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Greenland again sees widespread melt

Just a week after scientists reported with alarm that 97 percent of Greenland had seen ice melting on the surface in mid-July, new data shows that after a brief refreeze much of the massive ice sheet has again seen melt.

Temperatures again warmed above freezing at key points between July 24-31, according to data provided to NBC News by Konrad Steffen, director of the Swiss Federal Institute for Forest, Snow and Landscape Research.

Thomas Mote, a climatologist at the University of Georgia at Athens, added that satellite imagery showed that the week peaked on Saturday with 74 percent of the giant ice sheet seeing melt. 

Typically, about a quarter of the ice sheet has melt on any given day in July, he noted.

"This event was almost as impressive as earlier this month, but didn't have quite as much melt in the north and northwest," Mote told NBC News.

"The big issue is simply the total amount of melt going on this summer, as opposed to any one day," he said. "Overall, we've had much earlier-than-normal and more extensive melting on Greenland this summer."

Like the mid-July melt, this one coincided with an "impressive ridge" of warm air sitting over Greenland, Mote noted.

Related story: 97 percent of Greenland sees ice melt

Mote said he's anxious to see satellite data at the end of summer showing any change to Greenland's total ice mass. "I would expect a very large loss of mass from the ice sheet this summer," he said.

Greenland ice cores do reveal that such thaws have happened every 150 years or so, but the fear now is that it might occur much more frequently due to warming sea and air temperatures. 

"If we continue to observe melting events like this in upcoming years, it will be worrisome," NASA glaciologist Lora Koenig said last week when the first data were released.

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