Hidden under kilometers of ice, very little is known about underground meltwater. However, how fast the ice sheet moves towards the sea plays an important role as it creates less friction between the ice and bedrock.
If the runoff leaks under the ice and comes in contact with warm seawater, it can also increase the melting of the ice and affect global sea levels, according to scientists.
The new study found that the melting rate at the bottom of the ice sheet was underestimated by 150 percent.
Analyzing a decade’s data from the European Space Agency’s (ESA )’s CyroSat satellite, experts were surprised to find that the lakes beneath the Thwaites Glacier – a huge frozen area the size of Great Britain – were drained and recharged in 2013 and in quick succession in 2017.
The study, carried out by researchers from Edinburgh, estimates that drainage speed peaked at around 500 cubic meters per second – about eight times faster than the speed of the Thames flowing into the North Sea.
We used CryoSat to display a period of sea activity just four years after the previous drainage event in 2013. The interesting thing about this second drainage event, however, is how different it is from the first, with faster water transfer and increased drainage. Our observations indicate that there may have been significant changes in the subglacial system between these two events.
Lead Author, School of GeoSciences, University of Edinburgh
The relatively short time it took to recharge the lakes between the two drainage events gives scientists an unprecedented estimate of the rate of melting at the bottom of the ice sheet.
When comparing the rates with modeled estimates, the team found that previous models underestimated the bottom melt by nearly 150 percent.
The result will help glaciologists reevaluate models and improve predictions about how the ice sheet might behave in the future.
What goes on under the ice sheet is critical to how it reacts to changes in the atmosphere and ocean around Antarctica, and yet it is hidden by miles of ice, making observation very difficult. This movement of the water gives us an insight into where the water is and how much and how fast it is moving across the system. Together, this is important information about the nature of the subglacial environment and the processes of the hydrological network under the ice sheet. These results provide vital information that we can use to project how the ice sheet will affect sea levels as it reacts to climate change.
Dr. Noel Gourmelen
Reader, School of GeoSciences, University of Edinburgh
Dr. Gourmelen added that it is important to monitor such remote regions from space over long periods of time. The proposed CRISTAL mission, which is part of the European Copernicus expansion program, will be vital to ensure the continuity and expansion of the current capabilities to study the entire ice sheet from space.
With a width of around 120 km, Thwaites is the largest glacier on earth and one of the most fragile in Antarctica.
The International Thwaites Glacier Collaboration and ESA’s 4D Antarctica programs were set up to continuously monitor the entire Antarctic ice sheet using ice sheet simulation and observations from space.
The project combines several years of research by various teams to create a new comprehensive assessment of the hydrological processes of the Antarctic ice sheet – from the lithosphere to the subglacial environment to the surface melting process. This will certainly help lay a solid scientific foundation for the future development of an Antarctic digital twin.
ESA Head of the Earth Observation Science Division overseeing the 4D Antarctic Project
The paper, published in Geophysical Research Letters, was funded by the European Space Agency’s 4DAntarctica project and the PROPHET project, part of the International Thwaites Glacier Collaboration (ITGC) supported by the US National Science Foundation and the UK Natural Environment Research Council.