A team of scientists from Columbia University’s Lamont-Doherty Earth Observatory has discovered an ancient lake bed buried under more than a kilometer of ice that may hold secrets about Greenland’s past climate. Geomorphological analysis and hydrological modeling indicate that the basin once hosted a lake with an area of up to 7,100 square kilometers and a volume of up to 580 cubic km. The lake was formed when northwest Greenland was ice-free, sometime in Earth’s history hundreds of thousands or even millions of years ago, and may contain unique chemical and fossil traces of past climates and lives.
Important for the future
Given the rapid melting of Greenland today, the lake could reveal something about the future of the Arctic as the polar ice caps shrink. “This could be an important repository of information, in a landscape that at this moment is totally hidden and inaccessible,” said Guy Paxman, leader of the work that publishes the journal Earth and Planetary Science Letters . “We are working to try to understand how the Greenland ice sheet has behaved in the past. It is important if we want to understand how it will behave in the coming decades.” Recall that the ice sheet, which has been melting at an accelerating rate in recent years, contains enough water to raise global sea levels by more than 7 meters.
This fossil lake bed has never been observed by science in this part of the world and we know that the colossal Greenland ice sheet is full of mysteries hidden under its icy skin as it continues to lose mass at an alarming rate in a world in constant warming.
The researchers mapped the lake bed by analyzing data from airborne geophysical instruments that can read signals penetrating the ice and provide images of the geological structures below. Most of the data comes from planes flying low over the ice sheet as part of NASA’s Operation IceBridge.
This extinct lake has long been dry and is currently filled with eons of sedimentary fill, loose rock up to 1.2 kilometers thick and covered by an additional 1.8 kilometers of ice (an ice seal). The researchers estimate that the water depth in the ancient lake ranged from 50 to 250 meters and this is the first time this type of subglacial feature has been discovered on our planet.
The evidence is not conclusive
The lake could have been formed when an ancient fault split the Earth , creating a depression, or it could have been a basin carved out by a retreating glacier, they point out.
According to the researchers, for the sediment to accumulate in such a substantial way, there must have been long periods of time without ice . Drilling down to the sediment and analyzing it could give us more insight into the ice melt pattern that took place so many years ago. A sediment like this can contain a variety of materials that can show us the climate at the time of settlement, and even data on the local fauna.
“The basin may be an important site for future drilling under the ice and the retrieval of sediment records that can provide valuable information on the glacial, climatological and environmental history of the region,” the scientists conclude.
There are no current plans to drill into the lake bed, but such a feat would be possible.
Referencia: Guy J.G. Paxman et al. A fault-bounded palaeo-lake basin preserved beneath the Greenland Ice Sheet. Earth and Planetary Science Letters, published online October 28, 2020; doi: 10.1016/j.epsl.2020.116647
