Warmer Temps Chip Ice off Antarctic Block

Antarctica's ice shelves are melting away as temperatures climb, possibly as a result of global warming, British scientists said Wednesday.

At least five of the thick ice shelves that make up much of what is considered Antarctica have retreated dramatically over the past 50 years, David Vaughan and colleagues at the British Antarctic Survey in Cambridge said. ''Ice-shelf retreat has occurred on both coasts of the Antarctic Peninsula,'' they wrote in the science journal Nature.

Noting that a huge chunk of ice fell off the Larsen Ice Shelf a year ago - 500 square miles ''calved'' into the sea - they said the decay of the ice sheets coincided with a steady rise in temperatures in Antarctica.

''Meteorological records along the west coast of the Antarctic Peninsula show a ... consistent warming trend. At Faraday Station, a warming of 0.12 degree F a year has been measured since 1945, a total of about 4.2 degrees F,'' they wrote. ''We conclude that ice shelf extent may well be a sensitive indicator of regional climate change.''

The scientists said it was not clear whether the disappearance of the ice shelves was part of a natural cycle.

''We have still ... to determine the precise mechanisms whereby the atmospheric warming had such a catastrophic effect on the ice shelves of the Antarctic Peninsula but it is clear that ice shelves cannot survive periods of warming that last more than a few decades,'' they said.