Rising Temps Causing Greenland's Meltwater Lakes to Drain at Dramatic Rate
Rising temperatures are causing Greenland's meltwater lakes to drain at a dramatic rate, disappearing in a matter of just a few weeks, according to a new study.
One of the sub-glacial lakes once held about 6.7 billion gallons of water, only to be completely emptied in a single season. The other lake has filled and emptied twice in the last two years - "catastrophic" events that are the result of climate change.
"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.
High temperatures are causing the Greenland Ice Sheet - the second largest ice sheet in the world - to melt. This meltwater then pools beneath the ice; however, it now seems that this process is overwhelming the ice sheet's natural plumbing system, causing these lakes to simply drain and disappear.
Every time the two-mile-wide lake, described in the journal Nature, fills up, the meltwater carries stored heat - called latent heat - along with it, reducing the stiffness of the surrounding ice and making it more likely to flow out to sea, researchers say.
"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.
Described in the journal The Cryosphere, the crater of this once vast lake now sits about 50 kilometers (31 miles) inland from the southwest Greenland coast. It's two kilometers (1.2 miles) across and around 70 meters (230 feet) deep, which isn't considered big by any standards. But, to puts things in perspective, it is the same size as the reservoirs that supply water to Columbus, Ohio, a region of 1.9 million residents.
What's more, the research team says that it's possible thousands of such lakes are scattered along the Greenland coast, hidden by the massive ice sheet itself. (Scroll to read on...)
"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.
According to Howat and his colleagues, as more meltwater reaches the base of the ice sheet, it's likely that natural drainage tunnels along Greenland's coast are cutting further inland. The tunnels, carrying heat and water, are turning icy areas that were once frozen into pools of meltwater.
The rapid draining of the lakes suggests Greenland's ice loss has now reached a milestone. Researchers have long known about the existence of sub-glacial lakes, but this is the first time that they have witnessed them draining into the sea, let alone at unprecedented rates (nearly 57,000 gallons every second).
Not only are meltwater lakes causing the Greenland Ice Sheet to quickly disappear, but all this water draining into the oceans may also be a major contributor to sea level rise.
"If we can get better estimates, then we can have better projections for the extent and the impact of global warming," Marco Tedesco, a co-author of that report, said in a press release. "Greenland is really the big player for sea level rise in the future, so improving climate models is extremely crucial."
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