Lakes of meltwater can crack Greenland's ice and contribute to faster ice sheet flow

Researchers make first observations of surface meltwater cutting through the ice sheet to lubricate the bottom

Glaciologist Sarah Das stands atop a block of ice that was raised up 6 meters by the sudden drainage of a meltwater lake in Greenland. The block sits in the... Click here for more information.

Researchers from the Woods Hole Oceanographic Institution (WHOI) and the University of Washington (UW) have for the first time documented the sudden and complete drainage of a lake of meltwater from the top of the Greenland ice sheet to its base. From those observations, scientists have uncovered a plumbing system for the ice sheet, where meltwater can penetrate thick, cold ice and accelerate some of the large-scale summer movements of the ice sheet.

According to research by glaciologists Sarah Das of WHOI and Ian Joughin of UW, the lubricating effect of the meltwater can accelerate ice flow 50 to 100% in some of the broad, slow-moving areas of the ice sheet.

“We found clear evidence that supraglacial lakes—the pools of meltwater that form on the surface in summer—can actually drive a crack through the ice sheet in a process called hydrofracture,” said Das, an assistant scientist in the WHOI Department of Geology and Geophysics. “If there is a crack or defect in the surface that is large enough, and a sufficient reservoir of water to keep that crack filled, it can create a conduit all the way down to the bed of the ice sheet.”

But the results from Das and Joughin also show that while surface melt plays a significant role in overall ice sheet dynamics, it has a more subdued influence on the fast-moving outlet glaciers (which discharge ice to the ocean) than has frequently been hypothesized.

The research by Das and Joughin was compiled into two complementary papers and published on April 17 in the online journal Science Express. The papers will be printed in Science magazine on May 9. Co-authors of the work include Mark Behn, Dan Lizarralde and Maya Bhatia of WHOI; Ian Howat, Twila Moon, and Ben Smith of UW; and Matt King of Newcastle University.