Southern Ocean: History, Boundaries, and Official Status

Introduction and Boundary Designations. The entire planet is connected by a single global marine environment covering more than 70 percent of the Earth’s surface. However, because of the existence of continents, many parts of this vast body of water are regionally isolated. This has given rise historically to four named oceans: Pacific, Atlantic, Indian, and Arctic. A fifth ocean has intermittently been proposed as well, the Southern Ocean, sometimes referred to as the Antarctic Ocean or the Austral Ocean. Although there remains some disagreement to this day on its exact boundaries, or even its existence, the United States and many other governments accept the view that the Southern Ocean is the circular body of water surrounding Antarctica, with a distinct northern boundary from the Indian, Pacific, and Atlantic Oceans, at approximately 60°S latitude.

The boundaries and nomenclature of the Southern Ocean have shifted continuously throughout history. It was previously known by multiple other names dating all the way back to the ancient Greek historians Diodorus and Palaephatus, who named the water south of Cape Verde the Aethiopian Sea. The name Aethiopian Sea was used intermittently on sixteenth- and seventeenth-century maps as well, but it fell into disuse in the 1700s and was replaced by the terms Southern Atlantic Ocean, the South Seas, the Great Southern Ocean, or simply the Southern Ocean. During the 1700s and 1800s, there was no consensus on where to mark the boundary for the Southern Ocean, or if it deserved delineation from the Indian, Pacific, and Atlantic Oceans at all. James Cook, who first proved the continuity of the Southern Ocean water mass on his voyages, suggested that the northern boundary abuts the subtropical island of New Caledonia at 23°S. Additional suggestions by explorers and map makers included 40°S, 50°S, and, in the 1795 Geographical Dictionary by William Peacock and Co., “southward of America and Africa.” It was not until the discovery and exploration of Antarctica began in the 1900s that universal standard boundary lines were drawn.

In 1921, the International Hydrographic Organization (IHO) was established as an intergovernmental technical and consultative group focused on improving the safety and efficiency of navigation and the protection of the ungoverned marine environment (“high seas”) for all coastal member states. This was the result of a series of international maritime conferences held in Washington, DC., St. Petersburg, and London between 1889 and 1919. The IHO was founded with eighteen charter member states, and the original and current headquarters is located in Monaco.

Among the IHO charter’s goals is the pursuit of the greatest possible uniformity in all nautical charts and documents. To this end, the IHO produced its first edition of the Limits of Oceans and Seas, which identified the Southern Ocean as bounded by Antarctica to the south and by South America, Africa, Australia, and New Zealand to the north. This boundary was pushed farther south in the second edition published in 1937, with northern boundaries no longer abutting landmasses. The northern boundary was placed at 40°S between Africa and Australia and at 55°S between New Zealand and South America. The 1953 (third) edition of Limits of Oceans and Seas omitted the Southern Ocean entirely. The IHO noted that a majority of the member states at the time saw no justification for the distinction between the Southern Ocean and the Indian, Pacific, and Atlantic Oceans. Great Britain disagreed with this change and instead published its own hydrographic map placing the Southern Ocean boundary at 55°S.

Thus, the Southern Ocean was not officially recognized until fifty years later, when the most recent fourth edition of the Limits of Oceans and Seas was drafted in 2002. The IHO sent a survey to the sixty-eight member states and received responses from twenty-eight of them. All who responded, except Argentina, agreed to reinstate the Southern Ocean boundaries at approximately 60°S latitude. However, due to governmental disputes in other oceans, including debates concerning the Sea of Japan, the 2002 publication was never ratified by member nations. Therefore, the IHO officially uses the 1953 treaty, and the Southern Ocean is still not officially recognized by the intergovernmental body.

However, most countries and organizations use the fourth edition despite its draft status, including the US Board on Geographic Names, which officially recognizes the current boundary and nomenclature of the Southern Ocean. Scientifically, this makes sense as well, as there are many oceanographic and physical differences between the Southern Ocean and its three bounding neighbors (Indian, Pacific, and Atlantic). Some scientists disagree with a fixed northern boundary, however, suggesting that it should instead extend to the edge of the Antarctic Circumpolar Current, the defining oceanographic feature of the Southern Ocean that fluctuates with longitude and season.