CryoSat reveals ice erosion from underneath Antarctica

The place where a glacier’s base leaves the seabed and begins to float is known as the grounding line. This maps shows ground line migration around Antartica between 2010 and 2016 (CPOM)

3 April 2018

The European Space Agency’s CryoSat mission has helped scientists reveal startling underwater ice loses beneath Antartica’s great ice sheet where it’s impossible to access by submersibles. In a paper published this week in Nature Geoscience, researchers at the Centre for Polar Observation Modelling at the UK’s University of Leeds show that, over the last seven years, an area the size of Greater London (1,463m2) has been eroded away at the base of the continental ice shelf by warm southern ocean waters circulating beneath.

The research team, led by Dr Hannes Konrad, used CryoSat-2 to track the 16,000km continental coastline and produced the first complete map of how the ice sheet’s submarine edge is shifting. Although CryoSat-2 is designed to measure changes in ice sheet elevation, the team were able to calculate what was happening at the base using knowledge of the glacier and sea floor geometry and the Archimedes principle of buoyancy – which relates the thickness of floating ice to the height of its surface.

By measuring changes in surface elevation using ESA’s CryoSat-2, the retreat of glacier ground lines can be calculated (CPOM)

Said Dr Konrad: “Our study provides clear evidence that retreat is happening across the ice sheet due to ocean melting at its base.” He said the retreat was also having a huge impact on inland glaciers, “because releasing them from the sea bed removes friction, causing them to speed up and contribute to global sea level rise.”

The biggest changes among Antartic’s 65 biggest glaciers were seen in West Antarctica, where more than a fifth of the ice sheet has retreated across the sea floor faster than the pace of deglaciation. However, at the neighbouring Pine Island Glacier – until recently one of the fastest retreating on the continent – it has halted, revealing the complexity of ice sheet instability across the continent.