Physical and chemical properties of ocean water briefly. Basic physical and chemical properties of ocean (sea) water

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 ambient temperature. 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 of 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 %about. 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

An indicator of the thermal state of the ocean is 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

	Average annual temperature, "C			Average annual temperature, °C
	North hemisphere	Southern Hemisphere		North hemisphere	Southern Hemisphere

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, °C

	Depth, m
equatorial
tropical
Polar

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.

Physiochemical properties.Ocean water is 96.5% pure water by weight, with the rest being dissolved salts, gases, and suspended insoluble particles. In the water of the oceans, 44 chemical elements have been found in a dissolved state. In percentage terms, the share of various dissolved salts accounts for the following amount: chlorides 88.7, sulfates 10.7, carbonates 0.3, others 0.2. Most of the salt contentNaCl), which is why ocean water tastes salty; magnesium salts (MgCl 2 , MgSO 4 ) give it a bitter taste. The constancy of the salt composition of the ocean is characteristic. One of the reasons for this is the continuous mixing of the water. Oceanic waters emerged from the bowels of the Earth with the initial salinity.

The average salinity of the waters of the World Ocean is 35 ° / 00. Changes in salinity are caused by changes in the balance of salts, mainly associated with changes in the balance of fresh water.

Salinity changes are well pronounced down to a depth of about 1500 m. At greater depths, the salinity of the World Ocean remains almost unchanged, ranging from 34.7 to 34.9%.

The salinity of water on the surface of the seas can be very different from the salinity of water in the open part of the ocean. If the salinity of the sea is less than the salinity of the adjacent part of the ocean, then denser ocean water penetrates into the sea and sinks, filling its depths. If the sea is saltier than the neighboring part of the ocean, then the water moves along the bottom towards the ocean, along the surface - towards the sea.

Gases are dissolved in ocean water. Oxygen, nitrogen, carbon dioxide, hydrogen sulfide, ammonia and methane predominate. Gases enter the water from the atmosphere, during chemical and biological processes in water, during underwater eruptions.

The density of water on the surface of the ocean varies from 0.996 to 1.083. With an increase in salinity and a decrease in water temperature, the density increases. The density of water increases with depth. For every 10 m depth pressure increases by 1 atm. Pressure at a depth of 10,000 m equals 1119atm.

thermal regime.The main source of heat received by the ocean is solar radiation. In addition, the ocean receives heat due to the absorption of long-wave radiation of the atmosphere, heat released during condensation of moisture and ice formation, and during chemical and biological processes. The ocean receives heat brought by precipitation, river waters, air in contact with water, and warm currents. The temperature of the deep layers of the ocean is affected by the internal heat of the Earth and the adiabatic heating of the sinking water.

The ocean consumes heat mainly for the evaporation of water from its surface, for heating the adjacent layer of air, for heating the cold water of rivers and ocean currents, for the melting of ice, and for other processes.

The diurnal amplitudes of water temperature on the ocean surface are much less than the diurnal amplitudes of air temperatures above water. During the day, heat comes from solar radiation, but is also consumed as a result of increased evaporation of moisture. At night, water radiates heat into the atmosphere and receives it when moisture condenses on the cooling surface of the water. Temperature fluctuations are also smoothed out due to the high heat capacity of water. The daily amplitude of water temperature on the ocean surface does not exceed 0.5° on average.

The annual amplitudes of water temperature on the ocean surface are greater than the daily ones. They depend on the annual course of the radiation balance, on sea currents, on prevailing winds, and on latitude. At low latitudes they are 1°, at high latitudes 2°.

The highest average annual water temperatures (27-28°) are observed in equatorial latitudes. In tropical latitudes, under the influence of currents at the same latitude, the temperature of the water on the ocean surface near the western coast is higher than that of the eastern coast. This is facilitated by the trade winds, which drive water away from the eastern shores. In place of the departed water, the underlying, colder layers of it rise. In temperate latitudes of the northern hemisphere, due to currents near the eastern shores, the water temperature is higher than that of the western ones. In the southern hemisphere, south of 40°, the latitudinal distribution of temperature is hardly disturbed. In the polar latitudes, the water temperature drops to 0 ° and even to -2 °.

The temperature in the ocean tends to decrease with depth. Significant temperature changes occur only in the upper layers of the ocean (200-1000 m). At great depths, the temperature is from + 2 to -1 °.

The temperature on the surface of the seas under the influence of land, water exchange with the ocean, the influx of river waters and other causes can differ significantly from the temperature of the ocean at the same latitude. The highest temperature (up to + 36 °) is on the surface of tropical seas. The change in temperature with depth depends primarily on water exchange with neighboring parts of the ocean.

ice regime. The freezing point of water in the oceans depends on its salinity. The higher the salinity, the lower the freezing point.

The formation of ice begins with the appearance of fresh crystals.

When ice crystals accumulate in calm weather, a thin ice film is formed - salo. Near the shore, a strip of ice appears motionlessly attached to it - save. Gradually growing, zaberegi turn into landfast ice. At a calm state of the water surface, when fat freezes, transparent thin ice appears. During the excitement, separate ice disks appear - pancake ice. When pancake ice freezes, a continuous ice cover is formed.

In the high latitudes of the northern hemisphere, the ice formed during the winter does not have time to melt during the summer, so there are ices of different ages - from one-year to multi-year ones. First-year ice thickness 1-2.5 m, perennial 3 m and more. Perennial thick floating ice occupying the central parts of the Arctic Ocean are called pack ice. They occupy 70-80% of the total ocean ice area.

Spaces of flat ice are intersected by cracks. When compressed, the ice breaks along the cracks, the ice floes stand on edge and freeze, forming hummocks. When drifting ice is crushed, vast ice fields (up to 10 km in diameter), coarse ice (20-100 m) and finely broken ice (less than 20m).

By origin, in addition to sea ice, in the oceans and seas there are river and continental ice that has moved from land. Fragments of continental ice form floating ice mountains - icebergs. They are especially common in Antarctica.

The melting of ice begins with contaminated areas (usually from the coast). Lakes form on the surface of the ice as a result of melting. In the coastal strip there are continuous strips of clear water - water banks, gradually turning into polynyas. Melting ice under the influence of waves and currents breaks up into separate ice floes. The ice floes break, turn into ice porridge and, finally, the ice breaks up into crystals.

Ice covers about 15% of the world's oceans. The boundaries of the ice position experience significant seasonal changes. In the Arctic, south of the area of ​​solid ice in the Central Basin of the Arctic Ocean, there is an area of ​​non-continuous floating ice. Floating ice is also found in the Bering and Okhotsk Seas, in the Hudson Bay, a strip around Greenland and off the coast of the Labrador Peninsula. In the Antarctic in winter, ice forms a dense, wide ring around the mainland. In summer, fast ice breaks and the ice is carried northward. The boundary of floating ice in the southern hemisphere reaches 50-60 ° S. sh. Icebergs go far beyond the distribution of floating ice. They form mainly near Antarctica, Greenland and the islands of the Canadian Arctic Archipelago. A large mass and deep sediment in the water allows icebergs to reach 40-50 ° N in the northern hemisphere. latitude, and in the south, where the icebergs are larger, - 30-40 ° S. sh. Icebergs up to 157 m and diameter up to 170km.

Ice has an effect on the climate. The water under the ice is protected from deep cooling in winter, and from warming up in summer. The heat released during ice formation moderates winter air temperatures. Heat absorbed by melting ice lowers summer temperatures.

- Source-

Bogomolov, L.A. General geography / L.A. Bogomolov [and d.b.]. – M.: Nedra, 1971.- 232 p.

Post Views: 322

The World Ocean is the main part of the hydrosphere - the water shell of the Earth. Its waters cover 361 million km2, or 70.8%, of the surface of the globe, which is almost 2.5 times the land area (149 million km2, or 29.2%). The most important consequence of such a global ratio of land and sea is the influence of the World Ocean on the water and heat balance of the Earth. About 10% of solar radiation absorbed by the ocean surface is spent on heating and turbulent heat exchange between the surface water layers and the lower atmosphere. The remaining 90% of the heat is spent on evaporation. Evaporation from the ocean surface is both the main source of water in the global hydrological cycle and a consequence of the high latent heat of water evaporation, which is an important component of the Earth's global heat balance. The water area of ​​the World Ocean consists of the Atlantic, Pacific, Indian, Arctic and Southern oceans, marginal seas (Barents, Bering, Okhotsk, Japanese, Caribbean, etc.), inland seas (Mediterranean, Black, Baltic). Having no connection with the World Ocean, the Caspian and Aral sea-lakes are conditionally called seas solely because of their large size. At present, these are internal closed water bodies, and in the Quaternary time they were connected to the World Ocean.

At least 1.4 billion km3 of water is concentrated in the World Ocean, which is about 94% of the volume of the hydrosphere. These huge masses of water are in constant motion. The geological processes occurring in the World Ocean are diverse and are interrelated phenomena. They consist of the following processes:

Destruction, or abrasion (from the Latin “abrado” - I shave, scrape off), rock masses that make up the coast and part of the shallow water;

Transfer and sorting of destruction products brought from land;

Accumulation, or accumulation, of various precipitation. For a long time the bottom of the World Ocean and its sediments remained unexplored. Only since the middle of the 20th century did targeted research of the World Ocean begin with specially built research ships. Initially, various geophysical instruments installed on ships were used to study the bottom of the World Ocean, and rock samples were delivered by special trawls - dredges. As a result of these works, unique information about the topography of the bottom of the World Ocean was obtained.

Physical and chemical properties of the waters of the seas and oceans

Salinity and chemical composition of waters. In sea water, a large number of substances are in a dissolved state. The total content of dissolved salts in sea water is called its salinity (5) and is expressed in ppm (% o). For the average salinity of ocean waters, a value of about 35% o is taken. This means that 1 liter of water contains about 35 g of dissolved salts (the average salinity of sea water). The salinity of the surface waters of the World Ocean ranges from 32 to 37% c, and such fluctuations are associated with climatic zoning, which directly affects the evaporation of waters. In arid zones, where evaporation predominates, salinity increases, while in humid areas and in places where large rivers drain, salinity decreases. Salinity varies widely in inland seas. In the Mediterranean Sea it is 35-39%o, in the Red Sea it increases to 41-43%o, and in the seas located in humid areas, mainly due to the large influx of fresh water, salinity decreases. In the Black Sea, it is 18 - 22% o, in the Caspian - 12-15% o, in the Azov - 12% o, and in the Baltic - 0.3 - 6% o. Such a low salinity of the Baltic Sea is due to the large volume of river runoff. After all, such full-flowing rivers as the Rhine, Vistula, Neva, Neman, etc. carry their waters into this sea. Caspian Sea.

In the waters of the seas and oceans, almost all the chemical elements of the Periodic Table of D. I. Mendeleev are present. The content of some is so high that it is their ratio that determines the salinity of sea and ocean waters, while the number of others is thousandths and even ten thousandths of a percent. When comparing cations and anions, it turns out that chlorides (89.1%) predominate in the salt composition of sea water, sulfates (10.1%) are in second place, then carbonates 0.56%, and bromides make up only 0.3% .

Gas mode. In the waters of the World Ocean, various gases are in a dissolved state, but the main ones are oxygen, carbon dioxide and, in some places, hydrogen sulfide. Oxygen enters seawater both directly from the atmosphere and through phytoplankton photosynthesis. The main role in the redistribution of gases is played by the global ocean circulation. Thanks to it, the flow of oxygen-rich cold waters from high latitudes to the equator and surface waters to the bottom part occurs.

Carbon dioxide is partly dissolved in sea water, and partly it is chemically bound in the form of bicarbonates Ca(HC03) or carbonates (CaCO3). The solubility of CO2 in sea water depends on the sea water temperature and increases with its decrease. Therefore, the cold waters of the Arctic and Antarctic contain more carbon dioxide than the waters of low latitudes. A significant content of CO2 is noted in the near-bottom cold waters at depths below 4000 m. This affects the dissolution of carbonate shells of dead organisms that sink from the surface to the bottom.

An anomalous gas regime is observed in some marine basins. A classic example is the Black Sea, where, according to N. M. Strakhov, at depths of 150-170 m, the water is largely depleted in oxygen and contains large amounts of hydrogen sulfide. Its quantity greatly increases in the bottom layers. Hydrogen sulfide is formed due to the vital activity of sulfate-containing bacteria, which reduce sulfates from sea water to hydrogen sulfide. Hydrogen sulfide contamination is caused by a violation of the free water exchange between the Black Sea and the waters of the Mediterranean Sea. In the Black Sea, there is a stratification of water by salinity. In the upper part there are desalinated waters (17-18%o), and below are salty (20-22%o). This excludes vertical circulation and leads to a violation of the gas regime, and then to the accumulation of hydrogen sulfide. The lack of oxygen in the deeper layers contributes to the development of recovery processes. Hydrogen sulfide contamination in the bottom part of the Black Sea reaches 5 - 6 cm3/l. In addition to the Black Sea, hydrogen sulfide contamination was found in some Norwegian fiords.

sea ​​water temperature. The temperature distribution of the surface layers of the waters of the World Ocean is closely related to climatic zonality. The average annual temperature in high latitudes varies from 0 - 2 °С and reaches maximum values ​​of about 28 °С in equatorial latitudes. In temperate latitudes, water temperature experiences significant seasonal fluctuations ranging from 5 to 20 °C. The water temperature changes with depth, reaching only 2-3 °C in the near-bottom parts at considerable depths. In the polar regions, it drops to negative values ​​of the order of -1.0 -1.8 °C.

The transition from the upper layer of high temperature water to the lower layer of low temperature occurs in a relatively thin layer called the thermocline. This layer coincides with the 8-10° isotherm and is located at a depth of 300-400 m in the tropics and 500-1000 m in the subtropics. The general patterns in the temperature distribution are violated by surface warm and cold currents, as well as by bottom currents.

pressure and density. Hydrostatic pressure in the oceans and seas corresponds to the mass of the water column and increases with depth, reaching a maximum value in the deep parts of the ocean. The average density of sea water is approximately 1.025 g/cm3. In cold polar waters it increases to 1.028, and in warm tropical waters it decreases to 1.022 g/cm3. All these fluctuations are due to changes in the salinity and temperature of the waters of the World Ocean.

Relief elements.

There are four main stages of the relief of the ocean floor: the continental shelf (shelf), the continental slope, the ocean floor and deep-water depressions. Within the ocean floor, the greatest differences in depths and grandiose mountain structures are observed. Therefore, oceanic basins, mid-ocean ridges and oceanic uplifts began to be distinguished within the bed.

Shelf (mainland)- a shallow marine terrace that borders the mainland and is its continuation. In essence, the shelf is a submerged surface of ancient land. This is an area of ​​the continental crust, which is characterized by a flat relief with traces of flooded river valleys, Quaternary glaciation, and ancient coastlines.

The outer boundary of the shelf is the edge - a sharp bend in the bottom, beyond which the continental slope begins. The average depth of the shelf crest is 133 m, but in specific cases it can vary from several tens to a thousand meters. Therefore, the term "continental shallow" is not suitable for the name of this element of the bottom (better - shelf). The shelf width varies from zero (African coast) to thousands of kilometers (Asia coast). In general, the shelf occupies about 7% of the area of ​​the World Ocean.

continental slope- the area from the edge of the shelf to the continental foot. The average angle of inclination of the continental slope is about 6°, but often the steepness of the slope can increase up to 20-30°. The width of the continental slope due to the steep drop is usually small - about 100 km. The most characteristic landforms of the continental slope are underwater canyons. Their tops often cut into the edge of the shelf, and the mouth reaches the foot of the mainland.

foot of the mainland- the third element of the bottom relief, located within the continental crust. The continental foot is a vast sloping plain formed by sedimentary rocks 3-5 km thick. The width of this hilly plain can reach hundreds of kilometers, and the area is close to the areas of the shelf and continental slope.

Ocean bed- the deepest part of the ocean floor, occupying more than 2/3 of the entire area of ​​\u200b\u200bthe World Ocean. The prevailing depths of the ocean floor range from 4 to 6 km, and the bottom relief is the most calm. The main elements are oceanic basins, mid-ocean ridges and oceanic uplifts.

oceanic basins- extensive gentle depressions of the ocean floor with depths of about 5 km. The bottom of the basin, flat or slightly hilly, is usually called the abyssal (deep-water) plain. The leveled surface of the abyssal plains is due to the accumulation of sedimentary material brought from the land. The most extensive plains are located in the deep-sea areas of the ocean floor. In general, the abyssal plains occupy about 8% of the ocean floor.

mid-ocean ridges- the most tectonically active zones in which the neoformation of the earth's crust occurs. They are entirely composed of basalt rocks formed as a result of their entry along faults from the bowels of the Earth. This led to the peculiarity of the earth's crust, which makes up the mid-ocean ridges, and its separation into a special rift type.

ocean rises- large positive landforms of the ocean floor, not associated with mid-ocean ridges. They are located within the oceanic type of the earth's crust and are distinguished by large horizontal and significant vertical dimensions.

In the deep part of the ocean, a large number of isolated mountains were found that do not form any ridges. Their origin is volcanic. Seamounts, the tops of which are a flat platform, are called guyots.

Deep sea trenches (troughs)) - the zone of the greatest depths of the World Ocean, exceeding 6000 m. Their sides are very steep, and the bottom can be leveled if it is covered with precipitation. The deepest trenches are located in the Pacific Ocean.

The origin of the trenches is associated with the subsidence of lithospheric plates into the asthenosphere during the new formation of the seabed and the spreading of the plates. The gutters have significant horizontal dimensions. To date, 41 trenches have been discovered in the World Ocean (Pacific Ocean - 25, Atlantic - 7, Indian - 9).

Salinity. Ocean water consists by weight of 96.5% pure water and less than 4% dissolved salts, gases and suspended insoluble particles. The presence of a relatively small amount of various substances makes it significantly different from other natural waters.
In total, 44 chemical elements were found in the ocean water in a dissolved state. It is assumed that all naturally occurring substances are dissolved in it, but due to negligible amounts they cannot be detected. Distinguish between the main components of ocean water salinity (Cl, Na, Mg, Ca, K, etc.) and minor components contained in negligible amounts (among them gold, silver, copper, phosphorus, iodine, etc.).
A remarkable feature of the ocean water is the constancy of its salt composition. The reason for this may be the continuous mixing of the waters of the oceans. However, this explanation cannot be considered exhaustive.
The total amount of salts contained in the water of the World Ocean is 48 * 10 x 15 tons. This amount of salts is enough to cover the entire surface of the Earth with a layer of 45 m, and the land surface with a layer of 153 m.
With a very low content of silver (0.3 mg in 1 m3), its total amount in the water of the Ocean is 20,000 times greater than the amount of silver mined by people over the entire historical period. Gold is contained in ocean water in the amount of 0.006 mg per 1 m3, while its total amount reaches 10 billion tons.
According to the composition of salts, ocean water differs significantly from river water (Table 19).

In ocean water, most of all (27 g in 1 liter of water) ordinary table salt (NaCl), so the water of the Ocean tastes salty; magnesium salts (MgCl2, MgSO4) give it a bitter taste.
Significant differences in the ratio of salts in the water of the Ocean and in the water of rivers cannot but seem surprising, since rivers continuously carry salt into the Ocean.
It is assumed that the salt composition of the ocean waters released from the earth's interior is associated with their origin. Ocean waters stood out already with the initial salinity. In the future, a certain salt composition was balanced. The amount of salt carried by the rivers is to some extent balanced by their consumption. In the consumption of salts, the formation of iron-manganese nodules, the removal of salts by the wind, and, of course, the activity of organisms that extract salts (primarily calcium salts) from the water of the Ocean to build skeletons and shells are important. Skeletons and shells of dead organisms partially dissolve in water, and partially form bottom sediments and thus fall out of the cycle of matter.
Plants and animals that live in the Ocean absorb and concentrate in their bodies various substances found in the water, including those that man has not yet been able to detect. Calcium and silicon are especially vigorously absorbed. Algae annually fix billions of tons of carbon and release billions of tons of oxygen. Water passes through the gills of fish during breathing, many animals, filtering food, pass a large amount of water through the gastrointestinal tract, all animals swallow water with food. Ocean water somehow passes through the body of animals and plants, and this ultimately determines its modern salt composition.
Ocean waters have an average salinity of 35‰ (35 g of salts per 1 liter of water). Changes in salinity are caused by changes in the balance of salts or fresh water.
Salts enter the Ocean along with water flowing from the land, are brought in and carried away during water exchange with neighboring parts of the Ocean, are released or spent as a result of various processes occurring in the water. The constant supply of salts from land to the Ocean should have caused a gradual increase in the salinity of its waters. If this is indeed happening, it is so slowly that it remains undiscovered to this day.
The main reason for the differences in the salinity of the ocean water is the change in the balance of fresh water. Precipitation on the surface of the Ocean, runoff from land, melting ice cause a decrease in salinity; evaporation, ice formation, on the contrary, increase it. The influx of water from the land noticeably affects the salinity near the coast and especially near the confluence of rivers.
Since salinity on the surface of the Ocean in its open part depends mainly on the ratio of precipitation and evaporation (i.e., on climatic conditions), latitudinal zonality is found in its distribution. This is clearly visible on the map. isohaline- lines connecting points with the same salinity. In the equatorial latitudes, the surface layers of water are somewhat freshened (34-35‰) due to the fact that precipitation is greater than evaporation. In subtropical and tropical latitudes, the salinity of the surface layers is increased and reaches a maximum for the surface of the open Ocean (36-37‰. This is due to the fact that the consumption of water for evaporation is not covered by precipitation. The ocean loses moisture, while salts remain. To the north and south of the tropical latitudes, the salinity of ocean waters gradually decreases to 33-32‰, which is determined by a decrease in evaporation and an increase in precipitation. Melting floating ice contributes to a decrease in salinity on the surface of the Ocean. Currents violate the latitudinal zonality in the distribution of salinity on the surface of the Ocean. Warm currents increase salinity, cold ones, on the contrary , lower it.
The average salinity on the surface of the oceans is different. The Atlantic Ocean has the highest average salinity (35.4‰), the Arctic Ocean has the lowest (32‰). The increased salinity of the Atlantic Ocean is explained by the influence of the continents with its comparative narrowness. In the Arctic Ocean, Siberian rivers have a freshening effect (off the coast of Asia, salinity drops to 20‰).
Since changes in salinity are mainly related to the balance of water inflow and outflow, they are well expressed only in the surface layers, which directly receive (precipitation) and release water (evaporation), as well as in the mixing layer. Mixing covers the water column with a thickness of up to 1500 m. Deeper, the salinity of the waters of the World Ocean remains unchanged (34.7-34.9‰). The nature of the change in salinity depends on the conditions that determine salinity on the surface. There are four types of vertical salinity changes in the Ocean: I - equatorial, II - subtropical, III - moderate and IV - polar,
I. In equatorial latitudes, where water on the surface is freshened, salinity gradually increases, reaching a maximum at a depth of 100 m, where more saline waters come to the equator from the tropical part of the Ocean. Below 100 m salinity decreases, and from a depth of 1000-1500 m it becomes almost constant. II. In subtropical latitudes, salinity rapidly decreases to a depth of 1000 m; deeper it is constant. III. In temperate latitudes, salinity changes little with depth. IV. In the polar latitudes, the salinity on the surface of the Ocean is the lowest; with depth, it first increases rapidly, and then, from a depth of about 200 m, almost does not change.
The salinity of water on the surface of the seas can be very different from the salinity of water in the open part of the Ocean. It is also determined primarily by the balance of fresh water, and therefore depends on climatic conditions. The sea is influenced by the land washed by it to a much greater extent than the ocean. The deeper the sea goes into the land, the less it is connected with the ocean, the more its salinity differs from the average oceanic salinity.
Seas in polar and temperate latitudes have a positive water balance, and therefore the salinity on their surface is lower, especially at the confluence of rivers. Seas in subtropical and tropical latitudes, surrounded by land with a small number of rivers, have increased salinity. The high salinity of the Red Sea (up to 42‰) is explained by its position among the land, in a dry and hot climate. Precipitation on the sea surface is only 100 mm per year, there is no land runoff, and evaporation reaches 3000 mm per year. Water exchange with the Ocean occurs through the narrow Bab-el-Mandeb Strait.
The increased salinity of the Mediterranean Sea (up to 39‰) is the result of the fact that land runoff and precipitation do not compensate for evaporation, water exchange with the Ocean is difficult. In the Black Sea (18‰), on the contrary, evaporation is almost compensated by runoff (the annual runoff layer is 80 cm), and precipitation makes the water balance positive. The lack of free water exchange with the Sea of ​​Marmara contributes to the conservation of low salinity in the Black Sea.
In the North Sea, which, on the one hand, is influenced by the Ocean, and, on the other hand, by the strongly desalinated Baltic Sea, salinity increases from southeast to northwest from 31 to 35‰. All the margins of the sea, closely connected with the Ocean, have a salinity close to that of the adjacent part of the Ocean. In the coastal parts of the seas that receive rivers, the water becomes very fresh and often has a salinity of only a few ppm.
The change in salinity with depth in the seas depends on salinity at the surface and the associated water exchange with the Ocean (or with a neighboring sea).
If the salinity of the sea is less than the salinity of the Ocean (neighboring sea) at the strait connecting them, denser ocean water penetrates through the strait into the sea and sinks, filling its depths. In this case, the salinity in the sea increases with depth. If the sea is saltier than the neighboring part of the Ocean (sea), the water in the strait moves along the bottom towards the Ocean, along the surface - towards the sea. The surface layers acquire the salinity and temperature characteristic of the sea in given physical and geographical conditions. The salinity of the bottom waters corresponds to the salinity on the surface during the period of the lowest temperatures.
Various cases of changes in salinity with depth are clearly seen in the example of the Mediterranean, Marmara and Black seas. The Mediterranean Sea is saltier than the Atlantic Ocean. In the Strait of Gibraltar (depth 360 m) there is a deep current from the sea to the Ocean. Mediterranean water descends from the threshold, creating at some depth in the Ocean near the threshold an area of ​​increased salinity. On the surface in the strait, ocean water flows into the sea. The salinity of the water at the bottom of the Mediterranean Sea throughout its entire length is 38.6‰, while on the surface it varies from 39.6‰ in the eastern part to 37‰ in the western part. Accordingly, in the eastern part, salinity decreases with depth, in the western part it increases.
The Sea of ​​Marmara is located between two seas, the more salty Mediterranean and the less salty Black. Salty Mediterranean water, penetrating through the Dardanelles, fills the depths of the sea, and therefore the salinity at the bottom is 38‰. The Black Sea water, moving along the surface, comes to the Sea of ​​Marmara through the Bosporus and freshens the water of the surface layers up to 25‰.
The Black Sea is heavily freshened. Therefore, water of Mediterranean origin penetrates from the Sea of ​​Marmara into the Black Sea along the bottom of the Bosphorus and, descending, fills its depths. The salinity of water in the Black Sea increases with depth from 17-16 to 22.3‰.
The water of the World Ocean contains colossal amounts of the most valuable chemical raw materials, the use of which is still very limited. About 5 million tons of common salt are annually extracted from the water of the oceans and seas, including more than 3 million tons in the countries of Southeast Asia. Potassium and magnesium salts are extracted from sea water. Bromine gas is obtained as a by-product from the extraction of common salt and magnesium.
To extract chemical elements contained in very small quantities from water, one can use the amazing ability of many inhabitants of the Ocean to absorb and concentrate certain elements in their bodies, for example, the concentration of iodine in a number of algae is thousands and hundreds of thousands of times higher than its concentration in the water of the Ocean. Mollusks absorb copper, aspidia - zinc, radiolarians - strontium, jellyfish - zinc, tin, lead. There is a lot of aluminum in fucus and kelp, and sulfur in sulfur bacteria. By selecting certain organisms and enhancing their ability to concentrate elements, it will be possible to create artificial mineral deposits.
Modern chemistry has received ion exchangers (exchange resins), which have the property of absorbing various substances from a solution and retaining various substances on their surface. A pinch of ion exchanger can desalinate a bucket of salt water, extract salt from it. The use of ion exchangers will make the richness of the salts of the Ocean more accessible for use by people.
Gases in ocean water. Gases are dissolved in ocean water. These are mainly oxygen, nitrogen, carbon dioxide, as well as hydrogen sulfide, ammonia, methane. Water dissolves the gases of the atmosphere in contact with it, gases are released during chemical and biological processes, are brought by land waters, and enter the ocean water during underwater eruptions. The redistribution of gases in water occurs when it is stirred. Due to the high dissolving power of water, the ocean has a great influence on the chemical composition of the atmosphere.
Nitrogen is present everywhere in the Ocean, and its content almost does not change, since it does not enter into combinations well and is consumed little. Some infiltrating bacteria convert it into nitrates and ammonia.
Oxygen enters the ocean from the atmosphere and is released during photosynthesis. It is consumed in the process of respiration, for the oxidation of various substances, and is released into the atmosphere. The solubility of oxygen in water is determined by its temperature and salinity. When the surface of the Ocean is heated (spring, summer), water releases oxygen to the atmosphere; when it cools (autumn, winter), it absorbs it from the atmosphere. There is less oxygen in ocean water than in fresh water.
Since the intensity of photosynthesis processes depends on the degree of illumination of water by sunlight, the amount of oxygen in water fluctuates during the day, decreasing with depth. Below 200 m, there is very little light, there is no vegetation, and the oxygen content in the water drops, but then, at greater depths (>1800 m), it increases again as a result of the circulation of ocean waters.
The oxygen content in the surface layers of water (100-300 m) increases from the equator to the poles: at a latitude of 0 ° - 5 cm3 / l, at a latitude of 50 ° - 8 cm3 / l. The water of warm currents is poorer in oxygen than the water of cold currents.
The presence of oxygen in the water of the Ocean is a necessary condition for the development of life in it.
Carbon dioxide, unlike oxygen and nitrogen, is found in the water of the Ocean mainly in a bound state - in the form of carbon dioxide compounds (carbonates and bicarbonates). It enters the water from the atmosphere, is released during the respiration of organisms and during the decomposition of organic matter, and comes from the earth's crust during underwater eruptions. Like oxygen, carbon dioxide is more soluble in cold water. When the temperature rises, water releases carbon dioxide to the atmosphere, and when the temperature drops, it absorbs it. Much of the carbon dioxide in the atmosphere dissolves in ocean water. The reserves of carbon dioxide in the ocean are 45-50 cm3 per 1 liter of water. A sufficient amount of it is a prerequisite for the vital activity of organisms.
In the water of the seas, the amount and distribution of gases can be significantly different than in the water of the oceans. In the seas, the depths of which are not supplied with oxygen, hydrogen sulfide accumulates. This occurs as a result of the activity of bacteria that use the oxygen of sulfates to oxidize nutrients under anaerobic conditions. Normal organic life does not develop in a hydrogen sulfide environment.
An example of a sea whose depths are contaminated with hydrogen sulfide is the Black Sea. An increase in water density with depth ensures the balance of the water mass in the Black Sea. Complete mixing of water does not occur in it, oxygen gradually disappears with depth, the content of hydrogen sulfide increases, reaching 6.5 cm3 at the bottom per 1 liter of water.
Inorganic and organic compounds containing elements necessary for organisms are called nutrient.
The distribution of nutrients and energy (solar radiation) in the Ocean determines the distribution and productivity of living matter.
Ocean water density with an increase in salinity, it always increases, since the content of substances that have a greater specific gravity than water increases. Cooling, evaporation and ice formation contribute to the increase in density on the surface of the Ocean. As the density of water increases, convection occurs. When heated, as well as when salt water is mixed with precipitation water and with melt water, its density decreases.
On the surface of the Ocean, there is a change in density ranging from 0.996 to 1.083. In the open ocean, density is usually determined by temperature and therefore increases from the equator to the poles. The density of water in the ocean increases with depth.
Pressure. For every square centimeter of the ocean's surface, the atmosphere presses with a force of approximately 1 kg (one atmosphere). The same pressure on the same area is exerted by a column of water only 10.06 m high. Thus, we can assume that for every 10 m of depth, the pressure increases by 1 atmosphere. If we take into account that water compresses and becomes denser with depth, it turns out that the pressure at a depth of 10,000 m is 1119 atmospheres. All processes occurring at great depths are carried out under strong pressure, but this does not prevent the development of life in the depths of the Ocean.
Transparency of ocean water. The radiant energy of the Sun, penetrating into the water column, is scattered and absorbed. The transparency of water depends on the degree of its dispersion and absorption. Since the amount of impurities contained in water is not the same everywhere and changes with time, transparency also does not remain constant (Table 20). The least transparency is observed near the coast in shallow water, especially after storms. The transparency of water significantly decreases during the period of mass development of plankton. The decrease in transparency is caused by the melting of ice (ice always contains impurities, in addition, the mass of air bubbles enclosed in ice passes into water). It is noted that the transparency of water increases in places where deep waters rise to the surface.

Currently, transparency measurements at different depths are made using a universal hydrophotometer.
The color of the water of the oceans and seas. The thickness of the pure water of the Ocean (sea) as a result of the collective absorption and scattering of light has a blue or blue color. This color of water is called the "color of the sea desert." The presence of plankton and inorganic suspensions is reflected in the color of the water, and. it takes on a greenish tint. Large amounts of impurities make the water yellowish green, near the mouth of the rivers it can even be brownish.
To determine the color of the ocean water, the sea color scale (Forel-Ule scale) is used, which includes 21 test tubes with a liquid of different colors - from blue to brown.
In the equatorial and tropical latitudes, the dominant color of the ocean water is dark blue and even blue. For example, the Bay of Bengal, the Arabian Sea, the southern part of the China Sea, and the Red Sea have such water. Blue water in the Mediterranean Sea, the water of the Black Sea is close to it in color. In temperate latitudes, in many places the water is greenish (especially near the coast), it becomes noticeably greener in areas of ice melting. In the polar latitudes, a greenish color predominates.

mid-ocean ridges

They cross all the oceans, forming a single planetary system with a total length of over 60 thousand km, and their total area is 15,2 % area of ​​the oceans. The mid-ocean ridges do indeed occupy a median position in the Atlantic and Indian Oceans; in the Pacific Ocean they are shifted to the east towards the shores of America.

The relief of the mid-ocean ridges is sharply dissected, and as they move away from the axis, the mountain spiers are replaced by zones of hilly relief and become even more flattened in the area of ​​​​junction with deep-water plains. The ridges consist of mountain systems and valley-like depressions separating them, elongated in accordance with the general strike. The height of individual mountain peaks reaches 3-4 km, the total width of the mid-ocean ridges ranges from 400 to 2000 km. Along the axial part of the ridge, there is a longitudinal depression called a rift or rift valley (rift from the English gap). Its width is from 10 to 40 km, and the relative depth is from 1 to 4 km. The steepness of the slopes of the valley is 10-40°.

The walls of the valley are divided by steps into several ledges. The rift valley is the youngest and tectonically the most active part of the mid-ocean ridges; it has an intense block-ridge subdivision. Its central part consists of frozen basalt domes and sleeve-like streams dissected gyarami- gaping tensile cracks without vertical displacement, from 0.5 to 3 m wide (sometimes 20 m) and tens of meters long.

Mid-ocean ridges are broken by transform faults, breaking their continuity in the latitudinal direction. The amplitude of the horizontal displacement is hundreds of km (up to 750 km in the equatorial zone of the Mid-Atlantic Ridge), and the vertical displacement is up to 3-5 km.

Sometimes there are small forms of bottom topography called microrelief, among which erosive, biogenic and chemogenic are distinguished.

Water is a polymer compound of H 2 O molecules, unlike water vapor. Various O and H isotopes can participate in the structure of a water molecule. The most common are 1 H - light hydrogen, 2 H - deuterium (150 mg⁄ l.), 16 O, 17 O, 18 O. The bulk of the molecules are pure water 1 H 2 16 O, a mixture of all other types of water is called heavy water, which differs from pure water in greater density. In practice, heavy water is understood to be deuterium oxide 2 H 2 16 O (D 2 O), and superheavy water is tritium oxide 3 H 2 16 O (T 2 O). The last in the oceans contains a negligible amount - 800 grams (in terms of tritium). The main physical properties of water include optical, acoustic, electrical and radioactivity.

Optical properties

Usually they understand the penetration of light into water, its absorption and scattering in water, the transparency of sea water, its color.

The surface of the sea is illuminated directly by the sun's rays (direct radiation) and by light scattered by the atmosphere and clouds (diffuse radiation). One part of the sun's rays is reflected from the sea surface into the atmosphere, the other part penetrates into the water after refraction on the surface of the waters.

Sea water is a translucent medium, so light does not penetrate to great depths, but is scattered and absorbed. The light attenuation process is selective. The components of white light (red, orange, green, cyan, indigo, violet) are absorbed and scattered by sea water in different ways. As it penetrates into the water, red and orange first disappear (at a depth of approximately 50 m), then yellow and green (up to 150 m), and then blue, blue and purple (up to 400 m).

Transparency is traditionally understood as the depth of immersion of a white disk with a diameter of 30 cm, at which it ceases to be visible. Transparency must be measured under certain conditions, since its value depends on the observation height, time of day, cloud cover and sea waves. The most accurate measurements were taken in calm, clear weather around noon, from a height of 3-7 m above the water surface.

The combination of absorption and scattering of light determines the blue color of pure (without impurities) sea water. The color of the sea surface depends on a number of external conditions: the angle of view, the color of the sky, the presence of clouds, wind waves, etc. So, when waves appear, the sea quickly turns blue, and when dense clouds, it darkens.

As you approach the coast, the transparency of the sea decreases, the water turns green, sometimes it acquires yellowish and brown hues. In the open sea, transparency and color are determined by suspended particles of organic origin, plankton. During the period of phytoplankton development (spring, autumn), the transparency of the sea decreases, and the color becomes more green. In the central parts, the transparency usually exceeds 20 m, and the color is in the range of blue tones. The highest transparency (65.5 m) was recorded in the Sargasso Sea. In temperate and polar latitudes, rich in plankton, water transparency is 15-20 m, and the color of the sea is greenish-blue. At the confluence of large rivers, the color of sea water is cloudy and brownish-yellow, the transparency decreases to 4 m. The color of the sea changes sharply under the influence of plant or animal organisms. A mass accumulation of any one organism can color the surface of the sea in yellow, pink, milky, red, brown and green. This phenomenon is called the bloom of the sea. In some cases, the glow of the sea occurs at night, associated with the study of biological light by marine organisms.

Acoustic properties

Determine the possibility of sound propagation in sea water - wave-like oscillatory movements of particles of an elastic medium, which is sea water. The strength of the sound is proportional to the square of the frequency, which is determined by the number of elastic vibrations per second. Therefore, from a source of the same power, you can get a sound of greater strength by increasing the frequency of sound vibrations. For practical purposes in maritime affairs (echo sounding, underwater communications), ultrasound (high frequency sound) is used, which is also characterized by a weakly divergent beam of acoustic rays.

The speed of sound in sea water depends on the density and specific volume of the water. The first characteristic, in turn, depends on salinity, temperature and pressure. The speed of sound in sea water ranges from 1400 to 1550 m/s, which is 4-5 times the speed of sound in air. The propagation of sound in water is accompanied by its attenuation due to absorption and scattering, as well as refraction and reflection of sound waves.

At some depth in the ocean water there is a zone where the speed of sound is minimal, sound rays, undergoing multiple internal reflections, propagate in this zone over ultra-long distances. This layer with the minimum speed of sound propagation is called the sound channel. The sound channel is characterized by the property of continuity. If the sound source is placed near the axis of the channel, then the sound propagates over a distance of thousands of kilometers (the maximum recorded distance is 19,200 km). In the world ocean, the sound channel is located on average at a depth of 1 km. The polar seas are characterized by the effect of the near-surface location of the sound channel (depths of 50-100 m), as a result of sound reflection from the sea surface.

After the sound source is turned off, a residual sound, called reverberation, remains in the water column for some time. This is a consequence of the reflection and scattering of sound waves. Distinguish bottom, surface and volume reverberation, in the latter case, sound dispersion occurs with the help of gas bubbles, plankton, suspension.

Electrical Properties

Pure (fresh) water is a poor conductor of electricity. Sea water, being an almost completely ionized solution, conducts electricity well. The electrical conductivity depends on the salinity and temperature of the water, the higher the salinity and temperature, the higher the electrical conductivity. Moreover, salinity affects the electrical conductivity to a greater extent. For example, in the temperature range from 0 to 25°C, the electrical conductivity increases only two times, while in the salinity range from 10 to 40‰, it increases by 3.5 times.

In the thickness of sea water there are telluric currents caused by the corpuscular radiation of the sun. Since the electrical conductivity of sea water is better than that of a solid shell, the magnitude of these currents in the ocean is higher than in the lithosphere. It increases slightly with depth. When sea water moves, an electromotive force is induced in it, which is proportional to the magnetic field strength and the speed of sea water (conductor) movement. By measuring the induced electromotive force and knowing the strength of the magnetic field in a given place and at a given moment, it is possible to determine the speed of sea currents.

radioactive properties

Sea water is radioactive because radioactive elements are also dissolved in it. The main role belongs to the radioactive isotope 40 K and, to a much lesser extent, to the radioactive isotopes Th, Rb, C, U, and Ra. The natural radioactivity of sea water is 180 times less than the radioactivity of granite and 40 times less than the radioactivity of sedimentary rocks of the continents.

In addition to the considered physical properties, sea water has the properties of diffusion, osmosis and surface tension.

Molecular diffusion is expressed in the movement of particles of a substance dissolved in water without mechanical mixing.

The phenomenon of osmosis, i.e. diffusion of dissolved substances through a porous partition (membrane), is mainly of biological importance, but can also be used to obtain clean water from sea water.

Surface tension is the property of water to have a thin transparent film on the surface that tends to shrink. This phenomenon is of decisive importance in the formation of capillary waves on the sea surface.

The chemical composition of ocean waters

Sea water differs from the water of rivers and lakes by its bitter-salty taste and high density, which is explained by the minerals dissolved in it. Their number, expressed in grams per kilogram of sea water, is called salinity (S) and is expressed in ppm (‰). The total salinity is 35‰ or 35% or 35 g per 1 kg of water. Such salinity of sea water is called normal and is typical for the entire mass of water, with the exception of the surface layer of 100-200 m, where salinity ranges from 32 to 37‰, which is associated with climatic zoning. In arid zones, where evaporation is high and surface runoff is low, salinity increases. In humid zones, salinity decreases due to the desalination effect of surface water runoff from the continent. The climate is stronger in inland seas. In the Red Sea, salinity reaches 41-43‰. Particularly high salinity (200-300‰) is observed in the lagoons of arid regions laced from the sea (Kora-Bogaz-Gol). The salinity of the Dead Sea is 260-270‰.

Elemental composition Salt elemental composition

sea ​​water sea water

O 85.8% Cl 55.3%

H 10.7% Na 30.6%

Cl 2.1% SO 4 7.7%

Na 1.15% Mg 3.7%

Mg 0.14% Ca 1.2%

S 0.09% K 1.1%

Ca 0.05% Br 0.2%

K 0.04% CO2 0.2%

The rest is less than 0.001%.

The salt composition of sea water is dominated by:

Chlorides 89.1% (NaCl -77.8% - halite, MgCl 2 - 9.3% - bischofite, KCl - 2% - sylvite);

Sulfates 10.1% (Mg SO 4 - 6.6% - epsomite, CaSO 4 - 3.5% - anhydrite)

Carbonates 0.56%

Bromates 0.3%.

Gas composition of sea water

Dissolved in water: oxygen, carbon dioxide, nitrogen, hydrogen sulfide in some places.

Oxygen enters the water in two ways:

From the atmosphere

Due to the photosynthesis of phytoplankton (green plants)

6 CO 2 + 6H 2 O \u003d C 6 H 12 O 6 + 6O 2 + 674 kcal (light + chlorophyll).

Its content varies greatly from 5 to 8 cm 3 per liter and depends on temperature, salinity and pressure. The solubility of oxygen greatly decreases with increasing temperature, so it is abundant in high latitudes. Seasonal fluctuations take place, with an increase in temperature, oxygen is released into the atmosphere and vice versa, this is how the dynamic interaction of the atmosphere and the hydrosphere is carried out. The same inverse relationship exists between oxygen content and salinity: the greater the salinity, the less oxygen. The dependence of the oxygen content on pressure is direct: the greater the pressure, the more oxygen is dissolved in water. The largest amount of oxygen is contained on the surface of the water (due to the atmosphere and photosynthesis) and at the bottom (due to pressure and lower consumption by organisms) up to 8 cm 3 per liter - these two films merge in the coastal zone. In the middle part of the reservoir, the oxygen content is the lowest - 2-3 cm 3 per liter. Due to the vertical and horizontal circulation of waters, the oceans contain free oxygen almost everywhere. Oxygen is used for the respiration of plants and animals and the oxidation of minerals.

Carbon dioxide found in water 1) partially in a free dissolved state and 2) in a chemically bound form as part of carbonates and bicarbonates. The total content of CO 2 in water is more than 45 cm 3 per liter, of which only half falls to the share of free CO 2. Sources of carbon dioxide: atmosphere, volcanic gases, organics and river waters. Consumption: photosynthesis, formation of carbonate minerals. The content of CO 2 is also regulated by temperature; in the upper heated layers of sea water, the solubility of CO 2 drops and it is released into the atmosphere. Its shortage is created, which leads to the formation of insoluble calcium carbonate CaCO 3, which precipitates. In cold waters, a high content of CO 2 is noted.

Nitrogen contained in water in the amount of 13 cm 3 per liter and comes mainly from the atmosphere.

hydrogen sulfide It is distributed to a limited extent and confined to closed basin seas that communicate with the World Ocean through narrow shallow straits. This disrupts the water exchange between them. For example, in the Black Sea, hydrogen sulfide contamination starts approximately from a depth of 150 m and increases with depth, and in the near-bottom part it reaches 5-6 cm 3 /liter. Hydrogen sulfide is produced by bacteria from sulfates:

CaSO 4 + CH 4 → H 2 S + CaCO 3 + H 2 O

In addition, a certain amount of organic matter is dissolved in the waters of the World Ocean (up to 10 g/l in the Sea of ​​Azov), there is also a certain amount of turbidity and suspension.

The temperature of the waters of the oceans

The main source of heat received by the World Ocean is the Sun. Heat comes from it in the form of short-wave solar radiation, consisting of direct radiation and radiation scattered by the atmosphere. Some of the radiation is reflected back into the atmosphere (reflected radiation). The World Ocean receives additional heat as a result of condensation of water vapor on the surface of the sea and due to the heat flow coming from the bowels of the Earth. At the same time, the ocean loses heat through evaporation, effective radiation, and water exchange. The algebraic sum of the amount of heat entering the water and lost by the water as a result of all thermal processes is called the heat balance of the sea. Since the average water temperature of the World Ocean over the long-term observation period remains unchanged, then all heat fluxes in the sum are equal to zero.

The distribution of temperature over the surface of the World Ocean depends mainly on the latitude of the area, so the highest temperatures are located in the equatorial zone (thermal equator). The distorting influence is exerted by the continents, the prevailing winds, currents. Long-term observations show that the average surface water temperature is 17.54 o C. The warmest is the Pacific Ocean (19.37 o), the coldest is the Arctic Ocean (-0.75 o). The temperature decreases with depth. In the open parts of the ocean, this occurs relatively quickly up to Ch. 300-500 m and much slower up to ch. 1200-1500 m; below 1500 m the temperature decreases very slowly. In the bottom layers of the ocean at depths below 3 km, the temperature is mainly +2 o C and 0 o C, reaching -1 o C in the Arctic Ocean. In some deep-water basins with Ch. 3.5 - 4 km and to the bottom, the water temperature rises slightly (for example, the Philippine Sea). As an anomalous phenomenon, a significant increase in the temperature of the bottom layer of water up to 62 ° C in some depressions of the Red Sea should be considered. Such deviations from the general pattern are a consequence of the influence of deep processes occurring in the earth's interior.

The upper layer of water (on average up to 20 m) is subject to daily temperature fluctuations, it is distinguished as an active layer. The transition from the active layer to the lower layer of low temperatures occurs in a relatively thin layer, which is called thermocline. The main characteristics of the thermocline are as follows:

Depth of occurrence - from 300-400 m (in the tropics) to 500-1000 m (in the subtropics),

Thickness - from a few cm to tens of meters,

Intensity (vertical gradient) -0.1-0.3 o per 1 m.

Sometimes two thermoclines are distinguished: seasonal and permanent. The first one is formed in spring and disappears in winter (its depth is 50-150 m). The second, called the "main thermocline", exists year-round and occurs at relatively great depths. Two types of thermocline are found in temperate climates.

The thermocline is also characterized by a change in the optical properties of water, which is used by fish running away from predators: they dive into the thermocline, and predators lose sight of them.

It has also been established that over the past 70 million years, the temperature of the deep waters of the World Ocean has decreased from 14 to 2 o C.

Density of sea water

The density of any substance is a quantity measured by the mass of the substance per unit volume. The unit of density is the density of distilled water at a temperature of 4 ° C and normal atmospheric pressure. The density of sea water is the mass of sea water (in g) contained in 1 cm3. It depends on salinity (direct relationship) and temperature (inverse relationship). The density of sea water at a temperature of 0 ° C and a salinity of 35‰ is 1.028126 g / cm 3.

The density is unevenly distributed over the surface: it is minimal in the equatorial zone (1.0210 g/cm3) and maximal in high latitudes (1.0275 g/cm3). With depth, the change in density depends on the change in temperature. Below 4 km, the density of sea water changes little and reaches 1.0284 g/cm 3 near the bottom.

sea ​​water pressure

The pressure in the seas and oceans increases by 1 MPa or 10 atm for every 100 m. Its value also depends on the density of water. You can calculate the pressure using the formula:

P \u003d H ּρ / 100,

P - pressure in MPa,

H is the depth for which the calculation is made,

ρ is the density of sea water.

Under the pressure of the overlying layers, the specific volume of sea water decreases, i.e. it is compressed, but this value is insignificant: at S \u003d 35‰ and t \u003d 15 ° C it is 0.0000442. However, if water were absolutely incompressible, then the volume of the World Ocean would increase by 11 million km 3, and its level would climb 30 meters.

In addition to the thermocline (temperature jump), there is also a pressure jump - pycnocline. Sometimes several pycnoclines are identified in the marine basin. For example, two pycnoclines are known in the Baltic Sea: in the depth range of 20-30 m and 65-100 m. The pycnocline is sometimes used as a “liquid soil”, allowing a neutrally balanced submarine to lie on it without working propellers.