Biological resources of the Atlantic Ocean on the map. Biological resources of the Atlantic Ocean

INTRODUCTION

CHAPTER 1. CHARACTERISTICS OF THE ATLANTIC OCEAN

1.1.Geographical location, climatic and hydrological conditions

1.2.Bottom topography

The Atlantic Ocean is second in size only to the Pacific. It is distinguished from other oceans by its highly rugged coastline, forming numerous seas and bays, especially in the northern part. In addition, the total area of ​​river basins flowing into this ocean or its marginal seas is significantly larger than that of rivers flowing into any other ocean. Another difference of the Atlantic Ocean is the relatively small number of islands and the complex bottom topography, which, thanks to underwater ridges and rises, forms many separate basins.
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 – located in subtropical, tropical, subequatorial and equatorial climatic zones. Here all year round high positive air temperatures. The most severe climate is found in sub-Antarctic and Antarctic latitudes, and to a lesser extent in subpolar and northern latitudes.

CHAPTER 2. NATURAL RICHES OF THE ATLANTIC OCEAN

2.1.Waters and their properties

2.2.Flora

2.3.Fauna

2.4. Minerals

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. Greatest influence on temperature regime The Atlantic Ocean is influenced not only by its large meridional extent, but also by water exchange with the Arctic Ocean, the seas of Antarctica and 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). A common occurrence in subtropical zone- tropical hurricanes. In temperate latitudes average temperature himself warm month It stays within 10-15 °C, and the coldest 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 open ocean observed in the subtropical zone (up to 37.25 ‰), and the maximum in the Mediterranean Sea is 39 ‰. IN equatorial zone, where the maximum amount of precipitation is noted, salinity decreases to 34 ‰. A sharp desalination of water occurs in the estuary areas (for example, at the mouth of La Plata 18-19 ‰).

Ice formation. Ice formation in the Atlantic Ocean occurs in the Greenland and Baffin seas and Antarctic waters. The main source of icebergs in the South Atlantic is the Filchner Ice Shelf in the Weddell Sea. Floating ice in the northern hemisphere in July they reach 40°N.

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

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

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

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

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

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. The Gulf Stream then 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.

The organic world of the Atlantic and Pacific Oceans has much in common (Fig. 37). Life in the Atlantic Ocean is also distributed zonally and is concentrated mainly along the coasts of continents and in surface waters.

The Atlantic Ocean is poorer than the Pacific Ocean biological resources. This is due to his relative youth. But the ocean still provides 20% of the world's fish and seafood catch. This is first of all herring, cod, sea ​​bass, hake, tuna.

In temperate and polar latitudes there are many whales, in particular sperm whales and killer whales. Characteristic sea crayfish - lobster, lobsters.

Economic development of the ocean is also associated with mineral resources(Fig. 38). A significant part of them is mined on the shelf. In the North Sea alone, over 100 oil and gas fields have been discovered, hundreds of boreholes have been constructed, and oil and gas pipelines have been laid along the bottom. More than 3,000 special platforms from which oil and gas are produced operate on the shelf of the Gulf of Mexico. Coal is mined in the coastal waters of Canada and Great Britain, and diamonds are mined off the southwestern coast of Africa. Table salt has long been extracted from sea water.

Recently, huge reserves of oil and natural gas have been discovered not only on the shelf, but also at significant depths of the Atlantic Ocean. The coastal zones of Africa, in particular, turned out to be rich in fuel resources. Other areas of the Atlantic floor are also extremely rich in oil and gas - off the northeastern coast of North America, not far from the eastern coast of South America.

The Atlantic Ocean is crossed in different directions by important sea ​​routes. It is no coincidence that the largest ports in the world are located here, among them the Ukrainian one - Odessa. Material from the site

Active human economic activity in the Atlantic Ocean basin has caused significant pollution his water. It is especially noticeable in some seas of the Atlantic Ocean. Thus, the Mediterranean Sea is often called a “sewage” because industrial enterprises dump waste here. A large amount of pollutants also comes with river runoff. In addition, about hundreds of thousands of tons of oil and petroleum products enter its waters every year as a result of accidents and other reasons.

Oil is diluting the waters of the Atlantic Ocean. This kind of thing happens from time to time. In 1980, as a result of a disruption in oil production, 0.5 million tons of oil spilled into the Gulf of Mexico, and the oil slick stretched for 640 km. In 1997, as a result of a collision between two ships in the Caribbean Sea, 287 thousand tons of oil fell into the water.

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Oil and natural gas

The most important mineral resources of the Atlantic Ocean include oil and natural gas. Oil and gas-bearing shelves off the coast of North America include the shelves of the Labrador Sea, as well as the bays of Georges Bank, Nova Scotia and St. Lawrence.

On the eastern shelf of Canada, oil reserves amount to 2.5 billion tons, natural gas reserves - 3.3 trillion. cube m; on the continental slope and eastern shelf of the United States - up to 0.54 billion tons of oil and gas - 0.39 trillion. cube m. More than 280 deposits have been identified on the southern shelf of the United States, and more than 20 deposits off the coast of Mexico. More than 60% of all Venezuela's oil is produced in the Maracaibo Lagoon. The fields near the island of Trinidad in the Gulf of Paria are actively exploited.

Oil and gas bearing areas have been discovered on the shelves of the Gulf of Sao Jorge (Argentina) and the Gulf of Toduz-os-Santos (Brazil). The total reserves of the Caribbean Sea shelves are up to 13 billion tons of oil and 8.5 trillion. cube m of natural gas. Oil fields have been discovered in the Irish and North (114 fields) seas, the Gulf of Guinea (on the Nigerian shelf - 50, off Gabon - 37, off Congo - 3, etc.). On the Mediterranean shelf, the forecast oil reserves are 110-120 billion tons. There are deposits in the Adriatic, Aegean, Ionian seas, off the coasts of Egypt, Tunisia, Spain, etc.

Oil and gas basins

The largest oil and gas basins in the Atlantic Ocean include:

1. Gulf of Mexico oil and gas basin;
2. Maracaiba oil and gas basin.

The oil and gas basin of the Gulf of Mexico is located in the waters of the Gulf and adjacent territories of Mexico, the USA, Cuba, Belize, and Guatemala. The total area of ​​the oil and gas basin is about 2.5 million square meters. km. The initial industrial reserves of oil and condensate (data for 1985) are 18.3 billion tons and natural gas - 14.6 trillion. cube m.

The first deposits on the mainland part of the basin were discovered in 1896 (USA), and on the shelf - in 1938 (USA). In the American part of the basin, the largest deposits were discovered in the 30s. (Agua Dals-Stratton, East Texas, Carthage, Caillou Island, Old Ocean), and in the Mexican part - in the 70s. (Iris-Giraldas, Bermudez, Cantarel).

Note 1

In total, more than 5 thousand oil and 4 thousand gas and gas condensate fields have been discovered in the oil and gas basin of the Gulf of Mexico. 95% of deposits are in the USA.

Gulf of Mexico oil and gas basin confined to the southern regions of the Atlantic Epihercynian platform, represented by the Gulf of Mexico basin and the Gulf Coast. The basin is formed by sedimentary rocks of the Mesozoic-Cenozoic period with a maximum thickness of 15 km. The entire section of the sedimentary cover is associated with oil and gas content.

The furthest offshore deposit was identified at a distance of 240 km from the coast of Louisiana. Individual exploration wells are located at a distance of 260 km at a depth of 600 m. The oil in the outer zone is low-sulfur and light. Sulfur content increases in deposits that are associated with caprocks of salt domes. In the interior regions of the basin, oils are of medium density, methane-naphthenic composition and high-sulfur.

Natural gases contain a small amount of heavy homologues of methane and a lot of gas condensate. The main centers of natural gas production are Texas, Louisiana, Bay of Campeche, and the Reforma region.

On the territory of the Mexican oil and gas basin there is an extensive network of oil and gas pipelines, 75 oil refineries and 400 gas processing plants.

Maracaiba oil and gas basin is located in the northeast of Colombia, northwest of Venezuela, occupies the Gulf of Venezuela and the adjacent part of the landmass, Lake Maracaibo. The pool area is 86 thousand square meters. km, including about 30 thousand sq. km. water areas. The basin is surrounded by individual spurs of the Andes mountain system. The development of oil fields began in 1917. In total, 79 oil fields and 4 gas fields were discovered.

Initial oil reserves were 6.6 billion tons, natural gas - 1.7 trillion. cube m., on the shelf 5 billion tons and 1.2 trillion. cube m. respectively.

The Bolivar coastal-offshore oil and gas accumulation zone, stretching over 3.5 thousand square meters, stands out separately. km. Bolivar unites 8 deposits. The largest oil field is Lama, containing 584 million tons. Potential oil resources are estimated at 9.3 billion tons, natural gas - 1.9 trillion. cube m.

The Maracaiba oil and gas basin is formed mainly by terrigenous deposits of the Mesozoic and Cenozoic. The maximum thickness is 11 km. The reservoirs are sandstones and fractured limestones. A characteristic feature of the basin is its predominant oil content. Gas reserves represent 90% dissolved gas from oil fields. Oils are mainly viscous and heavy. Lighter oils belong to the Cretaceous deposits. The dissolved gas of the Bolivar zone contains heavy homologues of methane and fatty.

The main oil and gas processing centers are located in Punta Cardon and Amuay.

Minerals

The following minerals are mined on continental shelves:

• sulfur (Gulf of Mexico);
• iron ore (near the island of Newfoundland);
• diamonds (continental shelf of South America);
• phosphate sands and phosphorite formations (near Liberia, Morocco, Blake Plateau);
• hard coal (Canada, UK).

Coastal areas are rich in zirconium, titanium, monazite, phosphorites, and amber. The largest deposits are located off the coast of the Florida Peninsula and near Brazil. These minerals were found in smaller quantities off the coast of Uruguay, Argentina, Spain, Denmark, and Portugal.

Ferrous and tin-bearing sands are common on the Atlantic coast of Europe and North America, and deposits of gold, platinum and diamonds are found off the coast of southwestern Africa (Namibia, Angola, South Africa).

Note 2

The extraction of phosphorites and phosphate sand is unprofitable due to their lower quality compared to terrestrial fossils.

In the northwestern regions of the ocean, on the Blake Plateau and in the North American Basin, there are extensive fields of ferromanganese nodules. Their total reserves are estimated at 45 billion tons. They contain a high concentration of non-ferrous metals.

Barite, pebbles, sand, and limestone are mined from the seabed. Atlantic countries extract magnesium, table salt, bromine, and magnesium from sea water (Great Britain, France, Italy, Spain, Argentina, Canada).