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.