Borders of the oceans explained

The borders of the oceans are the limits of Earth's oceanic waters. The definition and number of oceans can vary depending on the adopted criteria. The principal divisions (in descending order of area) of the five oceans are the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern (Antarctic) Ocean, and Arctic Ocean. Smaller regions of the oceans are called seas, gulfs, bays, straits, and other terms. Geologically, an ocean is an area of oceanic crust covered by water.

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] This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[2]

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

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 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.[3] 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.[4] 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:

Arctic Ocean

The Arctic Ocean covers much of the Arctic and washes upon Northern America and Eurasia. It is sometimes considered a sea or estuary of the Atlantic Ocean.[5] [6]

The International Hydrographic Organization (IHO) defines the limits of the Arctic Ocean (excluding the seas it contains) as follows:[7]

Between Greenland and West Spitzbergen – The Northern limit of Greenland Sea.[8]

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.[9]

From Cape Kohlsaat to Cape Molotov – the Northern limit of Kara Sea.[10]

From Cape Molotov to the Northern extremity of Kotelni Island – the Northern limit of Laptev Sea.[11]

From the Northern extremity of Kotelni Island to the Northern point of Wrangel Island – the Northern limit of East Siberian Sea.[12]

From the Northern point of Wrangel Island to Point Barrow – the Northern limit of Chuckchi Sea.[13]

From Point Barrow to Cape Land's End on Prince Patrick Island – the Northern limit of Beaufort Sea,[14] through the Northwest coast of Prince Patrick Island to Cape Leopold M'Clintock, thence to Cape Murray (Brook Island [''sic'']) 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).

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

  1. "
  2. Spilhaus. Athelstan F.. July 1942. Maps of the whole world ocean. American Geographical Society).. 32 . 3. 431–5.
  3. http://www.marbef.org/data/gazetteer.php?p=browser European Marine Gazetteer browser
  4. Web site: Rosenberg . Matt . Do You Know the World's Newest Ocean? . ThoughtCo . 1 May 2005 . 16 December 2017.
  5. http://marinebio.org/oceans/ The Ocean
  6. http://www.britannica.com/EBchecked/topic/33188/Arctic-Ocean Arctic Ocean
  7. Web site: Limits of Oceans and Seas, 3rd edition. 1953. International Hydrographic Organization. 26 May 2020.
  8. Defined by IHO as "A line joining the Northernmost point of Spitzbergen [<nowiki/>[[Svalbard]]] to the Northernmost point of Greenland."
  9. Defined by IHO as "Cape Leigh Smith across the Islands Bolshoy Ostrov (Great Island) [<nowiki/>[[Storøya]]], Gilles [<nowiki/>[[Kvitøya]]] and Victoria; Cape Mary Harmsworth (Southwestern extremity of Alexandra Land) along the northern coasts of Franz-Josef Land as far as Cape Kohlsaat (81°14′N, 65°10′E)."
  10. Defined by IHO as "Cape Kohlsaat to Cape Molotov (81°16′N, 93°43′E) (Northern extremity of Severnaya Zemlya on Komsomolets Island)."
  11. Defined by IHO as "A line joining Cape Molotov to the Northern extremity of Kotelni Island (76°10′N, 138°50′E)."
  12. 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."
  13. 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)."
  14. 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:

On the West. The Eastern limits of the Caribbean Sea,[15] the Southeastern limits of the Gulf of Mexico[16] from the North coast of Cuba to Key West, the Southwestern limit of the Bay of Fundy[17] and the Southeastern and Northeastern limits of the Gulf of St. Lawrence.[18]

On the North. The Southern limit of Davis Strait[19] from the coast of Labrador to Greenland and the Southwestern limit of the Greenland Sea[20] and Norwegian Sea[21] from Greenland to the Shetland Islands.

On the East. The Northwestern limit of the North Sea,[22] the Northern and Western limits of the Scottish Seas,[23] the Southern limit of the Irish Sea,[24] the Western limits of the Bristol[25] and English Channels,[26] of the Bay of Biscay[27] and of the Mediterranean Sea.[28]

On the South. The equator, from the coast of Brazil to the Southwestern limit of the Gulf of Guinea.[29]

Note that this definition excludes any marginal waterbodies that are separately defined by the IHO (such as the Caribbean Sea and North Sea), though these are usually considered to be part of the Atlantic Ocean.

South 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 South Atlantic Ocean (excluding the seas it contains) 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 to Cape Espiritu Santo, Tierra del Fuego, the Eastern entrance to Magellan Strait.

On the West. The limit of the Rio de La Plata.[30]

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.

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.)[31] 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

  1. "
  2. Spilhaus. Athelstan F.. July 1942. Maps of the whole world ocean. American Geographical Society).. 32 . 3. 431–5.
  3. http://www.marbef.org/data/gazetteer.php?p=browser European Marine Gazetteer browser
  4. Web site: Rosenberg . Matt . Do You Know the World's Newest Ocean? . ThoughtCo . 1 May 2005 . 16 December 2017.
  5. http://marinebio.org/oceans/ The Ocean
  6. http://www.britannica.com/EBchecked/topic/33188/Arctic-Ocean Arctic Ocean
  7. Web site: Limits of Oceans and Seas, 3rd edition. 1953. International Hydrographic Organization. 26 May 2020.
  8. Defined by IHO as "A line joining the Northernmost point of Spitzbergen [<nowiki/>[[Svalbard]]] to the Northernmost point of Greenland."
  9. Defined by IHO as "Cape Leigh Smith across the Islands Bolshoy Ostrov (Great Island) [<nowiki/>[[Storøya]]], Gilles [<nowiki/>[[Kvitøya]]] and Victoria; Cape Mary Harmsworth (Southwestern extremity of Alexandra Land) along the northern coasts of Franz-Josef Land as far as Cape Kohlsaat (81°14′N, 65°10′E)."
  10. Defined by IHO as "Cape Kohlsaat to Cape Molotov (81°16′N, 93°43′E) (Northern extremity of Severnaya Zemlya on Komsomolets Island)."
  11. Defined by IHO as "A line joining Cape Molotov to the Northern extremity of Kotelni Island (76°10′N, 138°50′E)."
  12. 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."
  13. 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)."
  14. Defined by IHO as "A line from Point Barrow, Alaska, to Lands End, Prince Patrick Island (76°16′N, 124°08′W)."
  15. 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 in Venezuela".
  16. Defined by IHO as "A line joining Cape Catoche Light with the Light on Cape San Antonio in Cuba, through this island to the meridian of 83°W and to the Northward along this meridian to the latitude of the South point of the Dry Tortugas (24°35'N), along this parallel Eastward to Rebecca Shoal (82°35'W) thence through the shoals and Florida Keys to the mainland at eastern end of Florida Bay, all the narrow waters between the Dry Tortugas and the mainland being considered to be within the Gulf".
  17. Defined by IHO as "A line running northwesterly from Cape St. Mary (44°05'N) Nova Scotia, through Machias Seal Island (67°06'W) and on to Little River Head (44°39'N) in the State of Maine".
  18. Defined by IHO as "A line from Cape Canso to Red Point in Cape Breton Island, through this Island to Cape Breton and on to Pointe Blanche in the Island of St. Pierre, and thence to the Southwest point of Morgan Island " and "A line running from Cape Bauld (North point of Kirpon Island,) to the East extreme of Belle Isle and on to the Northeast Ledge . Thence a line joining this ledge with the East extreme of Cape St. Charles (52°13'N) in Labrador".
  19. Defined by IHO as "The parallel of 60° North between Greenland and Labrador".
  20. Defined by IHO as "A line joining Straumness (NW extreme of Iceland) to Cape Nansen in Greenland".
  21. Defined by IHO as "From a point on the West coast of Norway in Latitude 61°00' North along this parallel to Longitude 0°53' West thence a line to the NE extreme of Fuglö and on to the East extreme of Gerpir in Iceland".
  22. 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)".
  23. Defined by IHO as "A line running from Bloody Foreland in Ireland to the West point of Tory Island, on to Barra Head, the Southwest point of the Hebrides, thence through these islands, in such a manner that the West coasts of the main islands appertain to the Atlantic Ocean and all the narrow waters appertain to the Inner Seas, as far as the Butt of Lewis (North Point), and thence to Cape Wrath (58°37'N) in Scotland".
  24. Defined by IHO as "A line joining St. David's Head to Carnsore Point ".
  25. Defined by IHO as "a line joining Hartland Point [in [[Devon]]] to St. Govan's Head [in [[Pembrokeshire]]] ".
  26. Defined by IHO as "A line joining Isle Vierge to Lands End ".
  27. Defined by IHO as "A line joining Cap Ortegal to Penmarch Point ".
  28. Defined by IHO as "A line joining the extremities of Cape Trafalgar (Spain) and Cape Spartel (Africa)".
  29. Defined by IHO as "A line running Southeastward from Cape Palmas in Liberia to Cape Lopez ".
  30. Defined by IHO as "A line joining Punta del Este, Uruguay and Cabo San Antonio, Argentina ".
  31. News: Canberra all at sea over position of Southern Ocean. Darby. Andrew. 22 December 2003. The Age. 21 December 2009.

Indian Ocean

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

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:

On the North. The Southern limits of the Arabian Sea[32] and the Lakshadweep Sea,[33] [51] the Southern, Eastern and Northern limits of the Solomon[52] and Bismark[53] seas, and the Northeastern limit of the East Indian Archipelago from New Guinea to the Equator.[54]