(July 25, 2012) For several days this month, Greenland's surface ice cover melted over
a larger area than at any time in more than 30 years of satellite observations.
Nearly the entire ice cover of Greenland, from its thin, low-lying coastal
edges to its 2-mile-thick (3.2-kilometer) center, experienced some degree of
melting at its surface, according to measurements from three independent
satellites analyzed by NASA and university scientists.
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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.
Researchers have not yet
determined whether this extensive melt event will affect the overall volume of
ice loss this summer and contribute to sea level rise.
"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."