Atlantic Ocean

Atlantic Ocean

Atlantic Ocean [Lat.,=of Atlas], second largest ocean (c.31,800,000 sq mi/82,362,000 sq km; c.36,000,000 sq mi/93,240,000 sq km with marginal seas).

Physical Geography

Extent and Seas

The Atlantic Ocean extends in an S shape from the arctic to the antarctic regions between North and South America on the west and Europe and Africa on the east. It is connected with the Arctic Ocean by the Greenland Sea and Smith Sound; with the Pacific Ocean by Drake Passage, the Straits of Magellan, and the Panama Canal; and with the Indian Ocean by the Suez Canal and the expanse between Africa and Antarctica. The shortest distance across the Atlantic Ocean (c.1,600 mi/2,575 km) is between SW Senegal, W Africa, and NE Brazil, E South America. The principal arms of the Atlantic Ocean are Hudson and Baffin bays, the Gulf of Mexico, and the Caribbean Sea in the west; the Baltic, North, Mediterranean, and Black seas in the east; and the Weddell Sea in the south. More large rivers, including the Mississippi, the Congo, and the Amazon, drain into the Atlantic than into any other ocean.


The Atlantic has relatively few islands, with the greatest concentration found in the Caribbean region. Most of the islands are structurally part of the continents, such as the British Isles, Falkland Islands, Canary Islands, and Newfoundland. Iceland, the Azores, the islands of Cape Verde, Ascension, the South Sandwich Islands, the West Indies, and Bermuda are exposed tops of submarine ridges. The Bahamas are low coral islands that sit on the Blake Plateau, while the Madeiras are high volcanic islands.

Ocean Floor

The floor of the Atlantic has an average depth of c.12,000 ft (3,660 m). It is separated from that of the Arctic Ocean by a submarine ridge extending from SE Greenland to N Scotland; part of the floor (c.3,000 ft/910 m deep) is known as "telegraph plateau" because of the network of cables laid there. A shallow submarine ridge across the Strait of Gibraltar separates the Mediterranean basin from the Atlantic and limits the exchange of water between the two bodies. The Mid-Atlantic Ridge (c.300-600 mi/480-970 km wide), a submarine mountain range extending c.10,000 mi (16,100 km) from Iceland to near the Antarctic Circle, generally follows the trend of the coastlines of the continents. It rises to an average height of c.10,000 ft (3,050 m), and a few peaks emerge as islands. The ridge, which is the center of volcanic activity and earthquakes, has a great rift that is constantly widening (see seafloor spreading) and filling with molten rock from the earth's interior. As a result the Western Hemisphere and Europe and Africa are moving away from each other. The Mid-Atlantic Ridge divides the floor of the Atlantic Ocean into eastern and western sections that are composed of a series of deep-sea basins (abyssal plains). The greatest depth (c.28,000 ft/8,530 m) is the Milwaukee Deep, in the Puerto Rico Trench, N of Puerto Rico. Scientific knowledge of the ocean floor dates from the Challenger expedition (1872-76).


Because of its shape, the Atlantic may be divided into two basins—North Atlantic Ocean and South Atlantic Ocean—each with a distinct circulation system. The clockwise-moving currents of the North Atlantic (North Equatorial Current, Antilles Current, Gulf Stream, North Atlantic Drift, Canaries Current) and the counterclockwise-moving currents of the South Atlantic (South Equatorial Current, Brazil Current, West Wind Drift, Benguela Current) are separated from each other by the Equatorial Counter Current; the Guinea Current off W Africa is a link between the two systems. At the Grand Banks off Newfoundland heavy fogs form along the front where the warm Gulf Stream meets the cold Labrador Current. The surface waters in the Atlantic's trade wind belts attain the highest salinity known in ocean water.

Commerce and Shipping

The North Atlantic Ocean has some of the world's busiest shipping lanes; the northern lanes are patrolled for icebergs. Commerce between the Mediterranean Sea and the NE Atlantic Ocean was initiated by the Carthaginians. From the 7th cent. A.D., Scandinavians navigated the Atlantic; they probably reached North America c.1000. Trade routes along the coast of Africa were opened by Portugal in the 15th cent. and to the Western Hemisphere by Spain after the voyages of Columbus. The Grand Banks have traditionally contained some of the world's best commercial fishing grounds, but by the early 1990s the area had been overfished, and many species were depleted.


See V. H. Cassidy, The Sea Around Them: The Atlantic Ocean, A.D. 1250 (1968); K. F. George, The Atlantic Ocean (1977); K. O. Emery and E. Uchupi, The Geology of the Atlantic Ocean (1984).

Ocean separating North and South America from Europe and Africa. The second largest of the world's oceans, the Atlantic has an area of 31,830,000 sq mi (82,440,000 sq km). With its marginal seas, including the Baltic, North, Black, and Mediterranean to the east, and Baffin Bay, Hudson Bay, the Gulf of St. Lawrence, Gulf of Mexico, and Caribbean Sea to the west, it covers some 41,100,000 sq mi (106,450,000 sq km). Including these latter bodies of water, its average depth is 10,925 ft (3,330 m); its maximum depth is 27,493 feet (8,380 m) in the Puerto Rico Trench. Its most powerful current is the Gulf Stream.

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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. 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 BC (I 202); see also: Atlas Mountains. Another name historically used was the ancient term Ethiopic Ocean, derived from Ethiopia, 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 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.


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 at the 60° parallel by the Southern Ocean. 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 Arctic Ocean, the Mediterranean Sea, the North Sea, the Baltic Sea, and the Celtic Sea.

Covering approximately 22% of Earth's surface, the Atlantic Ocean is second only to the Pacific Ocean 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 kilometres (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 kilometres (77,640,000 cu mi).

The average depths of the Atlantic, with its adjacent seas, is 3,339 meters (10,936 ft); without them it is 3,926 metres (12,881 ft). The greatest depth, 8,605 metres (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 Sierra Leone to over in the south.

Cultural significance

Transatlantic travel played a major role in the expansion of Western civilization into the Americas. Today, it is often called the Pond in idioms, in reference to the cultural link between North America and Europe.

Ocean bottom

The principal feature of the bathymetry (bottom topography) 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 kilometres (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 Blake, 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 metres (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 metres (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 metres (3,300 ft). The North Atlantic Deep Water reaches depths of as much as 4,000 metres (13,200 ft). The Antarctic Bottom Water occupies ocean basins at depths greater than 4,000 metres (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.


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 tendency 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 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 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 Atlantic Ocean appears to be the second youngest of all five oceans. Evidence indicates that 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 being rifted 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, most famously the Challenger expedition, but also including those by the German Meteor expedition, Columbia University's Lamont Geological Observatory, and the United States Navy Hydrographic Office.

Here are some important recent events in relation to the Atlantic:


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.


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, Bermuda, Canary Islands, Caribbean, Cape Verde, Sao Tome e Principe, Annobon Province, St. Peter (island), Fernando de Noronha, Rocas Atoll, Ascension Island, Saint Helena, The Islands of Trindad, Tristan da Cunha, Diego Alverez (Also known as 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. 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.

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 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.

Marine debris, also known as marine litter, is a term used to describe human-created waste that has found itself floating in a lake, sea, ocean or waterway. Oceanic debris tends to accumulate at the centre of gyres and coastlines, frequently washing aground where it is known as beach litter.

Major ports and harbours

See also


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