Describe other natural resources of the Atlantic Ocean. Natural resources of the Atlantic Ocean

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. Nevertheless, the differences are also very significant, which are associated with a large difference in size: in terms of surface area (91.6 million km2) and volume (about 330 million km3), the Atlantic Ocean is approximately half as large as 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 of mainland islands and island archipelagos that have relatively recently lost contact with the continents (Newfoundland, Antilles, Falkland, 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 at the site of the North Atlantic, on the border with the Arctic Ocean, did the connection between the two continents persist 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. The intercontinental basin of the Mediterranean Sea, the Sea of ​​Marmara, the Black and Azov, as well as the seas and gulfs of the northern part of the 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 lithospheric plates located on both sides: the North American, Caribbean and South American in the west and the 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 layers of sedimentary rocks and crowned 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 much in common in the features of the geological structure of the bottom, the nature of the relief of underwater and surface mountain structures, and the 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 for a 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 the bottom of which is dominated by suboceanic type crust. 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 the western sector of the Tethys Ocean. 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. The largest reserves of oil and natural gas are concentrated within the adjacent land, on the shelf and adjacent parts of the bay. This is the oil and gas basin of the Gulf of Mexico, which is genetically and economically 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. Its 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 the 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 crust, which in the west is replaced by oceanic crust of the Pacific Ocean bed. The surrounding groups of islands (South Georgia, etc.) are of continental origin.

Vast expanses of shelf, which are also a characteristic feature of the 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 similarity of the geographical position of the Atlantic and Pacific oceans has already been noted above, which cannot but influence the peculiarities of climate formation and hydrological conditions of each of them. Approximately the same extent from north to south, between the subpolar latitudes of both hemispheres, the much larger size and massiveness of the land bordering the oceans in the northern hemisphere compared to the southern, relatively weak connection and limited possibilities of 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, the temperature regime of surface waters and the 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 surface of the ocean is only interrupted by land in relatively small areas, 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 shift slightly 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 differ significantly 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 high pressure centers form over ice-covered Greenland, North America and the interior of Eurasia due to cooling and the temperature not only over land, but also over the ice-clogged interisland waters of the Canadian Arctic Archipelago is 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 moist-unstable relatively warm air from the ocean to the Eurasian continent. 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 the summer season of the northern hemisphere, the high pressure area remains only over the Greenland ice sheet, low pressure centers are established over the continents, and the Icelandic low weakens. 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 high solar activity observed in recent years 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 arises 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 the warm waters of the Gulf Stream away 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 a so-called “cold wall”. The convergence of warm and cold waters promotes the development of microorganisms in the upper layer of water and, consequently, the 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. The highest values ​​(36-37%o - the maximum value for the open part of the World Ocean) are characteristic of 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 hand, large areas of the water surface have 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, a decrease in salinity to 32-34%o, especially in summer, 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. Their average weight in the Sargasso Sea is about 10 million tons. 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. They take several years to complete their full life cycle.

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

Atlantic Ocean

Geographical position.The Atlantic Ocean stretches from north to south for 16 thousand km from subarctic to Antarctic latitudes. The ocean is wide in the northern and southern parts, narrowing in equatorial latitudes to 2900 km. In the north it communicates with the Arctic Ocean, and in the south it is widely connected with the Pacific and Indian Oceans. It is limited by the shores of North and South America in the west, Europe and Africa in the east, and Antarctica in the south.

The Atlantic Ocean is the second largest among the planet's oceans. The ocean coastline in the northern hemisphere is heavily dissected by numerous peninsulas and bays. There are many islands, internal and marginal seas near the continents. The Atlantic includes 13 seas, which occupy 11% of its area.

Bottom relief. Through the entire ocean (approximately at an equal distance from the coasts of the continents) passes Mid-Atlantic Ridge. The relative height of the ridge is about 2 km. Transverse faults divide it into separate segments. In the axial part of the ridge there is a giant rift valley ranging from 6 to 30 km wide and up to 2 km deep. Both underwater active volcanoes and the volcanoes of Iceland and the Azores are confined to the rift and faults of the Mid-Atlantic Ridge. On both sides of the ridge there are basins with a relatively flat bottom, separated by elevated rises. The shelf area in the Atlantic Ocean is larger than in the Pacific.

Mineral resources. Oil and gas reserves have been discovered on the North Sea shelf, in the Gulf of Mexico, Guinea and Biscay. Phosphorite deposits were discovered in the area of ​​rising deep waters off the coast of North Africa in tropical latitudes. Placer deposits of tin off the coast of Great Britain and Florida, as well as diamond deposits off the coast of South-West Africa, have been identified on the shelf in sediments of ancient and modern rivers. Ferromanganese nodules were found in bottom basins off the coasts of Florida and Newfoundland.

Climate.The Atlantic Ocean is located in all climate zones of the Earth. The main part of the ocean is between 40° N latitude. and 42° S - is located in subtropical, tropical, subequatorial and equatorial climatic zones. There are high positive air temperatures here all year round. The most severe climate is found in sub-Antarctic and Antarctic latitudes, and to a lesser extent in subpolar and northern latitudes.

Currents.In the Atlantic, as in the Pacific, two rings of surface currents are formed. In the northern hemisphere, the Northern Trade Wind Current, Gulf Stream, North Atlantic and Canary Currents form a clockwise movement of water. In the southern hemisphere, the South Trade Wind, the Brazilian Current, the West Wind Current and the Benguela Current form the movement of water counterclockwise. Due to the considerable extent of the Atlantic Ocean from north to south, meridional water flows are more developed in it than latitudinal ones.

Properties of water. The zoning of water masses in the ocean is complicated by the influence of land and sea currents. This is manifested primarily in the temperature distribution of surface waters. In many areas of the ocean, isotherms off the coast deviate sharply from the latitudinal direction.

The northern half of the ocean is warmer than the southern half, the temperature difference reaches 6°C. The average surface water temperature (16.5°C) is slightly lower than in the Pacific Ocean. The cooling effect is exerted by the waters and ice of the Arctic and Antarctic. The salinity of surface waters in the Atlantic Ocean is high. One of the reasons for increased salinity is that a significant part of the moisture evaporating from the water area does not return to the ocean, but is transferred to neighboring continents (due to the relative narrowness of the ocean).

Many large rivers flow into the Atlantic Ocean and its seas: the Amazon, Congo, Mississippi, Nile, Danube, La Plata, etc.
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They carry huge masses of fresh water, suspended material and pollutants into the ocean. Ice forms in the desalinated bays and seas of subpolar and temperate latitudes in winter off the western shores of the ocean. Numerous icebergs and floating sea ice are disrupting shipping in the North Atlantic Ocean.

Organic world. The Atlantic Ocean is poorer in flora and fauna species than the Pacific Ocean. One of the reasons for this is its relative geological youth and noticeable cooling in the Quaternary period during the glaciation of the northern hemisphere. At the same time, in quantitative terms, the ocean is rich in organisms - it is the most productive per unit area. This is primarily due to the widespread development of shelves and shallow banks, which are home to many bottom and bottom fish (cod, flounder, perch, etc.). The biological resources of the Atlantic Ocean are depleted in many areas. The ocean's share of global fisheries has declined significantly in recent years.

Natural complexes.In the Atlantic Ocean, all zonal complexes are distinguished - natural zones, except for the North Polar. Water northern subpolar belt rich in life. It is especially developed on the shelves off the coasts of Iceland, Greenland and the Labrador Peninsula.
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Temperate zone characterized by intense interaction of cold and warm waters, its waters are the most productive areas of the Atlantic. Vast expanses of warm waters of two subtropical, two tropical and equatorial zones less productive than the waters of the northern temperate zone.

In the northern subtropical zone it stands out special natural aquatic complex of the Sargasso Sea. It is worth saying that it is characterized by increased water salinity (up to 37.5 ppm) and low bioproductivity. Grow in clear water of pure blue color brown algae - sargassum, which gave the name to the water area.

In the temperate zone of the southern hemisphere, as in the north, natural complexes are rich in life in areas where waters with different temperatures and water densities mix. In the subantarctic and antarctic belts Characterized by the manifestation of seasonal and permanent ice phenomena, which affect the composition of the fauna (krill, cetaceans, notothenia fish).

Economic use. The Atlantic Ocean represents all types of human economic activity in marine areas. Among them, maritime transport is of greatest importance, followed by underwater oil and gas production, and only then by fishing and use of biological resources.

On the shores of the Atlantic there are more than 70 coastal countries with a population of over 1.3 billion people. Many transoceanic routes with large volumes of freight and passenger traffic pass through the ocean. The most significant ports in the world in terms of cargo turnover are located on the coasts of the ocean and its seas.

The already explored mineral resources of the ocean are significant (examples are given above). At the same time, oil and gas fields are currently being intensively developed on the shelf of the North and Caribbean Seas, in the Bay of Biscay. Many countries that previously did not have significant reserves of these types of mineral raw materials are now experiencing economic growth due to their production (England, Norway, the Netherlands, Mexico, etc.).

Biological resources oceans have been used intensively for a long time. At the same time, due to overfishing of a number of valuable commercial fish species, in recent years the Atlantic is inferior to the Pacific Ocean in the production of fish and seafood.

Intensive human economic activity in the Atlantic Ocean and its seas causes a noticeable deterioration of the natural environment - both in the ocean (water and air pollution, reduction in stocks of commercial fish species) and on the coasts. In particular, recreational conditions on the ocean shores are deteriorating. In order to prevent further and reduce existing pollution of the natural environment of the Atlantic Ocean, scientific recommendations are being developed and international agreements are being concluded on the rational use of ocean resources.

Atlantic Ocean - concept and types. Classification and features of the category "Atlantic Ocean" 2017, 2018.

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 of four main atmospheric centers: the 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. 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. 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). Tropical hurricanes are a frequent occurrence in the subtropical zone. 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 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. 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 reaches 40°N in July.

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.

Oceanological conditions over large areas of the Atlantic Ocean are favorable for the development of life, therefore it is the most productive of all the oceans (260 kg/km2). Until 1958, it was a leader in the production of fish and non-fish products. However, many years of intensive fishing had a negative impact on the raw material base, which led to a slowdown in the growth of catches. At the same time, a sharp increase in the Peruvian anchovy catch began, and the Atlantic Ocean lost primacy in catches to the Pacific. In 2004, the Atlantic Ocean accounted for 43% of the world's catch. The volume of production of fish and non-fish objects varies by year and by area of ​​production.

Mining and fishing

The majority of the catch comes from the Northeast Atlantic. This region is followed by the North-West, Central-East and South-East regions; The North Atlantic has been and continues to be the main fishing area, although in recent years the role of its central and southern zones has noticeably increased. In the ocean as a whole, catches in 2006 exceeded the annual average for 2001–2005. In 2009, production was lower than the 2006 catch by 1,985 thousand tons. Against the background of this general decrease in catches in two regions of the Atlantic, in the North-West and North-East, production decreased by 2198 thousand tons. Consequently, the main catch losses occurred in the North Atlantic.

Analysis of fisheries (including non-fish objects) in the Atlantic Ocean in recent years has revealed the main reasons for changes in catches in different fishing areas.

In the Northwestern region of the ocean, production has decreased due to strict regulation of fishing within the 200-mile zones of the United States and Canada. At the same time, these states began to pursue a discriminatory policy here towards socialist countries, sharply limiting their fishing quotas, although they themselves do not fully use the raw material base of the region.

The increase in catches in the Southwest Atlantic is associated with an increase in catches in South American countries.

In the South-East Atlantic, the total catch of African countries has decreased, but at the same time, compared to 2006, the catches of almost all states conducting expeditionary fishing here, and multinational corporations, the nationality of which is difficult to determine, have increased.

In the Antarctic part of the Atlantic Ocean in 2009, the total production volume reached 452 thousand tons, of which 106.8 thousand tons were crustaceans.

The data presented indicate that in modern conditions, the extraction of biological resources in the Atlantic Ocean has largely become determined by legal and political factors.

Coastal marine placers rich in ilmenite, rutile, zircon and monocyte are represented by large deposits on the coasts of Brazil and the Florida Peninsula (USA). On a smaller scale, minerals of this type are concentrated off the coast of Argentina, Uruguay, Denmark, Spain, and Portugal. Tin-bearing and ferruginous sands are found on the Atlantic coast of North America and Europe, and coastal-marine placers of diamonds, gold, and platinum are found off the coast of South-West Africa (Angola, Namibia, South Africa). On the shelf of the Atlantic coast of North and South America and Africa (Blake Plateau, off Morocco, Liberia, etc.) phosphorite formations and phosphate sands have been discovered (the extraction of which is still unprofitable due to its lower quality compared to land phosphorites). Vast fields of ferromanganese nodules are located in the northwestern part of the ocean, in the North American Basin and on the Blake Plateau. The total reserves of ferromanganese nodules in the Atlantic Ocean are estimated at 45 billion tons. The level of concentration of non-ferrous metals in them (with a low manganese content) is close to that of ore-bearing land rocks. A large number of offshore oil and gas fields have been discovered in the Atlantic Ocean and its seas and are being intensively developed. The richest offshore oil and gas areas in the world include the Gulf of Mexico, the Maracaibo Lagoon, the North Sea, and the Gulf of Guinea, which are being intensively developed. Three large oil and gas provinces have been identified in the Western Atlantic: 1) from Davis Strait to the latitude of New York (industrial reserves near Labrador and south of Newfoundland); 2) on the Brazilian shelf from Cape Calcañar to Rio de Janeiro (more than 25 fields have been discovered); 3) in the coastal waters of Argentina from the Gulf of San Jorge to the Strait of Magellan. According to estimates, promising oil and gas areas make up about 1/4 of the ocean, and the total potential recoverable oil and gas resources are estimated at more than 80 billion tons. Some areas of the Atlantic shelf are rich in coal (Great Britain, Canada), iron ore (Canada, Finland) .

24. Transport system and ports of the Atlantic Ocean.

A leading place among other sea basins in the world. The world's largest oil cargo flow from the Persian Gulf countries on its way to the Atlantic is divided into two branches: one goes around Africa from the south and heads to Western Europe, North and South America, and the other through Suez. Oil from North African countries to Europe and, partially, to North America, from the Gulf of Guinea countries to the USA and Brazil. From Mexico and Venezuela to the USA via the Caribbean Sea, and from Alaska via the Panama Canal to ports on the Atlantic coast. Liquefied gas from North African countries (Algeria, Libya) to Western Europe and the USA. In dry bulk transportation - iron ore (from Brazilian and Venezuelan ports to Europe), grain (from the USA, Canada, Argentina - to European ports), phosphorites (from the USA (Florida), Morocco - Western Europe), bauxite and alumina (from Jamaica, Suriname and Guyana in the USA), manganese (from Brazil, West and South Africa), chrome ore (from South Africa and the Mediterranean), zinc and nickel ores (from Canada), timber cargo (from Canada, Scandinavian countries and northern ports Russia to Western Europe). General cargo, which is 2/3 transported by liner vessels. Universal ports with a high level of mechanization. Western Europe - 1/2 of cargo turnover. The English Channel to the Kiel Canal, the east coast of Great Britain, Mediterranean port complexes along the coast of the Gulf of Lyon and the Ligurian Sea. USA from Gulf of Maine to Chesapeake Bay: New York - New Jersey, Ameriport and Hampton Rhodes. The Gulf of Mexico, where there are three main port-industrial complexes (New Orleans and Baton Rouge; Galveston Bay and the Houston Canal; the ports of Beaumont, Port Arthur, and Orange connected to the Gulf of Mexico by canals through Lake Sabine). oil (Amuay, Cartagena, Tobruk) and chemical (Arzev, Alexandria, Abidjan) factories, aluminum (Belen, San Luis, Puerto Madryn), metallurgy (Tubaran, Maracaibo, Warrij), cement (Freeport) industries. the southeastern coast of Brazil (Santos, Rio de Janeiro, Victoria) and in the Gulf of La Plata (Buenos Aires, Rosario, Santa Fe). (Port Harcourt, Lagos, Niger Delta). North African ports are wide open to the sea, and their universal nature requires significant costs to modernize the port facilities (Algeria, Tripoli, Casablanca, Alexandria and Tunisia). On a number of Caribbean islands (Bahamas, Cayman, Virgin Islands), the deepest transshipment terminals for large tankers (400 - 600 thousand deadweight tons) in this part of the ocean have been built.