Arctic sea ice melts by almost a half

Scientists have detected a significant reduction in the thickness of the Arctic sea ice, which they say is related to global warming. Over the past 20 to 40 years the ice has lost up to 40 per cent of its depth right across the Arctic at 29 sites monitored by nuclear submarines.

Scientists have detected a significant reduction in the thickness of the Arctic sea ice, which they say is related to global warming. Over the past 20 to 40 years the ice has lost up to 40 per cent of its depth right across the Arctic at 29 sites monitored by nuclear submarines.

Andrew Rothrock, the scientist at the University of Washington in Seattle who led the investigations, will report in next month's Geophysical Research Letters that the average ice thickness has declined by 4.3 feet since 1958. "The decrease in sea ice occurs all across the Arctic Ocean and corresponds to previously reported evidence that the Arctic climate is warming," said the American Geophysical Union, which publishes the journal.

The scientists used radar data on sea ice draught - the depth between the ocean's surface and the bottom of the floating ice pack - gathered during the autumn cruises of three US submarines in 1993, 1996 and 1997. These were compared with measurements taken in 1958 and 1976.

Dr Rothrock said the reduction was "striking". Each of the 29 sites has shown a fall in ice thickness. In the Nansen Basin in the eastern Arctic, the thinning is more than 5.5 feet; in others it is nearer three feet. The scientists say it might result from an increase in the flow of heat from the ocean or from the heating of the atmosphere.

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