Warm and cold currents of the Indian Ocean list. Features of the currents of the Indian Ocean in its southern part

The Indian Ocean is the third largest ocean on Earth, covering about 20% of its water surface. Its area is 76.17 million km², volume - 282.65 million km³. The deepest point of the ocean is located in the Sunda Trench (7729 m).

Area: 76,170 thousand km²
Volume: 282,650 thousand km³
Greatest depth: 7729 m
Average depth: 3711 m

In the north it washes Asia, in the west - Africa, in the east - Australia; in the south it borders on Antarctica. The border with the Atlantic Ocean runs along the 20° meridian of eastern longitude; from Quiet - along 146°55’ meridian of eastern longitude. The northernmost point of the Indian Ocean is located at approximately 30°N latitude in the Persian Gulf. The Indian Ocean is approximately 10,000 km wide between the southern points of Australia and Africa.

Etymology

The ancient Greeks called the western part of the ocean known to them with the adjacent seas and bays the Erythraean Sea (ancient Greek Ἐρυθρά θάλασσα - Red, and in old Russian sources the Red Sea). Gradually, this name began to be attributed only to the nearest sea, and the ocean was named after India, the country most famous at that time for its wealth on the ocean shores. So Alexander the Great in the 4th century BC. e. calls it Indicon pelagos (ancient Greek Ἰνδικόν πέλαγος) - “Indian Sea”. Among the Arabs, it is known as Bar el-Hind (modern Arabic: al-muhit al-hindiy) - “Indian Ocean”. Since the 16th century, the name Oceanus Indicus (Latin Oceanus Indicus) - Indian Ocean, introduced by the Roman scientist Pliny the Elder back in the 1st century, has been established.

Physiographic characteristics

General information

The Indian Ocean is mainly located south of the Tropic of Cancer between Eurasia to the north, Africa to the west, Australia to the east and Antarctica to the south. The border with the Atlantic Ocean runs along the meridian of Cape Agulhas (20° E to the coast of Antarctica (Donning Maud Land)). The border with the Pacific Ocean runs: south of Australia - along the eastern border of the Bass Strait to the island of Tasmania, then along the meridian 146°55’E. to Antarctica; north of Australia - between the Andaman Sea and the Strait of Malacca, further along the southwestern coast of the island of Sumatra, the Sunda Strait, the southern coast of the island of Java, the southern borders of the Bali and Savu seas, the northern border of the Arafura Sea, the southwestern coast of New Guinea and the western border of the Torres Strait . Sometimes the southern part of the ocean, with the northern border from 35° south. w. (based on the circulation of water and atmosphere) up to 60° south. w. (by the nature of the bottom topography) are classified as the Southern Ocean, which is not officially distinguished.

Seas, bays, islands

The area of the seas, bays and straits of the Indian Ocean is 11.68 million km² (15% of the total ocean area), the volume is 26.84 million km³ (9.5%). Seas and main bays along the ocean coast (clockwise): Red Sea, Arabian Sea (Gulf of Aden, Gulf of Oman, Persian Gulf), Laccadive Sea, Bay of Bengal, Andaman Sea, Timor Sea, Arafura Sea (Gulf of Carpentaria), Great Australian Gulf, Mawson Sea, Davis Sea, Commonwealth Sea, Cosmonaut Sea (the last four are sometimes referred to as the Southern Ocean).

Some islands - for example, Madagascar, Socotra, the Maldives - are fragments of ancient continents, others - Andaman, Nicobar or Christmas Island - are of volcanic origin. The largest island of the Indian Ocean is Madagascar (590 thousand km²). Largest islands and archipelagos: Tasmania, Sri Lanka, Kerguelen Archipelago, Andaman Islands, Melville, Mascarene Islands (Reunion, Mauritius), Kangaroo, Nias, Mentawai Islands (Siberut), Socotra, Groot Island, Comoros, Tiwi Islands (Bathurst ), Zanzibar, Simelue, Furneaux Islands (Flinders), Nicobar Islands, Qeshm, King, Bahrain Islands, Seychelles, Maldives, Chagos Archipelago.

History of the formation of the Indian Ocean

In Early Jurassic times, the ancient supercontinent Gondwana began to break apart. As a result, Africa with Arabia, Hindustan and Antarctica with Australia were formed. The process ended at the turn of the Jurassic and Cretaceous periods (140-130 million years ago), and the young depression of the modern Indian Ocean began to form. During the Cretaceous period, the ocean floor expanded due to the movement of Hindustan to the north and the reduction in the area of the Pacific and Tethys oceans. In the Late Cretaceous, the split of the single Australian-Antarctic continent began. At the same time, as a result of the formation of a new rift zone, the Arabian Plate broke away from the African Plate, and the Red Sea and the Gulf of Aden were formed. At the beginning of the Cenozoic era, the expansion of the Indian Ocean towards the Pacific stopped, but continued towards the Tethys Sea. At the end of the Eocene - beginning of the Oligocene, a collision of Hindustan with the Asian continent occurred.

Today, the movement of tectonic plates continues. The axis of this movement is the mid-ocean rift zones of the African-Antarctic Ridge, the Central Indian Ridge and the Australasian-Antarctic Rise. The Australian plate continues to move north at a speed of 5-7 cm per year. The Indian plate continues to move in the same direction at a speed of 3-6 cm per year. The Arabian plate is moving northeast at a speed of 1-3 cm per year. The Somali Plate continues to break away from the African Plate along the East African Rift Zone, which moves at a speed of 1-2 cm per year in a northeast direction. On December 26, 2004, the largest earthquake in the history of observations, with a magnitude of up to 9.3, occurred in the Indian Ocean off the island of Simeulue, located off the northwestern coast of the island of Sumatra (Indonesia). The reason was a shift of about 1200 km (according to some estimates - 1600 km) of the earth's crust over a distance of 15 m along the subduction zone, as a result of which the Hindustan Plate moved under the Burma Plate. The earthquake caused a tsunami, which brought enormous destruction and a huge number of deaths (up to 300 thousand people).

Geological structure and bottom topography of the Indian Ocean

Mid-ocean ridges

Mid-ocean ridges divide the floor of the Indian Ocean into three sectors: African, Indo-Australian and Antarctic. There are four mid-ocean ridges: the West Indian, Arabian-Indian, Central Indian and Australian-Antarctic Rise. The West Indian Ridge is located in the southwestern part of the ocean. It is characterized by underwater volcanism, seismicity, rift-type crust and the rift structure of the axial zone; it is cut by several oceanic faults of submeridional strike. In the area of Rodriguez Island (Mascarene archipelago) there is a so-called triple junction, where the ridge system is divided to the north into the Arabian-Indian Ridge and to the southwest into the Central Indian Ridge. The Arabian-Indian ridge is composed of ultramafic rocks; a number of transecting faults of submeridial strike have been identified, with which very deep depressions (ocean troughs) with depths of up to 6.4 km are associated. The northern part of the ridge is crossed by the most powerful Owen fault, along which the northern section of the ridge experienced a displacement of 250 km to the north. Further west the rift zone continues in the Gulf of Aden and to the north-northwest in the Red Sea. Here the rift zone is composed of carbonate sediments with volcanic ash. In the rift zone of the Red Sea, strata of evaporites and metal-bearing silts were discovered, associated with powerful hot (up to 70 °C) and very saline (up to 350 ‰) juvenile waters.

In the southwest direction from the triple junction extends the Central Indian Ridge, which has a well-defined rift and flank zones, ending in the south with the volcanic Amsterdam plateau with the volcanic islands of Saint-Paul and Amsterdam. From this plateau, the Australian-Antarctic Rise extends to the east-southeast, looking like a wide, weakly dissected arch. In the eastern part, the uplift is dissected by a series of meridional faults into a number of segments displaced relative to each other in the meridional direction.

African segment of the ocean

The underwater margin of Africa has a narrow shelf and a clearly defined continental slope with marginal plateaus and a continental foot. In the south, the African continent forms protrusions extended to the south: the Agulhas Bank, Mozambique and Madagascar ranges, composed of continental-type earth crust. The continental foot forms a sloping plain that expands to the south along the coasts of Somalia and Kenya, which continues into the Mozambique Channel and borders Madagascar on the east. The Mascarene Range runs along the east of the sector, in the northern part of which are the Seychelles Islands.

The surface of the ocean floor in the sector, especially along the mid-ocean ridges, is dissected by numerous ridges and troughs associated with submeridional fault zones. There are many underwater volcanic mountains, most of which are built on coral superstructures in the form of atolls and underwater coral reefs. Between the mountain uplifts there are basins of the ocean floor with hilly and mountainous terrain: Agulhas, Mozambique, Madagascar, Mascarene and Somalia. In the Somali and Mascarene basins, extensive flat abyssal plains have been formed, which receive a significant amount of terrigenous and biogenic sedimentary material. In the Mozambique Basin there is an underwater valley of the Zambezi River with a system of alluvial fans.

Indo-Australian ocean segment

The Indo-Australian segment occupies half the area of the Indian Ocean. In the west, in the meridional direction, the Maldives ridge runs, on the summit surface of which the islands of Laccadive, Maldives and Chagos are located. The ridge is composed of continental-type crust. Along the coasts of Arabia and Hindustan stretch a very narrow shelf, a narrow and steep continental slope and a very wide continental foot, mainly formed by two giant fans of turbidity flows of the Indus and Ganges rivers. These two rivers each carry 400 million tons of debris into the ocean. The Indus Cone extends far into the Arabian Basin. And only the southern part of this basin is occupied by a flat asbyssal plain with individual seamounts.

Almost exactly 90°E. The blocky oceanic East Indian Ridge stretches for 4000 km from north to south. Between the Maldives and East Indian ridges is the Central Basin, the largest basin in the Indian Ocean. Its northern part is occupied by the Bengal fan (from the Ganges River), the southern border of which is adjacent to the abyssal plain. In the central part of the basin there is a small ridge called Lanka and the Afanasy Nikitin underwater mountain. To the east of the East Indian Ridge are the Cocos and Western Australian basins, separated by the blocky sublatitudinal oriented Cocos uplift with the Cocos and Christmas islands. In the northern part of the Cocos Basin there is a flat abyssal plain. From the south it is bounded by the Western Australian Uplift, which abruptly breaks off to the south and gently plunges under the bottom of the basin to the north. From the south, the Western Australian Rise is limited by a steep scarp associated with the Diamantina fault zone. The ralom zone combines deep and narrow grabens (the most significant are Ob and Diamatina) and numerous narrow horsts.

The transitional region of the Indian Ocean is represented by the Andaman Trench and the deep-sea Sunda Trench, to which the maximum depth of the Indian Ocean is confined (7209 m). The outer ridge of the Sunda island arc is the underwater Mentawai Ridge and its extension in the form of the Andaman and Nicobar Islands.

The underwater edge of the Australian mainland

The northern part of the Australian continent is bordered by the wide Sahul shelf with many coral structures. To the south, this shelf narrows and widens again off the coast of southern Australia. The continental slope is composed of marginal plateaus (the largest of them are the Exmouth and Naturalist plateaus). In the western part of the Western Australian Basin there are the Zenith, Cuvier and other rises, which are pieces of the continental structure. Between the southern underwater margin of Australia and the Australian-Antarctic Rise there is a small South Australian Basin, which is a flat abyssal plain.

Antarctic ocean segment

The Antarctic segment is limited by the West Indian and Central Indian ridges, and from the south by the shores of Antarctica. Under the influence of tectonic and glaciological factors, the Antarctic shelf has been deepened. The wide continental slope is cut through by large and wide canyons, through which supercooled waters flow from the shelf into the abyssal depressions. The continental foot of Antarctica is distinguished by a wide and significant (up to 1.5 km) thickness of loose sediments.

The largest protrusion of the Antarctic continent is the Kerguelen Plateau, as well as the volcanic rise of Prince Edward and Crozet Islands, which divide the Antarctic sector into three basins. To the west is the African-Antarctic Basin, which is half located in the Atlantic Ocean. Most of its bottom is a flat abyssal plain. The Crozet Basin, located to the north, has a coarsely hilly bottom topography. The Australian-Antarctic Basin, which lies east of Kerguelen, is occupied by a flat plain in the southern part and abyssal hills in the northern part.

Bottom sediments

The Indian Ocean is dominated by calcareous foraminiferal-coccolithic deposits, occupying more than half of the bottom area. The widespread development of biogenic (including coral) calcareous deposits is explained by the location of a large part of the Indian Ocean within the tropical and equatorial belts, as well as the relatively shallow depth of the oceanic basins. Numerous mountain uplifts are also favorable for the formation of calcareous sediments. In the deep-sea parts of some basins (for example, Central, Western Australian) deep-sea red clays occur. The equatorial belt is characterized by radiolarian oozes. In the cold southern part of the ocean, where conditions for the development of diatom flora are especially favorable, siliceous diatom deposits are present. Iceberg sediments are deposited off the Antarctic coast. At the bottom of the Indian Ocean, ferromanganese nodules have become widespread, confined mainly to areas of deposition of red clays and radiolarian oozes.

Climate

In this region there are four climatic zones, stretched along parallels. Under the influence of the Asian continent, a monsoon climate is established in the northern part of the Indian Ocean with frequent cyclones moving towards the coasts. High atmospheric pressure over Asia in winter causes the formation of the northeast monsoon. In summer it is replaced by a humid southwest monsoon, carrying air from the southern regions of the ocean. During the summer monsoon, winds of more than force 7 (with a frequency of 40%) often occur. In summer, the temperature over the ocean is 28-32 °C, in winter it drops to 18-22 °C.

The southern tropics are dominated by the southeast trade wind, which in winter does not extend north of 10°N latitude. The average annual temperature reaches 25 °C. In the zone 40-45°S. Throughout the year, westerly transport of air masses is characteristic, especially strong in temperate latitudes, where the frequency of stormy weather is 30-40%. In the mid-ocean, stormy weather is associated with tropical hurricanes. In winter, they can also occur in the southern tropical zone. Most often, hurricanes occur in the western part of the ocean (up to 8 times a year), in the areas of Madagascar and the Mascarene Islands. In subtropical and temperate latitudes in summer the temperature reaches 10-22 °C, and in winter - 6-17 °C. Strong winds are typical from 45 degrees and south. In winter, the temperature here ranges from −16 °C to 6 °C, and in summer - from −4 °C to 10 °C.

The maximum amount of precipitation (2.5 thousand mm) is confined to the eastern region of the equatorial zone. There is also increased cloudiness here (more than 5 points). The lowest rainfall is observed in the tropical regions of the southern hemisphere, especially in the eastern part. In the northern hemisphere, clear weather is typical for most of the year in the Arabian Sea. Maximum cloudiness is observed in Antarctic waters.

Hydrological regime of the Indian Ocean

Surface water circulation

In the northern part of the ocean there is a seasonal change in currents caused by the monsoon circulation. In winter, the South-West Monsoon Current is established, starting in the Bay of Bengal. South of 10° N. w. this current turns into the Western Current, crossing the ocean from the Nicobar Islands to the coast of East Africa. Then it branches: one branch goes north to the Red Sea, the other goes south to 10° S. w. and, turning east, gives rise to the Equatorial Countercurrent. The latter crosses the ocean and, off the coast of Sumatra, is again divided into a part that goes into the Andaman Sea and the main branch, which between the Lesser Sunda Islands and Australia goes to the Pacific Ocean. In summer, the southeast monsoon ensures that the entire mass of surface water moves eastward, and the Equatorial Countercurrent disappears. The summer monsoon current begins off the coast of Africa with the powerful Somali Current, which is joined by a current from the Red Sea in the Gulf of Aden area. In the Bay of Bengal, the summer monsoon current is divided into northern and southern, which flows into the South Trade Wind Current.

In the southern hemisphere, currents are constant, without seasonal fluctuations. Driven by trade winds, the Southern Trade Wind Current crosses the ocean from east to west towards Madagascar. It intensifies in winter (for the southern hemisphere) due to additional supply from the Pacific Ocean waters flowing along the northern coast of Australia. Near Madagascar, the Southern Trade Wind Current branches, giving rise to the Equatorial Countercurrent, the Mozambique and Madagascar Currents. Merging southwest of Madagascar, they form the warm Agulhas Current. The southern part of this current goes into the Atlantic Ocean, and part of it flows into the Western Winds. On the approach to Australia, the cold West Australian Current departs from the latter to the north. Local gyres operate in the Arabian Sea, the Bay of Bengal and the Great Australian Bay, and in the Antarctic waters.

The northern part of the Indian Ocean is characterized by a predominance of semi-diurnal tides. Tide amplitudes in the open ocean are small and average 1 m. In the Antarctic and subantarctic zones, the tidal amplitude decreases from east to west from 1.6 m to 0.5 m, and near the coast they increase to 2-4 m. Maximum amplitudes are observed between islands, in shallow bays. In the Bay of Bengal, the tidal range is 4.2-5.2 m, near Mumbai - 5.7 m, near Yangon - 7 m, near northwestern Australia - 6 m, and in the port of Darwin - 8 m. In other areas, the tidal range is about 1-3 m.

Temperature, water salinity

In the equatorial zone of the Indian Ocean, the surface water temperature is about 28 °C all year round in both the western and eastern parts of the ocean. In the Red and Arabian Seas, winter temperatures drop to 20-25 °C, but in summer the Red Sea sets maximum temperatures for the entire Indian Ocean - up to 30-31 °C. High winter water temperatures (up to 29 °C) are typical for the coasts of northwestern Australia. In the southern hemisphere, at the same latitudes in the eastern part of the ocean, the water temperature in winter and summer is 1-2° lower than in the western part. Water temperatures below 0°C in summer are observed south of 60°S. w. Ice formation in these areas begins in April and the thickness of fast ice reaches 1-1.5 m by the end of winter. Melting begins in December-January, and by March the waters are completely cleared of fast ice. Icebergs are common in the southern Indian Ocean, sometimes reaching north of 40° S. w.

The maximum salinity of surface waters is observed in the Persian Gulf and the Red Sea, where it reaches 40-41 ‰. High salinity (more than 36 ‰) is also observed in the southern tropical zone, especially in the eastern regions, and in the northern hemisphere also in the Arabian Sea. In the neighboring Bay of Bengal, due to the desalination effect of the Ganges runoff with the Brahmaputra and Irrawaddy, salinity is reduced to 30-34 ‰. Increased salinity correlates with zones of maximum evaporation and the least amount of precipitation. Low salinity (less than 34 ‰) is typical for Arctic waters, where the strong desalinating effect of melted glacial waters is felt. The seasonal difference in salinity is significant only in the Antarctic and equatorial zones. In winter, desalinated waters from the northeastern part of the ocean are transported by the monsoon current, forming a tongue of low salinity along 5° N. w. In summer this language disappears. In Arctic waters in winter, salinity increases slightly due to salinization of waters during the process of ice formation. From the surface to the bottom of the ocean, salinity decreases. Bottom waters from the equator to the Arctic latitudes have a salinity of 34.7-34.8 ‰.

Water masses

The waters of the Indian Ocean are divided into several water masses. In the part of the ocean north of 40° S. w. distinguish central and equatorial surface and subsurface water masses and underlying deep water masses (deeper than 1000 m). North to 15-20° S. w. The central water mass spreads. The temperature varies with depth from 20-25 °C to 7-8 °C, salinity 34.6-35.5 ‰. Surface layers north of 10-15° S. w. constitute an equatorial water mass with a temperature of 4-18 °C and a salinity of 34.9-35.3 ‰. This water mass is characterized by significant speeds of horizontal and vertical movement. In the southern part of the ocean, subantarctic (temperature 5-15 °C, salinity up to 34 ‰) and Antarctic (temperature from 0 to −1 °C, salinity due to melting ice drops to 32 ‰) are distinguished. Deep water masses are divided into: very cold circulation waters, formed by the descent of Arctic water masses and the influx of circulation waters from the Atlantic Ocean; South Indian, formed as a result of the subsidence of subarctic surface waters; North Indian, formed by dense waters flowing from the Red Sea and the Gulf of Oman. Below 3.5-4 thousand m, bottom water masses are common, forming from the Antarctic supercooled and dense salty waters of the Red Sea and the Persian Gulf.

Flora and fauna

The flora and fauna of the Indian Ocean are incredibly diverse. The tropical region is distinguished by the richness of plankton. The unicellular alga Trichodesmium (cyanobacteria) is especially abundant, due to which the surface layer of water becomes very cloudy and changes its color. The plankton of the Indian Ocean is distinguished by a large number of organisms that glow at night: peridines, some types of jellyfish, ctenophores, and tunicates. Brightly colored siphonophores are abundant, including poisonous physalia. In temperate and arctic waters, the main representatives of plankton are copepods, euphausids and diatoms. The most numerous fish of the Indian Ocean are coryphens, tunas, nototheniids and various sharks. Among reptiles there are several species of giant sea turtles, sea snakes, and among mammals there are cetaceans (toothless and blue whales, sperm whales, dolphins), seals, and elephant seals. Most cetaceans live in temperate and subpolar regions, where intensive mixing of waters creates favorable conditions for the development of planktonic organisms. Birds are represented by albatross and frigatebirds, as well as several species of penguins, inhabiting the coasts of South Africa, Antarctica and the islands lying in the temperate zone of the ocean.

The flora of the Indian Ocean is represented by brown (sargassum, turbinaria) and green algae (caulerpa). The calcareous algae lithothamnia and halimeda also develop luxuriantly, which participate together with corals in the construction of reef structures. In the process of activity of reef-forming organisms, coral platforms are created, sometimes reaching a width of several kilometers. Typical for the coastal zone of the Indian Ocean is the phytocenosis formed by mangroves. Such thickets are especially characteristic of river mouths and occupy significant areas in Southeast Africa, western Madagascar, Southeast Asia and other areas. For temperate and Antarctic waters, the most characteristic are red and brown algae, mainly from the fucus and kelp groups, porphyry, and gelidium. Giant macrocystis are found in the polar regions of the southern hemisphere.

Zoobenthos is represented by a variety of mollusks, calcareous and flint sponges, echinoderms (sea urchins, starfish, brittle stars, sea cucumbers), numerous crustaceans, hydroids, and bryozoans. Coral polyps are widespread in the tropical zone.

Ecological problems

Human activities in the Indian Ocean have led to the pollution of its waters and a reduction in biodiversity. At the beginning of the 20th century, some species of whales were almost completely exterminated, others - sperm whales and sei whales - still survived, but their numbers were greatly reduced. Since the 1985-1986 season, the International Whale Commission has imposed a complete moratorium on commercial whaling of any species. In June 2010, at the 62nd meeting of the International Whaling Commission, under pressure from Japan, Iceland and Denmark, the moratorium was suspended. The Mauritius dodo, destroyed by 1651 on the island of Mauritius, became a symbol of extinction and extinction of species. After it became extinct, people for the first time formed the idea that they could cause the extinction of other animals.

A great danger in the ocean is water pollution with oil and oil products (the main pollutants), some heavy metals and waste from the nuclear industry. The routes of oil tankers transporting oil from the Persian Gulf countries lie across the ocean. Any major accident can lead to an environmental disaster and the death of many animals, birds and plants.

Indian Ocean states

States along the Indian Ocean borders (clockwise):

South African Republic,
Mozambique,
Tanzania,
Kenya,
Somalia,
Djibouti,
Eritrea,
Sudan,
Egypt,
Israel,
Jordan,
Saudi Arabia,
Yemen,
Oman,
United Arab Emirates,
Qatar,
Kuwait,
Iraq,
Iran,
Pakistan,
India,
Bangladesh,
Myanmar,
Thailand,
Malaysia,
Indonesia,
East Timor,
Australia.

In the Indian Ocean there are island states and possessions of states outside the region:

Bahrain,
British Indian Ocean Territory (UK)
Comoros,
Mauritius,
Madagascar,
Mayotte (France),
Maldives,
Reunion (France),
Seychelles,
French Southern and Antarctic Territories (France),
Sri Lanka.

History of the study

The shores of the Indian Ocean are one of the areas where ancient peoples settled and the first river civilizations emerged. In ancient times, vessels such as junks and catamarans were used by people to sail under the monsoons from India to East Africa and back. The Egyptians, 3500 BC, conducted brisk maritime trade with the countries of the Arabian Peninsula, India and East Africa. The Mesopotamian countries made sea voyages to Arabia and India 3000 BC. From the 6th century BC, the Phoenicians, according to the Greek historian Herodotus, carried out sea voyages from the Red Sea across the Indian Ocean to India and around Africa. In the 6th-5th centuries BC, Persian merchants conducted maritime trade from the mouth of the Indus River along the eastern coast of Africa. At the end of the Indian campaign of Alexander the Great in 325 BC, the Greeks, with a huge fleet with a crew of five thousand, in difficult storm conditions, made a months-long voyage between the mouths of the Indus and Euphrates rivers. Byzantine merchants in the 4th-6th centuries penetrated into India in the east, and into Ethiopia and Arabia in the south. Beginning in the 7th century, Arab sailors began intensive exploration of the Indian Ocean. They perfectly studied the coast of East Africa, Western and Eastern India, the islands of Socotra, Java and Ceylon, visited the Laccadive and Maldives, the islands of Sulawesi, Timor and others.

At the end of the 13th century, the Venetian traveler Marco Polo, on his way back from China, passed through the Indian Ocean from the Strait of Malacca to the Strait of Hormuz, visiting Sumatra, India, and Ceylon. The journey was described in the “Book of the Diversity of the World,” which had a significant influence on sailors, cartographers, and writers of the Middle Ages in Europe. Chinese junks made trips along the Asian shores of the Indian Ocean and reached the Eastern shores of Africa (for example, the seven voyages of Zheng He in 1405-1433). An expedition led by the Portuguese navigator Vasco da Gama, circumnavigating Africa from the south, passing along the eastern coast of the continent in 1498, reached India. In 1642, the Dutch trading East India Company organized an expedition of two ships under the command of Captain Tasman. As a result of this expedition, the central part of the Indian Ocean was explored and it was proven that Australia is a continent. In 1772, a British expedition under the command of James Cook penetrated the southern Indian Ocean to 71° S. sh., and extensive scientific material on hydrometeorology and oceanography was obtained.

From 1872 to 1876, the first scientific oceanic expedition took place on the English sailing-steam corvette Challenger, new data were obtained on the composition of ocean waters, flora and fauna, bottom topography and soils, the first map of ocean depths was compiled and the first collection was collected deep sea animals. A round-the-world expedition on the Russian sail-screw corvette “Vityaz” in 1886-1889 under the leadership of oceanographer S. O. Makarov carried out large-scale research work in the Indian Ocean. A great contribution to the study of the Indian Ocean was made by oceanographic expeditions on the German ships Valkyrie (1898-1899) and Gauss (1901-1903), on the English ship Discovery II (1930-1951), and the Soviet expedition ship Ob ( 1956-1958) and others. In 1960-1965, under the auspices of the Intergovernmental Oceanographic Expedition under UNESCO, an international Indian Ocean expedition was carried out. It was the largest expedition ever to operate in the Indian Ocean. The oceanographic work program covered almost the entire ocean with observations, which was facilitated by the participation of scientists from about 20 countries in the research. Among them: Soviet and foreign scientists on the research ships “Vityaz”, “A. I. Voeikov", "Yu. M. Shokalsky", non-magnetic schooner "Zarya" (USSR), "Natal" (South Africa), "Diamantina" (Australia), "Kistna" and "Varuna" (India), "Zulfikvar" (Pakistan). As a result, valuable new data were collected on the hydrology, hydrochemistry, meteorology, geology, geophysics and biology of the Indian Ocean. Since 1972, regular deep-sea drilling, work to study the movement of water masses at great depths, and biological research have been carried out on the American vessel Glomar Challenger.

In recent decades, numerous measurements of the ocean have been carried out using space satellites. The result was a bathymetric atlas of the oceans released in 1994 by the American National Geophysical Data Center with a map resolution of 3-4 km and a depth accuracy of ±100 m.

Economic significance

Fisheries and marine industries

The importance of the Indian Ocean for global fisheries is small: catches here account for only 5% of the total. The main commercial fish in the local waters are tuna, sardines, anchovies, several species of sharks, barracudas and stingrays; Shrimp, lobster and lobster are also caught here. Until recently, whaling, which was intense in the southern regions of the ocean, is quickly curtailed due to the almost complete extermination of some species of whales. Pearls and mother-of-pearl are mined on the northwestern coast of Australia, Sri Lanka and the Bahrain Islands.

Transport routes

The most important transport routes in the Indian Ocean are routes from the Persian Gulf to Europe, North America, Japan and China, as well as from the Gulf of Aden to India, Indonesia, Australia, Japan and China. The main navigable straits of the Indian Strait are: Mozambique, Bab el-Mandeb, Hormuz, Sunda. The Indian Ocean is connected by the artificial Suez Canal to the Mediterranean Sea of the Atlantic Ocean. All the major cargo flows of the Indian Ocean converge and diverge in the Suez Canal and the Red Sea. Major ports: Durban, Maputo (export: ore, coal, cotton, minerals, oil, asbestos, tea, raw sugar, cashew nuts, import: machinery and equipment, industrial goods, food), Dar es Salaam (export : cotton, coffee, sisal, diamonds, gold, petroleum products, cashew nuts, cloves, tea, meat, leather, import: industrial goods, food, chemicals), Jeddah, Salalah, Dubai, Bandar Abbas, Basra (export: oil, grain, salt, dates, cotton, leather, import: cars, timber, textiles, sugar, tea), Karachi (export: cotton, fabrics, wool, leather, shoes, carpets, rice, fish, import: coal, coke, petroleum products , mineral fertilizers, equipment, metals, grain, food, paper, jute, tea, sugar), Mumbai (export: manganese and iron ores, petroleum products, sugar, wool, leather, cotton, fabrics, import: oil, coal, cast iron, equipment, grain, chemicals, industrial goods), Colombo, Chennai (iron ore, coal, granite, fertilizers, petroleum products, containers, cars), Kolkata (export: coal, iron and copper ores, tea, import: industrial goods, grain, food, equipment), Chittagong (clothing, jute, leather, tea, chemicals), Yangon (export: rice, hardwood, non-ferrous metals, cake, legumes, rubber, precious stones, import: coal, cars, food, fabrics) , Perth-Fremantle (export: ore, alumina, coal, coke, caustic soda, phosphorus raw materials, import: oil, equipment).

Minerals

The most important mineral resources of the Indian Ocean are oil and natural gas. Their deposits are located on the shelves of the Persian and Suez Gulfs, in the Bass Strait, and on the shelf of the Hindustan Peninsula. Ilmenite, monazite, rutile, titanite and zirconium are exploited on the coasts of India, Mozambique, Tanzania, South Africa, the islands of Madagascar and Sri Lanka. There are deposits of barite and phosphorite off the coast of India and Australia, and deposits of cassiterite and ilmenite are exploited on an industrial scale in the offshore zones of Indonesia, Thailand and Malaysia.

Recreational resources

The main recreational areas of the Indian Ocean: the Red Sea, the west coast of Thailand, the islands of Malaysia and Indonesia, the island of Sri Lanka, the coastal urban agglomerations of India, the east coast of the island of Madagascar, the Seychelles and the Maldives. Among the Indian Ocean countries with the largest flow of tourists (according to 2010 data from the World Tourism Organization) are: Malaysia (25 million visits per year), Thailand (16 million), Egypt (14 million), Saudi Arabia (11 million), South Africa (8 million), United Arab Emirates (7 million), Indonesia (7 million), Australia (6 million), India (6 million), Qatar (1.6 million), Oman (1.5 million).

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In the northern part of the ocean, the monsoon circulation causes seasonal changes in currents. In winter, the South-West Monsoon Current is established, originating in the Bay of Bengal. South of 10 N latitude. this current becomes the Western Current, crossing the ocean from the Nicobar Islands to the coast of eastern Africa, where it branches. One branch goes to the Red Sea, the other goes south to 10 S. latitude. and then, acquiring an eastern direction, it gives rise to the Equatorial Countercurrent. The latter crosses the ocean and, off the coast of Sumatra, branches again - part of the waters goes into the Andaman Sea, and the main branch goes between the Lesser Sunda Islands and the northern coast of Australia into the Pacific Ocean. In summer, the south-south monsoon ensures that the entire mass of surface water moves eastward, and the equatorial current weakens. The summer monsoon current begins off the coast of Africa with the powerful Somali Current, which is joined in the region of the Gulf of Aden by the current from the Red Sea. In the Bay of Bengal, the summer monsoon current forms a flow to the north, while the other part of the water goes south and flows into the South Trade Wind Current. In general, the current system in the Indian Ocean can be represented in the form of two main gyres. In winter (of the northern hemisphere), the northern gyre is distinguished, formed by the Monsoon, Somali and Equatorial currents. In the summer of the northern hemisphere, the Monsoon Current, which takes on the opposite direction, merges with the Equatorial Current and sharply strengthens it. As a result, the northern gyre is closed from the south by the South Trade Wind Current. The second, southern gyre is formed by the South Trade Wind, Madagascar, Agulhans, Western Winds and West Australian currents. Local gyres operate in the Arabian Sea, the Bays of Bengal and the Great Australian Bay, and in the Antarctic waters.

29. Salinity of surface waters of the World Ocean

Salinity is the total content of solid dissolved substances in 1 kg of sea water, expressed in ppm. The average salinity of the World Ocean is 34.71°/oo.

The average salinity of the sea is from 32 to 37%o on the surface and from 34 to 35 in the bottom layers. Salinity and temperature determine the density of water. The average density of sea water is more than 1, the highest is typical for the surface. waters in the tropics and beyond. at great depths, the latter circumstance is associated not so much with salinity as with the water temperature, which in the near-bottom layers is very low. High salinity is observed in surface waters of tropical latitudes, where evaporation greatly exceeds precipitation. Water with the highest salinity (up to 37.9°/oo) is formed in the Atlantic Ocean in the zone of the Azores anticyclone. In the equatorial zone of the oceans, where heavy rainfall is frequent, salinity is low (34-35°/oo). In temperate latitudes it is relatively equal to 34°/oo. The lowest salinity of ocean waters - up to 29 °/oo - is observed in the summer among melting ice in the Arctic Ocean. The salinity of deep and bottom waters in the oceans is approximately 34.5°/oo, and its distribution is determined by the circulation of the waters of the World Ocean. In coastal areas of the oceans with significant river flow (Amazon, St. Lawrence, Niger, Ob, Yenisei, etc.), salinity can be significantly less than the average salinity and equal only 15-20 °/oo. The salinity of waters in the Mediterranean seas can be either less or greater than the salinity of ocean waters. Thus, the salinity of surface waters in the Black Sea is 16-18°/oo, in the Azov Sea 10-12°/oo, and in the Baltic Sea 5-8°/oo. In the Mediterranean and Red Seas, where evaporation significantly exceeds precipitation, salinity reaches 39 and 42°/oo, respectively. Salinity, together with temperature, determines the density of sea water, which determines the draft of the ship, the propagation of sound in water and many other physical characteristics of water.

The passion for geography instilled by our teacher grew into a passion for knowing the whole world. There were only 2 lessons a week, the “Film Travel Club” was shown once a week, so I spent hours in the library reading room, where I quenched my thirst for geography. I also persuaded my father to subscribe to the magazine “Around the World”; by the way, I still carefully keep all the copies, and these are subscriptions for 20 (!) years.

Features of the currents of the Indian Ocean in its southern part

In this part of the ocean, its waters create a kind of circulation with their movement. This happens because warm and cold currents mix. Here are the huge masses of ocean waters involved in this process, what are the names and in what directions do these currents move:

South Passat (warm) to the North;
Madagascar (warm) to the West;
Needle (warm) to the West;
West winds (cold) to the South;
Western Australian (cold) to the East.

I note that this mainly happens in the winter months in the area between 3 and 8 degrees south latitude. This countercurrent is also called the equatorial or inter-trade current. And south of 55 degrees S. A number of water cycles develop (weaker), which close to the eastern current near the white continent.

Features of currents in the northern part of the ocean

Winds called monsoon winds have a huge influence on the movement of colossal volumes of water masses; by the way, this is why the local currents are usually called monsoon. This occurs north of 100 degrees N, and an interesting fact is that these currents reverse direction twice a year: in the summer they are northeastern and eastern, and in winter they are southwestern and western. They reach very high speeds - more than 130 km/h.

It is necessary to add a small but very significant note. The fact is that ocean currents are significantly affected by the waters of both the Red Sea and, of course, the Persian Gulf. Depending on the time of year, their influence is expressed in the strengthening or weakening of the currents described above.

The Indian Ocean is an integral part of the world ocean. Its maximum depth is 7729 m (Sunda Trench), and its average depth is just over 3700 m, which is second only to the depths of the Pacific Ocean. The size of the Indian Ocean is 76.174 million km2. This is 20% of the world's oceans. The volume of water is about 290 million km3 (together with all the seas).

The waters of the Indian Ocean are light blue in color and have good transparency. This is due to the fact that very few freshwater rivers flow into it, which are the main “troublemakers.” By the way, due to this, the water in the Indian Ocean is much saltier compared to the salinity levels of other oceans.

Location of the Indian Ocean

Most of the Indian Ocean is in the Southern Hemisphere. It is bordered to the north by Asia, to the south by Antarctica, to the east by Australia and to the west by the African continent. In addition, in the southeast its waters connect with the waters of the Pacific Ocean, and in the southwest with the Atlantic Ocean.

Seas and bays of the Indian Ocean

The Indian Ocean does not have as many seas as other oceans. For example, in comparison with the Atlantic Ocean there are 3 times less of them. Most of the seas are located in its northern part. In the tropical zone there are: the Red Sea (the saltiest sea on Earth), the Laccadive Sea, the Arabian Sea, the Arafura Sea, the Timor Sea and the Andaman Sea. The Antarctic zone contains the D'Urville Sea, the Commonwealth Sea, the Davis Sea, the Riiser-Larsen Sea, and the Cosmonaut Sea.

The largest bays of the Indian Ocean are the Persian, Bengal, Oman, Aden, Prydz and Great Australian.

Indian Ocean Islands

The Indian Ocean is not distinguished by an abundance of islands. The largest islands of mainland origin are Madagascar, Sumatra, Sri Lanka, Java, Tasmania, Timor. Also, there are volcanic islands such as Mauritius, Regyon, Kerguelen, and coral islands - Chagos, Maldives, Andaman, etc.

The underwater world of the Indian Ocean

Since more than half of the Indian Ocean is located in the tropical and subtropical zones, its underwater world is very rich and diverse in species. The coastal zone in the tropics is replete with numerous colonies of crabs and unique fish - mudskippers. Corals live in shallow waters, and in temperate waters a variety of algae grow - calcareous, brown, red.

The Indian Ocean is home to dozens of species of crustaceans, mollusks and jellyfish. A fairly large number of sea snakes also live in ocean waters, among which there are poisonous species.

The special pride of the Indian Ocean is sharks. Its waters are plied by many species of these predators, namely tiger, mako, gray, blue, great white shark, etc.

Mammals are represented by killer whales and dolphins. The southern part of the ocean is home to several species of pinnipeds (fur seals, dugongs, seals) and whales.

Despite all the richness of the underwater world, seafood fishing in the Indian Ocean is rather poorly developed - only 5% of the world catch. Sardines, tuna, shrimp, lobsters, rays and lobsters are caught in the ocean.

1. The ancient name of the Indian Ocean is Eastern.

2. In the Indian Ocean, ships are regularly found in good condition, but without a crew. Where he disappears is a mystery. Over the past 100 years, there have been 3 such ships - the Tarbon, the Houston Market (tankers) and the Cabin Cruiser.

3. Many species of the underwater world of the Indian Ocean have a unique property - they can glow. This is what explains the appearance of luminous circles in the ocean.

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Currents:

Benguela Current- cold Antarctic current.

It arises south of the Cape of Good Hope as a branch of the Western Winds and heads north. Reaches the Namibian region in Africa.

West Australian Current- cold current in the southeastern part of the Indian Ocean. It flows off the western coast of Australia from south to north, representing the northern branch of the Western Winds current. In the tropical zone of the Southern Hemisphere, part of the Western Australian Current passes into the South Trade Wind Current, and part dissipates in the Timor Sea.

Current speed is 0.7-0.9 km per hour, salinity is 35.5-35.70 grams per liter. The water temperature along the current varies from 19 to 26 °C in February and from 15 to 21 °C in August.

Madagascar Current- warm surface current of the Indian Ocean on the eastern and southern coasts of the island of Madagascar; branch of the South Trade Wind Current.

Directed south and southwest at a speed of 2-3 km/hour. The average surface water temperature per year is up to 26 ° C. Water salinity is more than 35 ‰. In the southwest it partially connects with the warm current of Cape Agulhas.

Mozambique Current- warm surface current in the Mozambique Channel, in the western part of the Indian Ocean; branch of the South Trade Wind Current. Directed south, along the coast of Africa, where it turns into the Cape Agulhas Current.

Northern trade wind current- warm surface current in the Mozambique Channel, in the western part of the Indian Ocean; branch of the South Trade Wind Current. Directed south, along the coast of Africa, where it turns into the Cape Agulhas Current.

Speed up to 2.8 km/h (from November to April). The average surface water temperature per year is up to 25 ° C. Salinity is 35 ‰.

North Equatorial Current- warm sea current in the Pacific, Atlantic and Indian Oceans.

In the Pacific Ocean, the North Equatorial Current (North Trade Wind) arises as a result of a deflection of the California Current and flows between 10° and 20° north latitude in a westerly direction until it is deflected before the east coast of the Philippines and becomes the warm Kuroshio Current.

In the Atlantic Ocean it arises from the Canary Current and flows between 10° and 30° north latitude in a northwest direction, being one of the sources of the Gulf Stream.

In the Indian Ocean, the direction of the North Equatorial Current depends on the time of year. During the winter months, during which the rainy season falls from the northeast, it flows weakly in a westerly direction along the Equator. In the summer months, when the rains come from the southwest, the Somali Current intensifies, flowing in a northeasterly direction along the coast of Africa and turning east, bypassing India.

Somali Current-current in the Indian Ocean near the Somali Peninsula. The fastest current in the open ocean, can reach speeds of 12.8 km/h

Changes its direction with the seasons, caused by monsoon winds. During the summer monsoon (July - August), with a southwest wind, the flow reaches a width of about 150 km and a thickness of about 200 m. In summer, water rises from the depths along the eastern coast of Somalia. The water temperature sometimes drops to 13° (at the surface). In winter, the northeast monsoon interrupts the Somali Current and turns it to the southwest. The rise of water from the depths practically stops.

Cape Agulhas Current, or Agulhas Current- a warm western boundary current in the Southwest Indian Ocean, which is part of the westward South Equatorial Current. Mainly passes along the western coast of Africa. The current is narrow and fast (at the surface the speed can reach 200 cm/s).

Equatorial countercurrent- a powerful countercurrent in the interval between the Northern Trade Wind Current and the Southern Trade Wind Current, observed in the equatorial region around the entire globe in the Pacific, Atlantic and Indian oceans.

Surface intertrade countercurrents in the Atlantic, Pacific and Indian oceans have been known since the 19th century. These currents are directed eastwards against the prevailing winds and against the movement of the main surface currents. Inter-trade countercurrents are caused by the transverse unevenness of the prevailing winds (trade winds), therefore their speed and flow fluctuate significantly, even disappearing, depending on the strength and uniformity of the winds.

In the middle of the 20th century, subsurface and even deep countercurrents were discovered. Including powerful equatorial subsurface countercurrents: the Cromwell Current, the Pacific Current, and the Lomonosov Current in the Atlantic Oceans. Subsurface equatorial currents are driven by pressure gradients and move as a narrow flow eastward under the westward trade wind current.

During the period of weakening trade winds, subsurface countercurrents can “reach” the ocean surface and be observed as surface currents.

Southern Trade Wind Current- named after the prevailing winds in the area - trade winds blowing from east to west - a warm current in the World Ocean passing through southern tropical latitudes.

In the Pacific Ocean, it begins near the coast of South America, approximately in the area of the Galapagos Islands, and goes west to the shores of New Guinea and Australia.

The northern limit of the current varies from 1 degree north latitude in summer to 3 degrees south latitude in winter.

Near the western coast of the Pacific Ocean, the current divides into branches - part of the current turns east, flowing into the Equatorial Countercurrent. Another major branch of the current is the East Australian Current, which begins off the coast of Australia.