PASADENA, California -- NASA scientists say the ice covering almost all of Greenland experienced some melting this summer. It was an event "so extraordinary" that one scientist involved in the discovery at first questioned whether it was real.
Here is NASA's summary from a report issued today: "On average in the summer, about half of the surface of Greenland's ice
sheet naturally melts. At high elevations, most of that melt water
quickly refreezes in place. Near the coast, some of the melt water is
retained by the ice sheet and the rest is lost to the ocean. But this
year the extent of ice melting at or near the surface jumped
dramatically. According to satellite data, an estimated 97 percent of
the ice sheet surface thawed at some point in mid-July."
NASA says research Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., was analyzing radar data from the Indian Space Research Organisation's (ISRO) Oceansat-2 satellite last week when he noticed that surface melting appeared to have occurred over most of Greenland on July 12. According to NASA, Nghiem said, "This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?"
Extent of surface melt over Greenlandâs ice sheet on July 8 (top) and July 12 (bottom). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. In the image, the areas classified as "probable melt" (light pink) correspond to those sites where at least one satellite detected surface melting. The areas classified as "melt" (dark pink) correspond to sites where two or three satellites detected surface melting. The satellites are measuring different physical properties at different scales and are passing over Greenland at different times. As a whole, they provide a picture of an extreme melt event about which scientists are very confident. (Nicolo E. DiGirolamo, SSAI/NASA GSFC, Jesse Allen, NASA Earth Observatory)
Ngheim consulted with several other scientists who confirmed the data. NASA says researchers don't yet know if the melt will contribute to overall sea rise. They say say the melting "coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland."
"The Greenland ice sheet is a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story," said Tom Wagner, NASA's cryosphere program manager in Washington. "Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system."
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