Nov. 10, 2002

Scientists report that the amount of ice melting from the surface of the Greenland Ice Sheet this year broke all known records and that Arctic sea ice in 2002 reached the lowest level in the satellite record.

A December 7 press release says scientists at the Colorado University-based Cooperative Institute for Research in Environmental Sciences report that the accelerated melting appears to be linked to shifts in Northern Hemisphere atmospheric circulation patterns. The study also found that temperatures during the summer of 2002 were unusually warm over much of the Arctic Ocean.

It is believed that sea-ice in the Arctic in 2002 is at the lowest since the early 1950s and possibly the lowest in several centuries. Satellite monitoring led to the discovery of the record sea-ice retreat.

The researchers believe a combination of warm temperatures and a season characterized by very stormy conditions probably contributed to the extensive melting and breakup of the icepack.

"It is likely that sea ice extent will continue to decline over the 21st century as the climate warms," said Research Associate Mark Serreze, lead author of the study, which was presented at a meeting of the American Geophysical Union held December 6-10 in San Francisco. "With these trends, we may see an approximate 20-percent reduction in the annual mean sea ice by 2050, and by then we might be approaching no ice at all during the summer months."

Colorado University scientists estimate that a warming in the Greenland climate would lead to an increase in the rate of sea-level rise, mainly due to the dynamic response of the large Greenland ice sheet and not so much to the surface melting. "Melt water has been shown to directly affect the rate of ice flow off Greenland, penetrating the ice sheet and causing the glaciers to accelerate in speed as they slide over a thin film of melt water," the release says.

Serreze said that accelerated melting of sea ice, along with runoff from the Greenland Ice Sheet, also has the potential to "cap" deep water convection in the North Atlantic, which could profoundly impact global ocean circulation and climate. "In other studies, changes in the North Atlantic circulation have been implicated in starting and stopping Northern Hemisphere ice ages," he added.