NEW YORK — The massive floating canopy of ice that covers the Arctic Ocean receded over a nine-year period, possibly reflecting the effects of global warming, researchers said.
The canopy, which at times is 70% larger than the United States, drew back about 2% between October, 1978, and August, 1987, researchers said.
But scientists cautioned that they do not know enough yet to blame global warming, the expected consequence of a buildup in the atmosphere of heat-trapping gases.
Researchers will need 30 years of observation "before you can even think about saying anything definite about the climate," study co-author Per Gloersen said.
Gloersen is a physicist in the oceans and ice branch of the National Aeronautics and Space Administration Goddard Space Flight Center in Greenbelt, Md. The work appears in today's issue of the British journal Nature.
Researchers used satellite observations to track the extent of Arctic and Antarctic sea ice over the nine-year period. The Arctic sea-ice canopy is a collection of many small ice chunks, often connected by thin ice, that fills the Arctic Ocean and spreads into the Bering Sea, Baffin Bay and other nearby bodies of water in winter. In summer, it retreats to within the Arctic Ocean, Gloersen said.
No significant changes were observed in the Antarctic ice cover. The researchers said they did not know why but that one computer simulation of global warming suggests the Arctic would warm quickly and the Antarctic slowly.