Ocean circulation in the deep waters around Antarctica has slowed significantly over the past three decades, posing a threat to the climate system, according to a new study.
Ocean circulation has kept climate change in check by drawing heat from the sea surface down to its depths. As polar waters freeze, they expel salt, causing surrounding waters to grow more saline — and thus, heavier — and sink to the ocean floor. But rising temperatures are increasingly melting polar ice, disrupting this process.
Scientists have long warned that warming could cause a collapse in circulation in the North Atlantic, but recent modeling finds the feared breakdown will more likely come in the Southern Ocean. The new study gives added added weight to these projections, with observational data showing that from 1994 to 2017, deep water circulation in the Australian–Antarctic basin slowed by around 30 percent. The findings were published in the journal Nature Climate Change.
Until now, scientists had only “limited observations of this remote and extreme environment,” said Ariaan Purich, a climate scientist at Monash University, in Australia, who was not affiliated with the study.
The new observational data brings much needed clarity, showing that ocean flows around Antarctica have “dwindled since the early 1990s,” Sorbonne oceanographer Casimir de Lavergne, who was also unaffiliated with the study, wrote in a comment on the research. The findings indicate that future ice loss may “stifle” Antarctic circulation, he added, underscoring the need for more research on the Southern Ocean.