Perennial ice, sometimes thick enough to defy icebreakers, may be key to predicting arctic thaw

Environment News Network: Loss of sea ice that is more than a year old -- called perennial ice -- may be the key predictor for how much Arctic ice melts each summer, a University of Washington polar scientist says. He says the loss of perennial ice in the last two years led to this summer's record-breaking ice retreat.

A paper being published online today by Geophysical Research Letters, says perennial sea ice covering the Arctic Ocean decreased by 23 percent during the past two winters as strong winds swept more Arctic ice than usual out Fram Strait near Greenland. The study relied on 50 years of data from the International Arctic Buoy Program, currently directed by Ignatius Rigor of the UW's Applied Physics Laboratory, and eight years of data from NASA's QuikScat satellite, a review of which was led by Son Nghiem of NASA's Jet Propulsion Laboratory.

"The most important thing about this paper is that it foretells this summer's record minimum ice extent in the Arctic," Rigor, a research scientist and co-author on the paper, says. "While the total area of ice cover in recent winters has remained about the same, during the past two years an increased amount of older, thicker perennial sea ice was swept by winds out of the Arctic Ocean into the Greenland Sea. What grew in its place in the winters between 2005 and 2007 was a thin veneer of first-year sea ice, which simply has less mass to survive the summer melt."…