Science & Technology

Satellites Confirm Extensive Ice Sheet Melt in Greenland

Extent of floor soften over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012 (proper). Measurements from three satellites confirmed that on July 8, about 40 p.c of the ice sheet had undergone thawing at or close to the floor. In only a few days, the melting had dramatically accelerated and an estimated 97 p.c of the ice sheet floor had thawed by July 12. Within the picture, the areas categorized as “possible soften” (mild pink) correspond to these websites the place no less than one satellite tv for pc detected floor melting. The areas categorized as “soften” (darkish pink) correspond to websites the place two or three satellites detected floor melting. Picture credit score: Jesse Allen, NASA Earth Observatory and Nicolo E. DiGirolamo, SSAI and Cryospheric Sciences Laboratory

Utilizing knowledge from three impartial satellites to research the extent of floor soften over Greenland’s ice sheet, NASA and college scientists discovered that ice melting at or close to the floor jumped dramatically this 12 months with an estimated 97 p.c of the ice sheet floor thawed sooner or later in mid-July.

Pasadena, California – For a number of days this month, Greenland’s floor ice cowl melted over a bigger space than at any time in greater than 30 years of satellite tv for pc observations. Almost the whole ice cowl of Greenland, from its skinny, low-lying coastal edges to its 2-mile-thick (3.2-kilometer) heart, skilled a point of melting at its floor, in response to measurements from three impartial satellites analyzed by NASA and college scientists.

On common in the summer season, about half of the floor of Greenland’s ice sheet naturally melts. At excessive elevations, most of that soften water rapidly refreezes in place. Close to the coast, a number of the soften water is retained by the ice sheet, and the remainder is misplaced to the ocean. However this 12 months the extent of ice melting at or close to the floor jumped dramatically. In keeping with satellite tv for pc knowledge, an estimated 97 p.c of the ice sheet floor thawed sooner or later in mid-July.

Researchers haven’t but decided whether or not this in depth soften occasion will have an effect on the general quantity of ice loss this summer season and contribute to sea degree rise.

“The Greenland ice sheet is an unlimited space with a diversified historical past of change. This occasion, mixed with different pure however unusual phenomena, akin to the big calving occasion final week on Petermann Glacier, are a part of a fancy story,” mentioned Tom Wagner, NASA’s cryosphere program supervisor in Washington. “Satellite tv for pc observations are serving to us perceive how occasions like these could relate to at least one one other in addition to to the broader local weather system.”

Son Nghiem of NASA’s Jet Propulsion Laboratory in Pasadena, California was analyzing radar knowledge from the Indian House Analysis Organisation’s (ISRO) Oceansat-2 satellite tv for pc final week when he observed that the majority of Greenland appeared to have undergone floor melting on July 12. Nghiem mentioned, “This was so extraordinary that initially I questioned the outcome: was this actual or was it due to a knowledge error?”

Nghiem consulted with Dorothy Corridor at NASA’s Goddard House Flight Middle in Greenbelt, Maryland Corridor research the floor temperature of Greenland utilizing the Reasonable-resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites. She confirmed that MODIS confirmed unusually excessive temperatures and that soften was in depth over the ice sheet floor.

Thomas Mote, a climatologist on the College of Georgia, Athens; and Marco Tedesco of Metropolis College of New York additionally confirmed the soften seen by Oceansat-2 and MODIS with passive-microwave satellite tv for pc knowledge from the Particular Sensor Microwave Imager/Sounder on a U.S. Air Drive meteorological satellite tv for pc.

The melting unfold rapidly. Melt maps derived from the three satellites confirmed that on July 8, about 40 p.c of the ice sheet’s floor had melted. By July 12, 97 p.c had melted.

This excessive soften occasion coincided with an unusually robust ridge of heat air, or a warmth dome, over Greenland. The ridge was one in all a sequence that has dominated Greenland’s climate for the reason that finish of Might. “Every successive ridge has been stronger than the earlier one,” mentioned Mote. This newest warmth dome began to maneuver over Greenland on July 8, after which parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate.

Even the realm round Summit Station in central Greenland, which at 2 miles (3.2 kilometers) above sea degree is close to the best level of the ice sheet, confirmed indicators of melting. Such pronounced melting at Summit and throughout the ice sheet has not occurred since 1889, in response to ice cores analyzed by Kaitlin Keegan at Dartmouth Faculty in Hanover, New Hampshire A Nationwide Oceanic and Atmospheric Administration climate station at Summit confirmed air temperatures hovered above or inside a level of freezing for a number of hours July 11 to 12.

“Ice cores from Summit present that melting occasions of this kind happen about as soon as each 150 years on common. With the final one occurring in 1889, this occasion is true on time,” mentioned Lora Koenig, a Goddard glaciologist and a member of the analysis staff analyzing the satellite tv for pc knowledge. “But when we proceed to watch melting occasions like this in upcoming years, it is going to be worrisome.”

Nghiem’s discovering whereas analyzing Oceansat-2 knowledge was the type of profit that NASA and ISRO had hoped to stimulate after they signed an settlement in March 2012 to cooperate on Oceansat-2 by sharing knowledge.

Picture: Jesse Allen, NASA Earth Observatory and Nicolo E. DiGirolamo, SSAI and Cryospheric Sciences Laboratory

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