Islands lie within the same region as the Antarctic Peninsula—one of the most rapidly warming places in the world.9 The average air temperature on the Antarctic Peninsula has warmed by 1° F (0.56° C) per decade for the last 50 years, for a total warming of about 5° F (2.8° C) since the 1950s.3,13 The per–decade pace of warming in the Antarctic Peninsula is around four times higher than the global average. Globally, the Earth has experienced a warming of 0.23° F (0.13° C) per decade over the past 50 years.8

The rapid warming of the Antarctic Peninsula and its surroundings may be due to a regional amplification of global trends, but exactly how this occurs is not well understood.9 Scientists have suggested that declining sea ice extent and rising air temperatures may be feeding back on each other, initiating even more warming and ice melt.9

What the Future Holds

Given a mid–range scenario14 for future emissions of heat–trapping gases—primarily from the burning of oil, coal, gas, and trees—the South Orkney Islands are projected to warm by 2.7 to 3.6° F (1.5 to 2.0° C) by the end of this century.15 In response, Antarctic sea ice extent is projected to decrease by about 25 percent, and winter sea ice thickness in the vicinity of the South Orkney Islands to decrease by about 30 percent.16

The South Orkney Islands are already at the northern limit of the Adélie penguin's range.7 The projected declines in sea ice could prevent these penguins from completing their breeding cycle, as historically their breeding success has been tied to fluctuations in local sea ice extent.7

Chinstrap penguins are better adapted to ice–free conditions, so sea ice declines will not affect their needed physical habitat as much.7 Because reductions in sea ice are correlated with reductions in food supply, however, climate change is likely to harm both species.6,7 Taking swift action to reduce heat–trapping emissions could lessen the impact of future climate change on penguin populations.

Credits

Endnotes

  1. Photograph used with permission from Liam Quinn. Online at: http://www.flickr.com/photos/liamq/5917160673/in/gallery-49535267@N06-72157627484385909/. Accessed April 16th, 2012.
  2. Meredith, M.P., and J.C. King. 2005. Rapid climate change in the ocean west of the Antarctic Peninsula during the second half of the 20th century. Geophysical Research Letters 32:L19604.
  3. Licuanan, W.Y., and E.D. Gomez. 2000. Philippine coral reefs, reef fishes, and associated fisheries: Status and recommendations to improve their management. In: Status of coral reefs of the world: 2000. Edited by C. Wilkinson. Townsville, Queensland: Australian Institute of Marine Science.
  4. Murphy, E.J., A. Clarke, C. Symon, and J. Priddle. 1995. Temporal variation in Antarctic sea–ice: Analysis of a long term fast–ice record from the South Orkney Islands. Deep–Sea Research I 42(7):1045–1062.
  5. Hinke, J.T., K. Salwicka, S.G. Trivelpiece, G.M. Watters, and W.Z. Trivelpiece. 2007. Divergent responses of Pygoscelis penguins reveal a common environmental driver. Oecologia doi:10.1007/s00442–007-0781–4.
  6. Trivelpiece, W.Z., J.T. Hinke, A.K. Miller, C.S. Reiss, S.G. Trivelpiece, and G.M. Watters. 2011. Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica. Proceedings of the National Academy of Sciences of the United States of America 108(18):7625–7628.
  7. Forcada, J., P.N. Trathan, K. Reid, E.J. Murphy, and J.P. Croxall. 2006. Contrasting population changes in sympatric penguin species in association with climate warming. Global Change Biology 12:411–423.
  8. Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A. Klein Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden, and P. Zhai. 2007. Observations: Surface and atmospheric climate change. In: Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller. Cambridge, UK, and New York, NY: Cambridge University Press.
  9. Vaughan, D.G., G.J. Marshall, W.M. Connolley, C. Parkinson, R. Mulvaney, D.A. Hodgson, J.C. King, C.J. Pudsey, and J. Turner. 2003. Recent rapid regional climate warming on the Antarctic Peninsula. Climatic Change 60:243–274.
  10. Atkinson, A., V. Sielgel, E. Pakhomov, and P. Rothery. 2004. Long–term decline in krill stock and increase in salps within the Southern Ocean. Nature 432:100–103.
  11. Commission for the Conservation of Antarctic Marine Living Resources. 2011. Statistical Bulletin 23. Tasmania, Australia.
  12. Emslie, S.D., and W.P. Patterson. 2007. Abrupt recent shift in d13C and d15N values in Adélie penguin eggshell in Antarctica. Proceedings of the National Academy of Sciences of the United States of America 104(28):11,666–11,669.
  13. Turner, J., S.R. Colwell, G.J. Marshall, T.A. Lachlan–Cope, A.M. Carleton, P.D. Jones, V. Lagun, P.A. Reid, and S. Iaogovkina. 2005. Antarctic climate change during the last 50 years. International Journal of Climatology 25:279–294.
  14. The scenario referred to here is the middle–emissions pathway known as A1B from the Intergovernmental Panel on Climate Change.
  15. Christensen, J.H., B. Hewitson, A. Busuioc, A. Chen, X. Gao, I. Held, R. Jones, R.K. Kolli, W.–T. Kwon, R. Laprise, V. Magaña Rueda, L. Mearns, C.G. Menéndez, J. Räisänen, A. Rinke, A. Sarr, and P. Whetton. 2007. Regional climate projections. In: Climate change 2007: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller. Cambridge, UK, and New York, NY: Cambridge University Press.
  16. Arzel, O., T. Fichefet, and H. Goosse. 2006. Sea ice evolution over the 20th and 21st centuries as simulated by current AOGCMs. Ocean Modelling 12:401–415.
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