Water resources in the Atlantic Ocean. Organic world of the Atlantic Ocean

Some areas of the Atlantic shelf are rich in coal. The largest underwater coal mining is carried out by Great Britain. The largest exploited Nor Tumberland-Derham field with reserves of about 550 million tons is located on the north-east coast of England. Coal deposits have been explored in the shelf zone northeast of Cape Breton Island. However, in the economy, underwater coal is of less importance than offshore oil and gas fields. The main supplier of monazite to the world market is Brazil. The USA is also a leading producer of concentrates of ilmenite, rutile and zircon (placers of these metals are almost ubiquitous on the North American shelf - from California to Alaska). Of significant interest are the cassiterite placers off the coast of Australia, off the Cornwall peninsula (Great Britain), and in Brittany (France). The largest accumulations of ferruginous sands in terms of reserves are located in Canada. Ferrous sands are also mined in New Zealand. Placer gold in coastal-marine sediments has been discovered on the western shores of the United States and Canada.

The main deposits of coastal-marine diamondiferous sands are concentrated on the southwestern coast of Africa, where they are confined to deposits of terraces, beaches and shelves to depths of 120 m. Significant marine terrace diamond placers are located in Namibia. African coastal-sea placers are promising. In the coastal zone of the shelf there are underwater deposits of iron ore. The most significant development of offshore iron ore deposits is carried out in Canada, on the east coast of Newfoundland (Wabana deposit). In addition, Canada mines iron ore in Hudson Bay.

Fig.1. Atlantic Ocean

Copper and nickel are extracted in small quantities from underwater mines (Canada - in the Hudson Bay). Tin mining is carried out on the Cornwall peninsula (England). In Turkey, on the coast of the Aegean Sea, mercury ores are mined. Sweden mines iron, copper, zinc, lead, gold and silver in the Gulf of Bothnia. Large salt sedimentary basins in the form of salt domes or strata deposits are often found on the shelf, slope, foot of continents and in deep-sea depressions (Gulf of Mexico, shelves and slopes of Western Africa, Europe). The minerals of these basins are represented by sodium, potassium and magnesite salts, and gypsum. Calculating these reserves is difficult: the volume of potassium salts alone is estimated to range from hundreds of millions of tons to 2 billion tons. There are two salt domes in operation in the Gulf of Mexico off the coast of Louisiana.

More than 2 million tons of sulfur are extracted from underwater deposits. The largest accumulation of sulfur, Grand Isle, located 10 miles off the coast of Louisiana, is exploited. Industrial reserves of phosphorites were found near the Californian and Mexican coasts, along the coastal zones South Africa, Argentina, off the coast of New Zealand. Phosphorites are mined in the California region from depths of 80-330 m, where the concentration averages 75 kg/m3.

IN Atlantic Ocean and its seas revealed a large number of offshore oil and gas fields, including one of the world's highest levels of production of these types of fuel. They are located in different areas of the ocean shelf zone. In its western part, the subsoil of the Maracaibo lagoon is distinguished by very large reserves and production volumes. Oil is extracted here from more than 4,500 wells, from which 93 million tons of “black gold” were obtained in 2006. The Gulf of Mexico is considered one of the richest offshore oil and gas regions in the world, believing that only a small portion of potential oil and gas reserves have been identified in it at present. 14,500 wells have been drilled at the bottom of the bay. In 2011, 60 million tons of oil and 120 billion m3 of gas were produced from 270 offshore fields, and in total, 590 million tons of oil and 679 billion m3 of gas were extracted here during development. The most significant of them are located off the coast of the Paraguano Peninsula, in the Gulf of Paria and off the island of Trinidad. Oil reserves here amount to tens of millions of tons.

In addition to the above-mentioned areas, three large oil and gas provinces can be traced in the western Atlantic. One of them stretches from Davis Strait to the latitude of New York. Within its boundaries, industrial oil reserves have so far been identified in Labrador and south of Newfoundland. Second oil and gas province stretches along the coast of Brazil from Cape Calcañar in the north to Rio de Janeiro in the south. 25 deposits have already been discovered here. The third province occupies the coastal areas of Argentina from the Gulf of San Jorge to the Strait of Magellan. Only small deposits have been discovered in it, which are not yet profitable for offshore development.

In the shelf zone of the eastern coast of the Atlantic, oil shows were discovered south of Scotland and Ireland, off the coast of Portugal, in the Bay of Biscay. A large oil and gas bearing area is located near the African continent. About 8 million tons come from oil fields concentrated near Angola.

Very significant oil and gas resources are concentrated in the depths of some seas of the Atlantic Ocean. Among them, the most important place is occupied by the North Sea, which has no equal in the pace of development of underwater oil and gas fields. Significant underwater oil and gas deposits have been explored in the Mediterranean Sea, where 10 oil and 17 offshore gas fields are currently operating. Significant volumes of oil are extracted from fields located off the coasts of Greece and Tunisia. Gas is being developed in the Gulf of Sidra (Bol. Sirte, Libya), off the Italian coast of the Adriatic Sea. In the future, the subsoil of the Mediterranean Sea should produce at least 20 million tons of oil per year.

Some areas of the Atlantic shelf are rich in coal. The largest underwater coal mining is carried out by Great Britain. The largest exploited North Tumberland-Derham field with reserves of about 550 million tons is located on the north-east coast of England. Coal deposits have been explored in the shelf zone northeast of Cape Breton Island. However, in the economy, underwater coal is of less importance than offshore oil and gas fields. The main supplier of monazite to the world market is Brazil. The USA is also a leading producer of ilmenite, rutile and zircon concentrates (placers of these metals are almost ubiquitous on the shelf North America- from California to Alaska). Of significant interest are the cassiterite placers off the coast of Australia, off the Cornwall peninsula (Great Britain), and in Brittany (France). The largest accumulations of ferruginous sands in terms of reserves are located in Canada. Ferrous sands are also mined in New Zealand. Placer gold in coastal-marine sediments has been discovered on the western shores of the United States and Canada.

The main deposits of coastal-marine diamondiferous sands are concentrated on the southwestern coast of Africa, where they are confined to deposits of terraces, beaches and shelves to depths of 120 m. Significant marine terrace diamond placers are located in Namibia. African coastal-sea placers are promising.

In the coastal zone of the shelf there are underwater deposits of iron ore. The most significant development of offshore iron ore deposits is carried out in Canada, on the east coast of Newfoundland (Wabana deposit). In addition, Canada mines iron ore in Hudson Bay.

Copper and nickel are extracted in small quantities from underwater mines (Canada - in the Hudson Bay). Tin mining is carried out on the Cornwall peninsula (England). In Turkey, on the coast of the Aegean Sea, mercury ores are mined. Sweden mines iron, copper, zinc, lead, gold and silver in the Gulf of Bothnia.

Large salt sedimentary basins in the form of salt domes or strata deposits are often found on the shelf, slope, foot of continents and in deep-sea depressions (Gulf of Mexico, shelves and slopes of Western Africa, Europe). The minerals of these basins are represented by sodium, potassium and magnesite salts, and gypsum. Calculating these reserves is difficult: the volume of potassium salts alone is estimated to range from hundreds of millions of tons to 2 billion tons. There are two salt domes in operation in the Gulf of Mexico off the coast of Louisiana.

More than 2 million tons of sulfur are extracted from underwater deposits. The largest accumulation of sulfur, Grand Isle, located 10 miles off the coast of Louisiana, is exploited. Industrial reserves of phosphorites have been found near the Californian and Mexican coasts, along the coastal zones of South Africa, Argentina, and off the coast of New Zealand. Phosphorites are mined in the California region from depths of 80-330 m, where the concentration averages 75 kg/m3.

A large number of offshore oil and gas fields have been identified in the Atlantic Ocean and its seas, including some of the highest levels of production of these fuels in the world. They are located in different areas of the ocean shelf zone. In its western part, the subsoil of the Maracaibo lagoon is distinguished by very large reserves and production volumes. Oil is extracted here from more than 4,500 wells, from which 93 million tons of “black gold” were obtained in 2006. The Gulf of Mexico is considered one of the richest offshore oil and gas regions in the world, believing that only a small portion of potential oil and gas reserves have been identified in it at present. 14,500 wells have been drilled at the bottom of the bay. In 2011, 60 million tons of oil and 120 billion m3 of gas were produced from 270 offshore fields, and in total, 590 million tons of oil and 679 billion m3 of gas were extracted here during development. The most significant of them are located off the coast of the Paraguano Peninsula, in the Gulf of Paria and off the island of Trinidad. Oil reserves here amount to tens of millions of tons.

In addition to the above-mentioned areas, three large oil and gas provinces can be traced in the western Atlantic. One of them stretches from Davis Strait to the latitude of New York. Within its boundaries, industrial oil reserves have so far been identified in Labrador and south of Newfoundland. The second oil and gas province stretches along the coast of Brazil from Cape Calcañar in the north to Rio de Janeiro in the south. 25 deposits have already been discovered here. The third province occupies the coastal areas of Argentina from the Gulf of San Jorge to the Strait of Magellan. Only small deposits have been discovered in it, which are not yet profitable for offshore development.

In the shelf zone of the eastern coast of the Atlantic, oil shows were discovered south of Scotland and Ireland, off the coast of Portugal, in the Bay of Biscay. A large oil and gas bearing area is located near the African continent. About 8 million tons come from oil fields concentrated near Angola.

Very significant oil and gas resources are concentrated in the depths of some seas of the Atlantic Ocean. Among them, the most important place is occupied by the North Sea, which has no equal in the pace of development of underwater oil and gas fields. Significant underwater oil and gas deposits have been explored in the Mediterranean Sea, where 10 oil and 17 offshore gas fields are currently operating. Significant volumes of oil are extracted from fields located off the coasts of Greece and Tunisia. Gas is being developed in the Gulf of Sidra (Bol. Sirte, Libya), off the Italian coast of the Adriatic Sea. In the future, the subsoil of the Mediterranean Sea should produce at least 20 million tons of oil per year.

The Atlantic Ocean is the second largest ocean on Earth after the Pacific. Like the Pacific, it extends from subarctic latitudes to the subantarctic, that is, from the underwater threshold separating it from the Arctic Ocean in the north to the shores of Antarctica in the south. In the east, the Atlantic Ocean washes the shores of Eurasia and Africa, in the west - North and South America(Fig. 3).

Not only in the geographical location of the largest oceans on Earth, but also in many of their features - climate formation, hydrological regime, etc. - there is much in common. However, there are also significant differences associated with big difference size: in terms of surface area (91.6 million km2) and volume (about 330 million km3), the Atlantic Ocean is approximately half the size of the Pacific Ocean.

The narrowest part of the Atlantic Ocean occurs at the same latitudes where the Pacific Ocean reaches its greatest extent. The Atlantic Ocean differs from the Pacific Ocean in the wider development of its shelf, especially in the area of ​​Newfoundland and off the southeastern coast of South America, as well as in the Bay of Biscay, the North Sea and the British Isles. The Atlantic is also characterized by a large number mainland islands and island archipelagos that relatively recently lost contact with the continents (Newfoundland, Antilles, Falklands, British, etc.). Islands of volcanic origin (Canary, Azores, St. Helena, etc.) are few in number in comparison with the Pacific Ocean.

The shores of the Atlantic Ocean are most severely dissected north of the equator. There, going deep into the land of North America and Eurasia, are the most significant seas related to it: the Gulf of Mexico (actually a semi-enclosed sea between the Florida and Yucatan peninsulas and the island of Cuba), the Caribbean, North, Baltic, as well as the intercontinental Mediterranean Sea, connected by straits with the Marmara, Black and Azov inland seas. North of the equator, off the coast of Africa, lies the vast Gulf of Guinea, wide open to the ocean.

The formation of the modern depression of the Atlantic Ocean began approximately 200 million years ago, in the Triassic, with the opening of a rift on the site of the future Tethys Ocean and the division of the Pangea continent into Laurasia and Gondwana (see map of continental drift). Subsequently, Gondwana was divided into two parts - African-South American and Australian-Antarctic and the formation of the western part of the Indian Ocean; the formation of a continental rift between Africa and South America and their movement to the north and northwest; creation of a new ocean floor between North America and Eurasia. Only on the site of the North Atlantic, on the border with the North Arctic Ocean, the connection between the two continents remained until the end of the Paleogene.

At the end of the Mesozoic and Paleogene, as a result of the movement towards Eurasia of the most stable part of the broken Gondwana - the African lithospheric plate, as well as the Hindustan block, the closure of Tethys occurred. The Mediterranean (Alpine-Himalayan) orogenic belt and its western continuation, the Antillean-Caribbean fold system, were formed. Intercontinental basin of the Mediterranean Sea, Marmara, Black and Sea of ​​Azov, as well as the seas and bays of the northern Indian Ocean, which were discussed in the corresponding section, should be considered as fragments of the closed ancient Tethys Ocean. The same “remnant” of Tethys in the west is the Caribbean Sea with the adjacent land and part of the Gulf of Mexico.

The final formation of the Atlantic Ocean basin and the surrounding continents occurred in the Cenozoic era.

Along the entire ocean from north to south, occupying its axial part, runs the Mid-Atlantic Ridge, separating the continental oceanic ridges located on both sides. lithospheric plates: North American, Caribbean and South American - in the west and Eurasian and African - in the east. The Mid-Atlantic Ridge has the most pronounced features of the mid-ocean ridges of the World Ocean. The study of this particular ridge laid the foundation for the study of the global system of mid-ocean ridges as a whole.

From the border with the Arctic Ocean off the coast of Greenland to the connection with the African-Antarctic Ridge at Bouvet Island in the south, the Mid-Atlantic Ridge has a length of over 18 thousand km and a width of 1 thousand km. It accounts for approximately a third of the area of ​​the entire ocean floor. A system of deep longitudinal faults (rifts) runs along the arch of the ridge; transverse (transform) faults cross it along its entire length. The areas of the most active manifestation of ancient and modern, underwater and above-water, rift volcanism in the northern part of the Mid-Atlantic Ridge are the Azores Islands at 40° N latitude. and the unique, largest volcanic island on Earth - Iceland on the border with the Arctic Ocean.

The island of Iceland is located directly on the Mid-Atlantic Ridge; in the middle it is crossed by a rift system - the “spreading axis”, bifurcating in the southeast. Almost all the extinct and active volcanoes of Iceland rise along this axis, the emergence of which continues to this day. Iceland can be considered as a “product” of the expansion of the ocean floor, which has been going on for 14-15 million years (H. Rast, 1980). Both halves of the island are moving apart from the rift zone, one, together with the Eurasian plate, to the east, the other, together with the North American plate, to the west. The movement speed is 1 - 5 cm per year.

South of the equator, the Mid-Atlantic Ridge retains its integrity and typical features, but differs from the northern part in less tectonic activity. The centers of rift volcanism here are the islands of Ascension, St. Helena, and Tristan da Cunha.

On both sides of the Mid-Atlantic Ridge lies an ocean floor composed of basaltic crust and thick layers of Meso-Cenozoic sediments. In the structure of the surface of the bed, as in the Pacific Ocean, there are numerous deep-sea basins (more than 5000 m, and the North American Basin is even more than 7000 m deep), separated from each other by underwater rises and ridges. The basins of the American side of the Atlantic are Newfoundland, North American, Guiana, Brazil and Argentina; from Eurasia and Africa - Western European, Canary, Angolan and Cape.

The largest rise of the Atlantic Ocean floor is the Bermuda Plateau within the North American Basin. Basically consisting of oceanic basalts, it is covered by a two-kilometer layer of sediment. On its surface, located at a depth of 4000 m, volcanoes rise, topped with coral structures, forming the Bermuda archipelago. Opposite the coast of South America, between the Brazilian and Argentine basins, is the Rio Grande plateau, also covered by thick strata sedimentary rocks and topped with underwater volcanoes.

In the eastern part of the ocean floor, the Guinea Rise along the lateral rift of the median ridge should be noted. This fault emerges onto the mainland in the Gulf of Guinea region in the form of a continental rift, to which the active Cameroon volcano is confined. Even further south, between the Angola and Cape basins, the underwater blocky Whale Ridge reaches the shores of South-West Africa.

In the main floor of the Atlantic Ocean it borders directly on the underwater margins of the continents. The transition zone is much less developed than in the Pacific Ocean and is represented by only three regions. Two of them - the Mediterranean Sea with adjacent land areas and the Antilles-Caribbean region, located between North and South America - are fragments of the Tethys Ocean, which closed towards the end of the Paleogene, separated from each other during the opening of the middle part of the Atlantic Ocean. Therefore, they have a lot in common in features geological structure bottom, the nature of the relief of underwater and surface mountain structures, types of manifestation of volcanic activity.

The depression of the Mediterranean Sea is separated from the deep basins of the ocean by the Gibraltar threshold with a depth of only 338 m. The smallest width of the Strait of Gibraltar is only 14 km. In the first half of the Neogene, the Strait of Gibraltar did not exist at all, and long time The Mediterranean Sea was a closed basin, isolated from the ocean and the seas that continued it in the east. The connection was restored only at the beginning of the Quaternary period. Peninsulas and groups of mainland islands formed by structures of different ages, the sea is divided into a number of basins, the structure of which is dominated by Earth's crust suboceanic type. At the same time, a significant part of the bottom of the Mediterranean Sea, belonging to the continental foot and shelf, is composed of continental crust. This is primarily the southern and southeastern parts of its depressions. Continental crust is also characteristic of some deep-sea basins.

In the Ionian Sea, between the Central Mediterranean, Cretan and Levantine basins, the Central Mediterranean Shaft stretches, to which the Hellenic deep-sea trench adjoins with the maximum depth of the entire Mediterranean Sea (5121 m), bordered from the northeast by the arc of the Ionian Islands.

The Mediterranean basin is characterized by seismicity and explosive-effusive volcanism, confined mainly to its central part, i.e. to the subduction zone in the area of ​​the Bay of Naples and adjacent land areas. Along with the most active volcanoes in Europe (Vesuvius, Etna, Stromboli), there are many objects there that indicate manifestations of paleovolcanism and active volcanic activity during historical time. The features of the Mediterranean noted here allow us to consider it “as a transitional region in the most advanced stage of development” (O. K. Leontiev, 1982). Fragments of the closed Tethys are also located to the east of the Black and Azov Seas and the Caspian Lake-Sea. The nature features of these reservoirs are discussed in the relevant sections of the regional review of Eurasia.

The second transition region of the Atlantic Ocean is located in its western part, between North and South America, and roughly corresponds to western sector Ocean Tethys. It consists of two semi-enclosed seas, separated from each other and from the ocean floor by peninsulas and island arcs of continental and volcanic origin. The Gulf of Mexico is a depression of Mesozoic age with a depth of more than 4000 m in the central part, surrounded by a wide strip of shelf from the mainland and the Florida and Yucatan peninsulas. Within the adjacent land, on the shelf and adjacent parts of the bay, the largest reserves of oil and natural gas. This oil and gas basin Gulf of Mexico, which is genetically and economic importance comparable to the oil and gas basin of the Persian Gulf. The Caribbean Sea, separated from the ocean by the arc of the Antilles, was formed in the Neogene. His maximum depths exceed 7000 m. On the ocean side, the Antillean-Caribbean transition region is limited by the deep-sea trench of Puerto Rico, the greatest depth of which (8742 m) is at the same time the maximum for the entire Atlantic Ocean. By analogy with Mediterranean Sea this area is sometimes called the American Mediterranean.

The third transitional region related to the Atlantic Ocean, the Scotia Sea (Scotia), is located between South America and the Antarctic Peninsula, on both sides of 60° S, i.e. actually in Antarctic waters. In the east, this area is separated from the ocean floor by the South Sandwich deep-sea trench (8325 m) and an arc of volcanic islands of the same name, perched on an underwater rise. The bottom of the Scotia Sea is composed of suboceanic type crust, giving way to oceanic bed crust in the west Pacific Ocean. The surrounding groups of islands (South Georgia, etc.) are of continental origin.

Vast areas of the shelf, which are also characteristic feature Atlantic Ocean, exist on both its Eurasian and American flanks. This is the result of relatively recent subsidence and flooding of the coastal plains. Even in the first half of the Cenozoic, North America extended almost to the pole and connected with Eurasia in the northwest and northeast. The formation of the Atlantic shelf off the coast of North America should obviously be attributed to the end of the Neogene, and off the coast of Europe - to the Quaternary period. This is associated with the existence of “land” forms in its relief - erosional hollows, dune hills, etc., and in more northern areas - traces of glacial abrasion and accumulation.

The similarities have already been noted above geographical location The Atlantic and Pacific oceans, which cannot but influence the peculiarities of climate formation and hydrological conditions of each of them. Approximately the same length from north to south, between the subpolar latitudes of both hemispheres, much big sizes and the massiveness of the land bordering the oceans in the northern hemisphere compared to the southern one, a relatively weak connection and limited opportunities water exchange with the Arctic Ocean and openness towards other oceans and the Antarctic basin in the south - all these features of both oceans determine the similarity between them in the distribution of centers of atmospheric action, the direction of winds, and temperature conditions surface waters and distribution of precipitation.

At the same time, it should be noted that the Pacific Ocean is almost twice as large in surface area as the Atlantic Ocean and its widest part is in the intertropical space, where it has a connection with the warmest part of the Indian Ocean through the interisland seas and straits of Southeast Asia. The Atlantic Ocean in subequatorial latitudes has the smallest width; it is limited to the east and west by massive land masses of Africa and South America. These features, as well as differences in the age and structure of the ocean basins themselves, create the geographical individuality of each of them, with individual features being more characteristic of the northern parts of the oceans, while in the southern hemisphere the similarities between them are much more pronounced.

The main pressure systems over the Atlantic Ocean, which determine the meteorological situation throughout the year, are the equatorial depression, which, as in the Pacific Ocean, is somewhat expanded towards the summer hemisphere, as well as quasi-stationary subtropical high pressure areas, along the periphery of which towards the equatorial Depressions are driven by trade winds - northeasterly in the northern hemisphere and southeasterly in the southern hemisphere.

In the southern hemisphere, where the ocean surface is only relatively small spaces interrupted by land, all the main pressure systems are extended along the equator in the form of sublatitudinal belts, separated by frontal zones, and during the year they only slightly shift following the sun towards the summer hemisphere.

In the winter of the southern hemisphere, the southeast trade wind penetrates to the equator and slightly further north, towards the Gulf of Guinea and northern South America. The main precipitation at this time falls in the northern hemisphere, and dry weather prevails on both sides of the Southern Tropic. South of 40° S. Western transport is active, winds blow, often reaching gale force, thick clouds and fogs are observed, and heavy precipitation falls in the form of rain and snow. These are the “roaring forties” latitudes, which have already been discussed in the sections devoted to the nature of the Pacific and Indian oceans. From Antarctica, in high latitudes, southeastern and eastern winds blow, with which icebergs and sea ice are blown to the north.

In the warm half of the year, the main directions of air flow remain the same, but the equatorial trough expands to the south, the southeast trade wind intensifies, rushing into an area of ​​​​low pressure over South America, and precipitation falls along its eastern coast. Western winds in temperate and high latitudes remain the dominant atmospheric process.

Natural conditions in the subtropical and temperate latitudes of the North Atlantic are significantly different from those characteristic of the southern part of the ocean. This is due both to the characteristics of the water area itself and to the size of the land bordering it, the temperature and air pressure above which change sharply throughout the year. The most significant contrasts in pressure and temperature are created in winter, when over ice-covered Greenland, North America and internal parts Eurasia, due to cooling, centers of high pressure are formed and the temperature is not only over land, but also over clogged with ice interisland waters of the Canadian Arctic Archipelago can be very low. The ocean itself, with the exception of the coastal northwestern part, even in February maintains a surface water temperature of 5 to 10 °C. This is due to the influx of warm waters from the south into the northeastern part of the Atlantic and the lack of cold water from the Arctic Ocean.

In the north of the Atlantic Ocean, a closed area of ​​​​low pressure is formed in winter - the Icelandic, or North Atlantic, minimum. Its interaction with the Azores (North Atlantic) maximum, located at the 30th parallel, creates a predominant westerly wind flow over the North Atlantic, carrying a relatively moisture-unstable flow from the ocean to the Eurasian continent. warm air. This atmospheric process is accompanied by precipitation in the form of rain and snow at positive temperatures. A similar situation applies to the ocean area south of 40° N. and in the Mediterranean, where it rains at this time.

IN summer season in the northern hemisphere, the high pressure area persists only over the Greenland ice sheet; centers are established over the continents low pressure, The Icelandic low is weakening. Western transport remains the main circulation process in temperate and high latitudes, but it is not as intense as in winter. The Azores High intensifies and expands, and most of the North Atlantic, including the Mediterranean Sea, is under the influence of tropical air masses and does not receive precipitation. Only off the coast of North America, where moisture-unstable air enters along the periphery of the Azores High, does monsoon-type precipitation occur, although this process is not at all as pronounced as on the Pacific coast of Eurasia.

In summer and especially in autumn, tropical hurricanes arise over the Atlantic Ocean between the northern tropic and the equator (as in the Pacific and Indian oceans at these latitudes), which sweep over the Caribbean Sea, the Gulf of Mexico, Florida with enormous destructive force, and sometimes penetrate far to the north, up to 40° N

Due to the observed last years Due to high solar activity off the coast of the Atlantic Ocean, the frequency of tropical hurricanes has increased significantly. In 2005, three hurricanes hit the southern coast of the United States - Katrina, Rita and Emily, the first of which caused enormous damage to the city of New Orleans.

The system of surface currents in the Atlantic Ocean generally follows their circulation in the Pacific Ocean.

In the equatorial latitudes there are two trade wind currents - the Northern Trade Wind and the Southern Trade Wind, moving from east to west. Between them, the Intertrade Countercurrent moves east. The Northern Trade Wind Current passes near 20° N latitude. and off the coast of North America it gradually deviates to the north. The Southern Trade Wind Current, passing south of the equator from the coast of Africa to the west, reaches the eastern protrusion of the South American continent and at Cape Cabo Branco it divides into two branches running along the coast of South America. Its northern branch (Guiana Current) reaches the Gulf of Mexico and, together with the North Trade Wind Current, takes part in the formation of the system of warm currents of the North Atlantic. The southern branch (Brazil Current) reaches 40° S, where it meets a branch of the circumpolar current of the Western Winds - the cold Falkland Current. Another branch of the Western Winds current, carrying relatively cold waters to the north, enters the Atlantic Ocean off the southwestern coast of Africa. This Benguela Current is an analogue of the Peruvian Current of the Pacific Ocean. Its influence can be traced almost to the equator, where it flows into the South Trade Wind Current, closing the southern Atlantic gyre and significantly reducing the temperature of surface waters off the coast of Africa.

The overall pattern of surface currents in the North Atlantic is much more complex than in the southern part of the ocean, and also differs significantly from the system of currents in the northern part of the Pacific Ocean.

A branch of the North Trade Wind Current, strengthened by the Guiana Current, penetrates through the Caribbean Sea and the Yucatan Strait into the Gulf of Mexico, causing a significant increase in water levels there compared to the ocean. As a result, a powerful waste current arises, which, rounding Cuba, emerges through the Strait of Florida into the ocean called the Gulf Stream (“stream from the gulf”). This is how the greatest system of warm surface currents in the World Ocean originates off the southeastern coast of North America.

Gulf Stream at 30°N. and 79°W merges with the warm Antilles Current, which is a continuation of the North Trade Wind Current. Next, the Gulf Stream passes along the edge of the continental shelf to approximately 36°N. At Cape Hatteras, deviating under the influence of the Earth's rotation, it turns east, skirting the edge of the Great Newfoundland Bank, and goes to the shores of Europe under the name of the North Atlantic Current, or “Gulf Stream Drift”.

When leaving the Strait of Florida, the width of the Gulf Stream reaches 75 km, depth - 700 m, and current speed - from 6 to 30 km/h. The average surface water temperature is 26 °C. After merging with the Antilles Current, the width of the Gulf Stream increases 3 times, and the water flow is 82 million m3/s, i.e. 60 times higher than the flow of all rivers on the globe.

North Atlantic Current at 50°N. and 20°W is divided into three branches. The northern one (Irminger Current) goes to the southern and western shores of Iceland, and then goes around the southern coast of Greenland. The main middle branch continues to move northeast, towards the British Isles and the Scandinavian Peninsula, and goes into the Arctic Ocean called the Norwegian Current. The width of its flow north of the British Isles reaches 185 km, depth - 500 m, flow speed - from 9 to 12 km per day. The surface water temperature is 7... 8 °C in winter and 11... 13 °C in summer, which is on average 10 °C higher than at the same latitude in the western part of the ocean. The third, southern, branch penetrates the Bay of Biscay and continues south along the Iberian Peninsula and the northeastern coast of Africa in the form of the cold Canary Current. Flowing into the North Trade Wind Current, it closes the subtropical gyre of the North Atlantic.

The northwestern part of the Atlantic Ocean is mainly influenced by cold waters coming from the Arctic, and different hydrological conditions develop there. In the area of ​​the island of Newfoundland, the cold waters of the Labrador Current move towards the Gulf Stream, pushing aside warm waters Gulf Stream from the northeastern coast of North America. In winter, the waters of the Labrador Current are 5...8 °C colder than the Gulf Stream; all year round their temperature does not exceed 10 °C, they form the so-called “ cold wall" The convergence of warm and cold waters promotes the development of microorganisms in top layer water and therefore an abundance of fish. The Great Newfoundland Bank is especially famous in this regard, where cod, herring, and salmon are caught.

To approximately 43°N. The Labrador Current carries icebergs and sea ice, which, combined with the fogs characteristic of this part of the ocean, pose a great danger to shipping. A tragic illustration is the disaster of the Titanic, which sank in 1912 800 km southeast of Newfoundland.

The water temperature on the surface of the Atlantic Ocean, as in the Pacific, is generally lower in the southern hemisphere than in the northern. Even at 60° N latitude. (with the exception of the northwestern regions), the temperature of surface waters fluctuates throughout the year from 6 to 10 °C. In the southern hemisphere at the same latitude it is close to 0 °C and in the eastern part it is lower than in the western.

The warmest surface waters of the Atlantic (26...28 °C) are confined to the zone between the equator and the Northern Tropic. But even these maximum values ​​do not reach the values ​​observed at the same latitudes in the Pacific and Indian Oceans.

The salinity of the surface waters of the Atlantic Ocean is much more varied than in other oceans. Largest values(36-37%o is the maximum value for the open part of the World Ocean) are typical for subtropical regions with low annual precipitation and strong evaporation. High salinity is also associated with the influx of salt water from the Mediterranean Sea through the shallow Strait of Gibraltar. On the other side, large plots The water surface has average oceanic and even low salinity. This is due to large amounts of atmospheric precipitation (in equatorial regions) and the desalination effect of large rivers (Amazon, La Plata, Orinoco, Congo, etc.). In high latitudes, salinity decreases to 32-34%o, especially in summer time, is explained by the melting of icebergs and floating sea ice.

The structural features of the North Atlantic basin, the circulation of the atmosphere and surface waters in subtropical latitudes determined the existence here of a unique natural formation called the Sargasso Sea. This is a section of the Atlantic Ocean between 21 and 36 latitudes. and 40 and 70° W. The Sargasso Sea is “boundless, but not limitless.” Its peculiar boundaries can be considered the currents: the North Trade Wind in the south, the Antilles in the southwest, the Gulf Stream in the west, the North Atlantic in the north and the Canary in the east. These boundaries are fluid, so the area of ​​the Sargasso Sea fluctuates between 6 and 7 million km2. Its position roughly corresponds to the central part of the Azores baric maximum. Within the Sargasso Sea are the volcanic and coral islands of the Bermuda archipelago.

The main features of the surface waters of the Sargasso Sea in comparison with the surrounding waters are their low mobility, poor development of plankton and the highest transparency in the World Ocean, especially in summer (to a depth of 66 m). High temperatures and salinity are also characteristic.

The sea gets its name from floating brown algae belonging to the genus Sargassum. Algae are carried by currents, and the area where they accumulate coincides with the space between the Gulf Stream and the Azores. Average weight there are about 10 million tons of them in the Sargasso Sea. There are such numbers of them nowhere else in the World Ocean. European and American eels spawn in the waters of the Sargasso Sea at depths of 500-600 m. The larvae of these valuable commercial fish are then transported by currents to the mouths of large rivers, and the adults return to spawn in the Sargasso Sea. To complete the complete life cycle they take several years.

The similarities noted above between the Atlantic and Pacific oceans are also manifested in their features. organic world. This is quite natural, since both oceans, stretching between the northern and southern polar circles and forming a continuous water surface in the south, together with the Indian Ocean, reflect the main features of their nature, including the organic world common features World ocean.

Like the entire World Ocean, the Atlantic is characterized by an abundance of biomass with a relative poverty of the species composition of the organic world in temperate and high latitudes and much greater species diversity in the intertropical space and subtropics.

The temperate and subantarctic zones of the southern hemisphere are included in the Antarctic biogeographic region.

The Atlantic Ocean, as well as other oceans in these latitudes, is characterized by the presence of large mammals in its fauna - fur seals, several species of true seals, and cetaceans. The latter are represented here most fully compared to other parts of the World Ocean, but in the middle of the last century they were severely exterminated. Among fishes, the endemic families of nototheniids and white-blooded pike are characteristic of the South Atlantic. The number of plankton species is small, but its biomass, especially in temperate latitudes, is very significant. Zooplankton includes copepods (krill) and pteropods, while phytoplankton is dominated by diatoms. The corresponding latitudes of the northern part of the Atlantic Ocean (North Atlantic biogeographical region) are characterized by the presence in the organic world of the same groups of living organisms as in the southern hemisphere, but they are represented by other species and even genera. And compared with the same latitudes of the Pacific Ocean, the North Atlantic is distinguished by a greater species diversity. This is especially true for fish and some mammals.

Many areas of the North Atlantic have long been and continue to be places of intense fishing. Cod, herring, halibut, sea bass, and sprat are caught on banks off the coast of North America, in the North and Baltic seas. Since ancient times, mammals have been hunted in the Atlantic Ocean, especially seals, whales and other marine animals. This has led to a severe depletion of the Atlantic's fishing resources compared to the Pacific and Indian oceans.

As in other parts of the World Ocean, the greatest diversity of life forms and the maximum species richness of the organic world is observed in the tropical part of the Atlantic Ocean. The plankton contains numerous foraminifera, radiolarians, and copepods. Nekton is characterized by sea turtles, squids, sharks, and flying fish; Among commercial fish species, tuna, sardines, mackerel are abundant, and in zones of cold currents - anchovies. Among the bottom forms are various algae: green, red, brown (sargassum already mentioned above); Animals include octopuses and coral polyps.

But despite the relative species richness of the organic world in the tropical Atlantic Ocean, it is still less diverse than in the Pacific and even the Indian Oceans. Coral polyps are much less represented here, the distribution of which is limited mainly to the Caribbean; There are no sea snakes or many species of fish. This may be due to the fact that in subequatorial latitudes the Atlantic Ocean has the smallest width (less than 3000 km), which is incomparable with the vast expanses of the Pacific and Indian oceans.

Climate and hydrological regime of the Atlantic Ocean. Hydrological resources.

Diversity 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 four main atmospheric centers: Greenland and Antarctic max., Icelandic and Antarctic minima. 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. Greatest impact on temperature regime The Atlantic Ocean is affected not only by its large meridional extent, but also by water exchange with the Arctic Ocean, the Antarctic seas and the Mediterranean Sea. Tropical latitudes are characterized by tempera. - 20 °C. To the north and south of the tropics there are subtropical zones with more noticeable seasonal zones (from 10 °C in winter to 20 °C in summer). Frequent occurrence in the subtropical zone - tropical hurricanes. In temperate latitudes, the average temperature of the warmest month is between 10-15 °C, and the coldest month is −10 °C. Precipitation is about 1000 mm.

Surface currents. Northern Trade Wind Current(t)>Antilles(t)>Mexico. Gulf>Florida(t)>Gulf Stream>North Atlantic(t)>Canary(x)>North Trade Wind Current(t) – northern gyre.

Southern trade wind>Guiana heat. (north) and Brazilian heat. (south)>current Western winds(x)>Bengela(x)>Southern trade winds – southern gyre.

There are several tiers in the Atlantic Ocean deep sea currents. 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 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.

Salinity. 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 it is noted maximum amount precipitation, 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. 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. Floating ice in the northern hemisphere in July they reach 40°N.

Upwelling. Along the entire western coast of Africa there is a particularly powerful upwelling zone caused by wind driven water,<связан. с пассатной циркуляцией. Также это зоны у Зелёного мыса, у берегов Анголы и Конго. Эти области наиболее благоприятны для развития орг. мира.

The bottom flora of the northern part of the Atlantic is represented by brown (mainly fucoids, and in the subditorial 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 the subantarctic and antarctic In the waters, notothenia, blue 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. To tropical and subtropical corals are confined to the zones. Temperate latitudes The northern hemisphere is 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.

There are 4 biogeographical regions in the Atlantic Ocean: 1. Arctic; 2. North Atlantic; 3. Tropico-Atlantic; 4. Antarctic.

Biological resources. 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.