On Sunday, September 16, the sun did not rise above the horizon in the Arctic. Nevertheless enough of the sun’s heat had poured over the North Pole during the summer months to cause the largest loss of Arctic sea ice cover since satellite records began in the 1970s. The record low 3.41 million square kilometers of ice shattered the previous low—4.17 million square kilometers—set in 2007. All told, since 1979, the Arctic sea ice minimum extent has shrunk by more than 50 percent—and even greater amounts of ice have been lost in the corresponding thinning of the ice, according to the U.S. National Snow and Ice Data Center (NSIDC).
“There is much more open ocean than there used to be,” says NSIDC research scientist Walt Meier. “The volume is decreasing even faster than the extent [of surface area] as best as we can tell,” based on new satellite measurements and thickness estimates provided by submarines. Once sea ice becomes thin enough, most or all of it may melt in a single summer.