a Surface elevation change from mid-2010 to mid-2020 over David 2 subglacial lake. The boundary delineated from the 2012 to late-2019 uplift event (black line) is shown alongside the corresponding gridded surface elevation change data in the background. The boundary delineated from the ICESat data10 is also illustrated (dashed grey line). b CryoSat-2 surface elevation change data from early-2017 to mid-2020 over the Institute E1 subglacial lake. The boundary delineated from this 2017—2020 surface subsidence event (dashed black line) is shown alongside boundaries from a previous period of surface uplift (early-2014 to late-2018) (solid black lines), and the subglacial lake boundary from the ICESat data10 (dashed grey line). The boundary of a smaller but distinct subglacial lake, named Institute_142 in our study, is located to the South of Institute E1, with boundaries for the 2017—2020 (dashed purple line) and 2014 to 2018 (solid purple line) events also shown. The North direction is indicated in both maps by the grey arrow. — Nature Communications
Hidden beneath the biggest ice mass on Earth, hundreds of subglacial lakes form a crucial part of Antarctica’s icy structure, affecting the movement and stability of glaciers, and consequentially influencing global sea level rise.
Thanks to a decade of data from the European Space Agency’s CryoSat satellite, researchers have identified 85 previously unknown lakes several kilometres under the frozen surface surrounding the South Pole. This increases the number of known active subglacial lakes below Antarctica by more than half to 231.
The research, published today in Nature Communications, is significant because active subglacial lakes, which drain and refill on a cyclical basis, offer a rare insight into what is happening far below the surface, at the base of the ice sheet. The research also identified new drainage pathways underneath the ice sheet, including five interconnected subglacial lake networks.
Lead author of the study, Sally Wilson, a doctoral researcher at the University of Leeds, explained that what we know about subglacial lakes and water flow is limited because they are buried under hundreds of metres of ice.
This map of subglacial lakes beneath the Antarctic ice sheet shows 85 lakes newly identified in a study published in Nature in September 2025. The data for this inventory comes from ESA’s CryoSat mission, which used its radar altimetry instrument to acquire data between 2010 and 2020. The purple shaded area around the continent’s margins is the area where CryoSat acquired data. Red triangles denote the newly discovered active subglacial lakes, while smaller pink triangles are active subglacial lakes that had previously been detected. The grey circles are previously known stable subglacial lakes. Glacier and Ice Stream names are abbreviated: Jutulstraumen Glacier (JG), Cook Glacier (CG), David Glacier (DG), Institute Ice Stream (IIS) and Recovery Glacier (RG). — ESA Larger image
“It is incredibly difficult to observe subglacial lake filling and draining events in these conditions, especially since they take several months or years to fill and drain. Only 36 complete cycles, from the start of subglacial filling through to the end of draining, had been observed worldwide before our study. We observed 12 more complete fill-drain events, bringing the total to 48.”
Why satellites matter
This is where satellites were able to contribute valuable data to the research. Observations from the CryoSat mission, which was launched in 2010, were able to produce a dataset spanning from 2010 to 2020.
ESA’s CryoSat satellite, part of ESA’s FutureEO programme, measures the thickness of polar sea ice and monitors changes in the height of ice sheets over Greenland and Antarctica and glaciers worldwide. Its main instrument is a radar altimeter, which can detect tiny variations in the height of the ice surface as well as measure sea surface height.
Using a decade of observations from CryoSat, researchers detected localised changes in the height of Antarctica’s icy surface, which rises and falls as the lakes fill and drain at the base of the ice sheet. They could then detect and map subglacial lakes and monitor their filling and draining cycles over time.
Anna Hogg, a co-author on the study and Professor at the University of Leeds, said, “It was fascinating to discover that the subglacial lake areas can change during different filling or draining cycles. This shows that Antarctic subglacial hydrology is much more dynamic than previously thought, so we must continue to monitor these lakes as they evolve in the future.”
Sally explained that observations like these are vital to understanding the structural dynamics of ice sheets and how they affect the ocean around them. “The numerical models we currently use to project the contribution of entire ice sheets to sea level rise do not include subglacial hydrology. These new datasets of subglacial lake locations, extents, and timeseries of change, will be used to develop our understanding of the processes driving water flow beneath Antarctica.”
Martin Wearing, ESA Polar Science Cluster Coordinator, noted, “This research again demonstrates the importance of data from the CryoSat mission to improve our understanding of polar regions and particularly the dynamics of ice sheets. The more we understand about the complex processes affecting the Antarctic Ice Sheet, including the flow of meltwater at the base of the ice sheet, the more accurately we will be able to project the extent of future sea level rise.”
Ice surface elevation changes from mid-2010 to mid-2020 over three subglacial lakes under Antarctica. Lake David 80 is shown on the left with a decrease ice surface elevation of 6 m during the study period. The subglacial lake known as David 2 on the right is associated with an increase in ice surface elevation of 8 metres. A smaller but distinct subglacial lake, named David 180, is located below these, also registering a decreased elevation. — ESA Larger image
How does a subglacial lake form?
Subglacial meltwater forms due to geothermal heat from Earth’s bedrock surface and frictional heat as ice slides over bedrock. This meltwater can pool on the bedrock surface, and periodically drains. This flow of water has the potential to reduce the friction between the ice and the bedrock it sits on, allowing ice to slide more quickly into the ocean.
Not all subglacial lakes are considered active – many are thought to be stable because they are not known to fill or drain. The biggest known subglacial lake is Lake Vostok underneath the East Antarctic Ice Sheet, holding an estimated 5000–65 000 cubic km of water beneath 4 km of ice (the water contained in Lake Vostok is enough to fill the Grand Canyon and overflow by at least 25 %). Although Lake Vostok is thought to be stable, if it did drain, it would impact on the stability of the Antarctic Ice Sheet, surrounding ocean circulation and marine habitats, and global sea level.
Implications for climate modelling
The filling-and-draining cycles of subglacial lakes are an important dataset for icesheet and climate models. By monitoring such phenomena, scientists can improve their understanding of interactions between the ice sheet, bedrock, ocean and atmosphere, which is key to understanding the future stability of ice sheets.
“Subglacial hydrology is a missing piece in many ice sheet models,” said Sally. “By mapping where and when these lakes are active, we can start to quantify their impact on ice dynamics and improve projections of future sea level rise.”
Detection of 85 new active subglacial lakes in Antarctica from a decade of CryoSat-2 data, Nature Communications, (open access)
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