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Some Antarctic Glaciers Shrinking

The first comprehensive survey of glaciers on the Antarctic Peninsula has shown that the rivers of ice are shrinking, mostly because of warming of the local climate.

It is unclear, however, whether the increased temperature causing the shrinkage is a natural regional effect or a result of global warming, said the scientists who conducted the study, published this week in the journal Science.

Researchers from the British Antarctic Survey and the U.S. Geological Survey analyzed more than 2,000 aerial photographs dating from 1940 and more than 100 satellite images from the 1960s onwards.

They calculated that 87 percent of the 244 glaciers going out to sea from the peninsula have retreated during the last 50 years and that the pace of shrinkage has accelerated in the last decade. Until now, scientists were uncertain whether the glaciers were growing or melting.

"Fifty years ago, most of the glaciers we look at were slowly growing in length but since then this pattern has reversed. In the last five years the majority were actually shrinking rapidly," said the study's leader, Alison Cook of the British Antarctic Survey.

"However, 32 glaciers go against the trend and are showing minor advance. Had we not studied such a large number of glaciers we may have missed the overall pattern."

The Antarctic peninsula is a small segment of the Antarctic continent, located at the South Pole, and the behavior of the ice on the peninsula is not necessarily a reflection of what's going on elsewhere in Antarctica, said another investigator, David Vaughan of the British Antarctic Survey.

Temperatures seem to be much warmer on the Antarctic peninsula than on the rest of the continent.

Evidence from the main Antarctic ice sheet is mixed, with some areas of the continent showing shrinkage and others showing thickening.

Ice shrinkage has also been documented in Alaska and the North Pole.

Scientists worry about the melting of the ice sheets because the extra water may increase sea levels, which in turn could mean more flooding damage to coastal areas during storms.

Sea levels have risen by 4-8 inches over the last 100 years. However, the study was not able to tell whether the shrinkage is having a meaningful impact on sea levels.

It also is unclear whether changes in the larger ice sheet in Antarctica are contributing to a sea-level rise, Vaughan said.

"This is another piece in the jigsaw that tells us how climate change is affecting the planet. It may not be a significant piece, but there's a million-piece jigsaw out there to be filled in ... and this is one piece in it," Vaughan said.

By Emma Ross
By Emma Ross