The least studied and, perhaps, the most interesting from a scientific point of view is the Southern or Antarctic Ocean. Before 2000, the concept " South ocean"was conditional - this is what oceanologists called the part of the world's oceans consisting of southern parts The Pacific, Atlantic and Indian oceans and washing the shores of Antarctica.
Study of the specifics of this part of the world ocean, associated with the unique hydrological regime of Antarctic waters between the convergence zone and northern shores Antarctica, which are united by the circumpolar current, the uniqueness of the shelf bottom, animals and flora, as well as its special influence on the planet’s climate, gave scientists reason to identify the fifth Southern or Antarctic Ocean in 2000.
The boundary of the Southern Ocean runs along the 60th parallel of south latitude and corresponds to the northern boundary of the Antarctic convergence zone and the unique bottom topography. Its area is 20,327 thousand square meters. km. and it is the fourth largest ocean on the globe. In his water part includes the Amundsen, Bellingshausen, Ross, Weddell seas, part of the Drake Passage, a small part of the Scottish Sea and others bodies of water Antarctica. The Southern Ocean's topography is mostly between 4,000 and 5,000 m deep, with minor shallow areas. Its continental shelf is extremely deep, narrow and lies at depths from 400 to 800 m. The deepest point of the Antarctic Ocean is the southern tip of the Sandwich Trench - 7,235 m.
The biggest ocean current in the world, which influences the formation and change of climate throughout the earth - the Antarctic polar current. It moves in east direction around Antarctica and carries 130 million cubic meters of water per second. This figure is a hundred times higher than the amount of water carried by all the rivers of the globe. The climate of the Southern Ocean is distinguished by its severity.
Fashionable direction of the 20-21 centuries - tours to Antarctica
The water temperature in the surface layers of the ocean varies from +10? C to -2? C. Due to the strong temperature contrast between the ice region and the open ocean, cyclonic storms are almost constantly observed here, moving around Antarctica in an easterly direction. The harsh cold winds blow much stronger here than anywhere else on the planet. IN winter time The Southern Ocean freezes to the 65th parallel south in the Pacific Ocean and to the 55th parallel in the Atlantic Ocean, and the surface temperature drops well below zero.
Roaring Forties...
Antarctic pack ice covers an average area of at least 2.6 million square kilometers in the month of March to a maximum of 18.8 million square kilometers in September, increasing approximately sevenfold during this time. They represent a huge reserve of the purest fresh water on the planet. Debris from ice shelves and continental glaciers form icebergs and floating ice. Some Antarctic icebergs can exist for 10 years or more.
Despite the harsh climatic conditions Southern Ocean, living life in Antarctic waters is rich and unique. The waters of the Southern Ocean are extremely rich in phyto- and zooplankton, primarily represented by krill. Krill is the basis of nutrition for many species of fish, cetaceans, penguins, squid, sponges, echinoderms, seals and other animals. Among the mammals that have adapted to living in such harsh conditions, penguins, fur seals, and seals should be noted. The waters of the Southern Ocean are a favorite habitat for many species of whales, such as blue whale, fin whale, sei whale, humpback whale. The species diversity of valuable species of oceanic fish, which are represented by the endemic families of nototheniids and white-blooded fish, is extremely rich.
Very peculiar invertebrate animals that live in the south ocean waters Oh. Special interest represent huge jellyfish, reaching a weight of up to 150 kilograms. Penguins are a symbol of Antarctica and the Southern Ocean. These peculiar birds, having a vertical body position, are represented by 17 species. They lead a semi-terrestrial lifestyle, feed on small crustaceans and fish in the water and cannot fly at all like their relatives.
The Southern Ocean, due to its very harsh climate, is still little studied and is of great interest to science and scientific discoveries. The secrets kept in the waters of the Southern Ocean will amaze humanity more than once with their discoveries and sensations.
General information. The ring of ocean waters washing Antarctica combines characteristic features separate ocean and well-defined natural features of the Atlantic, Pacific and Indian oceans.
A difficult issue in this situation is the issue of boundaries. In the south it is limited by the coast of the southern polar continent. Western and eastern border this ocean has not. According to modern scientifically based ideas, the northern border is considered to be the northern periphery of the Antarctic convergence line (a strip of convergence of relatively warm and cold surface waters) approximately 40-50° S. sh., which is close to the northern border of the Antarctic Circumpolar Current.
The main feature of this conditional geographical boundary Southern Ocean - its some changes in time and space in connection with interannual and interseasonal fluctuations in the position of the Antarctic convergence lines.
Within the designated boundaries, the area of the Southern Ocean is 86 million km (according to some sources, this is a controversial issue), the average depth is 3503 m, the greatest depth is 8264 m (South Sandwich Trench, Meteor). There are many islands of varying sizes scattered throughout the Southern Ocean, most of which have complex mountainous terrain. The seas are located on the southern periphery of the ocean. The Scotia Sea is unique. In the south, the seas are limited to the coast of Antarctica, and in the north they are open to the ocean.
Relief of the ocean floor. Based modern research geographical science, the continent and its surrounding waters lie mainly on the continental-oceanic Antarctic. Some sections of the bottom of the northern reaches of the Southern Ocean are located on other plates adjacent to the Pacific-South American plates, the Scotia Sea, etc. The features and topography of the Southern Ocean bottom are associated with this. All the main geomorphological forms are clearly expressed on the bottom; the shelf zone is characterized by a small width (on average 150 km). Only in the Ross Seas does its width reach 1000-1100 km. The average depth of the shelf zone reaches 200 m.
The continental slope off Antarctica, especially East End, dissected by steps and cut by an abundance of underwater canyons. In the Antarctic part, the continental slope is steep near the Pacific coast and relatively flat and weakly dissected near the Antarctic coast.
The ocean floor is characterized by a number of underwater ridges, small rises and basins. The largest ranges are the West Indian and Central Indian, within which the rift valleys. They are essentially the southern spurs of mid-ocean ridges.
Within the Southern Ocean there are the Australian-Antarctic, South Pacific and partially East Pacific rises. In the area of 60° south. w. There are large ocean basins: African-Antarctic (6787 m), Australian-Antarctic (6098 m) and Bellingshausen (5399 m).
In the general circulation of ocean waters, their vertical movement plays an important role. Between Eastern and Western currents due to their divergence (divergence), deep waters enriched with nutrients rise.
Over the continental slope within the Weddell Sea in winter, cooled and saline surface waters, being heavier, sink into the deeper layers. As a result of this phenomenon, relatively cold and salty bottom waters are formed. They spread east around Antarctica and north into the Atlantic, and where they mix with their waters.
Wind waves develop in ice-free areas of the Southern Ocean. It is strongest in winter between 40 and 60° S. w. Waves with a height of about 2 m predominate here, and during a storm they reach a height of 8-9 m. Near the Kerguelen Island (sector Indian Ocean) the highest are recorded - up to 35 m. Significant waves with wave heights of 4-6 m are noted west of the Drake Passage and in the area to the southwest. In summer, the strength of the waves weakens, the height of the waves decreases. Area 40-60° S. w. They are usually called the “roaring forties” and the “furious fifties”.
Tides in the Southern Ocean are celebrated everywhere, their largest values(about 8 m) are observed at southern shores. In other areas the value is 2-2.5 m.
Ice is one of the most characteristic features nature of the Southern Ocean. They exist all year round. During maximum development(September-October) ice covers an area of 18-19 million km2, and in summer time(January-February) - only 2-3 million km2.
Sea ice (fast ice and drifting ice), shelf ice and ice are found here. To the north of the fast ice there is drifting ice. The patterns and direction of their movement are determined by winds and currents.
Between the edge of the fast ice and the drifting ice there are flaw polynyas - large spaces clean water. The presence of shelf ice is associated with coastal strip shelf. This ice is of sedimentary origin; its continental edge is a continuation of the land cover. It lies completely on the ground. Average height shelf ice is 430 m, and above sea level it rises by 10 and sometimes by 50 m.
The presence of icebergs is the most significant feature of the Southern Ocean. They are formed as a result of the breaking off of coastal parts of continental and shelf ice under the influence of waves, swell and. According to available data, over 200,000 icebergs are found in the waters of the Southern Ocean every year. Their average length about 500 m, and the height is 50 m above sea level. Individual icebergs are up to 5 km long. The bulk of icebergs melt within 3-5 years. Largest quantity icebergs are found at a distance of 100-150 km from the coast. At a distance of up to 700 km they are quite rare. Under the influence of wind and current, icebergs drift into coastal zone Antarctica. As they drift over time, they are destroyed and take on bizarre shapes.
Organic life in the ocean. The presence of the Antarctic Circumpolar Current in the ocean determines the composition and distribution of organic life. Huge masses of ice limit life in the ocean, but nevertheless, the Antarctic seas can compete with many tropical areas of the World Ocean in the abundance and diversity of living organisms. The long existence of flora and fauna in a little changing environment (at least 5 million years) has led to the fact that organisms have adapted to harsh living conditions. Diatoms remain viable down to a temperature of -20 °C. Fish have developed adaptations for living in supercooled water, and the inhabitants of the lower surface of the fast ice use the ice as a shelter, where rich pastures of ice algae - regrowth - are formed.
The circumpolar position of the Southern Ocean is associated with sharp seasonal dynamics of the main condition for photosynthesis - . Under such conditions, a large amplitude is observed throughout the year quantitative changes phytoplankton and a shift in the flowering zone from the north, where spring begins earlier, to the south, where it is delayed. In low latitudes, two peaks of flowering have time to develop, and in high latitudes only one. In surface waters biological latitudinal zonation. The inhabitants of the bottom do not have such zoning, since in their development important role plays a role in the bottom topography and barriers that prevent the exchange of flora and fauna. In the Southern Ocean, phytoplankton is dominated by diatoms (about 180 species).
Blue-green algae make up a small number. In quantitative terms, diatoms also predominate, especially in high latitudes, where they are almost 100%. During the period of maximum flowering, the number diatoms reaches its largest concentration.
There is a clear relationship between the distribution of algae and the vertical stability of waters. In summer, a significant mass of algae is found in the surface 25-meter layer.
In the direction from south to north, the composition of phytoplankton changes: high-latitude cold-water species gradually disappear from the flora, being replaced by warm-water species.
Zooplankton in the waters of the Southern Ocean is represented by copepods (about 120 species), amphipods (about 80 species), etc., chaetognaths, polychaetes, ostracods, appendicularia and mollusks are of lesser importance. In quantitative terms, copepods are in first place, accounting for almost 75% of the zooplankton biomass of the Pacific and Indian sectors of the ocean. There are few copepods in the ocean sector, since wide use received euphausiids (krill).
The Southern Ocean, especially its Antarctic regions, is characterized by massive accumulations of krill (Antarctic crustaceans). The krill biomass in these areas reaches 2,200 million tons, which makes it possible to catch up to 50-70 million tons of krill annually. Here, krill is the main food source for baleen whales, seals, fish, cephalopods, penguins and tubenosed birds. Crustaceans feed on phytoplankton.
The number of zooplankton has two peaks during the year. The first is associated with the rise of overwintered species and is observed in surface waters. The second peak is characterized by the abundance of zooplankton throughout the entire thickness and is due to the emergence of a new generation. Both peaks appear in the form of two latitudinal bands of zooplankton concentration. This is the period when zooplankton blooms in summer. most of zooplankton passes into the upper layers and moves north, where noticeable accumulation occurs in the Antarctic convergence zone.
In winter, condensation is observed in the divergence area, where individuals from the deep gather. In winter, the maximum species abundance was noted at depths of 250-1000 m.
The question of the vertical distribution of zooplankton is complicated by the ability of many organisms to perform regular (daily, seasonal) migrations from one zone to another.
Phytobenthos and zoobenthos in the waters of the Southern Ocean amazes with its richness and diversity. The number of phytobenthos decreases from South America to Antarctica. If 300 species are known, in Kerguelen - 138, then off the coast of Antarctica there are from 20 to 40 species. Mainly predominate different kinds red algae. Brown algae reach gigantic sizes (Marcocystis - 80 and sometimes 90 m in length) with limited biomass.
Among the representatives of zoobenthos, filter feeders predominate, mainly sponges (300 species), polychaetes (300), bryozoans (320), brachiopods (15), mollusks (300), and echinoderms (320 species).
Biomass of zoobenthos in coastal areas averages up to 0.5 kg/m2, and in some places reaches 3 kg/m2 at depths of 20-50 m; there are no permanent inhabitants in the surface zone. The fauna is distributed unevenly along the coast. The decrease in biomass begins at a depth of 500 m. It should be noted that if in other areas of the World Ocean bottom line sublittoral is located at a depth of 200 m, then near Antarctica subtidal animals live at depths of 500-700 m. The greatest species diversity is characteristic to a depth of 200-300 m, fish - at depths of 200-500 m.
The Antarctic region of the Southern Ocean has a rich, unique fauna and many endemic species. The fauna is characterized by gigantism of many representatives (for example, among sponges).
Near the Kerguelen Island, the fauna is 5 times poorer than mainland areas. There are about 100 species of fish in the Southern Ocean. Among them, only 12 are bottom-dwelling, belonging to the nototenaceae family, and of commercial importance. White pike, grenadier, gray and marbled notothenia, and southern blue whiting are widely represented in the Antarctic sector. In the Indian sector of the ocean, the number of commercial fish is small. It is home to striped whitefish (icefish), gray and marbled notothenia. In the Pacific sector, the largest in area, southern blue whiting and New Zealand macroruno are found.
Mammals. The total number of whales in the Southern Ocean is estimated to be approximately over 500 thousand. Pinnipeds include the crabeater seal, leopard seal, southern elephant seal, Ross seal, Weddell seal and a number of others. Antarctic seals make up up to 56% of the global pinniped population.
Ornithofauna. Represented by 44 bird species total number 200 million individuals. Among them, 7 species of penguins account for 90% of the total biomass.
In particular, it is signed in the 3rd edition of the fundamental Atlas of the World and in other atlases published in the 21st century.
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There are 14 seas off the coast of Antarctica: Weddell, Scotch, Bellingshausen, Ross, Amundsen, Davis, Lazarev, Riiser-Larsen, King Haakon VII, Cosmonauts, Commonwealth, Mawson, D'Urville, Somov. The most important islands of the Southern Ocean: Kerguelen, South Shetland, South Orkney. The Antarctic shelf is submerged to a depth of 500 meters.
All seas washing Antarctica, except the Scotia and Weddell seas, are marginal. In the tradition accepted in most countries, they divide its coast into sectors as follows:
Seas of the Southern Ocean
Name Sector In whose honor is it named . Sea Lazarev 0-14° E. d. Riiser-Larsen Sea 14-34° E. d. Sea of Cosmonauts 34-45° E. d. Commonwealth Sea 70-87° E. d. International cooperation in Antarctica
Davis Sea 87-98° E. d. Mawson's Sea 98-113° E. d. Sea of D'Urville 136-148° E. d. Sea Somova 148-170° E. d. Sea of Rossa 170° E. Longitude - 158°W d. Amundsen Sea 100-123° W. d. Bellingshausen Sea 70-100° W. d. Sea Scotia 30-50° W. long., 55-60° S. w. Weddell Sea 10-60° W. long., 78-60° S. w. King Haakon's Sea VII 20° E. 67° S w. . Southern Ocean in cartography
The Southern Ocean was first identified in 1650 by the Dutch geographer Bernhard Varenius and included as not yet discovered by Europeans " southern mainland", and all areas above the Antarctic Circle.
Currently, the ocean itself continues to be considered a body of water, which is mostly surrounded by land. In 2000, the International Hydrographic Organization adopted a division into five oceans, but this decision was never ratified. IN current definition There are no oceans since 1953. There is no Southern Ocean.
IN Soviet tradition(1969), the Antarctic Convergence Zone ( northern border Antarctic surface waters), near 55° south latitude. In other countries the border is also blurred - latitude south of Cape Horn, border floating ice, Antarctic Convention Zone (area south of 60 degrees south latitude). The Australian Government considers the "Southern Ocean" to be the waters immediately south of the Australian continent.
In atlases and geographic Maps the name "Southern Ocean" was included until the first quarter of the 20th century. IN Soviet time this term was not used [ ], however, from the end of the 20th century he began to sign on maps published by Roscartography.
History of Southern Ocean exploration
XVI-XIX centuries
The first ship to cross the border of the Southern Ocean belonged to the Dutch; it was commanded by Dirk Geeritz, who sailed in the squadron of Jacob Magyu. In 1559, in the Strait of Magellan, Geeritz's ship, after a storm, lost sight of the squadron and went south. Having descended to 64° south latitude, it saw high ground- possibly the South Orkney Islands. In 1671, Anthony de la Roche discovered South Georgia; Bouvet Island was discovered in 1739; in 1772, the French naval officer Kerguelen discovered an island in the Indian Ocean named after him.
Almost simultaneously with Kerguelen's voyage, he set off from England on his first trip to Southern Hemisphere James Cook, and already in January 1773 his ships “Adventure” and “Resolution” crossed the Antarctic Circle at the meridian 37 ° 33 "E. After a difficult struggle with ice, it reached 67 ° 15" south latitude, where he was forced to turn north. In December of the same year, Cook again set off for the Southern Ocean; on December 8, he crossed the southern Arctic Circle at 150°6" west longitude and at the parallel 67°5" south latitude it was covered with ice, freed from which it went further south and, at the end of January 1774, reached 71°15" south latitude, 109°14" west longitude, southwest of Tierra del Fuego. Here an impenetrable wall of ice prevented him from going further. On his second voyage in the Southern Ocean, Cook crossed the Antarctic Circle twice. During both voyages he became convinced that the abundance ice mountains indicates the existence of a significant Antarctic continent. The difficulties of polar voyages were described by him in such a way that only whalers continued to visit these latitudes and the southern polar scientific expeditions stopped for a long time.
In 1819, the Russian navigator Bellingshausen, commanding the sloops of war "Vostok" and "Mirny", visited South Georgia and tried to penetrate deep into the Southern Ocean; for the first time, in January 1820, almost on the Greenwich meridian, he reached 69°21" south latitude; then, leaving the southern polar circle, Bellingshausen walked along it east to 19° east longitude, where he crossed it again and reached in February again almost the same latitude (69°6"). Further east, he rose only to the 62° parallel and continued his journey along the edge of the floating ice, then, on the meridian of the Balleny Islands, he reached 64°55", in December 1820, at 161° west longitude, he passed the southern polar circle and reached 67°15" south latitude, and in January 1821, between the meridians 99° and 92° west longitude, reached 69°53" south latitude; then, almost at the 81° meridian, discovered a high coast at 68°40" south latitude Peter I Island, and going further east, inside the Southern Arctic Circle - the coast of Alexander I Land. Thus, Bellingshausen was the first to complete a complete voyage around the South Arctic continent, open to them, almost all the time between latitudes 60° - 70°, on small sailing ships.
At the end of 1837, a French expedition, under the command of Dumont-D'Urville, consisting of two steam ships - "Astrolabe" ("L'Astrolabe") and "Zélée" ("La Zélée"), set off to explore Oceania, to check information Weddel and others. In January 1838, Dumont-D'Urville followed Weddel's path, but ice blocked his path at the parallel of 63° south latitude. South of the South Shetland Islands he saw a high coast called the Land of Louis Philippe; it later turned out that this land was an island, western shores which is called Trinity Land and Palmer Land. After wintering in Tasmania, on the way to the south, Dumont-D'Urville encountered the first ice and, after difficult navigation between them, on January 9, 1840, at latitudes 66° - 67°, almost on the Arctic Circle, and 141° east. D. saw a high mountainous coast. Dumont-D'Urville traced this land, called the Land of Adélie, along the Arctic Circle to the meridian of 134° east longitude. On January 17, at 65° south latitude and 131° east longitude, another coast was discovered, called the Clary Coast.
An American expedition, consisting of three ships: "Vincennes", "Peacock" and "Porpoise", under the command of Lieutenant Willis, set out from the Tierra del Fuego archipelago in February 1839 with the aim of trying to follow the Weddel route to the south, but it was met with the same insurmountable obstacles , like Dumont-D'Urville, and she was forced to return without much results to Chile (at the meridian of 103° west longitude she reached almost 70° south latitude and here she seemed to see land). In January 1840, American explorer Charles Wilkes went almost due south along 160° east longitude. Already at the parallel of 64°11" south latitude, the ice blocked his further path. Turning west and reaching the meridian 153°6" east longitude, at 66° south latitude, he saw a mountain 120 km away, which he named Ringold Knohl. Ross, who visited the area a little later, disputed Wilkes's discovery, but without reason. Honor of opening various parts Wilkes's land actually belongs to each of the three navigators - Wilkes, Dumont-D'Urville and Ross - separately. During January and February 1840, Wilkes traveled a considerable distance along the outskirts of the Antarctic continent and reached the meridian of 96° east longitude. During the entire voyage he was unable to land anywhere on the shore.
The third English expedition, under the command of James Clark Ross, to steam ships"Erebus" and "Terror" (Crozier was the commander of "Erebus"), were equipped to explore the southern polar countries in general. In August 1840, Ross was in Tasmania, where he learned that Dumont-D'Urville had just discovered the shores of the Terre Adélie; this led him to begin his research further east, on the meridian of the Balleny Islands. In December 1840, the expedition crossed the Antarctic Circle at the meridian 169°40"E and soon began fighting the ice. After 10 days, the ice strip was passed, and on December 31 (old style) they saw the high coast of Victoria Land, one of the highest mountain peaks which Ross named after the initiator of the expedition - Sabin, and the entire chain of mountains with a height of 2000 - 3000 m - the Admiralty Ridge. All the valleys of this chain were filled with snow and huge glaciers descending to the sea. Beyond Cape Adar, the coast turned to the south, remaining mountainous and inaccessible. Ross landed on one of the Possession Islands, at 71°56" south latitude and 171°7" east longitude, completely devoid of vegetation and inhabited by a mass of penguins who covered its shores with a thick layer of guano. Continuing his voyage further south, Ross discovered the islands of Kullman and Franklin (the latter at 76°8" south latitude) and saw the coast directly to the south and high mountain(Erebus volcano) with a height of 3794 meters, and a little to the east another volcano, already extinct, was noticed, called Terror, with a height of 3230 meters. The way forward to the south it was blocked by a coast that turned to the east and was bordered by a continuous vertical ice wall, up to 60 meters high above the water, descending, according to Ross, to a depth of about 300 meters. This ice barrier was distinguished by the absence of any significant depressions, bays or capes; its almost flat, vertical wall stretched for an enormous distance. Beyond the icy shore, to the south, the peaks of a high mountain range, going deep into the southern polar continent; she is named after Parry. Ross traveled from Victoria Land to the east about 840 km, and throughout this entire distance the nature of the ice coast remained unchanged. Finally, late time year forced Ross to return to Tasmania. On this voyage, he reached 78°4" south latitude, between meridians 173°-174° west longitude. On the second voyage, his ships on December 20, 1841 again crossed the Antarctic Circle and went south. At the beginning of February 1842, on meridian 165 ° west longitude, they reached more open sea and headed straight south, approaching the ice coast a little more east than in 1841. At 161°27" west longitude they reached 78°9" south latitude, that is, they approached south pole closer than anyone so far. Further voyage to the east was blocked solid ice(pack), and the expedition turned north. In December 1842, Ross made a third attempt to penetrate the south; this time he chose the path of Weddel and headed towards the Land of Louis Philippe. Going east, Ross, at the meridian of 8° west longitude, crossed the Arctic Circle and on February 21 reached 71°30" south latitude, 14°51 west longitude.
Almost 30 years later, the expedition on the corvette Challenger visited, among other things, the southern polar countries. Having visited Kerguelen Island, the Challenger headed south and reached 65°42" south latitude. At 64°18" south latitude and 94°47" east longitude, he determined a depth of 2380 meters, and although, according to Wilkes's map, the coast should have been only 30 kilometers away, it was not visible.
Climate and weather
Sea temperatures vary from approximately −2 to 10 °C. The cyclonic movement of storms eastward around the continent and is often intense due to the temperature contrast between the ice and open ocean. The ocean region from 40 degrees south latitude to the Antarctic Circle experiences the strongest average winds on Earth. In winter, the ocean freezes to 65 degrees south latitude in the Pacific sector and 55 degrees south latitude in the Atlantic sector, dropping surface temperatures well below 0 °C; in some coastal locations there are permanent strong winds leave coastline ice-free during the winter.
Icebergs can occur at any time of year throughout the Southern Ocean. Some of them are capable of reaching several hundred meters; smaller icebergs, their fragments and sea ice(usually 0.5 to 1 meter) also create problems for ships. The icebergs found are 6-15 years old, which suggests the simultaneous existence in the ocean waters of more than 200 thousand icebergs ranging in length from 500 meters to 180 km and a width of up to several tens of kilometers.
Sailors latitudes from 40 to 70 degrees south latitude, from the era sailing ships, are known as the "Roaring Forties", "Furious Fifties" and "Screaming Sixties" due to the bad weather, gale-force winds and big waves, formed due to the movement of air masses, which, flowing around Earth, do not encounter obstacles in the form of any noticeable land masses. Floating ice, especially between May and October, makes this area even more dangerous, and the region's remoteness from populated areas Earth makes search and rescue operations ineffective.
Life
Despite the harsh climate, the Southern Ocean is teeming with life.
Due to the circumpolar location of the Southern Ocean, there are sharp seasonal dynamics the most important condition photosynthesis - solar radiation. Under such conditions, a large amplitude of quantitative changes is observed throughout the year.
In 2000, the International Hydrographic Organization adopted a division into five oceans, separating the Southern Ocean from the Atlantic, Indian and Pacific. In its southern part, the boundaries between the three oceans are very arbitrary, while at the same time, the waters adjacent to Antarctica have their own specifics, and are also united by the Antarctic Circumpolar Current.
In Soviet and Russian tradition The Antarctic Convergence Zone (the northern limit of Antarctic surface waters) is considered the approximate boundary of the Southern Ocean. In other countries the border is also blurred - latitude south of the cape Horn, boundary of floating ice, Antarctic Convention zone (area south of 60 degrees south latitude).
This term appeared many times back in the 18th century, when systematic exploration of the region began.
Intense cyclonic activity has developed over the Southern Ocean. Most cyclones move from West to East. The air temperature in January off the coast of Antarctica does not exceed 0 °C (–6 °C in the Weddell and Ross Seas), at 50° S. latitude. increases to 7 °C in the Indian and Atlantic sectors and to 12 °C in the Pacific. In winter, the contrasts are even greater: in the coastal zone. the temperature drops to –20 °С (in the Weddell and Ross seas to –30 °С), and at 50° S. latitude. is 2-3 °C in the Atlantic and Indian sectors and 6-7 °C in the Pacific.
IcebergThe main feature of the Southern Ocean is the current of the Western Winds, which spreads throughout the entire thickness of the waters and transports them in an easterly direction. To the south of this current the Western Coastal Current is formed. Cold and dense water masses from the shores of Antarctica they flow along the ocean floor far to the North. The Southern Ocean ice cover is more developed in Western Hemisphere and varies greatly with the seasons: in September - October its area is 18-19 million km², and in January - February - only 2-3 million km². Average width of the drifting ice belt in November at 30° W. is 2000 km, at 170° W. - 1500 km, at 90-150° east. - 250-550 km.
Icebergs are constantly calving off the Antarctic Ice Sheet. At the same time, there are more than 200 thousand icebergs in the Southern Ocean, their environments. the length is 500 m, but there are giants up to 180 km long and several tens of kilometers wide. Icebergs are carried to the North and can be found even at 35-40° S. They exist in the ocean for an average of 6 years, but in some cases their age can exceed 12-15 years.
How deep do penguins swim?Despite the harsh climate, the Southern Ocean is rich in life. There are huge masses of phyto- and zooplankton, krill, sponges and echinoderms are abundant, and several families of fish, especially notothenia. Among the birds, petrels, skuas, and penguins are numerous. There are many whales in the ocean (blue whale, fin whale, sei whale, humpback whale, etc.) and seals (Weddell seal, crabeater seal, leopard seal, fur seal). Whaling is prohibited, but a lot of krill and fish are caught.