In April 2014, researchers flew over a site in southwest Greenland to find that a sub-glacial lake had drained away. This photo shows the crater left behind, as well as a deep crack in the ice.
Credit: Photo by Stephen Price, Los Alamos National Laboratory, courtesy of The Ohio State University.
Posted: 21 Jan 2015 10:51 AM PST
Researchers discovered craters left behind when two sub-glacial lakes in Greenland drained away — an indication that the natural plumbing system beneath the ice sheet is overflowing with meltwater. One lake once held billions of gallons of water and emptied to form a mile-wide crater in just a few weeks. The other lake has filled and emptied twice in the last two years.
Researchers who are building the highest-resolution map of the Greenland Ice Sheet to date have made a surprising discovery: two lakes of meltwater that pooled beneath the ice and rapidly drained away. One lake once held billions of gallons of water and emptied to form a mile-wide crater in just a few weeks. The other lake has filled and emptied twice in the last two years.
Researchers at The Ohio State University published findings on each lake separately: the first in the open-access journal The Cryosphere and the second in the journal Nature.
Ian Howat, associate professor of earth sciences at Ohio State, leads the team that discovered the cratered lake described in The Cryosphere. To him, the find adds to a growing body of evidence that meltwater has started overflowing the ice sheet’s natural plumbing system and is causing “blowouts” that simply drain lakes away.
“The fact that our lake appears to have been stable for at least several decades, and then drained in a matter of weeks — or less — after a few very hot summers, may signal a fundamental change happening in the ice sheet,” Howat said…Each time the lake fills, the meltwater carries stored heat, called latent heat, along with it, reducing the stiffness of the surrounding ice and making it more likely to flow out to sea, he said. Bevis explained the long-term implications. “If enough water is pouring down into the Greenland Ice Sheet for us to see the same sub-glacial lake empty and re-fill itself over and over, then there must be so much latent heat being released under the ice that we’d have to expect it to change the large-scale behavior of the ice sheet,” he said….Though researchers have long known of the existence of sub-glacial lakes, never before have they witnessed any draining away. The sudden discovery of two — one of which seems to be refilling and draining repeatedly — signals to Bevis that Greenland ice loss has likely reached a milestone.
“It’s pretty telling that these two lakes were discovered back to back,” he said. “We can actually see the meltwater pour down into these holes. We can actually watch these lakes drain out and fill up again in real time. With melting like that, even the deep interior of the ice sheet is going to change.”….
- Michael J. Willis, Bradley G. Herried, Michael G. Bevis, Robin E. Bell. Recharge of a subglacial lake by surface meltwater in northeast Greenland. Nature, 2015; DOI: 10.1038/nature14116
- I. M. Howat, C. Porter, M. J. Noh, B. E. Smith, S. Jeong. Brief Communication: Sudden drainage of a subglacial lake beneath the Greenland Ice Sheet. The Cryosphere, 2015; 9 (1): 103 DOI: 10.5194/tc-9-103-2015