The Antarctic Circumpolar Current is often described as the world's most powerful ocean current. Flowing uninterrupted around Antarctica, it helps isolate the continent from warmer waters, influences global climate patterns and plays a key role in the exchange of carbon between the ocean and atmosphere. But according to new research, this defining feature of the Southern Ocean did not emerge in the straightforward way scientists once imagined.
For decades, researchers believed the current formed largely because tectonic movements opened ocean gateways around Antarctica, creating a pathway for water to circulate around the continent. New simulations led by the Alfred Wegener Institute (AWI) and international modelling partners suggest the reality was considerably more complex.
Using coupled climate and ice-sheet models, the team found that the opening of seaways alone was not enough to establish a fully developed Antarctic Circumpolar Current. The models indicate that Australia's gradual separation from Antarctica was also critical. As the Tasman Gateway widened, it created conditions that allowed strong westerly winds to drive ocean circulation in new ways.
The research further suggests that the earliest version of the current was far from the continuous ocean ring seen today. Instead, circulation developed in stages, with regional flows that only later evolved into a complete circumpolar system.
The findings, published in Proceedings of the National Academy of Sciences (PNAS), provide new insight into one of the most significant turning points in Earth's climate history. The development of the Antarctic Circumpolar Current is closely linked to Antarctica's long-term cooling and the growth of the vast ice sheets that now cover the continent.
Beyond revising a chapter of Antarctic history, the study highlights how the interaction of continents, winds and oceans can reshape the global climate system. Understanding these past changes gives scientists a clearer picture of the processes that continue to influence climate and carbon cycling today.
Source: Alfred Wegener Institute (AWI) and international modelling partners, published in PNAS