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Politics : The Environmentalist Thread -- Ignore unavailable to you. Want to Upgrade?

To: Triffin who wrote (12200)	5/2/2007 1:38:38 PM
From: Triffin	Respond to of 36917

Here's some text from Wiki on Greenland Ice Sheet .. The Greenland Ice Sheet has experienced record melting in recent years and is likely to contribute substantially to sea level rise as well as to possible changes in ocean circulation in the future. The area of the sheet that experiences some melting has increased about 16% from 1979 (when measurements started) to 2002 (most recent data). The area of melting in 2002 broke all previous records [ACIA, 2004]. In 2006, estimated monthly changes in the mass of Greenland's ice sheet suggest that it is melting at a rate of about 239 cubic kilometres (57.3 cubic miles) per year. These measurements came from the US space agency's Grace (Gravity Recovery and Climate Experiment) satellite, launched in 2002, as reported by BBC News, 11 August 2006.If the entire 2,85 million km3 of ice were to melt, global sea levels would rise 7,2 m (23.6 ft.)[IPCC, 2001]. Recently, fears have grown that continued global warming will make the Greenland Ice Sheet cross a threshold where long-term melting of the ice sheet is inevitable. Climate models project that local warming in Greenland will exceed 3 degrees Celsius during this century. Ice sheet models project that such a warming would initiate the long-term melting of the ice sheet, leading to a complete melting of the ice sheet (over centuries), resulting in a global sea level rise of about seven meters [ACIA, 2004]. Such a rise would inundate almost every major coastal city in the world. How fast the melt would eventually occur is a matter of discussion. In [IPCC, 2001], the expected 3 degrees warming at the end of the century would, if kept from rising further, result in about 1 meter sea level rise over the next millennium Several factors determine the net rate of growth or decline. These are accumulation of snow in the central parts, which adds mass and lowers sea level melting of ice along the sheet's margins (runoff) and bottom, which decreases mass and raises sea level iceberg calving into the sea from outlet glaciers also along the sheet's edges, which also decreases mass and raises sea level. IPCC [IPCC, 2001] estimates the accumulation to 520 ± 26 Gigatonnes of ice per year, runoff and bottom melting to 297±32 Gt/yr and 32±3 Gt/yr, respectively, and iceberg production to 235±33 Gt/yr. On balance, they estimate -44 ± 53 Gt/yr, which means that on average the ice sheet may currently be melting, though it can't be determined for sure. The most recent research using data from 1996 to 2005 shows that the ice sheet is thinning even faster than supposed in [IPCC, 2001]. According to the study, in 1996 Greenland was losing about 96 km3 per year in mass from its ice sheet. In 2005, this had increased to about 220 km3 a year due to rapid thinning near its coasts [JPL, 2006], while in 2006 it was estimated at 239 km3 per year [1]. The melt zone, where summer warmth turns snow and ice into slush and ponds of meltwater, has been expanding at an accelerating rate in recent years. When the meltwater seeps down through cracks in the sheet, it accelerates the melting and, in some areas, allow the ice to slide more easily over the bedrock below, speeding its movement to the sea. Besides contributing to global sea level rise, the process adds freshwater to the ocean, which may disturb ocean circulation and thus regional climate [ACIA, 2004]. Note that the centuries long process to melt the Greenland Ice Sheet is predicated on a local 3 degree rise in temps that models predict .. In actual fact, the scientists aren't even sure if the Greenland Ice Sheet is in a current net melt mode ........ Triff ..