Study by European Space Agency’s CryoSat scientistscould improve future sea level rise projections

“Subglacial hydrology is a missing piece in many ice sheet models. 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.” -- Sally Wilson, University of Leeds, UK, Lead Author of research published in NatureCommunications.

In a statement received by the European Space Agency, WATERTODAY learned that scientists have identified 85 previously unknown lakes hidden beneath Antarctica's ice using a decade's worth of satellite data. This increases the number of known subglacial lakes to 231.

Review by Suzanne Forcese

The newfound lakes are "active," meaning they periodically drain and refill, changing size and shape over months and years, the researchers said. This subglacial activity affects the stability of glaciers and their grinding movement over the Antarctic bedrock, which in turn could impact global sea levels, the team noted.

“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,” Anna Hogg, professor of Earth Observation, University of Leeds, U.K.

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.

How Do Subglacial Lakes 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.

Why Satellites Matter

“My PhD research involves investigating ice sheet surface height measurements from ESA’s CryoSat-2 satellite to identify and examine subglacial lakes in Antarctica. I also use SAR images from satellites such as Sentinel-1 to measure ice velocity, to assess the impacts of lake drainage events on ice dynamics,” Wilson said.

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.

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.”

Implications For Climate Modelling

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.”

Research: Detection of 85 new active subglacial lakes in Antarctica from a decade of CryoSat-2 data