Oceans Borders

Though generally described as several 'separate' oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.

The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria. The principal divisions are: Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern or Antarctic Ocean and Arctic Ocean. Smaller regions of the oceans are called seas, gulfs, bays, straits and other names.

Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt that covers the Earth's mantle. Continental crust is thicker but less dense. From this perspective, the earth has three oceans: the World Ocean, the Caspian Sea, and Black Sea. The latter two were formed by the collision of Cimmeria with Laurasia. The Mediterranean Sea is at times a discrete ocean, because tectonic plate movement has repeatedly broken its connection to the World Ocean through the Strait of Gibraltar. The Black Sea is connected to the Mediterranean through the Bosporus, but the Bosporus is a natural canal cut through continental rock some 7,000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.

Despite their names, smaller landlocked bodies of saltwater that are not connected with the World Ocean, such as the Aral Sea, are actually salt lakes.

Arctic Ocean
The Arctic Ocean covers much of the Arctic and washes upon northern North America and Eurasia and is sometimes considered a sea of the Atlantic.

The International Hydrographic Organization defines the limits of the Arctic Ocean proper (that is, excluding the seas within the Ocean) as follows:

• Between Greenland and West Spitzbergen  — The Northern limit of Greenland Sea.
• Between West Spitzbergen and North East Land — the parallel of lat. 80°N.
• From Cape Leigh Smith to Cape Kohlsaat — the Northern limit of Barentsz Sea.
• From Cape Kohlsaat to Cape Molotov — the Northern limit of Kara Sea.
• From Cape Molotov to the Northern extremity of Kotelni Island — the Northern limit of Laptev Sea.
• From the Northern extremity of Kotelni Island to the Northern point of Wrangel Island — the Northern limit of East Siberian Sea.
• From the Northern point of Wrangel Island to Point Barrow — the Northern limit of Chuckchi Sea.
• From Point Barrow to Cape Land's End on Prince Patrick Island — the Northern limit of Beaufort Sea, through the Northwest coast of Prince Patrick Island to Cape Leopold M'Clintock, thence to Cape Murray (Brook Island) and along the Northwest coast to the extreme Northerly point; to Cape Mackay (Borden Island); through the Northwesterly coast of Borden Island to Cape Malloch, to Cape Isachsen (Ellef Ringnes Island); to the Northwest point of Meighen Island to Cape Stallworthy (Axel Heiberg Island) to Cape Colgate the extreme West point of Ellesmere Island; through the North shore of Ellesmere Island to Cape Columbia thence a line to Cape Morris Jesup (Greenland).

Atlantic Ocean
The Atlantic Ocean separates the Americas from Eurasia and Africa. It may be further subdivided by the equator into northern and southern portions.

North Atlantic

The 3rd edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the North Atlantic Ocean as follows:

• On the West. The Eastern limits of the Caribbean Sea, the Southeastern limits of the Gulf of Mexico from the North coast of Cuba to Key West, the Southwestern limit of the Bay of Fundy and the Southeastern and Northeastern limits of the Gulf of St. Lawrence.
• On the North. The Southern limit of Davis Strait from the coast of Labrador to Greenland and the Southwestern limit of the Greenland Sea and Norwegian Sea from Greenland to the Shetland Islands.
• On the East. The Northwestern limit of the North Sea, the Northern and Western limits of the Scottish Seas, the Southern limit of the Irish Sea, the Western limits of the Bristol and English Channels, of the Bay of Biscay and of the Mediterranean Sea.
• On the South. The equator, from the coast of Brazil to the Southwestern limit of the Gulf of Guinea.

South Atlantic
The 3rd edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the South Atlantic Ocean as follows:

• On the Southwest. The meridian of Cape Horn, Chile (67°16'W) from Tierra del Fuego to the Antarctic Continent; a line from Cape Virgins (52°21′S 68°21′W / 52.35°S 68.35°W / -52.35; -68.35) to Cape Espiritu Santo, Tierra del Fuego, the Eastern entrance to Magellan Strait, Chile
• On the West. The limit of the Rio de La Plata.
• On the North. The Southern limit of the North Atlantic Ocean.
• On the Northeast. The limit of the Gulf of Guinea.
• On the Southeast. From Cape Agulhas along the meridian of 20° East to the Antarctic continent.
• On the South. The Antarctic Continent.

In 2000 the IHO redefined the Atlantic Ocean, moving its southern limit to 60°S, with the waters south of that line identified as the Southern Ocean. This new definition has not yet been ratified (a reservation has been lodged by Australia) though it is in use by the IHO and others. If and when adopted, the 2000 definition will be published in the 4th edition of Limits of Oceans and Seas, restoring the Southern Ocean as originally outlined in the 2nd edition and subsequently omitted from the 3rd edition.


Indian Ocean
The Indian Ocean washes upon southern Asia and separates Africa and Australia.

The 3rd edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the Indian Ocean as follows:

• On the North. The Southern limits of the Arabian Sea and the Lakshadweep Sea, the Southern limit of the Bay of Bengal, the Southern limits of the East Indian Archipelago, and the Southern limit of the Great Australian Bight.
• On the West. From Cape Agulhas in 20° long. East, Southward along this meridian to the Antarctic Continent.
• On the East. From South East Cape, the Southern point of Tasmania down the meridian 146°55'E to the Antarctic Continent.
• On the South. The Antarctic Continent.

In 2000 the IHO redefined the Indian Ocean, moving its southern limit to 60°S, with the waters south of that line identified as the Southern Ocean. This new definition has not yet been ratified (a reservation has been lodged by Australia) though it is in use by the IHO and others. If and when adopted, the 2000 definition will be published in the 4th edition of Limits of Oceans and Seas, restoring the Southern Ocean as originally outlined in the 2nd edition and subsequently omitted from the 3rd edition.


Pasific Ocean
The Pacific is the ocean that separates Asia and Australia from the Americas. It may be further subdivided by the equator into northern and southern portions.

North Pacific

The 3rd edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the North Pacific Ocean as follows:

• On the Southwest. The Northeastern limit of the East Indian Archipelago from the Equator to Luzon Island.
• On the West and Northwest. The Eastern limits of the Philippine Sea and Japan Sea and the Southeastern limit of the Sea of Okhotsk.
• On the North. The Southern limits of the Bering Sea and the Gulf of Alaska.
• On the East. The Western limit of Coastal waters of Southeast Alaska and Br. Columbia, and the Southern limit of the Gulf of California.
• On the South. The Equator, but excluding those islands of the Gilbert and Galàpagos Groups which lie to the Northward thereof.

South Pasific

The 3rd edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the South Pacific Ocean as follows:

• On the West. From Southeast Cape, the Southern point of Tasmania, down the meridian of 146°55'E to the Antarctic continent.
• On the Southwest and Northwest. The Southern, Eastern and Northeastern limits of the Tasman Sea, the Southeastern and Northeastern limits of the Coral Sea, the Southern, Eastern and Northern limits of the Solomon and Bismark seas, and the Northeastern limit of the East Indian Archipelago from New Guinea to the Equator.
• On the North. The Equator, but including those islands of the Gilbert and Galàpagos Groups which lie to the Northward thereof.
• On the East. The meridian of Cape Horn (67°16'W) from Tierra del Fuego to the Antarctic continent; a line from Cape Virgins (52°21′S 68°21′W / 52.35°S 68.35°W / -52.35; -68.35) to Cape Espititu Santo, Tierra del Fuego, the Eastern entrance to Magellan Strait. (These limits have not yet been officially accepted by Argentina and Chile.)
• On the South. The Antarctica.

In 2000 the IHO redefined the Pacific Ocean, moving its southern limit to 60°S, with the waters south of that line identified as the Southern Ocean. This new definition has not yet been ratified (a reservation has been lodged by Australia) though it is in use by the IHO and others. If and when adopted, the 2000 definition will be published in the 4th edition of Limits of Oceans and Seas, restoring the Southern Ocean as originally outlined in the 2nd edition and subsequently omitted from the 3rd edition.


Southern Ocean
The Southern Ocean contains the waters that surround Antarctica and sometimes is considered an extention of Pacific, Atlantic and Indian Oceans.

The 1937 second edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas publication included a definition of an ocean around Antarctica. However, this ocean did not appear in the 1953 third edition because "the northern limits ... are difficult to lay down owing to their seasonal change" - instead the Atlantic, Indian and Pacific Oceans were extended southward.

The IHO readdressed the question of the ocean's existence in a survey in 2000. Of its 68 member nations, 28 responded, and all responding members except Argentina agreed to define a new ocean, reflecting the importance placed by oceanographers on ocean currents. The proposal for the name Southern Ocean won 18 votes, beating the alternative Antarctic Ocean. Half of the votes supported a definition of the ocean's northern limit at 60°S (with no land interruptions at this latitude), with the other 14 votes cast for other definitions, mostly 50°S, but a few for as far north as 35°S. However, the 4th edition of Limits of Oceans and Seas was never ratified or published due to a reservation lodged by Australia, and so the 3rd edition (which does not delineate a separate Southern Ocean) has not been superseded. If and when the 4th edition is published, it will restore the Southern Ocean as originally outlined in the 2nd edition and subsequently omitted from the 3rd.

Despite this, the 4th edition definition has de facto usage by many organisations, scientists and nations - even by the IHO. Some nations' hydrographic offices have defined their own boundaries; the United Kingdom used the 55°S parallel for example.

Other sources such as the National Geographic Society continue to show the Atlantic, Pacific and Indian Oceans as extending to Antarctica, although articles on the National Geographic web site have begun to reference the Southern Ocean.

In Australia, cartographical authorities defined the Southern Ocean as including the entire body of water between Antarctica and the south coasts of Australia and New Zealand, although New Zealand authorities do not generally follow suit. Coastal maps of Tasmania and South Australia label the sea areas as Southern Ocean, while Cape Leeuwin in Western Australia is described as the point where the Indian and Southern Oceans meet.