Temperatures W/I Greenland Ice Sheet Up By As Much As 10F Since 1950s; Test Site Snow Now Ice

In the mid-20th century, when Carl Benson was traveling Greenland gathering data he would use to write his Ph.D. thesis on the temperature, structure and composition of the hard-packed snow that covers that island, conditions deep beneath the surface were fairly consistent: white, firm, cold and dry. “If you could imagine cutting a wall of Styrofoam, that’s what it was like,” said Benson, now a professor emeritus with the University of Alaska Fairbanks’ Geophysical Institute.

Six decades later, researchers who revisited several of Benson’s test sites on the Greenland ice sheet found something different. Measurements taken in that 2013 expedition found temperatures below the surface had warmed by as much as 10 degrees Fahrenheit since Benson and his colleagues examined conditions in pits dug across Greenland in the 1950s, according to a study now online in the journal Geophysical Research Letters. Warming was “substantial” in the test sites located at elevations between 1,400 meters (4,593 feet) and 2,500 meters (8,202 feet), the study said.

The new survey also found evidence of snowmelt -- with ice layers formed by the refrozen water -- at every site tested. That made for some tougher digging conditions than those that Benson encountered, said lead author Chris Polashenski, a research geophysicist at the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory.

“He just had a shovel, and we needed a pick-ax,” said Polashenski, who also teaches at Dartmouth. Major changes since the 1950s were especially apparent at mid-altitude sites, according to the study. At test sites at elevations of 1,700 meters (5,577 feet) or above, Benson and his team found little or no evidence of melt, Polashenski said. Findings were different in the new survey, he said. “Here, we saw melt at every single site we went to,” he said.

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http://www.alaskadispatch.com/article/20140628/scientists-find-evidence-long-term-warming-inside-greenlands-ice-sheet