What is the Atlantic Ocean like? Atlantic Ocean: characteristics according to plan

The Atlantic Ocean is the second largest ocean on Earth after the Pacific Ocean, located between Greenland and Iceland in the north, Europe and Africa in the east, North and South America in the west, and Antarctica in the south.

The area is 91.6 million km², of which about a quarter is inland seas. The area of ​​coastal seas is small and does not exceed 1% of the total water area. The volume of water is 329.7 million km³, which is equal to 25% of the volume of the World Ocean. The average depth is 3736 m, the greatest is 8742 m (Puerto Rico Trench). The average annual salinity of ocean waters is about 35 ‰. The Atlantic Ocean has a highly indented coastline with a pronounced division into regional waters: seas and bays.

The name comes from the name of the Titan Atlas (Atlas) in Greek mythology.

Characteristics:

• Area - 91.66 million km²
• Volume - 329.66 million km³
• Greatest depth - 8742 m
• Average depth - 3736 m

Etymology

The name of the ocean first appears in the 5th century BC. e. in the works of the ancient Greek historian Herodotus, who wrote that “the sea with the pillars of Hercules is called Atlantis (ancient Greek Ἀτλαντίς - Atlantis).” The name comes from the myth known in Ancient Greece about Atlas, the Titan holding the firmament on his shoulders at the westernmost point of the Mediterranean. The Roman scientist Pliny the Elder in the 1st century used the modern name Oceanus Atlanticus (lat. Oceanus Atlanticus) - “Atlantic Ocean”. At different times, individual parts of the ocean were called the Western Ocean, the North Sea, and the Outer Sea. Since the middle of the 17th century, the only name referring to the entire water area was the Atlantic Ocean.

Physiographic characteristics

General information

The Atlantic Ocean is the second largest. Its area is 91.66 million km², the volume of water is 329.66 million km³. It extends from subarctic latitudes all the way to Antarctica. The border with the Indian Ocean runs along the meridian of Cape Agulhas (20° E) to the coast of Antarctica (Donning Maud Land). The border with the Pacific Ocean is drawn from Cape Horn along the meridian 68°04’W. or along the shortest distance from South America to the Antarctic Peninsula through the Drake Passage, from Oste Island to Cape Sterneck. The border with the Arctic Ocean runs along the eastern entrance of the Hudson Strait, then through Davis Strait and along the coast of Greenland to Cape Brewster, through the Denmark Strait to Cape Reydinupur on the island of Iceland, along its coast to Cape Gerpir, then to the Faroe Islands, then to Shetland islands and along 61° north latitude to the coast of the Scandinavian Peninsula. Sometimes the southern part of the ocean, with the northern border from 35° south. w. (based on the circulation of water and atmosphere) up to 60° south. w. (by the nature of the bottom topography) are classified as the Southern Ocean, which is not officially distinguished.

Seas and bays

The area of ​​the seas, bays and straits of the Atlantic Ocean is 14.69 million km² (16% of the total ocean area), the volume is 29.47 million km³ (8.9%). Seas and main bays (clockwise): Irish Sea, Bristol Bay, North Sea, Baltic Sea (Gulf of Bothnia, Gulf of Finland, Gulf of Riga), Bay of Biscay, Mediterranean Sea (Alboran Sea, Balearic Sea, Ligurian Sea, Tyrrhenian Sea, Adriatic Sea, Ionian Sea, Aegean Sea), Marmara Sea, Black Sea, Azov Sea, Gulf of Guinea, Riiser-Larsen Sea, Lazarev Sea, Weddell Sea, Scotia Sea (the last four are sometimes referred to as the Southern Ocean), Caribbean Sea, Gulf of Mexico , Sargasso Sea, Gulf of Maine, Gulf of St. Lawrence, Labrador Sea.

Islands

The largest islands and archipelagos of the Atlantic Ocean: British Isles (Great Britain, Ireland, Hebrides, Orkney, Shetland), Greater Antilles (Cuba, Haiti, Jamaica, Puerto Rico, Juventud), Newfoundland, Iceland, Tierra del Fuego archipelago (Terra del Fuego Land, Oste, Navarino), Maragio, Sicily, Sardinia, Lesser Antilles (Trinidad, Guadeloupe, Martinique, Curacao, Barbados, Grenada, St. Vincent, Tobago), Falkland Islands (Malvinas) (East Falkland (Soledad), West Falkland (Gran Malvina)), Bahamas (Andros, Grand Inagua, Grand Bahama), Cape Breton, Cyprus, Corsica, Crete, Anticosti, Canary Islands (Tenerife, Fuerteventura, Gran Canaria), Zealand, Prince Edward, Balearic Islands (Mallorca), South Georgia, Long Island, Moonsund Archipelago (Saaremaa, Hiiumaa), Cape Verde Islands, Euboea, Southern Sporades (Rhodes), Gotland, Funen, Cyclades Islands, Azores, Ionian Islands, South Shetland Islands, Bioko, Bijagos Islands, Lesbos, Åland Islands, Faroe Islands, Öland, Lolland, South Orkney Islands, Sao Tome, Madeira Islands, Malta, Principe, Saint Helena, Ascension, Bermuda.

History of ocean formation

The Atlantic Ocean was formed in the Mesozoic as a result of the split of the ancient supercontinent Pangea into the southern continent of Gondwana and northern Laurasia. As a result of the multidirectional movement of these continents at the very end of the Triassic, it led to the formation of the first oceanic lithosphere of the present North Atlantic. The resulting rift zone was a western extension of the Tethys Ocean rift. The Atlantic Trench, at an early stage of its development, was formed as a connection of two large ocean basins: the Tethys Ocean in the east and the Pacific Ocean in the west. Further expansion of the Atlantic Ocean depression will occur due to the reduction in the size of the Pacific Ocean. In Early Jurassic times, Gondwana began to split into Africa and South America and the oceanic lithosphere of the modern South Atlantic was formed. During the Cretaceous, Laurasia split, and the separation of North America from Europe began. At the same time, Greenland, moving to the north, broke away from Scandinavia and Canada. Over the past 40 million years and up to the present, the opening of the Atlantic Ocean basin has continued along a single rift axis located approximately in the middle of the ocean. Today, the movement of tectonic plates continues. In the South Atlantic, the African and South American plates continue to diverge at a rate of 2.9-4 cm per year. In the Central Atlantic, the African, South American and North American plates are diverging at a rate of 2.6-2.9 cm per year. In the North Atlantic, the spread of the Eurasian and North American plates continues at a rate of 1.7-2.3 cm per year. The North American and South American plates move to the west, the African plate to the northeast, and the Eurasian plate to the southeast, forming a compression belt in the Mediterranean Sea region.

Geological structure and bottom topography

Underwater continental margins

Significant areas of the shelf are confined to the northern hemisphere and are adjacent to the coasts of North America and Europe. In Quaternary times, most of the shelf was subject to continental glaciation, which formed relict glacial landforms. Another element of the relict relief of the shelf is flooded river valleys, found in almost all shelf areas of the Atlantic Ocean. Relict continental deposits are widespread. Off the coasts of Africa and South America, the shelf occupies smaller areas, but in the southern part of South America it expands significantly (Patagonian shelf). Tidal currents formed sand ridges, which are the most widespread of modern subaquatic landforms. They are very characteristic of the shelf North Sea, found in large numbers in the English Channel, as well as on the shelves of North and South America. In equatorial-tropical waters (especially in the Caribbean Sea, on the Bahamas, off the coast of South America), coral reefs are diverse and widely represented.

Continental slopes in most areas of the Atlantic Ocean are characterized by steep slopes, sometimes with a stepped profile, and are deeply dissected by submarine canyons. In some areas, the continental slopes are supplemented by marginal plateaus: Blake, Sao Paulo, Falkland on the American submarine margins; Podkupain and Goban on the underwater edge of Europe. The blocky structure is the Farrero-Icelandic Threshold, which extends from Iceland to the North Sea. In the same region is the Rokkol Rise, which is also a submerged part of the underwater part of the European subcontinent.

The continental foot, over most of its length, is an accumulation plain lying at a depth of 3-4 km and composed of a thick (several kilometers) layer of bottom sediments. Three rivers of the Atlantic Ocean are among the ten largest in the world - the Mississippi (solid flow 500 million tons per year), the Amazon (499 million tons) and the Orange (153 million tons). The total volume of sedimentary material carried annually into the Atlantic Ocean basin by only 22 of its main rivers is more than 1.8 billion tons. In certain areas of the continental foot there are large fans of turbidity currents, among them the most significant fans of the underwater canyons of the Hudson, Amazon, and Rhone (in the Mediterranean), Niger, Congo. Along the North American continental margin, due to the bottom runoff of cold Arctic waters along the continental foot in the southern direction, giant accumulative landforms are formed (for example, the “sedimentary ridges” of Newfoundland, Blake-Bahama and others).

Transition zone

Transition zones in the Atlantic Ocean are represented by the Caribbean, Mediterranean, and Scotia or South Sandwich Sea regions.

The Caribbean region includes: the Caribbean Sea, the deep-sea Gulf of Mexico, island arcs and deep-sea trenches. The following island arcs can be distinguished in it: Cuban, Cayman-Sierra Maestra, Jamaica-South Haiti, and the outer and inner arcs of the Lesser Antilles. In addition, the underwater rise of Nicaragua, the Beata and Aves ridges are distinguished here. The Cuban arc has a complex structure and is Laramian age of folding. Its continuation is the northern cordillera of the island of Haiti. The Cayman Sierra Maestra fold structure, which is of Miocene age, begins with the Mayan Mountains in the Yucatan Peninsula, then continues as the Cayman submarine ridge and the Southern Cuba Sierra Maestra mountain range. The Lesser Antilles arc includes a number of volcanic formations (including three volcanoes, such as Montagne Pelee). Composition of eruption products: andesites, basalts, dacites. The outer ridge of the arc is limestone. From the south, the Caribbean Sea is bordered by two parallel young ridges: the arc of the Leeward Islands and the Caribbean Andes mountain range, passing to the east into the islands of Trinidad and Tobago. Island arcs and submarine ridges divide the floor of the Caribbean Sea into several basins, which are lined by a thick layer of carbonate sediments. The deepest of them is Venezuela (5420 m). There are also two deep-sea trenches - Cayman and Puerto Rico (with the greatest depth of the Atlantic Ocean - 8742 m).

The areas of the Scotia Ridge and the South Sandwich Islands are borderlands - areas of the underwater continental margin, fragmented by tectonic movements of the earth's crust. The island arc of the South Sandwich Islands is complicated by a number of volcanoes. Adjacent to it from the east is the South Sandwich deep-sea trench with a maximum depth of 8228 m. The mountainous and hilly topography of the bottom of the Scotia Sea is associated with the axial zone of one of the branches of the mid-ocean ridge.

In the Mediterranean Sea there is a wide distribution of continental crust. The suboceanic crust is developed only in patches in the deepest basins: Balearic, Tyrrhenian, Central and Cretan. The shelf is significantly developed only within the Adriatic Sea and the Sicilian threshold. The mountainous folded structure connecting the Ionian Islands, Crete and the islands to the east of the latter represents an island arc, which is bounded on the south by the Hellenic Trench, in turn on the south, framed by the uplift of the East Mediterranean Wall. The bottom of the Mediterranean Sea in the geological section is composed of salt-bearing strata of the Messinian stage (Upper Miocene). The Mediterranean Sea is a seismic zone. Several active volcanoes remain here (Vesuvius, Etna, Santorini).

Mid-Atlantic Ridge

The meridional Mid-Atlantic Ridge divides the Atlantic Ocean into eastern and western parts. It begins off the coast of Iceland under the name of the Reykjanes Ridge. Its axial structure is formed by a basalt ridge; rift valleys are poorly expressed in the relief, but active volcanoes are known on the flanks. At latitude 52-53° N. The mid-ocean ridge is crossed by the transverse zones of the Gibbs and Reykjanes faults. Behind them begins the Mid-Atlantic Ridge with a clearly defined rift zone and rift valleys with numerous transverse faults and deep grabens. At latitude 40° N. The mid-ocean ridge forms the Azores volcanic plateau, with numerous surface (forming islands) and underwater active volcanoes. To the south of the Azores Plateau, in the rift zone, basalts lie under calcareous silts 300 m thick, and under them a blocky mixture of ultramafic and mafic rocks. The area is currently experiencing vigorous volcanic and hydrothermal activity. In the equatorial part, the North Atlantic Ridge is divided by a large number of transverse faults into a number of segments experiencing significant (up to 300 km) lateral displacements relative to each other. Near the equator, the Romanche depression with depths of up to 7856 m is associated with deep-sea faults.

The South Atlantic Ridge has a meridional strike. Rift valleys are well defined here, the number of transverse faults is fewer, so this ridge looks more monolithic compared to the North Atlantic Ridge. In the southern and middle parts of the ridge there are the volcanic plateaus of the Ascension, the islands of Tristan da Cunha, Gough, and Bouvet. The plateau is confined to active and recently active volcanoes. From Bouvet Island, the South Atlantic Ridge turns east, circles Africa and, in the Indian Ocean, meets the West Indian Mid-Range.

ocean bed

The Mid-Atlantic Ridge divides the floor of the Atlantic Ocean into two almost equal parts. In the western part, mountain structures: the Newfoundland Ridge, the Baracuda Ridge, the Ceara and Rio Grande uplifts divide the ocean floor into basins: Labrador, Newfoundland, North American, Guiana, Brazil, Argentina. To the east of the mid-ocean ridge, the bed is divided by the underwater base of the Canary Islands, the Cape Verde Islands, the Guinea Rise and the Whale Ridge into basins: Western European, Iberian, North African, Cape Verde, Sierra Leone, Guinea, Angolan, Cape. In the basins, flat abyssal plains are widespread, composed mainly of calcareous biogenic as well as terrigenous material. Over most of the ocean floor area, the sediment thickness is more than 1 km. Under the sedimentary rocks a layer was discovered consisting of volcanic rocks and compacted sedimentary rocks.

In areas of basins remote from the underwater margins of continents, abyssal hills are common along the periphery of mid-ocean ridges. About 600 mountains are located within the ocean floor. A large group of seamounts is confined to the Bermuda Plateau (in the North American Basin). There are several large submarine valleys, of which the most significant are the Hazen and Maury valleys in the northern part of the Atlantic Ocean, stretching on either side of the Mid-Ocean Ridge.

Bottom sediments

The sediments of the shallow part of the Atlantic Ocean are mostly represented by terrigenous and biogenic sediments, and occupy 20% of the area of ​​the ocean floor. Of the deep-sea sediments, the most common are calcareous foraminiferal silts (65% of the ocean floor area). In the Mediterranean and Caribbean Seas, in the southern zone of the South Atlantic Ridge, pteropod deposits became widespread. Deep-sea red clay occupies about 20% of the ocean floor and is confined to the deepest parts of ocean basins. In the Angola Basin, radilarium oozes are found. In the southern part of the Atlantic there are siliceous diatom deposits with authigenic silica content of 62-72%. In the zone of the Western Wind Current there is a continuous field of diatomaceous oozes, with the exception of the Drake Passage. In some basins of the ocean floor, terrigenous silts and pelites are significantly developed. Terrigenous deposits at abyssal depths are characteristic of the North Atlantic, Hawaiian, and Argentine basins.

Climate

The variety of climatic conditions on the surface of the Atlantic Ocean is determined by its large meridional extent and the circulation of air masses under the influence of four main atmospheric centers: the Greenland and Antarctic highs, the Icelandic and Antarctic lows. In addition, two anticyclones are constantly active in the subtropics: the Azores and the South Atlantic. They are separated by an equatorial region of low pressure. This distribution of pressure regions determines the system of prevailing winds in the Atlantic. The greatest influence on the temperature regime of the Atlantic Ocean is exerted not only by its large meridional extent, but also by water exchange with the Arctic Ocean, the Antarctic seas and the Mediterranean Sea. Surface waters are characterized by their gradual cooling as they move away from the equator to high latitudes, although the presence of powerful currents causes significant deviations from zonal temperature regimes.

In the vastness of the Atlantic, all climatic zones of the planet are represented. Tropical latitudes are characterized by slight seasonal temperature fluctuations (average 20 °C) and heavy precipitation. To the north and south of the tropics there are subtropical zones with more noticeable seasonal (from 10 °C in winter to 20 °C in summer) and daily temperature fluctuations; Precipitation here falls mainly in summer. Tropical hurricanes are a frequent occurrence in the subtropical zone. In these monstrous atmospheric vortices, wind speeds reach several hundred kilometers per hour. The most powerful tropical hurricanes rage in the Caribbean: for example, in the Gulf of Mexico and the West Indies. West Indian tropical hurricanes form in the western part of the ocean in the region of 10-15° N latitude. and move to the Azores and Ireland. Further to the north and south follow the subtropical zones, where in the coldest month the temperature drops to 10 °C, and in winter cold air masses from polar low pressure areas bring heavy precipitation. In temperate latitudes, the average temperature of the warmest month is between 10-15 °C, and the coldest month is −10 °C. There are also significant daily temperature changes here. The temperate zone is characterized by fairly uniform precipitation throughout the year (about 1,000 mm), reaching a maximum in the autumn-winter period, and frequent fierce storms, for which the southern temperate latitudes are nicknamed the “Roaring Forties.” The 10 °C isotherm defines the boundaries of the Northern and Southern polar zones. In the Northern Hemisphere, this boundary runs in a wide band between 50° N latitude. (Labrador) and 70°N. (coast of Northern Norway). In the Southern Hemisphere, the circumpolar zone begins closer to the equator - approximately 45-50° S. The lowest temperature (-34 °C) was recorded in the Weddell Sea.

Hydrological regime

Surface water circulation

Powerful carriers of thermal energy are circular surface currents located on both sides of the equator: such, for example, are the North Trade Wind and South Trade Wind currents, crossing the ocean from east to west. The Northern Trade Wind Current near the Lesser Antilles is divided: into a northern branch, continuing northwest along the coast of the Greater Antilles (Antilles Current) and into a southern branch, leaving through the straits of the Lesser Antilles into the Caribbean Sea, and then flowing through the Yucatan Strait into the Gulf of Mexico, and leaves it through the Strait of Florida, forming the Florida Current. The latter has a speed of 10 km/h and gives rise to the famous Gulf Stream. The Gulf Stream, following along the American coast, at 40°N. as a result of the influence of westerly winds and the Coriolis force, it acquires an eastern and then a northeastern direction and is called the North Atlantic Current. The main flow of water from the North Atlantic Current passes between Iceland and the Scandinavian Peninsula and flows into the Arctic Ocean, softening the climate in the European sector of the Arctic. Two powerful streams of cold, desalinated water flow from the Arctic Ocean - the East Greenland Current, which runs along the eastern coast of Greenland, and the Labrador Current, which goes around Labrador, Newfoundland and penetrates south to Cape Hatteras, pushing the Gulf Stream away from the coast of North America.

The Southern Trade Wind Current partially enters the northern hemisphere, and at Cape San Roque it divides into two parts: one of them goes to the south, forming the Brazil Current, the other turns to the north, forming the Guiana Current, which goes into the Caribbean Sea. The Brazilian Current in the La Plata region meets the cold Falkland Current (a branch of the West Wind Current). Near the southern end of Africa, the cold Benguela Current branches off from the West Wind Current and, moving along the coast of South-West Africa, gradually deviates to the west. In the southern part of the Gulf of Guinea, this current closes the anticyclonic circulation of the Southern Trade Wind Current.

There are several tiers of deep-sea currents in the Atlantic Ocean. A powerful countercurrent passes under the Gulf Stream, the main core of which lies at a depth of up to 3500 m, with a speed of 20 cm/s. The countercurrent flows as a narrow stream in the lower part of the continental slope; the formation of this current is associated with the bottom runoff of cold waters from the Norwegian and Greenland seas. The subsurface Lomonosov Current has been discovered in the equatorial zone of the ocean. It starts from the Antilo-Guiana countercurrent and reaches the Gulf of Guinea. The powerful deep Louisiana Current is observed in the eastern part of the Atlantic Ocean, formed by the bottom runoff of saltier and warmer Mediterranean waters through the Strait of Gibraltar.

The highest tide values ​​are confined to the Atlantic Ocean, which are observed in the fiord bays of Canada (in Ungava Bay - 12.4 m, in Frobisher Bay - 16.6 m) and Great Britain (up to 14.4 m in Bristol Bay). The highest tide in the world is recorded in the Bay of Fundy, on the east coast of Canada, where the maximum tide reaches 15.6-18 m.

Temperature, salinity, ice formation

Temperature fluctuations in Atlantic waters throughout the year are not large: in the equatorial-tropical zone - no more than 1-3°, in the subtropics and temperate latitudes - within 5-8°, in subpolar latitudes - about 4° in the north and no more than 1° on South. The warmest waters are in equatorial and tropical latitudes. For example, in the Gulf of Guinea the temperature in the surface layer does not drop below 26 °C. In the northern hemisphere, north of the tropics, the temperature of the surface layer decreases (at 60°N it is 10°C in summer). In the southern hemisphere, temperatures increase much faster and at 60°S. fluctuate around 0 °C. In general, the ocean in the southern hemisphere is colder than in the northern hemisphere. In the northern hemisphere, the western part of the ocean is colder than the eastern, in the southern hemisphere it is vice versa.

The highest salinity of surface waters in the open ocean is observed in the subtropical zone (up to 37.25 ‰), and the maximum in the Mediterranean Sea is 39 ‰. In the equatorial zone, where the maximum amount of precipitation is recorded, salinity decreases to 34 ‰. A sharp desalination of water occurs in the estuary areas (for example, at the mouth of La Plata 18-19 ‰).

Ice formation in the Atlantic Ocean occurs in the Greenland and Baffin seas and Antarctic waters. The main source of icebergs in the South Atlantic is the Filchner Ice Shelf in the Weddell Sea. On the Greenland coast, icebergs are produced by outlet glaciers, such as the Jakobshavn glacier in the area of ​​Disko Island. Floating ice in the northern hemisphere reaches 40°N in July. In the southern hemisphere, floating ice is present throughout the year up to 55°S, reaching its maximum extent in September-October. The total removal from the Arctic Ocean is estimated at an average of 900,000 km³/year, and from the surface of Antarctica - 1630 km³/year.

Water masses

Under the influence of wind and convective processes, vertical mixing of water in the Atlantic Ocean occurs, covering a surface thickness of 100 m in the southern hemisphere and up to 300 m in the tropics and equatorial latitudes. Below the layer of surface waters, outside the subantarctic zone, in the Atlantic there is the Antarctic intermediate water, which is almost universally identified with the intermediate minimum of salinity and is characterized by a higher content of nutrients in relation to the overlying waters, and extends north to the region of 20° N. at depths of 0.7-1.2 km.

A feature of the hydrological structure of the eastern part of the North Atlantic is the presence of an intermediate Mediterranean water mass, which gradually descends to a depth of 1000 to 1250 m, turning into a deep water mass. In the southern hemisphere, this water mass drops to levels of 2500-2750 m and wedges south of 45°S. The main feature of these waters is their high salinity and temperature relative to the surrounding waters. In the bottom layer of the Strait of Gibraltar, a salinity of up to 38 ‰ and a temperature of up to 14 °C are noted, but already in the Gulf of Cadiz, where Mediterranean waters reach the depths of their existence in the Atlantic Ocean, their salinity and temperature as a result of mixing with background waters drop to 36 ‰ and 12-13°C respectively. At the periphery of the distribution area, its salinity and temperature are, respectively, 35 ‰ and about 5°C. Under the Mediterranean water mass in the northern hemisphere, North Atlantic deep water is formed, which descends as a result of winter cooling of relatively salty waters in the North European Basin and the Labrador Sea to a depth of 2500-3000 m in the northern hemisphere and to 3500-4000 m in the southern hemisphere, reaching to approximately 50°S. The North Atlantic deep water differs from the overlying and underlying Antarctic waters in its increased salinity, temperature and oxygen content, as well as a reduced content of nutrients.

The Antarctic bottom water mass is formed on the Antarctic slope as a result of the mixing of cold and heavy Antarctic shelf water with lighter, warmer and more saline Circumpolar deep waters. These waters, spreading from the Weddell Sea, passing through all orographic obstacles up to 40°N, have a temperature of less than minus 0.8ºC in the north of this sea, 0.6ºC at the equator and 1.8ºC near the Bermuda Islands. The Arctic bottom water mass has lower salinity values ​​compared to the overlying waters and in the South Atlantic is characterized by an increased content of nutrients.

Flora and fauna

The bottom flora of the northern part of the Atlantic is represented by brown (mainly fucoids, and in the sublittoral zone - kelp and alaria) and red algae. In the tropical zone, green algae (caulerpa), red algae (calcareous lithothamnia) and brown algae (sargassum) predominate. In the southern hemisphere, bottom vegetation is mainly represented by kelp forests. There are 245 species of phytoplankton in the Atlantic Ocean: peridinea, coccolithophores, and diatoms. The latter have a clearly defined zonal distribution; their maximum number lives in the temperate latitudes of the northern and southern hemispheres. The population of diatoms is most dense in the zone of the Western Wind Current.

The distribution of the fauna of the Atlantic Ocean has a pronounced zonal character. In subantarctic and Antarctic waters, notothenia, whiting and others are of commercial importance. Benthos and plankton in the Atlantic are poor in both species and biomass. In the subantarctic zone and in the adjacent temperate zone, biomass reaches its maximum. The zooplankton is dominated by copepods and pteropods; the nekton is dominated by mammals such as whales (blue whale), pinnipeds, and their fish - nototheniids. In the tropical zone, zooplankton is represented by numerous species of foraminifera and pteropods, several species of radiolarians, copepods, larvae of mollusks and fish, as well as siphonophores, various jellyfish, large cephalopods (squid), and, among benthic forms, octopuses. Commercial fish are represented by mackerel, tuna, sardines, and in areas of cold currents - anchovies. Corals are confined to tropical and subtropical zones. The temperate latitudes of the northern hemisphere are characterized by abundant life with a relatively small diversity of species. Of the commercial fish, the most important are herring, cod, haddock, halibut, and sea bass. Foraminifera and copepods are the most characteristic of zooplankton. The greatest abundance of plankton is in the area of ​​the Newfoundland Bank and the Norwegian Sea. The deep-sea fauna is represented by crustaceans, echinoderms, specific species of fish, sponges, and hydroids. Several species of endemic polychaetes, isopods, and holothurians have been found in the Puerto Rico Trench.

Ecological problems

Since time immemorial, the Atlantic Ocean has been a place of intense marine fishing and hunting. The sharp increase in capacity and the revolution in fishing technology have led to alarming proportions. With the invention of the harpoon cannon, whales were largely exterminated in the North Atlantic at the end of the 19th century. Due to the massive development of pelagic whaling in Antarctic waters in the mid-20th century, whales here were also close to complete extermination. Since the 1985-1986 season, the International Whale Commission has imposed a complete moratorium on commercial whaling of any species. In June 2010, at the 62nd meeting of the International Whaling Commission, under pressure from Japan, Iceland and Denmark, the moratorium was suspended.

The explosion on the Deepwater Horizon oil platform, owned by the British company BP, which occurred on April 20, 2010, is considered the largest environmental disaster that has ever occurred at sea. The accident spilled about 5 million barrels of crude oil into the Gulf of Mexico and polluted 1,100 miles of coastline. The authorities have introduced a fishing ban; more than a third of the entire water area of ​​the Gulf of Mexico is closed to fishing. As of November 2, 2010, 6,814 dead animals had been collected, including 6,104 birds, 609 sea turtles, 100 dolphins and other mammals, and 1 other reptile. According to the Office of Specially Protected Resources of the National Oceanic and Atmospheric Administration, in 2010-2011, the mortality rate of cetaceans in the northern Gulf of Mexico increased several times compared to previous years (2002-2009).

A large garbage patch of plastic and other waste has formed in the Sargasso Sea, formed by ocean currents that gradually concentrate trash thrown into the ocean in one area.

There is radioactive contamination in some areas of the Atlantic Ocean. Waste from nuclear power plants and research centers is discharged into rivers and coastal seas, and sometimes into the deep ocean. Areas of the Atlantic Ocean heavily contaminated with radioactive waste include the North, Irish, Mediterranean Seas, the Bay of Mexico, the Bay of Biscay and the Atlantic coast of the United States. In 1977 alone, 7,180 containers containing 5,650 tons of radioactive waste were dumped into the Atlantic. The U.S. Environmental Protection Agency reported contamination of the seabed 120 miles east of the Maryland-Delaware border. There, 14,300 cemented containers containing plutonium and cesium were buried there for 30 years; radioactive contamination exceeded “expected” by 3-70 times. In 1970, the United States sank the Russell Brigge, 500 km off the coast of Florida, carrying 68 tons of nerve gas (sarin) placed in 418 concrete containers. In 1972, in the ocean waters north of the Azores, Germany sank 2,500 metal barrels containing industrial waste containing potent cyanide poisons. There are cases of rapid destruction of containers in the relatively shallow waters of the North and Irish Seas and the English Channel with the most detrimental consequences for the fauna and flora of water areas. 4 nuclear submarines sank in the waters of the North Atlantic: 2 Soviet (in the Bay of Biscay and the open ocean) and 2 American (off the coast of the United States and in the open ocean).

Atlantic coast states

On the shores of the Atlantic Ocean and its constituent seas there are states and dependent territories:

• In Europe (from north to south): Iceland, Norway, Sweden, Finland, Russian Federation, Estonia, Latvia, Lithuania, Poland, Federal Republic of Germany, Denmark, Netherlands, Belgium, United Kingdom, Ireland, Isle of Man (a British possession), Jersey (British possession), France, Spain, Portugal, Gibraltar (British possession), Italy, Malta, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Albania, Greece, Turkey, Bulgaria, Romania, Ukraine, Abkhazia (not recognized by the UN), Georgia;
• In Asia: Cyprus, Turkish Republic of Northern Cyprus (not recognized by the UN), Akrotiri and Dhekelia (possession of Great Britain), Syria, Lebanon, Israel, Palestinian Authority (not recognized by the UN);
• In Africa: Egypt, Libya, Tunisia, Algeria, Morocco, Sahrawi Arab Democratic Republic (not recognized by the UN), Mauritania, Senegal, Gambia, Cape Verde, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast , Ghana, Togo, Benin, Nigeria, Cameroon, Equatorial Guinea, Sao Tome and Principe, Gabon, Republic of the Congo, Angola, Democratic Republic of the Congo, Namibia, South Africa, Bouvet Island (possession of Norway), Saint Helena, Ascension and Tristan da Cunha (British possession);
• In South America (from south to north): Chile, Argentina, South Georgia and the South Sandwich Islands (British possession), Falkland Islands (British possession), Uruguay, Brazil, Suriname, Guyana, Venezuela, Colombia, Panama;
• In the Caribbean: US Virgin Islands (US possession), Anguilla (British possession), Antigua and Barbuda, Bahamas, Barbados, British Virgin Islands (British possession), Haiti, Grenada, Dominica, Dominican Republic, Cayman Islands (British possession) , Cuba, Montserrat (British possession), Navassa (US possession), Puerto Rico (US possession), St. Vincent and the Grenadines, Saint Kitts and Nevis, St. Lucia, Turks and Caicos (British possession), Trinidad and Tobago , Jamaica;
• In North America: Costa Rica, Nicaragua, Honduras, Guatemala, Belize, Mexico, United States of America, Bermuda (a British possession), Canada.

History of European exploration of the Atlantic Ocean

Long before the era of great geographical discoveries, numerous ships plied the expanses of the Atlantic. As early as 4000 BC, the peoples of Phoenicia conducted maritime trade with the inhabitants of the islands of the Mediterranean Sea. At a later time, from the 6th century BC, the Phoenicians, according to the testimony of the Greek historian Herodotus, made voyages around Africa, and through the Strait of Gibraltar and around the Iberian Peninsula they reached the British Isles. By the 6th century BC, Ancient Greece, having a huge military merchant fleet at that time, sailed to the shores of England and Scandinavia, in the Baltic Sea and to the western coast of Africa. In the X-XI centuries. The Vikings wrote a new page in the study of the North Atlantic Ocean. According to most researchers of pre-Columbian discoveries, the Scandinavian Vikings were the first to cross the ocean more than once, reaching the shores of the American continent (they called it Vinland) and discovering Greenland and Labrador.

In the 15th century, Spanish and Portuguese sailors began to make long voyages in search of routes to India and China. In 1488, the Portuguese expedition of Bartolomeu Dias reached the Cape of Good Hope and circumnavigated Africa from the south. In 1492, Christopher Columbus's expedition mapped many of the Caribbean islands and the vast continent later called America. In 1497, Vasco da Gama walked from Europe to India, circumnavigating Africa from the south. In 1520, Ferdinand Magellan, during his first circumnavigation of the world, passed the Strait of Magellan from the Atlantic to the Pacific Ocean. At the end of the 15th century, the rivalry between Spain and Portugal for supremacy in the Atlantic became so intense that the Vatican was forced to intervene in the conflict. In 1494, an agreement was signed, which established the so-called along 48-49° west longitude. "Papal Meridian" All lands to the west of it were given to Spain, and to the east - to Portugal. In the 16th century, as colonial wealth was being developed, the waves of the Atlantic began to regularly ply ships carrying gold, silver, precious stones, pepper, cocoa and sugar to Europe. Weapons, fabrics, alcohol, food and slaves for cotton and sugar cane plantations were delivered to America along the same route. It is not surprising that in the XVI-XVII centuries. Piracy and privateering flourished in these parts, and many famous pirates, such as John Hawkins, Francis Drake and Henry Morgan, wrote their names in history. The southern border of the Atlantic Ocean (the continent of Antarctica) was discovered in 1819-1821 by the first Russian Antarctic expedition of F. F. Bellingshausen and M. P. Lazarev.

The first attempts to study the seabed were made in 1779 near the coast of Denmark, and serious scientific research began in 1803-1806 with the first Russian round-the-world expedition under the command of naval officer Ivan Krusenstern. Temperature measurements at various depths were carried out by J. Cook (1772), O. Saussure (1780), and others. Participants in subsequent trips measured the temperature and specific gravity of water at different depths, took samples of water transparency and determined the presence of underwater currents. The collected material made it possible to compile a map of the Gulf Stream (B. Franklin, 1770), a map of the depths of the northern part of the Atlantic Ocean (M. F. Morey, 1854), as well as maps of winds and ocean currents (M. F. Morey, 1849-1860) and conduct other studies.

From 1872 to 1876, the first scientific oceanic expedition took place on the English sailing-steam corvette Challenger, new data were obtained on the composition of ocean waters, flora and fauna, bottom topography and soils, the first map of ocean depths was compiled and the first collection was collected deep-sea animals, as a result of which extensive material was collected, published in 50 volumes. It was followed by expeditions on the Russian sail-screw corvette Vityaz (1886-1889), on the German ships Valdivia (1898-1899) and Gauss (1901-1903) and others. The largest work was carried out on the English ship Discovery II (since 1931), thanks to which oceanographic and hydrobiological studies were carried out in the open part of the South Atlantic at great depths. As part of the International Geophysical Year (1957-1958), international forces (especially the USA and the USSR) carried out research, which resulted in the compilation of new bathymetric and marine navigation maps of the Atlantic Ocean. In 1963-1964, the Intergovernmental Oceanographic Commission conducted a large expedition to study the equatorial and tropical zones of the ocean, in which the USSR took part (on the ships “Vityaz”, “Mikhail Lomonosov”, “Akademik Kurchatov” and others), the USA, Brazil and others countries.

In recent decades, numerous ocean measurements have been made from space satellites. The result was a bathymetric atlas of the oceans released in 1994 by the American National Geophysical Data Center with a map resolution of 3-4 km and a depth accuracy of ±100 m.

Economic significance

Fisheries and marine industries

The Atlantic Ocean provides 2/5 of the world's catch and its share has been decreasing over the years. In subantarctic and Antarctic waters, notothenia, whiting and others are of commercial importance, in the tropical zone - mackerel, tuna, sardine, in areas of cold currents - anchovies, in temperate latitudes of the northern hemisphere - herring, cod, haddock, halibut, sea bass. In the 1970s, due to overfishing of some fish species, fishing volumes declined sharply, but after the introduction of strict limits, fish stocks are gradually recovering. There are several international fisheries conventions in force in the Atlantic Ocean basin, which aim at the effective and rational use of biological resources, based on the application of scientifically based measures to regulate fishing.

Transport routes

The Atlantic Ocean occupies a leading place in world shipping. Most of the routes lead from Europe to North America. The main navigable straits of the Atlantic Ocean: Bosphorus and Dardanelles, Gibraltar, English Channel, Pas de Calais, Baltic straits (Skagerrak, Kattegat, Oresund, Great and Little Belt), Danish, Florida. The Atlantic Ocean is connected to the Pacific Ocean by the artificial Panama Canal, dug between North and South America along the Isthmus of Panama, and also to the Indian Ocean by the artificial Suez Canal through the Mediterranean Sea. Largest ports: St. Petersburg (general cargo, petroleum products, metals, timber cargo, containers, coal, ore, chemical cargo, scrap metal), Hamburg (machinery and equipment, chemical products, raw materials for metallurgy, oil, wool, timber, food) , Bremen, Rotterdam (oil, natural gas, ores, fertilizers, equipment, food), Antwerp, Le Havre (oil, equipment), Felixstowe, Valencia, Algeciras, Barcelona, ​​Marseille (oil, ore, grain, metals, chemical cargo, sugar , fruits and vegetables, wine), Gioia Tauro, Marsaxlokk, Istanbul, Odessa (raw sugar, containers), Mariupol (coal, ore, grain, containers, oil products, metals, timber, food), Novorossiysk (oil, ore, cement, grain, metals, equipment, food), Batumi (oil, general and bulk cargo, food), Beirut (export: phosphorites, fruits, vegetables, wool, timber, cement, import: cars, fertilizers, cast iron, building materials, food), Port Said, Alexandria (export: cotton, rice, ores, import: equipment, metals, petroleum products, fertilizers), Casablanca (export: phosphorites, ores, citrus fruits, cork, food, import: equipment, fabrics, petroleum products) , Dakar (groundnuts, dates, cotton, livestock, fish, ores, import: equipment, petroleum products, food), Cape Town, Buenos Aires (export: wool, meat, grain, leather, vegetable oil, flaxseed, cotton, import : equipment, iron ore, coal, oil, industrial goods), Santos, Rio de Janeiro (export: iron ore, pig iron, coffee, cotton, sugar, cocoa beans, lumber, meat, wool, leather, import: petroleum products , equipment, coal, grain, cement, food), Houston (oil, grain, sulfur, equipment), New Orleans (ores, coal, construction materials, cars, grain, rental, equipment, coffee, fruit, food), Savannah, New York (general cargo, oil, chemical cargo, equipment, pulp, paper, coffee, sugar, metals), Montreal (grain, oil, cement, coal, timber, metals, paper, asbestos, weapons, fish, wheat, equipment , cotton, wool).

Air traffic plays a leading role in passenger traffic between Europe and North America across the Atlantic Ocean. Most of the transatlantic lines run in the North Atlantic through Iceland and Newfoundland. Another connection goes through Lisbon, the Azores and Bermuda. The air route from Europe to South America passes through Lisbon, Dakar and then across the narrowest part of the Atlantic Ocean to Rio de Janeiro. Airlines from the United States to Africa pass through the Bahamas, Dakar and Robertsport. On the shores of the Atlantic Ocean there are spaceports: Cape Canaveral (USA), Kourou (French Guiana), Alcantara (Brazil).

Minerals

Mineral extraction, primarily oil and gas, is carried out on continental shelves. Oil is produced on the shelves of the Gulf of Mexico, the Caribbean Sea, the North Sea, the Bay of Biscay, the Mediterranean Sea, and the Gulf of Guinea. Natural gas is also produced on the North Sea shelf. There is industrial mining of sulfur in the Gulf of Mexico, and iron ore off the island of Newfoundland. Diamonds are mined from sea deposits on the South African continental shelf. The next most important group of mineral resources is formed by coastal deposits of titanium, zirconium, tin, phosphorites, monazite and amber. Coal, barite, sand, pebbles and limestone are also mined from the seabed.

Tidal power stations have been built on the shores of the Atlantic Ocean: La Rance on the Rance River in France, Annapolis in the Bay of Fundy in Canada, and Hammerfest in Norway.

Recreational resources

The recreational resources of the Atlantic Ocean are characterized by significant diversity. The main countries of formation of outbound tourism in this region are formed in Europe (Germany, Great Britain, France, Italy, the Netherlands, Belgium, Austria, Sweden, the Russian Federation, Switzerland and Spain), North (USA and Canada) and South America. Main recreational areas: the Mediterranean coast of Southern Europe and North Africa, the coasts of the Baltic and Black Seas, the Florida Peninsula, the islands of Cuba, Haiti, the Bahamas, areas of cities and urban agglomerations of the Atlantic coast of North and South America.

Recently, the popularity of Mediterranean countries such as Turkey, Croatia, Egypt, Tunisia and Morocco has been growing. Among the countries of the Atlantic Ocean with the largest flow of tourists (according to 2010 data from the World Tourism Organization), the following stand out: France (77 million visits per year), USA (60 million), Spain (53 million), Italy (44 million), Great Britain (28 million), Turkey (27 million), Mexico (22 million), Ukraine (21 million), Russian Federation (20 million), Canada (16 million), Greece (15 million), Egypt (14 million), Poland (12 million ), Netherlands (11 million), Morocco (9 million), Denmark (9 million), South Africa (8 million), Syria (8 million), Tunisia (7 million), Belgium (7 million), Portugal (7 million) , Bulgaria (6 million), Argentina (5 million), Brazil (5 million).

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It is large in length (16 thousand km) from north to south - from Arctic to Antarctic latitudes and relatively small in width, especially in equatorial latitudes, where it does not exceed 2,900 km. The average ocean depth is 3597 m, the maximum is 8742 m (Puerto Rico Trench). It was the Atlantic Ocean, with its peculiarities of configuration, age and bottom topography, that served as the basis for the development of the theory of continental drift - the theory of mobilism - the movement of lithospheric plates. It was formed as a result of the split of Pangea, and then the separation of Laurasia and Gondwana. The main processes of formation of the Atlantic occurred in the Cretaceous period. The axial zone of the ocean is the “S”-shaped Mid-Atlantic Ridge, rising above the bottom of the basin by an average of 2000 m, and in Iceland, taking into account its surface part, by more than 4000 m. The Mid-Atlantic Ridge is young, tectonic processes are active in it and to the present day, as evidenced by earthquakes, surface and underwater volcanism.

Unlike other oceans, there are significant areas of continental crust in the Atlantic (off the coast of Scotland, Greenland, the Blake Plateau, at the mouth of La Plata), which indicates the youth of the ocean.

In the Atlantic, as in other oceans, planetary morphostructures are distinguished: underwater continental margins (shelf, continental slope and continental foot), transition zones, mid-ocean ridges and the ocean floor with a series of basins.

Characteristic features of the Atlantic shelf are the presence of two types (glacial and normal) and unequal width off the coasts of North and South America, Europe and Africa.

The glacial shelf is confined to areas of development of modern and cover Quaternary glaciation; it is well developed in the northern part of the Atlantic, including the North and Baltic seas, and off the coast of Antarctica. The glacial shelf is characterized by great dissection and widespread development of glacial gouge and accumulative relief. To the south of the islands of Newfoundland and Nova Scotia on the American side and the English Channel on the European side, the glacial shelf is replaced by a normal one. The surface of such a shelf is leveled by accumulative-abrasion processes, which from the beginning of the Quaternary period to the present day have influenced the bottom topography.

The African shelf is very narrow. Its depth is from 110 to 190 m. In the south (near Cape Town) it is terraced. The South American shelf is narrow, with depths up to 90 m, leveled, and gently sloping. In some places there are terraces and weakly defined underwater valleys of large rivers.

The continental slope of the normal shelf is leveled and moves towards the ocean either by a series of terraces with inclination angles of 1-2°, or by a steep ledge with inclination angles of 10-15°, for example, near the Florida and Yucatan peninsulas.

From Trinidad to the mouth of the Amazon, this is a dissected scarp with depths of up to 3500 m with two protrusions: the Guiana and Amazonian marginal plateaus. To the south there is a stepped ledge with blocky forms. Off the coast of Uruguay and Argentina, the slope has a concave shape and is strongly dissected by canyons. The continental slope off the coast of Africa is blocky in nature with well-defined steps near the Cape Verde Islands and the delta of the river. Niger.

Transition zones are areas of junction of lithospheric plates with underthrust (subduction). They occupy a small place in the Atlantic Ocean.

One of these zones - a relic of the Tethys Ocean - is located in the Caribbean-Antilles basin and continues into the Mediterranean Sea. It is separated by the moving Atlantic. In the west, the role of a marginal sea is played by the Caribbean Sea, the Greater and Lesser Antilles form island arcs, they are accompanied by deep-sea trenches - Puerto Rico (8742 m) and Cayman (7090 m). In the south of the ocean, the Scotia Sea borders on the east the South Antilles underwater ridge with chains of volcanic islands forming an arc (South Georgia, South Sandwich Islands, etc.). At the eastern foot of the ridge stretches a deep-sea trench - the South Sandwich (8264 m).

The mid-ocean ridge is the most striking geographic feature of the Atlantic Ocean.

The northernmost link of the Mid-Atlantic Ridge itself is the Reykjanes Ridge - at 58° N. w. limited by the sublatitudinal zone of the Gibbs faults. The ridge has a clear rift zone and flanks. U o. The Icelandic ridge crest has steep scarps, and the Gibbs Fault is a double chain of trenches with structural offsets of up to 350 km.

District o. Iceland, the above-water part of the North Atlantic Ridge, is a very active rift structure passing through the entire island, with the manifestation of spreading, as evidenced by the basaltic composition of the entire shaft of the ridge, the youth of sedimentary rocks, the symmetry of anomalous magnetic lines, increased heat flow from the interior, the presence of numerous small earthquakes, ruptures of structures (transform faults), etc.

On a physical map, the pattern of the Mid-Atlantic Ridge can be traced along the islands: o. Iceland, on the eastern slope - the Azores, on the equator - o. St. Paul, southeast - Fr. Ascension, then Fr. St. Helena, Fr. Tristan da Cunha (between Cape Town and Cape Town) and Fr. Bouvet. After skirting Africa, the Mid-Atlantic Ridge connects with the ridges.

The northern part of the Mid-Atlantic Ridge (up to the Azores) has a width of 1100-1400 km and represents an arc convex to the east.

This arc is cut by transverse faults - Faraday (49° N), Maxwell (48° N), Humboldt (42° N), Kurchatov (41° N). The flanks of the ridge are gently sloping surfaces with block-block-ridge relief. Northeast of the Azores there are two ridges (Poliser and Mesyatseva). The Azores plateau is located at the site of a triple junction of plates (oceanic and two continental). The southern part of the North Atlantic Ridge to the equator also looks like an arc, but its convex part faces the west. The width of the ridge here is 1600-1800 km, narrowing towards the equator to 900 km. Throughout its entire length, the rift zone and flanks are dissected by transform faults that look like trenches, some of which extend into neighboring basins of the ocean floor. The most well studied transform faults are Oceanographer, Atlantis, and Romany (at the equator). The displacement of structures in faults ranges from 50-550 km with a depth of up to 4500 m, and in the Romanche Trench - 7855 m.

South Atlantic Ridge from the equator to the island. Bouvet has a width of up to 900 km. Here, as well as in the North Atlantic, the rift zone with depths of 3500-4500 m is developed.

The faults of the southern part are Chain, Ascension, Rio Grande, Falkland. On the eastern flank, the mountains of Bagration, Kutuzov, and Bonaparte rise on underwater plateaus.

In Antarctic waters, the African-Antarctic Ridge is not wide - only 750 km, dissected by a series of transform faults.

A characteristic feature of the Atlantic is the fairly clear symmetry of the orographic structures of the bed. On both sides of the Mid-Atlantic Ridge there are basins with a flat bottom, successively replacing each other from north to south. They are separated by small underwater ridges, rapids, and rises (for example, Rio Grande, Whale), successively replacing each other from north to south.

In the extreme north-west there is the Labrador Basin, more than 4000 m deep - a flat abyssal plain with a thick two-kilometer sedimentary cover. Next is the Newfoundland Basin (maximum depth more than 5000 m), with an asymmetrical bottom structure: in the west it is a flat abyssal plain, in the east it is hilly.

The North American Basin is the largest in size. In the center is the Bermuda Plateau with a thick layer of sediment (up to 2 km). Drilling revealed Cretaceous deposits, but geophysical data indicate that there is an even more ancient formation beneath them. Volcanic mountains form the base of the Bermuda Islands. The islands themselves are composed of coral limestones and represent a giant atoll, which is rare for the Atlantic Ocean.

To the south is the Guyana Basin, part of which is occupied by the Para Threshold. It can be assumed that the threshold is of accumulative origin and is associated with the accumulation of material from turbidity currents feeding on the huge removal of solid sediment from the Amazon (more than 1 billion tons per year).

Even further south is the Brazilian Basin with a ridge of seamounts, at the top of one of which is the only coral atoll in the South Atlantic, Rocas.

The largest basin in the South Atlantic is the African-Antarctic basin - from the Scotia Sea to the Kerguelen Rise, its length is 3500 miles, width - about 800 miles, maximum depth - 6972 m.

In the eastern part of the ocean floor there is also a series of basins, often separated by volcanic uplifts: in the area of ​​​​the Azores Islands, near the Cape Verde Islands and the Cameroon fault. The basins of the eastern part (Iberian, Western European, Canary, Angolan, Cape) are characterized by the oceanic type of the earth's crust. The sedimentary cover of Jurassic and Cretaceous age has a thickness of 1-2 km.

Ridges play an important role in the ocean as environmental barriers. The basins differ from each other in bottom sediments, soils, and a complex of minerals.

Bottom sediments

Among the bottom sediments of the Atlantic, the most common are foraminiferal silts, occupying about 65% of the ocean floor area, in second place are deep-sea red and red-brown clays (about 20%). Terrigenous deposits are widespread in the basins. The latter are especially characteristic of the Guinea and Argentine basins.

Ocean sediments and bedrock contain a wide range of minerals. The Atlantic Ocean is rich in oil and gas fields.

The most famous deposits are in the Gulf of Mexico, the North Sea, the Bay of Biscay and Guinea, the Maracaibo lagoon, and coastal regions near the Falkland (Malvinas) Islands. New gas fields are discovered every year: off the east coast of the United States, in the Caribbean and North Seas, etc. By 1980, 500 fields were discovered on the shelf off the coast of the United States, and more than 100 in the North Sea. Deep-sea exploration is increasingly being used to search for minerals. drilling. In the Gulf of Mexico, for example, Glomar Challenger drilled and discovered a salt dome at a depth of 4000 m, and off the coast of Iceland, in an area with sea depths from 180 to 1100 m and a thick four-kilometer sediment cover, an oil-bearing well was drilled with a flow rate of 100-400 tons per hour. day.

In coastal waters with thick ancient and modern alluvium, there are deposits of gold, tin, and diamonds. Monazite sands are mined off the coast of Brazil. This is the world's largest deposit. There are known deposits of ilmenite and rutile off the coast of Florida (USA). The largest placers of ferromanganese nodules and phosphorite deposits belong to the regions of the South Atlantic.

Features of the climate of the Atlantic Ocean

The climate of the Atlantic Ocean is largely determined by its large meridional extent, the peculiarities of the formation of the pressure field, and the unique configuration (there are more water areas in temperate latitudes than in equatorial-tropical latitudes). On the northern and southern outskirts there are huge regions of cooling and the formation of centers of high atmospheric pressure. Constant areas of low pressure in subequatorial and temperate latitudes and high pressure in subtropical latitudes are also formed over the ocean.

These are the Equatorial and Antarctic depressions, the Icelandic minimum, the North Atlantic (Azores) and the South Atlantic maximums. The position of these centers of action changes with the seasons: they shift towards the summer hemisphere.

Trade winds blow from subtropical highs towards the equator. The stability of the direction of these winds is up to 80% per year, the strength of the winds is more variable - from 1 to 7 points. In the temperate latitudes of both hemispheres, winds of westerly components dominate, with significant speeds, often turning into storms in the Southern Hemisphere - the so-called “roaring forties” latitudes.

The distribution of atmospheric pressure and the characteristics of air masses affect the nature of cloudiness, the regime and amount of precipitation. Cloudiness over the ocean varies by zone: the maximum amount of clouds near the equator with a predominance of cumulus and cumulonimbus forms, the least cloudiness in tropical and subtropical latitudes, in moderate the amount of clouds increases again - stratus and nimbostratus forms dominate here.

Very characteristic of the temperate latitudes of both hemispheres (especially the Northern) are dense fogs that form when warm air masses come into contact with cold ocean waters, as well as when the waters of cold and warm currents meet near the island. Newfoundland. Particularly thick summer fogs in this area make navigation difficult, especially since icebergs are often found there. In tropical latitudes, fogs are most likely around the Cape Verde Islands, where dust blown from the Sahara serves as condensation nuclei for atmospheric water vapor. Fogs are also common off the southwestern coast of Africa in the climate region of “wet” or “cold” deserts.

A very dangerous phenomenon in the tropical latitudes of the ocean is tropical cyclones, causing hurricane winds and heavy rainfall. Tropical cyclones often develop from small depressions moving from the African continent to the Atlantic Ocean. Gaining strength, they become especially dangerous for the islands of the West Indies and southern North America.

Temperature

On the surface, the Atlantic Ocean is generally colder than the Indian Ocean due to its large extent from north to south, its small width near the equator, and its wide connection with.

The average surface water is 16.9°C (according to other sources - 16.53°C), while in the Pacific - 19.1°C, Indian - 17°C. The average temperature of the entire water mass of the Northern and Southern Hemispheres also differs. Mainly due to the Gulf Stream, the average water temperature of the North Atlantic (6.3°C) is slightly higher than the South Atlantic (5.6°C).

Seasonal temperature changes are also clearly visible. The lowest temperatures are recorded in the north and south of the ocean, and the highest - vice versa. However, the annual temperature amplitude at the equator is no more than 3°C, in subtropical and temperate latitudes - 5-8°C, in the polar latitudes - about 4°C. Daily fluctuations in the temperature of the surface layer are even smaller - on average 0.4-0.5°C.

The horizontal temperature gradient of the surface layer is significant where cold and warm currents meet, such as the East Greenland and Irminger currents, where a temperature difference of 7°C over a distance of 20-30 km is common.

Annual temperature fluctuations are clearly visible in the surface layer up to 300-400 m.

Salinity

The Atlantic Ocean is the saltiest of all. The salt content in the waters of the Atlantic averages 35.4%, which is higher than in other oceans.

The highest salinity is observed in tropical latitudes (according to Gembel) - 37.9% o, in the North Atlantic between 20 and 30 ° C. latitude, in the South - between 20 and 25° S. w. Trade wind circulation dominates here, there is little precipitation, and evaporation amounts to a layer of 3 m. Almost no fresh water comes from the land. Salinity is also slightly higher than average in the temperate latitudes of the Northern Hemisphere, where the waters of the North Atlantic Current flow. Salinity in equatorial latitudes is 35% o. There is a change in salinity with depth: at a depth of 100-200 m it is 35.4% o, which is associated with the subsurface Lomonosov Current. It has been established that the salinity of the surface layer does not coincide in some cases with the salinity at depth.

Sharp changes in salt content are also observed when currents of different temperatures meet. For example, south of. In Newfoundland, when the Gulf Stream and Labrador Current meet at a short distance, salinity drops from 35% o to 31-32% o.

The existence of underground fresh water in the Atlantic Ocean - submarine springs (according to I. S. Zetsker) is an interesting feature of it. One of them has long been known to sailors; it is located east of the Florida Peninsula, where ships replenish fresh water supplies. This is a 90-meter “fresh window” in the salty ocean. Here, a typical phenomenon of unloading of an underground source occurs in the area of ​​tectonic disturbances or areas of karst development. When the pressure of groundwater exceeds the pressure of the column of sea water, unloading occurs - the outpouring of groundwater to the surface. A well was recently drilled on the continental slope of the Gulf of Mexico off the coast of Florida. When drilling a well, a column of fresh water 9 m high broke out from a depth of 250 m. The search and study of submarine sources is just beginning.

Optical properties of water

Transparency, on which the illumination of the bottom and the nature of heating of the surface layer depend, is the main indicator of optical properties. It varies over a wide range, which is why the albedo of the water also changes.

The transparency of the Sargasso Sea is 67 m, the Mediterranean - 50, the Black - 25, the Northern and Baltic - 13-18 m. The transparency of the ocean waters far from the shores, in the tropics, is 65 m. The optical structure of the waters of the tropical latitudes of the Atlantic is especially interesting. The waters here are characterized by a three-layer structure: an upper mixed layer, a layer of reduced transparency and deep transparent ones. Depending on hydrological conditions, the thickness, intensity and a number of features of these layers change in time and space. The depth of the layer of maximum transparency decreases from 100 m off the coast of North Africa to 20 meters off the coast of South America. This is due to the turbidity of the waters at the mouth of the Amazon. The waters of the central part of the ocean are homogeneous and transparent. The transparency structure also changes in the upwelling zone off the coast of South Africa due to the increased content of plankton. The boundaries between layers with different opacity are often blurred and indistinct. Against the mouth of the river. Congo also has a three-layer profile; to the north and south there is a two-layer profile. In the Guinean sector of the Atlantic, the picture is the same as at the mouth of the Amazon: a lot of solid particles are carried into the ocean by rivers, in particular the river. Congo. Here is a place where currents converge and diverge; deep clear waters rise along the continental slope.

Water dynamics

They learned about existence in the ocean relatively recently; even the Gulf Stream became known only at the beginning of the 16th century.

In the Atlantic Ocean there are currents of various origins: drift - North and South Trade Winds, Western Drift or Western Winds (with a flow rate of 200 sverdrup), katabatic (Florida), tidal. In the Bay of Fundy, for example, the tide level reaches record levels (up to 18 meters). There are also density countercurrents (for example, the Lomonosov countercurrent is subsurface).

Powerful surface currents in tropical latitudes of the ocean are caused by trade winds. These are the Northern and Southern Trade Winds, moving from east to west. They branch off the eastern coasts of both Americas. In the summer, the Intertrade Countercurrent manifests itself most effectively; its axis moves from 3° to 8° N. w. The Northern Trade Wind Current near the Antilles divides into branches. One goes to the Caribbean Sea and the Gulf of Mexico, the other - the Antilles branch merges with the Florida branch and, leaving the gulf, forms a giant warm Gulf Stream current. This current, together with its branches, has a length of more than 10 thousand km, the maximum flow rate is 90 sverdrup, the minimum is 60, the average is 69. The water flow in the Gulf Stream is 1.5-2 times greater than that of the largest currents of the Pacific and Indian Oceans - Kuroshio and Somalia. The width of the stream is 75-100 km, the depth is up to 1000 m, the speed of movement is up to 10 km/h. The Gulf Stream boundary is determined by an isotherm of 15°C at a depth of 200 m. Salinity is more than 35% o, in the southern branch - 35.1% o. The main flow reaches 55° W. e. Before this segment, there is almost no transformation of the water mass on the surface; at a depth of 100-300 m, the properties of the flow do not change at all. At Cape Hatteras (Gateras), the waters of the Gulf Stream are divided into a series of narrow, strongly meandering streams. One of them, with a consumption of approximately 50 sverdrup, goes to the Newfoundland Bank. From 41° W. The North Atlantic Current begins. Rings are observed in it - vortices moving in the direction of the general movement of water.

The North Atlantic Current also “branches”, the Portuguese branch separates from it, which merges with the Canary Current. In the north, the Norwegian branch is formed and then the North Cape. The Irminger Current departs to the northwest, meeting the cold runoff East Greenland Current. The West Greenland Current in the south connects with the Labrador Current, which, mixing with the warm current, leads to a deterioration in meteorological conditions in the area of ​​the Newfoundland Bank. The water temperature in January is 0°C, in July - 12°C. The Labrador Current often carries icebergs into the ocean south of Greenland.

The Southern Trade Wind Current off the coast of Brazil bifurcates into the Guiana Current and the Brazilian Current, and to the north the Guiana Current merges with the North Trade Wind Current. Brazilian in the south about 40° S. w. connects with the Western Winds Current, from which the cold Benguela Current departs to the coast of Africa. It merges with the South Trade Wind, and the southern ring of currents closes. The cold Falklands approaches the Brazilian from the south.

The Lomonosov countercurrent, discovered in the 60s of the 20th century, has a direction from west to east, passes at a depth of 300-500 m in the form of a huge river several hundred kilometers wide.

In the southern part of the North Trade Wind, eddies of an anticyclonic nature were discovered with a movement speed of 5.5 cm/sec. In the ocean there are eddies of large diameters - 100-300 km (medium ones have a diameter of 50 km, small ones - 30 km). The discovery of these vortices, called synoptic vortices, is of great importance for plotting the course of ships. Artificial Earth satellites provide enormous assistance in compiling maps indicating the direction and speed of movement of synoptic vortices.

The dynamics of ocean waters have enormous energy potential, which has hardly been used to date. And although the ocean is in most cases less concentrated and less convenient to use than the energy of rivers, scientists believe that these are inexhaustible resources, constantly renewable. Tidal energy comes first.

The first successfully operating tidal water mills were built in England (Wales) back in the 10th-11th centuries. Since then, they have been constantly built on the shores of Europe and North America. However, serious energy projects appeared in the 20s of the 20th century. The possibilities of using tides as energy sources are most likely off the coasts of France, Great Britain, and the USA. The first small-scale tidal power plants are already in operation.

Work is underway to harness the thermal energy of the oceans. The surface layer of water in tropical latitudes can heat up with seasonal variations being insignificant. At a depth (300-500 m) the water temperature is only 8-10°C. The difference is even sharper in upwelling zones. Temperature differences can be used to generate energy in water-steam turbines. The first ocean experimental thermal station with a capacity of 7 MW was created by French scientists near Abidjan (Côte d'Ivoire).

The Atlantic Ocean is second in size only to the Pacific Ocean, its area is approximately 91.56 million km². It is distinguished from other oceans by its highly rugged coastline, forming numerous seas and bays, especially in the northern part. In addition, the total area of ​​river basins flowing into this ocean or its marginal seas is significantly larger than that of rivers flowing into any other ocean. Another difference of the Atlantic Ocean is the relatively small number of islands and the complex bottom topography, which, thanks to underwater ridges and rises, forms many separate basins.

North Atlantic Ocean

Borders and coastline. The Atlantic Ocean is divided into northern and southern parts, the border between which is conventionally drawn along the equator. From an oceanographic point of view, however, the southern part of the ocean should include the equatorial countercurrent, located at 5-8° N latitude. The northern border is usually drawn along the Arctic Circle. In some places this boundary is marked by underwater ridges.

In the Northern Hemisphere, the Atlantic Ocean has a highly indented coastline. Its relatively narrow northern part is connected to the Arctic Ocean by three narrow straits. In the northeast, the 360 ​​km wide Davis Strait (at the latitude of the Arctic Circle) connects it with the Baffin Sea, which belongs to the Arctic Ocean. In the central part, between Greenland and Iceland, there is the Denmark Strait, at its narrowest point only 287 km wide. Finally, in the northeast, between Iceland and Norway, there is the Norwegian Sea, approx. 1220 km. In the east, two water areas protruding deeply into the land are separated from the Atlantic Ocean. The more northern of them begins with the North Sea, which to the east passes into the Baltic Sea with the Gulf of Bothnia and the Gulf of Finland. To the south there is a system of inland seas - the Mediterranean and the Black - with a total length of approx. 4000 km. In the Strait of Gibraltar, which connects the ocean with the Mediterranean Sea, there are two oppositely directed currents, one below the other. The current moving from the Mediterranean Sea to the Atlantic Ocean occupies a lower position, since Mediterranean waters, due to more intense evaporation from the surface, are characterized by greater salinity and, consequently, greater density.

In the tropical zone in the southwest of the North Atlantic are the Caribbean Sea and the Gulf of Mexico, connected to the ocean by the Strait of Florida. The coast of North America is indented by small bays (Pamlico, Barnegat, Chesapeake, Delaware and Long Island Sound); to the northwest are the Bays of Fundy and St. Lawrence, the Strait of Belle Isle, Hudson Strait and Hudson Bay.

The largest islands are concentrated in the northern part of the ocean; these are the British Isles, Iceland, Newfoundland, Cuba, Haiti (Hispaniola) and Puerto Rico. On the eastern edge of the Atlantic Ocean there are several groups of small islands - the Azores, Canary Islands, and Cape Verde. Similar groups exist in the western part of the ocean. Examples include the Bahamas, Florida Keys and Lesser Antilles. The Greater and Lesser Antilles archipelagos form an island arc surrounding the eastern Caribbean Sea. In the Pacific Ocean, such island arcs are characteristic of areas of crustal deformation. Deep-sea trenches are located along the convex side of the arc.

The Atlantic Ocean basin is bordered by a shelf, the width of which varies. The shelf is cut through by deep gorges - the so-called. underwater canyons. Their origin is still controversial. One theory is that the canyons were cut by rivers when sea levels were lower than they are today. Another theory connects their formation with the activity of turbidity currents. It has been suggested that turbidity currents are the main agent responsible for the deposition of sediment on the ocean floor and that they are the ones that cut submarine canyons.

The bottom of the North Atlantic Ocean has a complex, rugged topography formed by a combination of underwater ridges, hills, basins and gorges. Most of the ocean floor, from depths of about 60 m to several kilometers, is covered with thin, dark blue or bluish-green muddy sediments. A relatively small area is occupied by rocky outcrops and areas of gravel, pebble and sandy deposits, as well as deep-sea red clays.

Telephone and telegraph cables were laid on the shelf in the North Atlantic Ocean to connect North America with Northwestern Europe. Here, the area of ​​the North Atlantic shelf is home to industrial fishing areas that are among the most productive in the world.

In the central part of the Atlantic Ocean, almost repeating the contours of the coastlines, there is a huge underwater mountain range approx. 16 thousand km, known as the Mid-Atlantic Ridge. This ridge divides the ocean into two approximately equal parts. Most of the peaks of this underwater ridge do not reach the ocean surface and are located at a depth of at least 1.5 km. Some of the highest peaks rise above ocean level and form the islands - the Azores in the North Atlantic and Tristan da Cunha - in the South. In the south, the ridge skirts the coast of Africa and continues further north into the Indian Ocean. A rift zone stretches along the axis of the Mid-Atlantic Ridge.

Surface currents in the North Atlantic Ocean move clockwise. The main elements of this large system are the northward warm Gulf Stream, as well as the North Atlantic, Canary and North Trade Wind (Equatorial) Currents. The Gulf Stream follows from the Strait of Florida and Cuba in a northerly direction along the coast of the United States and approximately 40° N. w. deviates to the northeast, changing its name to the North Atlantic Current. This current is divided into two branches, one of which follows northeast along the coast of Norway and further into the Arctic Ocean. It is thanks to it that the climate of Norway and all of northwestern Europe is much warmer than would be expected at latitudes corresponding to the area extending from Nova Scotia to southern Greenland. The second branch turns south and further southwest along the coast of Africa, forming the cold Canary Current. This current moves southwest and joins the North Trade Wind Current, which heads west towards the West Indies, where it merges with the Gulf Stream. To the north of the North Trade Wind Current there is an area of ​​stagnant waters, teeming with algae, known as the Sargasso Sea. The cold Labrador Current runs along the North Atlantic coast of North America from north to south, coming from Baffin Bay and the Labrador Sea and cooling the shores of New England.

South Atlantic Ocean

Some experts refer to the Atlantic Ocean in the south all the water space up to the Antarctic ice sheet; others take the southern limit of the Atlantic to be an imaginary line connecting Cape Horn in South America with the Cape of Good Hope in Africa. The coastline in the southern part of the Atlantic Ocean is much less indented than in the northern part; there are also no inland seas through which the influence of the ocean could penetrate deep into the continents of Africa and South America. The only large bay on the African coast is the Gulf of Guinea. On the coast of South America, large bays are also few in number. The southernmost tip of this continent - Tierra del Fuego - has an indented coastline bordered by numerous small islands.

There are no large islands in the southern part of the Atlantic Ocean, but there are isolated isolated islands, such as Fernando de Noronha, Ascension, Sao Paulo, St. Helena, the Tristan da Cunha archipelago, and in the extreme south - Bouvet, South Georgia , South Sandwich, South Orkney, Falkland Islands.

In addition to the Mid-Atlantic Ridge, there are two main submarine mountain ranges in the South Atlantic. The whale ridge extends from the southwestern tip of Angola to the island. Tristan da Cunha, where it joins the Mid-Atlantic. The Rio de Janeiro Ridge stretches from the Tristan da Cunha Islands to the city of Rio de Janeiro and consists of groups of individual underwater hills.

The major current systems in the South Atlantic Ocean move counterclockwise. The South Trade Wind Current is directed to the west. At the protrusion of the eastern coast of Brazil, it splits into two branches: the northern one carries water along the northern coast of South America to the Caribbean, and the southern one, the warm Brazil Current, moves south along the coast of Brazil and joins the Western Winds Current, or Antarctic Current, which heads east , and then to the northeast. Part of this cold current separates and carries its waters north along the African coast, forming the cold Benguela Current; the latter eventually joins the South Trade Wind Current. The warm Guinea Current moves south along the coast of Northwest Africa into the Gulf of Guinea.

The Atlantic Ocean is the most studied and developed by people of all the oceans. It got its name from the titan Atlas (according to Greek mythology, holding the vault of heaven on his shoulders). At different times it was called differently: “The Sea beyond the Pillars of Hercules”, “Atlantic”, “Western Ocean”, “Sea of ​​Darkness”, etc. The name "Atlantic Ocean" first appeared in 1507 on the Wald-Semüller map, since then the name has been firmly established.

The boundaries of the Atlantic Ocean along the shores of 4 continents (Eurasia, Africa, North and South America) are natural, with oceans - conditional: in the north with the Arctic Ocean, in the west and east, respectively, with the Pacific and Indian Oceans. The principle of drawing boundaries among a number of authors is different: A. V. Gembel believes that the most representative are boundaries drawn according to hydrological data (water balance, salinity; temperature and water dynamics). However, the lack of sufficient data in a number of regions does not allow us to take these factors into account and draw boundaries based on them. Therefore, most often, boundaries are drawn along orographic units: underwater plateaus, ridges, shoals, islands where there are no talons - along rhoxodromes. Those. lines cutting the meridians at the same angle. The border with the Arctic Ocean is usually drawn at 70°N. Baffin Island - Disko Island, Cape Brewster (Greenland) - 61° N. on the Scandinavian Peninsula; border with the Pacific Ocean, Oste Island (Terra del Fuego) to Cape Sterneck (Antarctica); border with the Indian Ocean - Cape Agulhas, and 20° E. to Antarctica. The remaining borders are land, along the coastlines of the continents. Within the designated boundaries, the ocean area is 91.7 million km 2, the volume of water is 329.7 million km 3, the average depth is 3597 m, the greatest depth is 8742 m (in the Puerto Rico Trench). The greatest length of the ocean along the meridian is about 15 thousand km. The width at its narrowest point - between Labrador and the coast of Norway - is about 2620 km, and at its widest - between the shores of Mexico and the Strait of Gibraltar - 9450 km. Water exchange occurs in 46 years, which is 2 times faster than in the Pacific Ocean.

The Atlantic Ocean was formed in the Mesozoic as a result of the breakup of the supercontinent Pangea. The split of Pangea went from north to south and began in the Triassic and ended in the Cretaceous. The Atlantic Ocean then expanded due to the westward movement of the North American and South American plates. In the Cenozoic, the Tethys Ocean closed and the African Plate shifted northward. In the North Atlantic Ocean, the spreading zone was located between North America and Greenland, where Baffin Bay is now located. Then spreading moved east, between Greenland and the Scandinavian Peninsula.

A characteristic element of the bottom topography Atlantic Ocean is the huge meridional Mid-Atlantic Ridge that divides ocean to the eastern and western parts.

The floor of the Atlantic Ocean in its northern part belongs to the North American and Eurasian plates; the central and southern parts are underlain by the South American, African, Caribbean plates and the Scotia plate in the south.

To the west and east of the Middle Ridge in the ocean floor area there are underwater plateaus (Bermuda, Rio Grande), ridges (South Antilles, Whale) and hills (Rockall and Sierra Leone). Bottom elevations separate vast basins: Labrador, North American, Guiana, Brazilian, Argentine and others in the west; Western European, North African, Guinean, Angolan, Cape, Agulhas in the east; African-Antarctic basins in the south depth from 3000 to 7200-7300 m. Maximum depths Atlantic Ocean associated with deep-sea trenches bordering the mountain systems of island arcs - the Greater Antilles (Puerto Rico trench, 8385 m) and the South Sandwich Islands (South Sandwich, 8428 m). The Greater and Lesser Antilles island arcs are separated from the exposed parts Atlantic Ocean The Mexican, Yucatan (with the Cayman Trench), Colombian and Venezuelan basins, and the threshold of the Strait of Gibraltar is the basin of the Mediterranean Sea. The beds of the basins are hilly or almost flat abyssal plains, only in some places complicated by seamounts. The peaks of the mountains in some places protrude above the water in the form of volcanic islands (Bermuda, Azores, Canaries, Cape Verde, Fernando de Noronha, Martin Vas, St. Helena, Tristan da Cunha, Gough, etc.). The largest seamounts: Altair, Anti-Altair, Milne, Kelvin, San Pablo, Rehobos, Ronqueway, Yakutat, Atlantis, Plateau, Cruiser, Great Metsor, Josephine, Ampere, Davis, Columbia, Discovery, Schmitt-Ott, Meteor , Alfred Mere et al.

The underwater margins of the continents surrounding the depression Atlantic Ocean, are characterized by gently sloping continental shoal plains and steep continental slopes. The latter are cut by underwater canyons, located mostly on the continuation of river valleys on land. The width of continental shoals ranges from several tens of kilometers (off the coast of Argentina, North America) to several hundred kilometers (North, Baltic and other seas). The depths of the outer edge of the continental shelves range from 100 to 500 m.

The underwater margins of continents are characterized by a continental type of crust and continental platform structures, which, as a rule, are cut off by continental slopes. Their continuation towards the ocean has been traced only in the Bay of Biscay and the Bay of Mexico, and is unknown in other places. The bottom of the basins is underlain by the oceanic crust, consisting of three layers: a layer of loose sediments; so-called a “second” layer, characterized by seismic wave velocities of about 5.0 km/sec, which may be composed of sedimentary volcanic or igneous rocks, and a “basalt” layer with seismic wave velocities of the order of 6.7 km/sec, which is probably composed of basic rocks such as gabbro-basalt and serpentinized ultramafic rocks. Below lie the rocks of the upper mantle, characterized by seismic wave velocities of about 8.3 km/sec and represented by peridotites and dunites. In the structure of the Mid-Atlantic Ridge, the sedimentary layer is almost absent, the “second” and “basalt” layers are thinned, and in the rift zone they are broken in places, so that ultrabasic rocks are exposed at the bottom. Here, according to seismic data, decompressed rocks of the upper mantle lie

The Atlantic Ocean, which is elongated in the meridional direction, is characterized by a well-defined zonality in the distribution and composition of sediments. Bottom sediments Atlantic Ocean, the maximum thickness of which in the bottoms of basins reaches 800−1000 m, according to their origin they are divided into several types.

Terrigenous deposits (gravel-pebble, sandy and silty material) are distributed mainly on the underwater margins of continents.

Biogenic sediments are represented by carbonate (more than 30%) and siliceous (more than 10%) sediments. Carbonate sediments (65% of the bottom area) line the slopes of the Mid-Atlantic Ridge, significant areas of the basin floors and the slopes of underwater rises within them. Siliceous sediments (about 10% of the bottom area) are distributed only in the southern part of the ocean, near Antarctica.

Polygenic sediments (about 26% of the bottom area), of mixed origin, are represented by red deep-sea clays that line the deepest parts of the basins. Volcanogenic sediments - sediments mixed with volcanic ash - are common in areas of volcanic islands.

The so-called rift sediments, which are products of the destruction of deep rocks, are confined to the rift gorges of the axial zone of the Mid-Atlantic Ridge.

Chemogenic deposits are developed in the form of glauconite sands and phosphorite nodules in the area of ​​underwater continental margins and in the form of ferromanganese nodules on the bed of deep basins. In the northern and southern parts Atlantic Ocean The transport of coarse clastic material by floating ice and icebergs has a significant impact on the composition of bottom sediments. Among the sediments of deep basins, sediments of suspension flows play an important role. Outcrops of bedrock are found on continental slopes in the form of sedimentary and metamorphic formations of various ages, up to the Cretaceous; tholeiitic and alkaline basalts were found on volcanic mountains and islands; on the crests of the ridges of the Mid-Atlantic Ridge - basalts and plutonic rocks of basic (gabbro) and ultrabasic (dunites, peridotites) composition. Serpentinites developed after peridotites and greenstones formed as a result of regional metamorphism of basalts and gabbros at the base of the earth's crust were noted. Ultramafic rocks make up the island. Sao Paulo. It is assumed that they are of deep (mantle) origin and their age is about 4.5 billion years (close to the age of the Earth).

Mining, primarily oil and gas, is produced on continental shelves. The next most important group of mineral resources is formed by coastal deposits of titanium, zirconium, tin, diamonds, phosphorites, monazite and amber.

Large meridional extent Atlantic Ocean determines the diversity of climatic conditions on its surface. Atlantic Ocean located in all climatic zones, from equatorial to subarctic in the north and Antarctic in the south. At the same time, a large area Atlantic Ocean, approximately between 40° N. w. and 40° S. sh., is located in the zones of equatorial, tropical and subtropical climates. Above ocean 4 main centers of atmospheric action are developing - the Icelandic and Antarctic lows, the North Atlantic and South Atlantic highs, which are separated at the equator by a zone of low atmospheric pressure. These centers, when interacting with areas of pressure developing over adjacent continents, determine the dominance of strong westerly winds in temperate latitudes, northeastern and southeastern winds (trade winds) in subtropical and tropical latitudes, respectively, in the Northern and Southern Hemispheres. Winds reach their greatest strength in temperate latitudes, especially in the southern part Atlantic Ocean. Storms are so frequent here that the southern temperate latitudes are called the “Roaring Forties.” Strong winds are also typical for the Bay of Biscay.

For northern tropical latitudes from June to October - November are characterized by tropical, so-called. West Indian hurricanes crossing the ocean from east to west. They reach their greatest strength over the Caribbean Sea and the Gulf of Mexico; air temperature in winter, in February (August in the southern part Atlantic Ocean), varies from 25°C at the equator to 0°C at 60°N. w. and from −8 to −10°С at 60° south. w. In the extreme northwest and south, temperatures drop to −25 °C and below. In summer, in August (in February in the southern part ocean), the temperature is 26−28°C at the equator, 8−12°C at 60° N. w. and 0−2°С at 60° south. w. In the south of the Weddell Sea the temperature ranges from −4 to −6 °C. Over the entire area Atlantic Ocean, located north of 40° south. sh., there is a noticeable difference between the air temperature of the eastern and western parts of the ocean, caused by the dominance of warm or cold currents in them. North of 30° N. w. temperatures in the west are 10°C lower than in the east, and between 30°C. w. and 40° S. w. in the west it is 5°C higher than in the east.

The average annual cloudiness in areas of low atmospheric pressure in the northern temperate, southern high and equatorial latitudes is 60−80%, in areas of high pressure in the subtropics it decreases to 30−40%. Average annual precipitation: at the equator more than 2000 mm, in temperate latitudes 1000-1500 mm, in subtropical latitudes and in Antarctica it decreases to 250−500 mm, in areas adjacent to the desert coasts of Africa up to 100 mm, in the southern parts of the ocean less 100 mm. Fogs are typical for areas where warm and cold waters meet (Great Newfoundland Bank, near the entrance to La Plata Bay, etc.) and for southern temperate latitudes, where warm air passes over the cold surface of the ocean. In the area of ​​the Cape Verde Islands, dust fogs are observed, brought by the northeast trade wind from the Sahara.

Hydrological regime Atlantic Ocean is formed under the influence of climatic conditions, water exchange with the adjacent oceans and the Mediterranean Sea, as well as the configuration features of the surrounding land. Under the influence of atmospheric circulation, surface currents Atlantic Ocean They form anticyclonic gyres in subtropical and tropical latitudes and cyclonic gyres in northern temperate and southern high latitudes. Characteristic Atlantic Ocean− a powerful system of warm currents, the so-called. the Gulf Stream system developing in its northern part. The Gulf Stream and its continuation, the North Atlantic Current, form, respectively, the western and northern peripheries of the northern anticyclonic gyre. The eastern periphery of this gyre is formed by the cold Canary Current, the southern by the warm North Trade Wind Current. The Northern Cyclonic Gyre is formed by currents - the warm North Atlantic and Irminger currents and the cold Labrador current, coming from the Baffin Sea.

In the southern part ocean the anticyclonic gyre is formed by the warm South Trade Wind and Brazilian currents in the north and west, respectively, and the cold West Winds and Benguela currents in the south and east. The cyclonic gyre develops south of 50° south. w. centered on the Weddell Sea. Anticyclonic circulations of the northern and southern parts Atlantic Ocean are separated in the summer north of the equator by the Intertrade (Equatorial) countercurrent, which in winter is replaced by a general westerly transport of surface waters. A more permanent boundary is the subsurface Lomonosov countercurrent at the equator. Currents are the main redistributors of solar heat absorbed by the ocean surface.

Heat balance Atlantic Ocean consists of the radiation balance, heat loss for evaporation and turbulent heat exchange with the atmosphere. The greatest positive heat balance is 2.5−3.3 GJ/(m 2 year) is observed at the equator and approaches 0 at 30° northern and southern latitudes. As latitude increases, the heat balance becomes negative. Thus, heat absorption by the surface Atlantic Ocean occurs mainly between 30° north and south latitudes; in the rest of the area, the ocean transfers heat to the atmosphere. Surface water temperature ocean in winter, in February (August in the southern part of the ocean), at the equator 27−28°C, at 60° N. w. 6°С, at 60° south. w. −1°С. In summer, in August (February in the southern part of the ocean), the temperature at the equator is 26°C, at 60°N. w. 10°C, at 60° S. w. about 0°C. Under the influence of warm and cold currents, large temperature differences are created within latitudinal zones. North of 30° N. w. in the west the temperature is approximately 10°C lower than in the east. Between 30° N. w. and 40° S. latitude, on the contrary, in the west the temperature is 5°C higher than in the east. South of 40° S. sh., where the zonal flow of surface water predominates, this difference disappears.

Vegetation. Vegetable world Atlantic Ocean very diverse. Bottom vegetation (phytobenthos), occupying the coastal zone to a depth of 100 m(about 2% of the total area of ​​the ocean floor), includes brown, green and red algae, as well as flowering plants living in salt water (philospadix, zoster, poseidonia). Between the bottom vegetation of the northern and southern parts Atlantic Ocean there are similarities, but the leading forms are represented by different species, and sometimes genera. The similarities between the vegetation of the western and eastern coasts are more clearly expressed. There is a clear geographic change in the main forms of phytobenthos along latitude. In high arctic latitudes ocean, where the surface is covered with ice for a long time, the littoral zone is devoid of vegetation. The bulk of phytobenthos in the sublittoral zone consists of kelp with an admixture of red algae.

In the temperate zone along the American and European coasts of the North Atlantic, rapid development of phytobenthos is characteristic. Brown algae (fucus and ascophyllum) predominate in the littoral zone. In the sublittoral zone they are replaced by species of kelp, alaria, desmarestia and red algae (furcelaria, ahnfeltia, lithothamnion, rhodomenia, etc.). Zostera is common on soft soils. In the temperate and cold zones of the Southern Hemisphere, brown algae, in particular kelp, predominate. In the tropical zone, in the littoral zone and in the upper horizons of the sublittoral zone, due to strong heating and intense insolation, vegetation is almost absent. Between 20 and 40° N. w. and 30 and 60° W. d. in Atlantic Ocean The Sargasso Sea is located, characterized by the constant presence of a mass of floating brown algae - sargassum. Phytoplankton, unlike phytobenthos, develops throughout the entire ocean area in the upper 100-meter layer, but reaches its highest concentration in the upper 40-50-meter layer. Phytoplankton consists of small unicellular algae (diatoms, peridines, blue-greens, flint-flagellates, coccolithines).

The mass of phytoplankton ranges from 1 to 100 mg/m3, and in high latitudes (50−60°) of the Northern and Southern Hemispheres during the period of mass development (“blooming”) reaches 10 g/m3 or more. In the cold and temperate zones of the northern and southern parts Atlantic Ocean Diatoms predominate, making up the bulk of phytoplankton. The coastal areas of the North Atlantic are characterized by the massive development of pheocystis (from golden algae) in the spring. Various species of coccolithina and the blue-green algae Trichodesmium are widespread in the tropics. The greatest quantitative development of phytoplankton is in high latitudes ocean observed in summer during the period of the most intense insolation. The temperate region is characterized by two peaks in the development of phytoplankton. Spring “blooming” is characterized by maximum biomass. During the autumn “blooming” the biomass is significantly lower than in the spring. In the tropical region, phytoplankton development occurs all year round, but the biomass is low throughout the year. Flora of the tropical region Atlantic Ocean characterized by greater qualitative diversity, but less quantitative development than the flora of the temperate and cold zones.

Animal organisms inhabit the entire water column Atlantic Ocean The diversity of fauna increases towards the tropics. In cold and temperate zones it numbers thousands of species, in tropical zones - tens of thousands. Cold and temperate zones are characterized by: mammals - whales and pinnipeds, fish - herring, cod, perch and flounder; in zooplankton there is a sharp predominance of copepods and sometimes pteropods. There is great similarity between the faunas of the temperate zones of both hemispheres. At least 100 species of animals are bipolar, that is, they are characteristic of cold and temperate zones and are absent in the tropics. These include seals, fur seals, whales, sprat, sardines, anchovies, and many invertebrates, including mussels. For tropical zones Atlantic Ocean Characteristic: sperm whale, sea turtles, crustaceans, sharks, flying fish, crabs, coral polyps, scyphoid jellyfish, siphonophores, radiolarians. The fauna of the Sargasso Sea is unique. Both free-swimming animals (mackerel, flying fish, pipefish, crabs, etc.) and those attached to algae (anemones, bryozoans) live here. Deep sea fauna ocean is richly represented by sponges, corals, echinoderms, crustaceans, fish, etc. This fauna is distinguished as an independent Atlantic deep-sea region.

In relation to the waters of the Atlantic Ocean at the level of physical-geographical zones, the following divisions are distinguished. The northwestern part of the ocean adjacent to Labrador and Greenland, characterized by rather harsh natural conditions, is classified as the Northern Subpolar Belt. To the south is the Northern Temperate Zone, which, thanks to the North Atlantic Current in the northeastern part of the ocean, extends far beyond the Arctic Circle, into the Arctic Ocean. The narrow Northern Subtropical zone is distinguished primarily by increased salinity and high water temperature; life here is much poorer than in more northern zones. The Northern Tropical Zone is characterized by a rich organic world within the neritic zone of the Caribbean Sea and very sparse in areas of the open ocean. The equatorial belt is distinguished by the constancy of temperature conditions, abundant precipitation and the general richness of the organic world. In the southern part of the ocean there are the southern tropical, subtropical and temperate zones, generally similar to the zones of the same name in the Northern Hemisphere. Only the boundaries of the Southern Tropical and Southern Subtropical belts in the western part of the ocean lie to the south, and in the eastern part, to the north of the corresponding latitudes, which is explained by the influence of the warm Brazilian (in the west) and cold Benguela (in the east) currents. The southern border of the Southern Temperate Zone is leveled out and follows in full accordance with the parallels, as well as the southern border of the Southern Subtropical Belt. The entire series of natural belts on the surface of the Atlantic Ocean ends with the South Polar Belt (there is no polar belt in the North Atlantic; it covers only the spaces of the Arctic Ocean). The South Polar, or Antarctic, belt is distinguished by the most severe natural conditions, ice cover, and is significantly less populated than the Subantarctic belt that borders it to the north.

Differentiation into latitudinal zones on the ocean floor is less pronounced than in the Indian and Pacific oceans.

The second largest ocean is the Atlantic. The ocean surface underwater was formed in different periods of time. The formation of the ocean began in the Mesozoic era, when a supercontinent split into several continents, which moved and as a result formed the primary oceanic lithosphere. Further, the formation of islands and continents occurred, which contributed to changes in the coastline and area of ​​the Atlantic Ocean. Over the past 40 million years, the ocean basin has opened along one rift axis, which continues to this day, since the plates move annually at a certain speed.

History of the study of the Atlantic Ocean

The Atlantic Ocean has been explored by people since ancient times. The most important trade routes of the ancient Greeks and Carthaginians, Phoenicians and Romans passed through it. In the Middle Ages, the Normans swam to the shores of Greenland, although there are sources confirming that they completely swam across the ocean and reached the shores of North America.

During the era of great geographical discoveries, expeditions crossed the ocean:

• B. Diasha;
• H. Columba;
• J. Cabot;
• Vasco da Gama;
• F. Magellan.

Initially, it was believed that the sailors crossed the ocean and discovered a new route to India, but much later it turned out that this was New Earth. The development of the northern shores of the Atlantic lasted in the sixteenth and seventeenth centuries, maps were compiled, and the process of collecting information about the water area, climatic features, directions and speed of ocean currents was underway.

In the eighteenth and nineteenth centuries, significant development and study of the Atlantic Ocean belonged to G. Alice, J. Cook, I. Krusenstern, E. Lentz, J. Ross. They studied the temperature regime of the water and plotted the contours of the shores, studied the ocean depths and bottom features.

From the twentieth century to the present day, fundamental research has been carried out in the Atlantic Ocean. This is an oceanographic study, using special devices that make it possible to study not only the water regime of the water area, but also the bottom topography, underwater flora and fauna. In addition, it is studying how the ocean climate affects the weather of the continents.

Thus, the Atlantic Ocean is the most important ecosystem of our planet, part of the World Ocean. It needs to be studied because it has a huge impact on the environment, and the amazing natural world opens up in the depths of the ocean.