| Health / Medical Topics |
Atlantic Ocean
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 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.
Geography
The Atlantic Ocean is bounded on the west by North and South America. 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 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. Some authorities show it extending south to Antarctica, while others show it bounded at the 60° parallel by the Southern Ocean. In the southwest, the Drake Passage connects it to the Pacific Ocean. The man-made Panama Canal links the Atlantic and Pacific. 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 is second in size to the Pacific. With its adjacent seas it occupies an area of about 106400000 square kilometres (41081040 sq mi); without them, it has an area of 82400000 square kilometres (31814640 sq mi). 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 3339 metres (10955 ft); without them it is 3926 metres (12881 ft). The greatest depth, 8605 metres (28232 ft), is in the Puerto Rico Trench. The Atlantic's width varies from 2848 kilometres (1770 mi) between Brazil and Sierra Leone to over 6400 km (3977 mi) 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
The principal feature of the bathymetry (bottom topography) 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 1600 kilometres (994 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 2700 metres (8858 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 from 3700-5500 metres (12139-18045 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 at 8605 metres (28232 ft). The Laurentian Abyss is found off the eastern coast of Canada. In the South Atlantic, the South Sandwich Trench reaches a depth of 8428 metres (27651 ft). A third major trench, the Romanche Trench, is located near the equator and reaches a depth of about 7454 metres (24455 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 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 60-3300 metres (197-10827 ft) 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
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 −2 °C (32 °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 7-8 °C (45-46 °F).
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 1000 metres (3281 ft). The North Atlantic Deep Water reaches depths of as much as 4000 metres (13123 ft). The Antarctic Bottom Water occupies ocean basins at depths greater than 4,000 meters.
Within the North Atlantic, ocean currents isolate the Sargasso Sea, 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
History
Notable crossings
In 1000, the Icelander, Leif Ericson was the first European to discover North America's Atlantic coast, including Vinland. The Norse discovery was documented in the 13th century Icelandic Sagas and was corroborated by recent archeological evidence.
In 1003, Thorfinnr Karlsefni led an attempted Viking settlement in North America but was driven off by the natives.
In 1004, Snorri Thorfinnsson was the first European born on the American continent.
In 1419 and 1427, Portuguese navigators reached Madeira and Azores, respectively.
From 1415 to 1488, Portuguese navigators sailed along the Western African coast, reaching the Cape of Good Hope.
In 1492, Christopher Columbus landed somewhere in The Bahamas.
From 1499 to 1502, Amerigo Vespucci mapped South America's east coast, proving that the Americas are not Asia's east edge.
In 1500, Pedro Álvares Cabral reached Brazil.
Between 1512 to 1530, Saint Brendan possible journeyed across the Atlantic, but his intentions remain disputable.
In 1524, Italian explorer Giovanni da Verrazzano discovered the United States of America east coast.
In 1764 William Harrison (the son of John Harrison) sailed aboard the HMS Tartar, with the H-4 time piece. The voyage became the basis for the invention of the global system of Longitude.
In 1858, Cyrus West Field laid the first transatlantic telegraph cable (it quickly failed).
In 1865 Brunel's ship the SS Great Eastern laid the first successful transatlantic telegraph cable .
On April 15, 1912 the RMS Titanic sank after hitting an iceberg with a loss of more than 1,500 lives.
1914-1918, the First Battle of the Atlantic took place.
In 1919, the American NC-4 became the first fixed-wing aircraft (seaplane) to cross the Atlantic (though it made a couple of landings on islands and the sea along the way, and taxied several hundred miles).
Later in 1919, a British aeroplane piloted by Alcock and Brown made the first non-stop transatlantic flight, from Newfoundland to Ireland.
In 1921, the British were the first to cross the North Atlantic in an airship.
In 1922, Sacadura Cabral and Gago Coutinho were the first to cross the South Atlantic in an airship.
The first transatlantic telephone call was made on January 7, 1927.
In 1927, Charles Lindbergh made the first solo non-stop transatlantic flight in an aircraft (between New York City and Paris).
In 1932, Amelia Earhart became the first female to make a solo flight across the Atlantic
1939-1945, the Second Battle of the Atlantic. Nearly 3,700 Allied ships were sunk at a cost of 783 German U-boats.
In 1952, Ann Davison was the first woman to single-handedly sail the Atlantic Ocean.
In 1980, Gérard d'Aboville was the first man to cross the Atlantic Ocean rowing.
In 1994, Guy Delage was the first man to swim across the Atlantic Ocean (with the help of a kick board, from Cape Verde to Barbados.)
In 1998, Benoît Lecomte was the first man to swim across the northern Atlantic Ocean without a kick board, stopping for only one week in the Azores.
In 1999, after rowing for 81 days and 4,767 kilometres (2,962 mi), Tori Murden became the first woman to cross the Atlantic Ocean by rowboat alone when she reached Guadeloupe from the Canary Islands.
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, Brazil and Monrovia, Liberia. 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 was 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 Newfoundland's Grand Banks, the Nova Scotia shelf , 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 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 Sea, Denmark Strait, and Baltic Sea. 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 Sea, Baltic Sea, North Sea, Labrador Sea, Black Sea, Gulf of Saint Lawrence, Bay of Fundy, Gulf of Maine, Mediterranean Sea, Gulf of Mexico, and Caribbean Sea.
Islands include Greenland, Iceland, Faroe Islands, Great Britain (including numerous surrounding islands), Ireland, Rockall, Newfoundland, Sable Island, Azores, Madeira, Bermuda, Canary Islands, Caribbean, Cape Verde, São Tomé and Príncipe, Annobón 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.
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
Icebergs are common from February to August in the Davis Strait, Denmark Strait, and the northwestern Atlantic and have been spotted as far south as Bermuda and Madeira. 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.
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 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 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.
YOU MAY ALSO LIKE
