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Global warming sign? Huge Arctic glacier is cracking

SCIENCE FILE

August 23, 2008|Seth Borenstein | Associated Press

In northern Greenland, a part of the Arctic that had seemed immune from global warming, new satellite images show a growing giant crack and an 11-square-mile chunk of ice hemorrhaging off a major glacier, scientists said Thursday.

That has led the university professor who spotted the wounds in the massive Petermann glacier to predict disintegration of a major portion of the Northern Hemisphere's largest floating glacier within the year.

The crack is 7 miles long and about half a mile wide. It is about half the width of the 500-square-mile floating part of the glacier. Other smaller fractures can be seen in images of the ice tongue, a long narrow sliver of the glacier.

"The pictures speak for themselves," said Jason Box, a glacier expert at the Byrd Polar Research Center at Ohio State University who spotted the changes while studying new satellite images.

"This crack is moving, and moving closer and closer to the front. It's just a matter of time till a much larger piece is going to break off."

The chunk that came off the glacier between July 10 and July 24 is about half the size of Manhattan and doesn't worry Box as much as the cracks. The Petermann glacier had a larger breakaway ice chunk in 2000.

"As we see this phenomenon occurring further and further north -- and Petermann is as far north as you can get -- it certainly adds to the concern," said Waleed Abdalati, director of the Center for the Study of Earth From Space at the University of Colorado.

The question that now faces scientists is: Are the fractures part of normal glacier stress or are they the beginning of the effects of global warming?

"It certainly is a major event," said NASA ice scientist Jay Zwally in a telephone interview from a conference on glaciers in Ireland. "It's a signal, but we don't know what it means."

University of Colorado professor Konrad Steffen, who returned from Greenland on Wednesday and has studied the Petermann glacier in the past, said that what Box saw was not too different from what he saw in the 1990s: "The crack is not alarming. . . . I would say it is normal."

However, scientists note that it fits with the trend of melting glacial ice they first saw in the southern part of the massive island and seems to be marching north with time.

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