Melting Antarctic ice is projected to slow the world's strongest ocean current by 20% by 2050 under a high emissions future, according to an Australian-led study. The Antarctic Circumpolar Current, which is more than four times stronger than the Gulf Stream and links the Atlantic, Pacific and Indian oceans, plays a critical role in regulating the climate by absorbing heat and carbon dioxide and preventing warmer waters from reaching Antarctica.
Using Australia's fastest supercomputer, Gadi, researchers modelled the impact of changing temperature, ice melt and wind conditions on the current. The findings, published in Environmental Research Letters, show a clear link between meltwater from Antarctic ice shelves and a slowdown of the current, which could further accelerate ice sheet melting and sea level rise.
Co-author Associate Professor Bishakhdatta Gayen from the University of Melbourne described the result as “quite alarming”. He explained that cold, fresh water from melting ice sinks and spreads towards the equator, altering ocean density and weakening the current. “If this current ‘engine’ breaks down, there could be severe consequences, including more climate variability and accelerated global warming due to reduced carbon uptake,” he said.
Climate scientist Dr Taimoor Sohail warned of a “vicious cycle” where a weaker current allows more warm water to reach Antarctica, increasing ice melt and further slowing the current. This could also disrupt marine ecosystems by allowing invasive species to reach the continent. However, he noted that “concerted efforts to limit global warming by reducing carbon emissions will limit Antarctic ice melting, averting the projected slowdown.”
Dr Edward Doddridge, a physical oceanographer at the University of Tasmania not involved in the study, called the findings significant and surprising, given previous studies suggested parts of the current were accelerating. He emphasised the importance of understanding ocean current changes, as oceans store over 90% of Earth's extra heat and redistribute it globally.
Monash University climate scientist Dr Ariaan Purich, also not involved, said dramatic changes are already occurring around Antarctica, with sea ice extent dropping below 2 million square kilometres every summer since 2022. “We need to know what the ocean is doing to better project the climate we experience on land and adapt accordingly,” she said.
