See also the
list of seas article for the seas included in each ocean area.
Overview
Though generally described as several separate oceans, the world's oceanic waters constitute one global, interconnected body of salt water sometimes referred to as the
World Ocean or Global Ocean.[1][2] This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to
oceanography.[3]
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,[citation needed] and the
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, some smaller landlocked "seas" are not connected with the World Ocean, such as the
Caspian Sea (which is nevertheless, geologically, itself a full-fledged ocean—see above) and numerous
salt lakes such as the
Aral Sea.
A complete hierarchy showing which seas belong to which oceans, according to the
International Hydrographic Organization (IHO), is available at the European Marine Gazetteer website.[4] See also the
list of seas article for the seas included in each ocean area. Also note there are many varying definitions of the world's seas and no single authority.
List of oceans
The world ocean is divided into a number of principal oceanic areas that are delimited by the
continents and various oceanographic features: these divisions are the
Atlantic Ocean,
Arctic Ocean (sometimes considered an
estuary of the Atlantic),
Indian Ocean,
Pacific Ocean, and the
Southern Ocean, defined by the
International Hydrographic Organization (IHO) in 2000, the latter being a relatively new addition identified with a distinct ecosystem and a unique impact on global climate.[5] In turn, oceanic waters are interspersed by many smaller seas, gulfs, and bays.
If viewed from the southern pole of Earth, the Atlantic, Indian, and Pacific Oceans can be seen as lobes extending northward from the Southern Ocean. Farther north, the Atlantic opens into the Arctic Ocean, which is connected to the Pacific by the
Bering Strait, forming a continuous expanse of water.
The five oceans are:
The
Pacific Ocean, the largest of the oceans, also reaches northward from the Southern Ocean to the Arctic Ocean. It spans the gap between
Australia and
Asia, and the
Americas. The Pacific Ocean meets the Atlantic Ocean south of
South America at
Cape Horn.
The
Atlantic Ocean, the second largest, extends from the Southern Ocean between the
Americas, and
Africa and
Europe, to the Arctic Ocean. The Atlantic Ocean meets the Indian Ocean south of Africa at
Cape Agulhas.
The
Indian Ocean, the third largest, extends northward from the Southern Ocean to
India, the
Arabian Peninsula, and
Southeast Asia in Asia, and between
Africa in the west and
Australia in the east. The Indian Ocean joins the Pacific Ocean to the east, near Australia.
The
Southern Ocean is a proposed
ocean surrounding
Antarctica, dominated by the
Antarctic Circumpolar Current, generally the ocean south of 60 degrees south latitude. The Southern Ocean is partially covered in
sea ice, the extent of which varies according to the season. The Southern Ocean is the second smallest of the five named oceans.
Note that these definitions exclude any marginal waterbodies that are separately defined by the IHO (such as the
Kara Sea and
East Siberian Sea), though these are usually considered to be part of the Arctic Ocean.
The CIA defines the limits of the
Arctic Ocean differently, as depicted in the map comparing its definition to the IHO's definition.
Notes
^Defined by IHO as "A line joining the Northernmost point of Spitzbergen [sic] [
Svalbard] to the Northernmost point of
Greenland."
^Defined by IHO as "A line joining Cape Molotov to the Northern extremity of
Kotelni Island (76°10′N, 138°50′E)."
^Defined by IHO as "A line from the Northernmost point of Wrangel Island (179°30'W) to the Northern sides of the
De Long Islands (including
Henrietta and
Jeannette Islands) and
Bennett Island, thence to the Northern extremity of Kotelni Island."
^Defined by IHO as "A line from Point Barrow,
Alaska (71°20′N, 156°20′W) to the Northernmost point of Wrangel Island (179°30'W)."
^Defined by IHO as "A line from Point Barrow, Alaska, to Lands End, Prince Patrick Island (76°16′N, 124°08′W)."
Atlantic Ocean
The
Atlantic Ocean separates the Americas from
Europe and
Africa. It may be further subdivided by the
Equator into northern and southern portions.
North Atlantic Ocean
The 3rd edition, currently in force, of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the North Atlantic Ocean (excluding the seas it contains) as follows:[9]: Art.23
The 3rd edition (currently in force) of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the South Atlantic Ocean (excluding the seas it contains) as follows:[9]
Note that these definitions exclude any marginal waterbodies that are separately defined by the IHO (such as the
Bay of Biscay and
Gulf of Guinea), though these are usually considered to be part of the Atlantic Ocean.
In its 2002 draft, 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 (and, in addition, a reservation was lodged in 2003 by Australia.)[11] While the name "Southern Ocean" is frequently used, some geographic authorities such as the 10th edition of the World Atlas from the U.S.
National Geographic Society generally show the Atlantic, Indian, and Pacific Oceans continuing to Antarctica. If and when adopted, the 2002 definition would be published in the 4th edition of Limits of Oceans and Seas, re-instituting the 2nd edition's "Southern Ocean", omitted from the 3rd edition.
Notes
^Defined by IHO as "From Point San Diego (
Puerto Rico) Northward along the meridian thereof (65°39'W) to the 100 fathom line, thence Eastward and Southward, in such a manner that all islands, shoals and narrow waters of the
Lesser Antilles are included in the Caribbean Sea as far as
Galera Point (Northeast extremity of the island of
Trinidad). From Galera Point through Trinidad to Galeota Point (Southeast extreme) and thence to Baja Point (9°32′N61°0′W / 9.533°N 61.000°W / 9.533; -61.000) in
Venezuela".
^Defined by IHO as "From
Dunnet Head (3°22'W) in
Scotland to Tor Ness (58°47'N) in the Island of
Hoy, thence through this island to the Kame of Hoy (58°55'N) on to Breck Ness on
Mainland (58°58'N) through this island to
Costa Head (3°14'W) and to Inga Ness (59'17'N) in
Westray through Westray, to Bow Head, across to Mull Head (North point of
Papa Westray) and on to Seal Skerry (North point of
North Ronaldsay) and thence to
Horse Island (South point of the
Shetland Islands)".
The 3rd edition, currently in force, of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the Indian Ocean (excluding the seas it contains) as follows:[9]
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.
Note that this definition excludes any marginal waterbodies that are separately defined by the IHO (such as the
Bay of Bengal and
Arabian Sea), though these are usually considered to be part of the Indian Ocean.
In its 2002 draft, 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 (and, in addition, a reservation was lodged in 2003 by Australia.)[11] While the name "Southern Ocean" is frequently used, some geographic authorities such as the 10th edition of the World Atlas from the U.S.
National Geographic Society generally show the Atlantic, Indian, and Pacific Oceans continuing to Antarctica. If and when adopted, the 2002 definition would be published in the 4th edition of Limits of Oceans and Seas, re-instituting the 2nd edition's "Southern Ocean", omitted from the 3rd edition.
The boundary of the Indian Ocean is a constitutional issue for Australia. The
Imperial South Australia Colonisation Act, 1834, which established and defined the
Colony of South Australia defined South Australia's southern limit as being the "Southern Ocean". This definition was carried through to Australian constitutional law upon the Federation of Australia in 1901.
Notes
^Defined by IHO as "A line running from the South extremity of
Addu Atoll (
Maldives), to the Eastern extreme of
Ràs Hafun (
Africa, 10°26'N)".
^Defined by IHO as "A line running from
Dondra Head in Ceylon [
Sri Lanka] to the most Southerly point of Addu Atoll".
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 Ocean
The 3rd edition, currently in force, of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the North Pacific Ocean (excluding the seas it contains) as follows:[9]
On the South. The Equator, but excluding those islands of the
Gilbert and
Galàpagos[sic] Groups which lie to the Northward thereof.
South Pacific Ocean
The 3rd edition, currently in force, of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas defines the limits of the South Pacific Ocean (excluding the seas it contains) as follows:[9]
Note that these definitions exclude any marginal waterbodies that are separately defined by the IHO (such as the
Gulf of Alaska and
Coral Sea), though these are usually considered to be part of the Pacific Ocean.
In its 2002 draft, 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 (and, in addition, a reservation was lodged in 2003 by Australia.)[11] While the name "Southern Ocean" is frequently used, some geographic authorities such as the 10th edition of the World Atlas from the U.S.
National Geographic Society generally show the Atlantic, Indian, and Pacific Oceans continuing to Antarctica. If and when adopted, the 2002 definition would be published in the 4th edition of Limits of Oceans and Seas, re-instituting the 2nd edition's "Southern Ocean", omitted from the 3rd edition.
Notes
^Defined by IHO as "By the ridge joining Japan to the
Bonin,
Volcano and
Ladrone (Mariana) Islands, all these being included in the Philippine Sea".
^Defined by IHO as "In the
Tsugaru Kaikô. From the extremity of Siriya Saki (141°28'E) to the extremity of Esan Saki (41°48'N)".
^Defined by IHO as "A line running from
Nosyappu Saki (Cape Noshap, 43°23'N) in the Island of
Hokusyû (Yezo) through the
Kuril or Tisima Islands to
Cape Lopatka (South point of
Kamchatka) in such a way that all the narrow waters between Hokusyû and Kamchatka are included in the Sea of Okhotsk".
^Northeastern limit defined by IHO as "By a line from the Southern point of
New Ireland to the North point of
Buka Island, through this island to the Northwest point of
Bougainville Island, along the Southern coasts of Bougainville,
Choisel,
Ysabel,
Malaita and San Cristobal Islands".
^North and Eastern limit defined by IHO as "By the Northern and Northeastern coasts of the islands of New Ireland,
New Hanover, the
Admiralty Islands,
Hermit Island, and the
Ninigo Group, through Manu and
Aua Islands to
Wuvulu Island and thence a line to Baudissin Point in New Guinea (142°02'E)".
The
Southern Ocean contains the waters that surround
Antarctica and sometimes is considered an extension of Pacific, Atlantic and Indian Oceans.[9]
In 1928, the first edition of the
International Hydrographic Organization's (IHO) Limits of Oceans and Seas publication included the Southern Ocean around Antarctica. The Southern Ocean was delineated by land-based limits – the continent of Antarctica to the south, and the continents of South America, Africa, and Australia plus
Broughton Island, New Zealand in the north. The detailed land-limits used were
Cape Horn in South America,
Cape Agulhas in Africa, the southern coast of Australia from
Cape Leeuwin, Western Australia, to
South East Cape, Tasmania, via the western edge of the water body of
Bass Strait, and then Broughton Island before returning to Cape Horn.[15]
The northern limits of the Southern Ocean were moved southwards in the IHO's 1937 second edition of the Limits of Oceans and Seas. The Southern Ocean then extended from Antarctica northwards to latitude 40° south between
Cape Agulhas in Africa (long. 20° east) and
Cape Leeuwin in Western Australia (long. 115° east), and extended to latitude 55° south between
Auckland Island of New Zealand (long. 165° or 166° east) and
Cape Horn in South America (long. 67° west).[16]
The Southern Ocean did not appear in the 1953 third edition because "...the northern limits ... are difficult to lay down owing to their seasonal change ... Hydrographic Offices who issue separate publications dealing with this area are therefore left to decide their own northern limits. (Great Britain uses the Latitude of 55° South)". Instead, in the IHO 1953 publication, the Atlantic, Indian and Pacific Oceans were extended southward, the Indian and Pacific Oceans (which had not previously touched pre 1953, as per the first and second editions) now abutted at the meridian of
South East Cape, and the southern limits of the
Great Australian Bight and the
Tasman Sea were moved northwards.[9]
The IHO readdressed the question of the Southern Ocean in a survey in 2000. Of its 68 member nations, 28 responded, and all responding members except
Argentina agreed to redefine the 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.
The 4th edition of Limits of Oceans and Seas has yet to be published due to "areas of concern" by several countries relating to various naming issues around the world. The IHB circulated a new draft of the 4th edition of the publication in August 2002, however there were still various changes, 60 seas were added or renamed from the 3rd edition, and even the name of the publication was changed.[17] A reservation had also been lodged by Australia regarding the Southern Ocean limits.[11] Effectively, the 3rd edition (which did not delineate the Southern Ocean leaving delineation to local hydrographic offices) has yet to be superseded and IHO documents declare that it remains "currently in force."
Despite this, the 4th edition definition has de facto usage by many organisations, scientists and nations – even at times by IHO committees.[18] Some nations' hydrographic offices have defined their own boundaries; the United Kingdom used the
55°S parallel for example.[9]
Other sources, such as the
National Geographic Society, 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.[19]
In
Australia,
cartographic authorities defined the Southern Ocean as including the entire body of water between Antarctica and the south coasts of Australia and
New Zealand. This delineation is basically the same as the original (first) edition of the IHO publication and effectively the same as the second edition. In the second edition, the
Great Australian Bight was defined as the only geographical entity between the Australian coast and the Southern Ocean. Coastal maps of
Tasmania and
South Australia label the sea areas as Southern Ocean,[20] while
Cape Leeuwin in
Western Australia is described as the point where the Indian and Southern Oceans meet.[21]
Theories of natural delimitation between the Atlantic and Pacific oceans
^Passarelli, Bruno (1998). El delirio armado: Argentina-Chile, la guerra que evitó el Papa (in Spanish). Editorial Sudamericana. p. 48.
ISBN978-9-5007-1469-3.
^Santibañez, Rafael (1969). "El Canal Beagle y la delimitación de los océanos".
Los derechos de Chile en el Beagle (in Spanish). Santiago: Editorial Andrés Bello. pp. 95–109.
OCLC1611130. Retrieved 22 March 2021.