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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 and about one-quarter of its water surface area. The first part of its name refers to the Atlas of Greek mythology, making the Atlantic the "Sea of Atlas". The oldest known mention of this name is contained in The Histories of Herodotus around 450 BCE (I 202); see also: Atlas Mountains. Another name historically used was the ancient term Ethiopic Oceanmarker, derived from Ethiopiamarker, whose name was sometimes used as a synonym for all of Africa and thus for the ocean. Before Europeans discovered other oceans, the term "ocean" itself was to them synonymous with the waters beyond Western Europe that we now know as the Atlantic and which the Greeks had believed to be a gigantic river encircling the world; see Oceanus.

The Atlantic Ocean occupies an elongated, S-shaped basin extendinglongitudinally 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 Oceanmarker (which is sometimes considered a sea of the Atlantic), to the Pacific Oceanmarker in the southwest, the Indian Oceanmarker in the southeast, and the Southern Oceanmarker in the south. (Alternatively, in lieu of it connecting to the Southern Ocean, the Atlantic may be reckoned to extend southward to Antarcticamarker.) The equator subdivides it into the North Atlantic Ocean and South Atlantic Ocean.



Geography

The Atlantic Ocean as seen from the western coast of Portugal
The Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Straitmarker, Greenland Seamarker, Norwegian Seamarker, and Barents Seamarker. To the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltarmarker (where it connects with the Mediterranean Seamarker, one of its marginal seas, and, in turn, the Black Seamarker), and Africa. In the southeast, the Atlantic merges into the Indian Ocean. The 20° East meridian, running south from Cape Agulhasmarker to Antarcticamarker defines its border. Some authorities show it extending south to Antarcticamarker, while others show it bounded at the 60° parallel by the Southern Ocean. In the southwest, the Drake Passagemarker connects it to the Pacific Ocean. The man-made Panama Canalmarker links the Atlantic and Pacific. Besides those mentioned, other large bodies of water adjacent to the Atlantic are the Caribbean Seamarker, the Gulf of Mexicomarker, Hudson Baymarker, the Arctic Ocean, the Mediterranean Sea, the North Seamarker, the Baltic Seamarker, and the Celtic Seamarker.

Covering approximately 22% of Earth's surface, the Atlantic is second in size to the Pacific. With its adjacent seas it occupies an area of about ; without them, it has an area of . The land that drains into the Atlantic covers four times that of either the Pacific or Indian oceans. The volume of the Atlantic with its adjacent seas is 354,700,000 cubic kilometers (85,100,000 cu mi) and without them 323,600,000 cubic kilometres (77,640,000 cu mi).

The average depth of the Atlantic, with its adjacent seas, is ; without them it is . The greatest depth, , is in the Puerto Rico Trenchmarker. The Atlantic's width varies from between Brazilmarker and Sierra Leonemarker to over in the south.

Cultural significance

Transatlantic travel played a major role in the expansion of Western civilization into the Americas. Today, it can be referred to in a humorously diminutive way as the Pond in idioms, in reference to the geographical and cultural divide between North America and Europe. Some British people refer to the USA as "across the pond".

Ocean bottom

Map that uses color to show ocean depth
The principal feature of the bathymetry (bottom topography) is a submarine mountain range called the Mid-Atlantic Ridge. It extends from Icelandmarker in the north to approximately 58° South latitude, reaching a maximum width of about . A great rift valley also extends along the ridge over most of its length. The depth of water over the ridge is less than 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 from . 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 Blakemarker, 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 Trenchmarker, in the North Atlantic, is the deepest at . The Laurentian Abyss is found off the eastern coast of Canadamarker. In the South Atlanticmarker, the South Sandwich Trench reaches a depth of . A third major trench, the Romanche Trench, is located near the equator and reaches a depth of about . 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 near large river mouths 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 they are thickest in the convergence belts and in upwelling zones. Authigenic deposits consist of such materials as manganese nodules. They occur where sedimentation proceeds slowly or where currents sort the deposits

Water characteristics

Map of the five major ocean gyres
On average, the Atlantic is the saltiest major ocean; surface water salinity in the open ocean ranges from 33 to 37 parts per thousand (3.3 - 3.7%) by mass and varies with latitude and season. Evaporation, precipitation, river inflow and sea ice melting influence surface salinity values. Although the salinity values are 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 enter. Maximum salinity values occur at about 25° north and south, 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 below . 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 .

The Atlantic Ocean consists of four major water masses. The North and South Atlantic central waters make up the surface. The sub-Antarctic intermediate water extends to depths of . The North Atlantic Deep Water reaches depths of as much as . The Antarctic Bottom Water occupies ocean basins at depths greater than 4,000 meters.

Within the North Atlantic, ocean currents isolate the Sargasso Seamarker, a large elongated body of water, with above average salinity. The Sargasso Sea contains large amounts of seaweed and is also the spawning ground for both the European eel and the American eel.

The Coriolis effect circulates North Atlantic water in a clockwise direction, whereas South Atlantic water circulates counter-clockwise. The south tides in the Atlantic Ocean are semi-diurnal; that is, two high tides occur during each 24 lunar hours. In latitudes above 40° North some east-west oscillation occurs.

Climate



Climate is influenced by the temperatures of the surface waters and water currents as well as winds. Because of the ocean's great heat retention capacity, maritime climates are more moderate and have less extreme seasonal variations than inland climates. Precipitation can be approximated from coastal weather data and air temperature from water temperatures. The oceans are the major source of the atmospheric moisture that is obtained through evaporation. Climatic zones vary with latitude; the warmest zones stretch across the Atlantic north of the equator. The coldest zones are in high latitudes, with the coldest regions corresponding to the areas covered by sea ice. Ocean currents influence climate by transporting warm and cold waters to other regions. The winds that are cooled or warmed when blowing over these currents influence adjacent land areas. The Gulf Stream and its northern extension towards Europe, the North Atlantic Drift, 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 eastern Canada (the Grand Banks of Newfoundlandmarker area) and Africa's north-western coast. In general, winds transport moisture and air over land areas. Hurricanes develop in the southern part of the North Atlantic Ocean.

History

The Atlantic Ocean appears to be the second youngest of the five oceans. Apparently it did not exist prior to 130 million years ago, when the continents that formed from the breakup of the ancestral super continent, Pangaea, were drifting apart from seafloor spreading. The Atlantic has been extensively explored since the earliest settlements along its shores. The Vikings, the Portuguesemarker, and Christopher Columbus were the most famous among 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). Scientific explorations include the Challenger expedition, the German Meteor expedition, Columbia University's Lamont-Doherty Earth Observatorymarker and the United States Navy Hydrographic Office.

Notable crossings



Ethiopic Ocean

The Ethiopic Ocean or Ethiopian Ocean (Okeanos Aithiopos) is an old name for what is now called the South Atlantic Ocean, which is separated from the North Atlantic Ocean by a narrow region between Natal, Brazilmarker and Monrovia, Liberiamarker. Use of this term illustrates a past trend towards referring to the whole continent of Africa by the name Aethiopia. The modern nation of Ethiopia, in northeast Africa, is nowhere near the Ethiopic Ocean, which would be said to lie off the west coast of Africa. The term Ethiopian Ocean sometimes appeared until the mid-19th century.

Economy

The Atlantic has contributed significantly to the development and economy of surrounding countries. Besides major transatlantic transportation and communication routes, the Atlantic offers abundant petroleum deposits in the sedimentary rocks of the continental shelves. The Atlantic hosts the world's richest fishing resources, especially in the waters covering the shelves. The major fish are cod, haddock, hake, herring, and mackerel. The most productive areas include Newfoundlandmarker's Grand Banksmarker, the Nova Scotiamarker shelf , Georges Bankmarker off Cape Codmarker, the Bahama Banksmarker, the waters around Iceland, the Irish Seamarker, the Dogger Bankmarker of the North Sea, and the Falkland Banks. Eel, lobster, and whales appear in great quantities. Because environmental threats from oil spills, marine debris, and the incineration of toxic wastes at sea, various international treaties attempt to reduce pollution.

Terrain

From October to June the surface is usually covered with sea ice in the Labrador Seamarker, Denmark Straitmarker, and Baltic Seamarker. A clockwise warm-water gyre occupies the northern Atlantic, and a counter-clockwise warm-water gyre appears in the southern Atlantic. The Mid-Atlantic Ridge , a rugged north-south centerline for the entire Atlantic basin, first discovered by the Challenger Expedition dominates the ocean floor. This was formed by the vulcanism that also formed the ocean floor and the islands rising from it.

The Atlantic has irregular coasts indented by numerous bays, gulfs, and seas. These include the Norwegian Seamarker, Baltic Seamarker, North Seamarker, Labrador Seamarker, Black Seamarker, Gulf of Saint Lawrencemarker, Bay of Fundymarker, Gulf of Mainemarker, Mediterranean Seamarker, Gulf of Mexicomarker, and Caribbean Seamarker.

Islands include Greenlandmarker, Icelandmarker, Faroe Islandsmarker, Great Britainmarker (including numerous surrounding islands), Irelandmarker, Rockallmarker, Newfoundlandmarker, Sable Islandmarker, Azores, Madeiramarker, Bermudamarker, Canary Islandsmarker, Caribbeanmarker, Cape Verdemarker, São Tomé and Príncipemarker, Annobón Provincemarker, St. Peter Islandmarker, Fernando de Noronhamarker, Rocas Atollmarker, Ascension Islandmarker, Saint Helena, The Islands of Trindadmarker, Tristan da Cunhamarker, Gough Islandmarker (Also known as Diego Alvarez), Falkland Islandsmarker, Tierra del Fuegomarker, South Georgia Island, South Sandwich Islands, and Bouvet Islandmarker.

Natural resources

The Atlantic harbors petroleum and gas fields, fish, marine mammals (seals and whales), sand and gravel aggregates, placer deposits, polymetallic nodules, and precious stones.

Natural hazards

Iceberg A22A in the South Atlantic Ocean
Icebergs are common from February to August in the Davis Straitmarker, Denmark Straitmarker, and the northwestern Atlantic and have been spotted as far south as Bermudamarker and Madeiramarker. Ships are subject to superstructure icing in the extreme north 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 United States' southeast coast has a long history of shipwrecks due to its many shoals and reefs. The Virginia and North Carolina coasts were particularly dangerous.

The Bermuda Trianglemarker 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 can kill dolphins, albatrosses and other seabirds (petrels, auks), hastening the fish stock decline and contributing to international disputes. Municipal pollution comes from the eastern United Statesmarker, southern Brazilmarker, and eastern Argentinamarker; oil pollution in the Caribbean Seamarker, Gulf of Mexicomarker, Lake Maracaibomarker, Mediterranean Seamarker, and North Seamarker; and industrial waste and municipal sewage pollution in the Baltic Seamarker, North Seamarker, and Mediterranean Seamarker.

In 2005, there was some concern that warm northern European currents were slowing down, but no scientific consensus formed from that evidence.

On June 7, 2006, Florida's wildlife commission voted to take the manatee off 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 entry into the ocean of potentially hazardous chemicals or particles. The biggest culprits are rivers and with them many agriculture fertilizer chemicals as well as livestock and human waste. The excess of oxygen-depleting chemicals leads to hypoxia and the creation of a dead zone.

Marine debris, also known as marine litter, describes human-created waste floating in a body of water. Oceanic debris tends to accumulate at the center of gyres and coastlines, frequently washing aground where it is known as beach litter.

Major ports and harbours

See also



References

  1. Limits of Oceans and Seas. International Hydrographic Organization Special Publication No. 23, 1953.
  2. Example: BBC Click - Episode 04 April 2009
  3. http://ap.google.com/article/ALeqM5gtFxhb2bKIQLIxaRF0qB0x7k4yvgD93RLE680
  4. "Introduction" U-Boat Operations of the Second World War—Vol 1 by Wynn, Kenneth, 1998 p. 1
  5. animallaw.info: Problems and Prospects for the Pelagic Driftnet
  6. Atlantic Ocean's 'Heat Engine' Chills Down by Christopher Joyce. All Things Considered, National Public Radio, 30 Nov, 2005.
  7. Gerlach: Marine Pollution, Springer, Berlin (1975)


http://www.cartage.org.lb/en/themes/geoghist/histories/history/hiscountries/A/atlanticocean.html

http://www.mnsu.edu/emuseum/information/oceans/atlantic.html

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 Archivemarker 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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