A Giant Groundwater System Was Discovered in Sediment Below Antarctic Ice

Liquid water is key to understanding the function of the frozen form in glaciers. Melt water lubricates the gravelly bottoms of the glaciers, making it easier for them to move on land. During years of research in Antarctica, scientists have found hundreds of joint liquid lakes and rivers protected within the ice itself.

Photo: Wikimedia Commons/Rodrigoanfor

A research team imaged thick basins of sediments under the ice — which will probably be one of the biggest existing water reservoirs on the planet. Scientists are still doing research to prove the existence of large bodies of water below ice sediments, and they have yet to discover how liquid water can interact with the ice.

In West Antarctica, the research team mapped a massive and active flowing water system below deep sediments. This discovery even led them to another study — how does this affect climate change and the frozen continent? The research can be accessed in the journal Science.

“People have hypothesized that there could be deep groundwater in these sediments, but up to now, no one has done any detailed imaging,” said the study’s lead author, Chloe Gustafson, who participated in the research as a graduate student at Columbia University’s Lamont-Doherty Earth Observatory. “The amount of groundwater we found was so significant, it likely influences ice-stream processes. Now we have to find out more and figure out how to incorporate that into models.”

Photo: Youtube/k2geo

The Antarctic ice sheet has been under observation for decades. Scientists have sent equipment to image the surface. Through their mission, many discoveries were made, such as that of sedimentary basins between ice and bedrock. However, the findings were limited, as geophysics can only detect the rough outlines, not water contents.

In 2019, Antarctica’s McMurdo Dry Valleys utilized helicopter-borne instruments to record a few hundred meters of subglacial groundwater below over 350 meters of ice. However, the deeper water, with much thicker ice in Antarctica, can’t be reached by airborne instruments alone. For this reason, the team resorted to drilling into the ice sediment — but it was able to penetrate only the first few meters.

According to an article from Science Daily, “This is a big deficiency; most of Antarctica’s expansive sedimentary basins lie below current sea level, wedged between bedrock-bound land ice and floating marine ice shelves that fringe the continent.” Researchers think the sedimentary basins were formed on sea bottoms during warm periods during higher sea levels. Once these ice shelves draw back in a warming climate, ocean waters can quickly penetrate the sediments. As a result, glaciers behind could push forward and raise sea levels across the world.

Photo: Youtube/k2geo

In the new study, researchers focused on the 60-mile-wide Whillans Ice Stream — a fast-moving stream feeding the Ross Ice Shelf. An existing study revealed a subglacial lake within the ice, and a sedimentary basin can be found below the surface. Having drilled the first few feet of ice sediments has led to liquid water and microbes. However, revealing the first few feet of the cover is insufficient to indicate what still lies underneath the massive ice land.

In 2018, Chloe Gustafson, Lamont-Doherty geophysicist Kerry Key, Colorado School of Mines geophysicist Matthew Siegfried, and mountaineer Meghan Seifert landed on the Whillans via a U.S. Air Force LC-130 ski plane. The team was determined to map the ice sediments and their properties, and they would accomplish the mission using geophysical instruments on the surface.

The research was conducted with a technique called magnetotelluric imaging. Researchers were capable of measuring the penetration into the ice surface of natural electromagnetic energy in the atmosphere. They detected the remotely located ice, sediments, freshwater, salty water, and bedrock — which all impart electromagnetic energy. They compared the MRI-like maps of the various elements. Instruments were planted in snow pits and brought to four dozen locations.

Photo: Youtube/k2geo

One of the results of their observation concluded that the location is a huge factor in how sediments extend the ice surface from a half kilometer to nearly two kilometers before bedrock. If it were extracted, a water column with an estimate of 220 to 820 meters high may form within the ice base.

Key also shared that groundwater becomes even more saline with depth — as it can conduct more energy than freshwater.

“Ocean waters probably last reached what is now the area covered by the Whillans during a warm period some 5,000 to 7,000 years ago, saturating the sediments with saltwater. When the ice readvanced, fresh melt water produced by pressure from above and friction at the ice base was evidently forced into the upper sediments. It probably continues to filter down and mix in today,” said geophysicist Kerry Key.

The slow draining of freshwater into the sediments could prevent water formation at the base of the ice. Based on the results of measuring the ice stream’s grounding line, it is discovered that the existing water there is less salty than seawater, hence making freshwater flow through the sediments by the ocean, creating space for more meltwater to enter and keeping everything stable.

Photo: Youtube/k2geo

However, climate change is just around the corner, and the ice surface will get thinner in no time. As the earth warms up, it will change the water flow — the direction could even be reversed. As the pressure decreases, more groundwater will form at the base of the ice surface. The Whillans already moves forward a meter a day towards the sea, which is more than the usual speed.

“Ultimately, we don’t have great constraints on the permeability of the sediments or how fast the water would flow,” said Gustafson. “Would it make a big difference that would generate a runaway reaction? Or is groundwater a more minor player in the grand scheme of ice flow?”

Existing microbes in the shallow sediments are another issue to be solved by researchers. If groundwater continues to move upward, it will carry out the carbon used by these organisms. The increase of carbon on the surface will turn Antarctica into a large carbon source, adding up to what the planet is experiencing right now. The researchers who authored the study have yet to unfold the significant effect of the groundwater system below ice sediments on climate change. See how they conduct the research in an ice-cold land in the video below.

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