Arctic shrinkage is the marked decrease in Arctic sea ice and the observed melting of the Greenland Ice Sheet in recent years. 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; a common theory estimates between 2040 and 2100. Scientific analysis currently has no evidence of seasonally ice-free Arctic over more than 700,000 years, although there were warmer periods. Scientists are studying possible cause and effect factors such as unusual wind patterns, rising Arctic temperatures, or shifting water circulation.
Greenland's ice sheet contains enough fresh water as ice to raise sea level worldwide by 7 metres (23 ft). Models predict a sea-level contribution of about 5 centimetres (2 in) 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.
Sea ice loss could cause more rapid warming of Northern latitudes, with effects on permafrost, methane release, and wildlife.
In September 2007, 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 bears’ habitat. The bears would disappear from Alaska, but would continue to exist in the Arctic archipelago of Canada and areas off the northern Greenland coast. April 3, 2007, the National Wildlife Federation urged the U.S. Congress to place polar bears under the Endangered Species Act.
According to the most ambitious of IEA emissions scenarios, cutting global CO2 emissions by 50 percent to 2050 is possible. However ambitious, this will only lead to a further rise in CO2 concentrations and temperatures, compared to 2008 values. Concluding from that present mitigation efforts will not be able to prevent continued Arctic melting.
Perhaps other means are at hand to halt Arctic melting, for instance geoengineering approaches influencing local sea-ice albedo or ice dynamics. In September 2008 building the St. Lawrence Dam was proposed, a plan to influence temperature and salinity in the Arctic Ocean, favouring sea ice conditions. Up to date this seems to be the only publicly proposed geoengineering approach focusing specifically on halting Arctic shrinkage.
Halting Arctic shrinkage may also have a beneficial, stabilizing influence on the global climate system as it will slow down two important positive feedbacks, one being the albedo effect (that increases temperature rise), the other Arctic methane release from thawing permafrost (that increases greenhouse gas emissions).
As with the rest of the planet, the climate in the Arctic has changed throughout time. About 55 million years ago it is thought that parts of the Arctic supported subtropical ecosystems (Serreze and Barry 2005) and that Arctic sea-surface temperatures rose to about 23 °C (73 °F) during the Paleocene–Eocene Thermal Maximum. In the more recent past, the planet has experienced a series of ice ages and interglacial periods over about the last 2 million years, with the last ice age reaching its maximum extent about 18,000 years ago and ending by about 10,000 years ago. During these ice ages, large areas of northern North America and Eurasia were covered by ice sheets similar to the one found today on Greenland; Arctic climate conditions would have extended much farther south, and conditions in the present-day Arctic region were likely colder. Temperature proxies suggest that over the last 8000 years the climate has been stable, with globally averaged temperature variations of less than about 1 °C (2 °F; see Paleoclimate).
For More Information: Arctic Shrinkage
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