What mineral resources is the Atlantic Ocean rich in? Mineral resources and minerals of the Atlantic Ocean
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, more than 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 considerable 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 http://worldofschool.ru
Active human economic activity in the Atlantic Ocean 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 waste is dumped 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.
Climate and hydrological regime of the Atlantic Ocean. Hydrological resources.
Diversity climatic conditions on the surface of the Atlantic Ocean is determined by its large meridional extent and the circulation of air masses under the influence of four main atmospheric centers: the Greenland and Antarctic max., Icelandic and Antarctic minima. In addition, two anticyclones are constantly active in the subtropics: the Azores and the South Atlantic. They are separated by an equatorial region of low pressure. This distribution of pressure regions determines the system of prevailing winds in the Atlantic. The greatest influence on the temperature regime of the Atlantic Ocean is exerted not only by its large meridional extent, but also by water exchange with the Arctic Ocean, the Antarctic seas and the Mediterranean Sea. Tropical latitudes are characterized by temperament. - 20 °C. To the north and south of the tropics there are subtropical zones with more noticeable seasonal zones (from 10 °C in winter to 20 °C in summer). Tropical hurricanes are a frequent occurrence in the subtropical zone. In temperate latitudes, the average temperature of the warmest month is between 10-15 °C, and the coldest month is −10 °C. Precipitation is about 1000 mm.
Surface currents. Northern Trade Wind Current(t)>Antilles(t)>Mexico. Gulf>Florida(t)>Gulf Stream>North Atlantic(t)>Canary(x)>North Trade Wind Current(t) – northern gyre.
Southern trade wind>Guiana heat. (north) and Brazilian heat. (south)>current Western winds(x)>Bengela(x)>Southern trade winds – southern gyre.
There are several tiers in the Atlantic Ocean deep sea currents. A powerful countercurrent passes under the Gulf Stream, the main core of which lies at a depth of up to 3500 m, with a speed of 20 cm/s. The powerful deep Louisiana Current is observed in the eastern part of the Atlantic Ocean, formed by the bottom runoff of saltier and warmer Mediterranean waters through the Strait of Gibraltar.
The highest tide values are confined to the Atlantic Ocean, which are observed in the fiord bays of Canada (in Ungava Bay - 12.4 m, in Frobisher Bay - 16.6 m) and Great Britain (up to 14.4 m in Bristol Bay). The highest tide in the world is recorded in the Bay of Fundy, on the east coast of Canada, where the maximum tide reaches 15.6-18 m.
Salinity. The highest salinity of surface waters in the open ocean is observed in the subtropical zone (up to 37.25 ‰), and the maximum in the Mediterranean Sea is 39 ‰. In the equatorial zone, where the maximum amount of precipitation is recorded, salinity decreases to 34 ‰. A sharp desalination of water occurs in the estuary areas (for example, at the mouth of La Plata 18-19 ‰).
Ice formation. Ice formation in the Atlantic Ocean occurs in the Greenland and Baffin seas and Antarctic waters. The main source of icebergs in the South Atlantic is the Filchner Ice Shelf in the Weddell Sea. Floating ice in the northern hemisphere reaches 40°N in July.
Upwelling. Along the entire western coast of Africa there is a particularly powerful upwelling zone caused by wind driven water,<связан. с пассатной циркуляцией. Также это зоны у Зелёного мыса, у берегов Анголы и Конго. Эти области наиболее благоприятны для развития орг. мира.
The bottom flora of the northern part of the Atlantic is represented by brown (mainly fucoids, and in the subditorial zone - kelp and alaria) and red algae. In the tropical zone, green algae (caulerpa), red algae (calcareous lithothamnia) and brown algae (sargassum) predominate. In the southern hemisphere, bottom vegetation is mainly represented by kelp forests. There are 245 species of phytoplankton in the Atlantic Ocean: peridinea, coccolithophores, and diatoms. The latter have a clearly defined zonal distribution; their maximum number lives in the temperate latitudes of the northern and southern hemispheres. The population of diatoms is most dense in the zone of the Western Wind Current.
The distribution of the fauna of the Atlantic Ocean has a pronounced zonal character. In the subantarctic and antarctic In the waters, notothenia, blue whiting and others are of commercial importance. Benthos and plankton in the Atlantic are poor in both species and biomass. In the subantarctic zone and in the adjacent temperate zone, biomass reaches its maximum. The zooplankton is dominated by copepods and pteropods; the nekton is dominated by mammals such as whales (blue whale), pinnipeds, and their fish - nototheniids. In the tropical zone, zooplankton is represented by numerous species of foraminifera and pteropods, several species of radiolarians, copepods, larvae of mollusks and fish, as well as siphonophores, various jellyfish, large cephalopods (squid), and, among benthic forms, octopuses. Commercial fish are represented by mackerel, tuna, sardines, and in areas of cold currents - anchovies. To tropical and subtropical corals are confined to the zones. Temperate latitudes The northern hemisphere is characterized by abundant life with a relatively small diversity of species. Of the commercial fish, the most important are herring, cod, haddock, halibut, and sea bass. Foraminifera and copepods are the most characteristic of zooplankton. The greatest abundance of plankton is in the area of the Newfoundland Bank and the Norwegian Sea. The deep-sea fauna is represented by crustaceans, echinoderms, specific species of fish, sponges, and hydroids. Several species of endemic polychaetes, isopods, and holothurians have been found in the Puerto Rico Trench.
There are 4 biogeographical regions in the Atlantic Ocean: 1. Arctic; 2. North Atlantic; 3. Tropico-Atlantic; 4. Antarctic.
Biological resources. The Atlantic Ocean provides 2/5 of the world's catch and its share has been decreasing over the years. In subantarctic and Antarctic waters, notothenia, whiting and others are of commercial importance, in the tropical zone - mackerel, tuna, sardine, in areas of cold currents - anchovies, in temperate latitudes of the northern hemisphere - herring, cod, haddock, halibut, sea bass. In the 1970s, due to overfishing of some fish species, fishing volumes declined sharply, but after the introduction of strict limits, fish stocks are gradually recovering. There are several international fisheries conventions in force in the Atlantic Ocean basin, which aim at the effective and rational use of biological resources, based on the application of scientifically based measures to regulate fishing.
Oceanological conditions over large areas of the Atlantic Ocean are favorable for the development of life, therefore it is the most productive of all the oceans (260 kg/km2). Until 1958, it was a leader in the production of fish and non-fish products. However, many years of intensive fishing had a negative impact on the raw material base, which led to a slowdown in the growth of catches. At the same time, a sharp increase in the Peruvian anchovy catch began, and the Atlantic Ocean lost primacy in catches to the Pacific. In 2004, the Atlantic Ocean accounted for 43% of the world's catch. The volume of production of fish and non-fish objects varies by year and by area of production.
Mining and fishing
The majority of the catch comes from the Northeast Atlantic. This region is followed by the North-West, Central-East and South-East regions; The North Atlantic has been and continues to be the main fishing area, although in recent years the role of its central and southern zones has noticeably increased. In the ocean as a whole, catches in 2006 exceeded the annual average for 2001–2005. In 2009, production was lower than the 2006 catch by 1,985 thousand tons. Against the background of this general decrease in catches in two regions of the Atlantic, in the North-West and North-East, production decreased by 2198 thousand tons. Consequently, the main catch losses occurred in the North Atlantic.
Analysis of fisheries (including non-fish objects) in the Atlantic Ocean in recent years has revealed the main reasons for changes in catches in different fishing areas.
In the Northwestern region of the ocean, production has decreased due to strict regulation of fishing within the 200-mile zones of the United States and Canada. At the same time, these states began to pursue a discriminatory policy here towards socialist countries, sharply limiting their fishing quotas, although they themselves do not fully use the raw material base of the region.
The increase in catches in the Southwest Atlantic is associated with an increase in catches in South American countries.
In the South-East Atlantic, the total catch of African countries has decreased, but at the same time, compared to 2006, the catches of almost all states conducting expeditionary fishing here, and multinational corporations, the nationality of which is difficult to determine, have increased.
World Ocean, area with seas 91.6 million km 2; average depth 3926 m; water volume 337 million m3. Includes: Mediterranean seas (Baltic, North, Mediterranean, Black, Azov, Caribbean with the Gulf of Mexico), less isolated seas (in the North - Baffin, Labrador; near Antarctica - Scotia, Weddell, Lazarev, Rieser-Larsen), large bays (Guinea , Biscay, Hudson, Above Lawrence). Islands of the Atlantic Ocean: Greenland (2176 thousand km 2), Iceland (103 thousand km 2), (230 thousand km 2), Greater and Lesser Antilles (220 thousand km 2), Ireland (84 thousand km 2), Cape Verde (4 thousand km 2), Faroes (1.4 thousand km 2), Shetland (1.4 thousand km 2), Azores (2.3 thousand km 2), Madeira (797 km 2), Bermuda (53.3 km 2) and others (See map).
Historical sketch. The Atlantic Ocean has been an object of navigation since the 2nd millennium BC. In the 6th century BC. Phoenician ships sailed around Africa. Ancient Greek navigator Pytheas in the 4th century BC. sailed to the North Atlantic. In the 10th century AD. Norman navigator Eric the Red explored the coast of Greenland. During the Age of Great Geographical Discovery (15-16 centuries), the Portuguese explored the route to the Indian Ocean along the coast of Africa (Vasco da Gama, 1497-98). The Genoese H. Columbus (1492, 1493-96, 1498-1500, 1502-1504) discovered the islands of the Caribbean Sea and. In these and subsequent voyages, the outlines and nature of the coasts were established for the first time, coastal depths, directions and speeds of currents, and climatic characteristics of the Atlantic Ocean were determined. The first soil samples were obtained by the English scientist J. Ross in the Baffin Sea (1817-1818 and others). Determinations of temperature, transparency and other measurements were carried out by expeditions of Russian navigators Yu. F. Lisyansky and I. F. Krusenstern (1803-06), O. E. Kotzebue (1817-18). In 1820, Antarctica was discovered by the Russian expedition of F. F. Bellingshausen and M. P. Lazarev. Interest in studying the relief and soils of the Atlantic Ocean increased in the mid-19th century due to the need to lay transoceanic telegraph cables. Dozens of vessels measured depths and took soil samples (American vessels "Arctic", "Cyclops"; English - "Lighting", "Porcupine"; German - "Gazelle", "Valdivia", "Gauss"; French - "Travaeur", " Talisman", etc.).
A major role in the study of the Atlantic Ocean was played by the British expedition on the ship "Challenger" (1872-76), based on the materials of which, using other data, the first relief and soils of the World Ocean were compiled. The most important expeditions of the 1st half of the 20th century: German on the Meteor (1925-38), American on the Atlantis (30s), Swedish on the Albatross (1947-48). In the early 50s, a number of countries, primarily and, launched extensive research into the geological structure of the Atlantic Ocean floor using precision echo sounders, the latest geophysical methods, and automatic and controlled underwater vehicles. Extensive work has been carried out by modern expeditions on the ships “Mikhail Lomonosov”, “Vityaz”, “Zarya”, “Sedov”, “Ekvator”, “Ob”, “Akademik Kurchatov”, “Akademik Vernadsky”, “Dmitry Mendeleev”, etc. 1968 Deep-sea drilling began on board the American vessel Glomar Challenger.
Hydrological regime. In the upper thickness of the Atlantic Ocean, 4 large-scale gyres are distinguished: the Northern Cyclonic Gyre (north of 45° north latitude), the anticyclonic gyre of the Northern Hemisphere (45° north latitude - 5° south latitude), the anticyclonic gyre of the Southern Hemisphere (5° south latitude - 45° south latitude), Antarctic circumpolar current of cyclonic rotation (45° south latitude - Antarctica). On the western periphery of the gyres there are narrow but powerful currents (2-6 km/h): Labrador - Northern Cyclonic Gyre; Gulf Stream (the most powerful current in the Atlantic Ocean), Guiana Current - Northern Anticyclonic Gyre; Brazilian - Southern Anticyclonic Gyre. In the central and eastern regions of the ocean, currents are relatively weak, with the exception of the equatorial zone.
Bottom waters are formed when surface waters sink in polar latitudes (their average temperature is 1.6°C). In some places they move at high speeds (up to 1.6 km/h) and are capable of eroding sediments and transporting suspended material, creating underwater valleys and large bottom accumulative landforms. Cold and low-salinity bottom Antarctic waters penetrate along the bottoms of basins in the western regions of the Atlantic Ocean to 42° north latitude. The average surface temperature of the Atlantic Ocean is 16.53°C (the South Atlantic is 6°C colder than the North). The warmest waters with an average temperature of 26.7°C are observed at 5-10° northern latitude (thermal equator). Toward Greenland and Antarctica, the water temperature drops to 0°C. The salinity of the waters of the Atlantic Ocean is 34.0-37.3 0/00, the highest water density is over 1027 kg/m 3 in the northeast and south, decreasing to 1022.5 kg/m 3 towards the equator. Tides are predominantly semidiurnal (maximum 18 m in the Bay of Fundy); in some areas mixed and daily tides of 0.5-2.2 m are observed.
Ice. In the northern part of the Atlantic Ocean, ice forms only in the inland seas of temperate latitudes (the Baltic, North and Azov seas, the Gulf of St. Lawrence); a large amount of ice and icebergs are carried out from the Arctic Ocean (Greenland and Baffin seas). In the South Atlantic Ocean, ice and icebergs form off the coast of Antarctica and in the Weddell Sea.
Relief and geological structure. Within the Atlantic Ocean, there is a powerful mountain system stretching from north to south - the Mid-Atlantic Ridge, which is an element of the global system of Mid-Ocean Ridges, as well as deep-sea basins and (map). The Mid-Atlantic Ridge extends over 17 thousand km at a latitude of up to 1000 km. Its ridge in many areas is dissected by longitudinal gorges - rift valleys, as well as transverse depressions - transform faults, which break it into separate blocks with a latitudinal displacement relative to the ridge axis. The relief of the ridge, highly dissected in the axial zone, levels out towards the periphery due to the burial of sediments. Shallow-focus epicenters are localized in the axial zone along the ridge crest and in areas. Along the outskirts of the ridge there are deep-sea basins: in the west - Labrador, Newfoundland, North American, Brazilian, Argentine; in the east - European (including Icelandic, Iberian and Irish Trench), North African (including Canary and Cape Verde), Sierra Leone, Guinea, Angolan and Cape. Within the ocean floor, abyssal plains, hill zones, uplifts and seamounts are distinguished (map). Abyssal plains stretch in two intermittent stripes in the continental parts of deep-sea basins. These are the flattest areas of the earth's surface, the primary relief of which is leveled by sediments with a thickness of 3-3.5 km. Closer to the axis of the Mid-Atlantic Ridge, at a depth of 5.5-6 km, there are zones of abyssal hills. Oceanic rises are located between the continents and the mid-ocean ridge and separate the basins. The largest uplifts: Bermuda, Rio Grande, Rockall, Sierra Leone, Whale Ridge, Canary, Madeira, Cape Verde, etc.
There are thousands of seamounts known in the Atlantic Ocean; almost all of them are probably volcanic structures. The Atlantic Ocean is characterized by unconformable cutting of the geological structures of the continents by the coastline. The depth of the edge is 100-200 m, in the subpolar regions 200-350 m, the width is from several kilometers to several hundred kilometers. The most extensive shelf areas are off the island of Newfoundland, in the North Sea, the Gulf of Mexico and off the coast of Argentina. The shelf topography is characterized by longitudinal grooves along the outer edge. The continental slope of the Atlantic Ocean has a slope of several degrees, a height of 2-4 km, and is characterized by terrace-like ledges and transverse canyons. Within the sloping plain (continental foot) the “granite” layer of the continental crust is pinched out. The transition zone with a special crustal structure includes the marginal deep-sea trenches: Puerto Rico (maximum depth 8742 m), South Sandwich (8325 m), Cayman (7090 m), Oriente (up to 6795 m), within which they are observed as shallow-focus, and deep-focus earthquakes (map).
The similarity of the contours and geological structure of the continents surrounding the Atlantic Ocean, as well as the increase in the age of the basalt bed, the thickness and age of sediments with distance from the axis of the mid-ocean ridge, served as the basis for explaining the origin of the ocean within the framework of the concept of Mobilism. It is assumed that the North Atlantic formed in the Triassic (200 million years ago) during the separation of North America from North-West Africa, the South - 120-105 million years ago during the separation of Africa and South America. The connection of the basins occurred about 90 million years ago (the youngest age of the bottom - about 60 million years - was found in the Northeast of the southern tip of Greenland). Subsequently, the Atlantic Ocean expanded with constant new formation of the crust due to outpourings and intrusions of basalts in the axial zone of the mid-ocean ridge and its partial subsidence into the mantle in the marginal trenches.
Mineral resources. Among the mineral resources of the Atlantic Ocean, gas is also of great importance (map to the station of the World Ocean). North America has oil and gas reserves in the Labrador Sea, the bays of St. Lawrence, Nova Scotia, and Georges Bank. Oil reserves on the eastern shelf of Canada are estimated at 2.5 billion tons, gas reserves at 3.3 trillion. m 3, on the eastern shelf and continental slope of the USA - up to 0.54 billion tons of oil and 0.39 trillion. m 3 gas. More than 280 fields have been discovered on the southern shelf of the United States, and more than 20 fields off the coast (see). More than 60% of Venezuela's oil is produced in the Maracaibo Lagoon (see). The deposits of the Gulf of Paria (Trinidad Island) are actively exploited. The total reserves of the Caribbean Sea shelves amount to 13 billion tons of oil and 8.5 trillion. m 3 gas. Oil and gas bearing areas have been identified on the shelves (Toduz-yc-Santos Bay) and (San Xopxe Bay). Oil fields have been discovered in the North (114 fields) and Irish Seas, the Gulf of Guinea (50 on the Nigerian shelf, 37 off Gabon, 3 off Congo, etc.).
The forecast oil reserves on the Mediterranean shelf are estimated at 110-120 billion tons. There are known deposits in the Aegean, Adriatic, Ionian seas, off the coast of Tunisia, Egypt, Spain, etc. Sulfur is mined in the salt dome structures of the Gulf of Mexico. With the help of horizontal underground workings, coal is extracted from coastal mines in the offshore extensions of continental basins - in the UK (up to 10% of national production) and Canada. Off the eastern coast of the island of Newfoundland is the largest iron ore deposit of Waubana (total reserves of about 2 billion tons). Tin deposits are being developed off the coast of Great Britain (Cornwall peninsula). Heavy minerals (,) are mined off the coast of Florida, in the Gulf of Mexico. off the coast of Brazil, Uruguay, Argentina, the Scandinavian and Iberian Peninsulas, Senegal, South Africa. The shelf of South-West Africa is an area of industrial diamond mining (reserves 12 million). Gold placers have been discovered off the Nova Scotia Peninsula. found on the US shelves, on the Agulhas Bank. The largest fields of ferromanganese nodules in the Atlantic Ocean are located in the North American Basin and on the Blake Plateau near Florida; their extraction is not yet profitable. The main sea routes in the Atlantic Ocean, along which mineral raw materials are transported, mainly developed in the 18th and 19th centuries. In the 1960s, the Atlantic Ocean accounted for 69% of all maritime traffic, except for floating vessels; pipelines are used to transport oil and gas from offshore fields to the shore. The Atlantic Ocean is increasingly being polluted by petroleum products, industrial wastewater from enterprises, containing toxic chemicals, radioactive and other substances that harm marine flora and fauna, are concentrated in marine food products, posing a great danger to humanity, which requires taking effective measures to preventing further pollution of the ocean environment.
TABLE OF CONTENTS
INTRODUCTION
The scientific direction of ocean geography, which emerged as an independent branch of geographical science in the second half of the twentieth century, was officially approved in the decisions of the V and VI Congresses of the Geographical Society of the USSR (1970, 1975) and the I All-Union Conference on Ocean Geography (1983). The main tasks of ocean geography were the study of general geographic patterns within the oceanosphere, the establishment of specific dependencies between natural conditions and ocean ecosystems, between natural resources and the ocean economy, as well as the identification of anomalous regimes of rational environmental management.Physical geography of the ocean deals with the study of the spatial structure and basic physical properties of the ocean as a single natural system, on the one hand, and as part of a more general planetary system - the biosphere - on the other hand. Its tasks include identifying the relationships between the nature of the ocean and continents, large-scale connections between the oceanosphere and the rest of the elements of the Earth’s geographic shell, processes of energy and mass exchange between them, and other phenomena.
The twentieth century, especially its last quarter, was marked by a very intensive increase in anthropogenic impact on the natural environment, which caused an environmental crisis on Earth, which continues in our time. This process covered not only land, but also the World Ocean, especially inland and marginal seas adjacent to economically developed countries. The Atlantic Ocean bears most of the anthropogenic load.
The above circumstances determine the relevance of the chosen topic. Object of study at work is the Atlantic Ocean, subject- its natural resources.
Goal of the work– analyze the natural resources of the Atlantic. To achieve this goal, we set the following tasks:
- give a general description of the Atlantic Ocean;
- analyze the properties of waters, the composition of flora and fauna, and also pay attention to the minerals of the ocean;
- reveal the features and problems of ocean development.
This work will be useful to everyone who is interested in issues of oceanology, as well as environmental management.
CHAPTER 1. CHARACTERISTICS OF THE ATLANTIC OCEAN
1.1.Geographical location, climatic and hydrological conditions
The Atlantic Ocean is the most studied and developed by people. It got its name from the titan Atlas (according to Greek mythology, holding the vault of heaven on his shoulders). At different times it was called differently: “The Sea beyond the Pillars of Hercules”, “Atlantic”, “Western Ocean”, “Sea of Darkness”, etc. The name "Atlantic Ocean" first appeared in 1507 on Wald-Seemüller's map, and since then the name has become established in geography.The boundaries of the Atlantic Ocean along the shores of the continents (Eurasia, Africa, the Americas and Antarctica) are natural, with other oceans (the Arctic, Pacific and Indian) - largely conditional.
The Atlantic Ocean borders the Arctic Ocean at 70° N. w. (Baffin Island - Disko Island), then from Cape Brewster (Greenland) along the Icelandic-Farrer threshold to 6° N. w. (Scandinavian Peninsula); with the Pacific Ocean - from about. Oste (Terra del Fuego) to Cape Sternek (Antarctic Peninsula); with the Indian Ocean - 20° east. from Cape Agulhas to Antarctica. The rest of the ocean is limited by the coastlines of Eurasia, Africa, North and South America, and Antarctica (Fig. 1). The given boundaries are officially accepted in our country and are indicated in the Atlas of the Oceans (publishing house of the Ministry of Defense of the USSR and the Navy, 1980). Within the designated limits, the ocean area is 93.4 million km 2, the volume of water is 322.7 million km 3. Water exchange occurs in 46 years, which is 2 times faster than in the Pacific Ocean.
The significant role of the Atlantic in people’s lives is largely explained by purely geographical circumstances:
a large extent (from the Arctic to the Antarctic) between four continents, and it separates mainly flat areas on the continents that are convenient for human settlement and have long been developed by them;
the fact that large and medium-sized rivers flow into the ocean (Amazon, Congo, Niger, Mississippi, St. Lawrence, etc.), which served and serve as natural routes of communication;
the large ruggedness of the coastline of Europe, the presence of the Mediterranean Sea and the Gulf of Mexico, which contributed to the development of navigation and ocean exploration.
The Atlantic Ocean has several seas: the Baltic, Mediterranean, Black, Marble, Azov, Caribbean and 3 large bays: Mexico, Biscay and Guinea. The largest islands - Great Britain and Ireland - are located off the coast of Europe. Particularly large clusters of islands are located off the coast of Central America: the Greater and Lesser Antilles, the Bahamas; off the coast of South America - Falkland, in the southern part of the ocean - South Orkney and South Sandwich; off the coast of Africa - the Canaries, Cape Verde, Azores, Madeira, Principe, Sao Tome, etc. In the axial zone of the ocean are the islands of Iceland, Ascension, St. Helena, Tristan da Cunha, on the border with the Arctic Ocean - The largest island on Earth is Greenland.
The climates of the Atlantic are largely determined by its large meridional extent, the peculiarities of the formation of the pressure field, and the unique configuration (there are more water areas in temperate latitudes than in equatorial-tropical latitudes). On the northern and southern outskirts there are huge regions of cooling and the formation of centers of high atmospheric pressure. Constant areas of low pressure in subequatorial and temperate latitudes and high pressure areas in subtropical latitudes are also formed over the ocean.
These are the Equatorial and Antarctic depressions, the Icelandic minimum, the North Atlantic (Azores) and South Atlantic maximums 1.
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. 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 moist, 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.
1.2.Bottom topography
The Mid-Atlantic Ridge runs across the entire ocean (at approximately equal distances from the continental coasts) (Fig. 2).The outlines of the shores of the Atlantic Ocean are extremely remarkable. If Africa and South America, Europe and North America are moved close to each other on the map, so that their coastlines coincide, then the contours of the continents will converge, like two halves of a torn ruble. This coincidence in the outlines of the coasts led some scientists to a rather simple and original conclusion that the listed continents used to form a single supercontinent, in which a giant crack arose under the influence of the Earth’s rotation. America separated from Europe and Africa and drifted along viscous deep rocks to the west, and the depression that formed between them filled with water and turned into the Atlantic Ocean.
Later, when it was established that a huge mountain system, the Mid-Atlantic Ridge, stretched from north to south in the Atlantic Ocean, it was not so easy to explain the origin of the Atlantic Ocean depression by the drift of America. The question arose: if America sailed from Africa, then where did the ridge 300-1500 kilometers wide, the peaks of which rise 1500-4500 meters above the ocean bed, come from between them? Maybe there was no continental drift? Maybe the waves of the Atlantic are walking over the flooded continents? This is precisely the opinion held by most geologists.
But the more information accumulated about the structure of the mysterious ridge, the details of the bottom topography and the rocks composing it, the clearer the complexity and seriousness of the problem became to scientists. This was further aggravated by the fact that the scientific data obtained often gave rise to contradictory judgments.
In the process of studying the ocean, it turned out that along the axis of the Mid-Atlantic Ridge there runs a deep valley - a crack that cuts the ridge along almost its entire length. Such valleys usually arise under the influence of tectonic extensional forces and are called rift valleys. They are zones of active manifestation of tectonics, seismicity and volcanism in the geological history of the Earth. The discovery of a rift valley on the ocean floor was reminiscent of a giant crack in a hypothetical supercontinent and continental drift. However, this new information and, above all, the relief features of the ridge required a different explanation of the mechanism of continental drift.
Schematically, the Mid-Atlantic Ridge is now represented as a symmetrical mountain structure, where the axis of symmetry is the rift valley. It is interesting that earthquakes occurring in the Atlantic Ocean are mostly associated with the Mid-Atlantic Ridge, and most of them are confined to the rift valley. Examining the relief of the ridge and pieces of rocks raised from the bottom, scientists noticed a pattern that surprised them in the geological structure of this mountain structure, namely: the further - be it to the west or east - from the rift valley, the older the bottom topography and the more ancient the mountain rocks become rocks that make up the mysterious underwater mountainous country. Thus, basalt rocks recovered by geologists from the crest of a ridge and from a rift valley, as a rule, are several hundred thousand years old; some basalt samples are several million years old, but not more than five million. In geological terms, these rocks are young. On the flanks of the ridge the basalts are much older than on the ridge; their age reaches 30 million years or more. Even further from the axis of symmetry, closer to the continents, the age of rocks raised from the ocean floor is determined to be 70 million years. It is important to note that no rocks older than 100 million years have been found in the Atlantic Ocean, while on land the oldest rocks are more than three billion years old.
The given information about the age of ocean rocks allows us to consider the Mid-Atlantic Ridge as a fairly young rock formation, which continues to develop and change to this day.
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. There are high positive air temperatures here all year round. The most severe climate is found in sub-Antarctic and Antarctic latitudes, and to a lesser extent in subpolar and northern latitudes.
CHAPTER 2. NATURAL RICHES OF THE ATLANTIC OCEAN
2.1.Waters and their properties
The zoning of water masses in the ocean is complicated by the influence of land and sea currents. This is manifested primarily in the temperature distribution of surface waters. In many areas of the ocean, isotherms off the coast deviate sharply from the latitudinal direction.The northern half of the ocean is warmer than the southern half, the temperature difference reaches 6°C. The average surface water temperature (16.5°C) is slightly lower than in the Pacific Ocean. The cooling effect is exerted by the waters and ice of the Arctic and Antarctic.
In subequatorial 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 picture of surface currents in the North Atlantic is much more complex than in the southern part of the 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, its depth is 700 m, and the current speed is 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 m 3 /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 (Fig. 2). This mysterious area of almost stagnant water lies in the southwestern part of the North Atlantic, between Bermuda and the West Indies. This sea got its name from the Portuguese word “saggaco”, which means “seaweed”. Almost stagnant, but clean and warm water is inhabited by sargassum algae, which are able to live and reproduce afloat (Fig. 3). Thanks to them, conditions here are more reminiscent of a tidal zone rather than an open ocean. Microscopic plankton do not live here because the water temperature is too high.
2.2.Flora
Ocean vegetation is very diverse. Phytobenthos (bottom vegetation) occupies about 2% of the bottom area and is distributed on the shelf to a depth of 100 m. It is represented by green, brown, red algae and some higher plants. The tropical ocean zone has a high species diversity, but a small amount of biomass compared to cold and temperate geographic zones. The northern littoral zone is characterized by brown algae, and the sublittoral zone by kelp. Red algae and some types of sea grass are found. Green algae are very common in the tropical zone. Various types of sea lettuce are the largest in size. Among the red algae, porphyry, rhodolinia, chaidrus, and ahnfeltia are widely represented. For many animals, a unique biotope is formed by free-floating sargassum algae, typical of the Sargasso Sea. Of the brown algae in the sublittoral zone in the northern part of the ocean, giant representatives of Macrocystis are characteristic. Phytoplankton, unlike phytobenthos, develops throughout the entire body of water. In the cold and temperate zones of the ocean it is concentrated at a depth of up to 50 m, and in the tropical zone - up to 80 m. It is represented by 234 species. Important representatives of phytoplankton are silicon algae, characteristic of temperate and circumpolar regions. In these areas, silicon algae represent more than 95% of the total phytoplankton. Near the equator the amount of algae is insignificant. The mass of phytoplankton ranges from 1 to 100 mg/m3, and in the high latitudes of the Northern and Southern Hemispheres during the period of mass development (sea bloom) reaches 10 g/m3 or more.2.3.Fauna
The fauna of the Atlantic Ocean is rich and diverse. Animals inhabit the entire thickness of ocean water. The diversity of fauna increases towards the tropics. In polar and temperate latitudes they number thousands of species, in tropical latitudes - tens of thousands.Temperate and cold waters are inhabited by large marine mammals - whales and pinnipeds, fish - herring, cod, perch and flounder; in zooplankton there is a sharp predominance of copepods and sometimes pteropods. There is great similarity between the faunas of the temperate zones of both hemispheres. More than 100 species of animals are bipolar, that is, they live only in cold and temperate zones, these include seals, fur seals, whales, sprat, sardines, anchovies, and many invertebrates, including mussels. The tropical waters of the Atlantic Ocean are characterized by: sperm whales, sea turtles, crustaceans, sharks, flying fish, crabs, coral polyps, scyphoid jellyfish, siphonophores, radiolarians. There are also many dangerous inhabitants: sharks, barracudas, moray eels. There are urchin fish and invertebrate sea urchins, the pricks of which are very painful.
The world of corals is very unique, but the coral structures of the Atlantic are insignificant in comparison with the Pacific Ocean. At a depth of about 4 m off the coast of Cuba, a “sea fan” coral lives, which has the appearance of burdock-shaped leaves penetrated by a network of vessels - this is the soft coral Gongonaria, forming entire thickets - “underwater forests”.
The deep-sea regions of the Atlantic, like other oceans, represent a special environment of enormous pressure, low temperatures and eternal darkness. Here you can find crustaceans, echinoderms, annelids, silicon sponges, and sea lilies.
In the Atlantic, there is also an “ocean desert” (“ocean Sahara”) - this is the Sargasso Sea, where the biomass value is no more than 25 mg/m 3, which is primarily due, apparently, to the special gas regime of the sea.
2.4. Minerals
A large number of offshore oil and gas fields have been discovered in the Atlantic Ocean and its seas and are being intensively developed. The richest offshore oil and gas areas in the world include: the Gulf of Mexico, the Maracaibo Lagoon, the North Sea, and the Gulf of Guinea, which are being intensively developed. Three large oil and gas provinces have been identified in the Western Atlantic: 1) from Davis Strait to the latitude of New York (industrial reserves near Labrador and south of Newfoundland); 2) on the Brazilian shelf from Cape Calcañar to Rio de Janeiro (more than 25 fields have been discovered); 3) in the coastal waters of Argentina from the Gulf of San Jorge to the Strait of Magellan. According to estimates, promising oil and gas areas make up about 1/4 of the ocean, and the total potential recoverable oil and gas resources are estimated at more than 80 billion tons. The largest iron ore deposit of Waubana is located off the east coast of the island of Newfoundland (total reserves are about 2 billion tons). Tin deposits are being developed off the coast of Great Britain and Florida. Heavy minerals (ilmenite, rutile, zircon, monazite) are mined off the coast of Florida, in the Gulf of Mexico. off the coast of Brazil, Uruguay, Argentina, the Scandinavian and Iberian Peninsulas, Senegal, South Africa. The shelf of South-West Africa is an area of industrial diamond mining (reserves of 12 million carats). Gold placers have been discovered off the Nova Scotia Peninsula. Phosphorites were found on the shelves of the USA, Morocco, Liberia, and on the Agulhas Bank. Diamond deposits were discovered off the coast of South-West Africa on the shelf in sediments of ancient and modern rivers. Ferromanganese nodules were found in bottom basins off the coasts of Florida and Newfoundland 2 . Coal, barite, sulfur, sand, pebbles and limestone are also mined from the seabed.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.
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.
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