Lead author Chloe Gustafson and climber Meghan Seifert are installing geophysical instruments to measure groundwater under the Whillans Icy Stream in West Antarctica. 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 discovery of groundwater under the Antarctic ice stream. The discovery confirms what scientists have already suspected, but have not been able to confirm so far.
Scientists are requesting data from all parts of Antarctica’s ice sheet to understand how the system works and how it changes over time in response to climate change. The study provides insight into a previously inaccessible and unexplored part of Antarctica’s ice sheet and improves scientists’ understanding of how it can affect sea levels.
“Ice flows are important because they direct about 90 percent of Antarctic ice from the interior to the periphery,” said Chloe Gustafson, a doctoral student at the Scripps Institute of Oceanography at the University of California, San Diego. The groundwater at the base of these ice streams can affect their flow, thus potentially affecting how ice is transported outside the Antarctic continent.
Although the team has depicted only one ice stream, there are many more in Antarctica. “This suggests that there is probably groundwater under more Antarctic ice flows,” Gustafson said.
A team of scientists from Scripps Oceanography and Lamont-Doherty Earth Observatory at Columbia University is leading the project. Gustafson and six co-authors report their findings in the May 6, 2022, issue of the journal Science.
“From our understanding of how the planet works, it’s hypothesized that there is 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.
Researchers measured groundwater during the 2018-2019 field season using a terrestrial geophysical electromagnetic (EM) method called magnetotellurics. The method uses variations in the Earth’s electric and magnetic fields to measure underground resistance. This study was the first time the method was used to search for groundwater under a glacial stream.
Timelapse video showing the crew setting up a magneto-telluric station on the suburban Lake Wilens in West Antarctica.
“This technique is not usually used in polar environments,” Fricker said. “This is a good demonstration of the power of technology and how much it can bring to our knowledge not only of Antarctica, but also of Greenland and other glacier regions.
The technique has been used in Antarctica since the 1990s, but these studies have focused on depicting deep crustal characteristics at depths well below 10 kilometers (6.2 miles). However, studies have had the effect of demonstrating that scientists can also use magnetotellurics on ice and snow, Gustafson said.
“We took their example and applied it to a shallow issue of hydrology, within five kilometers (3.1 miles) of the subglacial environment.”
Over the past decade, aerial electromagnetic techniques have been used to depict shallow groundwater in the upper 100 to 200 meters (328 to 656 feet) beneath some thin glaciers and permanently frozen areas of McMurdo’s dry valleys. But these techniques can only see through about 350 meters (1,148 feet) of ice.
The Whillans ice stream, where Gustafson and colleagues collected the data, is about 800 meters (2625 feet) thick. Their new data fills a wide gap between previous deep and shallow datasets.
Chloe Gustafson was part of a team of four who spent six weeks camping on ice and snow, collecting data on Whillans Ice Stream from November 2018 to January 2019. Together, they overcame the challenges of working in Antarctic conditions, including minus temperatures temperatures and strong winds.
“We took pictures from the ice bed about five kilometers and even deeper,” said Kerry Key, an associate professor of Earth and Environmental Sciences at Columbia University and a graduate of Scripps Oceanography.
“I hope people will start looking at electromagnetics as part of standard Antarctic geophysical tools,” Gustafson said.
The scientific study is based on passively collected, naturally generated magnetotelluric signals to measure variations in electrical resistance.
“This tells us about the characteristics of groundwater, because fresh water will appear very differently in our images than salt water,” Gustafson said.
The increase in EM measurements was seismic imagery data provided by co-author Paul Winbury of Central Washington University. These data confirmed the existence of thick sediments buried under ice and snow for 60 miles, which separated the magnetotelluric studies of the field team.
Researchers have calculated that if they manage to squeeze groundwater from sediments on the surface, it will form a lake that varies from 220 to 820 meters (722 to 2690 feet) deep.
“The Empire State Building next to the antenna is about 420 meters high,” Gustafson said. “At the shallow end of the water, about half of it would go up to the Empire State Building. At the deepest end are almost two Empire State Buildings stacked on top of each other. This is important because the glacial lakes in this area are two to 15 meters deep. It’s like one to four floors of the Empire State Building.
Groundwater could exist under similar conditions on other planets or moons that release heat from their interior, Key said.
“You can imagine a frozen lid on a liquid interior, whether it’s completely liquid or liquid-saturated sediments,” he said. “You can think of what we see in Antarctica as potentially similar to what you can find in Europe or some other ice-covered planets or moons.
The existence of subterranean groundwater also has implications for the release of significant amounts of carbon that have previously been stored by microbial communities adapted to seawater.
“Groundwater movement means it has the potential to transport more carbon into the ocean than we previously thought,” said Gustafson, who completed her doctorate under Kee’s supervision in Colombia in 2020.
For more information on this study, see Scientists have discovered a massive groundwater system in Antarctic ice sediments.
Reference: “Dynamic Salt Groundwater System Mapped Under Antarctic Ice Stream” by Chloe D. Gustafson, Kerry Key, Matryw 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 Research Consortium supported the study as part of a project to scientifically access the Antarctic subglacial lakes. Co-authors include Scripps Oceanography graduate Matthew Siegfried and Ryan A. Ventureli of the Colorado Mining School; and Alexander B. Misho, Bigelow Laboratory for Ocean Science, Maine.
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