Scientists have discovered changes in the subglacial lakes that have formed below the massive Greenland ice sheet. These lakes could make the ice more sensitive to changes in the climate than many previously believed.
According to a study published by a team of U.S. scientists that will appear in the journal Nature, while these aren't the first lakes to be discovered below the ice the findings do add to climatologists' understanding of the effect of global warming on the ice sheet's basal ice layer, which sits on top of the island's bedrock.
Meltwater is one of the largest contributors to the rise in sea levels globally, threatening coast cities across the entire world. The meltwater is the result of the rise in temperatures and essentially acts as a lubricant to the basal layer of ice, increasing the chances that it will one day slide out to sea.
Between 2012 and 2014, scientists have discovered meltwater had pooled on the glacier's surface and then suddenly drained. Scientists assume these lakes seeped under the ice sheet, transferring heat to the basal layer.
"If enough water is pouring down into the Greenland Ice Sheet for us to see the same subglacial lake empty and refill 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," study co-author Michael Bevis, of the School of Earth Sciences at Ohio State University in Columbus, said in a recent statement.
Two of the subglacial lakes already known to scientists have recently drained in a manner of weeks. In one spot along Greenland's ice sheet, one lake held more than 7 billion gallons of water (supplied by melting ice caps), is now a cold, empty crater that stretches some 1.2 miles wide and 230 feet deep.
Greenland's ice sheet covers almost 80 percent of the island and is the second largest ice sheet in the world, after Antarctica. The volume of ice on Greenland is estimated at 2.8 million cubic kilometers with some spots in the ice measuring nearly 3 kilometers thick.
As global temperatures have risen over the past century with last year being the warmest on record, large sections of the ice have melted, pouring billions of tons of water into the ocean.
Even more concerning to scientists was that in March it was discovered that Greenland's ice sheet was melting faster than originally believed, resulting in an additional 10 billion tons of water being added to the oceans.
Researchers say that as more of that water drains into the subsurface and accumulates underneath the ice sheet, the heat it releases can soften the surrounding ice, "which may eventually cause an increase in ice flow," lead author of the new study and a researcher with Cornell University, Michael Willis says. "Each summer scientists see bright blue streams form on the surface of Greenland as warm air melts the ice sheet. What happens to this water when it disappears into cracks in the ice has remained a mystery."
