Arctic ice melts to second-lowest level: scientists...

Arctic sea ice melted to its second-lowest level this summer, rising slightly from 2007's record but still showing a downward trend that is a key symptom of climate change, U.S. scientists said on Tuesday.

The ice slipped to its minimum extent for 2008 on September 12, when it covered 1.74 million square miles (4.52 million square km), and now appears to be growing as the Arctic starts its seasonal cooldown, the National Snow and Ice Data Center said.

This is 33 percent below the average summer ice cover in the Arctic since satellites began measuring it in 1979 and is less than 10 percent above last year's all-time record low, said Walt Meier, a research scientist at the ice center.

"We're not as low as we were last year, which was the real mind-blowing record, but we're well below anything else we've had in the past," Meier said in a telephone interview from Boulder, Colorado.

One channel of the Northwest Passage -- a long-sought water route between Europe and Asia -- was open in both 2007 and 2008. This year also saw the opening of the Northern Sea Route, which runs through the Arctic Ocean along the Siberian coast.

The ice center said last month that there was substantial ice melt in the Chukchi Sea off the Alaskan coast in the Eastern Siberian Seas off Russia's east coast, home to one of the world's largest polar bear populations.

Because polar bears use sea ice floes as platforms for hunting seals, they are forced to swim longer distances when the ice melts, making them more likely to tire and drown.

Arctic ice is a factor in global climate and weather patterns. The difference between the cool air at the poles and warm air around the Equator drives air and water currents, including the jet stream, Meier said.

Sea ice helps hold in the cold around the North Pole because its white color reflects sunlight. When sea ice vanishes, the newly exposed dark water absorbs more of the sun's rays, accelerating the heating effect.

DOWNWARD TREND "GETTING STEEPER"

Even though the ice did not shrink as dramatically in 2008 as it did in 2007, Meier said this year's conditions were remarkable because they occurred in a relatively cool year. Last year's sea ice melt happened in a "perfect storm" of conditions -- the skies were warm and clear and winds pushed the ice around, spurring the melting.

This year it was cooler, Meier said. There were no favorable winds, "and yet we still came pretty close to the record."

"In terms of long-term climate, it's not a recovery in any sense of the word," he said. "The long-term trend is still steeply downward and getting steeper."

Because the climate system is so interconnected to what happens in the Arctic, there are likely to be more widespread impacts, he said.

The emission of the greenhouse gas carbon dioxide -- produced by burning fossil fuels as well as natural sources, including human breath -- is spurring global climate change, and its effects are amplified in the Arctic, he said.

The last seven years are among the seven lowest on record in terms of Arctic sea ice, Meier said.

"That's a real indication that this isn't any kind of temporary climate cycle. It's more an indication that we're heading toward the point where we're going to have that sea ice completely melt in the coming decades or perhaps sooner."