The National Geographic Society of the United States announced the official recognition of the fifth ocean – the South, washing the shores of Antarctica. This decision is the result of many years of research efforts. So in the XXI century – although, it would seem, the era of major geographical discoveries is already far in the past – the map of the world has changed.
History of the issue
For the first time the designation “Southern Ocean” was used by the Spanish conquistador Vasco Nunez de Balboa at the beginning of the 16th century, describing the cold currents coming from the south to the shores of South America. Later, Antarctic expeditions equipped ships “to the Southern Ocean”. But officially it appeared, perhaps, only on maps published in Australia – all waters located south of the Australian continent were attributed to it.
The debate over whether to recognize the fifth ocean or not flared up in 1921, the year of the creation of the International Hydrographic Organization (IHO), designed to coordinate internationally shipping and trade in the oceans. In 1937, the term “Southern Ocean” was officially enshrined in the publications of the IHO.
Scientists supported this – after all, the waters adjacent to Antarctica and united by the Antarctic circumpolar current have a special specificity. In terms of physicochemical and biological characteristics, they are not similar to the other three oceans, merging in the southern circumpolar zone.
However, in 1953, the International Hydrographic Organization canceled its own decision due to the impossibility of drawing clear boundaries of the Southern Ocean. And therefore, to regulate navigation and commercial activities within its limits.
Scientists disagreed: they increasingly mentioned this term in scientific publications, emphasized the uniqueness of the Southern Ocean and the importance of a separate study of its hydrological and biosystems. As a result, in 2000, the IHO again adopted the classification, according to which the oceans were divided into five parts. But in order to make changes to all geographical atlases and textbooks, ratification at the level of official departments of the leading countries of the world was required.
The key was the recognition of the Southern Ocean this year by the US National Oceanic and Atmospheric Administration (NOAA). Even earlier, in 1999, the term was coined by the American Board of Geographical Names. And now the point has been set – on June 8, World Oceans Day, the National Geographic Society of the United States announced: from now on, the Southern Ocean will be marked on all maps.
The boundaries of the new ocean
The ancient Greeks understood the ocean as the world’s greatest river, which surrounds the land from all sides. It was named after the mythological titan Ocean – the son of Uranus and Gaia, that is, Heaven and Earth, brother and husband Tethys, the goddess of the primeval waters.
From the point of view of geographical science, there is only one ocean on Earth – the World, global water envelope. Everything else is its parts, and how many there are depends on the selection criteria. The simplest and most obvious is the location between the continents, that is, limited land mass on all sides. On this basis, the Atlantic, Pacific, Indian and Arctic oceans are classified as oceans.
No less important from the point of view of scientists – hydrographers, oceanologists, biologists – and other criteria: the presence of its own water circulation system, their physicochemical characteristics, the species composition of flora and fauna, the scheme of interaction with the atmosphere. And in this regard, the Southern Ocean is an absolutely independent part of the hydrosphere, although it does not have a clearly delineated northern border by islands or continents.
The International Hydrographic Organization, which recognized the Southern Ocean in 2000, determined its territory conditionally – from the coast of Antarctica to the north to the 60th parallel of the south latitude. This decision was taken by a majority vote for formal reasons – the 60th parallel does not cross land anywhere, and it is within these limits that the United Nations Antarctic Treaty operates.
It is clear that geographers were not satisfied with this approach. In their opinion, the northern boundary of the Southern Ocean should be drawn along the Antarctic Polar Front, within which the cold waters of the Antarctic Circumpolar Current circulate. This zone surrounding Antarctica is also called the Antarctic Convergence.
On its northern border, located between the 48th and 61st parallels south latitude, the cold waters of Antarctica flowing northward meet with the warmer Pacific and Atlantic oceans. Heading south, the convergence boundary is precisely defined by the sudden drop in sea water temperature from 5.6 degrees Celsius to below two degrees Celsius. The Antarctic Convergence Line separates two regions that differ in climate and biodiversity.
The boundaries of the Southern Ocean are no less clearly manifested in the bottom topography – in the form of underwater uplifts practically along the entire Antarctic Polar Front.
Areas along the Antarctic Polar Front are extremely rich in fish and marine mammals. The dense cold waters drain here under the warm ones, and the nutrient-rich, rising deep streams form a favorable habitat for Antarctic krill and other marine organisms.
The Atlantic circumpolar current, which moves in a circle from west to east, crossing all meridians, is the most powerful on Earth, it carries a hundred times more water than all the rivers of the world. Scientists believe that it originated 34 million years ago, when Antarctica separated from South America. Moving cold waters along the bottom from Antarctica to the north, it draws in surface warm waters from the Atlantic and Pacific Ocean into the polar region. It is the most important element of the global “conveyor belt” of currents, which determines the heat transfer scheme and regulates the climate on the planet.
Diagram of ocean currents in Antarctica. The boundaries of the Southern Ocean are determined by the Antarctic Circumpolar Current, which moves from west to east
The area of the new ocean is 20.3 million square kilometers: this is approximately two territories of the United States. It is larger than the Artic Ocean and the fourth largest in the world after the Pacific, Atlantic and Indian.
The average depth is 3270 meters, and the lowest point of the bottom is at 8264 meters, in the South Sandwich Trench.