Beneath the thick ice sheet that forms West Antarctica lies a colossal body of water, connected with a multitude of underwater rivers and lakes. Scientists have studied with empirical evidence, for the first time, these types of systems that exist in the depths of the frozen continent. knowing them is key to shedding light on the behavior of Antarctic glaciers and their melting.
A team of researchers from the Scripps Institution of Oceanography has been the first to map the secret that lies beneath the Antarctic ice sheets, and has published its results in the journal Science.
Scientists have been flying over the Antarctic ice sheet for decades with radar and other instruments to image subsurface features; but always with poor results. These missions demonstrated that there were sedimentary basins interbedded between ice and bedrock, but were unable to estimate water content or other features.. The evidence was there, but out of reach of the human hand.
However, this group of scientists has now unveiled this mystery. The researchers went to the western part of Antarctica, specifically to the area near the Whillans Current, which is about 800 meters thick and a hundred kilometers wide and feeds the Ross Ice Shelf, considered the largest in the world. They knew that by studying this place with the right tools, they would succeed. And it is that previous studies in the place had revealed that there is a subglacial lake under the ice and a sedimentary basin that extends below it. A few years ago, the outermost layer of the ice was drilled and liquid water and a thriving community of microbes were found. But what lay below remained a mystery.
The team used the magnetotelluric method, which measures the penetration of natural electromagnetic energy generated in the planet’s atmosphere into the earth, to obtain images of what was in the depths of Antarctica. Because ice, seafloor sediments, freshwater, saltwater, and bedrock all emit different degrees of electromagnetic energy, so you can measure the differences in these frequencies to create maps just as you would. an MRI.
Key to the behavior of glaciers
“The amount of groundwater we found was so significant that it likely influences ice-flow processes.. Now we need to find out more and figure out how to incorporate that into the models,” says study lead author Chloe Gustafson. Many scientists say that liquid water is key to understanding the behavior of the frozen form found in glaciers, considering that melt water lubricates the gravel and accelerates its movement towards the sea.
In addition, these magnetotelluric signals gave researchers insight into groundwater characteristics, “because freshwater shows up very differently in our images than saltwater,” Gustafson said.
In a second part of the investigation, the measurements were complemented with data from seismic images collected by Paul Winberry of Central Washington University, a co-author of the study. The analysis showed that, depending on the location, the sediment layer under the ice is more or less thick, from half a kilometer to almost two kilometers before reaching bedrock. With all the water it contains, a lake 220 to 820 meters deep could be formed.
What effects these underwater lakes may have on the marine dynamics of the frozen continent is unknown, but researchers have begun to consider some of them. It is believed that if ice shelves were to melt due to global warming, ocean waters could re-invade sediments and glaciers would risk raising global sea levels much higher than estimated .
The existence of subglacial groundwater also has implications for the carbon stored by communities of microbes adapted to seawater and could release “significant amounts” of this gas that until now had not been considered.
And also a lake as big as the island of La Gomera
Another different study, published in the journal Geology, has made it possible to discover under three kilometers of ice in East Antarctica, specifically in the Land of Princess Elizabeth, a lake of 370 square kilometers (the same as the island of La Gomera) and that contains a volume of liquid water of 21 cubic kilometers.
Analyzing this and other recently discovered subglacial lakes, as well as the sediments they have at the bottom, you can learn the history of the ice sheet from its earliest beginningspoint out the scientists from the University of Texas who are the authors of the research.
Specifically, it is about solving what Antarctica was like before it froze, how climate change has affected it since the beginning of its history and how current global warming is affecting it. The lake could keep a record of the ice cover of the last 34 million years.
Reference study: https://www.science.org/doi/10.1126/science.abm3301
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