COLUMBUS, Ohio, Jan. 22 (UPI) -- Two subglacial Greenland lakes thought to be stable -- pockets of icy water accumulated over many years -- are now gone, drained in a matter of weeks. And scientists aren't exactly sure why or what it means.
In one spot along Greenland's massive ice sheet, what was once a holding cell for more than 7 billion gallons of water (supplied by melting ice caps), is now a cold, empty crater, stretching some 1.2 miles wide and 230 feet deep.
The emptied lake was discovered by scientists at Ohio State who are studying the mechanisms of the island's massive ice sheet in relation to melting sea ice and sea level rise.
The other lake, now a two-mile-wide hole in the ice, was discovered by a team of scientists from Cornell. It has drained and filled twice since 2012. It is now slowly refilling after its most recent disappearing act, researchers say.
Geologists studying the two lakes say this new behavior is worrisome. They believe an uptick in meltwater is overwhelming the lakes' plumbing systems, causing "blowouts" that precipitate the rapid draining.
"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," Ohio State's Ian Howat told CBS.
Howat led the research into the disappearance of the first lake, the details of which were published in journal The Cryosphere. The study of the second disappearing lake was published separately in the journal Nature.
The rapid movement of meltwater, traveling downed widened, blown-out drainage conduits, is worrisome because it's not only a consequence but an accelerant. These sorts of phenomena can have compounding effects that current climate change and sea level rise models don't account for.
Expanded meltwater drainage systems bring warm water into contact with increasing amounts of ice, thus hastening the melting process. Latent heat carried by the meltwater also loosens surrounding ice, ensuring more chunks flow out to sea and melt.
"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," Michael Bevis, an earth scientist at Ohio State, said in a recent press release.
"It's pretty telling that these two lakes were discovered back to back," Bevis added. "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."