We’ve “lost control” of West Antarctica

Rapid melt of the West Antarctic Ice Sheet may now be unavoidable.

THE MELTING of the West Antarctic Ice Sheet (WAIS) may now be “locked in,” according to a new analysis.

Previous research has estimated that complete collapse of the sheet will cause about five metres of global sea level rise over several centuries. Now, a study published in Nature Climate Change has found that ocean warming triggering this collapse is inevitable, even if the world meets the Paris Agreement target of 1.5°C of warming above pre-industrial levels.

“It looks like we’ve lost control of melting of the West Antarctic Ice Sheet,” says the study’s lead author Kaitlin Naughten, a researcher at the British Antarctic Survey.

“If we wanted to preserve it in its historical state, we would have needed action on climate change decades ago.

The WAIS has been losing mass for decades, driven by its interactions with the Southern Ocean, in particular the Amundsen Sea. Naughten and colleagues set out to investigate how the ice sheet’s melting will be affected as the Amundsen Sea warms up due to greenhouse gas emissions.

Using the UK’S national supercomputer, they modelled changes to the sea’s temperature under four different future emissions scenarios. The most ambitious was consistent with the Paris Agreement target of 1.5°C of warming. The team found that even under this best-case scenario the Amundsen Sea will warm three times faster this century than the historical rate. This will melt the WAIS’S floating ice shelves and allow the ice sheet behind to slide more rapidly into the ocean. The study suggests this will occur even if the world slashes emissions to slow warming.

“By recognising this situation in advance, the world will have more time to adapt to the sea-level rise that’s coming,” Naughten says.

“If you need to abandon or substantially re-engineer a coastal region, having 50 years lead time is going to make all the difference.”

“The new results in this paper suggest that the huge changes we’ve seen in the Amundsen Sea region are unlikely to be aberrations – they are glimpses into a future that we can no longer avoid,” says Edward Doddridge, a physical oceanographer from the University of Tasmania, who wasn’t involved in the research.

“It is confronting to think that five metres of sea level rise [are] already locked in. But we should not see this result as a reason to despair, rather as an urgent call to action.”

The majority of Antarctic ice is in the continent’s east, which holds more than 50 metres of sea-level rise.