The reduction in multiyear ice—commonly defined as ice that has survived for two summers—is so noticeable compared with previous editions that National Geographic Geographer Juan José Valdés calls it "the biggest visible change other than the breakup of the U.S.S.R."
As the ocean heats up due to global warming, Arctic sea ice has been locked in a downward spiral. Since the late 1970s, the ice has retreated by 12 percent per decade, worsening after 2007, according to NASA. May 2014 represented the third lowest extent of sea ice during that month in the satellite record, according to the National Snow and Ice Data Center (NSIDC).
Ice loss is accelerated in the Arctic because of a phenomenon known
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