The Arctic Sea's ice cover melted more this year than has ever been recorded by satellites, according to the National Snow and Ice Data Center, breaking the previous low observed in 2007.
On September 16, the sea ice covering the North Pole receded to 1.32 million square miles, 18 percent lower than the previous record low of 1.61 million square miles, recorded on September 18, 2007.
Mark Serreze, director of the center, said the development puts the world in "uncharted territory."
"Few of us were prepared for how rapidly the changes would actually occur," he said in a statement.
Though the ice cover suffered record melting, it's likely done for the summer, and sea ice is likely to refreeze over the winter. Scientists at the center said that late-season ice melt that occurred this month is particularly troubling, because it indicates that the ice layer is thinner and more fragile than previously thought. According to Walt Meier, a scientist with the National Snow and Ice Data Center, parts of the Arctic that were once covered with ice for years at a time are now undergoing seasonal melting and refreezing during the winter.
In July, an "astonishing" heat wave melted nearly all of the ice covering Greenland. NASA scientist Waleed Abdalati said that melt "makes you wonder what's going on." Though much of that ice sheet has refrozen, scientists won't know the full impact of the Greenland melt until further into the winter.
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According to the center, this year's Arctic ice low point was almost 50 percent lower than the averages between 1979 and 2000. Some predictions by the center suggest that by 2050, summers in the Arctic Ocean may be entirely ice free, which could have major impacts on worldwide weather. But scientists at the center say that during recent summers, including this one, actual ice melt has outpaced predictions.
"This will gradually affect climate in areas where we live," NSIDC lead scientist Ted Scambos said in a statement. "We have a less polar pole, so there will be more variations and extremes."
Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at firstname.lastname@example.org