The planet's largest current
The Drake Passage is an 800-kilometer-wide (500 mi) strait between South America's Cape Horn and Antarctica's South Shetland Islands. It is the shortest route from Antarctica to any other landmass. Its primary feature is the Antarctic Circumpolar Current (ACC), the largest ocean current on Earth. The ACC flows from west to east, connecting the Pacific, Atlantic, and Indian Oceans and allowing them to exchange water, heat, and salt. The current's volume is immense, with recent measurements in the Drake Passage showing a mean transport of 173.3 Sverdrups (million cubic meters per second). This flow is more than 100 times that of all the world's rivers combined.
This uninterrupted circumpolar flow exists because no landmass connects to Antarctica, which keeps warmer ocean waters away and helps the continent maintain its massive ice sheet. The formation of the Drake Passage began between 30 and 50 million years ago, as South America and Antarctica separated. This geological event triggered a major global cooling and the expansion of the Antarctic ice sheets, as the newly formed ACC thermally isolated the continent.
A turbulent mixing machine
The powerful westerly winds, known as the "Roaring Forties" and "Furious Fifties," drive the Antarctic Circumpolar Current. With no land to block them, these winds transfer enormous energy to the ocean surface. This energy doesn't just push the water in a smooth loop. Instead, it powers intense mixing that extends to the ocean floor, which has an average depth of about 3,400 meters (11,000 feet).
The mixing process is complex. The ACC is not a single stream but is composed of several distinct jets, or fronts, including the Subantarctic Front and the Polar Front. The current's interaction with the rough seafloor topography, which includes features like the Shackleton Fracture Zone, generates turbulence and internal waves. This turbulence creates large, swirling eddies (the oceanic equivalent of storms)that spin off from the main current. Eddies are critical for moving heat and nutrients vertically, bringing cold, nutrient-rich deep water toward the surface and pulling warmer surface water down. This vertical exchange makes the region productive, supporting a diverse marine ecosystem. This intense mixing also makes the Drake Passage an area for the ocean's absorption of atmospheric carbon dioxide.