They discover a giant groundwater system under the Antarctic ice – Science

The study provides insight into the sediments under Antarctica’s ice, an inaccessible and hitherto unexplored part and will help scientists better understand how the frozen continent functions and how it changes in response to climate.

The research, published Thursday in the journal Science, was led by scientists from Scripps Oceanograph and Columbia University’s Lamont-Doherty Earth Observatory.

“Ice currents are important because they move about 90 percent of Antarctica’s ice from the interior to the extremities,” explains Chloe Gustafson, a postdoctoral researcher at the Scripps Institution of Oceanography at the University of California, San Diego.

The researcher explained that the groundwater that lies under these glacial currents “can affect their flow, and thus affect the transport of ice out of Antarctica.”

To conduct the study, the researchers used a geophysical electromagnetic (EM) method that uses differences in the Earth’s electric and magnetic fields to measure Earth’s resistance (something like scanning the Earth to see how it behaves when passing waves). .

This study represents the first time that this method has been used to search for groundwater under a glacial ice stream.

Gustafson and his colleagues collected data from the Whillans Ice Stream, which is about 800 meters thick and 100 kilometers wide and feeds the Ross Ice Shelf, the largest in the world. This data supplemented previous information from deep and shallow areas.

“We imaged from the ice layer to nearly five kilometers and even deeper,” explains Keri Kee, a researcher at Columbia University and a graduate of Scripps oceanography.

After the success of this technique demonstrated in the research, Gustafson believes it is time “people begin to think of electromagnetism as part of the standard Antarctic geophysical toolkit.”

Passively collected and naturally generated magnetic signals to measure differences in electrical resistance gave the researchers insight into the properties of groundwater, “as freshwater appears very differently in our images.” Gustafson says.

In the second part of the investigation, electromagnetic measurements were supplemented with data from seismic images collected by Paul Winbury of Central Washington University, a co-author of the study.

This analysis showed that, depending on the location, a thick layer of sediment extends under the ice bed from half a kilometer to nearly two kilometers before it reaches the bedrock.

They also confirmed that the sediment is filled with liquid water at the bottom. According to his calculations, if all of them were removed, it would form a lake with a depth of 220-820 meters.

If the Empire State Building, which is 420 meters high, is used as a reference, “At the shallow end, the water will reach half the building, and at the deep end, it will be approximately equal to two Empire State buildings, one on top of the other.” This is important because the lakes under Glaciers in this area range from 2 to 15 meters deep, Gustafson says.

The team photographed only one ice stream, but “it’s possible that there is groundwater under more Antarctic ice streams,” they say.

In addition, the authors believe that it is possible that groundwater in similar conditions exists on other planets or moons that release heat from their interiors and are covered in ice.

The presence of subglacial groundwater also has implications for carbon stored by microbial communities adapted to seawater and can release “significant amounts” of this gas that have not yet been taken into account.

“This study is just the beginning to address all of these questions. It is confirmation that deep groundwater has dynamics that have changed our understanding of the behavior of glacial currents, and will force subglacial water models to change.”