PHOTOS: Jamaica-Size Ice Shelf Breaks Free

Antarctic ice shelf pictures
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April 6, 2009—An "alarming rate" of melting in the Antarctic Peninsula has finally snapped the ice bridge that held the Wilkins Ice Shelf in place, experts say.

The 25-mile-long (40-kilometer-long) ribbon of sea ice that secured the Jamaica-size ice shelf (which is just out of view in the above pictures) to Antarctica had been "hanging by a thread" since August 2008 (above, top, in November 2008 in a European Space Agency satellite image).

On Saturday, April 4, the bridge broke at its weakest point (bottom)—at about 1,640 feet (500 meters) wide—and shattered into hundreds of small icebergs. The ice shelf, which is now exposed to the open ocean, is more vulnerable to breaking up, experts say.

"We've been watching it all summer, waiting for it to go, and bang—now it's gone," David Vaughan, a glaciologist for the British Antarctic Survey, told National Geographic News.

"It's the culmination of yet another ice shelf retreat that's been driven by [warming] climate," Vaughan said.

The Antarctic Peninsula has warmed 3 degrees Celsius (5.4 degrees Fahrenheit) since the 1950s, he said—"something that people should take note of."

(Related: "Antarctica Heating Up, 'Ignored' Satellite Data Show".)

The massive ice shelf had been stable for most of the past century until it began disintegrating in the 1990s.

Vaughan and colleagues will take sediment cores from Wilkins' newly exposed seabeds to find out whether such dramatic breakups have occurred in the shelf's past.

But previous research on another Antarctic ice shelf suggests that the giant ledges do not change much over the centuries.

"I wouldn't be at all surprised to find that Wilkins is similar," Vaughan said. "If it has been there [unchanged for] 10,000 years, this is a pretty significant event."

—Christine Dell'Amore

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