A new study has found that meltwater lakes in Greenland are draining at a dramatic rate due to rising temperatures.

The researchers said that one of the sub-glacial lakes in the region once held about 6.7 billion gallons of water but it was drained within weeks. The other lake has filled and emptied twice in the last two years.

"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," Ian Howat, an associate professor of earth sciences at The Ohio State University, who led the study, said in a statement.

The Greenland Ice Sheet is the second largest ice sheet in the world and the water which melts from this sheet pools beneath the ice.

The findings of the study are published in the journal Nature. The researchers noted that the meltwater carries stored heat - called latent heat - and it plays a role in reducing the stiffness of the surrounding ice.

"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," co-author Michael Bevis explained.

The researchers said that it is likely that thousands of such lakes are scattered along the Greenland coast. "Until we get a good map of the bed topography where this lake was, we have no idea whatsoever how many lakes could be out there," Howat said.