Study shows increased West Antarctic Ice Sheet melting is 'unavoidable'

Increased West Antarctic Ice Sheet melting is “unavoidable,” according to a new study by the British Antarctic Survey (BAS) published in the Nature Climate Change journal.

In fact, the researchers predict that the West Antarctic Ice Sheet will continue to increase its rate of melting over the rest of the century, no matter how much we reduce fossil fuel use.

Collectively the West Antarctic Ice Sheet contains enough ice to raise global mean sea level by up to five metres, submerging major cities from New York to Mumbai and Shanghai.

A substantial acceleration in ice melting likely cannot now be avoided, which implies that Antarctica’s contribution to sea level rise could increase rapidly over the coming decades, they said.

The scientists ran simulations on the UK’s national supercomputer. Taking into account climate variability such as El Nino, they found no significant difference between mid-range emissions scenarios and the most ambitious targets of the 2015 Paris Agreement. Even under a best-case scenario of a 1.5 degrees C global temperature rise, melting will increase three times faster than during the 20th century.

The West Antarctic Ice Sheet is losing ice and is Antarctica’s largest contributor to sea-level rise. Previous modelling finds this loss could be driven by warming of the Southern Ocean, particularly in the region of the Amundsen Sea.

“It looks like we’ve lost control of the melting of the West Antarctic Ice Sheet,” said lead author Kaitlin Naughten, a researcher at the BAS. “If we wanted to preserve it in its historical state, we would have needed action on climate change decades ago.

“The bright side is that by recognising this situation in advance, the world will have more time to adapt to the sea level rise that’s coming. 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 team simulated four future scenarios of the 21st century, plus one historical scenario of the 20th century. The future scenarios either stabilised global temperature rise at the targets set out by the Paris Agreement, 1.5 degrees C and 2 degrees C, or followed standard scenarios for medium and high carbon emissions.

All scenarios resulted in significant and widespread future warming of the Amundsen Sea and increased melting of its ice-shelves. The three lower-range scenarios followed nearly identical pathways over the 21st century. Even under the best-case scenario, warming of the Amundsen Sea sped up by about a factor of three, and melting of the floating ice shelves which stabilise the inland glaciers followed, though it did begin to flatten by the end of the century.

This study presents sobering future projections of Amundsen Sea ice-shelf melting but does not undermine the importance of mitigation in limiting the impacts of climate change.

“We must not stop working to reduce our dependence on fossil fuels,” Naughten cautions. “What we do now will help to slow the rate of sea level rise in the long term. The slower the sea level changes, the easier it will be for governments and society to adapt to, even if it can’t be stopped.”