NASA satellite images showed the extent of surface melt on Greenland's ice sheet on July 8 (L) and July 12 (R). Measurements showed that on July 8 about 40% of the ice sheet had undergone thawing at or near the surface. By July 12, an estimated 97% of the ice sheet surface had thawed.
This month, over a rapid four day period, the ice sheet that covers Greenland melted more than it ever has in the last 30 years, NASA reported.
Each summer about half the ice sheet naturally melts before refreezing or running off into the ocean, but in the last few days the melt has impacted an estimated 97% of the ice sheet, according to satellite data.
Scientists are not yet sure how this rapid melt—jumping from 40% ice sheet melt to 97% melt in four days—will affect the summer's total ice sheet loss or sea levels.
Unusually strong warm air, also known as a heat dome, has engulfed Greenland since May before beginning to dissipate July 16, NASA said in a statement regarding the images.
Time spoke to NASA's chief scientist Waleed Abdalati who said this kind of melt "makes you sit up and ask what's happening."
"It's a big signal, the meaning of which we're going to sort out for years to come," he continued.
About the same time, a giant iceberg broke off from the Petermann Glacier in northern Greenland. And the National Snow and Ice Data Center on Tuesday announced that the area filled with Arctic sea ice continues near a record low.
Wagner and other scientists said because this Greenland-wide melting has happened before they can't yet determine if this is a natural rare event or one triggered by man-made global warming. But they do know that the edges of Greenland's ice sheets have already been thinning because of climate change.