September 30, 2022
Chicago 12, Melborne City, USA
Tech

A Vast Underground Water System Helps Drive Antarctica’s Glaciers

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Lake Whillans is Water is a strange body, starting from the fact that there is fluid to fill it. Although the Antarctic ice is crushed more than 2,000 feet below, its temperature rises to only 0 degrees Celsius, thanks to the combination of geothermal warmth, intense friction from ice scraping rocks and that dense glacier blanket protecting it from polar winds. Due to the high pressure there, it is smooth enough to hold the lake water. Still unfamiliar, Lake Huilans blends in with life. A study a decade ago found thousands of types of microscopic craters that were thought to be feeding off the remaining nutrients in seawater that had descended into the basin a few millennia ago, when glaciers last pulled.

Most recently, Chloe Gustafson, a geophysicist at the Scripps Institution of Oceanography, arrived at a remote iceberg on Lake Huilans with a different mystery head in mind: What’s going on beneath the lake? Antarctic researchers have long suspected that the depth of the river beneath the glaciers was much deeper than they could see. This will have an impact on how the ice on any groundwater at the bottom of the lake moves toward the ocean and thus can contribute to the rapid growth of the ocean. But they could not prove for sure what the groundwater was. It was too deep, too covered in ice to map with traditional glacial equipment, such as bouncing radar signals from ice or setting off explosives and listening to shockwaves.

In a study published in the journal Science, Gustafson’s team offers a long-awaited plan for an underwater world under ice. A vast body of groundwater has reached more than one kilometer below the characteristics of subglacial water, such as Lake Huilans, which contains 10 times more water. To see this, researchers focus on a technique called magnetotelurics, or MT, which uses natural variations of the earth’s electromagnetic field to sketch a detailed picture of the sediment below. They expect similar groundwater systems based on other regions where ice flows faster – so-called ice currents account for about 90 percent of the ice in the oceans from within the continent. “It’s part of the puzzle asking why this ice is flowing,” Gustafsson said. “So it’s really important to understand what’s going on in Antarctica.”

Scientists have long understood that subglacial water plays a role in how ice moves to the surface. One reason is how it changes the sediments below, creating rats and planes in the terrain. Another is the lubrication of the soil, which allows the ice to slide faster. “If you have water on your slip n slide, you’re going to slide very fast,” Gustafson said. “If you don’t have water, you can’t go very far.” Creating the concept of that subglacial hydrology is especially important for researchers to create models of particularly precarious regions of ice, such as the Twitt’s Glacier, hundreds of miles from Wheylans. In January, a team of researchers reported that the Thwaites – the so-called Doomsday Glacier, which contains enough ice to raise global sea levels by 2 feet – could collapse in five years.

But those models are incomplete without groundwater. Slavek Tulakzik, a professor of Earth Sciences at UC Santa Cruz, said he had studied the region but was not involved in the study, and researchers had long observed that the expected amount of water was coming out of the bottom of the Huilans ice stream. This was weird. As the ice sheets get closer to the ocean they become thinner and thus less good to insulate the land from the cold Antarctic winds. At these ends, the water should slow down the ice, tending to freeze. But that was not what the ice scientists were seeing. “It was a puzzle,” he says. Somehow, the patterns they observed “failed thermodynamics.” The researchers estimated that about half of that water must have come from underground mapped sources.

Gustafsson’s team mapped it out. The ice on the top of Lake Huilans is in the western part of the Antarctic, at the foot of a mere transatlantic peak dividing the continent. The region favored scientists conducting research in the pre-GPS era because those mountains helped navigate. But it’s remote. “It was the longest, most difficult camping trip of my life,” said Gustafson, who spent weeks wandering around in the snow and ice, digging holes where the team would leave devices that passively listen to electromagnetic signals. The instruments will remain there for 24 hours before researchers dig them up and take them to the next site two kilometers away.

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