Describe other natural resources of the Atlantic Ocean. natural resources of the atlantic ocean

The Atlantic Ocean is the second largest after the Pacific, the ocean of the Earth. Like the Pacific, it extends from the subarctic latitudes to the Subantarctic, that is, from the underwater threshold that separates it from the Arctic Ocean in the north, to the coast 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 position of the largest oceans of the 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 twice as small as the Pacific Ocean.

The narrowest part of the Atlantic Ocean falls on the same latitudes where the Pacific Ocean reaches its greatest extent. The Atlantic Ocean differs from the Pacific Ocean in the wider development of the shelf, especially in the Newfoundland region and off the southeastern coast of South America, as well as in the Bay of Biscay, the North Sea and in the British Isles. The Atlantic is also characterized by a large number of mainland islands and island archipelagos, relatively recently lost contact with the continents (Newfoundland, Antilles, Falkland, British, etc.). The islands of volcanic origin (Canaries, Azores, St. Helena, etc.) are not numerous in comparison with the Pacific Ocean.

The shores of the Atlantic Ocean are most strongly dissected north of the equator. In the same place, deeply going into the land of North America and Eurasia, there 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, and also the intercontinental Mediterranean Sea, connected by straits with the Marmara, Black and Azov inland seas. To the north of the equator, off the coast of Africa, is the vast Gulf of Guinea, wide open to the ocean.

The formation of the modern basin of the Atlantic Ocean began approximately 200 million years ago, in the Triassic, with the opening of a rift at the site of the future Tethys Ocean and the division of the Pangea ancestral continent into Laurasia and Gondwana (see the continental drift map). Subsequently, there was a division of Gondwana into two parts - African-South American and Australo-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 in the place 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 disintegrated Gondwana - the African lithospheric plate, as well as the Hindustan block, Tethys closed. The Mediterranean (Alpine-Himalayan) orogenic belt and its western continuation - the Antilles-Caribbean fold system - were formed. The intercontinental basin of the Mediterranean Sea, the Marmara, Black and Azov Seas, 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 "remainder" of Tethys in the west is the Caribbean Sea with land adjacent to it and part of the Gulf of Mexico.

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

Along the entire ocean from north to south, occupying its axial part, the Mid-Atlantic Ridge passes, dividing the continental-oceanic lithospheric plates located on both sides of it: 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 near the coast of Greenland to the connection with the African-Antarctic Ridge near 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 about a third of the area of ​​the entire ocean floor. A system of deep longitudinal faults (rifts) runs along the crest of the ridge, and transverse (transform) faults cross its entire length. The areas of the most active manifestation of ancient and modern, underwater and surface, rift volcanism in the northern part of the Mid-Atlantic Ridge are the Azores at 40 ° N. latitude. and the unique, largest volcanic island of the Earth - Iceland on the border with the Arctic Ocean.

Iceland Island is located directly on the Mid-Atlantic Ridge, in the middle it is crossed by a system of rifts - the "spreading axis", bifurcating in the southeast. Almost all the extinct and active volcanoes of Iceland rise along this axis, the emergence of which does not stop 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 move 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 speed of movement in this case 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, Tristan da Cunha.

On both sides of the Mid-Atlantic Ridge stretches the ocean floor, composed of basalt crust and thick strata of Meso-Cenozoic deposits. In the structure of the surface of the bed, as in the Pacific Ocean, numerous deep-water basins are distinguished (more than 5000 m, and the North American basin even more than 7000 m deep), separated from each other by underwater uplifts and ridges. Basins of the American side of the Atlantic - Newfoundland, North American, Guiana, Brazilian and Argentinean; from Eurasia and Africa - Western European, Canary, Angolan and Cape.

The largest uplift in the bed of the Atlantic Ocean is the Bermuda Plateau within the North American Basin. Basically composed of oceanic basalts, it is overlain by two kilometers of sediment. On its surface, located at a depth of 4000 m, volcanoes rise, topped with coral structures that form the Bermuda archipelago. Opposite the coast of South America, between the Brazilian and Argentine basins, there is the Rio Grande plateau, also covered by thick strata 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 comes out on the mainland in the Gulf of Guinea in the form of a continental rift, to which the active volcano Cameroon is confined. Even further south, between the Angolan and Cape basins, the underwater blocky ridge Kitovy comes out to the shores of South-West Africa.

In the main bed of the Atlantic Ocean, it borders directly on the underwater margins of the continents. The transitional zone is incomparably 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 closed by the end of the Paleogene, separated from each other in the process of opening 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 terrestrial mountain structures, and the types of manifestations of volcanic activity.

The basin 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. Communication was restored only at the beginning of the Quaternary period. By peninsulas and groups of continental islands, formed by structures of various ages, the sea is divided into a number of basins, in the structure of the bottom of which the earth's crust of the suboceanic type predominates. 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. The continental crust is also characteristic of some deep-sea basins.

In the Ionian Sea, between the basins of the Central Mediterranean, Crete and Levantine, the Central Mediterranean shaft stretches, to which the Hellenic deep-water 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 basin of the Mediterranean Sea 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 Gulf of Naples and adjacent land areas. Along with the most active volcanoes in Europe (Vesuvius, Etna, Stromboli), there are many objects that testify to manifestations of paleovolcanism and active volcanic activity during historical time. The features of the Mediterranean noted here make it possible to consider it “as a transitional region at the latest stage of development” (OK 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 features of the nature of these water bodies are considered in the relevant sections of the regional review of Eurasia.

The second transitional 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 bed by peninsulas and island arcs of continental and volcanic origin. The Gulf of Mexico is a depression of the Mesozoic age with a depth in the central part of more than 4000 m, 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 are concentrated. 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 arch of the Antilles, formed in the Neogene. Its maximum depths exceed 7000 m. From the ocean side, the Antilles-Caribbean transitional region is limited by the Puerto Rico deep-sea trench, 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 area 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 Trench (8325 m) and an arc of volcanic islands of the same name, planted on an underwater uplift. The bottom of the Scotia Sea is composed of a suboceanic type of crust, in the west it is replaced by the oceanic crust of the Pacific Ocean floor. The surrounding groups of islands (South Georgia and others) are of continental origin.

Vast expanses of the 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 stretched 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, obviously, should be attributed to the end of the Neogene, and off the coast of Europe - to the Quaternary period. This is the reason for the existence in its relief of "terrestrial" forms - erosional hollows, dune hills, etc., and in more northern regions - 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 affect the features of climate formation and the hydrological conditions of each of them. Approximately the same extent from north to south, between the subpolar latitudes of both hemispheres, a much larger size and massiveness of the land that limits the oceans in the northern hemisphere compared to the southern, relatively weak connection and limited possibilities for 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 action of the atmosphere, the direction of the 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 as the Atlantic Ocean in surface area and its widest part falls on the intertropical space, where it is connected through the interisland seas and straits of Southeast Asia with the warmest part of the Indian Ocean. The Atlantic Ocean in equatorial latitudes has the smallest width, from the east and west it is limited by massive land areas of Africa and South America. These features, as well as differences in the age and structure of the ocean basins themselves, create a geographical identity for each of them, and individual features are more characteristic of the northern parts of the oceans, while in the southern hemisphere the similarities between them are much more pronounced.

The main baric systems over the Atlantic Ocean, which determine the meteorological situation throughout the year, are the equatorial depression, which, like 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 trade winds flow out of the depression - northeast in the northern hemisphere and southeast in the south.

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

In the winter of the southern hemisphere, the southeast trade wind penetrates to the equator and somewhat to the north, towards the Gulf of Guinea and the northern part of 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 the western transfer is active, winds blow, often reaching storm strength, dense clouds and fogs are observed, and heavy precipitation in the form of rain and snow falls. These are the "roaring forties" latitudes, which have already been mentioned in the sections devoted to the nature of the Pacific and Indian oceans. Southeasterly and easterly winds blow from Antarctica in high latitudes, with which icebergs and sea ice are carried northward.

In the warm half of the year, the main directions of air flow remain, but the equatorial trough widens to the south, the southeast trade wind intensifies, rushing into the 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 that are characteristic of the southern part of the ocean. This is due both to the features of the water area itself and to the size of the land limiting it, the temperature and air pressure over which change dramatically during the year. The most significant pressure and temperature contrasts 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-filled 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 water from the south into the northeastern part of the Atlantic and the absence of cold water from the Arctic Ocean.

In the north of the Atlantic Ocean, a closed area of ​​low pressure forms in winter - the Icelandic, or North Atlantic, minimum. Its interaction with the Azores (North Atlantic) maximum located at the 30th parallel creates a prevailing westerly wind flow over the North Atlantic, which carries humid, 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 persists only above the Greenland ice sheet, low pressure centers are established over the continents, and the Icelandic Low is weakening. The western transport remains the main circulation process in temperate and high latitudes, but it is not as intense as in winter. The Azores High is intensifying and expanding, 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 moist unstable air enters along the periphery of the Azores High, monsoon-type precipitation occurs, 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 great 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 - Katrina, Rita and Emily - hit the south coast of the United States, the first of which caused great damage to the city of New Orleans.

The system of surface currents of the Atlantic Ocean in general terms repeats their circulation in the Pacific Ocean.

In equatorial latitudes, there are two trade wind currents - the North Trade Wind and the South Trade Wind, moving from east to west. Between them, the trade wind countercurrent moves to the east. The Northern Equatorial Current passes near 20°N. and off the coast of North America gradually deviates to the north. The South Tradewind Current, passing south of the equator from the coast of Africa to the west, reaches the eastern ledge of the South American mainland and, at Cape Cabo Branco, is divided into two branches running along the coast of South America. Its northern branch (the 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 in the North Atlantic. The southern branch (Brazilian Current) reaches 40°S, where it meets with a branch of the circumpolar West Winds Current, the cold Falkland Current. Another branch of the West Winds current, carrying relatively cold water northward, enters the Atlantic Ocean off the southwestern coast of Africa. This is the Benguela Current - an analogue of the Peru Current of the Pacific Ocean. Its influence can be traced almost to the equator, where it flows into the South Equatorial 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 has significant differences from the system of currents in the northern part of the Pacific.

A branch of the North Equatorial Current, reinforced by the Guiana Current, penetrates through the Caribbean Sea and the Yucatan Strait into the Gulf of Mexico, causing a significant increase in the water level there compared to the ocean. As a result, a powerful sewage current arises, which, bending around Cuba, through the Florida Strait, enters the ocean called the Gulf Stream (“stream from the bay”). Thus, off the southeastern coast of North America, the greatest system of warm surface currents of the World Ocean is born.

Gulf Stream at 30°N and 79°W merges with the warm Antilles Current, which is a continuation of the North Trade Wind Current. Further, the Gulf Stream runs along the edge of the continental shelf to about 36°N. At Cape Hatteras, deviating under the influence of the rotation of the Earth, it turns east, skirting the edge of the Great Newfoundland Bank, and leaves for the shores of Europe called the North Atlantic Current, or "Gulf Stream Drift".

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

North Atlantic Current at 50°N and 20°W splits into three branches. The northern one (the 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, the depth is 500 m, the flow rate is from 9 to 12 km per day. The water temperature on the surface 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. Pouring into the Northern Equatorial Current, it closes the subtropical circulation of the North Atlantic.

The northwestern part of the Atlantic Ocean is mainly under the influence of cold waters coming from the Arctic, and other hydrological conditions develop there. In the area of ​​Newfoundland Island, the cold waters of the Labrador Current move towards the Gulf Stream, pushing the warm waters of the 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 contributes to the development of microorganisms in the upper layer of water and, consequently, to the abundance of fish. Especially famous in this regard is the Great Newfoundland Bank, where cod, herring, and salmon are caught.

Up to about 43°N The Labrador Current carries icebergs and sea ice, which, combined with the fogs characteristic of this part of the ocean, poses a great danger to navigation. A tragic illustration is the disaster of the Titanic liner, which crashed in 1912 800 km southeast of Newfoundland.

The temperature of the water 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 (with the exception of the northwestern regions), the temperature of surface waters fluctuates during the year from 6 to 10 °C. In the southern hemisphere at the same latitude it is close to 0°C and lower in the eastern part 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 ​​noted at the same latitudes in the Pacific and Indian Oceans.

Salinity indicators of the surface waters of the Atlantic Ocean are much more diverse than in other oceans. The highest values ​​(36-37% o - the maximum value for the open part of the World Ocean) are typical for tropical regions with low annual precipitation and strong evaporation. High salinity is also associated with the inflow of salt water from the Mediterranean Sea through the shallow Strait of Gibraltar. On the other hand, large areas of the water surface have an 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, the 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 led to the existence of a unique natural formation here, called the Sargasso Sea. This is a section of the Atlantic Ocean between 21 and 36 N. latitude. and 40 and 70°W The Sargasso Sea is "borderless, but not limitless." Currents can be considered as its peculiar boundaries: 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 mobile, 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 water area are their low mobility, poor development of plankton and the highest transparency in the World Ocean, especially in summer (up to a depth of 66 m). High temperatures and salinity are also characteristic.

The sea got its name from floating brown algae belonging to the genus Sargassum. Algae are carried by currents, and the area of ​​their accumulation 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 no such number of them anywhere else in the oceans. European and American eels spawn in the waters of the Sargasso Sea at depths of 500-600 m. Then the larvae of these valuable commercial fish are carried by currents to the mouths of large rivers, and adults again return to spawn in the Sargasso Sea. They take several years to complete their full life cycle.

The similarity noted above between the Atlantic and Pacific oceans is 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 common features of the World Ocean.

As for 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 a much greater species diversity in the intertropical space and subtropics.

The temperate and subantarctic belts of the southern hemisphere are part of the Antarctic biogeographic region.

For the Atlantic Ocean, as for other oceans in these latitudes, the presence of large mammals in the composition of the fauna - fur seals, several species of true seals, and cetaceans is characteristic. The latter are represented here most fully in comparison with other parts of the World Ocean, but in the middle of the last century they were subjected to severe extermination. Of the fish for the South Atlantic, endemic families of nototheniids and white-blooded pikes are characteristic. The number of plankton species is small, but its biomass, especially in temperate latitudes, is very significant. The zooplankton includes copepods (krill) and pteropods; phytoplankton is dominated by diatoms. For the corresponding latitudes of the northern part of the Atlantic Ocean (the North Atlantic biogeographic region), the presence in the composition of the organic world of the same groups of living organisms as in the southern hemisphere is typical, 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 large 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 intensive fishing. On the banks off the coast of North America, in the North and Baltic Seas, cod, herring, halibut, sea bass, and sprat are caught. 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 fishing resources of the Atlantic 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 are observed in the tropical part of the Atlantic Ocean. The plankton contains numerous foraminifers, radiolarians, and copepods. Nekton is characterized by sea turtles, squids, sharks, flying fish; Of the commercial fish species, tuna, sardines, mackerel are abundant, in zones of cold currents - anchovies. Among the benthic forms, various algae are represented: green, red, brown (already mentioned above Sargasso); from animals - octopuses, coral polyps.

But despite the relative species richness of the organic world in the tropical part of the Atlantic Ocean, it is still less diverse than in the Pacific and even in the Indian Oceans. Coral polyps are much poorer here, the distribution of which is limited mainly to the Caribbean; there are no sea snakes, many species of fish. Perhaps this is due to the fact that in equatorial 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 bounded 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 ocean in the world. The coastline of the ocean in the northern hemisphere is heavily dissected by numerous peninsulas and bays. There are many islands, inland and marginal seas near the continents. The Atlantic consists of 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 6 to 30 km wide and up to 2 km deep. Both underwater active volcanoes and volcanoes of Iceland and the Azores are confined to the rift and faults of the Mid-Atlantic Ridge. On both sides of the ridge lie basins with a relatively flat bottom, separated by elevated elevations. The shelf area in the Atlantic Ocean is larger than in the Pacific.

Mineral resources. Oil and gas reserves have been discovered on the shelf of the North Sea, in the Gulf of Mexico, Guinea and Biscay. Phosphorite deposits have been discovered in the area of ​​deep water rise 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 found on the shelf in the sediments of ancient and modern rivers. Ferromanganese nodules have been found in bottom basins off the coasts of Florida and Newfoundland.

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

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

Water properties. The zonality of water masses in the ocean is complicated by the influence of land and sea currents. This is manifested primarily in the distribution of surface water temperatures. In many areas of the ocean, the isotherms near the coast deviate sharply from the latitudinal direction.

The northern half of the ocean is warmer than the southern, 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 ices of the Arctic and Antarctic. 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 again, 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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Οʜᴎ carry huge masses of fresh water, suspended material and pollutants into the ocean. In desalinated bays and seas of subpolar and temperate latitudes, ice forms near the western shores of the ocean in winter. Numerous icebergs and floating sea ice hinder navigation in the North Atlantic Ocean.

organic world. The Atlantic Ocean is poorer in species in the composition of flora and fauna than the Pacific. One of the reasons for this is its relative geological youth and a 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 wide development of shelves and shallow banks, on which many demersal and demersal fish (cod, flounder, perch, etc.) live. The biological resources of the Atlantic Ocean are depleted in many areas. The share of the ocean in world fisheries has declined significantly in recent years.

natural complexes.In the Atlantic Ocean, all zonal complexes are distinguished - natural belts, 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 subtropical, two tropical and equatorial belts less productive than the waters of the northern temperate zone.

In the northern subtropical zone stands out a 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. In clear water, pure blue colors grow brown algae - sargasso, which gave the name of 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 the manifestation of seasonal and permanent ice phenomena, which are reflected in the composition of the fauna (krill, cetaceans, notothenia fish), is characteristic.

Economic use. All types of human economic activity in marine areas are represented in the Atlantic Ocean. Among them, maritime transport is of the greatest importance, then - underwater oil and gas production, only then - the catch and use of biological resources.

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

The already explored mineral resources of the ocean are significant (examples are given above). At the same time, oil and gas fields are 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 an economic upsurge due to their extraction (England, Norway, the Netherlands, Mexico, etc.).

biological resources oceans have long been intensively used. At the same time, in connection with the overfishing of a number of valuable commercial fish species, in recent years the Atlantic has been inferior to the Pacific Ocean in terms of fish and seafood production.

Intensive human economic activity in the waters of the Atlantic Ocean and its seas causes a noticeable deterioration of the natural environment - both in the ocean (water and air pollution, a decrease in the stocks of commercial fish species) and on the coasts. In particular, recreational conditions on the ocean coast are deteriorating. In order to prevent further and reduce the 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 waters 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: Greenland and Antarctic maximums, Icelandic and Antarctic minimums. In addition, two anticyclones constantly operate in the subtropics: Azores and South Atlantic. They are separated by an equatorial region of low pressure. This distribution of baric 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 seas of the Antarctic and the Mediterranean Sea. Tropical latitudes are characterized by tempera. - 20°C. To the north and south of the tropics are subtropical zones with more noticeable seasonal ones (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 kept within 10-15 °C, and the coldest -10 °C. Precipitation is about 1000 mm.

surface currents. North Equatorial Current (t)> Antilles (t)> Mexico. Gulf>Florida(t)>Gulf Stream>North Atlantic(t)>Canary(x)>Northern Equatorial Current(t) – northern circle.

South trade winds> Guiana temp. (North) and the Brazilian Warm. (south)>tech. Western winds (x)> Benguela (x)> South trade winds - southern circle.

There are several levels in the Atlantic Ocean deep 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 greatest tide values ​​are confined to the Atlantic Ocean, which are noted in the fjord 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 noted, salinity decreases to 34 ‰. A sharp desalination of water occurs in the estuarine 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. A particularly powerful upwelling zone stretches along the entire western coast of Africa, due to the wind<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 subditoral zone by kelp and alaria) and red algae. In the tropical zone, green (caulerpa), red (calcareous lithotamnia) and brown algae (sargasso) predominate. In the southern hemisphere, bottom vegetation is mainly represented by kelp. Phytoplankton of the Atlantic Ocean has 245 species: peridine, coccolithophorids, diatoms. The latter have a clearly defined zonal distribution; the maximum number of them lives in temperate latitudes of the northern and southern hemispheres. The population of diatoms is most dense in the strip of the Current of the Western Winds.

The distribution of the fauna of the Atlantic Ocean has a pronounced zonal character. In the subantarctic and antarctic In the waters of fish, 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 zone of the temperate zone, the biomass reaches its maximum. In zooplankton, copepods and pteropods predominate; in nekton, whales (blue whales), pinnipeds, and their fish are nototheniids. In the tropical zone, zooplankton is represented by numerous species of foraminifers and pteropods, several species of radiolarians, copepods, larvae of molluscs and fish, as well as siphonophores, various jellyfish, large cephalopods (squids), and octopuses among benthal forms. Commercial fish are represented by mackerel, tuna, sardines, in areas of cold currents - anchovies. To tropical and subtropical corals are confined to zones. temperate latitudes northern hemisphere are characterized by abundant life with a relatively small diversity of species. Of the commercial fish, the most important are herring, cod, haddock, halibut, and sea bass. The most common zooplankton species are foraminifera and copepods. 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 fish species, sponges, and hydroids. Several species of endemic polychaetes, isopods, and holothurians have been found in the Puerto Rico Trench.

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

biological resources. The Atlantic Ocean provides 2/5 of the world catch and its share decreases over the years. In subantarctic and antarctic waters, notothenia, blue 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, the volume of fishing fell sharply, but after the introduction of strict limits, fish stocks are gradually recovering. Several international fisheries conventions operate in the Atlantic Ocean basin, which aim at the efficient and rational use of biological resources, based on the application of scientifically based measures to regulate fishing.

Oceanological conditions in large areas of the Atlantic Ocean are favorable for the development of life, therefore, of all the oceans, it is the most productive (260 kg / km 2). Until 1958, he was a leader in the production of fish and non-fish products. However, many years of intensive fishing had a negative impact on the resource base, which led to a slowdown in the growth of catches. At the same time, a sharp increase in the catch of the Peruvian anchovy began, and the Atlantic Ocean gave way to the Pacific in catches. In 2004, the Atlantic Ocean provided 43% of the world's catch. The volume of production of fish and non-fish objects fluctuates both over the years and over the areas of production.

Mining and fishing

Most of the catch comes from the Northeast Atlantic. This district is followed by the Northwestern, Central Eastern and Southeastern 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 in 2006 by 1,985 thousand tons. Against the background of this general decrease in catches in two areas 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.

An analysis of fisheries (including non-fish species) in the Atlantic Ocean in recent years has revealed the main causes of changes in catches in different fishing areas.

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

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

In the South-East Atlantic, the total catch of African countries has decreased, but at the same time, compared with 2006, the catches of almost all states conducting expeditionary fishing here, and multinational corporations, whose nationality is difficult to determine by FAO, 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 accounted for by 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, 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, near Morocco, Liberia, etc.), phosphorite formations and phosphate sands have been found (the extraction of which is still unprofitable due to their lower quality compared to land phosphorites). Extensive 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, which are being intensively developed. The richest offshore oil and gas regions in the world include the Gulf of Mexico, the Maracaibo lagoon, the North Sea, the Gulf of Guinea, which are being intensively developed. Three large oil and gas provinces have been identified in the Western Atlantic: 1) from the Davis Strait to the latitude of New York (commercial reserves near Labrador and south of Newfoundland); 2) offshore Brazil from Cape Kalkanyar 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.

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