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The image above shows where average air temperatures (October 2010-September 2011) were up to 3 degrees Celsius above (red) or below (blue) the long-term average (1981-2010). Arctic Sea ice]] in 2007 from 2005 and also from 1979 2000 average Greenland Ice Sheet Mass Trend Ongoing changes in the climate of the Arctic include rising temperatures, loss of sea ice, and melting of the Greenland ice sheet.[1] Projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2060 and 2080,[2] while another estimate puts this date at 2030[3], and another at 2013 or earlier.[4] Because of the amplified 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. Arctic climate changes are summarized in the IPCC Fourth Assessment Report and the Arctic Climate Impact Assessment. The National Oceanic and Atmospheric Administration (NOAA)'s Arctic Report Card presents annually updated, peer-reviewed information on recent observations of environmental conditions in the Arctic relative to historical records.
Modelling, history, and predictions of sea ice Sea ice coverage in 1980 (bottom) and 2012 (top), as observed by passive microwave sensors on NASA s Nimbus-7 satellite and by the Special Sensor Microwave Imager/Sounder (SSMIS) from the Defense Meteorological Satellite Program (DMSP). Multi-year ice is shown in bright white, while average sea ice cover is shown in light blue to milky white. The data shows the ice cover for the period of November 1 through January 31 in their respective years. Seasonal variation and long term decrease of Arctic sea ice volume as determined by measurement backed numerical modelling.[5] 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.[6] Current climate models frequently underestimate the rate of sea ice retreat.[7] 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. [8] 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.[9][10] 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,[11] rising Arctic temperatures,[12] or shifting water circulation[13] (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."[14] Reduction of the area of Arctic sea ice means less solar energy is reflected back into space, thus accelerating the reduction.[15] 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.[16] 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.[17] On top of the long-term negative trend in recent years, attributed to global warming, there is considerable interannual variation.[18] Some of this variation may be related to effects such as the arctic oscillation, which may itself be related to global warming;[19] 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.[20] In the first time in human memory, the fabled Northwest Passage opened completely.[21] The dramatic 2007 melting surprised and concerned scientists.[23] In 2008 and 2009, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.[24] The sea ice thickness field, and accordingly the ice volume and mass, is much more difficult to determine than the extension. Exact measurements can be made only at a limited number of points. Because of large variations in ice and snow thickness and consistency air- and spaceborne measurements have to be evaluated carefully. Nevertheless the studies made support the assumption of a dramatic decline in ice age and thickness.[24] 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.[25] Another approach[5] is to simulate ice growth, melting and drift numerically in an integrated ocean-atmosphere model with input parameters fine tuned to fit model output to known thickness and extent data. The resulting time development shows a decrease of ice mass that is striking even after consideration of a possibly somewhat larger error bar than that of the extension data. Near complete ice freeness of the arctic ocean in late summer is probable as early as 2018. 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 ice extent (i.e., area with at least 15% sea ice coverage) and a 3% decline in ice 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 year-round ice (i.e., perennial ice, which survives throughout the year), which averaged a retreat of 10.2% and 11.4% per decade, respectively, for the period 1979 2007.[26] 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.[27] A 2010 study attributes that the recent Arctic temperature amplification was caused by the loss of sea ice itself, which exposes water instead of more reflective ice to solar radiation.[28] Effects Earlier retreat of sea ice in Barrow, Alaska The effects of Arctic climate change include a marked decrease in Arctic sea ice; melting permafrost, leading to the release of methane, a potent greenhouse gas;[29] the release of methane from clathrates, leading to longer time-scale methane release;[30] 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 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.Projected change in polar bear habitat from 2001 2010 to 2041 2050 The sea ice in the Arctic region is in itself important in maintaining global climate due to its albedo (reflectivity).[31] Melting of this sea ice will therefore exacerbate global warming due to positive feedback effects, where warming creates more warming by increased solar absorption.[31][32] 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.[33][34] 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.[35][36] The reduction of sea ice has also boosted the productivity of phytoplankton by about twenty percent over the past thirty years. However, the effect on marine ecosystems is unclear, since the larger types of phytoplankton, which are the preferred food source of most marine animals, do not appear to have increased as much as the smaller types. So far, arctic phytoplankton have not had a significant impact on the global carbon cycle.[37] April 3, 2007, the National Wildlife Federation urged the United States Congress to place polar bears under the Endangered Species Act.[38] Four months later, the United States Geological Survey completed a year-long study[39] 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.[40] 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,[41] both in the sea,[42] and on land[43] and consequential effects on methane release, and wildlife.[43] 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.[43] This thawing of the permafrost might accelerate methane release from areas like Siberia.[44] When the temperature warms sufficiently to cause the deep layers of ice underground (the permafrost) to melt, ground water will start seeping into the underlying strata and aquifer and thereby reduce the level of moisture. It may also become farmland after it is drained by canals as was done in the northern American Midwest region so wheat and corn could be farmed in what was previously swampland. [45] Increased vegetation The less severe winters in tundra areas allow shrubs such as alders to replace moss and lichens. The feedback effect of shrubs on the tundra's permafrost is unclear, however. In the winter they trap more snow which insulates the permafrost from extreme cold spells, but in the summer they shade the ground from direct sunlight.[46] Clathrate gun Sea ice serves to stabilise methane deposits on and near the shoreline,[47] preventing the clathrate breaking down and outgassing methane into the atmosphere. Any methane released to the atmosphere will then cause further warming. Melting of the Greenland Ice Sheet Albedo Change in Greenland Models predict a sea-level contribution of about from melting in Greenland during the 21st century.[48] 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.[49][50] 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.[51] 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 climate change Geoengineering Geoengineering approaches offer interventions which may increase Arctic ice, or reduce its decline.[52] These operate either by regional effects (Arctic geoengineering) or global effects (geoengineering). Several specific Arctic geoengineering schemes have been proposed to reduce Arctic climate change. 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."[53] 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: - DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies): European integrated project "specifically concerned with the potential for a significantly reduced sea ice cover, and the impacts this might have on the environment and on human activities, both regionally and globally".
- European Space Agency (ESA) launched CryoSat-2 on 8 April 2010. It provides satellite data on Arctic ice cover change rates.[54]
- International Arctic Buoy Program: deploys and maintains buoys that provide real-time position, pressure, temperature, and interpolated ice velocity data
- International Arctic Research Center: Main participants are the United States and Japan.
- International Arctic Science Committee: non-governmental organization (NGO) with diverse membership, including 18 countries from 3 continents.
- 'Role of the Arctic Region', in conjunction with the International Polar Year, was the focus of the second international conference on Global Change Research, held in Nyn shamn, Sweden, October, 2007.[55][56]
- SEARCH (Study of Environmental Arctic Change): Supported by the Arctic Research Office, a division of the United States' National Oceanic and Atmospheric Administration (NOAA), and the Russian Academy of Sciences.
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.[57] Danish Foreign Minister Per Stig M ller 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.[58] At the Arctic Ocean Conference, Foreign Ministers and other officials representing the five countries announced the Ilulissat Declaration on May 28, 2008.[59][60] See also References Further reading External links ar: de:Folgen der globalen Erw rmung in der Arktis es:Deshielo rtico sk: bytok adu v Arkt de fi:Arktisen alueen kutistuminen
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![Arctic Sea ice]] in 2007 from 2005 and also from 1979 2000 average](http://www.tutorgig.info/ed/File:2007_Arctic_Sea_Ice.jpg%7Cthumb%7CVery_substantial_decrease_in_%5B%5BPolar_ice_packs#Extent and trends of polar ice packs){kind=link}
![Seasonal variation and long term decrease of Arctic sea ice volume as determined by measurement backed numerical modelling.[5]](http://www.tutorgig.info/ed/File:Plot_arctic_sea_ice_volume.svg%7Cthumb){kind=link}
![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.](http://www.tutorgig.info/ed/File:Seaice-1870-part-2009.png%7Cthumb%7C1870%E2%80%932009_Northern_hemisphere_%5B%5BMeasurement_of_sea_ice#Sea ice extent){kind=link}
