Satellite images have shown melting over 97 percent of the surface of Greenland's ice sheet in just four days, an event thought to occur every 150 years on average.
Greenland ice, it seems, can vanish in a flash, with new satellite images showing that over just a few days this month nearly all of the veneer of surface ice atop the island's massive ice sheet had thawed.
The images, snapped by three satellites, showed that about 40 percent of the ice sheet had thawed at or near the surface on July 8; just days later, on July 12, images showed a dramatic increase in melting with thawing across 97 percent of the ice sheet surface.
"This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?" said Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., referring to the July 12 images taken by the Indian Space Research Organisation's (ISRO) Oceansat-2 satellite.
Nghiem had reason to be baffled, as this record ice-melt is well above average: About half of Greenland's surface ice tends to melt every summer, with the meltwater at higher elevations quickly refreezing in place and the coastal meltwater either pooling on top of the ice or draining into the sea. [Giant Ice: Photos of Greenland's Glaciers]