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NASA: Arctic sea ice hit its fourth lowest level on record

NASA says that an analysis of satellite data shows that the amount of late-summer Arctic sea ice is at its fourth lowest point on record.

The Arctic sea ice cover is frozen seawater that reflects solar energy back to space, helping keep the Earth cool. It gets smaller or larger depending on the season, and its minimum summertime extent occurs at the end of the melt season; NASA says the late-summer minimum size has been decreasing since the late 1970s due to warming temperatures. Analysis by NASA and the NASA-supported National Snow and Ice Data Center shows that on Sept. 11, the annual minimum extent was 1.70 million square miles, 699,000 square miles lower than the 1981-2010 average.

"This year is the fourth lowest, and yet we haven't seen any major weather event or persistent weather pattern in the Arctic this summer that helped push the extent lower, as often happens," Walt Meier, a sea ice scientist with NASA's Goddard Space Flight Center, said in a statement. "It was a bit warmer in some areas than last year, but it was cooler in other places, too." Since 1996, the sea ice decline has accelerated, and Meier said the ice cover is becoming less and less resilient: "The sea ice cap, which used to be a solid sheet of ice, now is fragmented into smaller floes that are more exposed to warm ocean water. In the past, Arctic sea ice was like a fortress. The ocean could only attack it from the sides. Now it's like the invaders have tunneled in from underneath and the ice pack melts from within."

Next week, NASA's Operation IceBridge will carry out flights over the Arctic to gain insight into how the summer melt season will affect land and sea ice. Catherine Garcia