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Ice melt in the summer is a normal phenomenon: As summer temperatures heat up the Northern Hemisphere, Arctic sea ice begins to melt, and its edge retreats and covers less of the North polar region. When temperatures begin to drop again in the winter, the ice reforms. But in recent years, rising air and ocean temperatures, fueled by global warming, have caused more and more ice to melt each summer, with ice extent reaching a record low on Sept. 16 this year, according to the University of Colorado at Boulder's National Snow and Ice Data Center (NSIDC). Winter sea ice, on the other hand, had remained fairly steady—until now.
A new study examining satellite measurements of the winter sea ice covering the Barents Sea (located north of Scandinavia) over the past 26 years has shown that the ice edge has recently been retreating in the face of rising sea surface temperatures, said study leader Jennifer Francis of Rutgers University.
Her research, detailed in a recent issue of the journal Geophysical Research Letters, showed that the warming waters in the Barents Sea—which have risen about 3 degrees Celsius since 1980—are to blame for the reduction in winter ice cover. Two factors contribute to the warming of the Barents Sea: warming Atlantic waters funneled in by the Gulf Stream and solar heating of the open ocean as ice melts in the summer, both of which make it harder for new ice to form in the winter.
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In another study that came out earlier this year, Stroeve compared current measurements of sea ice melt with the predictions of the Intergovernmental Panel on Climate Change's models—and what she found gave her cause for worry. "We're about 30 years ahead of where the climate models say we should be," Stroeve told LiveScience. Stroeve, Francis and others will be keeping a close eye on the sea ice this winter, as the new record summer low may mean a record low winter ice extent this year as well, thanks to the ice-albedo feedback. Francis and Stroeve both say that an unusually cold summer or winter in the future could pump ice levels back up, but they aren't optimistic that the ice will ever return to historic levels. "It's hard to imagine seeing it turned around," Francis said.
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