Hidden under more than a mile of ice for millions of years, a massive mega-canyon has been discovered beneath the Greenland ice sheet by a team of scientists who announced their findings Thursday in the journal Science.
"One might assume that the landscape of the Earth has been fully explored and mapped," Jonathan Bamber, professor of physical geography at the U.K.-based University of Bristol and lead author of the study, told NASA. "Our research shows there's still a lot left to discover."
Using data collected over the past few decades by NASA and researchers from Germany and the U.K. with ice-penetrating radar equipment hung from the belly of an airplane, the scientists found a canyon under Greenland's ice that stretches more than 460 miles long -- about twice the length of the Grand Canyon -- and just over 6 miles wide.
J. Bamber/University of Bristol
A 3-D image of the canyon under Greenland's ice sheet.
The canyon begins near the center of Greenland and continues all the way to the Petermann Glacier fjord, which empties out on the northern coast. This suggests that the canyon was carved by an ancient river long before the Arctic island was covered by today's ice sheet, which spans more than 660,000 square miles.
"Nowhere does it look like a typical U-shaped valley," Bamber told NPR in an interview yesterday, noting that's the shape a glacier-carved canyon would have. "At its northern limit, it looks pretty much like a river valley. It's got relatively steep slopes, and it's quite deep."
Because the canyon slopes continuously and gradually on its meandering path toward the sea -- without the ice sheet sitting on top of it, a river in the canyon would drop nearly two feet every mile, the scientists estimate -- glaciers probably didn't play a role in its formation.
"We think this was a major river system in Greenland before the ice sheet was there," he says. "And it's just survived the cover by the ice sheet."
This helps explain why Greenland doesn't have large sub-glacial lakes under its ice, unlike Antarctica, the scientists say -- because the canyon transports meltwater from Greenland's interior to the edge of the ice sheet and into the Arctic Ocean.
The researchers in the study pieced together data from radar images of the ice taken over the past 40 years, much of collected by missions like NASA's Operation IceBridge, using equipment that beams radio waves through the ice but which bounce off the bedrock at the bottom.
From the images they collected, the scientists assembled a three-dimensional map of the landscape underneath Greenland's ice sheet. It was only then that the canyon came fully into view, Bamber said in an interview with the London Telegraph.
“It is a huge feature and it was quite a surprise to all of us that it was really there," he told the U.K.-based newspaper. “We are pretty excited and amazed when we discovered this huge, undiscovered feature.”Follow @terrellwrites
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Diving into the water in Tasiilaq in southeastern Greenland. (Kristinn Einarsson/Visit Greenland)