Greenland’s surface ice cover experienced a broader thaw during a three-day period this month than in nearly four decades of satellite record-keeping, according to three independent satellite measurements analyzed by NASA and university scientists.

About half of the surface of Greenland’s ice sheet melts on average each summer. But between July 11 and 13, roughly 97 percent of the the sheet — from its coastal edges to its 2-mile-thick center — experienced some thawing.

The unusual amount of melt — coming on the heels of the Petermann glacier’s loss of ice last week — has highlighted the extent to which warming temperatures are affecting the Arctic. There has been an unusually strong ridge of warm air, or a heat dome, over Greenland...

...Dartmouth College professor Kaitlin Keegan [error: Keegan is a Ph.D. candidate working with professors Mary Albert and Ian Baker], who has sampled ice cores taken from Summit Station in central Greenland, which is near the highest point of the ice sheet, said ice core samples indicate such pronounced melting at Summit and across the ice sheet has not occurred since 1889.