Huge Antarctic Glacier
Melting Fast - Trigger
Mass Ice Disintegration?
From Discovery Channel Online
A huge Antarctic glacier is beating a hasty retreat from the ocean, and its movement could trigger the disintegration of an expanse of ice the size of about half of the United States.
In the current issue of the journal Science, Eric Rignot, of NASA's Jet Propulsion Laboratory, reports that between 1992 and 1996, about three miles of the Pine Island Glacier on the West Antarctic Ice Sheet has melted -- disappearing at a more rapid rate than scientists had expected.
Such a rapid retreat could "theoretically" decompose the vast West Antarctic Ice Sheet eventually, says Rignot, raising sea levels and flooding low lying areas around the world.
Much of the glacier extends deep into relatively warm Pacific waters, making it particularly sensitive to temperature changes, according to oceanographer Stan Jacobs of Columbia University's Lamont Dogherty Earth Observatory.
But understanding ice in the Antarctic can be extremely puzzling. The more scientists learn about glaciers "the more we find they are behaving erratically, spasmodically, with different things happening in different parts and at different times," says Cha rles Bentley, a geologist at the University of Wisconsin-Madison.
Using the same technique as Rignot, Mark Stenoien reports in his just-completed doctoral dissertation at the University of Wisconsin-Madison that the upper 125 miles (200 kilometers) of the Pine Island Glacier is stable.
Large shelves of ice just north of Pine Island were not there 500 years ago, reports Eugene Domack, a marine geologist at Hamilton College.
What's more, the entire West Antarctic Ice Sheet has been receding for the past 10,000 years, according to NASA glaciologist Robert Bindschadler.
"In that 10,000 years it has lost twice its present volume. It has contributed 10 meters to sea level over 10,000 years," says Bindschadler.
Consequently, the meaning of the retreat of the Pine Island Glacier is not clear, says Rignot. He and others emphasize the recession has occurred over an extraordinarily short time -- four years -- so deciding if it's the result of human-caused climate ch ange or much more enduring geological and oceanographic phenomena is impossible right now.
More study is needed, he says. But "we have a blinking light," he notes -- an indication that something significant may be happening.
By Harvey Black, Discovery Channel Online News
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