NOAA study backs up predictions of sea ice loss

Sea ice loss in regions of the Arctic is likely to exceed 40 percent by 2050 compared with the 1980s, according to an analysis of ice computer models by researchers at the National Oceanic and Atmospheric Administration.

 

A 40 percent loss of sea ice off Alaska in the Beaufort Sea could have profound effects on marine mammals dependent on the sea ice such as polar bears, now under consideration by the U.S. Fish and Wildlife Service for "threatened" status under the Endangered Species Act because of changes in the animals' habitat from global warming.

Researchers James Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory in Seattle, and Muyin Wang, a meteorologist at NOAA's Joint Institute for the Study of the Atmosphere and Ocean at the University of Washington in Seattle, reviewed 20 computer models provided through the International Panel on Climate Change in its fourth assessment report released this year.

The researchers compared those models' projections from 1979 through 1999 with actual sea ice observations and eliminated models deemed to be less reliable.

"About half the models were off, or outliers, in that they had too much ice or too little ice or not enough difference between the ice in the summer or winter compared to the observations of ice we already have," Overland said at a news conference Thursday.

The analysis increases the confidence in projections that greenhouse gas emissions will eliminate 40 percent of Arctic sea ice in summer and winter by the middle of the century, Overland said, based on emissions already in the atmosphere and those pumped out in the next two decades. In the 1980s, sea ice receded 30 to 50 miles each summer off the north coast of Alaska, Overland said.

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

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

It also will mean a changing ecosystem for commercial fishermen and marine mammals in the Bering Sea, Overland said.

With sea ice present, much of the nutrients produced in the ocean feed simple plankton that bloom and sink to the ocean floor, providing rich habitat for crabs, clams and the mammals that feed off them, including gray whales and walrus.

"If you don't have the ice around, the productivity stays up closer to the surface of the ocean," Overland said. "You actually have a change in the whole ecosystem from one that depends on the animals that live on the bottom to one that depends on the animals that live in the water column. So you have winners and losers."

That could mean short-term gains for salmon and pollock, he said. But it also could mean that fishermen will have to travel farther north to fish in Alaska's productive waters, and warm-water predators might also begin showing up.