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Arctic shrinkage
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Arctic shrinkage is the shrinkage of the Arctic region (as marked by isotherms), due to changes in the regional climate. Effects of Arctic shrinkage include melting permafrost, leading to Arctic methane release, a marked decrease in Arctic sea ice and the observed increase in melt on the Greenland Ice Sheet in recent years. Whilst there is a periodic variation in sea-ice extent due to the Arctic oscillation, among other varying factors, there is a long-term negative trend in recent years, attributed to global warming.
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Encyclopedia
Arctic shrinkage is the shrinkage of the Arctic region (as marked by isotherms), due to changes in the regional climate. Effects of Arctic shrinkage include melting permafrost, leading to Arctic methane release, a marked decrease in Arctic sea ice and the observed increase in melt on the Greenland Ice Sheet in recent years. Whilst there is a periodic variation in sea-ice extent due to the Arctic oscillation, among other varying factors, there is a long-term negative trend in recent years, attributed to global warming. (It is notable that the Arctic oscillation itself is believed to be affected strongly by global warming.)
The Arctic also stores vast quantities of methane, a potent greenhouse gas in permafrost and clathrates. Arctic methane release is accelerating rapidly due to Arctic shrinkage. This has the potential to create a runaway climate change event, which may have features in common with the Great dying (a mass extinction), and with the Paleocene-Eocene thermal maximum (an abrupt climate change event), although both of these took place in a climate much warmer than today's. 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. This is now thought unlikely in the near future. 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.
Computer models predict that the sea ice area will continue to shrink in the future, though there is no consensus on when the Arctic Ocean might become ice-free in summer. Current climate models frequently underestimate the rate of shrinkage. 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.? 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. 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, or shifting water circulation (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." Reduction of the area of Arctic sea ice means less solar energy is reflected back into space, thus accelerating the reduction.
The lowest extent of sea ice was in 2007; that of 2008 was slightly greater The area covered at a particular time is what determines the albedo of the Arctic region and thus has an important effect on future warming (or cooling) trends through ice-albedo feedback.
Sea ice may reach a tipping point and then be lost. The loss of the Arctic sea ice may represent a tipping point in global warming, when 'runaway' climate change starts. This is due to the release of methane from permafrost and clathrates in the region, and also because of ice-albedo feedback effects. Recent research, however, has challenged the notion of an imminent Arctic sea ice tipping point.
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.
Effects
The thawing of the Arctic might have global effects. Quantities of carbon exist in the form of methane stored in permafrost and clathrates. A loss of sea ice cover is expected to cause the increasing release of this stored methane back into the atmosphere. While the carbon locked up in this methane was absorbed from the atmosphere in the form of CO2, it will be re-released largely as gaseous methane, which is a potent greenhouse gas. However, recent atmospheric methanes levels show little increase, and current atmospheric methane concentrations are far below IPCC projections.
Sea ice
The sea ice in the Arctic region is in itself important in maintaining global climate due to its albedo (reflectivity). Melting of this sea ice will therefore exacerbate global warming due to positive feedback effects, where warming creates more warming by increased solar absorption.
April 3, 2007, the National Wildlife Federation urged the U.S. Congress to place polar bears under the Endangered Species Act.
Four months later, the United States Geological Survey completed a year-long study 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. 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, both in the sea, and on land and consequential effects on methane release, and wildlife. 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. This thawing of the permafrost might accelerate methane release from areas like Siberia.
Clathrate gun
Sea ice serves to stabilise methane deposits on and near the shoreline, preventing the clathrate breaking down and outgassing methane into the atmosphere. Any methane released to the atmosphere will then causing further warming. Should the gain of this feedback loop be sufficiently high, a 'runaway' process will occur. This is known as a clathrate gun effect.
Loss of Greenland Ice Sheet
Greenland's ice sheet contains enough fresh water as ice to raise sea level worldwide by . Models predict a sea-level contribution of about from melting in Greenland during the 21st century. 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. It is viewed by some scientists that wholly inadequate attention is being given to this issue,.
Control of Arctic shrinkage
Mitigation
Mitigation of global warming is proposed under mechanisms such as the Kyoto protocol. However, all scenarios envisaged by the IPCC involve the continuing increase of concentrations of atmospheric of greenhouse gases, and hence an increase in global warming. Therefore, the forcing of climate which has been concurrent with recent melting is expected to worsen (not improve) the situation for the Arctic in the short term.
Geoengineering
Geoengineering approaches offer interventions which may increase Arctic ice, or reduce its decline. These operate either by regional effects (Arctic geoengineering) or global effects (geoengineering).
Recent expert statements
2007
Associate professor Carl Egede Bøggild, University Centre in Svalbard was quoted by The New York Times as saying the melting rate of Greenland's ice sheet could be as high as 80 cubic miles per year.
Leif Toudal Pedersen of the Danish National Space Center commented about Arctic sea ice: "The strong reduction in just one year certainly raises flags that the ice (in summer) may disappear much sooner than expected...." The International Ice Charting Working Group issued a statement that the Arctic sea ice in September 2007 had reached the lowest extent "in the history of ice charting."
A 2007 study by Professor Wieslaw Maslowski at the U. S. Naval Postgraduate School, Monterey, California predicted that the Arctic Ocean may be free of ice during summer by as soon as 2013. The study used data sets from 1979 to 2004 and did not include the more recent record low ice minima set in 2005 and 2007. Maslowski suggested that other researchers seriously underestimated some key melting processes, producing models that predict an ice free Arctic Ocean to first occur from 2040 to 2100.
Professor Peter Wadhams from University of Cambridge, UK, agreed that some models have not been taking proper account of the physical processes occurring in nature. He said that Maslowski's model is more efficient because it takes account of processes that happen internally in the ice. Wadhams predicted that, in the end, the Arctic ice will just melt away quite suddenly, perhaps not as early as 2013 but much earlier than 2040.
In December 2007, the Canadian Press selected Arctic shrinkage as Canada's biggest environmental story of the year. Environment Canada senior climatologist David Phillips summed it up: "This huge chunk of ice the size of Ontario vanished within one year."
2008
According to Walt Meier of the National Snow and Ice Data Center (NSIDC), NASA satellite data shows that there has been a 50% decrease of perennial Arctic ice between February 2007 and February 2008.
While the cold winter did allow ice to re-cover much of the Arctic Sea surface area during the Winter of 2007/2008, conditions were far from normal as the pair of NASA images to the right reveals. The February 2008 ice pack contained much more young ice than the long-term average, and the total volume was arguably the lowest on record. In the past, more ice survived the summer melt season and had the chance to thicken over the following winter. In the mid- to late 1980s, over 20 percent of Arctic sea ice was at least six years old; in February 2008, just 6 percent of the ice was six years old or older.
NSIDC says Arctic sea ice extent during the 2008 melt season dropped to the second-lowest level since satellite measurements began in 1979, reaching the lowest point in its annual cycle of melt and growth on September 14, 2008. Average sea ice extent over the month of September... was 4.67 million square kilometers... The record monthly low, set in 2007, was 4.28 million square kilometers... the now-third-lowest monthly value, set in 2005, was 5.57 million square kilometers... The 2008 season strongly reinforces the thirty-year downward trend in Arctic ice extent. The 2008 September low was 34% below the long-term average from 1979 to 2000 and only 9% greater than the 2007 record... Because the 2008 low was so far below the September average, the negative trend in September extent has been pulled downward, from –10.7 % per decade to –11.7 % per decade.
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:
- (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) is scheduled in 2009 to launch CryoSat-2 which will provide satellite data on Arctic ice cover change rates.
- 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 Nynäshamn, Sweden, October, 2007.
- 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.
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. At the Arctic Ocean Conference, Foreign Ministers and other officials representing the five countries announced the Ilulissat Declaration on May 28, 2008.
See also
Further reading
External links
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