Monday, 2 February 2009

Polar warming

Over the last 50 years, Antarctica has warmed at a rate of about 0.1 degree centigrade in the east of the continent and about 0.17 in the west per decade. The results of this research were published in an article by Steig et al in Nature magazine (Nature 457, 459-462 (22 January 2008). Discussing the results on the web (http://www.realclimate.org/index.php/archives/2009/01/state-of-antarctica-red-or-blue/) one of the authors says that the trend is difficult to explain without taking into account the effect of global warming linked to atmospheric greenhouse gases.

If this trend continues, it will result in a major melting of the western Antarctic ice sheet. Taken in conjunction with increased flow from the Greenland ice sheet (IPCC Climate Change 2007: Synthesis Report – Summary for Policymakers) we may be facing a serious rise in sea levels over this century. Clearly, this would have a huge global impact on people and wildlife, with the human population crowded into ever-decreasing amounts of space, with ever-decreasing amounts of land for growing food.

As the ice retreats, exploitation of the Arctic’s resources becomes easier, and the EU and other nations are lining up to exploit the oil and natural gas which are present. Fishing craft are exploiting the marine life, and tourism is also increasing in the region. As the lands fringing the arctic sea become green, trees, grizzly bears and caribou move northwards, competing with native arctic wildlife. Additionally, migration of polar bears and arctic island caribou may well be disrupted as the sea ice breaks up, and changing ecosystems will affect many arctic-adapted creatures and northern peoples. The darker land has a lower albedo than ice, which means more sunlight is absorbed, further warming the land and being trapped by the greenhouse gases in the atmosphere.

The melting of the permafrost has potentially catastrophic consequences, both in terms of erosion and subsidence and, more critically, in the release of methane. There is great deal of methane locked up in the permafrost and, as it melts, the methane (a greenhouse gas 21 times as powerful - if shorter lived - than carbon dioxide) is released into the atmosphere. It is also possible that the warming of the region and thawing of the permafrost will lead to the release of subsea methane hydrate as methane gas. This gas has been linked to previous mass extinctions and climatic changes, such as the Permian-Triassic mass extinction which killed about 96% of all life (http://pangea.stanford.edu/research/Oceans/GES205/methaneGeology.pdf).

Evidence of the release of methane hydrate was reported in the arctic region last year. Shakhova et al (2008) estimate that not less than 1,400 Gt of Carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and that 5-10% of that area is subject to puncturing by open taliks (a patch of unfrozen ground in an area of permafrost). They conclude that "release of up to 50 Gt of predicted amount of hydrate storage [is] highly possible for abrupt release at any time" (http://www.cosis.net/abstracts/EGU2008/01526/EGU2008-A-01526.pdf).

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