Widening Channels and Westerly Winds Combine to Form Earth’s Strongest Current

The Antarctic Circumpolar Current (ACC), the world’s strongest ocean current, formed through a combination of widening ocean passages and strengthening westerly winds, according to new climate simulations published in April 2026. The research, conducted by scientists at the Alfred Wegener Institute in Germany, reveals that the ACC did not begin flowing simply because tectonic movements opened gateways between Antarctica, Australia, and South America. Instead, a critical threshold was reached only when the Tasman Gateway widened sufficiently to allow strong, sustained westerly winds to blow directly through it, driving the current’s full development.

The ACC, which flows clockwise around Antarctica, carries more than 100 times the combined flow of all the world’s rivers and is five times stronger than the Gulf Stream. It plays a central role in Earth’s climate system by connecting major ocean basins and facilitating the global distribution of heat, and nutrients. Despite its influence, the current has remained relatively understudied due to its location in the remote southern oceans.

To investigate the ACC’s origins, researchers ran climate simulations modeling Earth as it existed approximately 33.5 million years ago, near the estimated time of the current’s initiation. These simulations showed that while the drifting of continents created the necessary oceanic passages, the presence of strong westerly winds in the middle latitudes was equally essential. Only when both conditions coincided — widened channels and persistent wind forcing — did the simulations produce a current matching the ACC’s observed strength and structure.

“There were already indications that the wind in the Tasman Gateway played an important role in the formation of the ACC,” said Hanna Knahl, a climate modeler at the Alfred Wegener Institute. “Our simulations can clearly confirm this: Only when Australia had moved further away from Antarctica and the strong westerly winds blew directly through the Tasman Gateway, the current could fully develop.”

The Tasman Gateway, the oceanic passage between Antarctica and the southern coast of Australia, served as a critical conduit for these winds. As Australia drifted northward, the widening of this gateway allowed the wind-driven surface stresses to transmit more effectively into the ocean, initiating the eastward flow that defines the ACC. The study emphasizes that neither tectonic opening nor wind intensification alone was sufficient; their combination was required to overcome the ocean’s inertia and establish the current.

This finding refines previous theories that attributed the ACC’s formation primarily to continental drift. By demonstrating the interdependence of geological and atmospheric factors, the research highlights the complexity of ocean circulation development in response to Earth’s evolving climate and geography. It also underscores the sensitivity of major ocean currents to changes in wind patterns, a consideration relevant to understanding potential future shifts in the ACC under ongoing climate change.

The ACC’s strength and stability influence global weather patterns, marine ecosystems, and the ocean’s capacity to absorb carbon and heat. Changes in its behavior could have far-reaching consequences for climate regulation, particularly in the Southern Hemisphere. While the current remains stable today, the study provides a framework for assessing how alterations in wind systems or ocean gateways might affect its future dynamics.

The research contributes to a growing body of work using paleoclimate modeling to understand the long-term evolution of Earth’s ocean systems. By linking tectonic movements, wind dynamics, and ocean circulation, scientists can better reconstruct past climate states and improve projections of future changes. The ACC, as a key component of the global ocean conveyor belt, continues to be a focal point for studies seeking to understand the interconnected drivers of planetary climate.