Subglacial Lakes Beneath the Greenland Ice Sheet Refill with Meltwater

Scientists have made a surprising discovery beneath the Greenland Ice Sheet. While building the highest-resolution map yet of this ice sheet, they found two lakes of meltwater that pooled beneath the ice and rapidly drained away.

These lakes weren't small either. One 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. These lakes, in particular, add to a growing body of evidence that meltwater has started overflowing the ice sheet's natural plumbing system.

"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," said Ian Howat, one of the researchers, in a news release.

Each time the lakes fills, the meltwater carries stored heat, called latent heat, along with it. This reduces the stiffness of the surrounding ice and makes it more likely to flow out to sea.

"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," said Michael Bevis, one of the researchers.

The crater itself measures about 1.2 miles across and around 230 feet deep. The lake that formed, therefore, probably contained 6.7 billion gallons of water. While this isn't a huge lake, it's still roughly the same size as the combined reservoirs that supply water to the Columbus Ohio metropolitan area's 1.9 million residents.

Currently, research is still ongoing. Until the scientists map the bed topography of the ice sheet, they don't know exactly how many of these lakes could be out there.

"It's pretty telling that these two lakes were discovered back to back," said Bevis. "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."

The findings reveal that as temperatures warm, the ice sheet is continuing to change. With this draining, it's possible that the ice sheet could melt faster and faster over time.

The findings are published in the journals Nature and The Cryosphere.

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