Say Hello to a
On this year’s World Ocean Day, which was celebrated on June 08, the cartographers at National Geographic officially recognized the Southern Ocean, also known as the Antarctic or the Austral Ocean, as the world’s fifth – and newest – ocean. The Southern Ocean encompasses the waters surrounding Antarctica, with boundaries “roughly centred around a latitude of 60 degrees south. National Geographic, which began making maps in 1915, has erstwhile recognized four oceans: the Atlantic, Pacific, Indian, and Arctic Oceans.
National Geographic decided to designate the Antarctic waters as its own ocean (instead of merely southern parts the Atlantic, Indian and Pacific oceans) to bring awareness to, and promote conservation of the waters. But also because of its unique attributes, which scientists and geographers have long recognized. The reason behind this move, according to scientists, is that the waters south of that Antarctic Circumpolar Current are colder and ecologically distinct, making a home for thousands of species that can live nowhere else on Earth.
“The Southern Ocean encompasses unique and fragile marine ecosystems that are home to wonderful marine life such as whales, penguins, and seals,” said National Geographic Explorer-in-Residence Enric Sala in the announcement.
The waters around Antarctica (the Earth’s seventh continent) have also been known as the Antarctic Ocean or the Austral Ocean, though the use of Southern Ocean is the most popular in the media and scientific community, and is used by the US Board on Geographic Names and the International Hydrographic Organization and NOAA.
While the other oceans are defined by the continents that fence them in, the Southern Ocean is defined by a current. Scientists estimate that the Antarctic Circumpolar Current (ACC) was established roughly 34 million years ago, when Antarctica separated from South America. That allowed for the unimpeded flow of water around the bottom of the Earth.
The ACC flows from west to east around Antarctica, in a broad fluctuating band roughly centred around a latitude of 60 degrees south—the line that is now defined as the northern boundary of the Southern Ocean. Inside the ACC, the waters are colder and slightly less salty than ocean waters to the north.
Extending from the surface to the ocean floor, the ACC transports more water than any other ocean current. It pulls in waters from the Atlantic, Pacific and Indian Oceans, helping drive a global circulation system known as the conveyor belt, which transports heat around the planet. Cold, dense water that sinks to the ocean floor off Antarctica also helps store carbon in the deep ocean. In both those ways, the Southern Ocean has a crucial impact on Earth’s climate.
Generally, National Geographic has followed the International Hydrographic Organization (IHO) on marine names. While not directly responsible for determining them, the IHO works with the United Nations Group of Experts on Geographical Names to standardize names on an international scale. The IHO recognized the Southern Ocean in its 1937 guidelines but repealed that designation in 1953, citing controversy. It has deliberated on the matter since, but has yet to receive full agreement from its members to reinstate the Southern Ocean.
The US Board on Geographic Names, however, has used the name since 1999. And in February of this year, NOAA officially recognized the Southern Ocean as distinct.
Despite the Southern Ocean’s recent recognition by the National Geographic Society and the NOAA, the International Hydrographic Society (IHO) — an intergovernmental organization with 94 member states — has yet to ratify 2002 proposals to define the boundaries following disagreement among countries.
The writer is a member of staff.