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.
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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]
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]
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.
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]
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.
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]
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.
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]
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.
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]
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 cooperative research between nations has become increasingly important:
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]
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 |
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]
]] 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.
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.
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]
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.
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]
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.
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]
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 cooperative research between nations has become increasingly important:
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]
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   | Arctic Sea Ice Melting Rapidly, ESA Satellite Images Show - ScienceMode » Arctic Sea Ice Melting Rapidly, ESA Satellite Images Show - Science News - From Science Mode.com |
| | 'Drastic' shrinkage in Arctic ice - BBC NEWS | Science/Nature | 'Drastic' shrinkage in Arctic ice |
| | Warming Is Seen as Wiping Out Most Polar Bears - The New York Times > Log In |
| | Melting glacier uncovers island - Melting image - Photos: Melting glacier uncovers island - CNET News |
| | Arctic Change website, in near-realtime - A Near-Realtime Arctic Change Indicator website |
| | Study: Circulation Shift May Be Melting Arctic Sea Ice - FOXNews.com - Study: Circulation Shift May Be Melting Arctic Sea Ice - Science News | Science & Technology | Technology News |
| | International Arctic Buoy Programme - International Arctic Buoy Programme |
| | World Wildlife Foundation's International Arctic Programme - WWF International - Arctic conservation |
| | International Arctic Research Center - International Arctic Research Center Home Page |
| | International Arctic Science Committee - Arctic Portal - IASC |
| | 38th Annual International Arctic Workshop 2008 - Arctic Workshop 2008: 38th Annual |
| | Arctic summers ice-free 'by 2013' - BBC NEWS | Science/Nature | Arctic summers ice-free 'by 2013' |
| | Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change - Climate Change 2001: Impacts, Adaptation and Vulnerability |
| | Melting Arctic ice cap top Canadian weather story of 2007: Environment Canada - Prince George Citizen - Melting Arctic ice cap top Canadian weather story of 2007: Environment Canada |
| | Earth - melting in the heat? - BBC NEWS | Science/Nature | Earth - melting in the heat? |
| | Climate Change 2001: The Scientific Basis - Climate Change 2001: The Scientific Basis |
| | "The Science Behind the Shrinking Arctic Ice Cap" - The Science Behind the Shrinking Arctic Ice Cap | Pew Center on Global Climate Change: The Pew Center on Global Climate Change |
| | "The Arctic Ocean and Post-Jurassic Paleoclimatology" - Climate in Earth History: Studies in Geophysics |
| | ''The Arctic Sea Ice Ecosystem'' - The Arctic sea ice ecosystem - Google Books |
| | Recent cold snap helping Arctic sea ice, scientists find - Recent cold snap helping Arctic sea ice, scientists find |
| | Record Arctic ice shrinkage is seen as global warming effect - SCIENCE FILE - Record Arctic ice shrinkage is seen as global warming effect - Los Angeles Times |
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