The groundwater system, found in deep sediments in West Antarctica, is likely to have the consistency of a wet sponge, reveals an unexplored part of the region and could have implications for how the frozen continent responds to the climate crisis, according to a new study.
“People have speculated that there may be deep groundwater in these sediments, but so far no one has taken any detailed images,” said lead author Chloe Gustafson, a postdoctoral fellow at the Scripps Institute at the University of California, San Diego. Oceanography, in a news statement.
“Antarctica has 57 meters (187 feet) of potential for sea level rise, so we want to make sure we include all the processes that control how ice flows out of the continent into the oceans. Groundwater is currently missing from our ice stream models, “she added by email.
The ice cap that covers Antarctica is not a solid whole. Researchers in Antarctica have discovered in recent years hundreds of interconnected liquid lakes and rivers located in the ice itself. But this is the first time large amounts of liquid water have been found in subglacial sediments.
The study, published in the journal Science on Thursday, focused on the 60-mile (96.6-kilometer) Whillans Ice Stream, one of half a dozen streams feeding the Ross Ice Shelf, the world’s largest, about the size of the Canadian Yukon Territory.
Gustafson and her colleagues spent six weeks in 2018 mapping the sediments under the ice. The research team uses geophysical instruments placed directly on the surface to perform a technique called magnetotelluric imaging.
The technique can detect different degrees of electromagnetic energy conducted by ice, sediment, fresh water and salt water and create a map of these different sources of information.
“We imaged from the ice bed to about five kilometers (3.1 miles) and even deeper,” co-author Kerry Key, an associate professor of Earth and Environmental Sciences at Columbia University, said in a separate statement.
Researchers have calculated that if they manage to squeeze groundwater from sediments within 100 square kilometers (38.6 square miles) they have mapped to the surface, it will form a lake that ranges from 220 to 820 meters (722 to 2690 feet) deep. .
“The Empire State Building next to the antenna is about 420 meters (1,378 feet),” said Gustafson, who did the research as a graduate student at Columbia University’s Lamont-Doherty Observatory.
“At the shallow end of our water will go up to the Empire State Building about half. At the deepest end there are almost two Empire State Buildings stacked on top of each other. This is important because subglacial lakes in this area are two to 15 meters (6.6 to 49 feet) deep. It’s like one to four floors of the Empire State Building. “
How did you get there?
The mapping revealed that the water became saltier with depth, as a result of how the groundwater system formed.
Ocean water probably reached the area during the warm period 5,000 to 7,000 years ago, saturating the sediment with salty seawater. As the ice progresses, fresh molten water produced by top pressure and friction at the base of the ice is pushed into the upper sediments. It probably continues to be filtered and mixed into groundwater today, Kee said.
Researchers said more work needs to be done to understand the consequences of groundwater discovery, especially in the face of the climate crisis and rising sea levels.
It is possible that the slow flow of water from the ice into the sediment will prevent the accumulation of water at the base of the ice – acting as a brake on the movement of ice forward to the sea.
However, if the surface ice cap becomes thinner, reducing the pressure can allow this deep water to bend. This upward movement will crush the base of the ice and speed up its flow.
“This finding underscores groundwater hydrology as a potentially critical part of understanding the effect of water flow on Antarctic ice sheet dynamics,” said Winnie Chu, an assistant professor at the Georgia Institute of Technology, in a comment to the study. . She did not participate in the study.
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