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Antarctic melting goes deep.

A study in the October 31 issue of Science offers new clues to the connection between rising temperatures on the Antarctic Peninsula and the collapse of that continent's massive ice shelves. The authors suggest that the recent disintegration of two large sections of the Larsen Ice Shelf, known as Larsen A and Larsen B, were the result not just of increased melting on the surface of the ice (which is thought to speed the formation of cracks), but also of accelerated loss from the shelf's base. According to the report, this basal ice melting--caused by warming ocean waters--is thinning the shelf by as much as 78 centimeters annually.

Satellite imagery indicates that the Antarctic Peninsula's ice shelves have retreated by roughly 300 square kilometers a year since 1980. The Larsen collapses were among the largest: the 2,000 square kilometer Larsen A crumbled over a period of days in January 1995, while the 3,250 square kilometer Larsen B (the rest of the shelf's northern section) collapsed in February 2002. Scientists have attributed these events to rising temperatures because of the nature of the collapses: rather than clean breaks, or "calvings," of the shelf into large icebergs, which is believed to occur in natural cycles, both shelves rapidly disintegrated within a span of seven years, suggesting a wholesale weakening.

Andrew Shepherd, a researcher at Cambridge University's Scott Polar Research Center and co-author of the Science study, suggests that changing ocean temperatures in the surrounding area should be monitored closely and considered in any future assessments of climate change in the region. "The previously undetected basal ice melting may provide a simple link between the regional climate warming and the successive disintegration of Larsen ice shelf sections," he notes.
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Title Annotation:Environmental Intelligence
Author:Mastny, Lisa
Publication:World Watch
Date:Mar 1, 2004
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