Hidden under miles of thick ice, very little is known about ground-melting water, yet it plays an important role in how quickly the ice sheet moves toward the sea, as it creates less friction between the ice and the bedrock.
When the outflow comes out from under the ice and comes in contact with warm ocean waters, it also has the potential to increase ice melting 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 percent.
Experts have analyzed the value of a decade of data from the European Space Agency’s (ESA) CyroSat satellite, and were surprised that the lakes beneath Thwaites Glacier – a vast frozen expanse the size of Britain – emptied and recharged rapidly – in 2013 and in 2017.
The study, led by researchers in Edinburgh, estimates that the drainage speed peaked at about 500 cubic meters per second – about eight times faster than the speed of the 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 is interesting about this second drainage event is how it differs from the first, with faster water delivery and increased water outflow. Our observations highlight that there were possibly significant modifications to the subglacial system between these two events.
Lead author, School of Geosciences, University of Edinburgh
The relatively short time required to recharge the lakes between the two drainage events, gives scientists an unprecedented estimate of the rate of melting at the base of the ice sheet.
Comparing the rates to modeled estimates, the team found that previous models underestimated base fusion by nearly 150 percent.
The finding will help glaciologists reassess models and improve predictions about how the ice sheet might behave in the future.
What happens beneath the ice sheet is important as it reacts to changes in the atmosphere and ocean around Antarctica, and yet it is hidden from view by miles of ice, making it very difficult to observe. This movement of water gives us a glimpse of where the water is from and how and how fast it moves through the system. Together this is key information about 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 is added to sea level as it reacts to climate change.
Dr. Noel Gourmelen
Reader, School of Geosciences, University of Edinburgh
Dr. Gourmelen added that it is important to continue to monitor such remote areas of space for long periods of time. The planned CRISTAL mission, which is part of the European expansion program Copernicus, will be key to ensuring continuity and expansion of current capabilities to study all the ice from space, he said.
About 120 km wide, Thwaites is the largest glacier on Earth and one of the most delicate in Antarctica.
The International Thwaites Glacier Cooperation and ESA’s 4D Antarctic programs were created to continuously monitor the entire Antarctic ice rink by simulating the ice weather and observations from space.
The project brings together several years of research by different teams to form a new comprehensive assessment of Antarctic slide hydrological processes – from the lithosphere and subglacial environment to a surface melting process. This will certainly contribute to establishing a robust scientific basis for developing Digital Antarctic Gemini in the future.
Head of ESA Earth Observation Science Department – overseeing the 4D Antarctic project
The paper, published in Geophysical Research Letters, was funded by the European Space Agency’s 4DAntarctica project, and by the PROPHET project, part of the International Cooperation of Thwaites Glaciers (ITGC) supported by the US National Science Foundation and the Council on Natural Environmental Research of the United Kingdom.