Water is the most abundant substance on earth. The water shell of the Earth developed along with the lithosphere, atmosphere and wildlife. Almost all processes on our planet proceed with the participation of water. The hydrosphere consists of the oceans, land waters and groundwater. The bulk of the water is concentrated in the oceans.

The World Ocean is the blue mirror of our planet, the cradle of life on Earth. It contains not only the past, but also the future of our planet. To understand the great role of the ocean, it is necessary to know the features of its nature: the properties of water masses, to understand the role of currents, the significance of the interaction of the ocean with the atmosphere and land. You will learn about all this by studying this topic.

§ 9. Waters of the oceans

1. What is called the hydrosphere? World Ocean?
2. What do you already know about the nature of the ocean?
3. Make a characterization of the map of the oceans (see the plan in the appendix).

The role of the ocean in the life of the Earth. The ocean occupies almost 3/4 of the surface of our planet (Fig. 22). Water is one of the most amazing substances on Earth, a precious liquid, a gift of nature to our planet. In such quantities as on Earth, it is not found anywhere in the solar system.

Rice. 22. The area of ​​land and ocean: a) in general on Earth; b) in the Northern Hemisphere; c) in the southern hemisphere

The ocean... It is hard to imagine how great its importance in the life of the Earth. Clouds in the sky, rain and snow, rivers and lakes, springs - all these are particles of the ocean that have only temporarily left it.

The ocean determines many features of the nature of the Earth: it gives the atmosphere the accumulated heat, nourishes it with moisture, part of which is transferred to the land. It has a great influence on climate, soil, vegetation and animal world sushi. Its role in human economic activity is great. The ocean is a healer, giving medicines and taking millions of vacationers to its shores. He is a source of seafood, many minerals, energy; he is the "kitchen of the weather", and the most spacious road in the world connecting the continents. Thanks to the work of bacteria, the ocean has the ability (up to a certain limit) to cleanse itself, and therefore many of the waste generated on Earth is destroyed in it.

The history of mankind is inextricably linked with the study and development of the ocean. Its knowledge began in ancient times. (When? By whom?) Especially a lot of new data was obtained for recent decades by using latest technology. Research carried out on scientific vessels, collected by automatic oceanographic stations, as well as artificial satellites The Earth helped to detect eddies in the waters of the ocean, deep countercurrents, to prove the existence of life at great depths. The study of the structure of the ocean floor made it possible to create a theory of the movement of lithospheric plates.

Origin of the waters of the oceans. The ocean is the main custodian of water, the most common substance on Earth, which has long amazed researchers with its unusual properties. Only water under normal terrestrial conditions can be in three states. This property ensures the omnipresence of water. It permeates the entire geographic shell and performs a variety of work in it.

How did water appear on Earth? Finally, this “survey” has not yet been resolved by science. It is assumed that water either released immediately during the formation of the lithosphere from the upper mantle, or accumulated gradually. Water is still released from magma, falling on the surface of the planet during volcanic eruptions, during the formation of oceanic crust in the zones of stretching of lithospheric plates. This will continue for many millions of years. Part of the water comes to Earth from space.

properties of ocean waters. Their most characteristic properties - salinity and temperature - are already known to you. (Recall their key metrics from grade 6.) Oceanic mode is a weak solution in which almost no chemical substances. Gases, mineral and organic substances, formed as a result of vital activity of organisms, are dissolved in it.

The main changes in salinity are observed in the surface layer. The salinity of waters depends mainly on the ratio of atmospheric precipitation and evaporation, which varies depending on the geographical latitude. At the equator, the salinity is about 34%.., near the tropics - 36%, and in temperate and polar latitudes - about 33%. Salinity is less where the amount of precipitation exceeds evaporation, where there is a large influx of river waters, where ice melts.

You know that the waters of the ocean are heated, like the land, from the influx of solar heat on its surface. Occupying large area ocean receives more heat than land. The temperature of surface waters varies and is distributed depending on the latitude (Fig. 23). In some areas of the ocean, this regularity is disturbed by ocean currents, and in coastal parts, by the runoff of warmer waters from the continents. The temperature of the ocean water also changes with depth. At first, its decrease is very significant, and then it slows down. At depths of more than 3-4 thousand meters, the temperature usually ranges from +2 to 0 °C.

Rice. 23. The average annual water temperature on the surface of the oceans. Compare water temperatures at the same latitudes. Explain the result

Ice in the ocean. The formation of ice depends on the temperature of ocean waters. You already know that sea water freezes at -2°C. As salt water cools, the density of salt water increases, its upper layer becomes heavier and sinks down, and warmer layers of water rise to the surface. This mixing of the water prevents the formation of ice. Ice forms only in arctic and subarctic latitudes, where winters are long and very cold. Some shallow seas located in the temperate zone also freeze. Distinguish between annual and multi-year ice. Ocean ice can be immobile if it is connected to the land, or floating, i.e. drifting. In the ocean, there are ices that have broken off from the glaciers of the land and descended into the ocean - icebergs (Fig. 24).

Rice. 24. Melting icebergs in the ocean

The ice cover of the ocean has a huge impact on the climate of the Earth, on life in it. Ice reflect Sun rays, cool the air, contribute to the formation of fogs. They impede navigation and marine fisheries.

water masses. Water is the main component of the nature of the ocean. Large volumes of water that form in certain parts of the ocean and differ from each other in temperature, salinity, density, transparency, the amount of oxygen, the presence of certain living organisms, are called water masses. These properties are preserved throughout the space occupied by one or another water mass.

In the ocean, surface, intermediate, deep, and bottom water masses are distinguished. In surface fashionable masses up to a depth of 200 m, equatorial masses are distinguished. tropical, temperate and polar water masses. They are formed as a result of the uneven supply of solar heat at different latitudes and the influence of the atmosphere. In the same latitudes, the properties of surface water masses may differ, therefore, coastal and intra-oceanic masses are also distinguished.

Water masses actively interact with the atmosphere: they give it heat and moisture, absorb carbon dioxide from it, and release oxygen. When mixed, they change their properties.

1. What determines the salinity of ocean waters?
2. What are the differences in ocean water temperature?
3. Where does ice form in the ocean? How do they affect the nature of the Earth and economic activity human?
4. What is a water mass? Name the main types of water masses. What water masses are isolated in the surface layer of the ocean?

Natural complexes in the oceans are less studied than on land. However, it is well known that in the World Ocean, as well as on land, the law of zoning operates. Along with latitudinal zonality, deep zonality is also represented in the World Ocean. Latitudinal zones of the World Ocean Equatorial and tropical zones are found in three oceans: Pacific, Atlantic and Indian. The waters of these latitudes are characterized by high temperature, at the equator with […]

The oceans are in constant motion. In addition to waves, the calm of the waters is disturbed by currents, ebbs and flows. All this different types movement of water in the oceans. Wind waves It is difficult to imagine an absolutely calm expanse of the ocean. Calm - complete calm and the absence of waves on its surface - a rarity. Even in calm and clear weather, ripples can be seen on the surface of the water. And this […]

About 71% of the Earth's surface is covered by ocean waters. The oceans are the largest part of the hydrosphere. The ocean and its parts The World Ocean is the name given to the entire continuous water space of the Earth. The surface area of ​​the World Ocean is 361 million square kilometers, but its waters make up only 1/8oo of the volume of our planet. In the World Ocean, separate parts separated by continents are distinguished. These are oceans - vast areas of the single World Ocean, differing in […]

The waters of the oceans are never at rest. Movements occur not only in the surface water masses, but also in the depths, down to the bottom layers. Water particles perform both oscillatory and translational movements, usually combined, but with a noticeable predominance of one of them. Wave movements (or excitement) - predominantly oscillatory movements. They are fluctuations […]

The freezing point of water with average salinity is 1.8°C below 0°. The higher the salinity of water, the lower its freezing point. The formation of ice in the ocean begins with the formation of fresh crystals, which then freeze. Between the crystals are droplets of salt water, which gradually drains, so young ice is more salty than old, desalinated ice. The thickness of the first-year ice reaches 2-2.5 m, and […]

The ocean receives a lot of heat from the Sun - occupying a large area, it receives more heat than land. Water has a high heat capacity, so a huge amount of heat accumulates in the ocean. Only the upper 10-meter layer of ocean water contains more heat than the entire atmosphere. But the sun's rays heat only the upper layer of water, heat is transferred down from this layer as a result of […]

3/4 of our planet is covered by the oceans, so it looks blue from space. The world ocean is one, although it is strongly dissected. Its area is 361 million km2, the volume of water is 1,338,000,000 km3. The term "World Ocean" was proposed by Shokalsky Yu.M. (1856 - 1940), Russian geographer and oceanographer. The average depth of the ocean is 3700 m, the greatest is 11,022 m (Marian […]

The World Ocean, divided by continents and islands into separate parts, is a single body of water. The boundaries of the oceans, seas and bays are conditional, since there is a constant exchange of water masses between them. The world ocean as a whole has common features of nature and manifestations of similar natural processes. Research of the World Ocean Pervaya russkaya round the world expedition 1803-1806 under the command of I.F. Kruzenshtern and […]

Having reached the sea or the ocean, the fragment would like to calmly lie down on the bottom and “think about its future”, but that was not the case. Water environment has its own forms of movement. Waves, attacking the shores, destroy them and deliver large fragments to the bottom, icebergs carry huge blocks that eventually sink to the bottom, undercurrents carry silt, sand and even blocks […]

The temperature of the waters of the World Ocean The salinity of the waters of the World Ocean The properties of the waters of the World Ocean The world ocean makes up 96% of the mass of the entire hydrosphere. This is a huge body of water that occupies 71% of the Earth's surface. It extends in all latitudes and in all climatic zones of the planet. This is a single indivisible body of water, divided by continents into separate oceans. The question of the number of oceans remains open […]

Ocean currents - the movement of water in a horizontal direction The reason for the formation of ocean currents is the winds constantly blowing on the surface of the planet. Currents are warm and cold. The temperature of the currents in this case is not an absolute value, but depends on the temperature of the surrounding water in the ocean. If the surrounding water is colder than the current, it is warm; if it is warmer, then the current is considered cold. […]

Russian climatologist Alexander Ivanovich Voeikov called the World Ocean the "heating system" of the planet. Indeed, the average water temperature in the ocean is +17°C, while the air temperature is only +14°C. The ocean is a kind of heat accumulator on Earth. Water heats up much more slowly due to its low thermal conductivity compared to solid land, but it also consumes heat very slowly, […]

The ocean is a huge pantry natural resources, which in their potential are comparable to land resources. Mineral resources are subdivided into the resources of the shelf zone and the deep-water bottom. The resources of the shelf zone are: Ore (iron, copper, nickel, tin, mercury), at a distance of 10-12 km from the coast - oil, gas. The number of oil and gas basins on the shelf is more than 30. Some basins are purely marine […]

The world ocean includes all the seas and oceans of the Earth. It occupies about 70% of the planet's surface, it contains 96% of all water on the planet. The world ocean consists of four oceans: Pacific, Atlantic, Indian and Arctic. The size of the Pacific oceans - 179 million km2, Atlantic - 91.6 million km2 Indian - 76.2 million km2, Arctic - 14.75 […]

Boundless and great oceans. He is incredibly formidable to people in the hours of bad weather. And then it seems that there is no force that could cope with the mighty abyss. Alas! This impression is deceptive. A serious danger threatens the ocean: drop by drop, substances alien to the ocean environment rush into the ocean, poisoning the water and destroying living organisms. So what is the danger looming [...]

The oceans are called the treasury of the planet. And this is no exaggeration. Sea water contains almost all chemical elements periodic system. There are even more treasures in the bowels of the seabed. For centuries, people did not suspect this. Unless in fairy tales the sea king owned untold riches. Mankind has become convinced that the ocean hides huge reserves of completely unfabulous treasures only in […]

Organic life on our planet originated in the ocean environment. Tens of millions of years, all the wealth organic world limited to aquatic species. And in our days, when the land was inhabited by living organisms a long time ago, species that are hundreds of millions of years old have been preserved in the ocean. Many secrets still keep the ocean depths. Not a year goes by without biologists reporting the discovery of […]

As a result of the fact that sea water is saturated with salts, its density is slightly higher than that of fresh water. In the open ocean, this density is most often 1.02 - 1.03 g/cm3. The density depends on the temperature and salinity of the water. It grows from the equator to the poles. Its distribution, as it were, follows the geographical distribution of the spinning top temperature. but with the opposite sign. This […]

In the oceans, the same climatic zones are distinguished as on land. Some oceans do not have certain climatic zones. For example, there is no Arctic zone in the Pacific Ocean. In the oceans, it is possible to distinguish between the surface water column, heated by solar heat, and the cold deep water column. The thermal energy of the Sun penetrates into the depths of the ocean due to the mixing of water masses. Most actively stirs […]

The only source of practical importance that controls the light and heat regime of water bodies is the sun.

If the sun's rays falling on the surface of the water are partly reflected, partly spent on the evaporation of water and illuminating the layer where they penetrate, and partly absorbed, then it is obvious that the heating of the surface layer of water occurs only due to the absorbed part of the solar energy.

It is no less obvious that the laws of heat distribution on the surface of the World Ocean are the same as the laws of heat distribution on the surface of continents. Particular differences are explained by the high heat capacity of water and the greater homogeneity of water compared to land.

In the northern hemisphere, the oceans are warmer than in the southern, because in the southern hemisphere there is less land, which greatly heats the atmosphere, and there is also wide access to the cold Antarctic region; in the northern hemisphere there is more land, and the polar seas are more or less isolated. The thermal equator of water is located in the northern hemisphere. Temperatures naturally decrease from the equator to the poles.

The average surface temperature of the entire World Ocean is 17°.4, i.e., 3° ​​higher than the average air temperature on the globe. The high heat capacity of water and turbulent mixing explain the presence of large reserves of heat in the oceans. For fresh water, it is equal to I, for sea water (with a salinity of 35‰) it is slightly less, namely 0.932. On average annual output, the warmest ocean is the Pacific (19°.1), followed by the Indian (17°) and the Atlantic (16°.9).

Temperature fluctuations on the surface of the World Ocean are immeasurably smaller than air temperature fluctuations over the continents. The lowest reliable temperature observed on the surface of the ocean is -2°, the highest is +36°. Thus, the absolute amplitude is not more than 38°. As for the amplitudes of average temperatures, they are even narrower. The daily amplitudes do not go beyond 1°, and the annual amplitudes, which characterize the difference between the average temperatures of the coldest and warmest months, range from 1 to 15°. In the northern hemisphere for the sea, the warmest month is August, the coldest is February; vice versa in the southern hemisphere.

According to thermal conditions in the surface layers of the World Ocean, tropical waters, waters of the polar regions and waters of temperate regions are distinguished.

Tropical waters are located on both sides of the equator. Here in the upper layers the temperature never drops below 15-17°, and in large areas the water has a temperature of 20-25° and even 28°. Annual temperature fluctuations do not exceed 2° on average.

The waters of the polar regions (in the northern hemisphere they are called arctic, in the southern hemisphere antarctic) are distinguished by low temperatures, usually below 4-5 °. The annual amplitudes here are also small, as in the tropics - only 2-3°.

The waters of the temperate regions occupy an intermediate position - both territorially and in some of their features. Part of them, located in the northern hemisphere, was called the boreal region, in the southern - the notal region. In boreal waters, the annual amplitudes reach 10°, and in the notal region, they are half as much.

The transfer of heat from the surface and the depths of the ocean is practically carried out only by convection, i.e., by the vertical movement of water, which is caused by the fact that the upper layers turned out to be denser than the lower ones.

The vertical temperature distribution has its own characteristics for the polar regions and for the hot and temperate regions of the World Ocean. These features can be summarized in the form of a graph. The upper line represents the vertical temperature distribution at 3°S. sh. and 31°W d. in the Atlantic Ocean, i.e., serves as an example of a vertical distribution in tropical seas. What is striking is the slow decrease in temperature in the very surface layer, the sharp drop in temperature from a depth of 50 m to a depth of 800 m, and then again a very slow drop from a depth of 800 m and below: the temperature here almost does not change, and, moreover, it is very low (less than 4 °C). ). This constancy of temperature at great depths is explained by the complete rest of the water.

The lower line represents the vertical temperature distribution at 84°N. sh. and 80 ° in. etc., i.e. serves as an example of a vertical distribution in the polar seas. It is characterized by the presence of a warm layer at a depth of 200 to 800 m, overlapped and underlain by cold water with negative temperatures. The warm layers found both in the Arctic and in the Antarctic were formed as a result of the sinking of waters brought to the polar countries by warm currents, because these waters, due to their higher salinity compared to the desalinated surface layers of the polar seas, turned out to be denser and, therefore, heavier than local polar waters.

In short, in temperate and tropical latitudes there is a steady decrease in temperature with depth, only the rates of this decrease are different at different intervals: the smallest near the surface itself and deeper than 800-1000 m, the largest in the interval between these layers. For the polar seas, that is, for the Arctic Ocean and the southern polar space of the other three oceans, the pattern is different: the upper layer has low temperatures; with depth, these temperatures, rising, form a warm layer with positive temperatures, and under this layer, temperatures again decrease, with their transition to negative values.

This is the picture of vertical temperature changes in the oceans. As for individual seas, the vertical temperature distribution in them often deviates greatly from the patterns that we have just established for the World Ocean.

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Water is the simplest chemical compound hydrogen with oxygen, but ocean water is a universal homogeneous ionized solution, which includes 75 chemical elements. These are solid mineral substances (salts), gases, as well as suspensions of organic and inorganic origin.

Vola has many different physical and chemical properties. First of all, they depend on the table of contents and temperature environment. Let's give brief description 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 %O. Salts dissolved in water give it a bitter-salty taste.

About 27 out of 35 grams is sodium chloride ( salt), so the water is salty. Magnesium salts give it a bitter taste.

Since the water in the oceans was formed from hot salt solutions earth's interior and gases, its salinity was the original. 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 summer period salinity becomes less as a result of the melting of nearby icebergs and glaciers.

The saltiest of all oceans 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 used for the respiration of plants and animals in the upper layers. sea ​​waters and 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 high content 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 decay organic matter, but also produced by the respiration of marine organisms and their decomposition.

In the water column, in deep stagnant basins, as a result of the vital activity of organisms, hydrogen sulfide is formed, which is toxic and inhibits the biological productivity of 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, 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 — 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, highest values annual temperature fluctuations are observed in subtropical latitudes - 8-10 °C.

The temperature of ocean water also changes with depth. It decreases and already at a depth of 1000 m almost everywhere (on average) below 5.0 °C. At a depth of 2000 m, the water temperature levels 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 — characteristic property 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.

General information. The area of ​​the World Ocean is 361 million km/sq. In the northern hemisphere, the World Ocean occupies 61%, and in the southern - 81% of the area of ​​the hemispheres. For comfort Earth depicted in the form of so-called maps of the hemispheres. There are maps of the Northern, Southern, Western and Eastern hemispheres, as well as maps of the hemispheres of the oceans and continents (Fig. 7). In the oceanic hemispheres, 95.5% of the area is occupied by water.

World ocean: structure and history of research. The world ocean is one, it is not interrupted anywhere. From any of its points you can get to any other without crossing the land. According to scientists, the term ocean is borrowed from the Phoenicians and translated from ancient Greek means "a great river encircling the Earth."

The term "World Ocean" was introduced by the Russian scientist Yu.M. Shokalsky in 1917. In rare cases, the term "oceanosphere" is used instead of the term "World Ocean".

Map of the hemispheres of graphic discoveries, which cover the oceans from the second half of the 15th century to the first half of the 17th century. Great geographical discoveries are associated with the names of X. Columbus, J. Cabot, Vasco da Gama, F. Magellan, J. Drake, A. Tasman, A. Vespucci and others. its outlines, depth, salinity, temperature, etc.

Targeted Scientific research of the World Ocean were begun in the 17th century and are associated with the names of J. Cook, I. Kruzenshtern, Yu. Lisyansky, F. Bellingshausen, N. Lazarev, S. Makarov and others. ". The results obtained by the Challenger expedition laid the foundation for a new science - oceanography.

In the 20th century, the study of the World Ocean is carried out on the basis of international cooperation. Since 1920, work has been underway to measure the depths of the oceans. The outstanding French explorer Jean Picard was the first to sink to the bottom of the Mariana Trench in 1960. A lot of interesting information about the World Ocean was collected by the team of the famous French explorer Jacques Yves Cousteau. Space observations provide valuable information about the World Ocean.

The structure of the oceans. The World Ocean, as you know, is conditionally divided into separate oceans, seas, bays and straits. Each ocean is separate natural complex, conditioned geographic location, originality geological structure and living organisms.

The World Ocean in 1650 was first divided by the Dutch scientist B. Varenius into 5 parts, which are currently approved by the International Oceanographic Committee. As part of the World Ocean, 69 seas are distinguished, including 2 on land (Caspian and Aral).

Geological structure. The world ocean consists of large lithospheric plates, which, with the exception of the Pacific, are named after the continents.

River, glacial and biogenic deposits are found at the bottom of the World Ocean. The deposits of active volcanoes, as a rule, are confined to the mid-ocean ridges.

The relief of the bottom of the oceans. The relief of the bottom of the World Ocean, like the land relief, has a complex structure. The bottom of the World Ocean is usually separated from the land by a continental shelf, or shelf. At the bottom of the World Ocean, as well as on land, there are plains, mountain ranges, plateau-like elevations, canyons and depressions. Deep-sea depressions are a landmark of the World Ocean that cannot be found on land.

The mid-ocean ridges, together with the spurs, form a continuous single chain of mountains with a length of 60,000 km. The waters of the land are divided between five basins: the Pacific, Atlantic, Indian, Arctic and Inner closed. For example, rivers flowing into the Pacific Ocean or its constituent seas are called the rivers of the Pacific Basin, and so on.

A. Soatov, A. Abdulkasymov, M. Mirakmalov "Physical geography of continents and oceans" Publishing and printing art house "O`qituvchi" Tashkent-2013