A new survey of the Greenland Ice Sheet has revealed dozens of previously unknown lakes lying beneath the massive body of ice.

The 56 lakes, ranging in size from about 650 feet to more than 3.5 miles, bring the number of lakes known to exist under the sheet to 60. The researchers say it’s the first comprehensive look at bodies of water locked under the sheet, which in recent years has been melting rapidly as a result of global warming.

“We found a lot more lakes than what people have thought before,” said Winnie Chu, a postdoctoral researcher at Stanford University in Palo Alto, California, and coauthor of a paper about the research published June 26 in the journal Nature Communications.

What do the subglacial lakes mean for the future of the Greenland Ice Sheet given the looming threat of climate change? Left unchecked, melting of the ice sheets in Greenland and Antarctica, the site of Earth’s other massive ice sheet, will cause a rise in sea levels that threatens to inundate low-lying coastal areas around the world, researchers predict. Chu said the lakes could have a lubricating effect on the ice above, an effect she likened to a water slide. As the ice slides down to lower elevations, it could be even more susceptible to surface melting. Even so, it’s not clear that lots of lakes below the Greenland Ice Sheet will have a significant effect on sea levels.

"We don't think that subglacial lakes in Greenland are a huge concern for climate change,” Chu said, adding that the bodies of water could even store meltwater that would otherwise enter the oceans.

Scientists have long suspected that the ground beneath the Greenland Ice Sheet is dotted with lakes. Some subglacial lakes form when pressure from above or geothermal hot spots from below melt portions of the ice, others when meltwater trickles down from above through holes known as moulins to pool in hollows under the ice.

To count the lakes, the researchers looked for the unique signature of liquid water in more than two decades’ worth of ice-penetrating radar data collected by NASA aircraft during flyovers of the Greenland Ice Sheet. They also studied detailed topographic maps of the sheet, looking for telltale hollows suggesting that a subglacial lake might lie below.

Twila Moon, a research scientist who studies the Greenland Ice Sheet at the University of Colorado's National Snow and Ice Data Center in Boulder and who was not involved in the research, said she didn’t expect the discoveries to affect melting projections. “A lot of these lakes seem like they have existed there for a long time,” she said. “At this point, we don’t have to go back and recalculate how we think [the ice sheet] might change in the future.”

Moon praised the study for its thoroughness, adding that more research will be required to fully understand the relationship between the ice sheet and its subglacial lakes. “This is the kind of work that is at the tip of the iceberg,” she said. “They’re just starting to make more progress in understanding what’s down there.”

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