Scientists have discovered an ancient lake floor beneath the Greenland ice

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 gigantic sheet of ice, this former lake once measured 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 1.8 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 and 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.

The data used to make the discovery was collected by NASA’s IceBridge operation, which involves low-altitude surveys of the Greenland ice sheet using ice-penetrating radars and instruments capable of measuring gravity and magnetic anomalies. The radar allowed the 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 that 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.

The data revealed that the ancient bottom of the lake, which is located in northwestern Greenland, once had water depths between 50 and 250 meters. The sediment layer was found to be 1.2 kilometers thick, a considerable depth of fill that probably accumulated over hundreds of thousands of years – and possibly millions of years – before 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 researcher at Columbia University’s Lamont-Doherty Earth Observatory who conducted the study, said his team is not yet able to date the lake, but if “we could get to those sediments could tell us when ice was present or absent. “In fact, 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 addition to dating the lake and showing when ice was and was not present, sediment samples could provide evidence 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 1990s, researchers extracted a 3.2-kilometer-long core of ice from the Greenland ice sheet, capturing 110,000 years of history. Scientists have also had similar success in drilling cores in the Antarctic ice. 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 incredible buried impact crater found in Greenland two years ago. Also found by ground-penetrating radars, the crater measures around 30 kilometers in diameter, making it one of the largest asteroid craters on Earth. Some interesting things are hiding under giant ice sheets – we just have to look.