A huge system of groundwater was discovered under Antarctica

The research team collected data in the Antarctic cold for weeks to map the continent's subsoil.

The research team collected data in the Antarctic cold for weeks to map the continent’s subsoil.
Photo: Kerry Key

Antarctica, not just a large mass of ice, is a geologically complex continent made up of from extensive glaciers, jagged rocks and, as new research shows, large amounts of groundwater. ONE agudy published today in the journal Science describes a thick layer of groundwater beneath West Antarctica capable of governing the continent’s ice currents. Researchers behind the work believe that this could be one of the many huge groundwater reservoirs under Antarctica.

The team, led by Chloe Gustafson, currently a postdoctoral researcher at the Scripps Institute of Oceanography, traveled to West Antarctica in late 2018. Before embarking on remote field work — a dangerous mission away , a U.S. research outpost on Ross Island in Antarctica. “At the peak of the season, there may be 1,000 people living there, so it’s like a small town sometimes,” Gustafson told me by phone. “There is a galley where everyone eats, there are dormitories, there is a gym, there are a few bars.”

In addition to collecting all the tents, sleeping bags, food, and other supplies they would need, the team was trained with a climber on how to drive snowmobiles, dig snow shelters and set up tents. After a bit of bad weather, the team of four – Gustafson, Carrie Key of Columbia University Lamont-Doherty Earth Observatory, Matthew Siegfried of the Colorado Mining School, and climber Megan Seifert – flew to Ice Stream in the ice layer of West Antarctica.

McMurdo Station, shown here, is a U.S. research station located in Antarctica.

McMurdo Station, shown here, is a U.S. research station located in Antarctica.
Photo: Kerry Key

An ice stream is a relatively fast flow inside an ice sheet. These things can move at as fast as 6 feet a day in Antarctica and represent 90% of the ice flowing from the continent. They chose the Whillans Ice Stream for their study because of the existing data that has already been collected there. In 2007, Helen Fricker, another collaborator on this project, observed a system of subglacial lakes via satellite imaging. Over the next decade, researchers confirmed that there was actually a lake beneath the Whillans ice stream using seismology and drilling. “It was very interesting and we wanted to take it to the next step and see what happens deeper,” Gustafson said. “Is there groundwater?”

Most of the previous Whillans Ice Stream research was just about confirming the presence of liquid water under the ice through shallow drilling, but Gustafson and her team wanted to know what this subterranean groundwater actually looked like. Limited to a short period of time, they needed a more efficient method and settled on magneto-telluric, a passive geophysical method that Gustafson described as essentially “doing an MRI of the Earth.” Magnetics are based on his enthusiasm The ionosphere of the earth due to solar wind. This enthusiasm creates electromagnetic waves – recorded by Gustafson and her team – that travel through the Earth’s subsoil in different ways, depending on the medium.

“From these electric and magnetic field measurements, we can start to tease okay, this is the signal coming from ice, this signal is coming from salt water, this signal is coming from fresh water,” Gustafson explained.

The team had eight receivers that would bury one foot in the snow for 24 hours to collect these electromagnetic signals. As the day wore on, they dug them up and removed them a few miles, repeating this process over and over again for six weeks.

All of this data adds up to one key finding: The sediments under the Whillans ice stream were full of water. These are marine sediments deposited when Antarctica was once an open ocean millions of years ago. In their imaging, the team found that the sediments ranged in thickness from half a kilometer (about 1,600 feet) to 2 kilometers (over a mile). They determined that, beneath a layer of fresh water a few hundred meters thick (caused by the natural melting of glaciers), there is a column of water that the deeper it goes the saltier it becomes.

“Part of this salty groundwater could be a residue from the time these sediments were first deposited,” Gustafson suggested. “But then some of the salt in the groundwater could also come from periods when the ice sheet was growing, but then it receded again and the ocean water came in.”

All of this has been hypothetical so far, and researchers say they were the first to use magneto-telluriums to actually depict groundwater.

“The scientific community has known for some time that there is a thick layer of marine sediment beneath much of the West Antarctic ice sheet, but we do not know much about how the ice sheet is affected by deep groundwater, as the new study shows. saline solution, “wrote Paul Christoffersen in an email. Christoffersen, who called the new work “exciting”, is a frost specialist at the Scott Polar Research Institute at Cambridge University and has had nothing to do with it. He continued: “The new study also shows that freshwater produced by melting at the bottom of the ice sheet has penetrated several hundred meters into the groundwater system since the ice sheet formed and that salt and solutes are likely to have leaked. also in the basic drainage of the ice sheet. System.”

Groundwater under the ice stream could play a key role in how the stream carries ice to the sea. “I have this analogy: ice streams are like slips,” Gustafson said. “Well, if you have water on a slip-and-slide, you can slip fast enough. “But if there is less water or no water at all, you are not going to slip too far.”

Brad Lipovsky of the University of Washington College of the Environment echoed Gustafson’s description. He told me in a phone call: “In the first few meters below the glacier, the properties there control how fast the ice flows directly: [if] your glacier sits on top of a bunch of wet clay, it is more slippery and the ice flows faster ”.

These findings have potential implications for the rest of the continent. Gustafson said different subterranean pockets of groundwater could be found under ice streams across Antarctica. “There are observations from around Antarctica, which suggest that these sediments exist from below [other] ice streams, “he said. “I would bet these aquifers are common features throughout Antarctica.”

While glaciers cover only 10% of the Earth, glaciers in Antarctica account for 85% of that coverage. Depending on how this groundwater behaves, it could help the ice to flow faster or slower into the ocean. Researchers suggest that when the system is stable, groundwater will drain into the Southern Ocean as more meltwater seeps into the sediments. But if ice streams lost mass under rising climate change temperatures, their reduced pressure on sediments beneath them could allow groundwater to rise to the surface, further lubricating the base of the stream and increasing it.of speed, threatening the future of the continent’s ice cover.

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