Archive - Oct 15, 2008

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This summer, for the first time, both the fabled Northwest Passage through the upper reaches of North America and the Northern Sea Route above Russia opened up, apart from drifting ice. Overall, the expanse of Arctic sea ice was the second smallest in the 30 years of monitoring (summer 2007 was the smallest), and that left an islandlike polar ice cap surrounded by open water. In just the past five years, summer ice has shrunk by more than 25 percent, and so has its average thickness. One consequence of this change is that much of the sun's heat formerly reflected back out to space by the ice sheets is now being absorbed, entrenching the warming process. The acceleration of the ice melt is outstripping earlier predictions of a basically ice-free Arctic summer by mid- or late century. NASA climate scientist H. Jay Zwally now anticipates that most of the Arctic will lose summer ice in only five to 10 years. "We appear to be going through a tipping point," he says.

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