Scientists track cracks in Greenland’s ice sheet

New York Times : Scientists have observed significant increases in the crevasse fields of the Greenland ice sheet, the second largest body of ice in the world. Those changes could influence how the ice sheets move toward the ocean and raise sea levels, according to their paper published in Geophysical Research Letters.The researchers, from the Cooperative Institute for Research in Environmental Sciences , a joint institute of the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder, compared high-resolution images from 1985 and 2009 in Sermeq Avannarleq, in western Greenland. They observed that an increase in crevasses can cause both a slowing and an accelerating effect. More crevasses mean fewer tunnels in the ice that transport surface water to the base of the sheet, and therefore less lubricant to assist the ice sheet’s sliding across the landscape. However, the increased surface area that results from the higher number of crevasses means more of the ice’s interior is exposed to warming by surface melt water—as the ice sheet warms, it flows faster. What that means for overall sea-level rise remains to be seen, according to William Colgan, the report’s lead author.