Ocean currents are continuous, directed movements of ocean water. These vast systems are driven by wind, differences in water temperature and salinity, and the Earth’s rotation. They play an important role in distributing heat from the equator towards the poles and cold water back towards the equator, influencing global weather patterns and marine life. Understanding these dynamic features helps explain the ocean’s complex system.
The World’s Largest Ocean Current
The Antarctic Circumpolar Current (ACC) is the world’s largest ocean current. Its immense scale is measured by its volume transport, expressed in Sverdrups (Sv), where one Sverdrup equals one million cubic meters of water per second. The ACC’s mean transport is estimated at 137 ± 7 Sverdrups, though some studies indicate it can reach 173.3 Sverdrups through the Drake Passage. The ACC transports more than 100 times the combined flow of all the world’s rivers, making it significantly larger than other major currents like the Gulf Stream, which transports approximately 30 Sverdrups.
Defining Features of the Antarctic Circumpolar Current
The ACC’s large volume transport results from its unique physical attributes. It is the only ocean current that flows eastward around the globe, encircling the Antarctic continent. This continuous, unimpeded flow is possible because no landmasses connect Antarctica to other continents at these latitudes. The current extends from the ocean surface to the seafloor, reaching depths of up to 4,000 meters (over 2.5 miles).
Its width is considerable, spanning hundreds of kilometers and sometimes reaching 2,000 kilometers (1,243 miles) across. While its average speed is modest, ranging from 10 to 50 centimeters per second, it can reach 2 knots (3.7 kilometers per hour) in certain areas. The sheer volume of water moved by the ACC results from its extensive depth and width, rather than exceptionally high speeds. Driven by strong westerly winds in the Southern Ocean, known as the “Roaring Forties” and “Furious Fifties,” this current is a persistent force.
Global Significance of the Antarctic Circumpolar Current
Beyond its physical dimensions, the Antarctic Circumpolar Current plays an important role in the global ocean system. It acts as a connector, linking the waters of the Atlantic, Pacific, and Indian Oceans. This connection allows for the exchange of water masses among major ocean basins, influencing global circulation patterns. The ACC also contributes to regulating Earth’s climate by distributing heat across the planet. It helps isolate Antarctica, acting as a thermal barrier that limits warmer water inflow and maintains the continent’s cold conditions.
The current’s dynamics also impact marine ecosystems by facilitating nutrient upwelling. This process brings nutrient-rich deep waters to the surface, fueling phytoplankton growth, which forms the base of the marine food web. This enhanced biological productivity supports diverse marine life, including krill, fish, whales, and seabirds, unique to the Southern Ocean. The ACC also plays a part in the global carbon cycle, absorbing carbon dioxide from the atmosphere and transporting it into the deep ocean.