Arctic literally on thin ice, points out new evidenceApril 7th, 2009 - 11:55 am ICT by ANI
Washington, April 7 (ANI): New evidence from NASA and satellite observations has shown that the decade-long trend of shrinking sea ice cover in the Arctic is continuing, with the ice cap thinning as well.
In recent years, Arctic sea ice has been declining at a surprising rate.
Scientists who track Arctic sea ice cover from space have announced that this winter had the fifth lowest maximum ice extent on record.
The six lowest maximum events since satellite monitoring began in 1979 have all occurred in the past six years (2004-2009).
Until recently, the majority of Arctic sea ice survived at least one summer and often several. But, things have changed dramatically, according to a team of University of Colorado, Boulder, scientists led by Charles Fowler.
Thin seasonal ice that melts and re-freezes every year makes up about 70 percent of the Arctic sea ice in wintertime, up from 40 to 50 percent in the 1980s and 1990s.
Thicker ice, which survives two or more years, now comprises just 10 percent of wintertime ice cover, down from 30 to 40 percent.
According to researchers from the National Snow and Ice Data Center in Boulder, Colorado, the maximum sea ice extent for 2008-09, reached on Feb. 28, was 5.85 million square miles.
That is 278,000 square miles less than the average extent for 1979 to 2000.
“Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it grows more vulnerable to melting in the summer,” said Walter Meier, research scientist at the center and the University of Colorado, Boulder.
Last year, a team of researchers led by Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, California, produced the first map of sea ice thickness over the entire Arctic basin.
They found that the average winter volume of Arctic sea ice contained enough water to fill Lake Michigan and Lake Superior combined.
The older, thicker sea ice is declining and is being replaced with newer, thinner ice that is more vulnerable to summer melt, according to Kwok.
His team found that seasonal sea ice averages about 6 feet in thickness, while ice that had lasted through more than one summer averages about 9 feet, though it can grow much thicker in some locations near the coast. (ANI)
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