Ancient Lake Discovered Under Greenland May Be Millions of Years Old, Scientists Say

 The remains of a large, ancient lake are discovered under Greenland, buried deep below the ice sheet within the northwest of the country, and estimated to be many thousands of years old, if not millions, scientists say.

The huge 'fossil lake bed' may be a phenomenon the likes of which scientists haven't seen before during this part of the planet, while we all know the colossal Greenland Ice Sheet (the world's second-largest, after Antarctica's) remains filled with mysteries hidden under its frozen lid while shedding mass at an alarming pace.

Last year, scientists reported the invention of over 50 subglacial lakes beneath the Greenland Ice Sheet: bodies of thawed liquid water trapped between bedrock and also the ice sheet overhead.

The new find is of a unique nature: an ancient lake basin, long dry and now stuffed with eons of sedimentary infill – loose rock measuring up to 1.2 kilometers (three-quarters of a mile) thick – and so covered by another 1.8 kilometers of ice.

(Columbia University, adapted from Paxman et al., EPSL, 2020)

Above: The lake basin (red outline), fed by ancient streams (blue).

When the lake formed way back, however, the region would are freed from ice, researchers say, and also the basin would have supported a monumental lake with a sprawling area of roughly 7,100 square kilometers (2,741 square miles).

That's about the identical size because the combined area people states Delaware and Rhode Island, and this massive lake would have held around 580 cubic kilometers (139 cubic miles) of water, being fed by a network of a minimum of 18 ancient streams that after existed to the north of the bed, flowing into it along a sloping escarpment.

While there is no way of knowing at once just how ancient this lake is (or if it filled and drained numerous times), we'd be able to know if we could analyze the loose rock material now inside the basin: an enormous container of preserved sediment that might give us some clues about the environment of Greenland roughly forever ago.

"This may well be a crucial repository of knowledge, during a landscape that right away is completely concealed and inaccessible," says lead researcher and glacial geophysicist Guy Paxman from Columbia University.

"If we could get at those sediments, they might tell us when the ice was present or absent."

The giant bed – dubbed 'Camp Century Basin', with respect to a close-by historic military research base – was identified via observations from NASA's Operation IceBridge mission, an airborne survey of the world's polar regions.

During flights over the Greenland Ice Sheet, the team mapped the subglacial geomorphology under the ice employing a range of instruments measuring radar, gravity, and magnetic data. The readings revealed the outline of the enormous loose mass of sedimentary infill, composed of less dense and fewer magnetic material than the harder rock surrounding the mass.

It's possible, the team thinks, that the lake formed in warmer times as a result of bedrock displacement thanks to a line underneath, which is now dormant. Alternatively, glacial erosions might need to carve the form of the basin over time.

In either case, the researchers believe the traditional basin could hold a crucial sedimentary record, and if we will somehow drill down deep enough to extract and analyze it, it should indicate when the region was ice-free or ice-covered, reveal constraints of the extent of the Greenland Ice Sheet, and offer insights into past climate and environmental conditions within the region.

Whatever secrets those deeply buried rocks can tell us about polar temperature change within the ancient past may well be vital information for interpreting what's happening within the world without delay.

"We're working to do and understand how the Greenland ice sheet has behaved within the past," says Paxman. "It's important if we wish to know how it'll behave in future decades."