Atlantic Ocean

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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 but for physical purposes the division is moved slightly counter-clockwise to a line roughly from the Bolama region, Guinea-Bissau to Rio Grande do Norte state, Brazil to include the Gulf of Guinea with the South and the north coast of South America with the North.

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 at the 60° parallel 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 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

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.

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 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.

,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 6,400 km (4,000 mi) in the south.

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 the 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, Great Britain (including numerous surrounding islands), Ireland, 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, Gough Island (Also known as Diego Alvarez), Falkland Islands, Tierra del Fuego, South Georgia Island, South Sandwich Islands, and Bouvet Island.