Neptune's Needle

Second largest of the earth's four oceans ( c.36,000,000 sq miles with marginal seas), extending in an S shape from the arctic to the Antarctic regions between North America and South America on the W and Europe and Africa on the East. Flows from between c.70º00'N and c.60º00'S, about 7800 miles long. Its width varies from at its narrowest, 1800 miles, between the respective outcroppings of Africa and South America, to its widest at the bottom, about 4200 miles separating the Cape of Good Hope and Cape Horn.

Relationship to Other Bodies of Water

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 (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 are (in the W) Hudson and Baffin bays, the Gulf of Mexico, and the Caribbean Sea; (in the E) the Baltic, North, Mediterranean, and Black seas; and (in the S) Weddell Sea.

Islands

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, Shetland Islands, Falkland Islands, Canary Islands, and Newfoundland Island, Iceland, the Azores, the Cape Verde Islands, Ascension, the South Sandwich Islands. The West Indies and Bermuda are volcanic islands created by processes related to the Mid-Atlantic Ridge. The Bahamas are low coral islands that sit on the Blake Plateau, while the Madeiras are high volcanic islands.

Depth

The floor of the Atlantic has an average depth of c.12,000 ft/3,658 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 here. 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 greatest depth (c.28,000 ft/8,530 m) is the Milwaukee Deep, in the Puerto Rico Trench, N of Puerto Rico.

Waters That Flow Into the Ocean

More large rivers, including the Mississippi, the Congo, and the Amazon, drain into the Atlantic than into any other ocean. The surface waters in the Atlantic’s trade wind belts attain the highest salinity known in ocean water.

Basins and Currents

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 (Gulf Stream and the North Equatorial, Antilles, North Atlantic, and Canary currents) and the counterclockwise-moving currents of the South Atlantic (West Wind Drift and the South Equatorial, Brazil, and Benguela currents) are separated from each other by the Equatorial Countercurrent.

Economic Activity

At the Grand Banks off Newfoundland, heavy fogs form along the front where the warm Gulf Stream meets the cold Labrador Current. The Grand Banks, along with the Dogger Bank of the North Sea, contain some of the world’s best commercial fishing grounds. The North Atlantic Ocean has some of the world’s busiest shipping lanes; the N lanes are patrolled for icebergs.

Exploration

Commerce between the Mediterranean Sea and the NE Atlantic Ocean was initiated by the Carthaginians. From the 7th century 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 century and to the Western Hemisphere by Spain after the voyages of Columbus. Scientific knowledge of the ocean floor dates from the Challenger expedition (1872-1876) and has greatly expanded since the 1960s.

Sources

Compiler

Peter Richards