- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- Large shelves of ice just north of Pine
Island were not there 500 years ago, reports Eugene Domack, a marine geologist
at Hamilton College.
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- What's more, the entire West Antarctic
Ice Sheet has been receding for the past 10,000 years, according to NASA
glaciologist Robert Bindschadler.
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- "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.
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- 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.
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- More study is needed, he says. But "we
have a blinking light," he notes -- an indication that something significant
may be happening.
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- By Harvey Black, Discovery Channel Online
News
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- For more News Briefs, and for Feature
Stories, Mind Games, and real-time Expeditions, visit Discovery Channel
Online at http://www.discovery.com
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