Why is the Southern Ocean considered separate from the Atlantic, Pacific, and Indian oceans?

The Southern Ocean is considered a distinct body of water primarily due to its unique oceanographic and meteorological characteristics that create a natural separation from the Atlantic, Pacific, and Indian oceans.1

This separation is largely defined by the Antarctic Circumpolar Current, a powerful, wind-driven current that encircles Antarctica. Together with the winds circling the continent, this current creates the Antarctic Convergence, a zone where cold, northward-flowing Antarctic waters meet and mix with warmer waters from the other major oceans.213

While there is no universal agreement on its formal boundaries, many organizations and researchers define the Southern Ocean as the waters surrounding Antarctica south of 60° S latitude. This region is physically distinct because it is unbroken by any continental landmass, allowing the circumpolar current to flow continuously around the continent. Although some authorities historically grouped these waters with the Atlantic, Pacific, and Indian oceans, the recognition of the Southern Ocean as a fifth, separate entity has gained significant support, including official recognition by the National Geographic Society in 2021.314