Natural complexes of the world ocean. The world's oceans and its parts

Water is the simplest chemical compound of hydrogen and oxygen, but ocean water is a universal, homogeneous ionized solution, which contains 75 chemical elements. These are solid minerals (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 the ambient temperature. Let's give brief description some of them.

Water is a solvent. Since water is a solvent, we can judge that all waters are gas-salt solutions of different chemical compositions and different 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. 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)

Lines on a map connecting points with the same salinity are called isohalines.

Fresh water salinity(see Table 1) is on average 0.146%o, and sea - on average 35 %O. Salts dissolved in water give it a bitter-salty taste.

About 27 of the 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 salty solutions of the earth's interior and gases, its salinity was original. There is reason to believe that in the first stages of the formation of the ocean, its waters differed little in salt composition from river waters. Differences emerged 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 shown by fossil remains, developed no later than the Proterozoic.

In addition to chlorides, sulfites and carbonates, almost all known on Earth were found in sea water. chemical elements, including noble metals. However, the content of most elements in sea water is negligible; for example, only 0.008 mg of gold per 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 climate (the ratio of precipitation and evaporation from the ocean surface), the formation or melting of ice, sea currents, and near 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 influenced 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 zonation.

In 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, water salinity is greater near the western shores of the continents, where currents bring saltier subtropical waters, and less salinity is near the eastern shores, where cold currents bring less salty water.

Seasonal changes in water salinity occur in subpolar latitudes: in the fall, due to the formation of ice and a decrease in the strength of river flow, the salinity increases, and in the spring and summer, due to the melting of ice and an increase in river flow, the salinity decreases. Around Greenland and Antarctica in summer period salinity becomes less as a result of the melting of nearby icebergs and glaciers.

The saltiest 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%).

Among parts of the ocean - seas and bays - the maximum salinity is observed in areas limited by deserts, for example, in the Red Sea - 42%c, in the Persian Gulf - 39%c.

The salinity of water determines its density, electrical conductivity, ice formation and many other properties.

Gas composition of ocean water

In addition to various salts, various 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 relatively little space 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 the 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 cm3/l of nitrogen can dissolve in water, at 5 °C - 7.1 and 12.7 cm3/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 (subtropical and tropical) latitudes, which affects the development of organic life - the richness of the former and the relative poverty of the latter waters; 2) at 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 promotes 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 spent on the respiration of plants and animals in the upper layers of sea waters and on the oxidation of various substances. In the depth range of 600-2000 m there is a layer oxygen minimum. A small amount of oxygen here is combined with a high content of carbon dioxide. The reason is the decomposition in this layer of water 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 seawater is much less than in the atmosphere. This gas is mainly released into water from the air by the breakdown of organic matter, but is also produced by 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 waters.

Heat capacity of ocean waters

Water is one of the most heat-intensive bodies in nature. The heat capacity of just 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 arriving at its surface (Fig. 2). Due to this circumstance, the ocean slowly warms up and slowly releases heat. Due to the high heat capacity, everything water bodies are powerful heat accumulators. As the water cools, it gradually releases its heat into the atmosphere. Therefore, the World Ocean performs the function thermostat of our planet.

Rice. 2. Dependence of heat capacity 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 vaporization water - 597 cal/g, and heat of fusion - 79.4 cal/g - these properties are very important for living organisms.

Ocean temperature

Index thermal state ocean temperature.

Average ocean temperature- 4 °C.

Despite the fact that the surface layer of the ocean acts as a thermostat for the Earth, in turn, the temperature of sea waters depends on heat balance(heat inflow and outflow). Heat inflow consists of , and heat consumption consists 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 exchange is not large, its significance is enormous. It is with its help that planetary heat redistribution occurs through the atmosphere.

At the surface, ocean temperatures range from -2°C (freezing point) 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 approximately 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 in February. In the Southern Hemisphere the opposite is true.

Since it has thermal relationships with the atmosphere, the temperature of surface waters, like the air temperature, depends on the latitude of the area, i.e., it is subject to the law of zonation (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. Thus, thanks to warm currents in tropical latitudes, temperatures in the western oceans are 5-7 °C higher than in the east. However, in the Northern Hemisphere, due to warm currents in the eastern 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 - about -1.5 (-1.7) °C. Here the water temperature is mainly influenced by ice phenomena. In the fall, heat is released, softening the temperature of the air and water, and in the spring, heat is spent on melting.

Table 2. Average annual temperatures of ocean surface waters

The coldest of all oceans- Northern Arctic, and the warmest— The Pacific Ocean, since its main area is located in equatorial-tropical latitudes (average annual water surface temperature -19.1 ° C).

An important influence on the temperature of ocean water is exerted by the climate of the surrounding areas, as well as the time of year, since solar heat, which heats the upper layer of the World Ocean, depends on this. The highest water temperature in the Northern Hemisphere is observed in August, the lowest in February, and vice versa in the Southern Hemisphere. Daily fluctuations in sea water temperature at all latitudes are about 1 °C, highest values 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 out, decreasing to 2.0-3.0 ° C, and in polar latitudes - to tenths of a degree above zero, after which it either decreases very slowly or even increases 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, there are two main layers of water vertically in the World Ocean: warm superficial And powerful cold, extending to the bottom. Between them there is a transition temperature jump layer, or main thermal clip, within it there is a sharp drop in temperature.

This picture of the vertical distribution of water temperature in the ocean is disrupted at high latitudes, where at a depth of 300-800 m a layer of warmer and saltier water coming from temperate latitudes can be traced (Table 3).

Table 3. Average ocean water temperatures, °C

Change in water volume with temperature change

A sharp increase in the volume of water when freezing- This is a peculiar property of water. With a sharp drop 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 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, the opposite process of expansion occurs—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 higher the salinity, the greater the density of the water (Fig. 3). Thus, 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 with the highest density is not +4 °C, like fresh water, but negative (-2.47 °C at a salinity of 30% and -3.52 °C at a salinity of 35%o

Rice. 3. Relationship between the density of sea ox 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 Circle. In winter, polar waters descend 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 revealed (Fig. 4).

Rice. 4. Dependence of seawater density (L"=35%o) on pressure at different temperatures

The ability of water to self-purify

This important property water. During 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 disrupted.

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 is a lot of suspended matter, it is greenish, yellow, and brown.

In the open part of the ocean, water transparency is higher than near the coast. In the Sargasso Sea, water transparency is up to 67 m. During the period of plankton development, 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 (nightlight, 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 vessels locate schools of fish in seawater.

Sound conductivity - acoustic properties of water. Found in the oceans sound-diffusing my And underwater "sound channel" possessing sound superconductivity. The sound-dissipating layer rises at night and falls during the day. It is used by submariners to dampen noise from submarine engines, and by fishing vessels to detect schools of fish. "Sound
signal" is used for short-term forecast of tsunami waves, in underwater navigation for ultra-long-distance transmission of acoustic signals.

Electrical conductivity sea ​​water is high, it is directly proportional to salinity and temperature.

Natural radioactivity sea ​​waters are small. But many animals and plants have the ability to concentrate radioactive isotopes, so seafood catches are tested for radioactivity.

Mobility- 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. As it moves, the water is mixed, which allows waters of different salinity, chemical composition and temperature to be evenly distributed.

It is a well-known hackneyed, but nevertheless true, remark that our planet should be called not Earth, but Ocean. In fact, the World Ocean occupies 361 million km 2, or 71% of the entire surface of the planet. The most important global consequence of this relationship between 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 heating water and turbulent heat exchange between the surface layers of water and the lower layers of the 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 evaporation of water, an important component of the global heat balance.

The mass of the ocean makes up 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 greatest thermal inertia among geospheres. It plays a critical role in shaping the current climate of the planet, its spatial distribution and variability over time. The effect of wind on the upper layer of water determines the main features of ocean circulation in the surface zone. Ocean circulation ensures the 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, taking 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 flow of heat, fresh water and momentum at the ocean surface. Thus, climate evolution and ocean evolution are interconnected.

The deep zones of the ocean, to a much lesser extent than the surface zones, obey the law of geographic zonation, and more often than not they do not. The main deep and 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 at the surface of the ocean and changes in the degree of this participation are the most important factor in changing the main features of the ecosphere.

The deep (depth 2000-4000 m) and bottom (deeper than 4000 m) zones of the World Ocean make up 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 strata. The vertical circulation of ocean waters, under the influence of differences in the density of water 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 thousands of years or more. The release or, conversely, accumulation of such heat reserves may be decisive in long-term climate changes.

The low temperature of the World Ocean and its enormous thermal inertia play a crucial paleogeographical role. The deep layers are not only a good heat regulator of the Earth's system. The strengthening or weakening of heat exchange between the deep layers of the ocean and its surface appears to play a decisive role in deep and long-term transformations of the Earth's climate and, accordingly, in changes in its landscapes. In this case, changes in the heat exchange of the deep ocean masses with the surface ones, as well as the distribution of surface currents, can change over the course of decades, i.e. extremely quickly, taking into account the size of the World Ocean, which can lead to an equally rapid change in the natural situation.

The world's oceans are 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.) The salinity of water varies in space, but its chemical composition (in% of the whole) remains constant. The annual influx of salts into the ocean is approximately seven orders of magnitude (10 7 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 10¹ºt of carbon in solution, suspended and living forms. On land, in living organisms, soils and decaying organic matter, carbon is approximately 20 times less. Physicochemical 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). The limiting factor is usually nutrients.

Primary production is formed in the upper, well-lit layers of water, where nutrients come either from plankton, dying at the same depths, or from land and from the atmosphere. When plankton die, carbon-containing residues sink into the cold, deep layers of the ocean and to the bottom. Ultimately, 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 general content carbon in the deep and bottom zones of the ocean. Bio-geo-chemical processes associated with the absorption of carbon dioxide occur predominantly in the surface zone of the ocean, while the deep and bottom zones play a critical role in the long-term accumulation of carbon. The process is currently being intensively studied, but is still not well understood.

The main features of the relief of the bottom of the World Ocean

The structure of the ocean earth's crust different from continental: there is no granite layer inherent in the latter.

The thickness of the continental crust at sea level is about 30 km. The velocity of seismic waves in its upper half corresponds to the velocities in granite 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 “basement” - 0.5 km thick, a crust 4 km thick, and at a depth of about 10 km the mantle begins.

There are four zones at the bottom of the World Ocean.

The first zone is the underwater margin of the continents. The underwater continental margin is the margin of the continents submerged by ocean waters. It, in turn, consists of a shelf, a continental slope and a continental foot. The shelf is a coastal bottom plain with rather shallow depths, essentially 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 retreats of the sea, vast areas of the shelf turned into 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 edge. Below this edge, a continental slope extends towards the ocean - a zone of ocean or seabed narrower than the shelf, with a surface slope of several degrees. Often the continental slope takes the form of a ledge or a series of ledges with a steepness of 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 marginal seas, chains of predominantly volcanic islands in the form of arcs and narrow linear depressions - deep-sea trenches, with which deep faults that go under the mainland coincide.

On the outskirts Pacific Ocean, in the areas of the Mediterranean, Caribbean seas, and the Scotia Sea (Scotia), the underwater margins of the continents are in contact not directly with the ocean bed, 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 powerful mainly due to the sedimentary layer. From the outside, these pools are surrounded 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.

On the oceanic side of the island arcs there are deep-sea trenches - there is no large continental crust. Instead, there is an terrestrial, narrow, but very deep (6 - 11 km deep) depression developed here. They stretch parallel to the island arcs and correspond to the outcrops of ultra-deep 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 tilted towards the continents. The vast majority of earthquake sources are confined to them. Thus, the areas of deep-sea trenches, island arcs and deep-sea marginal seas are characterized 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 - main - zone of the bottom of the World Ocean - the ocean bed, is distinguished by the development of the earth's crust of an exclusively oceanic type. The ocean floor occupies more than half of its area at depths of up to 6 km. On the ocean floor there are ridges, plateaus, and hills that divide it into basins. Bottom sediments are represented by various silts of organic 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 admixtures of other metals.

Oceanic ridges are quite clearly divided into two types: domed-block and blocky. Dome-block structures are basically arched, linearly elongated uplifts of the oceanic crust, usually broken by transverse faults into separate blocks (the Hawaiian Ridge, which forms the underwater base of the archipelago of the same name).

In addition to ridges, there are many hills, or oceanic plateaus, known in the World Ocean. 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 in oceanic basins is the relief of abyssal hills. This is the name given to countless hills ranging in height from 50 to 500 m, with a base diameter ranging 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 on the ocean floor. Some underwater years with flattened tops are called guyots. It is believed that these peaks once rose above the ocean level until their peaks 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 sediment.

The fourth zone is located in the central parts of the oceans. These are the largest forms of relief on the ocean floor - mid-ocean ridges - giant linearly oriented arched rises of the earth's crust. During the formation of an arch, the greatest stresses arise not at its top; here faults are formed, along which parts of the arch descend, and grabens, the so-called, are formed. 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 rises 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. North of the parallel of Rodrigues Island, one branch - the Arabian-Indian Ridge - goes north, continuing with a number of relief forms on the bottom of the Gulf of Aden and the Red Sea, and the other branch follows to the east and passes into the mid-ocean ridge of the Pacific Ocean - the South Pacific and East Pacific raising. Mid-ocean ridges are probably young Cenozoic formations. Because ridges are the result of crustal stretching, 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 in 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 bulk of the Earth's water shell is formed by the salty waters of the World Ocean, covering 2/3 of the Earth's surface. Their volume is approximately 1379106 km3, while the volume of all land waters (including glaciers and groundwater to a depth of 5 km) is less than 90106 km3. Since oceanic waters make up about 93% of all waters in the biosphere, we can assume that their chemical composition determines the main features of the composition of the hydrosphere as a whole.

The modern chemical composition of the ocean is the result of its long-term changes under the influence of the activities of living organisms. The formation of the primary ocean was caused by the same processes of degassing of the solid matter of the planet that led to the formation of the gaseous shell of the Earth. For this reason, the composition of the atmosphere and hydrosphere is closely related, and their evolution also occurred interconnectedly.

As noted earlier, the degassing products were dominated by water vapor and carbon dioxide. From the moment the planet's surface temperature dropped below 100 °C, water vapor began to condense and form primary reservoirs. A process of water circulation arose on the surface of the Earth, which marked the beginning of the cyclic migration of chemical elements in the land-ocean-land system.

In accordance with the composition of the gases released, the first accumulations of water on the surface of the planet were acidic, enriched mainly in HC1, as well as HF, H3BO3, and H2S. Ocean water has gone through many cycles. Acid rain energetically destroyed aluminosilicates, extracting from them easily soluble cations - sodium, potassium, calcium, magnesium, which accumulated in the ocean. Cations gradually neutralized strong acids, and the waters of the ancient hydrosphere acquired a chlorine-calcium composition.

Among the various processes of transformation of degassed compounds, the activity of condensations of thermo-lithotrophic bacteria obviously occurred. The appearance of cyanobacteria that lived in water, which protected them from harmful ultraviolet radiation, marked the beginning of photosynthesis and the biogeochemical production of oxygen. The decrease in the partial pressure of CO2 due to photosynthesis contributed to the precipitation of large masses of carbonates Fe2+, then Mg2+ and Ca3+.

Free oxygen began to flow into the waters of the ancient ocean. Over a long period of time, the reduced and under-oxidized compounds of sulfur, ferrous iron and manganese were oxidized. The composition of ocean water acquired a chloride-sulfate composition, close to the modern one.

Chemical elements in the hydrosphere are found in various forms. Among them, the most common are simple and complex ions, as well as molecules in a state of highly dilute solutions. Common ions are sorption associated with particles of colloidal and subcolloidal sizes present in seawater in the form of a thin suspension. A special group consists of elements of organic compounds.

The total amount of dissolved compounds in seawater (salinity) in surface layers oceans and marginal seas ranges from 3.2 to 4%. In inland seas, salinity varies over a wider range. The average salinity of the World Ocean is assumed to be 35%.

Back in the middle of the 19th century. Scientists have discovered a remarkable geochemical feature of ocean water: despite fluctuations in salinity, the ratio of major ions remains constant. The salt composition of the ocean is a kind of geochemical constant.

As a result of the persistent work of scientists from many countries, extensive analytical material has been accumulated, characterizing the content of not only the main but also trace chemical elements in the water of the seas and oceans. The most substantiated data on the average values ​​(clarks) of chemical elements in the water of the World Ocean are given in reports by E.D. Goldberg (1963), A.P. Vinogradov (1967), B. Mason (1971), G. Horn (1972), A.P. Lisitsina (1983), K.N. Turekiana (1969). In table 4.1 uses the results of mainly the last two authors.

As can be seen from the data presented, the bulk of the dissolved compounds are chlorides of common alkali and alkaline earth elements, less sulfates are contained, and even less hydrocarbonates. The concentration of trace elements, the unit of measurement of which is μg/l, is three mathematical orders of magnitude lower than in rocks. The range of clarke values ​​of scattered elements reaches 10 mathematical orders, i.e. approximately the same as in the earth's crust, but the ratios of elements are completely different. Bromine, strontium, boron and fluorine are clearly dominant, with concentrations above 1000 µg/l. Iodine and barium are present in significant quantities, their concentration exceeds 10 μg/l.

Table 4.1

Some of the metals in water - molybdenum, zinc, uranium, titanium, copper - have a concentration of 1 to 10 μg/l. The concentration of nickel, manganese, cobalt, chromium, mercury, cadmium is much lower - hundredths and tenths of μg/l. At the same time, iron and aluminum, which play the role of the main elements in the earth's crust, have lower concentrations in the ocean than molybdenum and zinc. The least dissolved elements in the ocean are niobium, scandium, beryllium and thorium.

To determine some geochemical and biogeochemical parameters, it is necessary to know the concentration of elements not only in sea water, but also in the solid phase of soluble substances, i.e. in the total salts of sea water. The table shows data for the calculation of which the average salinity value is taken to be 35 g/l.

As shown above, the leading factor in the evolution of the chemical composition of the ocean throughout geological history was the total biogeochemical activity living organisms. Organisms play an equally important role in modern processes differentiation of chemical elements in the ocean and the removal of their masses into sediment. According to the biofiltration hypothesis developed by A.P. Lisitsin, planktonic (mainly zooplanktonic) organisms filter about 1.2107 km3 of water through their bodies every day, or about 1% of the volume of the World Ocean. In this case, thin mineral suspensions (particles 1 micron in size or less) are bound into lumps (pellets). Pellet sizes range from tens of micrometers to 1 - 4 mm. Binding thin suspensions into lumps ensures faster settling of suspended material to the bottom. At the same time, part of the chemical elements dissolved in water in the bodies of organisms turns into insoluble compounds. The most common examples of biogeochemical binding of dissolved elements into insoluble compounds are the formation of calcareous (calcite) and silicon (opal) skeletons of planktonic organisms, as well as the extraction of calcium carbonate by calcareous algae and corals.

Among pelagic muds (deep ocean sediments), two groups can be distinguished. The former consist predominantly of biogenic plankton formations, the latter are formed mainly by particles of non-biogenic origin. In the first group, calcareous (carbonate) silts are most common, in the second group - clayey silts. Carbonate silts occupy about a third of the area of ​​the bottom of the World Ocean, clayey silts - more than a quarter. In carbonate sediments, the concentration of not only calcium and magnesium increases, but also strontium and iodine. Silts, where clay components predominate, contain significantly more metals. Some elements are very weakly carried out of solution into silts and gradually accumulate in sea water. They should be called thalassophilic. By calculating the ratio between the concentrations in the sum of soluble salts of sea water and sediments, we obtain the value of the thalassophilicity coefficient CT, which shows how many times more of this element is present in the salt part of ocean water compared to sediment. Thalassophilic elements that accumulate in the dissolved salt part of water have the following CT coefficients:

Knowing the mass of an element in the World Ocean and the amount of its annual supply, it is possible to determine the rate of its removal from the oceanic solution. For example, the amount of arsenic in the ocean is approximately 3.6109 tons, with river runoff bringing 74103 tons/year. Consequently, over a period of 49 thousand years, the entire mass of arsenic is completely removed from the World Ocean.
Many authors have made estimates of the time that elements remain in a dissolved state in the ocean: T.F. Barth (1961), E.D. Goldberg (1965), H.J. Bowen (1966), A.P. Vinogradov (1967), etc. Data from different authors have greater or lesser discrepancies. According to our calculations, periods of complete removal of dissolved chemical elements from the World Ocean are characterized by the following time intervals (in years, in the sequence of increasing periods in each series):

• n*102: Th, Zr, Al, Y, Sc
• n*103: Pb, Sn, Mn, Fe, Co, Cu, Ni, Cr, Ti, Zn
• n*104: Ag, Cd, Si, Ba, As, Hg, N
• n*105: Mo, U, I
• n*106: Ca, F, Sr, V, K
• n*107: S, Na
• n*108: C1, Br

Despite the approximate nature of such calculations, the orders of magnitude obtained allow us to identify groups of trace elements that differ in the duration of their presence in the oceanic solution. The elements that are most intensely concentrated in deep-sea silts have the shortest duration of residence in the ocean. These are thorium, zirconium, yttrium, scandium, aluminum. The periods of presence of lead, manganese, iron, and cobalt in the oceanic solution are close to them. Most metals are completely removed from the ocean over several thousand or tens of thousands of years. Thalassophilic elements remain in a dissolved state for hundreds of thousands of years or more.

Significant masses of trace elements in the ocean are bound by dispersed organic matter. Its main source is dying planktonic organisms. The process of destruction of their remains most actively occurs to a depth of 500-1000 m. Therefore, in the sediments of shelf and shallow continental seas, huge masses of dispersed organic matter of marine organisms accumulate, to which are added organic suspensions carried by river runoff from the land.

The main part of the organic matter of the ocean is in a dissolved state and only 3 - 5% is in the form of suspension (Vinogradov A.P., 1967). The concentration of these suspensions in water is small, but their total mass in the entire volume of the ocean is very significant: 120 - 200 billion tons. The annual accumulation of highly dispersed organic detritus in the sediments of the World Ocean, according to V.A. Uspensky, exceeds 0.5109 tons.

Dispersed organic matter sorbs and entrains a certain complex of trace elements into sediments. Their content can be judged with a certain convention by the microelemental composition of large accumulations of organic matter - deposits of coal and oil. Element concentrations in these objects are usually given relative to the ash; Data in relation to the original, unashed material is no less important.

As can be seen from table. 4.2, the microelement composition of coal and oil is fundamentally different.

Table 4.2

Average concentrations of trace metals in coal and oil, 10-4%

In oil there is a different ratio; there is a significantly higher concentration of many trace elements. The high content of titanium, manganese and zirconium in coals is due to mineral impurities. Among the trace metals, the highest concentrations are typical for zinc, chromium, vanadium, copper and lead.

Many toxic elements (arsenic, mercury, lead, etc.) actively accumulate in organic matter, which are constantly removed from ocean water. Consequently, dispersed organic matter, like suspended minerals, plays the role of a global sorbent, regulating the content of trace elements and protecting the environment of the World Ocean from dangerous levels of their concentration. The amount of trace elements bound in dispersed organic matter is very significant, taking into account that the mass of the substance in sedimentary rocks hundreds of times greater than the total amount of all deposits of hard coal, carbonaceous shale and oil. According to J. Hunt (1972), N.B. Vassoevich (1973), A.B. Ronova (1976) the total amount of organic matter in sedimentary rocks is (1520)1015 tons.

The masses of trace elements accumulated in the organic matter of the Earth's sedimentary strata are measured in many billions of tons.

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hydrosphere (water shell of the Earth), which occupies the vast majority of it (more than $90\%$) and is a collection of water bodies (oceans, seas, bays, straits, etc.) washing land areas (continents, peninsulas, islands, etc.) .d.).

The area of ​​the World Ocean is about $70\%$ of planet Earth, which exceeds the area of ​​all land by more than $2$ times.

The world ocean, as the main part of the hydrosphere, is a special component - the oceanosphere, which is the object of study of the science of oceanology. Thanks to this scientific discipline, the component as well as physical and chemical compositions of the World Ocean are currently known. Let us consider in more detail the component composition of the World Ocean.

The world's oceans can be component-divided into its main independent large parts that communicate with each other - oceans. In Russia, based on established classification, four separate oceans were distinguished from the World Ocean: Pacific, Atlantic, Indian and Arctic. In some foreign countries, in addition to the above four oceans, there is also a fifth - the Southern (or Southern Arctic), which combines the waters of the southern parts of the Pacific, Atlantic and Indian oceans surrounding Antarctica. However, due to the uncertainty of its boundaries, this ocean is not distinguished in the Russian classification of oceans.

Seas

In turn, the component composition of the oceans includes seas, bays, and straits.

Definition 2

Sea- this is a part of the ocean limited by the shores of continents, islands and bottom elevations and differing from neighboring objects in physical, chemical, environmental and other conditions, as well as characteristic hydrological features.

Based on morphological and hydrological characteristics, seas are divided into marginal, Mediterranean and interisland.

Marginal seas are located on the underwater edges of continents, shelf zones, in transition zones and are separated from the ocean by islands, archipelagos, peninsulas or underwater rapids.

The seas that are confined to continental shallows are shallow. For example, the Yellow Sea has maximum depth equal to $106$ meters, and those seas that are located in the so-called transition zones are characterized by depths of up to $4\000$ meters - Okhotsk, Beringovo and so on.

The water of the marginal seas is practically no different in physical and chemical composition from open waters oceans, because these seas have an extensive front of connection with the oceans.

Definition 3

Mediterranean are called seas that cut deeply into the land and are connected with the waters of the oceans by one or more small straits. This feature Mediterranean seas, explains the difficulty of their water exchange with ocean waters, which forms the special hydrological regime of these seas. The Mediterranean seas include the Mediterranean, Black, Azov, Red and other seas. The Mediterranean seas, in turn, are divided into intercontinental and inland.

Interisland seas are separated from the oceans by islands or archipelagos, consisting of rings of individual islands or island arcs. Similar seas include the Philippine Sea, Fiji Sea, Banda Sea, and others. The interisland seas also include the Sargasso Sea, which does not have clearly established and defined boundaries, but has a pronounced and specific hydrological regime and special types of marine flora and fauna.

Bays and Straits

Definition 4

Bay- this is a part of the ocean or sea that extends into the land, but is not separated from it by an underwater threshold.

Depending on the nature of origin, hydrogeological features, forms of the coastline, shape, as well as their location in a particular region or country, bays are divided into: fjords, bays, lagoons, estuaries, lips, estuaries, harbors and others. The Gulf of Guinea, which washes the coast of Central and Western Africa, is recognized as the largest in area.

In turn, oceans, seas and bays are connected to each other by relatively narrow parts of the ocean or sea that separate continents or islands - straits. The straits have their own special hydrological regime and a special system of currents. The widest and deepest strait is the Drake Passage, which separates South America and Antarctica. Its average width is 986 kilometers and its depth is more than 3,000 meters.

Physico-chemical composition of the waters of the World Ocean

Sea water is a highly diluted solution of mineral salts, various gases and organic matter, containing suspensions of both organic and inorganic origin.

A series of physico-chemical, ecological and biological processes constantly occur in sea water, which have direct influence for change general composition solution concentration. The composition and concentration of mineral and organic substances in ocean water are actively influenced by influxes of fresh water flowing into the oceans, evaporation of water from the ocean surface, precipitation on the surface of the World Ocean, and the processes of ice formation and melting.

Note 1

Some processes, such as the activity of marine organisms, the formation and decay of bottom sediments, are aimed at changing the content and concentration in water solids and, as a consequence, a change in the relationship between them. The respiration of living organisms, the process of photosynthesis and the activity of bacteria affect the change in the concentration of dissolved gases in water. Despite this, all of these processes do not disturb the concentration of the salt composition of water in relation to the main elements included in the solution.

Salts and other mineral and organic substances dissolved in water are found primarily in the form of ions. The composition of salts is varied; almost all chemical elements are found in ocean water, but the bulk consists of the following ions:

• $Na^+$
• $SO_4$
• $Mg_2^+$
• $Ca_2^+$
• $HCO_3,\CO$
• $H2_BO_3$

The highest concentrations in sea waters contain chlorine - $1.9\%$, sodium - $1.06\%$, magnesium - $0.13\%$, sulfur - $0.088\%$, calcium - $0.040\%$, potassium - $0.038\%$, bromine – $0.0065\%$, carbon – $0.003\%$. The content of other elements is insignificant and amounts to about $0.05\%.$

The total mass of dissolved matter in the World Ocean is more than $50,000$ tons.

Precious metals have been discovered in the waters and at the bottom of the World Ocean, but their concentration is insignificant and, accordingly, their extraction is unprofitable. Ocean water is very different in its chemical composition from the composition of land waters.

The concentration of salts and salt composition in different parts of the World Ocean is heterogeneous, but the greatest differences in salinity indicators are observed in the surface layers of the ocean, which is explained by exposure to various external factors.

The main factor that makes adjustments to the concentration of salts in the waters of the World Ocean is precipitation and evaporation from the surface of the water. The lowest salinity levels on the surface of the World Ocean are observed in high latitudes, since these regions have an excess of precipitation over evaporation, significant river flow and melting floating ice. Approaching the tropical zone, the salinity level increases. At equatorial latitudes, the amount of precipitation increases, and salinity here decreases again. The vertical distribution of salinity is different in different latitudinal zones, but deeper than $1500$ meters, salinity remains almost constant and does not depend on latitude.

Note 2

Also, in addition to salinity, one of the main physical properties sea ​​water is its transparency. Water transparency refers to the depth at which the white Secchi disk with a diameter of $30$ centimeters ceases to be visible to the naked eye. The transparency of water depends, as a rule, on the content of suspended particles of various origins in the water.

The color or color of water also largely depends on the concentration of suspended particles, dissolved gases, and other impurities in the water. Color can vary from blue, turquoise and blue hues in clear tropical waters to blue-green and greenish and yellowish hues in coastal waters.

In many ways, this geosphere remains mysterious. Thus, the development of astronautics has refuted the “obvious” truth about the zero surface of the World Ocean. It turned out that even in complete calm the water surface has its own relief. Depressions and hills with an absolute excess of tens of meters accumulate over distances of thousands of kilometers, and therefore are invisible. Five planetary anomalies (in meters) are remarkable: Indian minus 112, Californian minus 56, Caribbean plus 60, North Atlantic plus 68, Australian plus 78.

The reasons for such stable anomalies have not yet been clarified. But it is assumed that elevations and decreases in the surface of the World Ocean are associated with gravity anomalies. The multilayer model of the planet provides for an increase in the density of each subsequent layer in depth. The boundaries between underground geospheres are uneven. The mountains of Mohorovicic's surface are twice as high as the terrestrial Himalayas. At depths from 50 to 2900 kilometers, the sources of gravity anomalies can be zones of phase transitions of matter. Due to disturbances, the direction of gravity deviates from the radional direction. It is believed that at a depth of 400 - 900 kilometers there are masses of low density and masses of particularly dense matter. Under positive density anomalies of the ocean surface there are masses of increased density, and under depressions there are decompacted masses. can be used to explain the relief of the World Ocean. The vastness of water-surface anomalies corresponds to large inhomogeneities of the internal surface, which are associated not only with phase transitions of matter, but also with the initially different matter of protoplanetary modules. In the Earth reunited and relatively lightweight material lunar modules and relatively heavy material. In 1955, the Twin City meteorite, composed of 70 percent iron and 30 percent nickel, fell in the southern United States. But the martensitic structure, typical of such meteorites, was not found in the Twin City meteorite. American scientist R. Knox suggested that this meteorite is an unchanged fragment of a planetesimal, from which, in particular, planets were formed billions of years ago. The presence in the depths of the masses of a substance corresponding to the Twin City meteorite will ensure the stable existence of gravity anomalies.

As was said earlier, the anomalies of the surface of the World Ocean and the projections of radiation anomalies coincide spatially. It is possible that disturbances in the gravity field and magnetic field have one internal reason associated with the primary heterogeneity of the planet.

The surface of the World Ocean is carefully studied from manned and automatic satellites. The Geo-3 satellite over the eastern coast of Australia at a distance of 3200 kilometers established a difference in height of the ocean surface of 2 m: the water level at north coast mainland above. The special Sisat satellite, launched in 1978, measures the water surface with an accuracy of 10 centimeters.

No less interesting is the problem of internal waves of the World Ocean. In the middle of the 18th century, B. Franklin, during a sea voyage, noticed that the oil in the lamp did not react to rocking, and a wave periodically appeared in the layer under the oil. B. Franklin's publication was the first scientific report on underwater waves, although the phenomenon itself was well known to sailors.

Sometimes, with a calm wind and little seas, the ship suddenly lost speed. The sailors talked about the mysterious " dead water“, but only after 1945 did systematic research into this phenomenon begin. It turned out that in complete calm, storms of unprecedented force were raging at depth: the height of underwater waves reaches 100 meters! True, the wave frequency ranges from several minutes to several days, but these slow waves penetrate the entire thickness of ocean waters.

It is possible that it was the internal wave that caused the death of the American nuclear submarine Thrasher: the boat was suddenly carried away by the wave to great depths and was crushed.

Some internal ocean waves are caused by tides (the period of such waves is half a day), others by wind and currents. However, such natural explanations are no longer enough, so numerous ships conduct observations in the ocean around the clock.

Man has always tried to penetrate into the depths of the World Ocean. The first descent in an underwater bell on the Tagus River was recorded in 1538. In 1911, in the Mediterranean Sea, the American G. Hartmann sank to a record depth of 458 meters. Experimental submarines reached 900 meters (Dolphin in 1968). Bathyscaphes stormed the super depths. On January 23, 1960, the Swiss J. Picard and the American D. Walsh sank to a depth of 10,919 meters to the bottom of the Mariana Trench. These are not only cases demonstrating the technical and volitional capabilities of a person, but also a direct immersion in the “ocean of mysteries.”

Over the course of geological time, the salt balance of the World Ocean and the solid earth's crust has reached. The average salinity of ocean water is 34.7 ppm, its fluctuations are 32-37.5 ppm.

Main ions of the World Ocean (in percent): CI 19.3534, SO24- 2.707, HCO 0.1427, Br- 0.0659, F- 0.0013, H3BO3 0.0265, Na+ 10.7638, Mg2+ 1.2970, Ca2+ 0.4080, K+ 0.3875, Sr2+ 0.0136/

The ocean is replenished with ions from various sources as a result of degassing of the planet's depths, destruction of the ocean bed, wind erosion, and the biological circulation of matter. A large number of ions come with river runoff. All land, with a total river flow of 33,540 cubic kilometers, supplies over two billion tons of ions per year.

The water mass of the World Ocean is heterogeneous. By analogy with the atmosphere, scientists began to identify volumetric boundaries of masses in the World Ocean. But if cyclones and anticyclones with a diameter of a thousand kilometers are common in the atmosphere, then in the ocean eddies are 10 times smaller. The reasons are the greater hydrostatic stability of water masses and the great influence of lateral coastal boundaries; In addition, the density, viscosity and thickness of the ocean are different. But the main thing is that waters of different salinity and impurities do not mix well. Internal water currents, wind and waves create a homogeneous layer at the surface of the ocean. The vertical stratification of the World Ocean is very stable. But there are limited “windows” for the vertical movement of waters of different temperatures and salinities. Particularly important are the “upwelling” zones, where cold deep waters rise to the sea surface and carry out significant masses and nutrients.

The boundaries between water masses are clearly visible from airplanes and space satellites. But this is only part of the boundaries of water masses. A significant proportion of boundaries are hidden at depth. K. N. Fedorov draws attention to an amazing phenomenon: water Mediterranean Sea, pouring out in the bottom layer of the Strait of Gibraltar, flow down the slopes of the shelf and continental slope, then break away from the ground at depths of about a thousand meters and, in the form of a layer hundreds of meters thick, cross the entire Atlantic Ocean. In the direction from east to west, the layer of Mediterranean water is divided into thin layers, which, due to higher salinity and elevated temperature, are clearly visible at a depth of 1.5 - 2 kilometers in the Sargasso Sea. The waters of the Red Sea, pouring into Indian Ocean. In the Red Sea itself, thermal ore-bearing brines are covered by a two-kilometer layer of water, the temperature of which is below 20-30 ° C. However, they do not mix. Thermal waters are heated to 45-58 °C, highly mineralized (up to 200 grams per liter). The upper limit of thermal waters is represented by a series of sharp density steps, where heat and mass exchange occurs.

Thus, the water masses of the World Ocean are divided according to natural reasons into isometric areas, layers and thinnest interlayers. In practice, these properties are widely used in hidden passages submarines. However, this is not all. It turns out that it is possible without concrete dams and fences to artificially create poorly surmountable boundaries of waters of different salinity and temperature, and this is the path to the creation of controlled aquaculture zones. For example, there are proposals to create artificial “upwelling” off the coast of Brazil using pumps to “fertilize” surface waters, which will increase the possibilities.