elongated, S-shaped basin extending in a north-south direction and is
COUNTERCURRENTS at about 8 deg north latitude. Bounded by North
and the Drake Passage on the south. An artificial connection between
the Atlantic and Pacific is also provided by the Panama Canal. On the
a line from Greenland to southernmost Spitsbergen to northern Norway.
Covering approximately 20% of the Earth’s surface, the Atlantic Ocean
is second only to the Pacific in size. The name is derived from Greek
mythology and means “Sea of Atlas.” With its adjacent seas it
occupies an area of about 106,450,000 sq km (41,100,000 sq mi);
without them, it has an area of 82,362,000 sq km (31,800,000 sq mi).
Pacific or Indian oceans. The volume of the Atlantic Ocean with its
adjacent seas is 354,700,000 km(3) (85,093,000 mi(3)) and without them 323,600,000 km(3) (77,632,000 mi(3).
The average depth of the Atlantic, with its adjacent seas, is 3,332 m (10,932 ft); without them it is 3,926 m (12,877 ft). The greatest
Liberia to about 4,830 km (3,000 mi) between the United States and northern Africa.
Norwegian-Greenland Sea, and Weddell Sea. Another characteristic feature is its relatively small number of islands. These include
Ridge. It extends from Iceland in the north to approximately 58 deg south latitude, reaching a maximum width of about 1,600 km
(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, forming 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 3,660 and 5,485 m
numerous basins. Some of the larger basins are the Guiana, North American, Cape Verde, and Canaries basins in the North Atlantic.
The deep ocean floor is thought to be fairly flat, although numerous SEAMOUNTS and some guyots exist. Several deeps or trenches
and reaches a depth of about 7,760 m (24,455 ft). The shelves along the margins of the continents constitute about 11% of the
bottom topography. In addition, a number of deep channels cut across the continental rise.
Ocean sediments are composed of terrigenous, pelagic, and authigenic material. Terrigenous deposits consist of sand, mud, and
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 m (200 ft) to 3,300 m (10,900 ft), they are thickest in the convergence belts
sedimentation proceeds slowly or where currents sort the deposits.
Although the minimum salinity values are found just north of the equator, 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 deg north latitude. Surface salinity
Surface water temperatures, which vary with latitude, current systems, and season and reflect the latitudinal distribution of solar
energy, range from less than 2 deg to 29 deg C (28 deg to 84 deg 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 deg to 8 deg C (12.6 deg to 14.4 deg 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 m (3,300 ft). The North Atlantic deep water reaches depths of as
much as 4,000 m (13,200 ft). The Antarctic bottom water occupies ocean basins at depths greater than 4,000 m (13,200 ft).
Water in the North Atlantic circulates in a clockwise direction, whereas water circulation in the South Atlantic is counterclockwise–a
lunar hours. The tides are a general wave that moves from south to north. In latitudes above 40 deg north some east-west oscillation
The climate of the Atlantic Ocean and adjacent land areas is influenced by the temperatures of the surface waters and water currents
moderate and free of extreme seasonal variations. 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
northwestern Europe, and the cold water currents contribute to heavy fog off the coast of northeastern Canada (the Grand Banks
area) and the northwestern coast of Africa. In general winds tend to transport moisture and warm or cool air over land areas.
Hurricanes develop in the southwestern North Atlantic Ocean.
HISTORY AND ECONOMY
The Atlantic Ocean appears to be the youngest of the world’s oceans. Evidence indicates that it did not exist prior to 100 million
the process of SEAFLOOR SPREADING. The Atlantic has been extensively explored since the earliest settlements were
including those by the German Meteor expedition, Columbia University’s Lamont Geological Observatory, and the U.S. Navy
cod, haddock, hake, herring, and mackerel. The most productive areas include the GRAND BANKS off Newfoundland, the shelf area
the North Sea, and the Falkland Banks. Eel, lobster, and whales are also taken in great quantities. All these factors, taken together,
Harvey, J. G., The Ocean and Atmosphere: Our Fluid Environment (1976); Huxley, Anthony, ed., Standard Encyclopedia of the
World’s Oceans and Islands (1962); Klenova, M. V., ed., Oceanographic Research in the Atlantic (1967