Geographic structure of the ocean. Lecture: The structure and water masses of the World Ocean Topic "Horizontal structure of the World Ocean waters"

(about 70%), consisting of a number of individual components. Any analysis of the structure of M.O. associated with component private structures of the ocean.

Hydrological structure of MO.

Temperature stratification. In 1928, Defant formulated a theoretical position on the horizontal division of the MO into two water strata. The upper part is the oceanic troposphere, or "Warm Ocean" and the oceanic stratosphere, or "Cold Ocean". The border between them runs obliquely, varying from almost vertical to horizontal position. At the equator, the border is at a depth of about 1 km; in polar latitudes, it can run almost vertically. The waters of the "warm" ocean are lighter than polar waters and are located on them like on a liquid bottom. Despite the fact that there is a warm ocean almost everywhere and, therefore, the border between it and the cold ocean has a significant length, water exchange between them occurs only in very few places, due to the rise of deep waters (upwelling), or the lowering of warm waters (downwelling) ...

Geophysical structure of the ocean(the presence of physical fields). One of the factors of its presence is the thermodynamic exchange between the ocean and the atmosphere. According to Shuleikin (1963), the ocean should be considered as a heat engine operating in the meridional direction. The equator is the heater and the poles are the refrigerators. Due to the circulation of the atmosphere and ocean currents, there is a constant outflow of heat from the equator to the poles. The equator divides the oceans into two parts with partially separate systems of currents, and the continents divide the M.O. to the regions. Thus, oceanography subdivides MO into 7 parts: 1) Arctic, 2) North Atlantic, 3) North Indian, 4) North Pacific, 5) South Atlantic, 6) South Pacific, 7) South Indian.

In the ocean, as elsewhere in the geographic envelope, there are bordering surfaces (ocean / atmosphere, coast / ocean, bottom / water mass, cold / warm VM, saltier / less salty VM, etc.). It has been established that the greatest activity of the course of chemical processes occurs precisely on the boundary surfaces (Aizatulin, 1966). An increased field of chemical activity and physical anomalies is observed around each such surface. MOs are divided into active layers, the thickness of which, when approaching the boundary that generates them, decreases down to molecular, and the chemical activity and the amount of free energy increase as much as possible. If several borders are crossed, then all processes are even more active. The maximum activity is observed on the coasts, on the ice edge, on oceanic fronts (VMs of different origins and characteristics).

Most active:

1. the equatorial zone, where VMs of the northern and southern parts of the oceans contact, twisting in opposite directions (clockwise or counterclockwise).
2. contact zones of oceanic waters from different depths. In the areas of upwelling, the waters of the stratosphere rise to the surface, in which a large amount of mineral substances are dissolved, which are food for plants. In areas of downwellin, surface waters rich in oxygen sink to the ocean floor. In such areas, the biomass doubles.
3. areas of hydrothermal fluids (submarine volcanoes). Here, "ecological oases" based on chemosynthesis are formed. In them, organisms exist at temperatures up to + 400 and salinity up to 300 ‰. Here archaeobacteria were found dying at + 100 ° C from hypothermia and related to those that existed on Earth 3.8 billion years ago, bristle worms - living in solutions resembling sulfuric acid at a temperature of + 260 ° C.
4. river mouths.
5. straits.
6. underwater rapids

The least active are the central parts of the oceans, far from the bottom and shores.

Biological structure.

Until the mid 60s. it was believed that the ocean could feed humanity. But it turned out that only about 2% of the ocean's water masses are saturated with life. There are several approaches to characterizing the biological structure of the ocean.

1. The approach is associated with identifying clusters of life in the ocean. There are 4 static clusters of life: 2 films of life, surface and bottom, approximately 100 m thick and 2 thickening of life: coastal and Sargasso - an accumulation of organisms in the open ocean, where the bottom does not play any role, associated with the rise and fall of waters in the ocean, frontal zones in the ocean,

2. Zenkevich's approach is associated with the identification of symmetry in the ocean exists. There are 3 planes of symmetry in the phenomena of the biotic environment: equatorial, 2 meridional, passing through the center of the ocean and along the center of the continent, respectively. In relation to them, there is a change in biomass from the coast to the center of the ocean, the biomass decreases. Latitudinal belts in the ocean are distinguished in relation to the equator.

   1. the equatorial zone with a length of about 10 0 (from 5 0 N to 5 0 S) is a strip rich in life. There are a lot of species with a small number of each. Fishing is usually not very profitable.
   2. subtropical-tropical zones (2) - zones of oceanic deserts. Quite a lot of species live, phytoplankton is active all year round, but the bioproductivity is very low. The maximum number of organisms lives on coral reefs and in mangroves (coastal vegetation formations submerged in water).
   3. zones of temperate latitudes (2 zones) have the highest bioproductivity. Species diversity in comparison with the equator sharply decreases, but the number of individuals of one species increases sharply. These are areas of active fishing. 4) polar zones - areas with minimal biomass due to the fact that photosynthesis of phytoplankton stops in winter.

3. Environmental classification. Allocate ecological groups of living organisms.

   1. plankton (from the Greek. Planktos - wandering), a set of organisms that live in the water column and are unable to resist the transfer of the current. It consists of bacteria, diatoms and some other algae (phytoplankton), protozoa, some coelenterates, molluscs, crustaceans, fish eggs and larvae, invertebrate larvae (zooplankton).
   2. nekton (from the Greek. nektos - floating), a set of actively swimming animals living in the water column, capable of resisting the current and moving long distances. Nekton includes squids, fish, sea snakes and turtles, penguins, whales, pinnipeds, etc.
   3. benthos (from the Greek. benthos - depth), a set of organisms that live on the ground and in the bottom of the bottom of water bodies. Some of them move along the bottom: starfish, crabs, sea urchins. Others attach to the bottom - corals, scallops, algae. Some fish swim at the bottom or lie on the bottom (stingrays, flounder), they can bury themselves in the ground.
   4. There are also other, smaller ecological groups of organisms: Pleiston - organisms floating on the surface; neuston - organisms that attach to the water film from above or below; hyponeuston - live directly under the water film.

Several features are distinguished in the structure of the geographic envelope of MO:

1. Unity of MO
2. Circular structures are distinguished within the MO structure.
3. The ocean is anisotropic, i.e. transmits the influence of adjoining surfaces at different speeds in different directions. A drop of water moves from the surface of the Atlantic Ocean to the bottom for 1000 years, and from east to west from 50 days to 100 years.
4. The ocean has vertical and horizontal zoning, which leads to the formation of lower internal boundaries within the ocean.
5. Significant sizes of the MC shift the lower boundary of the GO in it to 11 km depth.

There are significant difficulties in analyzing a single geographic ocean environment.

1. low accessibility for humans;
2. difficulties in developing techniques for studying the ocean;
3. a short period of time in which the ocean is being studied.

Reasons for disturbing the balance: Currents Ebb and flow Changes in atmospheric pressure Wind Coastline Water runoff from land

The World Ocean is a system of communicating vessels. But their level is not always and not everywhere the same: at one latitude higher near the western shores; on one meridian rises from south to north

Circulation systems Horizontal and vertical transfer of water masses takes place in the form of a vortex system. Cyclonic vortices - the mass of water moves counterclockwise and rises. Anticyclonic eddies - the mass of water moves clockwise and descends. Both motions are generated by frontal disturbances of the atmosphere.

Convergence and divergence Convergence is the convergence of water masses. The ocean level is rising. The pressure and density of the water increases and it sinks. Divergence is the divergence of water masses. The ocean level is dropping. Deep water rises. http: // www. youtube. com / watch? v = dce. MYk. G 2 j. Kw

Vertical stratification Upper sphere (200-300 m) A) upper layer (several micrometers) B) layer of wind action (10-40 m) C) layer of temperature jump (50-100 m) D) layer of penetration of seasonal circulation and temperature variability Ocean currents capture only the water masses of the upper sphere.

Deep sphere Does not reach the bottom for 1000 m.

The structure of the World Ocean is called its structure - vertical stratification of waters, horizontal (geographic) zonation, the nature of water masses and oceanic fronts.

Vertical stratification of the World Ocean. In a vertical section, the water column breaks up into large layers, similar to the layers of the atmosphere. They are also called spheres. The following four spheres (layers) are highlighted:

Upper sphere formed by direct exchange of energy and matter with the troposphere in the form of microcirculation systems. It covers a layer 200-300 m thick. This upper sphere is characterized by intense mixing, light penetration and significant temperature fluctuations.

Upper sphere splits into the following private layers:

a) the topmost layer several tens of centimeters thick;

b) a layer of wind impact with a depth of 10-40 cm; he participates in excitement, reacts to the weather;

c) the layer of the temperature jump, in which it falls sharply from the upper heated to the lower, unaffected by excitement and unheated layer;

d) a layer of penetration of seasonal circulation and temperature variability.

Ocean currents usually capture the water masses of only the upper sphere.

Intermediate sphere extends to depths of 1,500-2,000 m; its waters are formed from surface waters when they sink. At the same time, they are cooled and compacted, and then mixed in horizontal directions, mainly with a zonal component. Horizontal transfers of water masses predominate.

Deep sphere does not reach the bottom by about 1,000 m. This sphere is characterized by a certain homogeneity. Its thickness is about 2,000 m and it concentrates more than 50% of the entire water of the World Ocean.

Bottom sphere occupies the lowest layer of the ocean and extends to a distance of about 1,000 m from the bottom. The waters of this sphere are formed in cold zones, in the Arctic and Antarctic and move over vast areas along deep basins and trenches. They perceive heat from the bowels of the Earth and interact with the ocean floor. Therefore, during their movement, they are significantly transformed.

Water masses and ocean fronts of the upper ocean sphere. Water mass is a relatively large volume of water that forms in a certain area of ​​the World Ocean and has for a long time almost constant physical (temperature, light), chemical (gases) and biological (plankton) properties. The mass of water moves as a whole. One mass is separated from another by the ocean front.

The following types of water masses are distinguished:

1. Equatorial water masses limited by equatorial and subequatorial fronts. They are characterized by the highest temperature in the open ocean, low salinity (up to 34-32 ‰), minimum density, high oxygen and phosphate content.

2. Tropical and subtropical water masses are created in the areas of tropical atmospheric anticyclones and are limited from the temperate zones by the tropical northern and tropical southern fronts, and subtropical - by the northern temperate and northern southern fronts. They are characterized by high salinity (up to 37 ‰ and more), high transparency, poor nutrient salts and plankton. Ecologically, tropical water masses are ocean deserts.

3. Moderate water masses located in temperate latitudes and bounded from the poles by the Arctic and Antarctic fronts. They are distinguished by great variability of properties both in geographical latitudes and in seasons. Moderate water masses are characterized by an intense exchange of heat and moisture with the atmosphere.

4. Polar water masses The Arctic and Antarctic are characterized by the lowest temperature, the highest density, and the highest oxygen content. The waters of Antarctica are intensively immersed in the bottom sphere and supply it with oxygen.

Ocean currents. In accordance with the zonal distribution of solar energy over the planet's surface, both in the ocean and in the atmosphere, the same type and genetically related circulation systems are created. The old notion that ocean currents are caused solely by winds is not supported by the latest scientific research. The movement of both water and air masses is determined by the zonality common to the atmosphere and hydrosphere: uneven heating and cooling of the Earth's surface. From this, in some areas, ascending currents and a decrease in mass arise, in others, descending currents and an increase in mass (air or water). Thus, the impulse of movement is born. Transfer of masses - their adaptation to the field of gravity, the desire for uniform distribution.

Most macrocirculatory systems last all year round. Only in the northern part of the Indian Ocean do currents change following the monsoons.

In total, there are 10 large circulation systems on Earth:

1) North Atlantic (Azores) system;

2) North Pacific (Hawaiian) system;

3) the South Atlantic system;

4) South Pacific system;

5) Izhno-Indian system;

6) Equatorial system;

7) Atlantic (Icelandic) system;

8) Pacific (Aleutian) system;

9) Indian monsoon system;

10) Antarctic and Arctic system.

The main circulation systems coincide with the centers of action of the atmosphere. This community is genetic in nature.

The surface current deviates from the wind direction by an angle of up to 45 ° to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Thus, trade winds go from east to west, while trade winds blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The top layer can follow the wind. However, each underlying layer continues to deviate to the right (left) from the direction of movement of the overlying layer. In this case, the flow rate decreases. At some depth, the flow takes the opposite direction, which practically means its termination. Numerous measurements have shown that the currents end at depths of no more than 300 m.

In the geographic envelope as a system of a level higher than the oceanosphere, ocean currents are not only water flows, but also air mass transfer bands, directions of matter and energy exchange, migration routes of animals and plants.

The tropical anticyclonic systems of ocean currents are the largest. They stretch from one ocean coast to the other for 6-7 thousand km in the Atlantic Ocean and 14-15 thousand km in the Pacific Ocean, and along the meridian from the equator to latitude 40 °, for 4-5 thousand km. Stable and powerful currents, especially in the Northern Hemisphere, are mostly closed.

As in tropical atmospheric anticyclones, water moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. From the eastern shores of the oceans (western coasts of the mainland), surface water belongs to the equator, in its place rises from the depths (divergence) and compensates for cold water from temperate latitudes. This is how cold currents are formed:

Canary Cold Current;

California cold current;

Peruvian cold current;

Benguela Cold Current;

West Australian cold current, etc.

The speed of the currents is relatively low and amounts to about 10 cm / sec.

Jets of compensatory currents flow into the North and South Passat (Equatorial) warm currents. The speed of these currents is quite high: 25-50 cm / sec at the tropical periphery and up to 150-200 cm / sec near the equator.

Approaching the shores of the continents, the trade wind currents naturally deviate. Large waste streams are formed:

Brazilian current;

Guiana Current;

Antilles current;

East Australian Current;

Madagascar current, etc.

The speed of these currents is about 75-100 cm / sec.

Due to the deflecting action of the Earth's rotation, the center of the anticyclonic system of currents is displaced to the west relative to the center of the atmospheric anticyclone. Therefore, the transfer of water masses to temperate latitudes is concentrated in narrow strips near the western shores of the oceans.

Guiana and Antilles currents washed by the Antilles and most of the water flows into the Gulf of Mexico. The stock current of the Gulf Stream begins from it. Its initial section in the Florida Strait is called Florida current, the depth of which is about 700 m, width - 75 km, thickness - 25 million m 3 / sec. The water temperature here reaches 26 0 C. Having reached middle latitudes, the water masses partially return to the same system off the western coasts of the continents, and are partially involved in cyclonic systems of the temperate zone.

The equatorial system is represented by the Equatorial Countercurrent. Equatorial countercurrent formed as a compensation between the Tradewinds.

The cyclonic systems of temperate latitudes are different in the Northern and Southern Hemispheres and depend on the location of the continents. Northern cyclonic systems - Icelandic and Aleutian- are very extensive: from west to east they stretch for 5-6 thousand km and from north to south for about 2 thousand km. The circulation system in the North Atlantic begins with the warm North Atlantic Current. It often retains the name of the initial Gulf Stream... However, the Gulf Stream itself, as a stock current, continues no further than the New Foundland Bank. Starting from 40 0 ​​N water masses are drawn into the circulation of temperate latitudes and, under the influence of western transport and Coriolis force, are directed from the American shores to Europe. Due to the active water exchange with the Arctic Ocean, the North Atlantic Current penetrates into the polar latitudes, where cyclonic activity forms several gyres-currents Irminger, Norwegian, Svalbard, North Cape.

Gulf Stream in the narrow sense is called the stock current from the Gulf of Mexico to 40 0 ​​N., in the broad sense - the system of currents in the North Atlantic and the western part of the Arctic Ocean.

The second gyre is located off the northeastern coast of America and includes currents East Greenland and Labrador... They carry the bulk of the Arctic waters and ice into the Atlantic Ocean.

The circulation of the North Pacific Ocean is similar to that of the North Atlantic, but differs from it in a smaller water exchange with the Arctic Ocean. Stock current Kuroshio goes into North pacific going to Northwest America. Very often this system of currents is called the Kuroshio.

A relatively small (36 thousand km 3) mass of ocean water penetrates into the Arctic Ocean. The cold currents of the Aleutian, Kamchatka and Oyashio are formed from the cold waters of the Pacific Ocean, out of connection with the Arctic.

Circumpolar Antarctic System The Southern Ocean, respectively, the oceanicity of the Southern Hemisphere is represented by one current Westerly winds... This is the most powerful current in the World Ocean. It covers the Earth in a continuous ring in a belt from 35-40 to 50-60 0 S latitude. Its width is about 2,000 km, the thickness is 185-215 km3 / sec, and the speed is 25-30 cm / sec. To a large extent, this current determines the independence of the Southern Ocean.

The circumpolar current of the Western winds is not closed: branches branch out from it, flowing into Peruvian, Benguela, West Australian currents, and from the south, from Antarctica, the coastal Antarctic currents flow into it - from the Weddell and Ross Seas.

The Arctic system occupies a special place in the circulation of the waters of the World Ocean due to the configuration of the Arctic Ocean. Genetically, it corresponds to the Arctic baric maximum and the trough of the Icelandic minimum. The main current here is Western arctic... It moves water and ice from east to west across the entire Arctic Ocean to the Nansen Strait (between Svalbard and Greenland). Then it continues East Greenlandic and Labrador... In the east, in the Chukchi Sea, it separates from the Western Arctic Current Polar current going across the pole to Greenland and further to the Nansen Strait.

The circulation of the waters of the World Ocean is dissymmetric with respect to the equator. The dissymmetry of flows has not yet received a proper scientific explanation. The reason for it, probably, lies in the fact that the meridional transport dominates north of the equator, and the zonal transport in the Southern Hemisphere. This is also explained by the position and shape of the continents.

In inland seas, the circulation of water is always individual.

54. Sushi waters. Types of land waters

Atmospheric precipitation after falling on the surface of continents and islands is divided into four unequal and changeable parts: one evaporates and is carried further inland by atmospheric runoff; the second seeps into the soil and into the ground and for some time is retained in the form of soil and underground water flowing into rivers and seas in the form of groundwater; the third, in streams and rivers, flows into the seas and oceans, forming a surface runoff; the fourth turns into mountain or continental glaciers, which melt and drain into the ocean. Accordingly, there are four types of water accumulation on land: groundwater, rivers, lakes and glaciers.

55. Water runoff from land. Quantities characterizing the runoff. Runoff factors

The runoff of rain and melt water in small streams along the slopes is called planar or slope drain. Jets of slope runoff are collected in streams and rivers, forming channel, or linear called river , runoff ... Groundwater flows into rivers in the form ground or underground drain.

Full river runoff R formed from surface S and underground U: R = S + U ... (see Table 1). The total river runoff is 38,800 km 3, surface runoff is 26,900 km 3, groundwater flow is 11,900 km 3, glacial runoff (2500-3000 km 3) and groundwater runoff directly into the sea along the coastline is 2000-4000 km 3.

Table 1 - Water balance of land without polar glaciers

Surface runoff depends on the weather. It is unstable, temporary, poorly nourishing the soil, and often needs regulation (ponds, reservoirs).

Ground runoff occurs in soils. During the wet season, the soil absorbs excess water on the surface and in the rivers, and in the dry months the groundwater feeds the rivers. They ensure the constant flow of water in the rivers and the normal water regime of the soil.

The total volume and ratio of surface and groundwater runoff vary by zone and region. In some parts of the continents there are many rivers and they are full-flowing, the density of the river network is large, in others - the river network is sparse, the rivers are low-water or dry up altogether.

The density of the river network and the high water content of rivers is a function of the flow or water balance of the territory. The runoff as a whole is determined by the physical and geographical conditions of the area, on the account of which the hydrological and geographical method of studying land waters is based.

Quantities characterizing the runoff. Runoff from land is measured by the following quantities: runoff layer, runoff modulus, runoff coefficient and runoff volume.

The runoff is most clearly expressed layer , which is measured in mm. For example, on the Kola Peninsula, the runoff layer is 382 mm.

Drain module- the amount of water in liters flowing down from 1 km 2 per second. For example, in the Neva basin, the runoff module is 9, on the Kola Peninsula - 8, and in the Lower Volga region - 1 l / km 2 x s.

Runoff coefficient- shows what proportion (%) of atmospheric precipitation flows into rivers (the rest evaporates). For example, on the Kola Peninsula K = 60%, in Kalmykia only 2%. For the entire land mass, the average long-term runoff coefficient (K) is 35%. In other words, 35% of the annual rainfall flows into the seas and oceans.

Flowing water volume measured in cubic kilometers. On the Kola Peninsula, precipitation brings 92.6 km 3 of water per year, and 55.2 km 3 flows down.

Runoff depends on the climate, the nature of the soil cover, relief, vegetation, weathering, the presence of lakes and other factors.

Climate dependence of runoff. The role of climate in the hydrological regime of the land is enormous: the more precipitation and less evaporation, the more runoff, and vice versa. When the humidity is more than 100%, the runoff follows the amount of precipitation, regardless of the amount of evaporation. When humidification is less than 100%, the runoff decreases following evaporation.

However, the role of climate should not be overestimated to the detriment of the influence of other factors. If we recognize climatic factors as decisive, and the rest are insignificant, then we will be deprived of the opportunity to regulate the flow.

Dependence of runoff on soil cover. Soil and grounds absorb and accumulate (accumulate) moisture. The soil cover transforms atmospheric precipitation into an element of the water regime and serves as a medium in which the river runoff is formed. If the infiltration properties and water permeability of soils are low, then little water gets into them, more is spent on evaporation and surface runoff. Well-cultivated soil in a meter layer can store up to 200 mm of precipitation, and then slowly give it to plants and rivers.

Relief dependence of runoff. It is necessary to distinguish between the significance for the runoff of macro-, meso- and microreliefs.

Already from insignificant heights, the runoff is greater than from the adjacent plains. So, on the Valdai Upland, the runoff module is 12, and on the neighboring plains only 6 m / km 2 / s. Even more runoff in the mountains. On the northern slope of the Caucasus, it reaches 50, and in the western Transcaucasia - 75 l / km 2 / s. If there is no runoff on the desert plains of Central Asia, then in the Pamir-Alai and Tien Shan it reaches 25 and 50 l / km 2 / s. In general, the hydrological regime and water balance of mountainous countries is different from that of plains.

In the plains, the effect on the runoff of the meso- and micro-relief is manifested. They redistribute the stock and affect its rate. On flat areas of the plains, the runoff is slow, the soil is saturated with moisture, waterlogging is possible. On the slopes, the flat runoff turns into a linear one. Ravines and river valleys appear. They, in turn, accelerate runoff and drain the area.

Valleys and other depressions in the relief, in which water accumulates, supply the ground with water. This is especially important in areas of insufficient moisture, where soil and grounds are not soaked and groundwater is formed only when fed from river valleys.

Influence of vegetation on runoff. Plants increase evaporation (transpiration) and thus drain the area. At the same time, they reduce the heating of the soil and reduce evaporation from it by 50-70%. Forest litter has a high moisture capacity and increased water permeability. It increases the infiltration of precipitation into the ground and thereby regulates the runoff. Vegetation contributes to the accumulation of snow and slows down its melting, so more water seeps into the ground than from the surface. On the other hand, some of the rain is trapped by the foliage and evaporated before reaching the soil. Vegetation cover resists erosion, slows down runoff and transfers it from surface to underground. Vegetation maintains air humidity and thereby enhances inland moisture turnover and increases the amount of precipitation. It affects moisture circulation by changing the soil and its water intake properties.

The influence of vegetation is different in different zones. V.V.Dokuchaev (1892) believed that steppe forests are reliable and correct regulators of the water regime of the steppe zone. In the taiga zone, forests drain the terrain by more evaporation than in the fields. In the steppes, forest belts contribute to the accumulation of moisture by retention of snow and reducing runoff and evaporation from the soil.

The effect on the runoff of bogs in zones of excessive and insufficient moisture is different. In the forest zone, they are flow regulators. In the forest-steppe and steppes, their influence is negative; they suck in surface and ground waters and evaporate them into the atmosphere.

Weathering crust and runoff. Sandy and pebble deposits store water. Often, streams from remote places are filtered along them, for example, in deserts from the mountains. On massively crystalline rocks, all surface water flows down; on the shields, underground waters circulate only in cracks.

The importance of lakes for flow regulation. Large flowing lakes are one of the most powerful flow regulators. Large lake-river systems, such as the Nevskaya or St. Lawrence, have a very regulated runoff and this significantly differs from all other river systems.

Complex of physical and geographical factors of runoff. All of the above factors act together, affecting one another in an integral system of the geographic envelope, determine gross wetting of the territory ... This is the name of that part of atmospheric precipitation, which, minus the rapidly flowing surface runoff, seeps into the soil and accumulates in the soil cover and in the ground, and then is slowly consumed. Obviously, it is the gross moisture that has the greatest biological (plant growth) and agricultural (agriculture) significance. This is the most essential part of the water balance.

The vast expanses of salt water that stretch across the globe are called the World Ocean. It is an independent geographical object with a peculiar geological and geomorphological structure of its basin and shores, the specificity of the chemical composition of the waters, and the peculiarities of the physical processes taking place in them. All these components of the natural complex affect the economy of the World Ocean.

The structure and shape of the world's oceans

The part of the earth's crust hidden under the ocean waters has a certain internal structure and external forms. They are interconnected by the geological processes that create them, which at the same time are expressed in the structure and relief of the ocean floor.

The largest forms include the following: shelf, or continental shelf, - usually a shallow sea terrace, bordering the mainland and continuing it under water. Basically, it is a coastal plain flooded by the sea with traces of ancient river valleys and coastlines that existed at lower sea level positions than modern ones. The average depth of the shelf is about 130 m, but in some areas it reaches hundreds and even thousands of meters. The shelf width in the World Ocean varies from tens of meters to thousands of kilometers. In general, the shelf occupies about 7% of the area of ​​the World Ocean.

Continental slope - the slope of the bottom from the outer edge of the shelf to the depths of the ocean. The average slope of this bottom topography is about 6 °, but there are areas where its steepness increases to 20-30 °. Sometimes the continental slope forms sheer ledges. The continental slope is usually about 100 km wide.

The continental foot is a wide, sloping, slightly hilly plain located between the lower part of the continental slope and the oceanic bed. The width of the continental foot can reach hundreds of kilometers.

The ocean floor is the deepest (about 4-6 km) and most extensive (more than 2/3 of the entire area of ​​the World Ocean) area of ​​the ocean floor with a significantly dissected relief. Global mountain structures, deep-water depressions, abyssal hills and plains are noticeably expressed here. In all oceans, mid-oceanic ridges are clearly traced, giant swell-like structures of great length, forming longitudinal ridges, separated along axial lines by deep depressions (rift valleys), at the bottom of which there is practically no sedimentary layer.

The greatest depths of the World Ocean are found in deep-water trenches. In one of them (the Mariana Trench), the maximum - 11022 m - the depth of the World Ocean was noted.

The quantitative characteristic of the chemical composition of seawater is salinity - the mass (in grams) of solid mineral substances contained in 1 kg of seawater. 1 gram of salts dissolved in 1 kg of sea water is taken as a unit of salinity, and it is called ppm, denoting% o. The average salinity of the World Ocean is 35.00% o, but it varies widely across regions.

The physical properties of seawater, in contrast to distilled water, depend not only on and, but also on salinity, which especially strongly affects the density, the temperature of greatest density and the freezing point of seawater. The development of various physical processes taking place in the World Ocean largely depends on these properties.

The ocean is constantly in motion, which is caused by: space, atmospheric, tectonic, etc. The dynamics of ocean waters manifests itself in different forms and is carried out, in general, in the vertical and horizontal directions. Under the influence of the tidal forces of the Moon and the Sun, tides occur in the World Ocean - periodic increases and decreases in the ocean level and the corresponding horizontal, forward movements of water, called tidal currents. The wind blowing over the ocean disturbs the water surface, resulting in the formation of wind waves of various structures, shapes and sizes. Wave oscillations, in which particles describe closed or almost closed orbits, penetrate the subsurface horizons, mixing the upper and lower layers of water. In addition to excitement, the wind causes the movement of surface waters over long distances, thus forming ocean and sea currents. Of course, currents in the World Ocean are influenced not only by wind, but also by other factors. However, currents of wind origin play a very large role in the dynamics of ocean and sea waters.

For many areas of the World Ocean, upwelling is characteristic - the process of vertical movement of water, as a result of which deep waters rise to the surface. It can be caused by wind driven surface water from the coast. The most pronounced coastal rise of waters is observed off the western coasts of North and South America, Asia, Africa and Australia. The waters that have risen from the depths are colder than the surface waters, contain a large amount of nutrients (phosphates, nitrates, etc.), therefore, upwelling zones are characterized by high biological productivity.

It has now been established that organic life permeates the ocean waters from the surface to the deepest depths. All organisms that inhabit the oceans are divided into three main groups: plankton - microscopic algae (phytoplankton) and the smallest animals (zooplankton) that freely soar in ocean and sea waters; nekton - fish and marine animals that can actively move independently in the water; benthos are plants and animals that live on the ocean floor from the coastal zone to great depths.

The rich and diverse flora and fauna of the oceans and seas is not only classified by genera, species, habitats, etc., but also characterized by certain concepts that contain quantitative estimates of the fauna and flora of the World Ocean. The most important of them are biomass and biological productivity. Biomass is the amount expressed as their wet weight per unit area or volume (g / m 2, mg / m 2, g / m 3, mg / m 3, etc.). There are various characteristics of biomass. It is assessed either for the entire totality of organisms, or separately for the flora and fauna, or for certain groups (plankton, nekton, etc.) for the World Ocean as a whole. In these cases, the biomass values ​​are expressed in absolute weight units.

Biological productivity is the reproduction of living organisms in the World Ocean, which is largely analogous to the concept of "soil fertility".

The values ​​of biological productivity are determined by phyto- and zooplankton, which account for most of the products produced in the ocean. The annual production of unicellular plant organisms, due to the high rate of their reproduction, is many thousand times higher than the total stock of phytomass, while on land the annual production of vegetation is only 6% higher than its biomass. The exceptionally high rate of phytoplankton reproduction is an essential feature of the ocean.

So, the World Ocean is a kind of natural complex. It has its own physical and chemical characteristics and serves as a habitat for a variety of flora and fauna. The waters of the oceans and seas closely interact with the lithosphere (coast and bottom of the ocean), continental runoff and the atmosphere. These complex, unequal from place to place interconnections predetermine the various possibilities of economic activity in the World Ocean.

The world's oceans, covering 2/3 of the earth's surface, are a huge water reservoir, the mass of water in which is 1.4 kilograms or 1.4 billion cubic kilometers. Ocean water is 97% of all water on the planet.

The oceans are the future of humanity. Its waters are inhabited by numerous organisms, many of which are a valuable biological resource of the planet, and in the thickness of the earth's crust covered by the Ocean - most of all the mineral resources of the Earth.

In the conditions of a shortage of fossil raw materials and an incessant accelerated scientific and technological progress for half a century, when the explored deposits of natural resources on land are less and less economically profitable to develop, a person looks with hope to the vast territories of the Ocean.

The ocean, and especially its coastal zone, plays a leading role in supporting life on the Earth. Indeed, about 70% of the oxygen entering the planet's atmosphere is produced in the process of photosynthesis by plankton (phytoplankton). Blue-green algae that live in the oceans serve as a giant filter that purifies water in the process of its circulation. It receives polluted river and rainwater and, by evaporation, returns moisture to the continent in the form of pure atmospheric precipitation.

world ocean pollution resource

The entire World Ocean occupies 361 million square kilometers (about 71% of the entire surface of the Earth), with fresh water accounting for only 20 million square kilometers, and the total volume of the entire hydrosphere is 1390 million cubic meters. km, of which the actual waters of the Ocean - 96.4%.

The world's oceans are usually divided into separate oceans. Three of them, those that are crossed by the equator, usually do not cause doubts, you can only argue about the boundaries. Abroad, not everyone still recognizes the independence of the Arctic Ocean. Its most ardent defenders were in the 30s of the twentieth century. Soviet scientists, who rightly argued that this ocean, although small in size, is a completely independent water area. As for the Southern Ocean, it was previously signed on maps, but in the 20s it disappeared, it was divided between the Pacific, Atlantic and Indian. And only in the 60s, after several years of intensive research in Antarctica, it was again proposed to single it out as an independent one.

The sea is part of the World Ocean. The bay is also. Calling some water area a sea or a bay is a matter of purely tradition. Two water spaces close in size and similar in regime on different sides of the same peninsula are called one - the Arabian Sea, the other - the Bay of Bengal. The tiny Azov Sea is a sea, and two huge waters north and south of North America are called Hudson and Mexican bays. Count how many seas are allocated within one Mediterranean Sea. So there is no need to look for objective criteria for distinguishing seas and bays, even if they are called as it is customary.

Speaking of the straits, it is necessary to find out whether the students have learned well the difference between the concepts of connects and divides. For example, the Bosphorus Strait separates the Balkan Peninsulas and Asia Minor (if wider, then Europe and Asia) and connects the Black Sea with the Marmara Sea. The Strait of Dardanelles shares the same, but connects the Sea of ​​Marmara with the Aegean.

According to the physical and geographical features, which are expressed in the hydrological regime, separate oceans, seas, bays, bays and straits are distinguished in the World Ocean. The most widespread modern subdivision Ocean (World Ocean) is based on the idea of ​​morphological, hydrological and hydrochemical features of its water areas, to a greater or lesser extent isolated by continents and islands. The boundaries of the Ocean (World Ocean) are clearly expressed only by the coastal lines of the land washed by it; internal boundaries between separate oceans, seas and their parts are to some extent conditional. Guided by the specifics of physical and geographical conditions, some researchers also distinguish as a separate Southern Ocean with a boundary along the line of subtropical or subantarctic convergence or along latitudinal segments of mid-oceanic ridges.

In the Northern Hemisphere, water occupies 61% of the earth's surface, in the Southern - 81%. North of 81 ° N. sh. in the Arctic Ocean and approximately between 56 ° and 63 ° S. sh. Ocean waters (World Ocean) cover the earth in a continuous layer. According to the peculiarities of the distribution of water and land, the earth is divided into oceanic and continental hemispheres. The pole of the former is located in the Pacific Ocean, south-east of New Zealand; the latter, in the northeast of France. In the oceanic hemisphere, Ocean (World Ocean) waters occupy 91% of the area, in the mainland - 53%.