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Friday, June 25, 2010

DailyKos: Arctic Sea Ice Meltdown Accelerates

Arctic Sea Ice Meltdown Accelerates: DK Greenroots

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Thin Arctic sea ice, is cracking up and melting down at record rates so far this year. A central core of ice north of Greenland is intact while most of ice is failing across the Arctic. The melting of Arctic sea ice has more profound ecological and climatological implications than the BP oil disaster in the Gulf of Mexico.

High pressure and beautiful sunny weather at the north pole research station yesterday was reminiscent of the warm weather that led to the record low sea ice levels in September 2007.

This year's sea ice meltdown is well ahead of 2007 in loss of both area and thickness. The ice is failing at a record pace, in part, because it is at a record low thickness for the date. This ice is thinning at a record rate because of warm air temperatures above and because of melting from below.

Sea ice extent is well less for this date than it was in the record minimum year 2007. This year's ice extent is 3.9 standard deviations below normal according to a comment below by math and stats expert Keith Pickering, so it cannot be explained by random variability.

Atmospheric pressure and wind patterns this past winter were favorable for preserving multi-year sea ice. High pressure in the Arctic last winter led to less sea ice export out of the Arctic than normal. The increase in multi-year sea ice last winter has been the basis for some experts predicting that there might be a rebound in sea ice levels this summer and fall. First year sea ice is generally thin and relatively salty so most of it doesn't survive the summer. Normally, the increase of multiyear sea ice would be a basis for predicting an increase in the sea ice minimum this September.

Multi-year sea ice 2009 vs 2010

However, very warm temperatures in the Arctic in May, as much as 10 °F above normal offshore of Siberia, is melting the thinner-than-normal ice rapidly.

A large amount  of the multiyear sea ice has been stretched thin and transported south where it is unlikely to survive the summer.
Wind patterns during most of May have continued to push this ice to the west, placing more ice into the Chukchi Sea and keeping the ice further south than in recent years. Given the extent of melt over the past several years and the southern location of this old ice, we expect that it will completely melt out (ed with limited exceptions).
The University of Colorado team's forecast as of mid June is for a probable record low ice extent this fall.
Our best guess at this point for end-­‐of-­‐summer ice extent ranges from 4.5 x 10^6 km² at the high end to 3.8 x 10^6 km² at the low end.

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