Novel modelling links sea ice loss to Antarctic ice shelf calving events

(Press-News.org) New research has for the first time tracked ice shelf, sea ice and ocean swell wave conditions over multiple years in the lead-ups to three large-scale iceberg ‘calving’ events in Antarctica, revealing common patterns.

Published in Nature Geoscience, the study, led by the Universities of Melbourne and Adelaide, found long periods of sea ice loss surrounding the ice shelves in the six to 18 months prior to calving, as well as the collapse of the ‘landfast’ sea ice attached to the ice shelves only weeks prior to the calving events.

University of Melbourne Professor Luke Bennetts explained that the researchers also developed a novel mathematical model to quantify the ice shelf flexing caused by the huge Southern Ocean swells.

“Sea ice is retreating at an unprecedented rate all around Antarctica and our work suggests this will put further pressure on already thinned and weakened ice shelves,” Professor Bennetts said.

“This could lead to more large-scale calving events, with profound implications for the future of global sea levels.”

The Antarctic Ice Sheet is the thick layer of ice that sits on top of Antarctica. It holds enough fresh water to raise current sea levels by over 50 metres.

Ice shelves are floating platforms formed as glaciers flow off the Antarctic continent onto the ocean, whereas sea ice forms when the surface of the ocean freezes.

“Except for a relatively short period around summer, sea ice creates a protective barrier between the ice shelves and the potentially damaging swells of the Southern Ocean,” Professor Bennetts said.

“Without this barrier, the swells can bend and flex pre-weakened ice shelves until they break.”

Professor Bennetts said previous research has shown that warming temperatures are causing more rapid melting and more frequent ‘calving’ of icebergs from some ice shelves.

“Increased melting and calving does not directly increase sea levels as the ice shelves are already floating on the ocean, but it reduces the ability of the ice shelves to push back against the glacial flow into the ocean – which does raise sea levels,” he said.

There is currently no observation system for routinely recording ocean waves in Antarctic sea ice and ice shelves, so mathematical modelling is essential to quantify the connection between the observed ocean swells, sea ice conditions and the response of the ice shelves.

The research was funded by the Australian Antarctic Science Program and the Australian Research Council and collaborators included the University of Melbourne, the University of Adelaide, the Australian Bureau of Meteorology, the University of Tasmania, and the Australian Antarctic Division.

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