Science

A third of Antarctic ice shelves risk collapsing due to climate change

The Larsen C ice shelf on the east of the Antarctic Peninsula

NASA ICE

Around a third of the ice shelves holding back huge glaciers in Antarctica are at risk of collapse if the world fails to take sufficient action on climate change, new projections have found.

The ice shelves circling the continent are vulnerable to meltwater on their surface causing the ice to crack and disintegrate, a process known as hydrofracturing.

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Computer modelling by Ella Gilbert at the University of Reading, UK, and Christoph Kittel at the University of Liege, Belgium, showed that if the world warms by 4°C since pre-industrial levels, then 34 per cent of the continent’s ice shelves will have meltwater on their surface, a sign they are at risk of collapse.

However, the figure falls to 18 per cent if temperature rises are checked at 2°C. The world is currently on track for a 2.9°C rise but, if implemented, climate plans and net zero goals would cut that to 2.1°C.

“Warming to 2°C means half the ice shelf area is at risk of collapsing. That is the message: the less the warming the better,” says Gilbert.

She and Kittel used a much higher resolution climate model than previous research, with grid squares 35 kilometres across rather than hundreds of kilometres across. It also more accurately represents cloud physics, which is vital as estimates of the area at risk of collapse hinge on how much ice loss is replaced by snowfall. The big difference between the 2°C and 4°C rise scenarios stems from melting outweighing increased snowfall in a 4°C warmer world.

The Larsen C ice shelf on the east of the Antarctic Peninsula, where a huge iceberg broke off in 2017, was found to be one of the areas most at risk.

“This study shows melting at the ice shelves’ surface will spreads southwards to parts of the continent where huge reservoirs of inland ice may lose their protective barrier. If that happens, we can expect rapid increases in sea level rise along every coastline of our planet,” says Andrew Shepherd at the University of Leeds, UK, who wasn’t involved with the paper.

The research doesn’t put a figure on how much sea level rise could occur if ice shelves collapsed and released the glaciers behind them. However, Gilbert says: “My gut feeling is for 4°C it could potentially contribute tens of centimetres if they did collapse.” Avoiding 10 centimetres of sea level rise should expose 10 million fewer people globally to flooding risks.

Helene Seroussi at NASA’s Jet Propulsion Lab, who wasn’t part of the research team, says the study’s big advance is using a higher resolution model. While the research identifies ice shelves that could be hydrofractured, Seroussi says further analysis of how individual ice shelves move – the “dynamical stress regime” – is needed to work out which ones will actually collapse.

Journal reference: Geophysical Research Letters, DOI: 10.1029/2020GL091733

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