Ancient Riverbeds Reveal Clues about Disappearing Glaciers

 

image of a landscape with grass-covered ridges in foreground, water and mountains in background

An esker snakes across the ground in Iceland
Robert Storrar

An amazing landscape left behind by melting ice sheets offers clues to the future of Greenland’s shrinking glaciers, a new study suggests.

The incredible terrain is in northern Canada, which is ridged with thousands of eskers ā€” the sinuous, gravelly remains of streams and rivers that flowed beneath the ice. Canada was once buried beneath miles of ice, similar to the way Greenland is today. Called the Laurentide Ice Sheet, this massive ice cap covered all of Canada and parts of the northern United States 15,000 years ago. When the Laurentide Ice Sheet started melting, the retreating ice left behind a record of its demise, such as the eskers, still visible on the Arctic tundra. Deciphering this record could provide a better forecast of the future of Greenland’s changing ice sheet, scientists think.

“There’s kind of a contentious debate at the moment about what’s happening in Greenland,” said lead study author Robert Storrar, a geomorphologist at Durham University in the United Kingdom. The debate hinges on what happens to the sapphire-blue meltwater that appears each summer on top of the Greenland ice. After the water finds a way to the bottom of the ice sheet, how does the water flow beneath the ice ā€” in channels like rivers and streams, or in a different way, perhaps like a thin sheet, lubricating the ice? More important, as Earth’s climate warms, will more meltwater make Greenland’s glaciers speed up, ultimately increasing sea level rise? [Image Gallery: Greenland’s Melting Glaciers]

“At the moment, the IPCC models don’t take account of what the water looks like at all,” Storrar said, referring to predictions by the Intergovernmental Panel on Climate Change.

[More-ScientificAmerican]