Gravity Anomaly Reveals Ancient City-Sized Lake Hidden Under Antarctic Ice

After a season of anomalous sea ice loss in Antarctica, a group of researchers have discovered an ancient city-sized lake under the ice that offers clues into the geographical history of the continent. 

Detailed in a paper published Monday in the peer-reviewed journal Geology, a team of researchers at the University of Texas, Austin (UT Austin) have located a massive lake in Eastern Antarctica after three years of flying an instrumented research aircraft over it. They first identified the lake, located underneath the ice sheet, on satellite images of the Princess Elizabeth Land sector, an eastern fragment claimed by Australia. It was only after scanning the region with ice-penetrating radar that they were able to confirm the existence of a yet-undiscovered geological entity, which they named Lake Snow Eagle (LSE). 

“I literally jumped when I first saw that bright radar reflection,” the paper’s lead author, Shuai Yan, lead author on the paper and PhD candidate at UT Austin said in a press release. 

“The sediment layer at the bottom of Lake Snow Eagle could archive a very valuable sedimentary record of what Antarctica looked like before it froze over, how it froze over, and the evolution of the ice sheet since then,” Yan elaborated in an email to Motherboard. “A sample from this sediment layer could provide major insights on the past behavior of the Antarctic Ice Sheet during glacial cycles, and how it might behave in the future.”

Yan—who served as flight planner on the research team behind the paper—and the team used sensors that picked up a gravity anomaly as well as a magnetic anomaly around the site. They then used further measurements to craft a detailed picture of what lay under the ice: a lake nearly the size of Chicago at 229 square miles. They identified a layer of water-saturated sediment with an average thickness of 100 meters at the bottom of the lake, some 1,000 feet below its surface, some of which the researchers believe could’ve been deposited by river flow well before the creation of the ice sheet itself.

“LSE is located in a deep elongated subglacial trench,” the paper reads. “The bottom portion of the sedimentary column is potentially dominated by fluvial sediment that predates Antarctic glaciation.” 

“Knowledge of the geologic framework of the trench housing LSE provides crucial insight toward the tectonic context of the lake,” they go on to say, before noting that identifying the rate at which the sediment accumulated would offer valuable insight into how old it is. Depending on its age, the sediment could offer the team an “unprecedented and uninterrupted record of ice and climate change.” 

The next steps for Yan and his team and to continue collecting surveys to better understand how the lake flows between the surface of the ice and the sediment that underlies it.

 “This lake’s been accumulating sediment over a very long time, potentially taking us through the period when Antarctica had no ice at all, to when it went into deep freeze,” Martin Siegert, professor and glaciologist at Imperial College London and co-author on the paper said in the press release. “We don’t have a single record of all those events in one place, but the sediments at the bottom of this lake could be ideal.”