The hackneyed, but nevertheless true remark that our planet should not be called the Earth, but the Ocean, is widely known. In fact, the World Ocean occupies 361 million km2, or 71% of the entire surface of the planet. The most important global consequence of this ratio of land and sea is its influence on the water and heat balance of the Earth. About 10% of solar radiation absorbed by the ocean surface is spent on water heating and turbulent heat exchange between the surface layers of water and the lower atmosphere, the remaining 90% is spent on evaporation. Thus, evaporation from the ocean surface is both the main source of water in the global hydrological cycle and, due to the high latent heat of water evaporation, an important component of the global heat balance.
The mass of the ocean is 94% of the mass of the hydrosphere. The world ocean is the most important regulator of flows in the global hydrological cycle, its volume is large compared to any component of the cycle, the average duration of water exchange in the ocean is very significant, amounting to 3 thousand years.
The surface zone of the ocean (depth 0-200 m) has a very significant heat capacity and the largest thermal inertia among the geospheres. It plays a crucial role in shaping the current climate of the planet, its spatial distribution and temporal variability. The effect of wind on the upper water layer determines the main features of oceanic circulation in the surface zone. The circulation of the ocean provides a global redistribution of energy from the equatorial zones to the poles. The surface zone of the ocean is the most important component of the climate system, which takes an active part in the formation of the average annual climate, its changes from year to year, as well as its fluctuations on a scale of decades and centuries.
External influences on the ocean are carried out almost exclusively through the influence of the atmosphere on it, thanks to the flows of heat, fresh water and momentum at the surface of the ocean. Thus, the evolution of the climate and the evolution of the ocean are interrelated.
The deep zones of the ocean, to a much lesser extent than the surface zones, obey the law of geographical zonation, and more often and more recently they do not. The main deep and near-bottom water flows are formed in the polar regions and are initially directed towards the opposite poles (Fig. 15). Their greater or lesser participation in natural processes near the surface of the ocean and the change in the degree of this participation is the most important factor in changing the main features of the ecosphere.
Deep (depth 2000-4000 m) and near-bottom (deeper than 4000 m) zones of the World Ocean account for 64% of its total volume. The water temperature in these areas is 3°C or less. The average temperature of the entire mass of the World Ocean is only about 4 ° C due to the cold deep and bottom layers. The vertical circulation of oceanic waters, under the influence of the difference in water density due to differences in its temperature and salinity, causes the movement of water from the surface to the deep layers, where it can be isolated from atmospheric influences, retaining its heat reserve for millennia or more. The release or, conversely, the accumulation of such heat reserves can be decisive in long-term climate change.
The low temperature of the World Ocean and its enormous thermal inertia play an important paleogeographical role. The deep layers are not only a good heat regulator of the Earth system. Strengthening or weakening of heat transfer between the deep layers of the ocean and its surface apparently plays a decisive role in the deep and long-term transformations of the Earth's climate and, accordingly, in changes in its landscapes. At the same time, changes in the heat exchange between the deep masses of the ocean and the surface, as well as the distribution of surface currents, can change over decades, i.e. extremely fast, taking into account the size of the World Ocean, which can lead to an equally rapid change in the natural environment.
The world ocean is also a huge accumulator of substances, containing them in dissolved form in an amount of about 50 x 10 15 tons. (Recall that the average concentration of dissolved substances in sea water, or its salinity, is 35 g / l.) Water salinity changes in space, but its chemical composition (in % of the whole) remains constant. The annual influx of salts into the ocean is about seven orders of magnitude (107 times) less than their content in the ocean. This circumstance plays a significant role in the stabilization of biogeochemical cycles and the ecosphere as a whole.
The ocean contains about 4 x 10 ¹º tons of carbon in solution, in suspension and in living forms. On land, in living organisms, soils and decaying organic matter, carbon is about 20 times less. Physical and chemical conditions in the ocean and the interaction of marine biota with them predetermine the response of the ocean to changes in the concentration of carbon dioxide in the atmosphere. Carbon dioxide from the atmosphere dissolves in water or is absorbed from it by plankton during the formation of primary production (photosynthesis). This process needs sunlight, carbon dioxide in water, and dissolved nutrients (compounds of nitrogen, phosphorus, and other chemical elements). Nutrients are usually the limiting factor.
Primary production is formed in the upper, well-lit layers of water, where biogens come either from plankton dying off at the same depths, or from land and from the atmosphere. When plankton dies, carbon-containing residues sink into the cold deep layers of the ocean and to the bottom. In the end, this carbon at a considerable depth is converted by bacteria into a soluble inorganic form, and a small part of it is deposited in the form of bottom sediments.
This process, sometimes called the "biological pump", is extremely complex. The biological pump reduces the concentration of carbon dioxide in the upper layer of the ocean, as well as in the atmosphere, and increases the total carbon content in the deep and near-bottom zones of the ocean. Bio-geo-chemical processes associated with the absorption of carbon dioxide occur mainly in the surface zone of the ocean, while the deep and near-bottom zones play a major role in long-term carbon accumulation. The process is being intensively studied at the present time, but still not well understood.
The main features of the topography of the bottom of the oceans
The structure of the oceanic crust is different from the continental one: there is no granite layer inherent in the latter.
The thickness of the continental crust at sea level is about 30 km. The speed of seismic waves in its upper half corresponds to the velocities in granitic rocks, and in the lower half - to the velocities in basalts. In the oceans, under a five-kilometer layer of water, there is a layer of sedimentary rocks with an average thickness of 0.5 km, a layer of volcanic rocks - the "foundation" - with a thickness of 0.5 km, a crust with a thickness of 4 km, and at a depth of about 10 km the mantle begins.
There are four zones on the bottom of the World Ocean.
The first zone is the underwater margin of the continents. The underwater margin of the continents is the margin of the continents flooded by the waters of the ocean. It, in turn, consists of a shelf, a continental slope and a continental foot. Shelf - a coastal bottom plain with rather shallow depths, in essence, a continuation of the marginal plains of the land. Most of the shelf has a platform structure. On the shelf, there are often residual (relict) landforms of surface origin, as well as relict river and glacial deposits. This means that during the Quaternary retreat of the sea, vast expanses of the shelf turned into dry land.
Usually the shelf ends at depths of 100-200 m, and sometimes at greater depths, with a rather sharp bend, the so-called shelf crest. Below this edge towards the ocean, the continental slope extends - narrower than the shelf, the zone of the ocean or seabed with a surface slope of several degrees. Quite often the continental slope looks like a ledge or a series of ledges with a steepness from 10 to several tens of degrees.
The second - transitional - zone was formed at the junction of continental blocks and oceanic platforms. It consists of basins of the marginal seas, chains of predominantly volcanic islands in the form of arcs and narrow linear depressions - deep-sea trenches, with which deep faults coincide, going under the mainland.
On the outskirts of the Pacific Ocean, in the areas of the Mediterranean, Caribbean Seas, and the Scotia (Scotia) Sea, the underwater margins of the continents do not contact directly with the ocean floor, but with the bottom of the basins of the marginal or Mediterranean seas. In these basins, the crust is of the Suboceanic type. It is very thick mainly due to the sedimentary layer. From the outside, these basins are protected by huge underwater ridges. Sometimes their peaks rise above sea level, forming garlands of volcanic islands (Kuril, Mariana, Aleutian). These islands are called island arcs.
Deep-water trenches are located on the oceanic side of the island arcs - the grandiose continental crust is absent. Instead, a terrestrial, narrow, but very deep (6 - 11 km depth) depression is developed here. They stretch parallel to the island arcs and correspond to the outcrops of superdeep fault zones (the so-called Benioff-Zavaritsky zones) on the Earth's surface. Faults penetrate into the bowels of the Earth for many hundreds of kilometers. These zones are inclined towards the continents. The vast majority of earthquake sources are confined to them. Thus, the regions of deep-water trenches, island arcs, and deep-water marginal seas are distinguished by violent volcanism, sharp and extremely rapid movements of the earth's crust, and very high seismicity. These zones are called transition zones.
The third - the main - zone of the bottom of the World Ocean - the bed of the ocean, it is distinguished by the development of the earth's crust of an exclusively oceanic type. The ocean bed occupies more than half of its area at depths of up to 6 km. On the bed of the ocean there are ridges, plateaus, hills that divide it into basins. Bottom sediments are represented by various silts of organogenic origin and red deep-sea clay, which arose from fine insoluble mineral particles, cosmic dust and volcanic ash. At the bottom there are many ferromanganese nodules with impurities of other metals.
Ocean ridges are quite clearly divided into two types: arched blocky and blocky. Arch-block structures are basically arched, linearly elongated rises of the oceanic crust, usually broken into separate blocks by transverse faults (the Hawaiian Range, which forms the underwater base of the archipelago of the same name).
In addition to the ridges in the World Ocean, many elevations, or oceanic plateaus, are known. The largest of them in the Atlantic Ocean is the Bermuda Plateau. On its surface there are a number of seamounts of volcanic origin.
The most common type of relief of oceanic basins is the relief of abyssal hills. This is the name of countless hills from 50 to 500 m high, with a base diameter from several hundred meters to tens of kilometers, almost completely dotting the bottom of the basins. In addition, more than 10 thousand underwater mountain peaks are known at the bottom of the ocean. Some underwater years with flattened tops are called guyots. It is believed that once these peaks rose above the level of the ocean, until their tops were gradually cut off by the waves.
The other two types of landforms are undulating and flat abyssal plains. They arose after the partial or complete burial of the abyssal hills under a layer of sediments.
The fourth zone stands out in the central parts of the oceans. These are the largest landforms of the ocean floor - mid-ocean ridges - giant linearly oriented arched uplifts of the earth's crust. During the formation of the vault, the greatest stresses do not occur at its top, and here faults are formed, along which part of the vault is lowered, grabens, the so-called. rift valleys. Mantle material rushes upward along these weakened zones of the earth's crust.
Beginning in the Arctic Ocean with the small Gakkel Ridge, the system of these uplifts crosses the Norwegian-Greenland basin, includes Iceland, and passes into the grandiose North Atlantic and South Atlantic ridges. The latter passes into the West Indian Ridge already in the Indian Ocean. To the north of the parallel of Rodrigues Island, one branch - the Arabian-Indian ridge - goes north, continuing with a number of landforms of the bottom of the Gulf of Aden and the Red Sea, and the other branch follows the east and passes into the mid-ocean ridge of the Pacific Ocean - the South Pacific and East Pacific uplift. Mid-ocean ridges are probably young Cenozoic formations. Since the ridges are the result of crustal extension, are crossed by transverse faults, and often have central rift valleys, they provide an exceptional opportunity to study oceanic crustal rocks.
Sedimentation is one of the most important factors of relief formation in the ocean. It is known that more than 21 billion tons of solid sediments, up to 2 billion tons of volcanic products, and about 5 billion tons of calcareous and siliceous remains of organisms enter the World Ocean annually.
The structure of the World Ocean is its structure - vertical stratification of waters, horizontal (geographical) zonality, the nature of water masses and ocean 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 distinguished:
Upper sphere is formed by direct exchange of energy and matter with the troposphere in the form of microcirculation systems. It covers a layer of 200-300 m thick. This upper sphere is characterized by intense mixing, light penetration and significant temperature fluctuations.
Upper sphere breaks down into the following particular layers:
a) the uppermost layer is several tens of centimeters thick;
b) wind effect layer with a depth of 10-40 cm; he participates in excitement, reacts to the weather;
c) a layer of temperature jump, in which it drops sharply from the upper heated layer to the lower layer, not affected by waves and not heated;
d) penetration layer of seasonal circulation and temperature variability.
Ocean currents usually capture water masses only in the upper sphere.
Intermediate sphere extends to depths of 1500 - 2000 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 uniformity. Its thickness is about 2,000 m and it concentrates more than 50% of all the 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 expanses 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 sphere of the ocean. A water mass is a relatively large volume of water that forms in a certain area of the World Ocean and has almost constant physical (temperature, light), chemical (gases) and biological (plankton) properties for a long time. The water mass moves as a whole. One mass is separated from another by an ocean front.
The following types of water masses are distinguished:
1. Equatorial water masses limited by the equatorial and subequatorial fronts. They are characterized by the highest temperature in the open ocean, low salinity (up to 34-32 ‰), minimum density, high content of oxygen and phosphates.
2. Tropical and subtropical water masses are formed in areas of tropical atmospheric anticyclones and are limited from the side of 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, lack of nutrient salts and plankton. Ecologically, tropical water masses are oceanic deserts.
3. Moderate water masses are located in temperate latitudes and are limited from the side of the poles by the Arctic and Antarctic fronts. They are characterized 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 the Antarctic sink intensively into the near-bottom sphere and supply it with oxygen.
ocean currents. In accordance with the zonal distribution of solar energy over the surface of the planet, similar and genetically related circulation systems are created both in the ocean and in the atmosphere. The old assumption 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 zoning 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 (of air or water). Thus, an impulse of movement is born. The transfer of masses is their adaptation to the field of gravity, the desire for a uniform distribution.
Most macrocirculatory systems last all year. Only in the northern part of the Indian Ocean do the currents change following the monsoons.
In total, there are 10 major circulation systems on Earth:
1) North Atlantic (Azores) system;
2) North Pacific (Hawaiian) system;
3) South Atlantic system;
4) South Pacific system;
5) South 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 commonality is genetic in nature.
The surface current deviates from the direction of the wind at an angle of up to 45 0 to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Thus, the trade winds flow from east to west, while the 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 a certain depth, the current takes the opposite direction, which practically means its termination. Numerous measurements have shown that currents end at depths of no more than 300 m.
In the geographical shell as a system of a higher level 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.
Tropical anticyclonic systems of ocean currents are the largest. They extend from one coast of the ocean to another 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 40 ° latitude, for 4-5 thousand km. Steady and powerful currents, especially in the Northern Hemisphere, are mostly closed.
As in tropical atmospheric highs, the movement of water is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. From the eastern shores of the oceans (the western shores of the mainland), surface water belongs to the equator, rises from the depths (divergence) in its place, and cold comes in compensation from temperate latitudes. This is how cold currents are formed:
Canarian cold current;
California cold current;
Peruvian cold current;
Benguela cold current;
West Australian cold current, etc.
The speed of the currents is relatively small and is about 10 cm/sec.
Jets of compensatory currents flow into the Northern and Southern Equatorial (Equatorial) warm currents. The speed of these currents is quite high: 25-50 cm/sec on the tropical periphery and up to 150-200 cm/sec near the equator.
Approaching the shores of the continents, the trade winds naturally deviate. Large sewer currents 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 effect of the Earth's rotation, the center of the anticyclonic system of currents is shifted to the west relative to the center of the atmospheric anticyclone. Therefore, the transfer of water masses to temperate latitudes is concentrated in narrow bands near the western coasts of the oceans.
Guiana and Antilles currents wash the Antilles and most of the water enters the Gulf of Mexico. From it begins the flow of the Gulf Stream. 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 the middle latitudes, the water masses partially return to the same system near the western coasts of the continents, and are partially involved in the cyclonic systems of the temperate zone.
The equatorial system is represented by the Equatorial countercurrent. equatorial countercurrent formed as a compensation between the trade wind currents.
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- very extensive: from west to east they stretch for 5-6 thousand km and from north to south 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 proper as a drain continues no further than the New Foundland Bank. Starting from 40 0 N.S. water masses are involved in the circulation of temperate latitudes and, under the influence of western transport and the Coriolis force, are directed from the coasts of America 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 currents. Irminger, Norwegian, Svalbard, North Cape.
Gulf Stream in a narrow sense, it is called a runoff current from the Gulf of Mexico to 40 0 N, in a broad sense, a 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 northern part of the Pacific Ocean is similar to the North Atlantic, but differs from it in a smaller water exchange with the Arctic Ocean. Stock current Kuroshio goes into North Pacific heading towards Northwest America. Very often this system of currents is called 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 without connection with the Arctic.
Circumpolar Antarctic System of the Southern Ocean, respectively, the oceanicity of the Southern Hemisphere is represented by one current Western winds. This is the most powerful current in the oceans. It covers the Earth in a continuous ring in the belt from 35-40 to 50-60 0 S.L. Its width is about 2,000 km, its thickness is 185–215 km3/s, and its speed is 25–30 cm/s. To a large extent, this current determines the independence of the Southern Ocean.
The circumpolar course of the Western winds is not closed: branches depart from it, flowing into Peruvian, Benguela, Western Australian currents, and from the south, from Antarctica, 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 throughout the Arctic Ocean to the Nansen Strait (between Svalbard and Greenland). Then it continues East Greenland and Labrador. In the east, in the Chukchi Sea, it separates from the Western Arctic Current polar current, going through 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 currents has not yet received a proper scientific explanation. The reason for this probably lies in the fact that north of the equator the meridional transport dominates, while in the Southern Hemisphere it is zonal. This is also explained by the position and shape of the continents.
In inland seas, water circulation is always individual.
54. Land waters. Types of land waters
Atmospheric precipitation, after falling on the surface of continents and islands, is divided into four unequal and variable parts: one evaporates and is transported further inland by atmospheric runoff; the second seeps into the soil and into the soil and is retained for some time in the form of soil and underground water, flowing into rivers and seas in the form of groundwater runoff; the third in streams and rivers flows into the seas and oceans, forming surface runoff; the fourth turns into mountain or continental glaciers, which melt and flow into the ocean. Accordingly, four types of water accumulation are distinguished on land: groundwater, rivers, lakes and glaciers.
55. Land runoff. Values characterizing the runoff. Runoff factors
The flow of rain and melt water in small streams down the slopes is called planar or slope drain. Slope runoff jets collect in streams and rivers, forming run-of-river, or linear, called river , stock . Groundwater flows into rivers as ground or underground runoff.
Full river flow R formed from the surface S and underground U:R=S+U . (see Table 1). Total river runoff is 38800 km3, surface runoff is 26900 km3, groundwater runoff is 11900 km3, glacial runoff (2500-3000 km3) and groundwater runoff directly into the seas along the coastline is 2000-4000 km3.
Table 1 - Land water balance without polar glaciers
Surface runoff depends on the weather. It is unstable, temporary, feeds the soil poorly, often needs regulation (ponds, reservoirs).
ground runoff occurs in the soil. During the wet season, the ground receives excess water from the surface and in the rivers, and during the dry months, groundwater feeds the rivers. They ensure the constancy of the flow of water in the rivers and the normal water regime of the soil.
The total volume and ratio of surface and underground runoff varies 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 rare, the rivers are shallow or dry up altogether.
The density of the river network and the high water content of rivers are a function of the runoff or water balance of the territory. The flow as a whole is determined by the physical and geographical conditions of the area, on which the hydrological and geographical method of studying land waters is based.
Values characterizing the runoff. Land runoff 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 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 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 amount of precipitation 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.
The runoff depends on the climate, the nature of the soil cover, topography, vegetation, weathering, the presence of lakes and other factors.
Dependence of runoff on climate. The role of climate in the hydrological regime of the land is enormous: the more precipitation and less evaporation, the greater the runoff, and vice versa. Above 100% humidity, runoff follows rainfall regardless of the amount of evaporation. At less than 100% humidity, runoff decreases following evaporation.
However, the role of climate should not be overestimated to the detriment of other factors. If we recognize climatic factors as decisive, and the rest as insignificant, then we will lose the ability to regulate the flow.
Dependence of runoff on soil cover. Soil and soils absorb and accumulate (accumulate) moisture. The soil cover converts atmospheric precipitation into an element water regime and serves as a medium in which 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.
Dependence of runoff on relief. It is necessary to distinguish between the value for the runoff of macro-, meso- and microrelief.
Already from insignificant heights, the runoff is greater than from the plains adjacent to them. So, on the Valdai Hills, 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 Transcaucasus, 75 l/km2/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 of the meso- and microrelief on the runoff is manifested. They redistribute the runoff and influence its rate. On flat areas of the plains, the runoff is slow, the soils are saturated with moisture, waterlogging is possible. On the slopes, flat runoff turns into a linear one. There are ravines and river valleys. They, in turn, accelerate the flow and drain the area.
Valleys and other depressions in the relief, in which water accumulates, supply the soil with water. This is especially significant in zones of insufficient moisture, where soils 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 thereby 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 runoff. Vegetation contributes to the accumulation of snow and slows 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 evaporates before reaching the soil. Vegetation counteracts erosion, slows down runoff and transfers it from surface to underground. Vegetation maintains the humidity of the air and thereby enhances intracontinental moisture cycles and increases the amount of precipitation. It affects the moisture cycle by changing the soil and its water intake properties.
The influence of vegetation is different in different zones. VV Dokuchaev (1892) believed that the steppe forests are reliable and faithful regulators of the water regime of the steppe zone. In the taiga zone, the forests dry up the area through greater evaporation than in the fields. In the steppes, forest belts contribute to the accumulation of moisture by retaining snow and reducing runoff and evaporation from the soil.
The impact on swamp runoff is different in zones of excessive and insufficient moisture. In the forest zone, they are runoff regulators. In the forest-steppe and steppes, their influence is negative, they suck in surface and ground water and evaporate it into the atmosphere.
Weathering crust and runoff. Sand and pebble deposits accumulate water. Often, streams from distant places are filtered through them, for example, in deserts from mountains. On massively crystalline rocks, all surface water drains; on shields, groundwater circulates only in cracks.
Importance of lakes for flow regulation. One of the most powerful flow regulators are large flowing lakes. Large lake-river systems, like the Neva or St. Lawrence, have a very regulated flow and this differs significantly from all other river systems.
Complex of physiographic factors of runoff. All of the above factors act together, influencing one another in an integral system of the geographic envelope, determine gross moistening of the territory . This is the name of that part of atmospheric precipitation, which, with the deduction of 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.
Water is the simplest chemical compound of hydrogen and oxygen, but ocean water is a universal homogeneous ionized solution, which includes 75 chemical elements. These are solid mineral substances (salts), gases, as well as suspensions of organic and inorganic origin.
Vola has many different physical and chemical properties. First of all, they depend on the table of contents and temperature environment. Let's briefly describe some of them.
Water is a solvent. Since water is a solvent, it can be judged that all waters are gas-salt solutions of various chemical composition and various concentrations.
Salinity of ocean, sea and river water
Salinity sea water (Table 1). The concentration of substances dissolved in water is characterized by salinity which is measured in ppm (% o), i.e., in grams of a substance per 1 kg of water.
Table 1. Salt content in sea and river water (in % of the total mass of salts)
|
Basic connections |
Sea water |
river water |
|
Chlorides (NaCI, MgCb) |
||
|
Sulphates (MgS0 4, CaS0 4, K 2 S0 4) |
||
|
Carbonates (CaCOd) |
||
|
Compounds of nitrogen, phosphorus, silicon, organic and other substances |
||
Lines on a map connecting points of equal salinity are called isohalines.
Salinity of fresh water(see Table 1) is on average 0.146% o, and marine - on average 35 %O. Salts dissolved in water give it a bitter-salty taste.
About 27 out of 35 grams is sodium chloride (table salt), so the water is salty. Magnesium salts give it a bitter taste.
Since the water in the oceans was formed from hot saline solutions of the earth's interior and gases, its salinity was primordial. There is reason to believe that at the first stages of the formation of the ocean, its waters did not differ much from river waters in terms of salt composition. Differences were outlined and began to intensify after the transformation of rocks as a result of their weathering, as well as the development of the biosphere. The modern salt composition of the ocean, as fossil remains show, was formed no later than the Proterozoic.
In addition to chlorides, sulfites and carbonates, almost all chemical elements known on Earth, including noble metals, have been found in sea water. However, the content of most elements in seawater is negligible, for example, only 0.008 mg of gold in a cubic meter of water was detected, and the presence of tin and cobalt is indicated by their presence in the blood of marine animals and in bottom sediments.
Salinity of ocean waters- the value is not constant (Fig. 1). It depends on the climate (the ratio of precipitation and evaporation from the surface of the ocean), the formation or melting of ice, sea currents, near the continents - on the influx of fresh river water.
Rice. 1. Dependence of water salinity on latitude
In the open ocean, salinity ranges from 32-38%; in the marginal and Mediterranean seas, its fluctuations are much greater.
The salinity of waters down to a depth of 200 m is especially strongly affected by the amount of precipitation and evaporation. Based on this, we can say that the salinity of sea water is subject to the law of zoning.
In the equatorial and subequatorial regions, salinity is 34% c, because the amount of precipitation is greater than the water spent on evaporation. In tropical and subtropical latitudes - 37, since there is little precipitation, and evaporation is high. In temperate latitudes - 35% o. The lowest salinity of sea water is observed in the subpolar and polar regions - only 32, since the amount of precipitation exceeds evaporation.
Sea currents, river runoff, and icebergs disrupt the zonal pattern of salinity. For example, in the temperate latitudes of the Northern Hemisphere, the salinity of water is greater near the western coasts of the continents, where more saline subtropical waters are brought with the help of currents, and the salinity of water is lower near the eastern coasts, where cold currents bring less saline water.
Seasonal changes in water salinity occur in subpolar latitudes: in autumn, due to the formation of ice and a decrease in the strength of river runoff, salinity increases, and in spring and summer, due to ice melting and increased river runoff, salinity decreases. Around Greenland and Antarctica, salinity decreases during the summer as a result of the melting of nearby icebergs and glaciers.
The most saline of all oceans is the Atlantic Ocean, the waters of the Arctic Ocean have the lowest salinity (especially off the Asian coast, near the mouths of Siberian rivers - less than 10% o).
Among the parts of the ocean - seas and bays - the maximum salinity is observed in areas bounded by deserts, for example, in the Red Sea - 42% c, in the Persian Gulf - 39% c.
Its density, electrical conductivity, ice formation and many other properties depend on the salinity of water.
The gas composition of ocean water
In addition to various salts, different gases are dissolved in the waters of the World Ocean: nitrogen, oxygen, carbon dioxide, hydrogen sulfide, etc. As in the atmosphere, oxygen and nitrogen predominate in ocean waters, but in slightly different proportions (for example, the total amount of free oxygen in the ocean 7480 billion tons, which is 158 times less than in the atmosphere). Despite the fact that gases occupy a relatively small place in water, this is enough to influence organic life and various biological processes.
The amount of gases is determined by the temperature and salinity of water: the higher the temperature and salinity, the lower the solubility of gases and the lower their content in water.
So, for example, at 25 ° C, up to 4.9 cm / l of oxygen and 9.1 cm 3 / l of nitrogen can dissolve in water, at 5 ° C - 7.1 and 12.7 cm 3 / l, respectively. Two important consequences follow from this: 1) the oxygen content in the surface waters of the ocean is much higher in temperate and especially polar latitudes than in low latitudes (subtropical and tropical), which affects the development of organic life - the richness of the first and the relative poverty of the second waters; 2) in the same latitudes, the oxygen content in ocean waters is higher in winter than in summer.
Daily changes in the gas composition of water associated with temperature fluctuations are small.
The presence of oxygen in ocean water contributes to the development of organic life in it and the oxidation of organic and mineral products. The main source of oxygen in ocean water is phytoplankton, called the "lungs of the planet." Oxygen is mainly consumed for the respiration of plants and animals in the upper layers of sea waters and for the oxidation of various substances. In the depth interval of 600-2000 m, there is a layer oxygen minimum. A small amount of oxygen is combined with a high content of carbon dioxide. The reason is the decomposition in this water layer of the bulk of the organic matter coming from above and the intensive dissolution of biogenic carbonate. Both processes require free oxygen.
The amount of nitrogen in sea water is much less than in the atmosphere. This gas mainly enters the water from the air during the breakdown of organic matter, but is also produced during the respiration of marine organisms and their decomposition.
In the water column, in deep stagnant basins, as a result of the vital activity of organisms, hydrogen sulfide is formed, which is toxic and inhibits the biological productivity of water.
Heat capacity of ocean waters
Water is one of the most heat-intensive bodies in nature. The heat capacity of only a ten meter layer of the ocean is four times greater than the heat capacity of the entire atmosphere, and a 1 cm layer of water absorbs 94% of the solar heat entering its surface (Fig. 2). Due to this circumstance, the ocean slowly heats up and slowly releases heat. Due to the high heat capacity, all water bodies are powerful heat accumulators. Cooling, the water gradually releases its heat into the atmosphere. Therefore, the World Ocean performs the function thermostat our planet.
Rice. 2. Dependence of heat capacity of water on temperature
Ice and especially snow have the lowest thermal conductivity. As a result, ice protects the water on the surface of the reservoir from hypothermia, and snow protects the soil and winter crops from freezing.
Heat of evaporation water - 597 cal / g, and melting heat - 79.4 cal / g - these properties are very important for living organisms.
Ocean water temperature
Index thermal state ocean temperature.
Average temperature of ocean waters- 4 °C.
Despite the fact that the surface layer of the ocean performs the functions of the Earth's temperature regulator, in turn, the temperature of sea waters depends on the heat balance (inflow and outflow of heat). The heat input is made up of , and the flow rate is made up of the costs of water evaporation and turbulent heat exchange with the atmosphere. Despite the fact that the proportion of heat spent on turbulent heat transfer is not large, its significance is enormous. It is with its help that the planetary redistribution of heat occurs through the atmosphere.
On the surface, the temperature of ocean waters ranges from -2 ° C (freezing temperature) to 29 ° C in the open ocean (35.6 ° C in the Persian Gulf). The average annual temperature of the surface waters of the World Ocean is 17.4°C, and in the Northern Hemisphere it is about 3°C higher than in the Southern Hemisphere. The highest temperature of surface ocean waters in the Northern Hemisphere is in August, and the lowest is in February. In the Southern Hemisphere, the opposite is true.
Since it has thermal relationships with the atmosphere, the temperature of surface waters, like air temperature, depends on the latitude of the area, i.e., it is subject to the zonality law (Table 2). Zoning is expressed in a gradual decrease in water temperature from the equator to the poles.
In tropical and temperate latitudes, water temperature mainly depends on sea currents. So, due to warm currents in tropical latitudes in the west of the oceans, temperatures are 5-7 ° C higher than in the east. However, in the Northern Hemisphere, due to warm currents in the east of the oceans, temperatures are positive all year round, and in the west, due to cold currents, the water freezes in winter. In high latitudes, the temperature during the polar day is about 0 °C, and during the polar night under the ice it is about -1.5 (-1.7) °C. Here, the water temperature is mainly affected by ice phenomena. In autumn, heat is released, softening the temperature of air and water, and in spring, heat is spent on melting.
Table 2. Average annual temperatures of the surface waters of the oceans
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Average annual temperature, "C |
Average annual temperature, °С |
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North hemisphere |
Southern Hemisphere |
North hemisphere |
Southern Hemisphere |
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The coldest of all oceans- Arctic, and the warmest- The Pacific Ocean, since its main area is located in the equatorial-tropical latitudes (the average annual temperature of the water surface is -19.1 ° C).
An important influence on the temperature of ocean water is exerted by the climate of the surrounding territories, as well as the time of year, since the sun's heat, which heats the upper layer of the World Ocean, depends on it. The highest water temperature in the Northern Hemisphere is observed in August, the lowest - in February, and in the Southern - vice versa. Daily fluctuations in sea water temperature at all latitudes are about 1 °C, the largest values of annual temperature fluctuations are observed in subtropical latitudes - 8-10 °C.
The temperature of ocean water also changes with depth. It decreases and already at a depth of 1000 m almost everywhere (on average) below 5.0 °C. At a depth of 2000 m, the water temperature levels off, dropping to 2.0-3.0 ° C, and in polar latitudes - up to tenths of a degree above zero, after which it either drops very slowly or even rises slightly. For example, in the rift zones of the ocean, where at great depths there are powerful outlets of underground hot water under high pressure, with temperatures up to 250-300 °C. In general, two main layers of water are distinguished vertically in the World Ocean: warm superficial And powerful cold extending to the bottom. Between them is a transitional temperature jump layer, or main thermal clip, a sharp decrease in temperature occurs within it.
This picture of the vertical distribution of water temperature in the ocean is disturbed at high latitudes, where at a depth of 300–800 m there is a layer of warmer and saltier water that came from temperate latitudes (Table 3).
Table 3. Average values of ocean water temperature, °С
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Depth, m |
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equatorial |
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tropical |
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Polar |
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Change in the volume of water with a change in temperature
A sudden increase in the volume of water when freezing is a peculiar property of water. With a sharp decrease in temperature and its transition through the zero mark, a sharp increase in the volume of ice occurs. As the volume increases, the ice becomes lighter and floats to the surface, becoming less dense. Ice protects the deep layers of water from freezing, as it is a poor conductor of heat. The volume of ice increases by more than 10% compared to the initial volume of water. When heated, a process occurs that is the opposite of expansion - compression.
Density of water
Temperature and salinity are the main factors that determine the density of water.
For sea water, the lower the temperature and the higher the salinity, the greater the density of the water (Fig. 3). So, at a salinity of 35% o and a temperature of 0 ° C, the density of sea water is 1.02813 g / cm 3 (the mass of each cubic meter of such sea water is 28.13 kg more than the corresponding volume of distilled water). The temperature of sea water of the highest density is not +4 °C, as in fresh water, but negative (-2.47 °C at a salinity of 30% c and -3.52 °C at a salinity of 35%o
Rice. 3. Relationship between the density of sea water and its salinity and temperature
Due to the increase in salinity, the density of water increases from the equator to the tropics, and as a result of a decrease in temperature, from temperate latitudes to the Arctic Circles. In winter, the polar waters sink and move in the bottom layers towards the equator, so the deep waters of the World Ocean are generally cold, but enriched with oxygen.
The dependence of water density on pressure was also revealed (Fig. 4).
Rice. 4. Dependence of the density of the sea water (A "= 35% o) on pressure at various temperatures
The ability of water to self-purify
This is an important property of water. In the process of evaporation, water passes through the soil, which, in turn, is a natural filter. However, if the pollution limit is violated, the self-cleaning process is violated.
Color and transparency depend on the reflection, absorption and scattering of sunlight, as well as on the presence of suspended particles of organic and mineral origin. In the open part, the color of the ocean is blue, near the coast, where there are a lot of suspensions, it is greenish, yellow, brown.
In the open part of the ocean, water transparency is higher than near the coast. In the Sargasso Sea, the water transparency is up to 67 m. During the development of plankton, the transparency decreases.
In the seas, such a phenomenon as glow of the sea (bioluminescence). Glow in sea water living organisms containing phosphorus, primarily such as protozoa (night light, etc.), bacteria, jellyfish, worms, fish. Presumably, the glow serves to scare away predators, to search for food, or to attract individuals of the opposite sex in the dark. The glow helps fishing boats find schools of fish in sea water.
Sound conductivity - acoustic property of water. Found in the oceans sound-diffusing mine And underwater "sound channel", possessing sonic superconductivity. The sound-diffusing layer rises at night and falls during the day. It is used by submariners to dampen submarine engine noise, and by fishing boats to detect schools of fish. "Sound
signal" is used for short-term forecasting of tsunami waves, in underwater navigation for ultra-long-range transmission of acoustic signals.
Electrical conductivity sea water is high, it is directly proportional to salinity and temperature.
natural radioactivity sea water is small. But many animals and plants have the ability to concentrate radioactive isotopes, so the seafood catch is tested for radioactivity.
Mobility is a characteristic property of liquid water. Under the influence of gravity, under the influence of wind, attraction by the Moon and the Sun and other factors, water moves. When moving, the water is mixed, which allows even distribution of waters of different salinity, chemical composition and temperature.
The hydrosphere is the shell of the Earth, which is formed by oceans, seas, surface water bodies, snow, ice, rivers, temporary water flows, water vapor, clouds. The shell, composed of reservoirs and rivers, oceans has a discontinuous character. The underground hydrosphere is formed by underground currents, groundwater, artesian basins.
The hydrosphere has a volume equal to 1,533,000,000 cubic kilometers. Water covers three fourths of the Earth's surface. Seventy-one percent of the Earth's surface is covered by seas and oceans.
The huge water area largely determines the water and thermal regimes on the planet, since water has a high heat capacity, it has a large energy potential. Water plays an important role in the formation of the soil, the appearance of the landscape. The waters of the oceans are different chemical composition water is almost never found in distilled form.
Oceans and seas
The world ocean is a body of water that washes the continents, it makes up more than 96 percent of the total volume of the earth's hydrosphere. Two layers of the water mass of the world's oceans have different temperatures, which ultimately determines the temperature regime of the Earth. The world's oceans accumulate the energy of the sun, and when cooled, part of the heat is transferred to the atmosphere. That is, the thermoregulation of the Earth is largely due to the nature of the hydrosphere. The world ocean includes four oceans: Indian, Pacific, Arctic, Atlantic. Some scientists single out the Southern Ocean, which surrounds Antarctica.
The world ocean is distinguished by the heterogeneity of water masses, which, located in a certain place, acquire distinctive characteristics. The bottom, intermediate, surface and subsurface layers are distinguished vertically in the ocean. The bottom mass has the largest volume, it is also the coldest.
Sea - part of the ocean that extends into the mainland or adjacent to it. The sea differs in its features from the rest of the ocean. The basins of the seas develop their own hydrological regime.
The seas are divided into internal (for example, the Black, Baltic), inter-island (in the Indo-Malay archipelago) and marginal (seas of the Arctic). Among the seas, inland (White Sea), intercontinental (Mediterranean) are distinguished.
Rivers, lakes and swamps
An important component of the Earth's hydrosphere is rivers, they contain 0.0002 percent of all water reserves, 0.005 percent fresh water. Rivers are an important natural reservoir of water, which is used for drinking, industry, and agriculture. Rivers are a source of irrigation, water supply, watering. Rivers are fed by snow cover, groundwater and rainwater.
Lakes occur when there is excess moisture and in the presence of basins. Basins can be of tectonic, glacial-tectonic, volcanic, cirque origin. Thermokarst lakes are common in permafrost regions, floodplain lakes are often found in river floodplains. The regime of lakes is determined by whether the river carries water out of the lake or not. Lakes can be endorheic, flowing, represent a common lake-river system with a river.
Swamps are common on the plains in conditions of waterlogging. The lowlands are fed by soils, the upland ones are fed by precipitation, the transitional ones are fed by soils and precipitation.
The groundwater
Groundwater is located at different depths in the form of aquifers in the rocks of the earth's crust. Groundwater lies closer to the surface of the earth, groundwater is located in deeper layers. Of greatest interest are mineral and thermal waters.
Clouds and water vapor
Water vapor condensate forms clouds. If the cloud has a mixed composition, that is, it includes ice and water crystals, then they become a source of precipitation.
Glaciers
All components of the hydrosphere have their own special role in the global processes of energy exchange, global moisture circulation, and affect many life-forming processes on Earth.
The body of water outside the land is called oceans. The waters of the World Ocean occupy about 70.8% of the surface area of our planet (361 million km 2) and play an extremely important role in the development of the geographical envelope.
The world ocean contains 96.5% of the waters of the hydrosphere. The volume of its waters is 1,336 million km 3. The average depth is 3711 m, the maximum is 11022 m. The prevailing depths are from 3000 to 6000 m. They account for 78.9% of the area.
The temperature of the water surface is from 0°C and below in the polar latitudes to +32°C in the tropics (Red Sea). To the bottom layers, it decreases to +1°C and below. The average salinity is about 35 ‰, the maximum is 42 ‰ (Red Sea).
The oceans are divided into oceans, seas, bays, straits.
Borders oceans not always and not everywhere they pass along the coasts of the continents, they are often carried out very conditionally. Each ocean has a complex of inherent qualities only to it. Each of them is characterized by its own system of currents, a system of tides, a specific distribution of salinity, its own temperature and ice regime, its own circulation with air currents, its own character of depths and dominant bottom sediments. Allocate Pacific (Great), Atlantic, Indian and Arctic oceans. Sometimes the Southern Ocean is also distinguished.
Sea - a significant area of the ocean, more or less isolated from it by land or underwater uplifts and distinguished by its natural conditions(depth, bottom relief, temperature, salinity, waves, currents, tides, organic life).
Depending on the nature of the contact between continents and oceans Seas are divided into the following three types:
1.Mediterranean seas: are located between two continents or are located in the fault belts of the earth's crust; they are characterized by a strong indentation of the coastline, a sharp drop in depths, seismicity and volcanism (Sargasso Sea, Red Sea, Mediterranean Sea, Sea of Marmara, etc.).
2. Inland seas: deeply protrude into land, located inside the continents, between islands or continents or within the archipelago, significantly separated from the ocean, characterized by shallow depths (White Sea, Baltic Sea, Hudson Sea, etc.).
3. Marginal seas: located on the outskirts of the continents and large islands, on continental shallows and slopes. They are wide open towards the ocean (the Norwegian Sea, the Kara Sea, the Sea of Okhotsk, the Sea of Japan, the Yellow Sea, etc.).
Geographical position sea largely determines its hydrological regime. Inland seas are weakly connected to the ocean, so the salinity of their water, currents and tides differ markedly from those of the ocean. The regime of the marginal seas is essentially oceanic. Most of the seas are located off the northern continents, especially off the coast of Eurasia.
gulf - a part of the ocean or sea that protrudes into the land, but has free water exchange with the rest of the water area, differs slightly from it in terms of natural features and regime. The difference between the sea and the bay is not always perceptible. In principle, the bay is smaller than the sea; every sea forms bays, but the opposite does not happen. Historically, in the Old World, even small water areas, such as Azov and Marmara, are called seas, and in America and Australia, where names were given by European discoverers, even large seas are called bays - Hudson, Mexican. Sometimes the same water areas are called one sea, the other - a bay (Arabian Sea, Bay of Bengal).
Depending on the origin, coast structure, shape and size, bays are called bays, fjords, estuaries, lagoons:
Bays (harbours)- bays of small size, protected from waves and winds by capes protruding into the sea. They are convenient for mooring ships (Novorossiysk, Sevastopol - the Black Sea, the Golden Horn - the Sea of Japan, etc.).
fjords- narrow, deep, long bays with protruding, steep, rocky shores and a trough-shaped profile, often separated from the sea by underwater rapids. The length of some can reach more than 200 km, the depth - more than 1000 m. Their origin is associated with faults and erosional activity of Quaternary glaciers (the coast of Norway, Greenland, Chile).
Estuaries- shallow, deeply protruding bays with spits and embankments. They are formed in the widened mouths of rivers when the coastal land sinks (the Dnieper and Dniester estuaries in the Black Sea).
lagoons- Shallow bays with salty or brackish water stretched along the coast, separated from the sea by spits, or connected to the sea by a narrow strait (well developed on the coast of the Gulf of Mexico).
Lips- shallow bays into which large rivers usually flow. Here, the water is highly desalinated, differs sharply in color from the water of the adjacent sea area and has yellowish and brownish hues (Penzhina Bay).
Straits - relatively narrow water spaces connecting separate parts of the World Ocean and separating land areas. According to the nature of water exchange, they are divided into: flowing– currents are directed along the entire cross section in one direction; exchange The waters move in opposite directions. In them, water exchange can occur vertically (Bosphorus) or horizontally (Laperouse, Devisov).
structure The world ocean is called its structure - vertical stratification of waters, horizontal (geographical) zonality, the nature of water masses and ocean fronts.
In a vertical section, the water column breaks up into large layers, similar to the layers of the atmosphere. The following four spheres (layers) are distinguished:
Upper sphere formed by direct exchange of energy and matter with the troposphere. It covers a layer of 200–300 m thick. This upper sphere is characterized by intense mixing, light penetration and significant temperature fluctuations.
Intermediate sphere extends to depths of 1500–2000 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. They stand out in the polar regions with elevated temperatures, in temperate latitudes and tropical regions with low or high salinity. Horizontal transfers of water masses predominate.
Deep Sphere does not reach the bottom by about 1000 m. This sphere is characterized by a certain uniformity. Its thickness is about 2000 m and it concentrates more than 50% of all the water of the World Ocean.
bottom sphere occupies the lowest layer of the ocean and extends to a distance of about 1000 m from the bottom. The waters of this sphere are formed in cold zones, in the Arctic and Antarctic and move over vast expanses along deep basins and trenches, they are distinguished by the lowest temperatures and the highest density. They perceive heat from the bowels of the Earth and interact with the ocean floor. Therefore, during their movement, they are significantly transformed.
A water mass is a relatively large volume of water that forms in a certain area of the World Ocean and has almost constant physical (temperature, light), chemical (gases) and biological (plankton) properties for a long time. One mass is separated from another by an ocean front.
The following types of water masses are distinguished:
1. Equatorial water masses are characterized by the highest temperature in the open ocean, low salinity (up to 34–32 ‰), minimum density, high content of oxygen and phosphates.
2. Tropical and subtropical water masses are created in the areas of tropical atmospheric anticyclones and are characterized by high salinity (up to 37 ‰ and more) and high transparency, poverty of nutrient salts and plankton. Ecologically, they are oceanic deserts.
3. Moderate water masses are located in temperate latitudes and are characterized 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. The polar water masses of the Arctic and Antarctic are characterized by the lowest temperature, highest density, and high oxygen content. The waters of the Antarctic sink intensively into the near-bottom sphere and supply it with oxygen.
The waters of the World Ocean are in continuous movement and mixing. Unrest- oscillatory movements of water, currents- progressive. The main cause of unrest (waves) on the surface is wind at a speed of more than 1 m/s. The excitement caused by the wind fades with depth. Deeper than 200 m, even strong waves are already imperceptible. At a wind speed of approximately 0.25 m / s, ripples. When the wind increases, the water experiences not only friction, but also air blows. Waves grow in height and length, increasing the period of oscillation and speed. The ripples turn into gravitational waves. The magnitude of the waves depends on the wind speed and acceleration. The maximum height in temperate latitudes (up to 20 - 30 meters). The least excitement is in the equatorial zone, the frequency of calm is 20 - 33%.
Seismic waves are generated by underwater earthquakes and volcanic eruptions. tsunami. The length of these waves is 200 - 300 meters, the speed is 700 - 800 km / h. seiches(standing waves) occur as a result of sudden changes in pressure over the water surface. Amplitude 1 - 1.5 meters. Characteristic of closed seas and bays.
sea currents- these are horizontal movements of water in the form of wide streams. Surface currents are caused by wind, while deep currents are caused by different water densities. Warm currents (Gulf Stream, North Atlantic) are directed from lower latitudes towards wider ones, cold ones (Labrodor, Peruvian) - vice versa. In tropical latitudes near the western coasts of the continents, the trade winds drive warm water and carry it westward. In her place rises from the deep cold water. 5 cold currents are formed: Canary, California, Peruvian, West Australian and Benguela. In the southern hemisphere, the cold streams of the current of the West Winds pour into them. Warm waters are formed by moving parallel trade wind currents: North and South. In the Indian Ocean in the northern hemisphere - monsoon. At the eastern coasts of the continents, they are divided into parts, deviate to the north and south and go along the continents: at 40 - 50º N.S. under the influence of westerly winds, the currents deviate to the east and form warm currents.
Tidal movements ocean waters arise under the influence of the forces of attraction of the moon and the sun. The highest tides are observed in the Bay of Fundy (18 m). There are semi-diurnal, diurnal and mixed tides.
Also, the water dynamics is characterized by vertical mixing: in convergence zones - water subsidence, in divergence zones - upwelling.
The bottom of the oceans and seas is covered with sedimentary deposits called marine sediments , soils and silts. According to the mechanical composition, udon deposits are classified into: coarse-grained sedimentary rocks or psephites(blocks, boulders, pebbles, gravel), sandy rocks or psummits(sands coarse, medium, fine), silty rocks or silts(0.1 - 0.01 mm) and clayey rocks or pellets.
According to the material composition, bottom sediments are divided into weakly calcareous (lime content 10–30%), calcareous (30–50%), highly calcareous (more than 50%), weakly siliceous (silicon content 10–30%), siliceous (30–50%) and strongly siliceous (more than 50%) deposits. According to the genesis, terrigenous, biogenic, volcanogenic, polygenic and authigenic deposits are distinguished.
Terrigenous precipitation is brought from land by rivers, wind, glaciers, surf, tides and tides in the form of rock destruction products. Near the coast, they are represented by boulders, further by pebbles, sands, and finally, silts and clays. They cover approximately 25% of the ocean floor, occur mainly on the shelf and continental slope. A special variety of terrigenous deposits are iceberg deposits, which are characterized by a low content of lime, organic carbon, poor sorting, and a diverse granulometric composition. They are formed from sedimentary material that falls to the ocean floor when icebergs melt. They are most characteristic of the Antarctic waters of the World Ocean. There are also terrigenous deposits of the Arctic Ocean, formed from sedimentary material brought by rivers, icebergs, river ice. Turbidites, sediments of turbidity flows, also have a mostly terrigenous composition. They are typical of the continental slope and continental foot.
Biogenic precipitation are formed directly in the oceans and seas as a result of the death of various marine organisms, mainly planktonic, and the precipitation of their insoluble residues. According to their material composition, biogenic deposits are divided into siliceous and calcareous.
Siliceous sediments consist of the remains of diatoms, radiolarians and flint sponges. Diatom sediments are widespread in the southern parts of the Pacific, Indian and Atlantic oceans in the form of a continuous belt around Antarctica; in the northern part of the Pacific Ocean, in the Bering and Okhotsk seas, but here they contain a high admixture of terrigenous material. Separate patches of diatom oozes have been found at great depths (more than 5000 m) in the tropical zones of the Pacific Ocean. Diatom-radiolarian deposits are most common in the tropical latitudes of the Pacific and Indian oceans, flint-sponge deposits are found on the shelf of Antarctica, the Sea of Okhotsk.
lime deposits, like siliceous, are divided into a number of types. The most widely developed are foraminiferal-coccolithic and foraminiferal oozes, which are distributed mainly in the tropical and subtropical parts of the oceans, especially in the Atlantic. A typical foraminiferal silt contains up to 99% lime. The shells of planktonic foraminifers, as well as coccolithophorids, shells of planktonic calcareous algae, constitute a significant part of such oozes. With a significant admixture in the bottom sediments of shells of planktonic pteropod mollusks, pteropod-foraminiferal deposits are formed. Large areas of them are found in the equatorial Atlantic, as well as in the Mediterranean, Caribbean Seas, in the Bahamas, in the Western Pacific Ocean and other areas of the World Ocean.
Coral-algae deposits occupy the equatorial and tropical shallow waters of the western part of the Pacific Ocean, cover the bottom in the north of the Indian Ocean, in the Red and Caribbean Seas, shelly carbonate deposits - coastal zones of the seas of temperate and subtropical zones.
Pyroclastic or volcanogenic sediments are formed as a result of the products of volcanic eruptions entering the World Ocean. Usually these are tuffs or tuff breccias, less often - unconsolidated sands, silts, less often sediments of deep, highly saline and high-temperature underwater sources. So, at their outlets in the Red Sea, highly ferruginous sediments with a high content of lead and other non-ferrous metals are formed.
TO polygenic sediments one type of bottom sediments is referred to as deep-water red clay, a sediment of pelitic composition of brown or brown-red color. This color is due to the high content of iron and manganese oxides. Deep-water red clays are common in the abyssal basins of the oceans at depths of more than 4500 m. They occupy the most significant areas in the Pacific Ocean.
authigenic or chemogenic sediments are formed as a result of chemical or biochemical precipitation of certain salts from sea water. These include oolitic deposits, glauconite sands and silts, and ferromanganese nodules.
Oolites- the smallest balls of lime, found in the warm waters of the Caspian and Aral Seas, the Persian Gulf, in the Bahamas.
Glauconite sands and silts– sediments of various compositions with a noticeable admixture of glauconite. They are most widespread on the shelf and continental slope off the Atlantic coast of the USA, Portugal, Argentina, on the underwater margin of Africa, off the southern coast of Australia and in some other areas.
ferromanganese nodules- concretions of iron and manganese hydroxides with an admixture of other compounds, primarily cobalt, copper, nickel. They occur as inclusions in deep-water red clays and in places, especially in the Pacific Ocean, form large accumulations.
More than a third of the entire area of the ocean floor is occupied by deep-water red clay, and approximately the same distribution area is covered by foraminiferal sediments. The rate of accumulation of sediments is determined by the thickness of the layer of sediments deposited on the bottom over 1000 years (in some areas 0.1–0.3 mm per thousand years, in estuaries, transition zones and gutters - hundreds of millimeters per thousand years).
In the distribution of bottom sediments in the World Ocean, the law of latitudinal geographical zonality is clearly manifested. So, in the tropical and temperate zones, the ocean floor to a depth of 4500–5000 m is covered with biogenic calcareous deposits, deeper - with red clays. The subpolar belts are occupied by siliceous biogenic material, while the polar belts are occupied by iceberg deposits. Vertical zoning finds expression in the replacement of carbonate sediments at great depths by red clays.
