Huge Antarctic ice chunk collapses

WASHINGTON (AP) -- A chunk of Antarctic ice about seven times the size of Manhattan suddenly collapsed, putting an even greater portion of glacial ice at risk, scientists said Tuesday.

Satellite images show the runaway disintegration of a 160-square-mile chunk in western Antarctica, which started February 28. It was the edge of the Wilkins ice shelf and has been there for hundreds, maybe 1,500 years.

This is the result of global warming, said British Antarctic Survey scientist David Vaughan.

Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the ongoing collapse for rare pictures and video.

"It's an event we don't get to see very often," said Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. "The cracks fill with water and slice off and topple... That gets to be a runaway situation."

While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades, Vaughan said. The collapse is similar to what happens to hardened glass when it is smashed with a hammer, he said.

The rest of the Wilkins ice shelf, which is about the size of Connecticut, is holding on by a narrow beam of thin ice. Scientists worry that it too may collapse. Larger, more dramatic ice collapses occurred in 2002 and 1995.

Vaughan had predicted the Wilkins shelf would collapse about 15 years from now.

Scientists said they are not concerned about a rise in sea level from the latest event in Antarctica, but say it's a sign of worsening global warming.

Such occurrences are "more indicative of a tipping point or trigger in the climate system," said Sarah Das, a scientist at the Woods Hole Oceanographic Institute. E-mail to a friend

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