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Antarctica may seem like a static environment: a motionless white landscape frozen in place.
But there’s a lot more going on under the ice than we realize – although you have to travel to space to be sure.
More than a decade ago, scientists made such a discovery, when an analysis of data from NASA’s ICESat satellite found that variations in ice elevation in West Antarctica reflected a vast mass of movement. of subglacial water under the ice cap.
Before the discovery, it was believed that the hidden meltwater lakes – deeply hidden at the bottom of the ice cap, where the ice meets the continental bedrock below – existed in isolation, cut off from each other.
But in 2007, researchers found that fluctuations in the height of Antarctic surface ice meant the movement of water flowing between a hidden network of subglacial lakes, which alternately fill and empty. before their water escapes into the Southern Ocean.
The new lakes discovered. (Siegfried et al./NASA Goddard / YouTube)
Now, the monitoring of the ICESat mission – ICESat-2, launched in 2018 – gives scientists an even more precise insight into this mysterious network of deeply buried lakes, while revealing two lakes never before discovered.
“The discovery of these interconnected systems of lakes at the interface of the ice bed that move water, with all these impacts on glaciology, microbiology and oceanography – it was a great discovery of the ICESat mission”, said glaciologist Matthew Siegfried of the Colorado School of Mines.
“ICESat-2 is like putting on your goggles after using ICESat, the data is so precise that we can really start to draw the lake’s boundaries on the surface.”
In a new study, Siegfried and other researchers compiled elevation data from ICESat-2 and the original ICESat mission, as well as measurements taken by CryoSat-2, an ice observing satellite operated by the European Space Agency (ESA).
By combining the datasets – spanning the period 2003 to 2020 – researchers are able to monitor active subglacial lakes at timescales shorter than the ICESat-2 repeat cycle (the interval of 91 days before he could observe the same region again).
“Surface deformation due to the filling and drainage of active subglacial lakes provides one of the few remotely accessible windows into the evolution of base water systems; these systems are otherwise hidden under up to 4 km [2.5 miles] of ice and remains one of the main physical uncertainties in projections of the future dynamics of the ice sheet, ”the researchers write in their paper.
“ICESat-2 laser altimetry can not only extend the recording of subglacial lake activity, but also provide insight into hydrological processes by capturing denser and more precise spatial details. “
In addition to giving us a more detailed look at the activity and contours of Antarctica’s known subglacial lakes – of which more than 130 are already documented – the analysis revealed two anomalies that appear to be hidden lakes, no. previously detected.
These potentially active lakes, referred to as Lower Conway Subglacial Lake (LSLC) and Lower Mercer Subglacial Lake (LSLM), lie in close proximity to previously discovered lakes and may have been missed by the original ICESat mission, located in the narrow gaps between his observations.
In this region – beneath the ice streams Mercer and Whillans in West Antarctica – the lake system, which is dominated by two large active subglacial lakes (the subglacial Lake Conway and the subglacial Lake Mercer), appears be in the midst of its third drainage event since ICESat observations began in 2003.
Just a few weeks ago, one of the same researchers involved here – glaciologist Helen Fricker of the Scripps Institution of Oceanography – co-authored a related study, detailing a dramatic lake drainage event in Antarctica. eastern, where a surface lake on a floating ice shelf vanished within days.
Far beneath the West Antarctic ice cap, it is also believed that water draining from subglacial lakes will eventually flow into the ocean, although the hidden escape route is much more difficult to visualize. .
“These are processes that take place under Antarctica that we would have no idea about if we didn’t have satellite data,” says Fricker.
“We have struggled to get good predictions about the future of Antarctica, and instruments like ICESat-2 are helping us to observe at the scale of the process.”
The results are reported in Geophysical research letters.
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