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

It is known that water is an ideal solvent. Sea water is a gas-salt solution rich in quality composition. 44 chemical elements have been found in the water of the oceans. Most of all, chlorides are dissolved, which account for 88.7%, sulfates - 10.7%, carbonates and other elements - 0.8%. From this ocean water and bitter-salty taste. The salty taste is caused by a solution, and the bitter taste is caused by sulfate salts (MgSO 4 , CaBO, etc.). The salinity of the oceans is measured in% o (ppm). The average salinity of the World Ocean is 35% o, i.e., 35 g of salt are dissolved in 1 liter of water. The highest salinity is observed in tropical latitudes, where evaporation is high, and fresh water inflow is small. In the equatorial strip, salinity decreases somewhat due to the large amount of precipitation. In temperate latitudes, compared to tropical latitudes, salinity decreases again. Salinity fluctuations are small from 32 to 41% 0 . In the coastal seas of the Arctic Ocean, salinity decreases to 32%o, and in the Red Sea it reaches 41%o. The ratio of dissolved substances in the oceans does not change.

The seas of Russia, with the exception of the seas of the Pacific Ocean, have low salinity: the Baltic Sea - 8% o. Black Sea 14-19% o.

Salinity depends on the climate (it increases in dry climates). The distribution of salinity is also influenced by sea currents: warm ones increase it, cold ones decrease it. Salinity decreases where large rivers flow into the sea.

Numerous gases are dissolved in ocean water. Oxygen is of particular importance. It is more dissolved in cold waters than in warm ones.

Carbon dioxide, unlike oxygen and nitrogen, is bound state- in the form of carbonic compounds. Carbon dioxide is used by animals to build shells and bone parts of the body.

The color of ocean water in the thickness acquires a bluish tint . The transparency of water depends on impurities and is determined using a Sacchi disk. It is made of zinc with a diameter of 30 cm, painted white. When the disk is immersed in water, it is monitored at what depth it ceases to be visible. This depth determines the degree of water transparency.

Ocean water temperature. In the upper layers of the ocean, heat is distributed zonally. In the equatorial zone, the temperature rises within + 27-28°C, seasonal fluctuations are insignificant: 1-3°C. In tropical latitudes the water temperature is +20-25°С, in temperate latitudes - from 0 to +20°С, in polar latitudes - from 0С to -2°С.

The regional distribution of temperatures is determined by sea currents. In tropical latitudes, the western parts of the ocean are warmer than the eastern ones; the temperature difference reaches 10°. At northern latitudes, the eastern parts of the oceans are warmer than the western ones, and the temperature difference is also 10°.

The average temperature of the surface waters of the World Ocean is + 17.4 ° C, i.e., 3 ° higher than the land temperature. The highest recorded temperature is +36°C, the lowest is 2°C. The amplitude of fluctuations in water temperatures is 38°, while for air it is 145° (-87, +58°).

In the polar latitudes, ocean water freezes. Its freezing temperature depends primarily on salinity. So, at a salinity of 20% 0, water freezes at t-1.1°C.

Fresh water has the highest density at t+ 4 ° С, ocean - at lower temperatures. At a salinity of 35%o, the highest density of water is observed at t - 3.5 °.

When fresh water is cooled, its heavier layers but sink down, while warmer and lighter ones rise up. Mixing of water occurs until the entire mass is cooled to + 4 ° C. Further cooling leads to accumulation of lighter water on the surface, and then to freezing. In the ocean, the mixing of water does not stop because the density of water increases with decreasing temperature. In addition, when ocean water freezes, ice crystals are formed from fresh water, therefore, the total salinity of the waters increases. Therefore, the waters of the ocean freeze even at lower temperatures, and the excitement slows down this process.

The relief of the bottom of the oceans

For a correct idea of ​​the relief of the bottom of the World Ocean, it is necessary to measure its depths. Depth measurements are made in various ways. Shallow pools are measured using a simple lot consisting of a long cord with a weight at the end. But great depths cannot be measured with such a lot.

Currently, ultrasonic waves are used, they are sent and captured by special instruments that allow you to record depths along the route of the ship. The results of the measurements are put on a map. Places with equal depths are connected by lines called isobaths.

On school maps, the depths are applied by coloring; according to the depth scale, you can determine the depths of one or another part of the ocean.

The relief of the bottom of the oceans is diverse. These are mountain systems stretching for thousands of kilometers, plains with flatter elevations, continental slopes and deep-sea trenches (with depths from 6,000 to 11,000 m). Like land, the crust of the ocean floor is divided into stable areas - platforms covered with thick layers of sedimentary rocks, and geosynclines - moving areas. Geosynclinal regions stretch along the eastern coasts of Asia and Central America, as well as along the western coasts of North and South America. They represent huge troughs that are filled with sedimentary rocks.

The greatest mountain systems form mid-ocean ridges with a total length of up to 80 thousand km. Numerous rift ridges and valleys are located in their axial part. Rift valleys are associated with intense seismic and volcanic activity. These are the most active parts of the earth's crust. The width and height of the mid-ocean ridges are different. So, in the Atlantic Ocean, this system narrows to 370 km, while in others it expands to 2300 km with a height of 1-2 to 9 km. These are truly the largest mountain structures on Earth.

The movement of water in the oceans

The water in the oceans is in constant motion. There are three types of water movement: oscillatory, translational and mixed.

Oscillatory motions are observed in waves, translational motions in ocean currents, and mixed motions in tides.

Waves. The main reason for the formation of waves on the surface of the oceans is the wind. In some cases, they arise from earthquakes, changes in atmospheric pressure, and other reasons. Individual particles of water during wave motion move in circular orbits. In the upper part of the orbit, particles move in the direction of the wave, and in the lower part, in the opposite direction. This is why a thrown object oscillates on a wave, but does not move.

Ebb and flow. People who lived along the shores of the seas noticed that twice a day the sea level rises, flooding flat coasts, and falls twice a day, exposing the bottom of the sea.

The scheme of formation of ebbs and flows is complicated by the following reasons.

1. Tides are formed under the influence of attraction not only of the Moon, but also of the Sun. On the full moon and new moon, the lunar and solar eclipses coincide, so the tides reach their greatest magnitude.

2. Depending on the coastline of the continents, the height of the tides may increase or decrease.

ocean currents. The translational movements of huge masses of ocean water are called currents. As a result, the ocean water cycle occurs. Not only surface layers of water move, but also deep ones.

Wind is the main cause of surface currents. Winds that are constant in direction blow off the surface layers of water and force them to move.

Rivers

There are more than 200,000 rivers in Russia. A river is a natural, permanent watercourse flowing down a slope and enclosed in banks. Rivers originate from springs that come to the earth's surface. Many rivers originate in lakes and swamps, on mountain slopes from under glaciers. Temporary streams, streams and rivers form flowing waters. They level the surface of the Earth: they destroy hills, mountains and carry away the products of destruction to lower places. The value of flowing waters is very great in human economic activity. Springs, rivers and streams are the main sources of water supply. There are settlements along the streams and rivers, the rivers are used as a means of communication, as well as for the construction of hydroelectric power plants and fishing. In arid regions, river water is used for irrigation (Murgab, Tedzhen, Amudarya, Syrdarya, etc.).

Each river has a source, upper, middle and lower reaches, tributaries, mouth. Source - the place where the river originates. A mouth is a place where another river, lake, or sea flows into another. In deserts, rivers are sometimes lost in the sands, their water is used for evaporation and filtration.

The rivers flowing through any territory form a river network, which consists of separate systems, including the main river and its tributaries. Usually the main river is longer, full-flowing and occupies an axial position in the river system. As a rule, it has an older geological age than the tributaries. Sometimes the opposite happens. For example, the Volga carries less water than the Kama, but is considered the main river, since its basin was historically inhabited earlier than the Kama. Some tributaries are longer than the main river (the Missouri is longer than the Mississippi, the Irtysh is longer than the Ob).

The tributaries of the main river are divided into tributaries of the first, second and subsequent orders.

The river network consists of river systems. The river system includes the main river and its tributaries. A river system is characterized by the degree of length of all its rivers, the area of ​​its basin, and the sinuosity and density of the river network. Extended p. rivers can be measured on a large-scale map using a compass, curvimeter, less accurately by applying a wet thread.

A river basin is understood as the area from which it receives food. The basin area can be determined from large-scale maps using a palette. The basins of the various rivers are separated by watersheds. They often pass through hills, in some cases - through flat wetlands.

Tortuosity is the ratio of the length of a river to a straight line, coi 1 » dividing the source and mouth or between two separate navels.

The density of the river network is the ratio of the total length of all rivers of a given main river to the basin area l (km/km2). It depends on the relief, climate, rocks that form the area where it flows. In places where there is a greater amount of precipitation and evaporation is negligible, the river network is more dense, for example, in the north-west of the country. In the mountains, the density of the river network is greater than in the plains. Gak, on the northern slopes of the Caucasus Range, it is 0.49 km / km 2, i.e., 490 mm of river length falls on 1 km 2 of the area, and in Ciscaucasia - 0.05 km / km 2, i.e. per 1 km 2 of the area accounts for 50 m of the length of the rivers.

The rivers are fed by groundwater, which comes to the surface in the form of springs (springs), as well as by precipitation in the form of rain and snow. Rainwater that falls on the surface partially evaporates, part of it seeps into the depths of the earth, and also flows down the river. Fallen snow melts in spring. Melt water flows down the slope into depressions and eventually ends up in rivers. Thus, groundwater, rains in summer and snowmelt in spring are a constant source of river nutrition. Is the mountainous areas of the river fed by waters from melting glaciers.

The level of water in the rivers depends on the nature of food. The largest rise in water in the territory of our country is observed in spring, during the melting of snow. Rivers overflow their banks, flooding huge spaces, often causing great harm. national economy. During spring floods, more than half of the annual volume of water flows down. In places where more precipitation falls in summer, rivers have a summer flood. For example, Amur has two floods: less powerful - in spring and more powerful - at the end of summer, during monsoon rains. Rivers< "редней Азии и Кавказа имеют тоже летний разлив, но при­чина его в том, что летом усиленно тают снега и ледники в го­рах. Летний разлив имеют также реки Крайнего Севера, так |.мк там тают снега летом.

Observations of the level of the rivers made it possible to single out periods of high (and low) water.

High water - an annual recurring rise in water in the same season. In the spring, when snow melts for 2-3 months, a high water level is maintained in the rivers. At this time, rivers flood.

Floods - short-term non-periodic rises in the rivers - 11.1. For example, during heavy prolonged rains, some rivers of the East European Plain overflow their banks, flooding vast areas. Floods occur on i rivers during hot weather, when snow and glaciers melt intensively.

The height of the rise of water during floods is different (in mountainous countries - higher, on plains - lower) and depends on iptsn-; (41) and the features of snowmelt, rainfall, forest cover of territory-1; | 1pi, the width of the floodplain and the nature of ice drift. Thus, on large Siberian rivers, during the formation of ice jams, the rise<>-: dy reaches 20 m.

Low water is the lowest water level in a river. At this time, the river is fed mainly by groundwater. In the central zone of our country, low water is observed at the end of summer, when water evaporates strongly and seeps into the ground, and also at the end of winter, when there is no surface nutrition.

All rivers of the globe can be divided into the following types according to their feeding methods: rivers of rain feeding (rivers of the equatorial, tropical and subtropical belts - Amazon, Congo, Nile, Yangtze, etc.); rivers fed by melting snow and glaciers (rivers of mountainous regions and the Far North - Amu Darya, Syr Darya, Kuban, Yukon); underground feeding rivers (rivers of mountain slopes in the arid zone - small rivers of the northern slope of the Tien Shan); rivers of mixed nutrition (rivers of the temperate zone with a pronounced stable snow cover - the Volga, Dnieper, Ob, Yenisei, etc.).

River work. The river is constantly producing work that manifests itself in erosion, transport and accumulation of material.

Erosion is understood as the destruction of rocks. They distinguish deep erosion, aimed at deepening the channel, lateral erosion, aimed at destroying the banks. On the rivers you can see bends, which are called meanders. transports and deposits.Deposition begins when the current slows down.Larger material (stones, pebbles, coarse sand) is deposited first, then finer sand and silt.

In the mouths of the rivers, the brought material accumulates. Islands and shoals are formed with channels between them. Such formations are called deltas.

On the map you can see a large number of rivers that form deltas. But there are rivers that don't have them. They flow into the sea in the form of an expanding wedge. I call such mouths estuaries, for example, near the Thames, the Rhine.

Why does the river form a delta in some cases and not in others? It depends on the stability of the bottom of the sea into which the river flows. Where it is constantly lowered as a result of the bow movements of the earth's crust, the delta does not form. In places where the bottom of the sea rises, deltas form. Rivers may not have deltas even if there is a strong current in the sea in the area where the river enters. It carries river nanoses far out to sea. For this reason, for example, the Cong River (Zaire) does not have a delta.

As a result of the work of the river, river valleys are formed. They are elongated winding depressions with a certain slope, along the bottom of which a river flows.

River valleys differ in the following elements: floodplain channel, terraces, slopes. Under the channel understand the lower part of the valley through which the river flows. The channel has two banks: right and left. One coast is gentle, the other is steep. The bed of a flat river has a winding shape. Therefore, in addition to the force of gravity and friction, the nature of the movement of the flow is affected by the centrifugal force that occurs at the turns of the river, as well as the deflecting force of the Earth's rotation. These forces cause transverse circular motion. Under the action of centrifugal force at the turn, the flow is pressed against the concave bank, and the jets of water, hitting, destroy it. There is a change in the direction of the flow. Along the bottom, the stream is directed towards the opposite, gently sloping shore. The deflecting force of the Earth's rotation causes the flow to press against the right bank (in the northern hemisphere). It collapses, the riverbed moves. So, during the reign of Ivan the Terrible, the Kazan Kremlin was located on the banks of the Volga, and by now the river has moved 7 km away from it.

The process of formation of meanders (meander) is continuous. However, for a certain time in this area, it may stop. The fact is that the river, increasing the sinuosity, reduces the slope, and consequently, the average speed. There comes a moment when the speed even on roundings becomes insufficient for further blurring. In addition, meanders can approach each other at such a distance that they connect. Then the river will straighten out. Former meanders become oxbow lakes, and then lakes.

In lowland rivers, the alternation of reaches and rifts can be distinguished as a common feature. Plesy - the deepest sections of the river with a slow current. They are formed on its bends. Rifts - small parts of the river with a fast current. They form in flat areas. Gradually, stretches and rifts move along the river.

The river constantly deepens the channel, but deep erosion cannot go below the water level at the confluence of the river into another river, lake, sea. This level is called the basis of erosion. The final basis of erosion for all rivers is the level of the World Ocean. Changes in the level of the ocean, sea, lake are reflected in the work of rivers. When the erosion base decreases, the river strongly erodes, deepens the channel; with an increase, this process slows down, intensive deposition takes place.

Floodplain - part of the valley, flooded with spring waters. Its surface is uneven: extensive elongated depressions alternate with small sandy elevations. The highest areas are located along the coast - coastal shafts. They are usually covered with vegetation. According to the nature of the relief, the floodplains are divided into three parts: near the riverbed - the highest; central - flat with fertile alluvial soils, occupied by meadows and vegetable gardens; terraced low, often swampy. Terraces are flat areas stretching along the slopes in the form of steps. On large rivers, several terraces are observed, they are counted from the floodplain (first, second, etc.). The Volga has four terraces, and on the rivers Eastern Siberia- up to 20. Slopes limit the valley from the sides. In some cases they are steep, in others they are gentle. Often one slope is steep, the other is gentle. For example, the right slope of the Volga is steep, the left slope is gentle.

The river valley is created by the river. However, other factors also influence the formation of valleys. These include tectonic processes that determine the direction and sometimes the shape of the valley, rocks, their composition, the location of layers, weathering, washing away of loose rocks by atmospheric waters, slipping of soils, etc.

Young rivers in the longitudinal profile have areas where rapids are observed (places with a fast flow and stones come to the surface of the water), waterfalls (areas where water falls from steep ledges). Waterfalls are found on many mountain rivers and flat ones, where solid rocks come to the surface.

The largest waterfall in the world is Victoria Falls on the Zambezi River. Water falls from a height of 120 m with a width of 1800 m. The noise of falling water can be heard for tens of kilometers, and the waterfall is always shrouded in a cloud of spray.

The waters of Niagara Falls (North America) fall from a height of 51 m, the width of the stream is 1237 m.

Many mountain waterfalls are even higher. The highest of them is Angel on the Orinoco River. Its water falls from a height of 1054 m.

Consumption and flow of water in rivers. During construction settlements it is very important to know how much water flows in the river, whether it can provide the population and enterprises with water. For this purpose, the flow of water in the river is determined. The flow of water in a river is understood as the amount of water (m 3) passing through the living section of the river in 1 s: P^=S-V, where s is the area of ​​\u200b\u200bthe xp section, m, Y is the average speed, m / s.

To determine the water flow in a small river, a temporary hydrometric nori is built on its straight section, consisting of four sections: starting, upper, main and lower (Fig. 30).

From the above formula, it can be seen that to determine the flow of water V river, you need to measure the speed and calculate the area of ​​\u200b\u200bthe living section of the river.

The speed of the current is determined by devices called hydrometric vanes. The speed of the current of a small river can be determined using floats. Ig is usually used by wooden floats with a diameter of 15-20 cm and a length of 8-10 cm. A flag with a number is placed on the float.

Since the speed is different in different parts of the channel, 3-5 floats are used. The float is launched at the launch site and the time of its passage through the upper and lower sites is recorded. Measure the distance between them in advance. And if the distance and time of passage of the float between the upper and lower sections is known, you can calculate the speed. Floats are allowed at different distances from the coast: near the right bank, in the middle (2-3 floats), near the left bank. It has been established that the speed of the river flow is approximately 80% of the average speed of wooden floats.

On the main alignment, the area of ​​\u200b\u200bthe living section is determined. To do this, measure the depth of the river after a certain number of meters. According to the data, a drawing of the section of the riverbed (living section) is built, the area of ​​individual figures is calculated, and then it is summarized. You can calculate the area of ​​​​the living section in another way. First, determine the average depth of the channel along the alignment and multiply the resulting value by the width of the channel.

For example, the speed of the river flow is 1 m / s, the area of ​​\u200b\u200bliving section is 10 m 2. This means that the water flow in the river is 10 m 3 / s.

The flow of water in a river over a long period is called river runoff. It is usually determined from long-term data and is expressed in km 3 /year.

The flow shows the high water content of the river. Here are some indicators of the average flow for the main rivers of the Earth.

The flow depends on the area of ​​the river basin and climatic conditions. A large amount of precipitation with little evaporation contributes to an increase in runoff. In addition, the runoff depends on the rocks that make up the given territory and the terrain.

The abundance of water in the Amazon River (see Table 11) is explained by the huge area of ​​the basin (about 7 million km 2). This is the most Syulsha river basin. More than 300 mm of precipitation per year falls on its area. The Amazon has 17 tributaries of the first order, each of them gives almost as much water as the Volga. The most abundant river in the Soviet Union is the Yenisei, its annual flow is 548 km 3 / year.

Grandiose work has been carried out in our country to regulate river flow. Almost all major rivers (Volga, Dnieper, Angara) have built reservoirs that contain spring and flood waters, which makes it possible to use it economically throughout the year. The water of these rivers sets in motion turbines that generate electricity, goes to the needs of the population and irrigation of fields.

Lakes and swamps

About 2% of all land is occupied by lakes. Lakes are significant land depressions filled with water and not connected to the sea. On the territory of our country are located the largest lake in the world - the Caspian and the deepest - Baikal. There are many lakes in the northwest of the country, especially in Karelia.

Since ancient times, man has used lakes for water supply; they serve as communication routes, a place for fishing. Many lakes contain valuable raw materials: salts, iron ores, sapropel. They are objects for tourism.

According to the nature of the runoff, the lakes are subdivided into flowing, waste and non-drainage. Numerous rivers flow into flowing lakes and flow out of them. This type includes the Ladoga, Onega and lakes of Finland.

Waste lakes receive a large number of rivers, but one river flows out of them. Lake Sevan in Armenia can be attributed to this type.

In the arid regions there are lakes with no outflow - Caspian, Aral, Balkhash. Numerous tundra lakes also belong to this type.

In the process of development, drainless lakes can become wastewater if the water supply exceeds evaporation.

Lake basins are extremely diverse in origin. There are basins that have arisen as a result of the manifestation of the internal forces of the Earth (endogenous). This is the majority of large lakes in the world. Small lakes are generated by the activity of external forces (exogenous). Endogenous basins include tectonic and volcanic. Tectonic basins are subsided sections of the earth's crust. Subsidence can occur as a result of layer deflection or fault faults along fractures. Thus, the largest lakes Caspian, Aral (trough of the earth's layers), Baikal, Tanganyika, Nyasa, Upper, Huron, Michigan (fault) were formed.

Basins of volcanic origin are oboe volcanic craters or valleys covered by lava flows. There are similar basins in Kamchatka, for example, Kronotskoye Lake. Lake basins of exogenous origin are diverse. In the river valleys there are often lakes that have an oblong shape. They arose on the site of the former r "settled rivers.

Many lakes were formed during the Ice Age. Continental ice plowed out huge hollows during its movement. They filled with water. Such lakes are found in Finland, Canada, in the north-west of our country. Many lakes are elongated in the direction of movement of glaciers.

In areas composed of limestone, dolomite and gypsum, there are basins of failed origin, they are called karst. Many of them are very deep.

Basins can also occur as a result of blowing. Such basins are very shallow, and the lakes disappear in them. They are found in coastal dry areas.

Lake basins, which arose as a result of uneven thawing of permafrost, have a special type. These are lakes of thermokarst origin (most of the tundra lakes).

Dam lakes can appear in the mountains as a result of strong earthquakes. So, in 1911 in the Pamirs literally i Lake Sarez appeared in the eyes of people: part of the mountain range was thrown into the river valley as a result of the earthquake, a dam with a height of more than 500 m was formed.

A lot of hollows created by man - these are artificial reservoirs.

In our country, the flow of most large rivers is regulated (Volga, Dnieper, Angara, Yenisei), dense ones are built on them, large reservoirs are created.

Many lake basins are of mixed origin. For example, Lakes Ladoga and Onega are tectonic, but their basins have changed their appearance under the influence of glaciers, rivers, and seas. The Caspian Sea-Lake is the remainder of a large sea basin, which was once connected through the Kumo-Manych depression with the Azov and Black Seas.

Lake nutrition. Lakes are fed by groundwater, atmospheric precipitation and rivers flowing into them. Part of the water from the lakes is carried into the rivers, evaporates from the surface, goes to the underground runoff. Depending on the ratio of the incoming and outgoing part, the water level fluctuates, which leads to a change in the areas of lakes. For example, Lake Chad in the dry season has an area of ​​12000 km2, and in the rainy season it increases to 26000 km2. Over the past hundred years, a decrease in the water level of the Caspian Lake has been noted. As a result, the area of ​​lakes has decreased by 30 thousand km2, many bays have disappeared, and the islands have turned into peninsulas. Now the level of the Caspian lake is 28 m below the ocean level.

The change in the water level in the lakes is associated with climatic conditions: a decrease in the amount of precipitation in the lake basin, as well as its evaporation from the surface. The water level in the lake can also change as a result of tectonic movements.

Water level fluctuations in flowing lakes are insignificant and do not reach one meter (Baikal, Onega, Ladoga). According to the amount of substance dissolved in water, lakes are divided into fresh, brackish and salty. Fresh lakes have dissolved salts less than 1%o. Brackish lakes are those where the salinity is more than 1% 0, and saline - over 24.7% 0 (with such salinity, the freezing point of water coincides with the temperature of the highest density of water).

Flowing and wastewater lakes are usually fresh, since the inflow of fresh water is greater than the outflow. Endorheic lakes are predominantly brackish or saline. In these lakes, the inflow of water is less than the outflow, so the salinity increases. Salt lakes are located in the steppe and desert zones (Elton, Baskunchak, Dead, Big Salt and many others). But some are distinguished by a high content of soda (Na2S04) - these are soda lakes (for example, Lake Van and some lakes in the south of Western Siberia); others are rich along with chlorides and sulfides of borax (Na2B 4 0 7 - YPtsO) such lakes are found in Tibet, in California.

Stages of development of lakes. Lakes are short-lived formations on the Earth's surface. They separate and record the bridge oi surrounding conditions. Rivers, temporary water streams carry from the slopes to the lakes a huge amount of inorganic and organic substances that are deposited on the bottom. Vegetation appears, the remains of which also accumulate, filling the lake basins. As a result of this, the lakes become shallow, and swamps form in their place.

The overgrowth of lakes and their transformation into swamps occurs gradually. The shallow lake begins to overgrow from the banks (Fig. 31). Sedges, arrowheads, water buckwheat, water buttercups, etc. grow to a depth of 1 m. Deeper, up to 2-3 m, reeds, reeds, horsetails settle; even deeper - water lilies, ponds, in which only leaves and flowers float on the surface, and all other organs of the plant are completely immersed in water. The deep part of the lake is occupied by various kinds of algae. Plants, dying, fall to the bottom, and powerful layers of sapropel are formed there. "The lake continues to shallow, overgrow and turns into a swamp. Mosses and lichens appear on the surface. Under a layer of mosses, the dead remains of vegetation without access to oxygen turn into peat. In the forest belt it is very lakes are often overgrown from windward shores.

There are several stages in the development of lakes.

1. The stage of youth, when the original bottom topography remains unchanged.

2. The stage of maturity, when the coastal shallows are developed; alluvial cones of the rivers are well expressed at their confluence, but the unevenness of the bottom is still preserved.

3. The stage of old age, when sediments have leveled the bottom of the lake. In fresh lakes, vegetation surrounds the shores in a semicircle.

4. The stage of complete overgrowth, when the lake becomes shallow, vegetation covers most of the water surface, the lake turns into a swamp.

The distribution of lakes is subject to the laws of zoning. In the Soviet Union, the densest lake network is also observed in the forest belt, in areas of ancient glaciation: on the Kola Peninsula, in Karelia. Here the lakes are fresh, mostly flowing and rapidly overgrowing. To the south, in the forest-steppe and steppe zones, the number of lakes decreases sharply. Drainless salt lakes predominate in the desert zone; they often dry up, turning into salt marshes. Tectonic lakes abound in the wind in all belts. They have great depths, so their change is slow, hardly noticeable to a person.

Bblota - land areas, excessively moistened, covered with moisture-loving vegetation, having a layer of peat of at least 30 cm.

Bogs, as mentioned, can be formed when lakes are overgrown, as well as under conditions of constant waterlogging of soils due to a large amount of precipitation, low evaporation, and slow runoff. Waterlogging leads to a deterioration in the oxygen and mineral nutrition of plants. The lack of oxygen hinders the process of decomposition of plant residues, from which peat is formed. Soils are depleted in nutrients, forest and grassy vegetation is starving, moss appears in the lower tier, which is less demanding on nutritional conditions. Mosses absorb atmospheric moisture and retain a large amount of water. Therefore, the access of air to the soil is difficult, peat begins to accumulate. Trees die due to lack of oxygen for root systems. The death of trees increases waterlogging of soils. Bogging in the forest belt occurs during deforestation. Favorable conditions for the formation of swamps in the tundra, where permafrost does not allow groundwater to penetrate deep and they remain on the surface.

According to the conditions of nutrition and location, the swamps are divided into lowland and upland. Lowland swamps are fed by atmospheric precipitation, surface and underground waters. Groundwater is rich in minerals. This causes rich vegetation in low-lying swamps (alder, willow, birch, sedge, horsetail, reed, and rosemary from shrubs). Lowland swamps are widespread b-.yen-strip on the floodplains of large rivers.

Under certain conditions, lowland bogs can turn into raised ones. As peat grows, the amount of minerals decreases, and plants demanding mineral nutrition give way to less demanding ones. Usually these plants appear in the center of the swamp (sphagnum mosses). They secrete organic acids that slow down the decay of plant matter. There are rises from h > |) fa. Water flowing into the swamp can no longer fall into the titre, where sphagnum mosses spread, feeding on atmospheric moisture. Such swamps are called raised. Mounted oolots arise on poorly dissected watersheds.

Swamps occupy vast areas. Approximately 1/10 of the territory of our country is covered with swamps. Extensive areas of swamps in Polesie (Belarus), Pskov, Novgorod regions, Meshchera and Western Siberia. Many swamps i * tundra.

Peat is mined in the swamps, which is used for heating and electricity production, and is also used as ii.m-mist fertilizer. In our country, the planned drainage of swamps is carried out, which, as a result, turn into fertile agricultural land.

The groundwater

Groundwater refers to the waters below the surface of the Earth in liquid, solid and gaseous states. They accumulate in pores, cracks, voids of rocks.

Groundwater was formed as a result of seepage of water that fell to the surface of the Earth, condensation of water vapor that entered through the pores from the atmosphere, and also as a result of the formation of water vapor during cooling of magma at a depth and their condensation in the upper layers of the earth's crust. Of decisive importance in the formation of groundwater are the processes of seepage of water from the surface of the Earth. In some zones, for example, in sandy deserts, the main role is played by water coming from the atmosphere in the form of water vapor.

Water that is under the influence of gravity is called)! gravitational. Its movement is due to the slope of the waterproof layer.

Water held by molecular forces is called film water. Water molecules that come into direct contact with rock grains form hygroscopic water. Film and hygroscopic water can be removed from the rock only by calcination. Therefore plants this water can not! use.

The root systems of plants assimilate capillary water (located in the capillaries of the soil) and gravitational.

The rate of movement of groundwater is negligible and depends on the structure of the rocks. There are fine-grained strata (clays, loams), granular (sands), fissured (" limestones "). 1-0.3 mm per day.

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

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

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

Transfer and sorting of destruction products brought from land;

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

Physico- Chemical properties waters of the seas and oceans

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

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

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

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

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

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

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

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

Relief elements.

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

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

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

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

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

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

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

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

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

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

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

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

mid-ocean ridges

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

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

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

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

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

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

Optical properties

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

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

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

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

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

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

Acoustic properties

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

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

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

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

Electrical Properties

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

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

Radioactive properties

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

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

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

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

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

The chemical composition of ocean waters

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

Elemental composition Salt elemental composition

sea ​​water sea water

O 85.8% Cl 55.3%

H 10.7% Na 30.6%

Cl 2.1% SO 4 7.7%

Na 1.15% Mg 3.7%

Mg 0.14% Ca 1.2%

S 0.09% K 1.1%

Ca 0.05% Br 0.2%

K 0.04% CO2 0.2%

The rest is less than 0.001%.

The salt composition of sea water is dominated by:

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

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

Carbonates 0.56%

Bromates 0.3%.

Gas composition of sea water

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

Oxygen enters the water in two ways:

From the atmosphere

Due to the photosynthesis of phytoplankton (green plants)

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

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

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

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

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

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

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

The temperature of the waters of the oceans

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

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

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

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

Thickness - from a few cm to tens of meters,

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

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

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

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

Density of sea water

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

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

sea ​​water pressure

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

P \u003d H ּρ / 100,

P - pressure in MPa,

H is the depth for which the calculation is made,

ρ is the density of sea water.

Under the pressure of the overlying layers, the specific volume of sea water decreases, i.e. it is compressed, but this value is insignificant: at S \u003d 35‰ and t \u003d 15 ° C, it is 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 climb 30 meters.

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

The oceans and its parts

world ocean 1- a single continuous water shell of the Earth, surrounding the continents and islands. Of the 510 million km 2 of the earth's area, it accounts for 361.3 million km 2 (70.8%), so that we, in essence, live on islands 2 . The southern hemisphere is more oceanic (81%) than the northern (61%). The uneven distribution of ocean and land waters on our planet is one of the most important factors in the formation of the nature of the globe.

The volume of the World Ocean is more than 1340 million km 3, and if we take into account the water contained in the silts of the ocean floor (about 10% of the waters of the Ocean), then the total volume of the oceanosphere is almost 1.5 billion km 3. The average depth of the Ocean is 3710 m.

1 The word "ocean" (Greek. o/geapos), meaning "ve
lyrical river flowing around the whole Earth "came to us from
ancient times. The term "World Ocean" was proposed in
1917 by the Russian oceanologist Yu. M. Shokalsky.

2 With the help of artificial earth satellites,
updated that the actual area of ​​the World Ocean
due to uneven ocean surface by 0.14%
more projection, which is usually accepted for races
even, and is 361.8 million km 2.

The world ocean is not only water, it is an integral natural formation, a kind of geographical object on a planetary scale. From the standpoint of system research, it is considered as an open dynamic self-regulating system that exchanges matter and energy with all other spheres of the Earth.

The United World Ocean is subdivided into separate oceans. Ocean - a vast part of the World Ocean, isolated by continents, having a peculiar configuration of the coastline, certain geological structure, bottom topography and bottom sediments, independent systems of atmospheric circulation and currents, specific hydrological characteristics and natural resources. Despite the conventionality of borders and the free exchange of water masses, each ocean is unique. But the specificity of the oceans is manifested against the background of general planetary processes and features inherent in the World Ocean as a whole.

In modern world oceanological literature, the concept of dividing the World Ocean into four oceans has developed: Quiet

Lyubushkina

(area 178.68 million km 2, maximum depth in the Mariana Trench 11022 m), Atlantic(91.66 million km 2, depth in the Puerto Rico trench 8742 m), Indian(76.17 million km 2, depth in the Yavan Trench 7729 m), Arctic(14.75 million km 2, depth in the Nansen Basin 5527 m). The boundaries of the oceans are drawn along the continents, islands, and in the expanses of water either along underwater uplifts that impede water exchange, or even conventionally along meridians and parallels. The border between the Pacific and Atlantic Oceans is drawn along the meridian of Cape Horn (Tierra del Fuego), between the Atlantic and Indian Oceans - along the meridian of Cape Agulhas (South Africa), the Indian and Pacific Oceans - along the meridian of Cape South (Tasmania Island) and along the western shores of the peninsula Malacca, Greater and Lesser Sunda Islands. The border of the Arctic Ocean with the Atlantic passes partly along the underwater rapids and islands: from the Sogne Fjord Bay (Scandinavian Peninsula) through the Faroe Islands and Iceland, then along the southern slope of the elevation of the bottom of the Danish Strait to Cape Brewster (Greenland Island); then along the southern slope of the elevation in the Davis Strait to the Labrador Peninsula. The border between the Pacific and Arctic Oceans runs along the Bering Strait from Cape Dezhnev in Chukotka to Cape Prince of Wales in Alaska.

Rice. 78. Southern Ocean

In 1996, the Federal Service for Geodesy and Cartography of Russia decided to highlight on maps published in Russia -

Russian Federation, Southern Ocean. The northern boundary of the Southern Ocean is defined along the long-term average position of the subtropical front (approximately along 40° S with deviations from 37° to 48°) (Fig. 78).

All oceans have seas. Sea - a part of the Ocean more or less isolated by islands, peninsulas and underwater heights. The exception is the unique Sargasso "sea without shores", located in the anticyclonic ring of the currents of the North Atlantic.

Due to some isolation and the great influence of land and other local conditions, as well as slow water exchange, the seas differ from the open part of the Ocean in their hydrological regime and other natural features.

Seas are classified according to different criteria.

By location, the seas are divided into marginal, inland and interisland. Outlying The seas are located on the underwater continuation of the continents and are limited on the one hand by land, on the other - by islands and underwater hills. Their connection with the Ocean is rather close (Barents, Bering, Tasmanovo, etc.). Inland (Mediterranean) the seas protrude far into the land, are connected to the oceans by narrow straits with rapids and sharply differ from them in hydrological regime. They are, in turn, subdivided into inland(Baltic, Black, etc.) and intercontinental(Mediterranean, Red, etc.). to interisland seas surrounded by a more or less dense ring of islands and underwater rapids include the Yavan, Philippine, and others. Their regime is determined by the degree of water exchange with the ocean.

In general, the seas make up about 10% of the area of ​​the World Ocean. The largest seas are the Philippine - 5726 thousand km 2, the Arabian - 4832 thousand km 2, the Coral - 4068 thousand km 2.

According to the origin of the basins, two main types of seas are distinguished: continental and oceanic. They, as a rule, also differ in the shape of the basins and depth.

Continental (epicontinental) The seas are located within the underwater margin of the continent with the continental crust, mainly on the shelf. They arise when the Ocean advances on land due either to fluctuations in the earth's crust, or due to an increase in water in the Ocean after the melting of ice sheets. Most marginal seas and many inland seas

are worn to this type. The marginal seas have an asymmetric shape: the slope is gentle on the land side, and steep on the ocean side (islands). Their depths are relatively small and grow towards the ocean.

Oceanic (geosynclinal) seas are formed as a result of faults in the earth's crust and the sinking of land. These include, first of all, the seas of transitional zones from the continents to the ocean bed and the Mediterranean intercontinental seas. They have basins symmetrical in shape, the depths increase towards the center up to 2000 m or more. Usually they cut through the continental base, and they are currently characterized by tectonic activity (volcanoes, earthquakes). All interisland seas are also located in tectonically active zones of the Earth, and the islands surrounding them are, in fact, the tops of seamounts, often volcanoes.

Along with these two main types of seas, there are seas that have features of both types, for example, the Bering Sea.

Seas, unlike oceans, are regional complex natural objects, because their main features are formed under the influence of local factors.

Coastline- the border of land and sea is usually uneven, with bends in the form of bays and peninsulas. Along it, islands are common, separated from the continents and from each other by straits.

gulf The part of the ocean that extends deep into the land. Bays are less isolated from adjacent oceans than seas. Therefore, their regime is more similar to the water areas to which they belong. Bays are classified into different types depending on a number of factors. According to their origin, for example, fjords- narrow, long, deep bays with steep banks, protruding into mountainous land, formed at the site of tectonic faults, subsequently processed by a glacier and flooded by the sea (Sognefjord, etc.); estuaries- small bays on the site of the mouth parts of the rivers flooded by the sea (Dneprovsky estuary, etc.); lagoons- bays along the coast, separated from the sea by spits (Curonian Lagoon, etc.). There is a division of bays by size (the largest is Bengal - 2191 thousand km 2), by depth (onge - 4519 m), by the shape of the coastline: rounded (Biscay), long and narrow (California).

Historically, essentially the same type of water areas are sometimes called bays, sometimes seas, although in many ways they are similar: for example, the Bay of Bengal,

but the Arabian Sea, Gulf of Mexico, but the Caribbean Sea, the Persian Gulf, but the Red Sea, etc. These discrepancies are explained by the fact that the names were given to them at different times without scientific justification and, according to tradition, have survived to this day.

strait- a relatively narrow part of the ocean or sea that separates two areas of land and connects two adjacent bodies of water. Straits often tend to raise the bottom - an underwater threshold. Straits are also divided into different types according to a number of characteristics. According to morphology, they are distinguished narrow And wide straits (the widest is the Drake Passage - 1120 km), short And long(the longest - Mozambique - 1760 km), small And deep(the deepest is also the Drake Strait - 5249 m). According to the direction in the straits of water, they are divided into flow, in which the current, like in a river, is directed in one direction, for example, the Strait of Florida with the Florida current, and on exchange, in which currents are observed in opposite directions: either near different coasts (in the Davis Strait, the warm West Greenland Current is directed to the north, and the cold Labrador Current is directed to the south), or in opposite directions at two different levels (in the Bosphorus Strait, the surface current follows from the Black seas to Marmara, and the deep - vice versa).

Peninsula A piece of land that extends into the ocean or sea and is surrounded on three sides by water. The largest peninsula is Arabian (2732 thousand km 2). Allocate indigenous and accumulative peninsulas. Indigenous subdivided into detached, being a continuation of the mainland in geological terms (Kola Peninsula), and affiliated- independent parts of the land, geologically not connected with the mainland, but joined to it (Hindostan peninsula). accumulative peninsulas are attached to the shore due to the bridge of alluvial land as a result of wave activity (for example, the Buzachi peninsula on the Caspian Sea).

Island- a small piece of land compared to the continents, surrounded on all sides by water. There are single islands (the largest is Greenland - 2176 thousand km 2) and clusters of islands - archipelagos(Canadian archipelago, Severnaya Zemlya). By origin, the islands are divided into two main groups: continental and oceanic. Mainland- those that separated from the continents; they are usually large and located on the underwater margin of the continents (Great Britain, the New Siberian Islands, etc.). oceanic(self-

I 11111 300 200 100

ocean level

Rice. 79. Change in the level of the World Ocean and its possible limits over the past 350 thousand years (according to R Fairbridge)

standing), in turn, are divided into volcanic and coral (organogenic). Volcanic islands- the result of the eruption of underwater volcanoes, the tops of which were above the level of the Ocean. They either form a chain of islands along deep-sea trenches in the transitional zone of the ocean (Kuril), or are outlets to the surface of mid-ocean ridges (Iceland Island is part of such an underwater ridge with a fault along the axis, active volcanism and intense hydrothermal activity). Often these are arched blocky underwater ridges on the ocean floor, the crests of which are crowned with volcanic mountains (Hawaiian Islands). A huge number of single islands of volcanic origin are scattered along the bottom of the oceans, especially the Pacific. coral islands characteristic of the hot zone, especially a lot of them in the Pacific and Indian Oceans. Coral structures - atolls have the shape of a ring or a horseshoe with a diameter of up to several tens of kilometers around a shallow lagoon. The basis for them are usually flat-topped underwater volcanoes - guyots. Sometimes atolls form garlands along the coast - barrier reefs, for example, the Great Barrier Reef, which stretches along the east coast of Australia for 2000 km.

Level surface of the ocean - free water surface of the oceans and seas,

close to geoid shape. In our country, for the initial level - the standard from which the absolute height of the land surface and the depth of the seas are measured, is taken the average long-term level of the Baltic Sea near Kronstadt (Baltic system of heights).

The level of the World Ocean is subject to various kinds of fluctuations, both periodic and non-periodic. TO periodic fluctuations include, for example, daily fluctuations due to tides, annual fluctuations due to temperature, precipitation, winds. Non-periodic fluctuations arise due to the passage of tropical cyclones, tsunamis, sea quakes, etc. The oscillation periods can be short(high-low tide after 6 hours 12.5 minutes) and long, age-old(hundreds of years). For example, many buildings in Scandinavia, once erected on the seashore, are now far from it. And in Holland, Venice, the land is sinking and the sea is advancing.

century changes can be caused by various reasons: changes in the volume of water in the ocean (hydrocratic, or ev-static, fluctuations) or changes in the capacitance of the ocean (geocratic, or tectonic, fluctuations). Geocratic fluctuations are caused by tectonic disturbances of the ocean floor, due to which the volume of the World Ocean changes.

This has happened repeatedly over geologic time, causing transgressions(offensive) and regression(retreat) of the sea.

-10000 -8000 -6000 -4000 -2000 N, m - ocean levels (0 - current level)

Interconnected theocratic and hydrocratic changes occurred repeatedly during the Pleistocene. During cooling, a huge mass of water in the form of ice was conserved on land and the level of the Ocean dropped by 100-120 m.

During interglacial warming, as a result of ice melting, water entered the Ocean and its level increased (Fig. 79). The nature of the ocean level fluctuations in the Quaternary was influenced to a certain extent by glacioisostatic compensations. Figure 80 shows the directed rise in the level of the World Ocean after the end of the Quaternary glaciations in the Holocene (about 10 thousand years ago). It is clear that he achieved his current situation approximately in the middle of the Atlantic period of the Holocene about 6 thousand years ago and since then has been experiencing periodic fluctuations around zero

Rice. 80. Changes in the level of the World Ocean and its possible deviations in the Holocene (according to R. K. Klige and others)

labels. At the same time, the increase in the level of the World Ocean over the past 100 years by 16 cm is associated with global anthropogenic climate warming on Earth, which caused the melting of glaciers and thermal expansion of water in the Ocean (Fig. 81). Calculations indicate a further increase in the level of the Ocean by about 20-30 cm by the middle of the 21st century, although extreme estimates differ significantly: from 5-7 cm to 140 cm. The overall picture of the change in the level of the Ocean is very complex and is usually calculated for certain observation points.

Rice. 81. Modern changes level of the World Ocean (according to R. K. Klige and others)

Basic physical and chemical properties of ocean (sea) water

ocean water- a universal homogeneous ionized solution, which includes all chemical elements. The solution contains solid mineral substances (salts) and gases, as well as suspensions of organic and inorganic origin.

Salinity of sea water. By weight, dissolved salts make up only 3.5%, but they give the water a bitter-salty taste and other properties. The composition of sea water and its content different groups salts are visible from table 8. Sea water differs sharply in composition from river water, because chlorides predominate in it. It is interesting to note that the composition of salts in blood plasma is close to the composition of salts in sea water, in which, according to many scientists, life originated.

Table 8

(in% of the total mass of salts) (according to L.K. Davydov and others)

Salinity- the amount of salts in grams in 1 kg of sea water. The average salinity of the Ocean is 35% 0 . Of the 35 grams of salts in sea water, most of all is table salt (about 27 g), so it is salty. Magnesium salts give it a bitter taste. Lines on a map connecting points of equal salinity are called isohalines.

Ocean water was formed from hot saline solutions of the earth's interior and gases, so that salinity her original. The composition of sea water is similar to that juvenile waters, i.e., waters and gases released during volcanic eruptions from magma and for the first time entering the water cycle on Earth. Ga-

ses released from modern volcanoes consist mainly of water vapor (about 75%), carbon dioxide (up to 20%), chlorine (7%), methane (3%), sulfur and other components.

The initial composition of salts of sea water and its salinity were somewhat different. The changes that it has undergone during the evolution of the Earth were caused primarily by the appearance of life, especially the mechanism of photosynthesis and the production of oxygen associated with it. Some changes, apparently, were introduced by river waters, which at first leached rocks on land and delivered easily soluble salts to the Ocean, and later - mainly carbonates. However, living organisms, especially animals, consumed huge amounts of first silicon and then calcium to form their internal skeletons and shells. After dying, they sank to the bottom and dropped out of the mineral cycle without increasing the content of carbonates in sea water.

In the history of the development of the World Ocean, there were periods when salinity fluctuated in the direction of decreasing or increasing. This happened both as a result of geological reasons, because tectonic activation of the interior and volcanism influenced the activity of magma degassing, and due to climatic changes. In severe ice ages, when large masses of fresh water were conserved on land in the form of glaciers, salinity increased. With warming in the interglacial epochs, when melted glacial waters entered the Ocean, it decreased. During arid epochs, salinity increased, while during wet epochs, it decreased.

In the distribution of salinity of surface waters to a depth of approximately 200 m, one can trace zoning, which is connected with the balance (inflow and outflow) of fresh water, and above all with the amount of precipitation and evaporation. Reduce the salinity of sea water river water and icebergs.

In equatorial and subequatorial latitudes, where more precipitation falls than water is spent on evaporation (K of moisture > 1), and river runoff is large, salinity is slightly less than 35% 0. In tropical and subtropical latitudes, due to the negative freshwater balance (there is little precipitation and high evaporation), the salinity is 37% 0. In temperate latitudes, salinity is close to 35%. In the subpolar and polar latitudes, the salinity is the lowest - an eye-

about 32%o, since the amount of precipitation exceeds evaporation, there is a large river runoff, especially in Siberian rivers, and there are many icebergs, mainly around Antarctica and Greenland.

The zonal pattern of salinity is disturbed by sea currents and the inflow of river waters. For example, in the temperate latitudes of the northern hemisphere, salinity is greater near the western coasts of the continents, where subtropical waters of increased salinity, brought by warm currents, enter, less - near the eastern coasts of the continents, where cold currents bring less saline subpolar waters.

Of the oceans, the Atlantic Ocean has the highest salinity. This is explained, firstly, by its comparative narrowness at low latitudes, combined with its proximity to Africa with its deserts, from where a hot dry wind blows unhindered onto the ocean, increasing the evaporation of sea water. Secondly, in temperate latitudes, the western wind carries the Atlantic air far into the depths of Eurasia, where a significant part of the precipitation falls from it, not completely returning to the Atlantic Ocean. The salinity of the Pacific Ocean is less, since, on the contrary, it is wide in the equatorial zone, where the salinity of the water is lower, and in the temperate latitudes of the Cordillera and the Andes, heavy precipitation is retained on the windward western slopes of the mountains, and they again enter the Pacific Ocean, desalinating it.

The lowest salinity of water in the Arctic Ocean, especially off the Asian coast, near the mouths of Siberian rivers - less than 10% 0. However, in subpolar latitudes, there is a seasonal change in water salinity: in autumn - winter, with the formation of sea ice and a decrease in river runoff, salinity increases, in spring - summer, with melting sea ice and an increase in river runoff, it decreases. Around Greenland and Antarctica, salinity also decreases in summer due to melting icebergs and thawing of the marginal parts of ice sheets and shelves.

Rice. 82. Types of vertical distribution of salinity (according to L.K. Davydov and others)

The maximum salinity of water is observed in tropical inland seas and bays surrounded by deserts, for example, in the Red Sea - 42% 0, in the Persian Gulf - 39% 0.

Despite the different salinity of sea water in different areas of the Ocean, the percentage of salts dissolved in it is unchanged. It is provided by the mobility of water, its continuous horizontal and vertical mixing, which together leads to a general circulation of the waters of the oceans.

The change in water salinity vertically in the oceans is different. Five zonal types of vertical distribution of salinity are outlined: I - polar, II - subpolar, III - moderate, IV - tropical and V - equatorial. They are presented in the form of graphs in Figure 82.

The depth distribution of salinity in the seas is very different depending on the balance of fresh moisture, the intensity of vertical mixing and water exchange with neighboring water areas.

Annual fluctuations in salinity in the open parts of the Ocean are insignificant and in the surface layers do not exceed 1% o, and from a depth of 1500-2000 m, salinity is practically unchanged throughout the year. In coastal marginal seas and bays, seasonal fluctuations in water salinity are more significant. In the seas of the Arctic Ocean, at the end of spring, salinity decreases due to the inflow of river waters, and in water areas with a monsoon climate in summer, also due to the abundance of precipitation. In polar and subpolar latitudes, seasonal changes in surface water salinity are largely due to the processes of freezing water in autumn and melting sea ice in spring, as well as the melting of glaciers and icebergs during the polar day, which will be discussed later.

The salinity of water affects many of its physical properties: temperature, density, electrical conductivity, sound propagation speed, ice formation rate, etc.

It is interesting to note that in the seas near the karst coasts, powerful underwater (submarine) sources of fresh water are not uncommon at the bottom, rising to the surface in the form of fountains. Such "fresh windows" among salt water are known off the coast of Yugoslavia in the Adriatic Sea, off the coast of Abkhazia in the Black Sea, off the coast of France, Florida and in other places. This water is used by sailors for household needs.

The gas composition of the oceans. In sea water, in addition to salts, the gases dissolved are nitrogen, oxygen, carbon dioxide, hydrogen sulfide, etc. And although the content of gases in water is extremely insignificant and noticeably changes in space and time, they are sufficient for the development of organic life and biogeochemical processes.

Oxygen in sea water more than in the atmosphere, especially in the upper layer (35% at 0°C). Its main source is phytoplankton, which is called the "lungs of the planet." Below 200 m, the oxygen content decreases, but from 1500 m it increases again, even in equatorial latitudes, due to the inflow of water from the subpolar regions, where oxygen saturation reaches 70–90%. Oxygen is consumed by recoiling into the atmosphere with an excess of it in the surface layers (especially during the day), for the respiration of marine organisms and for the oxidation of various substances. nitrogen less in sea water than in the atmosphere. The content of free nitrogen is associated with the decay of organic substances. Nitrogen dissolved in water is absorbed by special bacteria, processed into nitrogenous compounds, which are of great importance for the life of plants and animals. A certain amount of free and bound is dissolved in sea water. carbonic acid, which enters the water from the air during the respiration of marine organisms, during the decomposition of organic matter, as well as during volcanic eruptions. It is important for biological processes, as it is the only source of carbon that plants need to build organic matter. hydrogen sulfide It is formed in deep stagnant basins in the lower parts of the water column during the decomposition of organic matter and as a result of the vital activity of microorganisms (for example, in the Black Sea). Since hydrogen sulfide is a highly toxic substance, it dramatically reduces the biological productivity of water.

Since the solubility of gases is more intense at low temperatures, the waters of high latitudes contain more of them, including the most important gas for life - oxygen. The surface waters there are even supersaturated with oxygen and the biological productivity of the waters is higher than in low latitudes, although the species diversity of animals and plants is poorer. During the cold season, the ocean absorbs gases from the atmosphere; during the warm season, it releases them.

Density is an important physical property of sea water. Sea water is denser than fresh water. The higher the salinity and the lower the temperature of the water, the greater its density. The density of surface waters increases from the equator to the tropics due to an increase in salinity and from temperate latitudes to the polar circles as a result of a decrease in temperature, and in winter also due to an increase in salinity. This leads to intense subsidence of polar waters during the cold season, which lasts 8-9 months. In the bottom layers, polar waters move towards the equator, as a result of which the deep waters of the World Ocean are generally cold (2-4 ° C), but enriched with oxygen.

Color and transparency depend on the reflection, absorption and scattering of sunlight, as well as on substances of organic and mineral origin suspended in water. Blue color is inherent in water in the open part of the Ocean, where there are no suspensions. Near the coasts, where there is a lot of suspension brought by rivers and temporary streams from land, as well as due to the stirring of coastal soil during waves, the color of the water is greenish, yellow, brown, etc. With an abundance of plankton, the color of the water is bluish-green.

For visual observations of the color of sea water, a color scale is used, consisting of 21 test tubes with color solutions - from blue to brown. The color of the water cannot be identified with the color of the surface of the sea. It depends on weather conditions, especially cloud cover, as well as wind and waves.

Transparency is better in the open part of the Ocean, for example, in the Sargasso Sea - 67 m, worse - near the coasts, where there are a lot of suspensions. Transparency decreases during the period of mass development of plankton.

Glow of the sea (bioluminescence) - this is the glow in sea water of living organisms containing phosphorus and emitting "living" light. First of all, the simplest lower organisms (the night light, etc.), some bacteria, jellyfish, worms, and fish shine in all layers of the water. Therefore, the gloomy depths of the Ocean are not completely devoid of light. Glow amplification

vaysya with excitement, so the ships at night are accompanied by a real illumination. Among biologists there is no consensus on the purpose of the glow. It is believed that it serves either to scare away predators, or to search for food, or to attract individuals of the opposite sex in the dark. The cold glow of marine fish makes it possible for fishing boats to find their shoals.

Sound conductivity- acoustic property of sea water. The propagation of sound in sea water depends on temperature, salinity, pressure, gas and suspension content. On average, the speed of sound in the World Ocean ranges from 1400-1550 m/s. With an increase in temperature, an increase in salinity and pressure, it increases, and with a decrease, it decreases. Layers with different sound conductivity have been found in the oceans: sound-scattering layer and a layer with sound superconductivity - underwater

"sound channel". Accumulations of zooplankton and, accordingly, fish are confined to the sound-scattering layer. It experiences diurnal migrations: it rises at night, falls during the day. It is used by divers to dampen the noise from submarine engines, and by fishing boats to detect schools of fish. The "sound channel" began to be used for short-term forecasting of tsunami waves, in the practice of 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 plants and animals are able to concentrate radioactive isotopes. Therefore, at present, the catch of fish and other seafood is undergoing a special check for radioactivity.

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

Vola has many different physical and chemical properties. First of all, they depend on the table of contents and ambient temperature. Let's briefly describe some of them.

Water is a solvent. Since water is a solvent, it can be judged that all waters are gas-salt solutions of various chemical composition and various concentrations.

Salinity of ocean, sea and river water

Salinity of sea water(Table 1). The concentration of substances dissolved in water is characterized by salinity which is measured in ppm (% o), i.e., in grams of a substance per 1 kg of water.

Table 1. Salt content in sea and river water (in % of the total mass of salts)

Basic connections	Sea water	river water
Chlorides (NaCI, MgCb)
Sulphates (MgS0 4, CaS0 4, K 2 S0 4)
Carbonates (CaCOd)
Compounds of nitrogen, phosphorus, silicon, organic and other substances

Lines on a map connecting points of equal salinity are called isohalines.

Salinity of fresh water(see Table 1) is on average 0.146% o, and marine - on average 35 %O. Salts dissolved in water give it a bitter-salty taste.

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

Since the water in the oceans was formed from hot saline solutions of the earth's interior and gases, its salinity was primordial. There is reason to believe that at the first stages of the formation of the ocean, its waters did not differ much from river waters in terms of salt composition. Differences were outlined and began to intensify after the transformation of rocks as a result of their weathering, as well as the development of the biosphere. The modern salt composition of the ocean, as fossil remains show, was formed no later than the Proterozoic.

In addition to chlorides, sulfites and carbonates, almost all chemical elements known on Earth, including noble metals, have been found in sea water. However, the content of most elements in seawater is negligible, for example, only 0.008 mg of gold in a cubic meter of water was detected, and the presence of tin and cobalt is indicated by their presence in the blood of marine animals and in bottom sediments.

Salinity of ocean waters- the value is not constant (Fig. 1). It depends on the climate (the ratio of precipitation and evaporation from the surface of the ocean), the formation or melting of ice, sea currents, near the continents - on the influx of fresh river water.

Rice. 1. Dependence of water salinity on latitude

In the open ocean, salinity ranges from 32-38%; in the marginal and Mediterranean seas, its fluctuations are much greater.

The salinity of waters down to a depth of 200 m is especially strongly affected by the amount of precipitation and evaporation. Based on this, we can say that the salinity of sea water is subject to the law of zoning.

In the equatorial and subequatorial regions, salinity is 34% c, because the amount of precipitation is greater than the water spent on evaporation. In tropical and subtropical latitudes - 37, since there is little precipitation, and evaporation is high. In temperate latitudes - 35% o. The lowest salinity of sea water is observed in the subpolar and polar regions - only 32, since the amount of precipitation exceeds evaporation.

Sea currents, river runoff, and icebergs disrupt the zonal pattern of salinity. For example, in the temperate latitudes of the Northern Hemisphere, the salinity of water is greater near the western coasts of the continents, where more saline subtropical waters are brought with the help of currents, and the salinity of water is lower near the eastern coasts, where cold currents bring less saline water.

Seasonal changes in water salinity occur in subpolar latitudes: in autumn, due to the formation of ice and a decrease in the strength of river runoff, salinity increases, and in spring and summer, due to ice melting and increased river runoff, salinity decreases. Around Greenland and Antarctica, salinity decreases during the summer as a result of the melting of nearby icebergs and glaciers.

The most saline of all oceans is the Atlantic Ocean, the waters of the Arctic Ocean have the lowest salinity (especially off the Asian coast, near the mouths of Siberian rivers - less than 10% o).

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

Its density, electrical conductivity, ice formation and many other properties depend on the salinity of water.

The gas composition of ocean water

In addition to various salts, different gases are dissolved in the waters of the World Ocean: nitrogen, oxygen, carbon dioxide, hydrogen sulfide, etc. As in the atmosphere, oxygen and nitrogen predominate in ocean waters, but in slightly different proportions (for example, the total amount of free oxygen in the ocean 7480 billion tons, which is 158 times less than in the atmosphere). Despite the fact that gases occupy a relatively small place in water, this is enough to influence organic life and various biological processes.

The amount of gases is determined by the temperature and salinity of water: the higher the temperature and salinity, the lower the solubility of gases and the lower their content in water.

So, for example, at 25 ° C, up to 4.9 cm / l of oxygen and 9.1 cm 3 / l of nitrogen can dissolve in water, at 5 ° C - 7.1 and 12.7 cm 3 / l, respectively. Two important consequences follow from this: 1) the oxygen content in the surface waters of the ocean is much higher in temperate and especially polar latitudes than in low latitudes (subtropical and tropical), which affects the development of organic life - the richness of the first and the relative poverty of the second waters; 2) in the same latitudes, the oxygen content in ocean waters is higher in winter than in summer.

Daily changes in the gas composition of water associated with temperature fluctuations are small.

The presence of oxygen in ocean water contributes to the development of organic life in it and the oxidation of organic and mineral products. The main source of oxygen in ocean water is phytoplankton, called the "lungs of the planet." Oxygen is mainly consumed for the respiration of plants and animals in the upper layers of sea waters and for the oxidation of various substances. In the depth interval of 600-2000 m, there is a layer oxygen minimum. A small amount of oxygen is combined with a high content of carbon dioxide. The reason is the decomposition in this water layer of the bulk of the organic matter coming from above and the intensive dissolution of biogenic carbonate. Both processes require free oxygen.

The amount of nitrogen in sea water is much less than in the atmosphere. This gas mainly enters the water from the air during the breakdown of organic matter, but is also produced during the respiration of marine organisms and their decomposition.

In the water column, in deep stagnant basins, as a result of the vital activity of organisms, hydrogen sulfide is formed, which is toxic and inhibits the biological productivity of water.

Heat capacity of ocean waters

Water is one of the most heat-intensive bodies in nature. The heat capacity of only a ten meter layer of the ocean is four times greater than the heat capacity of the entire atmosphere, and a 1 cm layer of water absorbs 94% of the solar heat entering its surface (Fig. 2). Due to this circumstance, the ocean slowly heats up and slowly releases heat. Due to the high heat capacity, all water bodies are powerful heat accumulators. Cooling, the water gradually releases its heat into the atmosphere. Therefore, the World Ocean performs the function thermostat our planet.

Rice. 2. Dependence of heat capacity of water on temperature

Ice and especially snow have the lowest thermal conductivity. As a result, ice protects the water on the surface of the reservoir from hypothermia, and snow protects the soil and winter crops from freezing.

Heat of evaporation water - 597 cal / g, and melting heat - 79.4 cal / g - these properties are very important for living organisms.

Ocean water temperature

An indicator of the thermal state of the ocean is temperature.

Average temperature of ocean waters- 4 °C.

Despite the fact that the surface layer of the ocean performs the functions of the Earth's temperature regulator, in turn, the temperature of sea waters depends on the heat balance (inflow and outflow of heat). The heat input is made up of , and the flow rate is made up of the costs of water evaporation and turbulent heat exchange with the atmosphere. Despite the fact that the proportion of heat spent on turbulent heat transfer is not large, its significance is enormous. It is with its help that the planetary redistribution of heat occurs through the atmosphere.

On the surface, the temperature of ocean waters ranges from -2 ° C (freezing temperature) to 29 ° C in the open ocean (35.6 ° C in the Persian Gulf). The average annual temperature of the surface waters of the World Ocean is 17.4°C, and in the Northern Hemisphere it is about 3°C ​​higher than in the Southern Hemisphere. The highest temperature of surface ocean waters in the Northern Hemisphere is in August, and the lowest is in February. In the Southern Hemisphere, the opposite is true.

Since it has thermal relationships with the atmosphere, the temperature of surface waters, like air temperature, depends on the latitude of the area, i.e., it is subject to the zonality law (Table 2). Zoning is expressed in a gradual decrease in water temperature from the equator to the poles.

In tropical and temperate latitudes, water temperature mainly depends on sea currents. So, due to warm currents in tropical latitudes in the west of the oceans, temperatures are 5-7 ° C higher than in the east. However, in the Northern Hemisphere, due to warm currents in the east of the oceans, temperatures are positive all year round, and in the west, due to cold currents, the water freezes in winter. In high latitudes, the temperature during the polar day is about 0 °C, and during the polar night under the ice it is about -1.5 (-1.7) °C. Here, the water temperature is mainly affected by ice phenomena. In autumn, heat is released, softening the temperature of air and water, and in spring, heat is spent on melting.

Table 2. Average annual temperatures of the surface waters of the oceans

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

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

An important influence on the temperature of ocean water is exerted by the climate of the surrounding territories, as well as the time of year, since the sun's heat, which heats the upper layer of the World Ocean, depends on it. The highest water temperature in the Northern Hemisphere is observed in August, the lowest - in February, and in the Southern - vice versa. Daily fluctuations in sea water temperature at all latitudes are about 1 °C, the largest values ​​of annual temperature fluctuations are observed in subtropical latitudes - 8-10 °C.

The temperature of ocean water also changes with depth. It decreases and already at a depth of 1000 m almost everywhere (on average) below 5.0 °C. At a depth of 2000 m, the water temperature levels off, dropping to 2.0-3.0 ° C, and in polar latitudes - up to tenths of a degree above zero, after which it either drops very slowly or even rises slightly. For example, in the rift zones of the ocean, where at great depths there are powerful outlets of underground hot water under high pressure, with temperatures up to 250-300 °C. In general, two main layers of water are distinguished vertically in the World Ocean: warm superficial And powerful cold extending to the bottom. Between them is a transitional temperature jump layer, or main thermal clip, a sharp decrease in temperature occurs within it.

This picture of the vertical distribution of water temperature in the ocean is disturbed at high latitudes, where at a depth of 300–800 m there is a layer of warmer and saltier water that came from temperate latitudes (Table 3).

Table 3. Average values ​​of ocean water temperature, °С

	Depth, m
equatorial
tropical
Polar

Change in the volume of water with a change in temperature

A sudden increase in the volume of water when freezing is a peculiar property of water. With a sharp decrease in temperature and its transition through the zero mark, a sharp increase in the volume of ice occurs. As the volume increases, the ice becomes lighter and floats to the surface, becoming less dense. Ice protects the deep layers of water from freezing, as it is a poor conductor of heat. The volume of ice increases by more than 10% compared to the initial volume of water. When heated, a process occurs that is the opposite of expansion - compression.

Density of water

Temperature and salinity are the main factors that determine the density of water.

For sea water, the lower the temperature and the higher the salinity, the greater the density of the water (Fig. 3). So, at a salinity of 35% o and a temperature of 0 ° C, the density of sea water is 1.02813 g / cm 3 (the mass of each cubic meter of such sea water is 28.13 kg more than the corresponding volume of distilled water). The temperature of sea water of the highest density is not +4 °C, as in fresh water, but negative (-2.47 °C at a salinity of 30% c and -3.52 °C at a salinity of 35%o

Rice. 3. Relationship between the density of sea water and its salinity and temperature

Due to the increase in salinity, the density of water increases from the equator to the tropics, and as a result of a decrease in temperature, from temperate latitudes to the Arctic Circles. In winter, the polar waters sink and move in the bottom layers towards the equator, so the deep waters of the World Ocean are generally cold, but enriched with oxygen.

The dependence of water density on pressure was also revealed (Fig. 4).

Rice. 4. Dependence of the density of the sea water (A "= 35% o) on pressure at various temperatures

The ability of water to self-purify

This is an important property of water. In the process of evaporation, water passes through the soil, which, in turn, is a natural filter. However, if the pollution limit is violated, the self-cleaning process is violated.

Color and transparency depend on the reflection, absorption and scattering of sunlight, as well as on the presence of suspended particles of organic and mineral origin. In the open part, the color of the ocean is blue, near the coast, where there are a lot of suspensions, it is greenish, yellow, brown.

In the open part of the ocean, water transparency is higher than near the coast. In the Sargasso Sea, the water transparency is up to 67 m. During the development of plankton, the transparency decreases.

In the seas, such a phenomenon as glow of the sea (bioluminescence). Glow in sea water living organisms containing phosphorus, primarily such as protozoa (night light, etc.), bacteria, jellyfish, worms, fish. Presumably, the glow serves to scare away predators, to search for food, or to attract individuals of the opposite sex in the dark. The glow helps fishing boats find schools of fish in sea water.

Sound conductivity - acoustic property of water. Found in the oceans sound-diffusing mine And underwater "sound channel", possessing sonic superconductivity. The sound-diffusing layer rises at night and falls during the day. It is used by submariners to dampen submarine engine noise, and by fishing boats to detect schools of fish. "Sound
signal" is used for short-term forecasting of tsunami waves, in underwater navigation for ultra-long-range transmission of acoustic signals.

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

natural radioactivity sea ​​water is small. But many animals and plants have the ability to concentrate radioactive isotopes, so the seafood catch is tested for radioactivity.

Mobility is a characteristic property of liquid water. Under the influence of gravity, under the influence of wind, attraction by the Moon and the Sun and other factors, water moves. When moving, the water is mixed, which allows even distribution of waters of different salinity, chemical composition and temperature.