Such a loss could have profound effects on mammals dependent on the sea ice, such as polar bears, now being considered for threatened species status because of changes in habitat due to global warming. It could also threaten the catch of fishermen.

In the 1980s, sea ice receded 30 to 50 miles each summer off the north coast, said James Overland, a Seattle-based oceanographer for the National Oceanic and Atmospheric Administration.

"Now we're talking about 300 to 500 miles north of Alaska," he said of projections for 2050.

That's far past the edge of the highly productive waters over the relatively shallow continental shelf, considered important habitat for polar bears and their main prey, ringed seals, as well as other ice-dependent mammals, such as walrus.

The NOAA researchers reviewed 20 computer scenarios of the effects of warming on sea ice, used by the United Nations' Intergovernmental Panel on Climate Change in its assessment report released this year.

The researchers compared those models with observations from 1979 through 1999, Overland said, and concluded that the summer ice in the Beaufort Sea likely will have diminished by 40 percent, compared with its 1980s area.

The same is likely for the East Siberian-Chukchi Sea region off northwest Alaska and Russia. In contrast, Canada's Baffin Bay and Labrador showed little predicted change.

Source - CNN

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