BOULDER, Colo., April 6 (UPI) -- The U.S. space agency says this winter had the fifth lowest maximum coverage of arctic ice on record.
The National Aeronautics and Space Administration and National Snow and Ice Data Center said the information came from recent satellite observations.
Arctic sea ice plays a key role in ocean circulation, the scientists said, and during recent years the sea ice has been declining at a surprising rate. The six lowest maximum events since satellite monitoring began in 1979 all occurred during the past six years (2004-2009).
Until recently, most arctic sea ice survived at least one summer and often several, the scientists said. But things have changed dramatically, say University of Colorado-Boulder researchers. The scientists said thin seasonal ice -- ice that melts and refreezes every year -- now makes up about 70 percent of the arctic sea ice during winter, up from 40 percent to 50 percent during the 1980s and 1990s.
Thicker ice, which survives two or more years, now comprises only 10 percent of wintertime arctic ice cover, down from 30 percent to 40 percent.
The researchers said maximum sea ice for the 2008-2009, winter on Feb. 28, was 5.85 million square miles. That's 278,000 square miles less than the average maximum for 1979 to 2000.