Scientists analyzing decades of data from Arctic Sea ice recently reported a significant reduction in the thickness of the ice during the last decade. The scientists found a decrease in sea ice all across the Arctic Ocean and that corresponds to  previously reported evidence that the Arctic climate is warming, according to Dr. D. Andrew Rothrock of the University of
Washington and colleagues.

A report on the data, Thinning of the Arctic Sea-Ice Cover, will be published in the Dec. 1 issue of Geophysical Research Letters.

The Scientific Ice Expeditions program, which consisted of six extended voyages, acquired the data using nuclear submarines. This study analyzed data from three autumn cruises: USS Pargo in 1993, USS Pogy in 1996 and USS Archerfish in 1997.

The average draft of the sea ice (its thickness from the ocean surface to the bottom of the ice pack) has declined by 4.3 feet, or 40 percent, since the first measurements were made in 1958, said the scientists.

The thinning of Arctic ice that has already occurred is "a major climatic signal that needs to be accounted for in a successful
theory of climate variability," according to the scientists. To help fill the gaps between the earlier and more recent submarine observations, they call for the public release of other ice thickness data gathered by submarines over the past 40 years, which they believe would be "of immense help" in understanding the cause of thinning.

The available data are insufficient to provide answers about the cause of the ice loss, said the researchers. They suggest several hypotheses about the flow of heat from the ocean itself, the flow of heat from the atmosphere as well as from short-wave radiation. Other possible avenues to explore include the amount of precipitation and snow cover in the region and ice movement.