An ice shelf in Antarctica the size of Scotland is rapidly disintegrating because of warmer seas, scientists said yesterday. They believe that the Larsen ice shelf on the Antarctic peninsula may disappear within 70 years.

This photo released by Greenpeace shows a crack in the Larsen B ice shelf in the Wedden sea, in Antarctica. (AFP/EPA/File)

Although the ice shelf will not raise sea levels - it is already floating on the ocean - scientists say that its loss may trigger a release of ice from the peninsula's mainland, causing global sea levels to rise by 1 meter (3ft 3in).

Researchers led by Andrew Shepherd, a glaciologist from Cambridge University, found that the Larsen ice shelf had thinned by as much as 18 meters in the past 10 years. That can only be explained by a warmer ocean, he said.

The study is published in the journal Science a day after a study revealed that the ice in the Arctic was melting rapidly due to a rise in temperatures, threatening the natural habitat of the polar bear.

Both studies used radar measurements taken by the European Space Agency's ERS-1 and ERS-2 satellites. This enabled the scientists to monitor the loss of ice over huge areas of sea at opposite ends of the Earth for 10 years.

Dr Shepherd said: "We've discovered that the Larsen ice shelf is thinning due to warmer oceans around it."

The radar measurements of the ice shelf's average height above the sea, which are accurate to within 20cm, revealed a pattern of thinning since measurements began in 1992, Dr Shepherd said.

The amount of melting freshwater running off the ice shelf into the surrounding sea was equivalent to eight times the flow of the river Thames. This could disturb the local sea currents that were part of a much wider global ocean circulation, he said. Dr Shepherd said that it was not possible to say with certainty whether global warming was directly responsible for the melting. However, he said that it was indisputable that the sea around the Antarctic peninsula was getting warmer - although other parts of the Antarctic continent were getting colder.

Dr Shepherd said the Larsen ice shelf was about 300 meters thick. When two previous sections of the shelf thinned to about 200 meters they quickly disintegrated.

Current estimates suggested that the Larsen ice shelf would begin to disintegrate rapidly by about 2070, although that was likely to happen sooner if current warming trends continued, Dr Shepherd said.

The disappearance of the ice shelf might also affect the local ice sheets, large bodies of ice trapped on land by the ice shelf. "This is a really important indicator of how grounded ice behind will respond to this disintegration," Dr Shepherd said.

Much bigger ice shelves in Antarctica are also being monitored. The Ronne and the Ross ice shelves are about 10 times the size of the Larsen ice shelf and their disintegration would be a far more serious event. Scientists estimate that the Larsen ice shelf has been in existence for 2,000 years and took many centuries to form.

© 2003 Independent Digital (UK) Ltd

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