Thursday, December 29, 2011

Melting glaciers mean double trouble for water supplies

Rick Lovett in National Geographic Daily News: Mountain glaciers long have been known to be in retreat as the planet warms. But the process is occurring even more rapidly than previously believed, scientists said earlier this month in San Francisco at a meeting of the American Geophysical Union.

For example, said Garry Clarke, professor emeritus of glaciology at the University of British Columbia in Vancouver, Canada, the massive glaciers of Canada's Saint Elias region, now comprised of nearly 98 cubic miles of ice (453 cubic kilometers), are likely to be cut in half by 2100, even under middle-of-the-road climate-change scenarios. "[And] that's the good news," Clarke said.

In parts of the Canadian Rockies, he said, today's glaciers will all but disappear completely, while others will shrink to remnants just 5 to 20 percent of their current size. "We think that we will be witness over the next century mainly to the disappearance of the glaciers of western North America," he said.

Other disturbing finds are coming from the Himalayas, where Ulyana Horodyskyj, a graduate student at the University of Colorado's Cooperative Institute for Research in Environmental Sciences, has been monitoring supraglacial lakes—ponds of water that appear on the surface of melting glaciers.

"Most people think about glaciers receding," she said, "but they also shrink vertically. These lakes can lead to enhanced melting, and we see a lot of them forming throughout the Himalayas ... You can think of these lakes as cancers that are consuming the glacier."....

National Park Service photo of Hidden Lake in Glacier National Park in Montana

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