1.1 Distribution of water and land on the globe.

The total surface of the earth is 510 million sq. km.

The land area is 149 million sq. km. (29%)

Occupied by water - 310 million sq. km. (71%)

In the Northern and Southern Hemispheres, the ratio of land surface and water is not the same:

In the Southern Hemisphere, water accounts for 81%

In the Northern Hemisphere, water occupies 61%

The continents are more or less separated from each other, while the waters of the ocean form a continuous body of water on the surface of the globe, which is called the World Ocean. According to physical and geographical features, the latter is divided into separate oceans, seas, bays, bays and straits.

Ocean - the largest part of the World Ocean, bounded on different sides by continents that are not connected to each other.

Since the 30s of the twentieth century, the division into 4 oceans has been accepted: Quiet, Indian, Atlantic, Arctic (formerly Southern Arctic).

The continents that divide the World Ocean define the natural boundaries between the oceans. In the high southern latitudes there are no such boundaries and they are accepted here conditionally: between the Pacific and Atlantic along the meridian of Cape Horn (6804 ‘W), from the island of Tierra del Fuego to Antarctica; between the Atlantic and Indian - from Cape Agulhas along the meridian 20E. ; between Indian and Pacific - from Cape South-East to the island. Tasmania along the meridian 14655’.

The areas of the oceans as a percentage of the total area of ​​the World Ocean are;

Quiet - 50%

Atlantic - 25.8%

Indian - 20.8%

Arctic - 3.6%

In each of the oceans, seas are distinguished and represent more or less isolated and fairly extensive areas of the ocean, which have their own hydrological regime, connecting under the influence of local conditions and difficult water exchange with adjacent areas of the ocean.

The seas, according to the degree of their isolation from the ocean and physical and geographical conditions, are divided into three main groups:

1.inland seas

A. middle seas

b. semi-closed

2. marginal seas

3. interisland seas

Mediterranean Seas surrounded on all sides by land and connected to the ocean by one or more straits. They are characterized by maximum isolation of natural conditions, closed circulation of surface waters and greatest independence in the distribution of salinity and temperature.

These seas include: Mediterranean, Black, White Seas.

Semi-enclosed seas partially limited by continents and separated from the ocean by peninsulas or a chain of islands, rapids in the straits between which complicate water exchange, but it is still carried out much more freely than in the Mediterranean seas.

Example: the Bering, Okhotsk, and Japanese seas, which are separated from the Pacific Ocean by the Aleutian, Kuril, and Japanese islands.

Rim Seas are more or less open parts of the ocean, separated from the ocean by peninsulas or islands.

Water exchange between seas of this type and the ocean is practically free. The formation of the current system and the distribution of salinity and temperature are equally influenced by both the continent and the ocean. The marginal seas include: the Arctic seas, except for the White Sea.

Interisland seas - these are parts of the ocean surrounded by a ring of islands, the rapids in the straits between which prevent any free exchange of water. As a result of the influence of the ocean, the natural conditions of these seas are similar to the natural conditions of the ocean. There is some independence in the nature of the currents and the distribution of temperature and salinity on the surface and at the depths of these seas. Seas of this type include the seas of the East Indian archipelago: Sulu, Celeba, Benda, Java, etc.

The smaller divisions of the ocean are bays, bays and straits. The difference between a bay and a bay is quite arbitrary.

Bay called the part of the sea that juts into the land and is sufficiently open to the influence of adjacent waters. The largest bays: Biscay, Guinea, Bengal, Alaska, Hudson, Anadyr, etc.

Bay called a small bay with the mouth of the bay itself, limited by islands or peninsulas, which somewhat complicate the water exchange between the bay and the adjacent body of water. Example Sevastopol, Zolotoy Rog, Tsemeskaya, etc.

In the north, the bays that protrude deeply into the land where rivers usually flow are called lips; at the bottom of the lips there are traces of river sediments, the water is highly desalinated.

The largest bays: Obskaya, Dvinskaya, Onega, etc. Winding, low, deeply protruding bays into the mainland, formed due to glacial erosion, are called fiords .

Liman called the mouth of a river valley, or ravine, flooded by the sea, as a result of a slight subsidence of the land. Lagoon called: a) a shallow body of water, separated from the sea as a result of sediment deposition in the form of a coastal bar and connected to the sea by a narrow strait; b) an area of ​​sea between the mainland and a coral reef or atoll.

Strait called a relatively narrow part of the World Ocean, connecting two bodies of water with fairly independent natural conditions.

1.2. Chemical composition and salinity of sea water

Sea water differs from fresh water in taste, specific gravity, transparency, color, and more aggressive effects. Due to the strong polarity and large dipole moment of the molecules, water has a high dissociating ability. Therefore, various salts are dissolved in ionic dispersed form, and sea water is essentially a weak, fully ionized solution with an alkaline reaction, which is determined by the excess of the sum of cation equivalents by an average of 2.38 mg-equiv/l (alkaline solution). Weight reduced to vacuum The amount expressed in grams dissolved in 1 kg of sea water, provided that all halogens are replaced by an equivalent amount of chlorine, all carbonates are converted into oxides, and organic matter is burned, is usually called the salinity of sea water. Salinity is indicated by the symbol S. A unit of salinity is taken to be 1 g of salts dissolved in 1000 g of sea water and called ppm , denoted by %0. The average amount of minerals dissolved in 1 kg of sea water is 35 g and, therefore, the average salinity of the world's oceans is S = 35%0.

Theoretically, sea water contains all known chemical elements, but their weight content is different. There are two groups of elements contained in sea water.

1 group. Major ions of ocean water.

Ions and molecules	Per 1 kg of water (S = 35%0)
Chloride Cl
Sulfated SO4
Hydrocarbonate HCO3
Bromide B2
Fluoride F
Boric acid H2 BO3
Sum of anions:
Sodium Na
Magnesium Mg
Calcium Ca
Strontium Sr
Sum of cations
Sum of ions

Group 2 - Microelements whose total content does not exceed 3 mg/kg.

Certain elements are present in seawater in vanishingly small quantities. Example: silver - 310 -7 g, gold - 510 -7 g. The main elements are found in salt compounds in sea water, the main ones being NaCl and MgCl, constituting 88.7% by weight of all solids dissolved in sea water ; sulfates MgSO4, CaSO4, K2SO4 making up 10.8% and carbonate CaCO3 making up 0.3%. As a result of the analysis of sea water samples, it was found that the content of dissolved minerals can vary widely (from 2 to 30 g/kg), but their percentage ratio can be assumed to be constant with sufficient accuracy for practical purposes. This pattern is called constancy of the salt composition of sea water .

Based on this pattern, it turned out to be possible to associate the salinity of sea water with the content of chlorine (as the element contained in the largest amount in sea water)

S = 0.030 + 1.805 Cl.

River water contains on average 60.1% carbonates and 5.2% chlorides. However, despite the fact that every year 1.6910 9 tons of carbonates (HCO3) enter the World Ocean with the water of rivers, the flow of which is 3.610 4 , their total content in the ocean remains practically unchanged. The reasons are:

Intensive consumption by marine organizations to build limestone formations.

Precipitation due to poor solubility.

It should be noted that it is almost impossible to detect changes in salt content because the total mass of water in the ocean is 5610 15 tons and the supply of salts turns out to be practically negligible. For example, it will take 210 5 years to change the content of chloride ions by 0.02%0.

Salinity on the surface of the ocean in its open parts depends on the relationship between the amount of precipitation and the amount of evaporation, and the fluctuation in salinity for these reasons is 0.2%0. The greater the difference in temperature between water and air, the wind speed and its duration, the greater the amount of evaporation. This leads to an increase in water salinity. Precipitation reduces surface salinity.

In the polar regions, salinity changes with melting and ice formation and fluctuations here are approximately 0.7%0.

The change in salinity across latitudes is approximately the same for all oceans. Salinity increases from the poles to the tropics, reaching 20-25°C. and Yu. or and decreases again at the equator. Distribution by latitude in the Atlantic Ocean of salinity, precipitation, evaporation, density, and water temperature. (Figure 1).

A uniform change in the salinity surface is obtained due to the presence of oceanic and coastal currents, as well as as a result of the removal of fresh water by large rivers.

The less the sea is connected to the ocean, the more different the salinity of the seas is from the salinity of the ocean.

Sea salinity:

Mediterranean 37-38%0 in the west

38-39%0 in the east

Red Sea 37%0 in the south

41%0 in the north

Persian Gulf 40%0 in the north

37-38%0in the east

In depth, fluctuations in salinity occur only at a depth of 1500 m. Below this horizon, salinity does not change significantly. The distribution of salinity in depth is affected by horizontal movements and vertical circulation of water masses. To map the distribution of salinity on the surface of the ocean or on any other horizon, salinity lines are drawn - isohalines .

1.3.

Gases in sea water

In contact with the atmosphere, sea water absorbs gases contained in it from the air: oxygen, nitrogen, carbon dioxide.

The amount of dissolved gases in seawater is determined by the partial pressure and solubility of the gases, which depends on the chemical nature of the gases and decreases with increasing temperature.

	Table of solubility of gases in fresh water at a partial pressure of 760 mmHg.
	Gas solubility (ml/l)			Oxygen	Carbon dioxide

Hydrogen sulfide

The solubility of oxygen and nitrogen that do not react with seawater also depends on salinity and decreases with its increase. The content of soluble gases in seawater is estimated in absolute units (ml/l) or as a percentage of the saturated amount, i.e. on the amount of gases that can dissolve in water at a given temperature and salinity, normal humidity and pressure of 760 mmHg. Oxygen and nitrogen, due to the better solubility of oxygen in sea water, are in a 1:2 ratio. The oxygen content fluctuates in time and space from significant supersaturation (up to 350% then in shallow water as a result of photosynthesis, to its complete disappearance when consumed by the respiration of organisms and oxidation and in the absence of vertical circulation.

Since the solubility of oxygen largely depends on temperature, in the cold season oxygen is absorbed by sea water, and with increasing temperature, excess oxygen passes into the atmosphere.

Carbon dioxide is contained in the air in an amount of 0.03% and therefore its content in water should be achieved at 0.5 ml/l. However, unlike oxygen and nitrogen, carbon dioxide not only dissolves in water, but also partially enters into compounds with bases (since water has a slightly alkaline reaction). As a result, the total content of free and bound carbon dioxide can reach 50 ml/l. Carbon dioxide is consumed during photosynthesis and for the construction of calcareous formations by organisms. A small part of carbon dioxide (1%) combines with water to form carbonic acid

CO2 + H2O  H2CO3.

H2CO3  H + HCO3

H2CO3  H + CO3

A normal solution of hydrogen ions contains 1 g
in 1 liter of water. Experiments have established that at a H ion concentration of 110 -7 g/l, water is neutral. It is convenient to express the concentration of hydrogen ions by an exponent with the opposite sign and denote pH.

For neutral water pH = 7

If hydrogen ions predominate pH< 7 (кислая реакция).

If hydroxyl ions predominate pH > 7 (alkaline reaction).

It has been established that with a decrease in the content of free carbon dioxide, the pH increases. In the open ocean, water has a slightly alkaline reaction or pH = 7.8 - 8.8.

1.4. Temperature and thermal properties of sea water

The ocean surface is heated directly and by diffuse solar radiation.

In the absence of continents, the temperature on the surface of the ocean would depend only on the latitude of the place. In fact, with the exception of the southern part of the World Ocean, the map is completely different due to the dismemberment of the ocean, the influence of oceanic plants and vertical circulation.

Average gas temperatures on the surface of the oceans:

Atlantic - 16.9 С

Indian - 17.0 С

Quiet 19.1 С

Global - 17.4С

Average air temperature 14.3 С

The highest is in the Persian Gulf (35.6 С). The lowest is in the Arctic Ocean (-2 С). Temperature decreases with depth to horizons of 3000 - 500 m very quickly, then to 1200 - 1500 m much more slowly, and from 1500 m to the bottom either very slowly or does not change at all. (Figure 2)

Fig.2. Temperature changes with depth at different latitudes.

Daily temperature fluctuations quickly decrease with depth and die out at a horizon of 30-50 m. The maximum temperature at depth occurs 5-6 hours later than at the surface. The depth of penetration of gas temperature fluctuations depends on environmental conditions, but usually does not exceed 300 - 500 m. The specific heat capacity is very high:

1 Cal/g * deg = 4186.8 J/kg * deg.

Substance	Heat capacity Cal/G*deg
Fresh water
Sea water
Liquid ammonia

When 1 cubic cm of water is cooled by 1°C, an amount of heat is released sufficient to heat about 3000 cubic meters per 1 m. cm air.

The thermal conductivity of sea water is determined by the coefficient of molecular thermal conductivity, which varies depending on temperature, salinity, pressure within the range (1.3 - 1.4) 10 -3 Cal / cm  degsec.

Heat transfer in this way occurs extremely slowly. In real conditions, there is always turbulent fluid movement, and heat transfer in the ocean is always determined by the coefficient of turbulent thermal conductivity.

1.5. Density, specific gravity and compressibility of sea water

The density of sea water is the ratio of a unit weight of a volume of water at the temperature at the time of observation to the weight of a unit volume of distilled water at a temperature of 4  C ( ).

It is known from physics that density is defined as mass enclosed in units of volume (g/cm ; kg/m ).

Since the density and specific gravity of distilled water at 4 °C is taken = 1, then the numerical density ( ) and physical density are equal.

In oceanography, density is not measured but calculated through specific gravity, with 2 forms of specific gravity used for intermediate calculations:

The following concepts are derived:

Conditional density

Conditional specific gravity at 17.5  WITH

Conditional specific gravity at 0  C (standard conventional weight of sea water)

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 the established classification, four separate oceans have been 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 a maximum depth of $106$ 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 waters of the marginal seas are practically no different in physical and chemical composition from the open waters of the 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 of the 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 physicochemical, ecological and biological processes constantly occur in seawater, which have a direct impact on changes in the overall composition of the 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 of solids in water and, as a result, changing the ratio 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 substance dissolved 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 of 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 of 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.

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 World Ocean. Mid-ocean ridges actually occupy a middle position in the Atlantic and Indian Oceans; in the Pacific Ocean they are shifted east to the shores of America.

The relief of the mid-ocean ridges is sharply dissected, and as they move away from the axis, mountain spiers give way to zones of hilly relief and flatten even more in the area of ​​\u200b\u200bthe junction with deep-sea plains. The ridges consist of mountain systems and valley-shaped depressions separating them, elongated in accordance with the general strike. The height of individual mountain peaks reaches 3-4 km, the total width of mid-ocean ridges ranges from 400 to 2000 km. Along the axial part of the ridge, a longitudinal depression can be traced, called a rift or rift valley (rift from the English gap). Its width is from 10 to 40 km, and its relative depth is from 1 to 4 km. The steepness of the valley slopes is 10-40°.

The walls of the valley are divided by steps into several ledges. The rift valley is the youngest and tectonically most active part of the mid-ocean ridges; it has an intense block-ridge dissection. Its central part consists of frozen basalt domes and arm-shaped flows, dissected gyarami– gaping tensile cracks without vertical displacement, 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 relief called microrelief, among which erosional, biogenic and chemogenic are distinguished.

Water is a polymer compound of H 2 O molecules, unlike water vapor. Various isotopes of O and H 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 mass is formed by molecules of pure water 1 H 2 16 O, the mixture of all other types of water is called heavy water, which differs from pure water in being more dense. In practice, heavy water is understood as deuterium oxide 2 H 2 16 O (D 2 O), and superheavy water is understood as tritium oxide 3 H 2 16 O (T 2 O). The world's oceans contain a negligible amount of the latter - 800 grams (in terms of tritium). The main physical properties of water include optical, acoustic, electrical and radioactivity.

Optical properties

Usually they mean 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 penetrates into the water after refraction on the surface of the water.

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

Transparency is traditionally understood as the depth at which a white disk with a diameter of 30 cm is immersed, at which it ceases to be visible. Transparency must be measured under certain conditions, since its value depends on the observation altitude, time of day, cloud cover and sea conditions. The most accurate measurements are those 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 causes the blue color of pure (without impurities) sea water. The color of the sea surface depends on a number of external conditions: viewing angle, sky color, presence of clouds, wind waves, etc. So, when waves appear, the sea quickly turns blue, and when there are dense clouds, it darkens.

As you approach the shores, the transparency of the sea decreases, the water turns green, sometimes acquiring yellowish and brown shades. 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 greener. In the central parts, transparency usually exceeds 20 m, and the color is within 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, transparency decreases to 4 m. The color of the sea changes sharply under the influence of plant or animal organisms. A massive accumulation of any one organism can color the surface of the sea yellow, pink, milky, red, brown and green. This phenomenon is called sea bloom. In some cases, sea glow 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 propagating oscillatory movements of particles of an elastic medium, which is sea water. The strength of 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 it is possible to obtain 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 diverging beam of acoustic rays.

The speed of sound in sea water depends on the density and specific volume of 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 dispersion, as well as refraction and reflection of sound waves.

At a certain 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 very 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 a sound source is placed near the axis of the channel, then the sound travels over a distance of thousands of kilometers (the maximum recorded distance is 19,200 km). In the world's oceans, the sound channel is located on average at a depth of 1 km. The polar seas are characterized by the effect of a near-surface location of the sound channel (depth 50-100 m), as a result of the reflection of sound from the surface of the sea.

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

Electrical properties

Pure (fresh) water is a poor conductor of electricity. Sea water, being an almost completely ionized solution, conducts electricity well. 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 electrical conductivity to a greater extent. For example, in the temperature range from 0 to 25°C, electrical conductivity increases only twofold, 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 corpuscular radiation from the sun. Since the electrical conductivity of seawater is better than that of the solid shell, the magnitude of these currents in the ocean is higher than in the lithosphere. It increases somewhat with depth. When sea water moves, an electromotive force is induced in it, proportional to the magnetic field strength and the speed of movement of the sea water (conductor). By measuring the induced electromotive force and knowing the magnetic field strength 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 physical properties discussed, 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), has mainly biological significance, 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 contract. This phenomenon is crucial in the formation of capillary waves on the sea surface.

Chemical composition of ocean waters

Sea water differs from the water of rivers and lakes in its bitter-salty taste and high density, which is explained by the minerals dissolved in it. Their quantity, 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. This salinity of sea water is called normal and is characteristic of 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 zonation. 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 has a stronger effect in inland seas. In the Red Sea, salinity reaches 41-43‰. Particularly high salinity (200-300‰) is observed in lagoons of arid regions isolated 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% CO 2 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% (MgSO 4 - 6.6% - epsomite, CaSO 4 - 3.5% - anhydrite)

Carbonates 0.56%

Bromates 0.3%.

Gas composition of sea water

Dissolved in water are: oxygen, carbon dioxide, nitrogen, and sometimes hydrogen sulfide.

Oxygen enters the water in two ways:

From the atmosphere

Through photosynthesis of phytoplankton (green plants)

6 CO 2 + 6H 2 O = 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 decreases greatly with increasing temperature, which is why it is abundant at high latitudes. There are seasonal fluctuations; when the temperature rises, oxygen is released into the atmosphere and vice versa, this is how the dynamic interaction between the atmosphere and the hydrosphere occurs. The same inverse relationship exists between oxygen content and salinity: the higher the salinity, the less oxygen. The dependence of oxygen content on pressure is direct: the higher the pressure, the more oxygen is dissolved in water. The greatest amount of oxygen is contained on the surface of the water (due to the atmosphere and photosynthesis) and on 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 water, 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, organic matter and river waters. Consumption: photosynthesis, formation of carbonate minerals. The CO 2 content is also regulated by temperature; in the upper heated layers of sea water, the solubility of CO 2 decreases and it is released into the atmosphere. A shortage of it is created, which leads to the formation of insoluble calcium carbonate CaCO 3, which precipitates. Cold waters have a high CO 2 content.

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

Hydrogen sulfide It has a limited distribution and is confined to closed basin seas that communicate with the World Ocean through narrow, shallow straits. This disrupts the water exchange between them. For example, the Black Sea, contamination with hydrogen sulfide begins at approximately a depth of 150 m and increases with depth, and in the bottom part 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), and a certain amount of turbidity and suspended matter is also present.

Temperature of the world's 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 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 remains unchanged over a long period of observation, all heat flows in total are equal to zero.

The distribution of temperature over the surface of the World Ocean depends mainly on the latitude of the area, therefore the highest temperatures are located in the equatorial zone (thermal equator). Continents, prevailing winds, and currents have a distorting influence. 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). Temperature decreases with depth. In open parts of the ocean this happens relatively quickly up to 100 m. 300-500 m and much slower up to gl. 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 predominantly +2 o C and 0 o C, reaching -1 o C in the Arctic Ocean. In some deep-sea depressions with ch. 3.5 - 4 km and to the bottom the water temperature rises slightly (for example, the Philippine Sea). A significant increase in the temperature of the bottom layer of water up to 62 o C in some depressions of the Red Sea should be considered as an anomalous phenomenon. Such deviations from the general pattern are a consequence of the influence of deep processes occurring in the bowels of the earth.

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

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

Thickness – from several 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 is formed in spring and disappears in winter (its depth is 50-150 m). The second, called the “main thermocline,” exists year-round and lies at relatively great depths. Two types of thermocline occur in temperate climate zones.

The thermocline is also characterized by a change in the optical properties of water; fish fleeing from predators take advantage of this: 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 value 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 o 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 o C and a salinity of 35‰ is 1.028126 g/cm 3 .

Density is distributed unevenly over the surface: it is minimal in the equatorial zone (1.0210 g/cm3) and maximum 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 at the bottom.

Sea water pressure

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. The pressure can be calculated using the formula:

Р = Н ּρ/100,

P – pressure in MPa,

H – depth for which the calculation is made,

ρ density of sea water.

Under the influence of pressure from overlying layers, the specific volume of sea water decreases, i.e. it is compressed, but this value is insignificant: at S = 35‰ and t = 15 o C it is equal to 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 rise 30 m.

In addition to the thermocline (temperature jump), there is also a pressure jump - pycnocline. Sometimes several pycnoclines are identified in a sea 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 with propellers.

Temperature regime of MO waters. The temperature regime of MO waters is determined by the thermal balance. The ocean receives heat from total solar radiation. from moisture condensation on the water surface, ice formation and chemical and biological processes that occur with the release of heat; the ocean receives heat brought by precipitation and river waters; the temperature of the deep-sea layers is affected by the warmth of the Earth (this is evidenced by high temperatures up to 260 0 C in the depressions of the Red Sea - the water here is a hot brine with a salinity of 270 0 / 00). Heat is lost due to effective radiation of the water surface, water evaporation, ice melting, turbulent exchange with the atmosphere, heating of cold water in rivers and currents. The incoming solar radiation and heat consumption for evaporation are of decisive importance in the heat balance.

The average annual temperature of the Moscow Region is 17.4 0 C, the highest average annual water temperature was noted for the Pacific Ocean (19.1 0 C), the lowest - for the Arctic Ocean (0.75 0 C). The distribution of heat in the ocean water occurs due to convection and mixing as a result of waves and currents. The water temperature decreases with depth. At a certain depth in the water column, a sharp decrease in temperature is observed; here a layer of temperature jump stands out - thermocline Based on changes in water temperature with depth, several types of temperature distribution are distinguished.

IN equatorial type the water temperature quickly decreases from 26.65 0 C on the surface to 10.74 0 C at a depth of 300 m. The thermocline is observed at a depth of 200-300 m. Further, to a depth of 1000 m, the water temperature decreases slowly, and deeper remains almost constant.

IN tropical type the water temperature drops sharply from 26.06 0 C to 13.60 0 C at a depth of 300 m, then the water temperature changes more smoothly.

IN subtropical type the water temperature decreases from 20.3 0 C at the surface to 13.1 0 C at a depth of 300 m. In the subpolar type, the temperature decreases from 8.22 0 C at the surface to 5.20 0 C at a depth of 150 m. The polar type is characterized by a decrease water temperature to a depth of 100 m, then the temperature begins to rise to 1.8 0 C at a depth of 400 m. Due to the influx of warm Atlantic waters. At a depth of 1000 m, the water temperature is 1.55 0 C. In the layer from the surface to a depth of 1000 m, a zonal change in temperature and salinity of water is observed; deeper water characteristics remain almost constant.

Physicochemical properties of MO waters. Back at the beginning of the 19th century. It was noticed that the amount of salts dissolved in ocean waters can vary greatly, but the salt composition and the ratio of various salts in the ocean waters are the same. This pattern is formulated as a property of constancy of the salt composition of sea waters. Per 1 kg of sea water there are 19.35 g of chlorine, 2.70 g of sulfates, 0.14 g of bicarbonates, 10.76 g of sodium, 1.30 g of magnesium, 0.41 g of calcium. The quantitative ratio between the main salts in MO water remains constant. Total salinity is determined by the amount of chlorine in water (the formula was obtained by M. Knudsen in 1902):

S = 0.030 + 1.805 Cl

The waters of the oceans and seas belong to the chloride class and the sodium group, in this they differ sharply from river waters. Just eight ions account for more than 99.9% of the total mass of salts in seawater. The remaining 0.1% accounts for all other elements of the D.I. table. Mendeleev.

The distribution of salinity in water masses is zonal and depends on the ratio of precipitation, influx of river water and evaporation. In addition, the salinity of water is influenced by water circulation, the activity of organisms and other reasons. At the equator, there is a reduced salinity of water (34-33 0/00), due to a sharp increase in precipitation, the flow of full-flowing equatorial rivers and slightly reduced evaporation due to high humidity. In tropical latitudes, the highest water salinity is observed (up to 36.5 0/00), associated with high evaporation and small amounts of precipitation at baric pressure maxima. In temperate and polar latitudes, water salinity is reduced (33-33.5 0/00), which is explained by an increase in precipitation, river runoff and melting sea ice.

The latitudinal distribution of salinity is disrupted by currents, rivers and ice. Warm ocean currents transport saltier waters towards high latitudes, while cold currents transport less salty waters towards low latitudes. Rivers desalinate the estuarine areas of oceans and seas. The influence of the Amazon rivers is very great (the desalination influence of the Amazon is felt at a distance of 1000 km from the mouth), Congo, Niger, etc. Ice has a seasonal effect on the salinity of waters: in winter, when ice forms, the salinity of water increases, in summer, when ice melts, it decreases.

The salinity of the deep waters of the Moscow Region is uniform and generally amounts to 34.7-35.0 0 / 00. The salinity of bottom waters is more varied and depends on volcanic activity on the ocean floor, the release of hydrothermal waters, and the decomposition of organisms. The nature of changes in the salinity of ocean waters with depth is different at different latitudes. There are five main types of changes in salinity with depth.

IN equatorial latitudes salinity gradually increases with depth and reaches its maximum value at a depth of 100 m. At this depth, saltier and denser waters of the tropical latitudes of the oceans approach the equator. To a depth of 1000 m, salinity very slowly increases to 34.62 0/00, deeper salinity remains virtually unchanged.

IN tropical latitudes salinity increases slightly to a depth of 100 m, then gradually decreases to a depth of 800 m. At this depth, the lowest salinity is observed in tropical latitudes (34.58 0 / 00). Obviously, less salty but colder waters of high latitudes spread here. From a depth of 800 m it increases slightly.

IN subtropical latitudes salinity quickly decreases to a depth of 1000 m (34.48 0/00), then becomes almost constant. At a depth of 3000 m it is 34.71 0 / 00.

IN subpolar latitudes salinity slowly increases with depth from 33.94 to 34.71 0/00, in polar latitudes Salinity increases more significantly with depth - from 33.48 to 34.70 0 / 00.

The salinity of the seas is very different from the salinity of the sea. The salinity of water in the Baltic (10-12 0/00), Black (16-18 0/00), Azov (10-12 0/00), White (24-30 0/00) seas is due to the desalinating influence of river waters and atmospheric precipitation . The salinity of water in the Red Sea (40-42 0/00) is explained by low precipitation and high evaporation.

The average salinity of the Atlantic Ocean waters is 35.4; Quiet – 34.9; Indian - 34.8; Arctic Ocean – 29-32 0/00.

Density– the ratio of the mass of a substance to its volume (kg/m3). The density of water depends on the salt content, temperature and depth at which the water is located. As the salinity of water increases, the density increases. The density of water increases with decreasing temperature, with increasing evaporation (as the salinity of water increases), and with the formation of ice. Density increases with depth, although very slightly due to the low compressibility coefficient of water.

The density of water varies zonally from the equator to the poles. At the equator, the water density is low - 1022-1023, which is due to low salinity and high water temperatures. Toward tropical latitudes, the density of water increases to 1024-1025 due to an increase in water salinity due to increased evaporation. In temperate latitudes, the density of water is average, in polar latitudes it increases to 1026-1027 due to a decrease in temperature.

The ability of water to dissolve gases depends on temperature, salinity and hydrostatic pressure. The higher the temperature and salinity of the water, the less gases can dissolve in it.

Various gases are dissolved in ocean water: oxygen, carbon dioxide, ammonia, hydrogen sulfide, etc. Gases enter the water from the atmosphere due to river runoff, biological processes, and underwater volcanic eruptions. Oxygen is of greatest importance for life in the ocean. It is involved in planetary gas exchange between the ocean and atmosphere. 5 x 10 10 tons of oxygen are produced annually in the active layer of the ocean. Oxygen comes from the atmosphere and is released during photosynthesis of aquatic plants, spent on respiration and oxidation.

Carbon dioxide is found in water mainly in a bound state, in the form of carbon dioxide compounds. It is released during the respiration of organisms, during the decomposition of organic matter, and is used for the construction of skeletons by corals.

Nitrogen is always present in ocean water, but its content relative to other gases is less than in the atmosphere. In some seas, hydrogen sulfide can accumulate in the depths; this occurs due to the activity of bacteria in an oxygen-free environment. Hydrogen sulfide pollution has been noted in the Black Sea; its content has reached 6.5 cm 3 /l; organisms do not live in such an environment.

Water clarity depends on the scattering and absorption of solar radiation, on the amount of mineral particles and plankton. The highest transparency is observed in the open ocean at tropical latitudes and is equal to 60 m. Water transparency decreases in shallow water near river mouths. Water transparency decreases especially sharply after a storm (up to 1 m in shallow water). The least transparency is observed in the ocean during the period of active plankton reproduction. The depth of penetration of sunlight into the ocean and, consequently, the distribution of photosynthetic plants depends on the transparency of the water. Organisms that can absorb solar energy live at depths of up to 100 m.

The thickness of clear water has a blue or dark blue color, a large amount of plankton leads to the appearance of a greenish tint, and near rivers the water may be brown.

Salinity. Ocean water by weight consists of 96.5% pure water and 3.5% dissolved minerals, gases, trace elements, colloids and suspended matter of organic and inorganic origin. The composition of sea water includes all known chemical elements. Ocean water contains the most sodium, i.e. table salt NaCl (27.2 g per 1 liter), so the ocean water tastes salty. This is followed by magnesium salts - MgCl (3.8 g per 1 l) and MgSO 4 (1.7 g per 1 l), which give the water a bitter taste. All other elements, including biogenic elements (phosphorus, nitrogen, etc.) and microelements, account for less than 1%, i.e. their content is negligible. The total amount of salts in the Ocean reaches 50 10 16 tons. When deposited, these salts can cover the bottom of the Ocean with a layer of about 60 m, the entire Earth with a layer of 45 m, and the land with a layer of 153 m. An amazing feature of ocean water is the constancy of the salt composition. The solution may have different concentrations in different parts of the Ocean, but the ratio of the main salts remains unchanged.

The average salinity of the World Ocean is 35‰. The Atlantic Ocean has the highest average salinity - 35.4‰, the Arctic Ocean has the lowest - 32‰. Deviations from the average salinity in either direction are caused mainly by changes in the inflow-outflow balance of fresh water. Atmospheric precipitation falling on the surface of the Ocean, runoff from land, and melting ice cause a decrease in salinity; evaporation and ice formation – on the contrary, increase it. Since changes in salinity are associated mainly with the inflow and outflow of fresh water, they are noticeable only in the surface layer, which directly receives precipitation and evaporates water, and in some layer below it (up to a depth of 1500 m), determined by the depth of mixing. The deeper salinity of the waters of the World Ocean remains unchanged (34.7 – 34.9 ‰).

The salinity of sea water is closely related to its density. Ocean water density– the ratio of the mass of a unit of its volume at a given temperature to the mass of pure water of the same volume at a temperature of + 4°C. The density of ocean water always increases with increasing salinity, since the content of substances that have a greater specific gravity than water increases. An increase in the density of surface water layers is facilitated by cooling, evaporation and ice formation. Heating, as well as mixing of salt water with precipitation water or melt water, causes a decrease in density. At the ocean surface, there is a density variation ranging from 0.9960 to 1.083. In the open ocean, density is usually determined by temperature and therefore generally increases from the equator to the poles. With depth, the density of water in the Ocean increases.

Gases in Ocean water. Gases enter water from the atmosphere, are released during chemical and biological processes, they are brought by rivers, and they are released during underwater eruptions. Redistribution of gases occurs through mixing. The ability of ocean water to dissolve gases depends on its temperature, salinity and hydrostatic pressure. The higher the temperature and salinity of the water, the less gases can dissolve in it. Dissolved in water are primarily nitrogen (63%), oxygen (35%) and carbon dioxide, as well as hydrogen sulfide, ammonia, methane, etc.

Carbon dioxide, like oxygen, dissolves better in cold water. Therefore, when the temperature rises, the water releases it to the atmosphere, and when it decreases, it absorbs it. During the day, due to the increased consumption of carbon dioxide by plants, its content in water decreases; at night, on the contrary, it increases. At high latitudes the ocean absorbs carbon dioxide, at low latitudes it releases it into the atmosphere. The exchange of gases between the ocean and the atmosphere is a continuous process.

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 atm. All processes occurring at great depths occur under strong pressure, but this does not prevent the development of life in the depths of the Ocean.

Transparency. The radiant energy of the Sun, penetrating into the water column, is dissipated and absorbed. The degree of dissipation and absorption of solar energy depends on the amount of suspended particles contained in the water. The least transparency is observed off the coast in shallow water, due to an increase in the amount of suspended matter brought in by rivers and the agitation of the soil by waves. The transparency of water decreases significantly during the period of mass development of plankton and when ice melts (ice always contains impurities; in addition, the mass of air bubbles contained in the ice passes into the water). Water transparency increases in places where deep water rises to the surface.

Transparency is expressed by the number of meters, i.e. the depth at which a white disk with a diameter of 30 cm is still visible. The greatest transparency (67 m) was observed in the Central Pacific Ocean, in the Mediterranean Sea - 60 m, in the Indian Ocean - 50 m. In the North in the sea it is 23 m, in the Baltic Sea - 13 m, in the White Sea - 9 m, in the Azov Sea - 3 m.

The color of the water of oceans and seas. As a result of the collective absorption and scattering of light, the thickness of the ocean's clear water has a blue or blue color. The presence of plankton and inorganic suspended matter affects the color of the water, and it acquires a greenish tint. Large amounts of organic impurities make the water yellowish-green; near river mouths it can even be brown.

In equatorial and tropical latitudes, the dominant color of ocean water is dark blue and even blue. This color is the water, for example, in the Bay of Bengal, the Arabian Sea, the southern part of the China Sea, and the Red Sea. Blue water in the Mediterranean and Black Seas. In temperate latitudes, in many places the water is greenish (especially near the coast); it becomes noticeably greener in areas where the ice melts. In polar latitudes, greenish color predominates.

Glow of the sea. The glow of sea water is created by organisms emitting “living” light. These organisms include primarily luminous bacteria. In desalinated coastal waters, where such bacteria are mainly common, the glow of the sea is observed in the form of an even milky light. Glow is also caused by small and minute protozoa, of which the most famous is the night light (Noctiluca). Some larger organisms (large jellyfish, bryozoans, fish, annelids, etc.) are also distinguished by their ability to produce light. Sea glow is a phenomenon widespread throughout the world's oceans. It is observed only in sea water and never in fresh water.

Sea bloom represents the rapid development of zoo- and phytoplankton in the surface layers of the sea. Mass accumulations of these organisms cause changes in the color of the sea surface in the form of yellow, pink, milky, green, red, brown and other stripes and spots.

Sound conductivity There is 5 times more ocean water than air. In air, a sound wave moves at a speed of 332 m/s, in fresh water - 435 m/s, in ocean water - 1500 m/s. The propagation of sound in sea water depends on temperature, salinity, pressure, gas content, as well as suspended impurities of organic and inorganic origin.

World Ocean water temperature. The main source of heat received by the surface of the World Ocean is direct and diffuse solar radiation. River waters can serve as an additional source of heat. Part of the incoming solar radiation is reflected by the water surface, while part is emitted into the atmosphere and interplanetary space. The sea loses a large amount of heat to evaporation. A major role in the distribution and change in temperature of ocean waters belongs to the continents, prevailing winds and especially currents.

Sea waters, coming into contact with the atmosphere, exchange heat with it. If the water is warmer than the air, then heat is transferred to the atmosphere, but if the water is colder, it receives some heat through the process of heat exchange.

The heat coming from the Sun is absorbed by a thin surface layer and goes to heat the water, but due to the low thermal conductivity of water, it is almost not transferred to depth. The penetration of heat from the surface to the underlying layers occurs mainly through vertical mixing, as well as due to the advection of heat by deep currents. As a result of vertical mixing in the summer, colder waters rise to the surface and lower the temperature of the surface layers, while deep waters warm up. In winter, when surface waters are cooled, an influx of warmer waters occurs from the depths in the process of vertical exchange, delaying the onset of ice formation.

The average annual temperature on the surface of the Ocean is + 17.4°C, while the average annual air temperature is +14°C. The surface of the Pacific Ocean has the highest average temperature, most of which is located in low latitudes (+ 19.1°C), Indian (+ 17.1°C), and Atlantic (+ 16.9°C). Significant temperature changes occur only in the upper layers of ocean water with a thickness of 200 - 1000 m. Deeper, the temperature does not exceed + 4, + 5 ° C and changes very little. Due to the large heat capacity of water, the Ocean is an accumulator of solar heat on Earth.

The process of ice formation in sea and fresh water occurs differently - fresh water freezes at a temperature of 0 ° C (slightly below 0 ° C), and sea water freezes at different temperatures depending on salinity. The formation of ice in the Ocean begins with the formation of fresh crystals, which then freeze together. At the same time, droplets of strong brine remain in the space between the ice crystals, so when the ice is formed, it is salty. The lower the temperature at which ice formation occurred, the saltier the ice. The brine gradually flows between the crystals, so over time the ice becomes desalinated.

In the high latitudes of the northern hemisphere, the ice formed in winter does not have time to melt during the summer, so among the polar ice there is ice of different ages - from annual to multi-year. The thickness of first-year ice in the Arctic reaches 2–2.5 m, in the Antarctic 1–1.5 m. Multi-year ice has a thickness of 3–5 m or more. Where the ice is compressed, its thickness reaches 40 m. Ice covers about 15% of the entire water area of ​​the World Ocean, i.e. 55 million km 2, including 38 million km 2 in the southern hemisphere.

Ice cover has a huge impact on the climate of the entire Earth and on life in the Ocean.

Ice in the oceans and especially in the seas makes navigation and sea fishing difficult.

The concept of water masses. The waters of the World Ocean have very different physical and chemical properties. Large volumes of water formed in given physical and geographical conditions at certain periods of time and characterized by characteristic physical, chemical and biological properties are called water masses.

Water masses are formed mainly in the surface layers of the World Ocean under the influence of climatic conditions, processes of thermal and dynamic interaction between the ocean and the atmosphere. In the formation of water masses, the main role belongs to convective mixing, which, like other types of vertical exchange, ends with the formation of a homogeneous water mass. Currents transport water masses to other areas, where, in contact with waters of a different origin, they are transformed, especially along the periphery.

Movement of ocean waters

The entire mass of ocean waters is constantly moving. This ensures constant mixing of water, redistribution of heat, salts and gases. There are 3 types of movement: oscillatory– waves, progressive- ocean currents, mixed– ebbs and flows.

Waves. The main reason for the occurrence of waves on the surface of the World Ocean is wind. In some cases, waves reach a height of 18 m and a length of up to 1 km. The waves fade with depth.

During an earthquake, underwater volcanic eruption and underwater landslides, seismic waves arise, spreading from the epicenter in all directions and covering the entire water column. They're called tsunami. Ordinary tsunamis are waves that follow each other at intervals of 20–60 minutes at a speed of 400–800 km/h. In the open ocean, the height of the tsunami does not exceed 1 m. When approaching the shore - in shallow water, the tsunami turns into a giant wave up to 15 - 30 m. Such waves cause enormous destruction. The tsunami most often affects the eastern coasts of Eurasia, Japan, New Zealand, Australia, the Philippine and Hawaiian islands, and the southeastern part of Kamchatka.

Ocean currents. The forward movements of huge masses of water are called currents. This is the horizontal movement of water over long distances. There are currents wind(or drift), when the cause is the wind blowing in one direction. Sewage currents arise in the event of a constant rise in water level caused by its influx or heavy precipitation. For example, the Gulf Stream is caused by rising water levels due to influx from the neighboring Caribbean Sea. Compensatory Currents replace the loss of water in any part of the ocean. When the wind constantly blows from land to sea, it drives away surface waters, in whose place cold waters rise from the depths. Density currents are the result of different densities of water at the same depth. They can be observed in straits connecting seas with different salinities. For example, along the Bosphorus Strait, more salty and dense water flows along the bottom from the Mediterranean Sea to the Black Sea, and fresher water flows towards this flow on the surface.

Currents disrupt the latitudinal zonality in the temperature distribution. In all three oceans - the Atlantic, Indian and Pacific - temperature anomalies arise under the influence of currents: positive anomalies are associated with the transfer of warm waters from the equator to higher latitudes by currents that have a direction close to the meridional direction; negative anomalies are caused by oppositely directed (from high latitudes to the equator) cold currents. Currents influence the distribution of other oceanological characteristics: salinity, oxygen content, nutrients, color, transparency, etc. The distribution of these characteristics has a huge impact on the development of biological processes, flora and fauna of the seas and oceans.

Mixed currents- ebbs and flows resulting from the axial rotation of the Earth and the attraction of the planet by the Sun and Moon. At each point on the surface of the Ocean, there is a high tide 2 times a day and an ebb tide 2 times. The height of a tidal wave in the open ocean is about 1.5 m, and off the coast it depends on their configuration. The highest tide in the Bay of Fundy off the coast of North America in the Atlantic Ocean is 18 m.

The ocean as a living environment

In the World Ocean, life exists everywhere - in different forms and different manifestations. According to the conditions of existence in the Ocean, two different areas are distinguished: the water column (pelagial) and the bottom (benthal). Benthal is divided into coastal - littoral, having depths of up to 200 m, and deep - abyssal The abyssal region is represented by peculiar organisms adapted to living in conditions of low temperature, high pressure, lack of light and relatively low oxygen content.

The organic world of the Ocean consists of three groups: benthos, plankton, nekton . Benthos– inhabitants of the bottom (plants, worms, mollusks), unable to rise into the water column for a long time. Plankton– inhabitants of the water column (bacteria, fungi, algae, protozoa, etc.) that do not have the ability to actively move over long distances. Nekton– inhabitants of the waters that freely swim long distances (whales, dolphins, fish) .

Green plants can develop only where the lighting is sufficient for photosynthesis (to a depth of no more than 200 m). Most of the mass of living matter in the Ocean is made up of phytoplankton, which inhabit the upper 100-meter layer of water. The average mass of phytoplankton is 1.7 billion tons, annual production is 550 billion tons. The most common form of phytoplankton is diatoms, represented by 15 thousand species. One diatom can produce 10 million specimens per month. It is only because phytoplankton quickly dies off and is eaten in large quantities that it has not filled the Ocean. Phytoplankton is the initial link in the food chain in the Ocean. Places of abundant development of phytoplankton are places of increased fertility in the Ocean, rich in life in general.

The distribution of life in the Ocean is very uneven and has a clearly defined zonal character. In the high latitudes of the northern hemisphere, the conditions for the development of phytoplankton are unfavorable - continuous ice cover, polar night, low position of the Sun above the horizon in summer, cold (below 0°C) water, weak vertical circulation (a consequence of the desalination of the upper layer of water), which does not ensure the removal of nutrients from the depths In summer, some cold-loving fish and fish-eating seals appear in the polynyas.

IN subpolar latitudes Seasonal migration of the polar ice edge occurs. In the cold part of the year, in a layer of several hundred meters, the water is intensively mixed (a consequence of cooling), enriched with oxygen and nutrient salts. In spring and summer there is a lot of light, and, despite the relatively low temperature of the water (the result of heat expended on melting), a mass of phytoplankton develops in it. This is followed by a short period of development of zooplankton feeding on phytoplankton. During this period, a lot of fish accumulate in the subpolar zone (herring, cod, haddock, sea bass, etc.). Whales come to feed, which are especially numerous in the southern hemisphere.

IN temperate latitudes In both hemispheres, strong mixing of water, sufficient heat and light create the most favorable conditions for the development of life. These are the most productive zones of the Ocean. Maximum development of phytoplankton is observed in spring. It absorbs nutrients, their quantity decreases - the development of zooplankton begins. In autumn there is a second maximum of phytoplankton development. The abundance of zooplankton determines the abundance of fish (herring, cod, anchovy, salmon, sardine, tuna, flounder, halibut, navaga, etc.).

IN subtropical and tropical At latitudes, the water on the surface of the Ocean has increased salinity, but due to the high temperature it turns out to be relatively light, which interferes with mixing. Particles containing nutrients do not linger and sink to the bottom. Oxygen is 2 times less than in the temperate zone. Phytoplankton develops weakly, and there is little zooplankton. In subtropical latitudes, water has the greatest transparency and intense blue color (the color of the ocean desert). In warm water, brown algae, sargassum, which is not associated with the bottom, grow, typical of this part of the Ocean.

IN equatorial latitudes At the border of trade wind currents and the equatorial countercurrent, water is mixed, and therefore it is relatively rich in nutrient salts and oxygen. There is much more plankton here than in neighboring latitudes, although not as much as on the northern edge of the temperate zone.

Warm water contains little carbon dioxide and therefore does not dissolve calcium carbonate well, which is found in abundance and is easily absorbed by plants and animals. As a result, the shells and skeletons of animals become massive and durable, and after the organisms die off, thick layers of carbonate sediments, coral reefs and islands, so characteristic of low latitudes, are formed.

The latitudinal zonality of the distribution of life in the upper layers of the Ocean, well expressed in its open part, is disrupted on the outskirts under the influence of winds and currents.