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Very substantial decrease in Arctic Sea ice in 2007 from 2005 and also from 1979-2000 average

Arctic shrinkage is the decrease in size of the Arctic region (as defined by the 10 °C (50 °F) July isotherm). This is a change in the regional climate as a result of global warming. Projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2060 and 2080.[1] Because of the rapid response of the Arctic to global warming, it is often seen as a high-sensitivity indicator of climate change. Scientists also point to the potential for release of methane from the Arctic region, especially through the thawing of permafrost and methane clathrates.

Contents

Modelling, history, and predictions

Computer models predict that the sea ice area will continue to shrink in the future, although recent work has called into question their ability to accurately predict sea ice changes.[2] Current climate models frequently underestimate the rate of shrinkage.[3] In 2007 the IPCC reported that “the projected reduction [in global sea ice cover] is accelerated in the Arctic, where some models project summer sea ice cover to disappear entirely in the high-emission A2 scenario in the latter part of the 21st century.″ [4] There is currently no scientific evidence that a seasonally ice-free Arctic Ocean existed anytime in the last 700,000 years, although there were periods when the Arctic was warmer than it is today.[5][6] Scientists are studying possible causal factors such as direct changes resulting from the greenhouse effect as well as indirect changes such as unusual wind patterns, rising Arctic temperatures,[7] or shifting water circulation[8] (such as increasing inflows of warm, fresh water to the Arctic Ocean from rivers.)

According to the Intergovernmental Panel on Climate Change, "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world."[9] Reduction of the area of Arctic sea ice means less solar energy is reflected back into space, thus accelerating the reduction.[10] Studies have shown that recent warming in the polar regions was due to the net effect human influence through greenhouse gases and ozone depletion, which has a cooling effect opposed to the influence of greenhouse gases.[11]

1870-2000 Northern hemisphere sea ice extent in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in Autumn up to 1940 reflects lack of data rather than a real lack of variation.

Reliable measurement of sea ice edge begin within the satellite era in the late 1970s. Before this the region was less well monitored by a combination of ships, buoys and aircraft [12] On top of the long-term negative trend in recent years, attributed to global warming, there is considerable interannual variation [13]. Some of this variation may be related to effects such as the arctic oscillation, which may itself be related to global warming [14]; some of the variation is essentially random "weather noise".

The Arctic sea ice September minimum extent reached new record lows in 2002, 2005, and 2007 (39.2 percent below below the 1979-2000 average). In 2007, Arctic sea ice broke all previous records by early August—a month before the end of melt season, with the biggest decline ever in Arctic sea ice minimum extent, more than a million square kilometers.[15] In the first time in human memory, the fabled Northwest Passage opened completely.[16] The dramatic 2007 melting surprised and concerned scientists.[17][18 ]

In 2008 and 2009, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.[19] Additionally, studies show a dramatic decline in ice age and thickness.[20] The Catlin Arctic Survey reported an average thickness of 1.8 meters across the northern Beaufort Sea, an area that had traditionally contained older, thicker ice.[21]

Effects

Earlier retreat of sea ice in Barrow, Alaska

The effects of Arctic shrinkage include a marked decrease in Arctic sea ice; melting permafrost, leading to the release of methane, a potent greenhouse gas[22]; the release of methane from clathrates, leading to longer time-scale methane release;[23] the observed increase in melt on the Greenland Ice Sheet in recent years; and potential changes in patterns of ocean circulation. Scientists worry that some of these effects may cause positive feedbacks which could accelerate the rate of global warming.

Sea ice

The sea ice in the Arctic region is in itself important in maintaining global climate due to its albedo (reflectivity).[24] Melting of this sea ice will therefore exacerbate global warming due to positive feedback effects, where warming creates more warming by increased solar absorption.[24][25] An important feedback in the Arctic currently is ice-albedo feedback. The loss of the Arctic sea ice may represent a tipping point in global warming, when 'runaway' climate change starts.[26][27] This would be due to the release of methane from permafrost and clathrates in the region, and also because of ice-albedo feedback effects. However, recent research has challenged the notion of ice-albedo feedback causing an imminent Arctic sea ice tipping point.[28][29]

Projected change in polar bear habitat from 2001–2010 to 2041–2050

April 3, 2007, the National Wildlife Federation urged the U.S. Congress to place polar bears under the Endangered Species Act.[30] Four months later, the United States Geological Survey completed a year-long study[31] which concluded in part that the floating Arctic sea ice will continue its rapid shrinkage over the next 50 years, consequently wiping out much of the polar bear habitat. The bears would disappear from Alaska, but would continue to exist in the Canadian Arctic Archipelago and areas off the northern Greenland coast.[32] Secondary ecological effects are also resultant from the shrinkage of sea ice; for example, Polar Bears are denied their historic length of seal hunting season due to late formation and early thaw of pack ice.

Loss of permafrost

Sea ice loss has melting effects on permafrost[33], both in the sea[34], and on land[35] and consequential effects on methane release, and wildlife.[36] Some studies imply a direct link, as they predict cold air passing over ice is replaced by warm air passing over the sea. This warm air carries heat to the permafrost around the Arctic, and melts it.[35] This thawing of the permafrost might accelerate methane release from areas like Siberia.[37]

Clathrate gun

Sea ice serves to stabilise methane deposits on and near the shoreline,[38] preventing the clathrate breaking down and outgassing methane into the atmosphere. Any methane released to the atmosphere will then causing further warming.

Melting of the Greenland Ice Sheet

Models predict a sea-level contribution of about 5 centimetres (2 in) from melting in Greenland during the 21st century.[39] It is also predicted that Greenland will become warm enough by 2100 to begin an almost complete melt during the next 1,000 years or more.[40][41]

Effect on ocean circulation

Although this is now thought unlikely in the near future, it has also been suggested that there could be a shutdown of thermohaline circulation, similar to that which is believed to have driven the Younger Dryas, an abrupt climate change event. There is also potentially a possibility of a more general disruption of ocean circulation, which may lead to an ocean anoxic event, although these are believed to be much more common in the distant past. It is unclear whether the appropriate pre-conditions for such an event exist today.

Control of Arctic shrinkage

Geoengineering

Geoengineering approaches offer interventions which may increase Arctic ice, or reduce its decline.[42] These operate either by regional effects (Arctic geoengineering) or global effects (geoengineering). Several specific Arctic geoengineering schemes have been proposed to reduce Arctic shrinkage. Further, scientists such as Paul Crutzen have argued for general geoengineering proposals such as using stratospheric sulfur aerosols to be used, which will affect the Arctic if deployed in or near this region.

According to John Holdren, Assistant to the President of the United States for Science and Technology, complete loss of summer sea ice in the Arctic would be a milestone that could justify geoengineering in order to purposely cool the climate. Holdren believes that complete loss of summer sea ice in the Arctic could signal an increased chance of "really intolerable consequences."[43]

Research

National

Individual countries within the Arctic zone, Canada, Denmark (Greenland), Finland, Iceland, Norway, Russia, Sweden, and the United States (Alaska) conduct independent research through a variety of organizations and agencies, public and private, such as Russia's Arctic and Antarctic Research Institute. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the Chinese Arctic and Antarctic Agency.

International

International cooperative research between nations has become increasingly important:

Territorial claims

Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' Arctic territorial claims in hopes of establishing resource development and new shipping lanes, in addition to protecting sovereign rights.[47]

Danish Foreign Minister Per Stig Møller and Greenland's Premier Hans Enoksen invited foreign ministers from Canada, Norway, Russia and the United States to Ilulissat, Greenland for a summit in May 2008 to discuss how to divide borders in the changing Arctic region, and a discussion on more cooperation against climate change affecting the Arctic.[48] At the Arctic Ocean Conference, Foreign Ministers and other officials representing the five countries announced the Ilulissat Declaration on May 28, 2008.[49][50]

See also

References

  1. ^ Bo, J.; Hall, A.; Qu, X. (2009). "September sea-ice cover in the Arctic Ocean projected to vanish by 2100". Nature Geoscience 2: 341. doi:10.1038/ngeo467.   edit
  2. ^ Eisenman, Ian; Untersteiner, Norbert; Wettlaufer, J.S. (2007). "On the reliability of simulated Arctic sea ice in Global Climate Models". Geophysical Research Letters 34: L10501. doi:10.1029/2007GL029914. http://pantheon.yale.edu/%7Ejw378/articles/EUW_revised_2007.pdf.  
  3. ^ Stroeve, J.; Holland, M. M.; Meier, W.; Scambos, T.; Serreze, M. (2007). "Arctic sea ice decline: Faster than forecast". Geophysical Research Letters 34: L09501. doi:10.1029/2007GL029703.   edit
  4. ^ Meehl, G.A., and others; Intergovernmental Panel on Climate Change Working Group I. (2007). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10. New York: Cambridge University Press. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf.  
  5. ^ Overpeck, Jonathan T. (2005-08-23). "Arctic System on Trajectory to New, Seasonally Ice-Free State" (pdf). Eos, Transactions, American Geophysical Union 86 (34): 309–316. http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf. Retrieved 2007-12-24.  
  6. ^ Butt, F. A.; H. Drange, A. Elverhoi, O. H. Ottera & A. Solheim (2002). The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings. 21. Quaternary Science Reviews. pp. 1643–1660. OCLC 108566094. http://www.nersc.no/~oddho/Thesis/chapter3.pdf.  
  7. ^ Black, Richard (2006-09-14). "'Drastic' shrinkage in Arctic ice". Science/Nature (BBC News). http://news.bbc.co.uk/2/hi/science/nature/5344208.stm. Retrieved 2007-09-16.  
  8. ^ "Study: Circulation Shift May Be Melting Arctic Sea Ice". Fox News. 2007-11-24. http://www.foxnews.com/story/0,2933,311753,00.html. Retrieved 2007-11-27.  
  9. ^ McCarthy, James J.; Intergovernmental Panel on Climate Change Working Group II. (2001). Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press. ISBN 0521807689. http://www.grida.no/climate/ipcc_tar/wg2/597.htm#16131. Retrieved 2007-12-24.  
  10. ^ Black, Richard (2007-05-18). "Earth - melting in the heat?". BBC News. http://news.bbc.co.uk/2/hi/science/nature/4315968.stm. Retrieved 2008-01-03.  
  11. ^ Gillett, Nathan P.; Stone, Dáithí A.; Stott, Peter A.; Nozawa, Toru; Karpechko, Alexey Yu.; Hegerl, Gabriele C.; Wehner, Michael F.; Jones, Philip D. (2008-10-30). "Attribution of polar warming to human influence". Nature Geoscience (Nature Publishing Group) 1: 750. doi:10.1038/ngeo338. http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo338.html. Retrieved 2008-11-01.  
  12. ^ W.N., J.C. Stroeve, and F. Fetterer. 2006. Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record. Annals of Glaciology 46: 428-434.
  13. ^ http://www.jpl.nasa.gov/news/news.cfm?release=2007-131
  14. ^ Fyfe, J.C; G.J. Boer and G.M. Flato (June 1, 1999). "The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming". Geophysical Research Letters 26 (11): 1601–4. doi:10.1029/1999GL900317.  
  15. ^ NSIDC "State of the Cryosphere, Is the Cryosphere sending signals about climate change?"
  16. ^ http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html NSIDC 1 October 2007 "Arctic Sea Ice Shatters All Previous Record Lows - Diminished summer sea ice leads to opening of the fabled Northwest Passage"
  17. ^ NASA "Remarkable' Drop in Arctic Sea Ice Raises Questions"
  18. ^ .NASA Earth Observatory - Monitoring Sea Ice
  19. ^ NSIDC"Arctic sea ice extent remains low; 2009 sees third-lowest mark"
  20. ^ NSIDC 6 October 2009
  21. ^ Catlin Arctic Survey "SURVEY DATA SUPPORTS RAPID ICE LOSS - LARGELY OPEN ARCTIC SEAS IN SUMMER WITHIN TEN YEARS"
  22. ^ Christensen, T. R.; Johansson, T. öR.; Jonas Åkerman, H.; Mastepanov, M.; Malmer, N.; Friborg, T.; Crill, P.; Svensson, B. H. (2004). "Thawing sub-arctic permafrost: Effects on vegetation and methane emissions". Geophysical Research Letters 31: L04501. doi:10.1029/2003GL018680.   edit
  23. ^ Macdonald, G. J. (1990). "Role of methane clathrates in past and future climates". Climatic Change 16: 247–243. doi:10.1007/BF00144504.   edit
  24. ^ a b "All About Sea Ice". NSIDC. http://www.nsidc.org/seaice/intro.html. Retrieved 2009-01-10.  
  25. ^ "Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea". United Nations Environment Programme. p. 75–76. http://www.unep.org/geo/geo_ice/PDF/GEO_C5_LowRes.pdf.  
  26. ^ Lawrence, D. M.; Slater, A. (2005). "A projection of severe near-surface permafrost degradation during the 21st century". Geophysical Research Letters 32: L24401. doi:10.1029/2005GL025080.   edit
  27. ^ Archer, D.; Bufett, B. (2005). "Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing". Geochemistry Geophysics Geosystems 6: Q03002. doi:10.1029/2004GC000854. http://geosci.uchicago.edu/~archer/reprints/archer.2005.clathrates.pdf.   edit
  28. ^ http://environmentalresearchweb.org/cws/article/research/37591
  29. ^ Eisenman, Ian; Wettlaufer, J.S. (2009). "Nonlinear threshold behavior during the loss of Arctic sea ice". Proceedings of the National Academy of Sciences of the United States of America 106 (1): 28–32. doi:10.1073/pnas.0806887106. http://pantheon.yale.edu/%7Ejw378/articles/E&W_Bif_PNAS.pdf.  
  30. ^ "Protection For Polar Bears Urged By National Wildlife Federation". Science Daily. 2008-04-03. http://www.sciencedaily.com/releases/2008/04/080402210456.htm. Retrieved 2008-04-03.  
  31. ^ DeWeaver, Eric (2007). "Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears" (pdf). United States Department of the Interior. http://www.usgs.gov/newsroom/special/polar_bears/docs/USGS_PolarBear_DeWeaver_GCM-Uncertainty.pdf.  
  32. ^ Broder, John; Revkin, Andrew C. (2007-07-08). "Warming Is Seen as Wiping Out Most Polar Bears". The New York Times. http://www.nytimes.com/2007/09/08/science/earth/08polar.html?_r=1&hp=&adxnnl=1&oref=slogin&adxnnlx=1190574637-aS0VOr2klykTSNwK91tiDg. Retrieved 2007-09-23.  
  33. ^ http://www.cgd.ucar.edu/ccr/dlawren/publications/lawrence.grl.submit.2008.pdf
  34. ^ http://e360.yale.edu/content/feature.msp?id=2081
  35. ^ a b http://www.ucar.edu/news/releases/2008/permafrost.jsp
  36. ^ "Permafrost Threatened by Rapid Retreat of Arctic Sea Ice, NCAR Study Finds". University Corporation for Atmospheric Research. 2008-06-10. http://www.ucar.edu/news/releases/2008/permafrost.jsp.. Retrieved 2008-06-11.  
  37. ^ http://news.nationalgeographic.com/news/2008/12/081219-methane-siberia.html
  38. ^ Shakhova, N.; Semiletov, I.; Panteleev, G. (2005). "The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle". Geophysical Research Letters 32: L09601. doi:10.1029/2005GL022751.   edit
  39. ^ IPCC AR4 chapter 10 [1] Table 10.7
  40. ^ Gregory JM; Huybrechts P; Raper SC (April 2004). "Climatology: threatened loss of the Greenland ice-sheet". Nature 428 (6983): 616. doi:10.1038/428616a. PMID 15071587. http://homepages.vub.ac.be/~phuybrec/pdf/Nature.Green.2004.pdf. "The Greenland ice-sheet would melt faster in a warmer climate and is likely to be eliminated — except for residual glaciers in the mountains — if the annual average temperature in Greenland increases by more than about 3 °C. This would raise the global average sea-level by 7 metres over a period of 1000 years or more. We show here that concentrations of greenhouse gasses will probably have reached levels before the year 2100 that are sufficient to raise the temperature past this warming threshold.".  
  41. ^ "Regional Sea Level Change" (Figure 11.16). Intergovernmental Panel on Climate Change. http://www.grida.no/climate/ipcc_tar/wg1/432.htm#fig1116.  
  42. ^ Lenton, T; N. Vaughan. "Geoengineering: a critical review". http://www.cosis.net/abstracts/EGU2008/09934/EGU2008-A-09934.pdf?PHPSESSID=. Retrieved 2009-02-23.  
  43. ^ Borenstein, Seth. “Obama Looking at Cooling Air to Fight Warming”, Associated Press via ABC News. (2009-04-09).
  44. ^ "ESA's ice mission CryoSat-2". esa.int. 11 September 2008. http://www.esa.int/esaLP/ESAOMH1VMOC_LPcryosat_0.html. Retrieved 2009-06-15.  
  45. ^ Svenningsson, Annakarin (2007-10-14). "Global Environmental Change - The Role of the Arctic Region". innovations-report.de. http://www.innovations-report.de/html/berichte/veranstaltungen/bericht-92741.html. Retrieved 2007-10-16.  
  46. ^ Wininger, Corinne (2007-10-26). "E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research". innovations-report.de. http://www.innovations-report.com/html/reports/environment_sciences/report-93680.html. Retrieved 2007-11-26.  
  47. ^ Eckel, Mike (2007-09-20). "Russia: Tests Show Arctic Ridge Is Ours". The Associated Press (The Washington Post). http://www.washingtonpost.com/wp-dyn/content/article/2007/09/20/AR2007092001703.html. Retrieved 2007-09-21.  
  48. ^ "Denmark aims for meeting of Arctic nations to discuss borders" (online). Denmark-Diplomacy (EUX.TV the Europe channel). 2007-09-13. http://www.eux.tv/article.aspx?articleId=14443. Retrieved 2007-09-16.  
  49. ^ "Conference in Ilulissat, Greenland: Landmark political declaration on the future of the Arctic". Ministry of Foreign Affairs of Denmark. 2008-05-28. http://www.um.dk/en/servicemenu/News/ConferenceInIlulissatGreenlandLandmarkPoliticalDeclarationOnTheFutureOfTheArctic.htm. Retrieved 2008-06-06.  
  50. ^ "The Ilulissat Declaration". um.dk. 2008-05-28. http://www.um.dk/NR/rdonlyres/BE00B850-D278-4489-A6BE-6AE230415546/0/ArcticOceanConference.pdf. Retrieved 2008-06-06.  

Further reading

External links


in 2007 from 2005 and also from 1979-2000 average]]  
Mass Trend]]

Arctic shrinkage is the decrease in size of the Arctic region (as defined by the 10 °C (50 °F) July isotherm)[citation needed]. This is a change in the regional climate generally agreed to be a result of global warming. Projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2060 and 2080[1] while another estimate puts this date at 2030.[2] Because of the rapid response of the Arctic to global warming, it is often seen as a high-sensitivity indicator of climate change. Scientists also point to the potential for release of methane from the Arctic region, especially through the thawing of permafrost and methane clathrates.

Contents

Modelling, history, and predictions of sea ice

Computer models predict that the sea ice area will continue to shrink in the future, although recent work has called into question their ability to accurately predict sea ice changes.[3] Current climate models frequently underestimate the rate of shrinkage.[4] In 2007 the IPCC reported that “the projected reduction [in global sea ice cover] is accelerated in the Arctic, where some models project summer sea ice cover to disappear entirely in the high-emission A2 scenario in the latter part of the 21st century.″ [5] There is currently no scientific evidence that a seasonally ice-free Arctic Ocean existed anytime in the last 700,000 years, although there were periods when the Arctic was warmer than it is today.[6][7] Scientists are studying possible causal factors such as direct changes resulting from the greenhouse effect as well as indirect changes such as unusual wind patterns,[8] rising Arctic temperatures,[9] or shifting water circulation[10] (such as increasing inflows of warm, fresh water to the Arctic Ocean from rivers.)

According to the Intergovernmental Panel on Climate Change, "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world."[11] Reduction of the area of Arctic sea ice means less solar energy is reflected back into space, thus accelerating the reduction.[12] Studies have shown that recent warming in the polar regions was due to the net effect human influence; the warming radiative forcing of greenhouse gases is only partially offset by the cooling effect of ozone depletion.[13]

[[File:|thumb|right|1870-2009 Northern hemisphere sea ice extent in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in Autumn up to 1940 reflects lack of data rather than a real lack of variation.]]

Reliable measurement of sea ice edge begin within the satellite era in the late 1970s. Before this the region was less well monitored by a combination of ships, buoys and aircraft.[14] On top of the long-term negative trend in recent years, attributed to global warming, there is considerable interannual variation.[15] Some of this variation may be related to effects such as the arctic oscillation, which may itself be related to global warming;[16] some of the variation is essentially random "weather noise".

The Arctic sea ice September minimum extent reached new record lows in 2002, 2005, and 2007 (39.2 percent below the 1979–2000 average). In 2007, Arctic sea ice broke all previous records by early August—a month before the end of melt season, with the biggest decline ever in Arctic sea ice minimum extent, more than a million square kilometers.[17] In the first time in human memory, the fabled Northwest Passage opened completely.[18] The dramatic 2007 melting surprised and concerned scientists.[19][20]

In 2008 and 2009, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.[21] Additionally, studies show a dramatic decline in ice age and thickness.[21] The Catlin Arctic Survey reported an average thickness of 1.8 meters across the northern Beaufort Sea, an area that had traditionally contained older, thicker ice.[22]

The rate of the decline in entire arctic ice coverage is accelerating. From 1979–1996, the average per decade decline in entire ice coverage was a −2.2% decline in extent (area with at least 15% sea ice coverage) and a −3% decline in area. For the decade ending 2008, these values have risen to −10.1% and −10.7%, respectively. These are comparable to the September to September loss rates in perennial ice not melted in summer, which averaged a retreat of −10.2% and −11.4% per decade, respectively for the period 1979–2007.[23] This is consistent with ICESat measurements indicating decreased thickness in arctic ice and a decline in multi-year ice. For the period 2005–2008, multi-year ice decreased −42% in coverage and −40% in volume, a loss of ~6300 km3.[24]

A 2010 study attributes that the recent Arctic temperature amplification was caused by Arctic shrinkage itself, that exposes to sun radiation water instead of ice, which has a lower reflectivity than ice.[25]

Effects

]] The effects of Arctic shrinkage include a marked decrease in Arctic sea ice; melting permafrost, leading to the release of methane, a potent greenhouse gas;[26] the release of methane from clathrates, leading to longer time-scale methane release;[27] the observed increase in melt on the Greenland Ice Sheet in recent years; and potential changes in patterns of ocean circulation. Scientists worry that some of these effects may cause positive feedbacks which could accelerate the rate of global warming.

Sea ice

File:Arctic melt trends
The number of days where the arctic is in the melt stage has increased since satellite records began in 1979. Red indicates more melting, blue less melting.

The sea ice in the Arctic region is in itself important in maintaining global climate due to its albedo (reflectivity).[28] Melting of this sea ice will therefore exacerbate global warming due to positive feedback effects, where warming creates more warming by increased solar absorption.[28][29] An important feedback in the Arctic currently is ice-albedo feedback. The loss of the Arctic sea ice may represent a tipping point in global warming, when 'runaway' climate change starts.[30][31] This would be due to the release of methane from permafrost and clathrates in the region, and also because of ice-albedo feedback effects. However, recent research has challenged the notion of ice-albedo feedback causing an imminent Arctic sea ice tipping point.[32][33]


April 3, 2007, the National Wildlife Federation urged the U.S. Congress to place polar bears under the Endangered Species Act.[34] Four months later, the United States Geological Survey completed a year-long study[35] which concluded in part that the floating Arctic sea ice will continue its rapid shrinkage over the next 50 years, consequently wiping out much of the polar bear habitat. The bears would disappear from Alaska, but would continue to exist in the Canadian Arctic Archipelago and areas off the northern Greenland coast.[36] Secondary ecological effects are also resultant from the shrinkage of sea ice; for example, Polar Bears are denied their historic length of seal hunting season due to late formation and early thaw of pack ice.

Loss of permafrost

Sea ice loss has melting effects on permafrost,[37] both in the sea,[38] and on land[39] and consequential effects on methane release, and wildlife.[39] Some studies imply a direct link, as they predict cold air passing over ice is replaced by warm air passing over the sea. This warm air carries heat to the permafrost around the Arctic, and melts it.[39] This thawing of the permafrost might accelerate methane release from areas like Siberia.[40]

Clathrate gun

Sea ice serves to stabilise methane deposits on and near the shoreline,[41] preventing the clathrate breaking down and outgassing methane into the atmosphere. Any methane released to the atmosphere will then causing further warming.

Melting of the Greenland Ice Sheet

Models predict a sea-level contribution of about 5 centimetres (2 in) from melting in Greenland during the 21st century.[42] It is also predicted that Greenland will become warm enough by 2100 to begin an almost complete melt during the next 1,000 years or more.[43][44]

Ice thickness measurements from the GRACE satellite indicate that ice mass loss is accelerating. For the period 2002–2009, the rate of loss increased from −137 Gt/yr to −286 Gt/yr, with an acceleration of −30 gigatonnes per year per year.[45]

Effect on ocean circulation

Although this is now thought unlikely in the near future, it has also been suggested that there could be a shutdown of thermohaline circulation, similar to that which is believed to have driven the Younger Dryas, an abrupt climate change event. There is also potentially a possibility of a more general disruption of ocean circulation, which may lead to an ocean anoxic event, although these are believed to be much more common in the distant past. It is unclear whether the appropriate pre-conditions for such an event exist today.

Control of Arctic shrinkage

Geoengineering

Geoengineering approaches offer interventions which may increase Arctic ice, or reduce its decline.[46] These operate either by regional effects (Arctic geoengineering) or global effects (geoengineering). Several specific Arctic geoengineering schemes have been proposed to reduce Arctic shrinkage. Further, scientists such as Paul Crutzen have argued for general geoengineering proposals such as using stratospheric sulfur aerosols to be used, which will affect the Arctic if deployed in or near this region.

According to John Holdren, Assistant to the President of the United States for Science and Technology, complete loss of summer sea ice in the Arctic would be a milestone that could justify geoengineering in order to purposely cool the climate. Holdren believes that complete loss of summer sea ice in the Arctic could signal an increased chance of "really intolerable consequences."[47]

Research

National

Individual countries within the Arctic zone, Canada, Denmark (Greenland), Finland, Iceland, Norway, Russia, Sweden, and the United States (Alaska) conduct independent research through a variety of organizations and agencies, public and private, such as Russia's Arctic and Antarctic Research Institute. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the Chinese Arctic and Antarctic Administration (CAA).

International

International cooperative research between nations has become increasingly important:

Territorial claims

Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' Arctic territorial claims in hopes of establishing resource development and new shipping lanes, in addition to protecting sovereign rights.[51]

Danish Foreign Minister Per Stig Møller and Greenland's Premier Hans Enoksen invited foreign ministers from Canada, Norway, Russia and the United States to Ilulissat, Greenland for a summit in May 2008 to discuss how to divide borders in the changing Arctic region, and a discussion on more cooperation against climate change affecting the Arctic.[52] At the Arctic Ocean Conference, Foreign Ministers and other officials representing the five countries announced the Ilulissat Declaration on May 28, 2008.[53][54]

See also

References

  1. ^ Bo, J.; Hall, A.; Qu, X. (2009). [Expression error: Unexpected < operator "September sea-ice cover in the Arctic Ocean projected to vanish by 2100"]. Nature Geoscience 2: 341. doi:10.1038/ngeo467.  edit
  2. ^ Roach, John (2009-10-15). "Arctic Largely Ice Free in Summer Within Ten Years?". National Geographic News. http://news.nationalgeographic.com/news/2009/10/091015-arctic-ice-free-gone-global-warming.html. Retrieved 2010-10-2. 
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Further reading

  • [Expression error: Unexpected < operator "International - The Arctic - Drawing lines in melting ice"]. The Economist 384 (8542): 47. 2007. OCLC 166288931. 
  • Miller, PA; SW Laxon, DL Feltham (2007). [Expression error: Unexpected < operator "Consistent and Contrasting Decadal Arctic Sea Ice Thickness Predictions from a Highly Optimized Sea Ice Model"]. Journal of Geophysical Research 112 (C7): C07020–2. doi:10.1029/2006JC003855. OCLC 170040287. 
  • Oyugi, JO; H Qiu, D. Safronetz (2007). [Expression error: Unexpected < operator "Global Warming and the Emergence of Ancient Pathogens in Canada's Arctic Regions"]. Medical Hypotheses 68 (3): 709. doi:10.1016/j.mehy.2006.09.006. OCLC 110702580. PMID 17064851. 
  • Schiermeier, Q (2007). [Expression error: Unexpected < operator "Polar Research: the New Face of the Arctic"]. Nature 446 (7132): 133–135. doi:10.1038/446133a. OCLC 110702580. PMID 17344829. 
  • Stroeve, J; MM Holland, W Meier, T Scambos, M Serreze (2007). [Expression error: Unexpected < operator "The Cryosphere – L09501 – Arctic Sea Ice Decline: Faster Than Forecast"]. Geophysical Research Letters 34 (9): n.p.. doi:10.1029/2007GL029703. OCLC 110702580. 
  • Xu, J; G Wang, B Zhang (2007). [Expression error: Unexpected < operator "Climate Change Comparison between Arctic and Other Areas in the Northern Hemisphere Since the Last Interstade"]. Journal of Geographical Sciences 17 (1): 43–50. doi:10.1007/s11442-007-0043-8. OCLC 91622949. 

External links


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