Groundwater discovered in sediments buried deep under Antarctic ice

Lead author Chloe Gustafson and mountaineer Meghan Seifert install geophysical instruments to measure groundwater beneath West Antarctica’s Whillans Ice Stream. Credit: Kerry Key/Lamont-Doherty Earth Observatory

The study proves the value of electromagnetic techniques in a new polar environment.

Researchers have made the first detection of groundwater beneath an Antarctic ice stream. The discovery confirms what scientists had already suspected but had not been able to verify until now.

Scientists need data from all parts of the Antarctic ice sheet to understand how the system works and how it changes over time in response to climate. The research provides insight into a previously inaccessible and unexplored part of the Antarctic ice sheet and improves scientists’ understanding of how it might affect sea levels.

“Ice currents are important because they funnel about 90% of Antarctica’s ice from the interior to the margins,” said Chloe Gustafson, postdoctoral fellow at UC San Diego’s Scripps Institution of Oceanography. The groundwater at the base of these ice streams can affect their flow, potentially influencing how the ice is transported out of the Antarctic continent.

Although the team only photographed one ice stream, there are many more in Antarctica. “This suggests there is likely groundwater beneath more Antarctic ice streams,” Gustafson said.

A team of scientists from Scripps Oceanography and[{” attribute=””>Columbia University’s Lamont-Doherty Earth Observatory led the project. Gustafson and six co-authors reported their findings in the May 6, 2022, issue of the journal Science.

“It’s been a hypothesis from our understanding of how the planet works that there’s groundwater under Antarctica, but we haven’t been able to measure it before,” said study co-author Helen Amanda Fricker, a Scripps glaciologist and co-director of the Scripps Polar Center.

The researchers measured the groundwater during the 2018-2019 field season by using a ground-based geophysical electromagnetic (EM) method called magnetotellurics. The method uses variations in Earth’s electric and magnetic fields to measure subsurface resistivity. This study was the first time the method had been used to search for groundwater beneath a glacial ice stream.

Time-lapse video showing the field crew setting up a magnetotelluric station at subglacial Lake Whillans in West Antarctica.

“This technique has generally not been used in polar environments,” Fricker said. “It’s a great demonstration of the power of the technique and how much it can bring to our knowledge not only of Antarctica, but also of Greenland and other glacial regions.”

The technique has been used in Antarctica since the 1990s, but these studies aimed to image deep crustal features at depths well below 10 kilometers (6.2 miles). The studies, however, had the effect of demonstrating that scientists could also use magnetotellurics on ice and snow, Gustafson said.

“We took their example and applied it to a shallow hydrology question, within five kilometers (3.1 miles) of the subglacial environment.”

Over the past decade, airborne electromagnetic techniques have been used to image shallow groundwater in the upper 100 to 200 meters (328 to 656 feet) beneath some thin glaciers and permanently frozen areas of the McMurdo Dry Valleys. But these techniques can only see through about 350 meters (1,148 feet) of ice.

The Whillans Ice Stream, where Gustafson and his colleagues collected the data, is about 800 meters (2,625 feet) thick. Their new data fills a wide gap between these previous deep and shallow data sets.

Chloe Gustafson was part of a four-person team that spent six weeks camping in the ice and snow collecting data on the Whillans Ice Stream from November 2018 to January 2019. Together they overcame the challenges of working in Antarctic terrain conditions, including sub-zero temperatures and high winds.

“We photographed from the ice bed about three miles and even deeper,” said Kerry Key, associate professor of earth and environmental sciences at Columbia University and Scripps Oceanography alumnus.

“I hope people will start thinking about electromagnetism as part of the standard Antarctic geophysical toolkit,” Gustafson said.

the Science The study was based on passively collected and naturally generated magnetotelluric signals to measure electrical resistivity variations.

“It tells us about groundwater characteristics, because fresh water will appear very different in our imagery than salt water,” Gustafson said.

Seismic imagery data provided by co-author Paul Winberry of Central Washington University supplemented the EM measurements. These data confirmed the existence of thick sediments buried under the ice and snow all along the 60 miles that separated the magnetotelluric readings from the field team.

The researchers calculated that if they could press groundwater from the sediment to the surface, it would form a lake with a depth ranging from 220 to 820 meters (722 to 2,690 ft).

“The Empire State Building up to the antenna is about 420 meters tall,” Gustafson said. “At the shallow end, our water would come up the Empire State Building about halfway. At the deep end, there are almost two Empire State Buildings stacked on top of each other. This is important because the subglacial lakes in this region range in depth from 2 to 15 meters. It’s like a four-story Empire State Building.

Groundwater may exist in similar conditions on other planets or moons that release heat from their interiors, Key said.

“You can imagine a frozen lid on a liquid interior, whether it’s completely liquid or liquid-saturated sediment,” he said. “You can think of what we see in Antarctica as potentially analogous to what you might find on Europa or other ice-covered planets or moons.”

The existence of subglacial groundwater also has implications for the release of significant amounts of carbon that were previously stored by seawater-adapted communities of microbes.

“Groundwater movement means there’s the potential for more carbon to be transported to the ocean than we previously thought,” said Gustafson, who completed her PhD under Key’s supervision at Columbia in 2020.

For more on this research, see Scientists discover massive groundwater system in sediments beneath Antarctic ice.

Reference: “A dynamic saline groundwater system mapped beneath an Antarctic ice stream” by Chloe D. Gustafson, Kerry Key, Matthew R. Siegfried, J. Paul Winberry, Helen A. Fricker, Ryan A. Venturelli, and Alexander B Michaud, May 5, 2022, Science.
DOI: 10.1126/science.abm3301

The National Science Foundation and the Columbia University Electromagnetic Methods Research Consortium supported this study as part of the Scientific Access to Subglacial Antarctic Lakes Project. Co-authors included Scripps Oceanography alumnus Matthew Siegfried and Ryan A. Venturelli of the Colorado School of Mines; and Alexander B. Michaud, Bigelow Laboratory for Ocean Sciences, Maine.

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