Scientists have discovered an ancient lake floor beneath Greenland ice


The ancient basin, now under a mile of ice, is shaped like a cleaver.

The ancient basin, now under a mile of ice, is shaped like a cleaver.
Image: Paxman et al., EPSL, 2020

Using radar and other ice-penetrating tools, scientists have detected a “fossil lake bed” preserved under the Greenland ice sheet, in what is the first discovery of its kind.

Now a basin suffocated by a giant sheet of ice, this former lake once measured 2,740 square miles (7,100 square kilometers) in size, which is an area comparable to Rhode Island and Delaware combined, according to a Columbia University. Press release. In some places it reached up to 250 meters deep and was fed by more than a dozen streams. It doesn’t look very Greenlandic today, but that’s probably what the island looked like millions of years ago.

Eventually, however, and we’re not quite sure when, this lake became covered in ice, never to see daylight again. New Research published in Earth and Planetary Science Letters shows that the lake floor is now buried under 1.1 miles (1.8 kilometers) of ice. The water that once flowed through this ancient basin has probably long since disappeared, smeared by the invading ice cap, but the sediments of the lake have remained in place.

Scientists have already discovered subglacial lakes in both Greenland is Antarctica. The difference here is that the fossil bottom of the newly discovered lake does not contain liquid water and is found on the rocky surface of Greenland. Such a thing has never been discovered before, according to the press release.

NASA's Operation IceBridge at work, flying over a vast Greenland ice sheet.

NASA’s Operation IceBridge at work, flying over a vast Greenland ice sheet.
Image: Kirsty Tinto / Lamont-Doherty Earth Observatory

The data used to make the discovery was collected by NASA’s IceBridge operation, which involves low altitude investigations on the Greenland ice sheet using ice-penetrating radar and instruments capable of measuring gravity and magnetic anomalies. Radar allowed scientists to create a topographical map of the earth’s surface below the ice sheet, revealing the basin. Gravity measurements showed that the material in the basin is less dense than it is it is found in the surrounding rock, which is hard and metamorphic. And because sediments are less magnetic than solid rock, the researchers were able to map the depth of sediments lying in the basin.

T.the data revealand that the ancient backdrop, located in northwestern Greenland, once featured water depths of between 164 and 820 feet (50 to 250 meters). The sediment layer was found to be 0.75 miles (1.2 kilometers) thick, a considerable depth of filling that probably accumulated over hundreds of thousands of years –and perhaps millions of yearsbefore the Greenland Ice Age. The topographical features allowed the team to identify at least 18 former stream beds that once flowed into the lake along its northern shore. A possible watercourse has also been identified to the south.

In the press release, Guy Paxman, a postdoctoral fellow at Columbia University’s Lamont-Doherty Earth Observatory who led the study, he said his team is not yet able to date the lake, but if “we could get to those sediments, they could tell us when the ice was present or absent.” Indeed, these scientists, and probably others, would very much like to get their hands on this ancient sediment, which they would do by drilling through the ice sheet.

In in addition to dating the lake and showing when ice was and was not present, sediment samples it could provide signs of ancient life in the form of plant spores or other organic materials. If detected, these biological signatures would bolster theories about Greenland’s climate history and how it once featured vast forests. As the authors write, the “subglacial landscape precedes the vast glaciation in Greenland” and, consequently, the “basin may contain important documents of regional and paleoclimatic glacial history”.

That said, some of these will be difficult to prove, as subsoil materials have been transported far and wide by the ebb and flow of glaciers.

Drilling this far into the ice is not unprecedented. In the 90s, researchers pulled a 2 mile long (3.2km long) ice core from the Greenland ice sheet, capturing 110,000 years of history. Scientists also had S.imilar success core samples in The ice of Antarctica. And now, thanks to this new discovery, we have a tempting new target in Northwest Greenland. Let’s do drilling!

Oh, I’d be remiss if I didn’t mention that awesome buried subject impact crater found in Greenland two years ago. Also found by ground-penetrating radars, the crater measures approximately 19 miles (30 kilometersS.) through, making it one of the largest asteroid craters on Earth. Some interesting things are hiding under giant ice sheets – we just have to look.


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