Wednesday, March 19, 2008

Scientists monitoring sea ice around the high Arctic and glaciers on the world's highest mountains are detecting ominous new changes linked to the warming global climate, they reported Tuesday.

The Arctic's thin and salty seasonal sea ice that freezes and thaws in the far north every year actually spread more widely this past winter, but the team of NASA scientists keeping watch over the ice by satellite said the much thicker perennial ice that normally remains throughout the Arctic summer has grown much thinner and some is already melting and drifting southward as winter ends.

In a related development, scientists at the World Glacier Monitoring Service, based at the University of Zurich in Switzerland, reported that some 30 major glaciers around the world are shrinking fast, threatening to increase floods in some regions and to decrease precious water supplies in others.

The extent of total sea ice - both thick and thin - around the North Pole reached an all-time low last year - nearly 25 percent less than the record low set two years earlier. This winter, the area of short-lived thin seasonal ice increased due to an episode of somewhat colder-than-average sea surface temperatures, but the thicker perennial ice that stays year after year declined substantially, the NASA scientists told reporters during a press briefing on the team's latest findings.

Perennial ice that lasts six years or more once covered as much as 60 percent of the oceans of the Arctic region, according to Walter Meier of the national Snow and Ice Center at the University of Colorado, but by last month, the same type of older sea ice had decreased to only 6 percent coverage, he said.

"That really old, thick ice is tough as nails," Meier said, "But it's growing thinner and thinner and much more susceptible to melting. You definitely have a situation now where the perennial ice is rushing out of the Arctic and into the Atlantic."

From the air, the ice appears to be covering most of the Arctic, Meier said, but it's all the thin stuff, and it melts every summer. "It's a facade, like a Hollywood set," he said. "There's no building behind it."

Meier and his colleagues, Josefino Comiso and Seelye Martin of NASA's Cryospheric Sciences Program, gather their data regularly from a satellite named IceSat that has been orbiting the poles since 2003 and measuring the declining extent of the ice as well as its thickness.

Meanwhile, Swiss scientists have been tracking the world's glaciers for more than a century, and the current team is now linked to the U.N. Environment Program.

Data from 30 glaciers in nine mountain ranges from Alaska, the Andes, Antarctica, the Alps and the Himalayas showed that between 2004 and 2006 the average rate of melting and thinning more than doubled, the team reported.

"The latest figures are part of what appears to be an accelerating trend with no apparent end in sight," said Wilfrid Haeberli, director of the Swiss-based glacier monitoring service.

The glaciers in the survey were melting at an average rate of about a foot a year between 1980 and 1999, Haeberli said. But since "the turn of the millennium," he said, the loss rate has increased to nearly 20 inches a year.

The rapid melting of glaciers in every mountain region poses serious dangers, from drinking water shortages to flash floods to decreases in available irrigation water, said Peter Gleick, president of the Oakland-based Pacific Institute, which is recognized as a major authority on water issues.

"This is more bad news from the real world," Gleick said Tuesday in a phone interview. "It's more evidence of climate change and it's pretty compelling.

"With so many glaciers melting faster, in the long run that means severely diminished water supplies for many parts of the world that need it badly."