The Antarctic Circumpolar Current (ACC) is the world’s largest and most powerful ocean current. Encircling Antarctica, it flows continuously from west to east through the Southern Ocean and is the only major ocean current to travel completely around the globe.
The ACC is also a critical link between the world’s major oceans, connecting the Atlantic, Pacific and Indian Oceans. It is driven primarily by the strong westerly winds that dominate the Southern Ocean, particularly the winds of the Roaring Forties, Furious Fifties and Screaming Sixties.
The World’s Most Powerful Ocean Current
One of the defining features of the Antarctic Circumpolar Current is its sheer scale. The ACC travels for more than 20,000 kilometres around Antarctica and transports roughly 170 million cubic metres of water every second through the Drake Passage, far more than the combined flow of all the world’s rivers.
Rather than being confined to the surface, the current extends thousands of metres into the ocean. This enormous movement of water makes the ACC one of the most important components of the global ocean circulation system.
Why Is the Antarctic Circumpolar Current So Important?
The ACC plays a pivotal role in regulating the Earth’s climate and oceans. As it circles Antarctica, it helps redistribute heat, nutrients, oxygen and carbon between the Atlantic, Pacific and Indian Oceans.
The Southern Ocean is also an important part of the global carbon cycle. Strong winds and currents bring deep, nutrient-rich water towards the surface, supporting the growth of phytoplankton. These microscopic organisms form the base of much of the Southern Ocean food web and absorb carbon dioxide through photosynthesis.
Some of that carbon ultimately makes its way into the deeper ocean, helping the oceans absorb and store a significant proportion of the carbon dioxide released into the atmosphere.
The ACC and Antarctica’s Frozen Climate
The Antarctic Circumpolar Current also contributes to Antarctica’s climatic isolation.
Because the ACC circles the continent without being blocked by another land mass, it helps separate the extremely cold waters surrounding Antarctica from the generally warmer waters farther north. This has helped maintain Antarctica’s exceptionally cold climate over geological timescales.
However, the relationship between the ACC and Antarctic ice is complex. Warmer deep ocean water can cross the current and reach parts of the Antarctic continental shelf, where it can contribute to the melting of ice shelves from below.
Scientists are therefore particularly interested in how changes in Southern Ocean winds and currents might affect Antarctica’s ice sheets and, ultimately, global sea levels.
The Antarctic Circumpolar Current and the Global Ocean Conveyor Belt
The ACC is closely connected to the global thermohaline circulation, sometimes described as the global ocean conveyor belt.
By linking the major ocean basins, the ACC allows enormous quantities of water and heat to move between them. Around Antarctica, surface waters, deep waters and bottom waters interact as part of a much larger global circulation system.
This circulation helps redistribute heat around the planet and influences climate far beyond the Southern Ocean.
How Climate Change Could Affect the ACC
Understanding the Antarctic Circumpolar Current is becoming increasingly important as the climate changes.
Changes in Southern Ocean winds, ocean temperatures, melting Antarctic ice and the amount of freshwater entering the ocean can all affect the waters through which the ACC flows. Scientists are studying how these changes could alter the current’s strength, position and structure, as well as its ability to transport heat and carbon.
Because the ACC connects all three major ocean basins, changes occurring in the Southern Ocean have the potential to influence ocean circulation and climate far beyond Antarctica.
The Antarctic Circumpolar Current may be thousands of miles from most of us, but its influence reaches around the globe. Understanding this extraordinary current is an important part of understanding our oceans, our climate and the future of Antarctica.
Understanding the Antarctic Circumpolar Current is crucial in the context of climate change. As global temperatures rise, changes in the ACC’s speed, position, and water composition could have cascading effects on ocean circulation, marine ecosystems, and the stability of Antarctic ice sheets. Scientists continue to study this massive current to predict better and mitigate the impacts of a warming planet.
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Main Image: AI generated image. A stylised representation of Antarctica.
Ocean Current Images Courtesy of Teara
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