Hidden under miles of thick ice, very little is known about subsoil meltwater, but it plays an important role in how quickly the ice sheet moves towards the sea, as it creates less friction between the ice and bedrock.
When runoff comes out from under the ice and comes into contact with warm ocean waters, it also has the potential to increase ice melt and affect global sea levels, according to scientists.
The new study found that the rate of melting at the base of the ice sheet was underestimated by 150%.
Experts analyzed a decade’s worth of data from the European Space Agency’s (ESA) CyroSat satellite and were surprised to find that the lakes beneath Thwaites Glacier – a vast expanse of ice the size of Britain – dried up and recharged by new in quick succession – in 2013 and 2017.
The study, conducted by the Edinburgh researchers, estimates that drainage speeds peaked at around 500 cubic meters per second, about eight times faster than the speed of the River Thames as it flows into the North Sea.
We used CryoSat to show a period of lake activity just four years after the previous drainage event in 2013. But what’s interesting about this second drainage event is how different it is from the first, with faster water transfer and increased water discharge. Our observations highlight that there were potentially significant changes to 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 melting rate at the base of the ice sheet.
Comparing the rates to the modeled estimates, the team found that previous models underestimated baseline fusion by nearly 150%.
The discovery will help glaciologists re-evaluate models and improve predictions about how the ice sheet might behave in the future.
What happens beneath the ice sheet is critical to how it responds to changes in the atmosphere and ocean around Antarctica, yet it’s hidden from view by miles of ice making it very difficult to observe. This movement of the water gives us an idea of where the water is and how much and how fast it moves through the system. Together, these are key insights into the nature of the subglacial environment and the processes of the hydrological network beneath the ice sheet. These findings provide key information that can help us project how the ice sheet adds to sea level as it responds to climate change.
Dr Noel Gourmelen
Lecturer, School of GeoSciences, University of Edinburgh
Dr Gourmelen added that it is important to continue monitoring such remote regions from space for long periods of time. The planned CRISTAL mission, which is part of the Copernicus European expansion program, will be crucial to ensure the continuity and expansion of current capabilities to study the entire ice sheet from space, he said.
With a width of around 120 km, Thwaites is the largest glacier on Earth and one of the most fragile in Antarctica.
ESA’s International Thwaites Glacier Collaboration and 4D Antarctica programs were established to continuously monitor the entire Antarctic ice sheet using ice sheet simulation and observations from space.
The project brings together several years of research from different teams to form a comprehensive new assessment of the hydrological processes of the Antarctic ice sheet, from the lithosphere and subglacial environment to the surface melting process. This will certainly help establish a solid scientific basis for developing a digital twin of Antarctica in the future.
Head of ESA’s Earth Observation Science Section, overseeing the 4D Antarctica project
The paper, published in Geophysical Research Letters, was funded by the European Space Agency’s 4DAntarctica project and the PROPHET project, a component of the International Thwaites Glacier Collaboration (ITGC) supported by the US National Science Foundation and the UK Natural Environment Research Council.