Difference between revisions of "Atlantic Ocean" - New World Encyclopedia
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{{Five oceans}} | {{Five oceans}} | ||
| − | + | [[Image:Atlantic_Ocean.png|right|Atlantic Ocean]] | |
| + | {{redirect|Atlantic}} | ||
| − | + | The '''Atlantic Ocean''' is the second-largest of the world's [[ocean]]ic divisions; with a total area of about 106.4 million [[square kilometre]]s (41.1 million [[square mile]]s), it covers approximately one-fifth of the [[Earth]]'s surface. Its name, derived from [[Greek mythology]], means the "[[Sea]] of [[Atlas (mythology)|Atlas]]." The oldest known mention of this name is contained in ''[[Histories (Herodotus)|The Histories]]'' of [[Herodotus]] around 450 B.C.E. (I 202). | |
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| − | The average | + | The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between the [[Americas]] to the west, and [[Eurasia]] and [[Africa]] to the east. A component of the all-encompassing [[World Ocean]], it is connected in the north to the [[Arctic Ocean]] (which is sometimes considered a [[sea]] of the Atlantic), to the [[Pacific Ocean]] in the southwest, the [[Indian Ocean]] in the southeast, and the [[Southern Ocean]] in the south. (Alternatively, in lieu of it connecting to the Southern Ocean, the Atlantic may be reckoned to extend southward to [[Antarctica]].) The [[equator]] subdivides it into the '''North Atlantic Ocean''' and '''South Atlantic Ocean'''. |
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| + | ==Geography== | ||
| + | The Atlantic Ocean is bounded on the west by [[North America|North]] and [[South America]]. In the north and northeast, it is separated from the Arctic Ocean by the [[Canadian Arctic Archipelago]], [[Greenland]], [[Iceland]], [[Jan Mayen]], [[Svalbard]], and mainland [[Europe]]. It connects to the Arctic Ocean through the [[Denmark Strait]], [[Greenland Sea]], [[Norwegian Sea]], and [[Barents Sea]]. To the east, the boundaries of the ocean proper are Europe, the [[Strait of Gibraltar]] (where it connects with the [[Mediterranean Sea]], one of its [[marginal sea]]s, and, in turn, the [[Black Sea]]), and Africa. In the southeast, the Atlantic merges into the Indian Ocean, the border being defined by the 20° East meridian, running south from [[Cape Agulhas]] to [[Antarctica]]. While some authorities show the Atlantic Ocean extending south to Antarctica, others show it as bounded to the south by the Southern Ocean <ref>[http://ioc.unesco.org/oceanteacher/OceanTeacher2/01_GlobOcToday/03_GeopolOc/s23_1953.pdf ''Limits of Oceans and Seas'']. International Hydrographic Organization Special Publication No. 23, 1953.</ref>. In the southwest, the [[Drake Passage]] connects it to the Pacific Ocean. A man-made link between the Atlantic and Pacific is provided by the [[Panama Canal]]. Beside those mentioned, other large bodies of water adjacent to the Atlantic are the [[Caribbean Sea]], the [[Gulf of Mexico]], [[Hudson Bay]], the Mediterranean Sea, the [[North Sea]], and the [[Baltic Sea]]. | ||
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| + | Covering approximately 20% of Earth's surface, the Atlantic Ocean is second only to the Pacific in size. With its adjacent seas it occupies an area of about [[1 E+14 m²|106,400,000]] [[square kilometer]]s (41,100,000 [[square mile|sq mi]]); without them, it has an area of [[1 E+13 m²|82,400,000 square kilometers]] (31,800,000 sq mi). The land area that drains into the Atlantic is four times that of either the Pacific or Indian oceans. The volume of the Atlantic Ocean with its adjacent seas is [[1 E+15 m³|354,700,000]] [[cubic kilometer]]s (85,100,000 [[cubic mile|cu mi]]) and without them 323,600,000 cubic kilometers (77,640,000 cu mi). | ||
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| + | The average depths of the Atlantic, with its adjacent seas, is 3,338 [[meter]]s (10,932 [[foot (unit of length)|ft]]); without them it is 3,926 meters (12,881 ft). The greatest depth, 8,605 meters (28,232 ft), is in the [[Puerto Rico Trench]]. The width of the Atlantic varies from [[1 E+6 m|2,848]] [[kilometer]]s (1,770 mi) between [[Brazil]] and [[Liberia]] to about 4,830 kilometers (3,000 mi) between the [[United States]] and northern Africa. | ||
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==Ocean bottom== | ==Ocean bottom== | ||
| − | The principal feature of the bottom [[ | + | The principal feature of the bottom [[bathymetry]] ([[terrain]]) of the Atlantic Ocean is a submarine mountain range called the [[Mid-Atlantic Ridge]]. It extends from Iceland in the north to approximately 58° South latitude, reaching a maximum width of about 1,600 kilometers (1,000 mi). A great [[rift valley]] also extends along the ridge over most of its length. The depth of water over the ridge is less than 2,700 m (8,900 ft) in most places, and several mountain peaks rise above the water and form islands. The South Atlantic Ocean has an additional submarine ridge, the [[Walvis Ridge]]. |
| − | The Mid-Atlantic Ridge separates the Atlantic Ocean into two large [[trough (geology)| | + | The Mid-Atlantic Ridge separates the Atlantic Ocean into two large [[trough (geology)|troughs]] with depths averaging between 3,700 and 5,500 metres (12,000 and 18,000 ft). Transverse ridges running between the continents and the Mid-Atlantic Ridge divide the ocean floor into numerous basins. Some of the larger basins are the Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic. The largest South Atlantic basins are the Angola, Cape, Argentina, and Brazil basins. |
| − | The deep ocean floor is thought to be fairly flat, although numerous [[seamount]]s and some [[guyot]]s exist. Several deeps or trenches are also found on the ocean floor. The Puerto Rico Trench, in the North Atlantic, is the deepest. The [[Laurentian Abyss]] is found off the eastern coast of Canada. In the | + | The deep ocean floor is thought to be fairly flat, although numerous [[seamount]]s and some [[guyot]]s exist. Several deeps or trenches are also found on the ocean floor. The Puerto Rico Trench, in the North Atlantic, is the deepest. The [[Laurentian Abyss]] is found off the eastern coast of [[Canada]]. In the South Atlantic, the [[South Sandwich Trench]] reaches a depth of 8,428 metres (27,651 ft). A third major trench, the [[Romanche Trench]], is located near the [[equator]] and reaches a depth of about 7,454 meters (24,455 ft). The shelves along the margins of the continents constitute about 11% of the bottom topography. Several deep channels cut across the continental rise. |
| − | Ocean [[sediment]]s are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land and then washed to sea. These materials are | + | Ocean [[sediment]]s are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land and then washed to sea. These materials are found mostly on the [[continental shelf|continental shelves]] and are thickest off the mouths of large rivers or off desert coasts. Pelagic deposits, which contain the remains of organisms that sink to the ocean floor, include red clays and [[Globigerinida|Globigerina]], [[pteropod]], and siliceous oozes. Covering most of the ocean floor and ranging in thickness from 60 to 3,300 meters (200 to 11,000 ft), they are thickest in the convergence belts and in the zones of upwelling. Authigenic deposits consist of such materials as [[manganese nodule]]s. They occur where sedimentation proceeds slowly or where currents sort the deposits. |
| − | ==Water characteristics== | + | ==Water characteristics== |
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| − | The Atlantic Ocean | + | <!-- Unsourced image removed: [[Image:Capespearnew.jpg|250px|thumb|right|The Atlantic Ocean at [[Cape Spear]], Newfoundland]] —> |
| + | [[Image:Ireland-AtlanticOceanwithAranIsland.jpg|thumb|right|200px|The Atlantic Ocean as seen from the west coast of [[Ireland]] on a fair day]] | ||
| − | [[ | + | On average, the Atlantic is the saltiest of the world's major oceans; the [[salinity]] of the surface waters in the open ocean ranges from 33 to 37 parts per thousand (3.3 - 3.7%) by mass and varies with latitude and season. Surface salinity values are influenced by evaporation, precipitation, river inflow, and melting of [[sea ice]]. Although the minimum salinity values are found just north of the equator (because of heavy tropical rainfall), in general the lowest values are in the high latitudes and along coasts where large rivers flow into the ocean. Maximum salinity values occur at about 25° north and south of the equator, in [[subtropical]] regions with low rainfall and high evaporation. |
| − | + | Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar energy, range from less than −2 °[[Celsius|C]] to 29 °C (28 °[[Fahrenheit|F]] to 84 °F). <!-- less than 2 is not −2, but assuming less than -2 intended, degree signs butt to letter with space from number —> Maximum temperatures occur north of the equator, and minimum values are found in the polar regions. In the middle latitudes, the area of maximum temperature variations, values may vary by 7 °C to 8 °C (13°F to 14°F). | |
| − | + | The Atlantic Ocean consists of four major water masses. The North and South Atlantic central waters constitute the surface waters. The sub-Antarctic intermediate water extends to depths of 1,000 meters (3,300 ft). The [[North Atlantic Deep Water]] reaches depths of as much as 4,000 meters (13,200 ft). The [[Antarctic Bottom Water]] occupies ocean basins at depths greater than 4,000 meters (13,200 ft). | |
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| + | Within the North Atlantic, ocean currents isolate a large elongated body of water known as the [[Sargasso Sea]], in which the salinity is noticeably higher than average. The Sargasso Sea contains large amounts of [[seaweed]] and is also the spawning ground for both the [[European eel]] and the [[American eel]]. | ||
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| + | Because of the [[Coriolis effect]], water in the North Atlantic circulates in a clockwise direction, whereas water circulation in the South Atlantic is counter-clockwise. The south [[tide]]s in the Atlantic Ocean are semi-[[diel|diurnal]]; that is, two high tides occur during each 24 lunar hours. The tides are a general wave that moves from south to north. In latitudes above 40° North some east-west oscillation occurs. | ||
==Climate== | ==Climate== | ||
| − | [[Image:Atlantic hurricane graphic.gif|frame|right|Waves in the trade | + | [[Image:Atlantic hurricane graphic.gif|frame|right|Waves in the [[trade wind]]s in the Atlantic Ocean—areas of converging winds that move along the same track as the prevailing wind—create instabilities in the atmosphere that may lead to the formation of hurricanes]] |
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| − | + | The climate of the Atlantic Ocean and adjacent land areas is influenced by the temperatures of the surface waters and water currents as well as the winds blowing across the waters. Because of the ocean's great capacity for retaining heat, maritime climates are more moderate and have less tendancy toward extreme seasonal variations than inland climates. [[Precipitation (meteorology)|Precipitation]] can be approximated from coastal weather data and air temperature from the water temperatures. The oceans are the major source of the atmospheric moisture that is obtained through evaporation. Climatic zones vary with latitude; the warmest climatic zones stretch across the Atlantic north of the equator. The coldest zones are in the high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents contribute to climatic control by transporting warm and cold waters to other regions. Adjacent land areas are affected by the winds that are cooled or warmed when blowing over these currents. The [[Gulf Stream]], for example, warms the atmosphere of the British Isles and north-western Europe, and the cold water currents contribute to heavy fog off the coast of north-eastern Canada (the [[Grand Banks]] area) and the north-western coast of Africa. In general, winds tend to transport moisture and warm or cool air over land areas. [[Tropical cyclone|Hurricanes]] develop in the southern part of the North Atlantic Ocean. The average wavelength towards the North America shore about 500 m (1650 ft) out is 1000. | |
| − | The Atlantic Ocean | ||
| − | + | ==History== | |
| + | [[Image:Pangea animation 03.gif|thumb|left|240px|Pangaea separation animation, which formed the Atlantic Ocean known today. ]] | ||
| + | The Atlantic Ocean appears to be the second youngest of the world's oceans, after the [[Southern Ocean]]. Evidence indicates that it did not exist prior to 130 million years ago, when the continents that formed from the breakup of the ancestral supercontinent, [[Pangaea]], were being rafted apart by the process of seafloor spreading. The Atlantic has been extensively explored since the earliest settlements were established along its shores. The [[Vikings]], the [[Portugal|Portuguese]], and [[Christopher Columbus]] were the most famous among its early explorers. After Columbus, European exploration rapidly accelerated, and many new trade routes were established. As a result, the Atlantic became and remains the major artery between [[Europe]] and the [[Americas]] (known as [[transatlantic]] trade). Numerous scientific explorations have been undertaken, including those by the German Meteor expedition, [[Columbia University]]'s Lamont Geological Observatory, and the [[United States Navy]] [[Hydrographic office#United States|Hydrographic Office]]. | ||
| − | *In | + | Some important events in relation to the Atlantic: |
| − | * | + | *In 1858, the first [[transatlantic telegraph cable]] was laid by [[Cyrus Field]]. |
| − | *Later in | + | *On April 14 1912 the [[RMS Titanic]] sank after hitting an [[iceberg]] with loss of 1,593 people. |
| − | *In | + | *In 1919, the American [[NC-4]] became the first [[fixed-wing aircraft|airplane]] to cross the Atlantic (though it made a couple of landings on islands along the way). |
| − | *In | + | *Later in 1919, a British [[airplane]] piloted by [[Alcock and Brown]] made the first non-stop transatlantic flight, from [[Newfoundland]] to [[Ireland]]. |
| − | *The first transatlantic [[telephone]] call was made on | + | *In 1921, the [[United Kingdom|British]] were the first to cross the North Atlantic in an [[airship]]. |
| − | *In | + | *In 1922, the [[Portuguese people|Portuguese]] were the first to cross the South Atlantic in an airship. |
| − | *After rowing for 81 days and 2,962 | + | *The first transatlantic [[telephone]] call was made on January 7, 1927. |
| + | *In 1927, [[Charles Lindbergh]] made the first solo non-stop transatlantic flight in an airplane (between [[New York City]] and [[Paris]]). | ||
| + | *In 1952, [[Ann Davison]] was the first woman to single-handedly [[sail]] the Atlantic Ocean. | ||
| + | *In 1994, [[Guy Delage]] was the first man to swim across the Atlantic Ocean, from the [[Cape Verde islands]] to [[Barbados]]. | ||
| + | *In 1998, [[Benoit Lecomte]] was the first man to swim across the northern Atlantic Ocean, stopping for only one week in the [[Azores]]. | ||
| + | *After rowing for 81 days and 4,767 kilometers (2,962 mi), on December 3, 1999, [[Tori Murden]] became the first woman to cross the Atlantic Ocean by [[rowboat]] alone when she reached [[Guadeloupe]] from the [[Canary Islands]]. | ||
| + | ==Economy== | ||
| + | The ocean has also contributed significantly to the development and economy of the countries around it. Besides its major transatlantic transportation and communication routes, the Atlantic offers abundant [[petroleum]] deposits in the [[sedimentary rock]]s of the continental shelves and the world's richest fishing resources, especially in the waters covering the shelves. The major species of fish caught are [[cod]], [[haddock]], [[hake]], [[herring]], and [[mackerel]]. The most productive areas include the Grand Banks of [[Newfoundland]], the shelf area off [[Nova Scotia]], [[Georges Bank]] off [[Cape Cod]], the Bahama Banks, the waters around Iceland, the [[Irish Sea]], the [[Dogger Bank]] of the North Sea, and the Falkland Banks. [[Eel]], [[lobster]], and [[whale]]s have also been taken in great quantities. All these factors, taken together, tremendously enhance the Atlantic's great commercial value. Because of the threats to the ocean environment presented by oil spills, [[marine debris]], and the incineration of toxic wastes at sea, various international treaties exist to reduce some forms of pollution. | ||
| + | <!-- This would be good if it were in an infobox | ||
'''Location:''' | '''Location:''' | ||
| − | body of water between | + | body of water between Africa, [[Europe]], the [[Southern Ocean]], and the [[Americas]] |
'''[[Geographic coordinates]]:''' {{coor dm|0|00|N|25|00|W|}} | '''[[Geographic coordinates]]:''' {{coor dm|0|00|N|25|00|W|}} | ||
| Line 63: | Line 75: | ||
'''Area:''' | '''Area:''' | ||
| − | * ''total:'' [[1 | + | * ''total:'' [[1 E+13 m²|76.762 million km²]] (29.637 million mi²) |
| − | * ''note:'' includes the [[Baltic Sea]], [[Black Sea]], [[Caribbean Sea]], [[Davis Strait]], [[Denmark Strait]], part of the [[Drake Passage]], [[Gulf of Mexico]], [[Mediterranean Sea]], [[North Sea]], [[Norwegian Sea]], almost all of the [[Scotia Sea]], and other tributary water bodies | + | * ''note:'' includes the [[Baltic Sea]], [[Black Sea]], [[Caribbean Sea]], [[Davis Strait]], [[Denmark Strait]], part of the [[Drake Passage]], [[Gulf of Mexico]], [[Labrador Sea]], [[Mediterranean Sea]], [[North Sea]], [[Norwegian Sea]], almost all of the [[Scotia Sea]], and other tributary water bodies |
'''Area - comparative:''' | '''Area - comparative:''' | ||
| − | slightly less than 6.5 times the size of the [[United States | + | slightly less than 6.5 times the size of the [[United States]] |
'''Coastline:''' | '''Coastline:''' | ||
| − | 111 | + | 111 866 km (69,510 mi) |
'''Climate:''' | '''Climate:''' | ||
| − | Tropical cyclones ([[hurricane]]s) develop anywhere from off the coast of Africa near [[Cape Verde]] to the [[Windward Islands]] and move westward into the | + | Tropical cyclones ([[hurricane]]s) develop anywhere from off the coast of Africa near [[Cape Verde]] to the [[Windward Islands]] and move westward into the Caribbean Sea or up the east coast of [[North America]]; hurricanes can occur from May to December but are most frequent from late July to early November. Storms are common in the North Atlantic during northern winters, making ocean crossings more difficult and dangerous. |
| + | —> | ||
==Terrain== | ==Terrain== | ||
| − | The surface is usually covered with sea ice in the [[Labrador Sea]], | + | [[Image:Atlantic bathymetry.jpg|thumb|300px|Atlantic [[bathymetry]]]] |
| + | The surface is usually covered with sea ice in the [[Labrador Sea]], Denmark Strait, and Baltic Sea from October to June. There is a clockwise warm-water [[gyre]] in the northern Atlantic, and a counter-clockwise warm-water gyre in the southern Atlantic. The ocean floor is dominated by the [[Mid-Atlantic Ridge]], a rugged north-south centerline for the entire Atlantic basin, first discovered by the [[Challenger Expedition]]. This was formed by the vulcanism that also formed the floor of the Atlantic, and the islands rising from it. | ||
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| + | The Atlantic Ocean has irregular coasts indented by numerous bays, gulfs, and seas. These include Norwegian Sea, Baltic Sea, North Sea, Labrador Sea, [[Black Sea]], [[Gulf of St. Lawrence]], [[Bay of Fundy]], [[Gulf of Maine]], Mediterranean Sea, Gulf of Mexico, and Caribbean Sea. | ||
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| + | Islands in the Atlantic Ocean include [[Greenland]], [[Iceland]], [[Faroe Islands]], [[The British Isles]] (including [[Great Britain]], [[Ireland]] and numerous surrounding islands), [[Rockall]], [[Newfoundland]], [[Sable Island]], [[Azores]], [[Madeira Islands]], [[Bermuda]], [[Canaries]], [[West Indies]], [[Cape Verde Islands]], [[Sao Tome e Principe]], [[Annobon]], [[St. Peter and Paul Rocks]], [[Fernando de Noronha]], [[Atol das Rocas]], [[Ascension Island|Ascension]], [[Saint Helena (Britain)|St. Helena]], [[Trindade and Martim Vaz]], [[Tristan da Cunha]], [[Gough Island]], [[Falkland Islands]], [[Tierra del Fuego]], [[South Georgia Island]], [[South Sandwich Islands]], and [[Bouvet Island]]. | ||
===Elevation extremes=== | ===Elevation extremes=== | ||
| − | *''lowest point:'' [[Milwaukee Deep]] in the | + | *''lowest point:'' [[Milwaukee Deep]] in the Puerto Rico Trench −8,605 metres (28,232 ft) |
| − | *''highest point:'' sea level 0 m | + | *''highest point:'' sea level, 0 m (0 ft) |
===Natural resources=== | ===Natural resources=== | ||
| − | + | Petroleum and [[gas]] fields, [[fish]], marine mammals ([[seal (mammal)|seals]] and whales), sand and gravel aggregates, [[placer deposit]]s, [[polymetallic nodules]], precious stones | |
===Natural hazards=== | ===Natural hazards=== | ||
| − | [[Iceberg]]s are common in the [[Davis Strait]], [[Denmark Strait]], and the northwestern Atlantic Ocean from February to August and have been spotted as far south as [[Bermuda]] and the [[Madeira Islands]]. Ships are subject to [[superstructure#Engineering concept|superstructure]] [[icing (nautical)|icing]] in extreme northern Atlantic from October to May. Persistent fog can be a maritime hazard from May to September | + | [[Iceberg]]s are common in the [[Davis Strait]], [[Denmark Strait]], and the northwestern Atlantic Ocean from February to August and have been spotted as far south as [[Bermuda]] and the [[Madeira Islands]]. Ships are subject to [[superstructure#Engineering concept|superstructure]] [[icing (nautical)|icing]] in extreme northern Atlantic from October to May. Persistent fog can be a maritime hazard from May to September, as can hurricanes north of the equator (May to December). |
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| + | The [[Bermuda Triangle]] is popularly believed to be the site of numerous aviation and shipping incidents because of unexplained and supposedly mysterious causes, but coast guard records do not support this belief. | ||
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| + | ==Current environmental issues== | ||
| + | Endangered marine species include the [[manatee]], seals, [[sea lion]]s, [[turtle]]s, and whales. [[Drift net]] fishing is killing [[dolphin]]s, [[albatross]]es and other seabirds ([[petrel]]s, [[auk]]s), hastening the decline of fish stocks and contributing to international disputes <ref> animallaw.info: Problems and Prospects for the Pelagic Driftnet [http://www.animallaw.info/articles/arus12bcenvtlafflrev473.htm]</ref>. There is municipal sludge pollution off the eastern [[United States]], southern Brazil, and eastern [[Argentina]]; oil pollution in the Caribbean Sea, Gulf of Mexico, [[Lake Maracaibo]], Mediterranean Sea, and North Sea; and industrial waste and municipal sewage pollution in the Baltic Sea, North Sea, and Mediterranean Sea. | ||
| + | |||
| + | In 2005, there was some concern that the currents warming northern Europe were slowing down, but no scientific consensus was formed based on the reported evidence.<ref>[http://www.npr.org/templates/story/story.php?storyId=5033329 Atlantic Ocean's 'Heat Engine' Chills Down] by Christopher Joyce. All Things Considered, National Public Radio, 30 Nov, 2005.</ref> | ||
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| + | On June 7, 2006, Florida's wildlife commission voted to take the manatee off of the state's endangered species list. Some environmentalists worry that this could erode safeguards for the popular sea creature. | ||
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| + | ===Marine Pollution=== | ||
| + | {{main|Marine pollution}} | ||
| + | Marine pollution is a generic term for the harmful entry into the ocean of chemicals or particles. The biggest culprit are rivers that empty into the Ocean, and with it the many chemicals used as [[fertilizers]] in agriculture as well as waste from [[livestock]] and [[humans]]. The excess of oxygen depleting chemicals in the water leads to [[hypoxia]] and the creation of a [[dead zone (ecology)|dead zone]].<ref>Gerlach: Marine Pollution, Springer, Berlin (1975)</ref> | ||
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| + | {{see also|Ship pollution}} | ||
| − | + | ==Major ports and harbours== | |
| − | + | {{main|List of ports and harbours of the Atlantic Ocean}} | |
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| − | == | + | ==References== |
| − | + | <!--This article uses the Cite.php citation mechanism. If you would like more information on how to add references to this article, please see http://meta.wikimedia.org/wiki/Cite/Cite.php —> | |
| + | <div class="references-small"><references/> | ||
| + | </div> | ||
| − | + | Much of this article comes from the public domain site <nowiki>http://oceanographer.navy.mil/atlantic.html</nowiki> ([[dead link]]). It is now accessible from the [[Internet Archive]] at http://web.archive.org/web/20020221215514/http%3a//oceanographer.navy.mil/atlantic.html. | |
| − | + | * Disclaimers for this website, including its status as a public domain resource, are recorded on the Internet Archive at http://web.archive.org/web/20020212021049/http%3a//oceanographer.navy.mil/warning.html. | |
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| − | == | + | ==See also== |
| − | [[ | + | {{wikisource|CIA World Fact Book, 2004/Atlantic Ocean}} |
| + | *[[Transatlantic]] | ||
| + | **[[Transatlantic flight]] | ||
| + | *[[List of islands in the Atlantic Ocean]] | ||
| + | *[[:Category:Shipwrecks in the Atlantic Ocean]] | ||
| + | *[[:Category:Atlantic hurricanes]] | ||
| + | *[[Ocean Highway]] | ||
==External links== | ==External links== | ||
| − | {{Commons| | + | {{Commons|Atlantic Ocean}} |
| − | * | + | * [http://www.latimes.com/news/local/oceans/la-oceans-series,0,7842752.special LA Times special Altered Oceans] |
| − | * | + | * [http://www.whoi.edu/imageOfDay.do Oceanography Image of the Day ], from the Woods Hole Oceanographic Institution |
| − | *[http://www.cia.gov/ | + | * [http://dapper.pmel.noaa.gov/dchart/ NOAA In-situ Ocean Data Viewer] Plot and download ocean observations |
| + | *[https://www.cia.gov/library/publications/the-world-factbook/geos/zh.html CIA – The World Factbook – Atlantic Ocean] | ||
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| + | [[Category:Atlantic Ocean| ]] | ||
| − | [[ | + | [[be-x-old:Атлянтычны акіян]] |
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| − | {{credit| | + | {{credit|140718159}} |
Revision as of 12:37, 26 June 2007
|
| Earth's oceans |
|---|
- "Atlantic" redirects here.
The Atlantic Ocean is the second-largest of the world's oceanic divisions; with a total area of about 106.4 million square kilometres (41.1 million square miles), it covers approximately one-fifth of the Earth's surface. Its name, derived from Greek mythology, means the "Sea of Atlas." The oldest known mention of this name is contained in The Histories of Herodotus around 450 B.C.E. (I 202).
The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between the Americas to the west, and Eurasia and Africa to the east. A component of the all-encompassing World Ocean, it is connected in the north to the Arctic Ocean (which is sometimes considered a sea of the Atlantic), to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south. (Alternatively, in lieu of it connecting to the Southern Ocean, the Atlantic may be reckoned to extend southward to Antarctica.) The equator subdivides it into the North Atlantic Ocean and South Atlantic Ocean.
Geography
The Atlantic Ocean is bounded on the west by North and South America. In the north and northeast, it is separated from the Arctic Ocean by the Canadian Arctic Archipelago, Greenland, Iceland, Jan Mayen, Svalbard, and mainland Europe. It connects to the Arctic Ocean through the Denmark Strait, Greenland Sea, Norwegian Sea, and Barents Sea. To the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltar (where it connects with the Mediterranean Sea, one of its marginal seas, and, in turn, the Black Sea), and Africa. In the southeast, the Atlantic merges into the Indian Ocean, the border being defined by the 20° East meridian, running south from Cape Agulhas to Antarctica. While some authorities show the Atlantic Ocean extending south to Antarctica, others show it as bounded to the south by the Southern Ocean [1]. In the southwest, the Drake Passage connects it to the Pacific Ocean. A man-made link between the Atlantic and Pacific is provided by the Panama Canal. Beside those mentioned, other large bodies of water adjacent to the Atlantic are the Caribbean Sea, the Gulf of Mexico, Hudson Bay, the Mediterranean Sea, the North Sea, and the Baltic Sea.
Covering approximately 20% of Earth's surface, the Atlantic Ocean is second only to the Pacific in size. With its adjacent seas it occupies an area of about 106,400,000 square kilometers (41,100,000 sq mi); without them, it has an area of 82,400,000 square kilometers (31,800,000 sq mi). The land area that drains into the Atlantic is four times that of either the Pacific or Indian oceans. The volume of the Atlantic Ocean with its adjacent seas is 354,700,000 cubic kilometers (85,100,000 cu mi) and without them 323,600,000 cubic kilometers (77,640,000 cu mi).
The average depths of the Atlantic, with its adjacent seas, is 3,338 meters (10,932 ft); without them it is 3,926 meters (12,881 ft). The greatest depth, 8,605 meters (28,232 ft), is in the Puerto Rico Trench. The width of the Atlantic varies from 2,848 kilometers (1,770 mi) between Brazil and Liberia to about 4,830 kilometers (3,000 mi) between the United States and northern Africa.
Ocean bottom
The principal feature of the bottom bathymetry (terrain) of the Atlantic Ocean is a submarine mountain range called the Mid-Atlantic Ridge. It extends from Iceland in the north to approximately 58° South latitude, reaching a maximum width of about 1,600 kilometers (1,000 mi). A great rift valley also extends along the ridge over most of its length. The depth of water over the ridge is less than 2,700 m (8,900 ft) in most places, and several mountain peaks rise above the water and form islands. The South Atlantic Ocean has an additional submarine ridge, the Walvis Ridge.
The Mid-Atlantic Ridge separates the Atlantic Ocean into two large troughs with depths averaging between 3,700 and 5,500 metres (12,000 and 18,000 ft). Transverse ridges running between the continents and the Mid-Atlantic Ridge divide the ocean floor into numerous basins. Some of the larger basins are the Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic. The largest South Atlantic basins are the Angola, Cape, Argentina, and Brazil basins.
The deep ocean floor is thought to be fairly flat, although numerous seamounts and some guyots exist. Several deeps or trenches are also found on the ocean floor. The Puerto Rico Trench, in the North Atlantic, is the deepest. The Laurentian Abyss is found off the eastern coast of Canada. In the South Atlantic, the South Sandwich Trench reaches a depth of 8,428 metres (27,651 ft). A third major trench, the Romanche Trench, is located near the equator and reaches a depth of about 7,454 meters (24,455 ft). The shelves along the margins of the continents constitute about 11% of the bottom topography. Several deep channels cut across the continental rise.
Ocean sediments are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and rock particles formed by erosion, weathering, and volcanic activity on land and then washed to sea. These materials are found mostly on the continental shelves and are thickest off the mouths of large rivers or off desert coasts. Pelagic deposits, which contain the remains of organisms that sink to the ocean floor, include red clays and Globigerina, pteropod, and siliceous oozes. Covering most of the ocean floor and ranging in thickness from 60 to 3,300 meters (200 to 11,000 ft), they are thickest in the convergence belts and in the zones of upwelling. Authigenic deposits consist of such materials as manganese nodules. They occur where sedimentation proceeds slowly or where currents sort the deposits.
Water characteristics
On average, the Atlantic is the saltiest of the world's major oceans; the salinity of the surface waters in the open ocean ranges from 33 to 37 parts per thousand (3.3 - 3.7%) by mass and varies with latitude and season. Surface salinity values are influenced by evaporation, precipitation, river inflow, and melting of sea ice. Although the minimum salinity values are found just north of the equator (because of heavy tropical rainfall), in general the lowest values are in the high latitudes and along coasts where large rivers flow into the ocean. Maximum salinity values occur at about 25° north and south of the equator, in subtropical regions with low rainfall and high evaporation.
Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar energy, range from less than −2 °C to 29 °C (28 °F to 84 °F). Maximum temperatures occur north of the equator, and minimum values are found in the polar regions. In the middle latitudes, the area of maximum temperature variations, values may vary by 7 °C to 8 °C (13°F to 14°F).
The Atlantic Ocean consists of four major water masses. The North and South Atlantic central waters constitute the surface waters. The sub-Antarctic intermediate water extends to depths of 1,000 meters (3,300 ft). The North Atlantic Deep Water reaches depths of as much as 4,000 meters (13,200 ft). The Antarctic Bottom Water occupies ocean basins at depths greater than 4,000 meters (13,200 ft).
Within the North Atlantic, ocean currents isolate a large elongated body of water known as the Sargasso Sea, in which the salinity is noticeably higher than average. The Sargasso Sea contains large amounts of seaweed and is also the spawning ground for both the European eel and the American eel.
Because of the Coriolis effect, water in the North Atlantic circulates in a clockwise direction, whereas water circulation in the South Atlantic is counter-clockwise. The south tides in the Atlantic Ocean are semi-diurnal; that is, two high tides occur during each 24 lunar hours. The tides are a general wave that moves from south to north. In latitudes above 40° North some east-west oscillation occurs.
Climate
The climate of the Atlantic Ocean and adjacent land areas is influenced by the temperatures of the surface waters and water currents as well as the winds blowing across the waters. Because of the ocean's great capacity for retaining heat, maritime climates are more moderate and have less tendancy toward extreme seasonal variations than inland climates. Precipitation can be approximated from coastal weather data and air temperature from the water temperatures. The oceans are the major source of the atmospheric moisture that is obtained through evaporation. Climatic zones vary with latitude; the warmest climatic zones stretch across the Atlantic north of the equator. The coldest zones are in the high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents contribute to climatic control by transporting warm and cold waters to other regions. Adjacent land areas are affected by the winds that are cooled or warmed when blowing over these currents. The Gulf Stream, for example, warms the atmosphere of the British Isles and north-western Europe, and the cold water currents contribute to heavy fog off the coast of north-eastern Canada (the Grand Banks area) and the north-western coast of Africa. In general, winds tend to transport moisture and warm or cool air over land areas. Hurricanes develop in the southern part of the North Atlantic Ocean. The average wavelength towards the North America shore about 500 m (1650 ft) out is 1000.
History
The Atlantic Ocean appears to be the second youngest of the world's oceans, after the Southern Ocean. Evidence indicates that it did not exist prior to 130 million years ago, when the continents that formed from the breakup of the ancestral supercontinent, Pangaea, were being rafted apart by the process of seafloor spreading. The Atlantic has been extensively explored since the earliest settlements were established along its shores. The Vikings, the Portuguese, and Christopher Columbus were the most famous among its early explorers. After Columbus, European exploration rapidly accelerated, and many new trade routes were established. As a result, the Atlantic became and remains the major artery between Europe and the Americas (known as transatlantic trade). Numerous scientific explorations have been undertaken, including those by the German Meteor expedition, Columbia University's Lamont Geological Observatory, and the United States Navy Hydrographic Office.
Some important events in relation to the Atlantic:
- In 1858, the first transatlantic telegraph cable was laid by Cyrus Field.
- On April 14 1912 the RMS Titanic sank after hitting an iceberg with loss of 1,593 people.
- In 1919, the American NC-4 became the first airplane to cross the Atlantic (though it made a couple of landings on islands along the way).
- Later in 1919, a British airplane piloted by Alcock and Brown made the first non-stop transatlantic flight, from Newfoundland to Ireland.
- In 1921, the British were the first to cross the North Atlantic in an airship.
- In 1922, the Portuguese were the first to cross the South Atlantic in an airship.
- The first transatlantic telephone call was made on January 7, 1927.
- In 1927, Charles Lindbergh made the first solo non-stop transatlantic flight in an airplane (between New York City and Paris).
- In 1952, Ann Davison was the first woman to single-handedly sail the Atlantic Ocean.
- In 1994, Guy Delage was the first man to swim across the Atlantic Ocean, from the Cape Verde islands to Barbados.
- In 1998, Benoit Lecomte was the first man to swim across the northern Atlantic Ocean, stopping for only one week in the Azores.
- After rowing for 81 days and 4,767 kilometers (2,962 mi), on December 3, 1999, Tori Murden became the first woman to cross the Atlantic Ocean by rowboat alone when she reached Guadeloupe from the Canary Islands.
Economy
The ocean has also contributed significantly to the development and economy of the countries around it. Besides its major transatlantic transportation and communication routes, the Atlantic offers abundant petroleum deposits in the sedimentary rocks of the continental shelves and the world's richest fishing resources, especially in the waters covering the shelves. The major species of fish caught are cod, haddock, hake, herring, and mackerel. The most productive areas include the Grand Banks of Newfoundland, the shelf area off Nova Scotia, Georges Bank off Cape Cod, the Bahama Banks, the waters around Iceland, the Irish Sea, the Dogger Bank of the North Sea, and the Falkland Banks. Eel, lobster, and whales have also been taken in great quantities. All these factors, taken together, tremendously enhance the Atlantic's great commercial value. Because of the threats to the ocean environment presented by oil spills, marine debris, and the incineration of toxic wastes at sea, various international treaties exist to reduce some forms of pollution.
Terrain
The surface is usually covered with sea ice in the Labrador Sea, Denmark Strait, and Baltic Sea from October to June. There is a clockwise warm-water gyre in the northern Atlantic, and a counter-clockwise warm-water gyre in the southern Atlantic. The ocean floor is dominated by the Mid-Atlantic Ridge, a rugged north-south centerline for the entire Atlantic basin, first discovered by the Challenger Expedition. This was formed by the vulcanism that also formed the floor of the Atlantic, and the islands rising from it.
The Atlantic Ocean has irregular coasts indented by numerous bays, gulfs, and seas. These include Norwegian Sea, Baltic Sea, North Sea, Labrador Sea, Black Sea, Gulf of St. Lawrence, Bay of Fundy, Gulf of Maine, Mediterranean Sea, Gulf of Mexico, and Caribbean Sea.
Islands in the Atlantic Ocean include Greenland, Iceland, Faroe Islands, The British Isles (including Great Britain, Ireland and numerous surrounding islands), Rockall, Newfoundland, Sable Island, Azores, Madeira Islands, Bermuda, Canaries, West Indies, Cape Verde Islands, Sao Tome e Principe, Annobon, St. Peter and Paul Rocks, Fernando de Noronha, Atol das Rocas, Ascension, St. Helena, Trindade and Martim Vaz, Tristan da Cunha, Gough Island, Falkland Islands, Tierra del Fuego, South Georgia Island, South Sandwich Islands, and Bouvet Island.
Elevation extremes
- lowest point: Milwaukee Deep in the Puerto Rico Trench −8,605 metres (28,232 ft)
- highest point: sea level, 0 m (0 ft)
Natural resources
Petroleum and gas fields, fish, marine mammals (seals and whales), sand and gravel aggregates, placer deposits, polymetallic nodules, precious stones
Natural hazards
Icebergs are common in the Davis Strait, Denmark Strait, and the northwestern Atlantic Ocean from February to August and have been spotted as far south as Bermuda and the Madeira Islands. Ships are subject to superstructure icing in extreme northern Atlantic from October to May. Persistent fog can be a maritime hazard from May to September, as can hurricanes north of the equator (May to December).
The Bermuda Triangle is popularly believed to be the site of numerous aviation and shipping incidents because of unexplained and supposedly mysterious causes, but coast guard records do not support this belief.
Current environmental issues
Endangered marine species include the manatee, seals, sea lions, turtles, and whales. Drift net fishing is killing dolphins, albatrosses and other seabirds (petrels, auks), hastening the decline of fish stocks and contributing to international disputes [2]. There is municipal sludge pollution off the eastern United States, southern Brazil, and eastern Argentina; oil pollution in the Caribbean Sea, Gulf of Mexico, Lake Maracaibo, Mediterranean Sea, and North Sea; and industrial waste and municipal sewage pollution in the Baltic Sea, North Sea, and Mediterranean Sea.
In 2005, there was some concern that the currents warming northern Europe were slowing down, but no scientific consensus was formed based on the reported evidence.[3]
On June 7, 2006, Florida's wildlife commission voted to take the manatee off of the state's endangered species list. Some environmentalists worry that this could erode safeguards for the popular sea creature.
Marine Pollution
Marine pollution is a generic term for the harmful entry into the ocean of chemicals or particles. The biggest culprit are rivers that empty into the Ocean, and with it the many chemicals used as fertilizers in agriculture as well as waste from livestock and humans. The excess of oxygen depleting chemicals in the water leads to hypoxia and the creation of a dead zone.[4]
Major ports and harbours
ReferencesISBN links support NWE through referral fees
- ↑ Limits of Oceans and Seas. International Hydrographic Organization Special Publication No. 23, 1953.
- ↑ animallaw.info: Problems and Prospects for the Pelagic Driftnet [1]
- ↑ Atlantic Ocean's 'Heat Engine' Chills Down by Christopher Joyce. All Things Considered, National Public Radio, 30 Nov, 2005.
- ↑ Gerlach: Marine Pollution, Springer, Berlin (1975)
Much of this article comes from the public domain site http://oceanographer.navy.mil/atlantic.html (dead link). It is now accessible from the Internet Archive at http://web.archive.org/web/20020221215514/http%3a//oceanographer.navy.mil/atlantic.html.
- Disclaimers for this website, including its status as a public domain resource, are recorded on the Internet Archive at http://web.archive.org/web/20020212021049/http%3a//oceanographer.navy.mil/warning.html.
See also
- Transatlantic
- Transatlantic flight
- List of islands in the Atlantic Ocean
- Category:Shipwrecks in the Atlantic Ocean
- Category:Atlantic hurricanes
- Ocean Highway
External links
- LA Times special Altered Oceans
- Oceanography Image of the Day , from the Woods Hole Oceanographic Institution
- NOAA In-situ Ocean Data Viewer Plot and download ocean observations
- CIA – The World Factbook – Atlantic Ocean
be-x-old:Атлянтычны акіян
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