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Larsen B ice shelf breaks off from Antarctic Peninsula. (Environmental Intelligence).

Over a five-week period ending in March, an ice shelf 200 meters thick and bigger than Luxembourg broke off from the Antarctic Peninsula and fragmented, releasing approximately 720 million tons of floating ice into the Weddell Sea. Scientists estimate that the Larsen B ice shelf was at least 400 years old and may have even existed since the end of the last ice age 12,000 years ago.

The smaller, neighboring Larsen A shelf broke off in 1995, and scientists at the British Antarctic Survey predicted then that Larsen B would also eventually collapse. But the scale and speed of its breakup was "unprecedented," according to Ted Scambos, a glaciologist at the U.S.-based National Snow and Ice Data Center. The center called the demise of the Larsen B shelf "the largest single event in a 30- year series of ice shelf retreats in the peninsula."

Scambos and his colleagues theorize that the melted water collecting on the surface of ice shelves drains into cracks and causes fracturing, which can lead eventually to the shelves' disintegration. The Larsen B shelf's collapse came at the end of the warmest summer on record in the Antarctic peninsula, where average temperatures have risen by about 2.5 degrees C in the past 50 years. Scambos said that the shelf's breakup was related to "summertime melting and a warming trend" in the region but that it could not be directly attributed to global warming. "Linking the effects of greenhouse gases in the atmosphere to the specific events in the Antarctic is a real problem," he said, because global warming models are not yet sophisticated enough to explain climate patterns in Antarctica.

The loss of the Larsen B shelf has sharply altered the landscape of Antarctica, but it will not cause sea levels to rise because the ice was already floating.
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Author:Larson, Vanessa
Publication:World Watch
Article Type:Brief Article
Geographic Code:8ANTA
Date:Jul 1, 2002
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Next Article:E.U., U.S. pledge to increase development assistance. (Environmental Intelligence).

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