Caspian Sea: description, depth, width, interesting facts. Countries on the shores of the Caspian Sea Azov and Caspian Seas on the map

On Sunday, August 12, in Aktau, Kazakhstan, the presidents of Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan signed the Convention on the Legal Status of the Caspian Sea. Previously, its status was regulated by Soviet-Iranian treaties, in which the Caspian Sea was defined as a closed (inland) sea, and each Caspian state had sovereign rights to a 10-mile zone and equal rights to the rest of the sea.

Now, according to the new convention, each country is assigned its own territorial waters (zones 15 miles wide). In addition, the provisions of the 1982 UN Convention on the Law of the Sea will not apply to the Caspian Sea, the seabed will be delimited into sectors, as is done by neighboring seas, and sovereignty over the water column will be established on the basis of the principle that it is a lake.

Why is the Caspian considered neither a lake nor a sea?

To be considered a sea, the Caspian Sea must have access to the ocean; this is one of the most important conditions for which a body of water can be called a sea. But the Caspian Sea has no access to the ocean, so it is considered a closed body of water not connected to the World Ocean.

The second feature that distinguishes sea waters from lake waters is their high salinity. The water in the Caspian Sea is indeed salty, but in its salt composition it occupies an intermediate position between the river and the ocean. In addition, in the Caspian Sea, salinity increases towards the south. The Volga delta contains 0.3‰ salts, and in the eastern regions of the Southern and Middle Caspian Sea the salinity reaches 13-14‰. And if we talk about the salinity of the World Ocean, it averages 34.7 ‰.

Due to its specific geographical and hydrological characteristics, the reservoir received a special legal status. The summit participants decided that the Caspian Sea is an inland body of water that does not have a direct connection with the World Ocean, and therefore cannot be considered a sea, and at the same time, due to its size, water composition and bottom features, cannot be considered a lake.

What has been achieved since the signing of the Convention?

The new treaty expands opportunities for cooperation between countries and also involves limiting any military presence of third countries. According to political scientist, director of the Institute of Modern States Alexey Martynov, the main achievement of the last summit is that its participants managed to stop any talk about the possible construction of military bases and NATO infrastructure facilities in the Caspian Sea.

“The most important thing that was achieved was to fix that the Caspian Sea will be demilitarized for all Caspian states. There will be no other military personnel there except those representing the countries that signed the Caspian Agreement. This is a fundamental and main question that was important to fix. Everything else, what is divided proportionally into zones of influence, zones of extraction of biological resources, zones of extraction of shelf resources, was not so important. As we remember, in the last twenty years the military has been actively seeking to enter the region. The United States even wanted to build its own military base there,” says Martynov.

In addition to the distribution of each country's shares in the oil and gas fields of the Caspian basin, the Convention also provides for the construction of pipelines. As stated in the document, the rules for laying them provide for the consent of only neighboring countries, and not all countries of the Caspian Sea. After signing the agreement, Turkmenistan, in particular, stated that it was ready to lay pipelines along the bottom of the Caspian Sea, which would allow it to export its gas through Azerbaijan to Europe. The consent of Russia, which previously insisted that the project could only be implemented with the permission of all five Caspian states, is now no longer required. They plan to subsequently connect the gas pipeline to the Trans-Anatolian gas pipeline, through which natural gas will flow through the territory of Azerbaijan, Georgia and Turkey to Greece.

“Turkmenistan is not a foreign country to us, but our partner, a country that we consider very important for us in the post-Soviet space. We cannot be against them receiving an additional impetus for development through such pipeline projects. Gas has long been coming from Turkmenistan and other countries through another pipeline system, somewhere it is even mixed with Russian gas, and there is nothing wrong with that. If this project works, everyone will benefit, including Russia. Under no circumstances should the project be considered as some kind of competition. The European market is so large and insatiable, I mean the energy market, that there is enough room for everyone,” says Martynov.

Today, almost all Turkmen gas is supplied to China, where Russia also intends to supply blue fuel. For this purpose, in particular, a large-scale project for the construction of the Power of Siberia gas pipeline is being implemented. Thus, the geography of gas supplies for both countries can expand - Turkmenistan will gain access to the European market, and Russia will be able to increase its gas supplies to China.

In dry and hot climates, a large amount of sea water evaporates, water molecules pass into the air. Thus, every year such a huge amount of water particles is carried away from the surface of the Caspian Sea that all together they would fill a bowl with a volume of several hundred cubic kilometers. This amount of water could fill ten such reservoirs as Kuibyshevskoye.

But can water from the surface of the sea get into the bottom layers of the Caspian Sea, to a depth of 900-980 meters?

This is possible provided that the density of the surface layers of water is greater than the density of the bottom layers.

It is known that the density of sea water depends on salinity and temperature. The more salts the water contains, the denser it is, and therefore heavier. High temperature water is less dense than cold water. Only at low temperatures (about 0-4° Celsius) is the opposite relationship given, when water, heating up, becomes more dense.

High salinity of the surface layers of the sea is created in the hot season, when the water evaporates strongly, but the salt remains in the sea. At this time, the salinity of surface waters turns out to be no less, and even slightly greater than the salinity of deep and near-bottom layers.

The temperature of surface waters in the warm season is the same everywhere, about 25-28°, that is, five times higher than at a depth of 150-200 meters. With the onset of the cold season, the temperature of the surface layers decreases and during a certain period it turns out to be 5-6° above zero.

The temperature of the bottom and deep (deeper than 150-200 m) layers of the Caspian Sea is the same (5-6°), practically unchanged throughout the year.

Under these conditions, it is possible for denser surface cold and highly saline water to sink into the bottom layers.

Only in the southern regions of the Caspian Sea the surface water temperature, as a rule, does not drop to 5-6° even in winter. And, although the sinking of surface water into the depths directly in these areas cannot occur, water that has sank from the surface in the more northern parts of the sea is brought here by deep currents.

A similar phenomenon is observed in the eastern part of the border zone between the Middle and Southern Caspian Seas, where cooled surface waters descend along the southern slope of the border underwater threshold and then follow a deep current into the southern regions of the sea.

This widespread mixing of surface and deep waters is confirmed by the fact that oxygen was found at all depths of the Caspian Sea.

Oxygen can only reach depths with the surface layers of water, where it comes directly from the atmosphere or as a result of photosynthesis.

If there were no continuous supply of oxygen to the bottom layers, it would quickly be absorbed by animal organisms there or spent on the oxidation of soil organic matter. Instead of oxygen, the bottom layers would be saturated with hydrogen sulfide, which is what is observed in the Black Sea. The vertical circulation in it is so weak that oxygen in sufficient quantities does not reach the depth, where hydrogen sulfide is formed.

Although oxygen has been found at all depths of the Caspian Sea, it is not in the same quantity in different seasons of the year.

The water column is richest in oxygen in winter. The harsher the winter, that is, the lower the surface temperature, the more intense the aeration process occurs, which reaches the deepest parts of the sea. Conversely, several warm winters in a row can cause the appearance of hydrogen sulfide in the bottom layers and even the complete disappearance of oxygen. But such phenomena are temporary and disappear during the first more or less severe winter.

The upper water column to a depth of 100-150 meters is especially rich in dissolved oxygen. Here the oxygen content ranges from 5 to 10 cubic meters. cm in liter. At depths of 150-450 m, there is much less oxygen - from 5 to 2 cubic meters. cm in liter.

Below 450 m there is very little oxygen and life is represented very sparsely - several species of worms and mollusks, small crustaceans.

Mixing of water masses is also caused by surge phenomena and waves.

Waves, currents, winter vertical circulation, surges, and surges operate constantly and are important factors in water mixing. It is not surprising, therefore, that no matter where we take a water sample in the Caspian Sea, its chemical composition will be constant everywhere. If there were no mixing of waters, all living organisms at great depths would die out. Life would only be possible in the photosynthetic zone.

Where the waters mix well and this process occurs quickly, for example in shallow areas of the seas and oceans, life is richer.

The constancy of the salt composition of the water of the Caspian Sea is a general property of the waters of the World Ocean. But this does not mean that the chemical composition of the Caspian Sea is the same as in the ocean or in any sea connected to the ocean. Consider a table showing the salt content in the waters of the ocean, the Caspian Sea and the Volga.

The table shows that ocean water has very little in common with river water in terms of salt composition. In terms of salt composition, the Caspian Sea occupies an intermediate position between the river and the ocean, which is explained by the great influence of river runoff on the chemical composition of Caspian water. The ratio of salts dissolved in the water of the Aral Sea is closer to the salt composition of river water. This is understandable, since the ratio of the volume of river flow to the volume of water in the Aral Sea is much greater than for the Caspian Sea. A large amount of sulfuric acid salts in the Caspian Sea gives its water a bitter-salty taste, distinguishing it from the waters of the oceans and seas connected to them

The salinity of the Caspian Sea continuously increases towards the south. In the pre-estuary space of the Volga, a kilogram of water contains hundredths of a gram of salts. In the eastern regions of the Southern and Middle Caspian Sea, salinity reaches 13-14‰

The concentration of salts in Caspian water is low. So, in this water you can dissolve almost twenty times more salts than are present in it.

B.A. Shlyamin. Caspian Sea. 1954

The Caspian Sea is inland and located in a vast continental depression on the border of Europe and Asia. The Caspian Sea has no connection with the ocean, which formally allows it to be called a lake, but it has all the features of the sea, since in past geological eras it had connections with the ocean.

The sea area is 386.4 thousand km2, the volume of water is 78 thousand m3.

The Caspian Sea has a vast drainage basin, with an area of ​​about 3.5 million km2. The nature of the landscapes, climatic conditions and types of rivers are different. Despite its vastness, only 62.6% of its area is in waste areas; about 26.1% - for non-drainage. The area of ​​the Caspian Sea itself is 11.3%. 130 rivers flow into it, but almost all of them are located in the north and west (and the eastern coast does not have a single river reaching the sea). The largest river in the Caspian basin is the Volga, which provides 78% of the river waters entering the sea (it should be noted that more than 25% of the Russian economy is located in the basin of this river, and this undoubtedly determines many other features of the waters of the Caspian Sea), as well as the Kura River , Zhaiyk (Ural), Terek, Sulak, Samur.

Physiographically and by nature, the sea is divided into three parts: northern, middle and southern. The conventional border between the northern and middle parts runs along the line Chechen Island–Cape Tyub-Karagan, and between the middle and southern parts along the line Zhiloy Island–Cape Kuuli.

The shelf of the Caspian Sea is on average limited to depths of about 100 m. The continental slope, which begins below the shelf edge, ends in the middle part at approximately 500–600 m depths, in the southern part, where it is very steep, at 700–750 m.

The northern part of the sea is shallow, its average depth is 5–6 m, the maximum depths of 15–20 m are located on the border with the middle part of the sea. The bottom topography is complicated by the presence of banks, islands, and grooves.

The middle part of the sea is an isolated basin, the region of maximum depths of which - Derbent - is shifted to the western coast. The average depth of this part of the sea is 190 m, the greatest is 788 m.

The southern part of the sea is separated from the middle by the Absheron threshold, which is a continuation. The depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian depression with a maximum sea depth of 1025 m is located east of the Kura delta. Several underwater ridges up to 500 m high rise above the bottom of the basin.

The shores of the Caspian Sea are diverse. In the northern part of the sea they are quite indented. Here are the Kizlyarsky, Agrakhansky, Mangyshlaksky bays and many shallow bays. Notable peninsulas: Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak. Large islands in the northern part of the sea are Tyuleniy and Kulaly. In the deltas of the Volga and Ural rivers, the coastline is complicated by many islands and channels, often changing their position. Many small islands and banks are located on other parts of the coastline.

The middle part of the sea has a relatively flat coastline. The Absheron Peninsula is located on the western coast, on the border with the southern part of the sea. To the east of it there are islands and banks of the Absheron archipelago, of which the largest island is Zhiloy. The eastern coast of the Middle Caspian is more indented; the Kazakh Gulf with Kenderli Bay and several capes stand out here. The largest bay of this coast is.

South of the Absheron Peninsula are the islands of the Baku archipelago. The origin of these islands, as well as some banks off the eastern coast of the southern part of the sea, is associated with the activity of underwater mud volcanoes lying on the seabed. On the eastern shore there are large bays of Turkmenbashi and Turkmensky, and near it the island of Ogurchinsky.

One of the most striking phenomena of the Caspian Sea is the periodic variability of its level. In historical times, the Caspian Sea had a level lower than the World Ocean. Fluctuations in the level of the Caspian Sea are so great that for more than a century they have attracted the attention of not only scientists. Its peculiarity is that in the memory of mankind its level has always been below the level of the World Ocean. Since the beginning of instrumental observations (since 1830) of sea level, the amplitude of its fluctuations has been almost 4 m, from –25.3 m in the eighties of the 19th century. to –29 m in 1977. In the last century, the level of the Caspian Sea changed significantly twice. In 1929 it stood at about -26 m, and since it had been close to this level for almost a century, this level position was considered to be a long-term or secular average. In 1930 the level began to decline rapidly. By 1941 it had dropped by almost 2 m. This led to the drying out of vast coastal areas of the bottom. The decrease in level, with slight fluctuations (short-term slight rises in level in 1946–1948 and 1956–1958), continued until 1977 and reached a level of –29.02 m, i.e. the level reached its lowest position in history the last 200 years.

In 1978, contrary to all forecasts, sea level began to rise. As of 1994, the level of the Caspian Sea was at –26.5 m, that is, over 16 years the level rose by more than 2 m. The rate of this rise is 15 cm per year. The level increase in some years was higher, and in 1991 it reached 39 cm.

The general fluctuations in the level of the Caspian Sea are superimposed by its seasonal changes, the long-term average of which reaches 40 cm, as well as surge phenomena. The latter are especially pronounced in the Northern Caspian Sea. The northwestern coast is characterized by large surges created by prevailing storms from the eastern and southeastern directions, especially in the cold season. A number of large (more than 1.5–3 m) surges have been observed here over the past decades. A particularly large surge with catastrophic consequences was noted in 1952. Fluctuations in the level of the Caspian Sea cause great damage to the states surrounding its waters.

Climate. The Caspian Sea is located in temperate and subtropical climates. Climatic conditions change in the meridional direction, since the sea stretches from north to south for almost 1200 km.

Various circulation systems interact in the Caspian region, however, winds from eastern directions predominate throughout the year (influence of the Asian High). The position at fairly low latitudes provides a positive balance of heat influx, so the Caspian Sea serves as a source of heat and moisture for passing people most of the year. The average annual temperature in the northern part of the sea is 8–10°C, in the middle - 11–14°C, in the southern part - 15–17°C. However, in the northernmost areas of the sea, the average January temperature is from –7 to –10°C, and the minimum during invasions is up to –30°C, which determines the formation of ice cover. In summer, rather high temperatures dominate over the entire region under consideration - 24–26°C. Thus, the Northern Caspian is subject to the most dramatic temperature fluctuations.

The Caspian Sea is characterized by a very small amount of precipitation per year - only 180 mm, with most of it falling during the cold season of the year (from October to March). However, the Northern Caspian differs in this respect from the rest of the basin: here the average annual precipitation is lower (for the western part only 137 mm), and the seasonal distribution is more uniform (10–18 mm per month). In general, we can talk about proximity to arid ones.

Water temperature. The distinctive features of the Caspian Sea (large differences in depths in different parts of the sea, nature, isolation) have a certain influence on the formation of temperature conditions. In the shallow Northern Caspian Sea, the entire water column can be considered homogeneous (the same applies to shallow bays located in other parts of the sea). In the Middle and Southern Caspian Sea, surface and deep masses can be distinguished, separated by a transition layer. In the Northern Caspian and in the surface layers of the Middle and Southern Caspian, water temperatures vary over a wide range. In winter, temperatures vary from north to south from less than 2 to 10°C, the water temperature off the west coast is 1–2°C higher than that on the east, in the open sea the temperature is higher than at the coasts: by 2–3°C in the middle part and by 3–4°С in the southern part of the sea. In winter, the distribution of temperature with depth is more uniform, which is facilitated by winter vertical circulation. During moderate and severe winters in the northern part of the sea and shallow bays of the east coast, the water temperature drops to freezing temperature.

In summer, the temperature varies in space from 20 to 28°C. The highest temperatures are observed in the southern part of the sea; temperatures are also quite high in the well-warmed shallow Northern Caspian Sea. The zone where the lowest temperatures occur is adjacent to the east coast. This is explained by the rise of cold deep waters to the surface. Temperatures are also relatively low in the poorly heated deep-sea central part. In open areas of the sea, at the end of May–beginning of June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often it is located between 20 and 30 m in the middle part of the sea and 30 and 40 m in the southern part. In the middle part of the sea, due to the surge off the eastern coast, the shock layer rises close to the surface. In the bottom layers of the sea, the temperature throughout the year is about 4.5°C in the middle part and 5.8–5.9°C in the southern part.

Salinity. Salinity values ​​are determined by factors such as river runoff, water dynamics, including mainly wind and gradient currents, the resulting water exchange between the western and eastern parts of the Northern Caspian and between the Northern and Middle Caspian, bottom topography, which determines the location of waters with different, mainly along isobath, evaporation, providing a deficit of fresh water and an influx of saltier water. These factors collectively influence seasonal differences in salinity.

The Northern Caspian Sea can be considered as a constant mixing of river and Caspian waters. The most active mixing occurs in the western part, where both river and Central Caspian waters directly flow. Horizontal salinity gradients can reach 1‰ per 1 km.

The eastern part of the Northern Caspian is characterized by a more uniform salinity field, since most of the river and sea (Middle Caspian) waters enter this area of ​​the sea in a transformed form.

Based on the values ​​of horizontal salinity gradients, it is possible to distinguish in the western part of the Northern Caspian the river-sea contact zone with water salinity from 2 to 10‰, in the eastern part from 2 to 6‰.

Significant vertical salinity gradients in the Northern Caspian are formed as a result of the interaction of river and sea waters, with runoff playing a decisive role. The strengthening of vertical stratification is also facilitated by the unequal thermal state of the water layers, since the temperature of the surface desalinated waters coming from the seashore in summer is 10–15°C higher than the bottom waters.

In the deep-sea depressions of the Middle and Southern Caspian Sea, fluctuations in salinity in the upper layer are 1–1.5‰. The largest difference between the maximum and minimum salinity was noted in the area of ​​the Absheron threshold, where it is 1.6‰ in the surface layer and 2.1‰ at a 5 m horizon.

The decrease in salinity along the western coast of the South Caspian Sea in the 0–20 m layer is caused by the flow of the Kura River. The influence of the Kura runoff decreases with depth; at horizons of 40–70 m, the range of salinity fluctuations is no more than 1.1‰. Along the entire western coast to the Absheron Peninsula there is a strip of desalinated water with a salinity of 10–12.5‰, coming from the Northern Caspian Sea.

In addition, in the Southern Caspian Sea, an increase in salinity occurs when salted waters are carried out from bays and gulfs on the eastern shelf under the influence of southeastern winds. Subsequently, these waters are transferred to the Middle Caspian Sea.

In the deep layers of the Middle and Southern Caspian Sea, the salinity is about 13‰. In the central part of the Middle Caspian, such salinity is observed at horizons below 100 m, and in the deep-water part of the Southern Caspian, the upper boundary of waters with high salinity drops to 250 m. Obviously, in these parts of the sea, vertical mixing of waters is difficult.

Surface water circulation. Currents in the sea are mainly wind-driven. In the western part of the Northern Caspian, currents of the western and eastern quarters are most often observed, in the eastern part - southwestern and southern ones. Currents caused by the runoff of the Volga and Ural rivers can be traced only within the estuary coastal area. The prevailing current speeds are 10–15 cm/s; in open areas of the Northern Caspian Sea, maximum speeds are about 30 cm/s.

In the coastal areas of the middle and southern parts of the sea, in accordance with the wind directions, currents in the northwestern, northern, southeastern and southern directions are observed; near the east coast, currents in the eastern direction often occur. Along the western coast of the middle part of the sea, the most stable currents are southeastern and southern. Current speeds are on average about 20–40 cm/s, with maximum speeds reaching 50–80 cm/s. Other types of currents also play a significant role in the circulation of sea waters: gradient, seiche, and inertial.

Ice formation. The Northern Caspian Sea is covered with ice every year in November, the area of ​​the frozen part of the water area depends on the severity of the winter: in severe winters the entire Northern Caspian Sea is covered with ice, in mild winters the ice remains within 2–3 meter isobath. The appearance of ice in the middle and southern parts of the sea occurs in December-January. On the eastern coast the ice is of local origin, on the western coast it is most often brought from the northern part of the sea. In severe winters, shallow bays freeze off the eastern coast of the middle part of the sea, shores and fast ice form off the coast, and on the western coast, drifting ice spreads to the Absheron Peninsula in abnormally cold winters. The disappearance of ice cover is observed in the second half of February–March.

Oxygen content. The spatial distribution of dissolved oxygen in the Caspian Sea has a number of patterns.
The central part of the waters of the Northern Caspian Sea is characterized by a fairly uniform distribution of oxygen. An increased oxygen content is found in the areas near the Volga River near the mouth, while a decreased oxygen content is found in the southwestern part of the Northern Caspian Sea.

In the Middle and Southern Caspian Sea, the highest concentrations of oxygen are confined to shallow coastal areas and pre-estuary coastal areas of rivers, with the exception of the most polluted areas of the sea (Baku Bay, Sumgait region, etc.).

In the deep-water areas of the Caspian Sea, the main pattern remains the same throughout all seasons - a decrease in oxygen concentration with depth.
Thanks to autumn-winter cooling, the density of the North Caspian Sea waters increases to a value at which it becomes possible for North Caspian waters with a high oxygen content to flow along the continental slope to significant depths of the Caspian Sea.

The seasonal distribution of oxygen is mainly associated with the annual course and seasonal relationship of production-destruction processes occurring in the sea.

In spring, the production of oxygen during photosynthesis very significantly covers the decrease in oxygen caused by a decrease in its solubility with increasing water temperature in spring.

In the areas of the estuary coastal areas of rivers feeding the Caspian Sea, in the spring there is a sharp increase in the relative oxygen content, which in turn is an integral indicator of the intensification of the photosynthesis process and characterizes the degree of productivity of the mixing zones of sea and river waters.

In summer, due to significant warming and activation of photosynthesis processes, the leading factors in the formation of the oxygen regime are photosynthetic processes in surface waters, and biochemical oxygen consumption by bottom sediments in bottom waters.

Due to the high temperature of the waters, the stratification of the water column, the large influx of organic matter and its intense oxidation, oxygen is quickly consumed with minimal entry into the lower layers of the sea, as a result of which an oxygen deficiency zone is formed in the Northern Caspian Sea. Intense photosynthesis in the open waters of the deep-sea regions of the Middle and Southern Caspian Sea covers the upper 25-meter layer, where oxygen saturation is more than 120%.

In autumn, in the well-aerated shallow areas of the Northern, Middle and Southern Caspian Sea, the formation of oxygen fields is determined by the processes of water cooling and the less active, but still ongoing process of photosynthesis. The oxygen content is increasing.

The spatial distribution of nutrients in the Caspian Sea reveals the following patterns:

• increased concentrations of nutrients are characteristic of areas near the mouth of the coastal rivers feeding the sea and shallow areas of the sea subject to active anthropogenic influence (Baku Bay, Turkmenbashi Bay, water areas adjacent to Makhachkala, Fort Shevchenko, etc.);
• The Northern Caspian, which is a vast mixing zone of river and sea waters, is characterized by significant spatial gradients in the distribution of nutrients;
• in the Middle Caspian, the nature of the circulation contributes to the rise of deep waters with a high content of nutrients into the overlying layers of the sea;
• in the deep-water regions of the Middle and Southern Caspian Sea, the vertical distribution of nutrients depends on the intensity of the convective mixing process, and their content increases with depth.

The dynamics of nutrient concentrations throughout the year in the Caspian Sea are influenced by such factors as seasonal fluctuations in nutrient runoff into the sea, the seasonal ratio of production-destructive processes, the intensity of exchange between soil and water mass, ice conditions in winter in the Northern Caspian, winter processes vertical circulation in deep sea areas.

In winter, a significant area of ​​the Northern Caspian Sea is covered with ice, but biochemical processes actively develop in subglacial water and in ice. The ice of the Northern Caspian, being a kind of accumulator of nutrients, transforms these substances entering the sea from and from the atmosphere.

As a result of the winter vertical circulation of water in the deep-water regions of the Middle and Southern Caspian Sea during the cold season, the active layer of the sea is enriched with nutrients due to their supply from the underlying layers.

Spring for the waters of the Northern Caspian Sea is characterized by a minimum content of phosphates, nitrites and silicon, which is explained by the spring outbreak of phytoplankton development (silicon is actively consumed by diatoms). High concentrations of ammonium and nitrate nitrogen, characteristic of the waters of a large area of ​​the Northern Caspian Sea during floods, are due to intensive washing by river waters.

In the spring season, in the area of ​​water exchange between the Northern and Middle Caspian Seas in the subsurface layer, with a maximum oxygen content, the phosphate content is minimal, which, in turn, indicates the activation of the photosynthesis process in this layer.

In the Southern Caspian, the distribution of nutrients in spring is basically similar to their distribution in the Middle Caspian.

In summer, a redistribution of various forms of biogenic compounds is detected in the waters of the Northern Caspian Sea. Here the content of ammonium nitrogen and nitrates decreases significantly, while at the same time there is a slight increase in the concentrations of phosphates and nitrites and a rather significant increase in the concentration of silicon. In the Middle and Southern Caspian Sea, the concentration of phosphates has decreased due to their consumption during photosynthesis and the difficulty of water exchange with the deep-sea accumulation zone.

In autumn in the Caspian Sea, due to the cessation of activity of some types of phytoplankton, the content of phosphates and nitrates increases, and the concentration of silicon decreases, as there is an autumn outbreak of the development of diatoms.

Oil has been extracted on the Caspian Sea shelf for more than 150 years.

Currently, large hydrocarbon reserves are being developed on the Russian shelf, the resources of which on the Dagestan shelf are estimated at 425 million tons in oil equivalent (of which 132 million tons of oil and 78 billion m3 of gas), on the shelf of the Northern Caspian Sea - at 1 billion tons of oil .

In total, about 2 billion tons of oil have already been produced in the Caspian Sea.

Losses of oil and its products during production, transportation and use reach 2% of the total volume.

The main sources of pollutants, including petroleum products, entering the Caspian Sea are removal with river runoff, discharge of untreated industrial and agricultural wastewater, municipal wastewater from cities and towns located on the coast, shipping, exploration and exploitation of oil and gas fields. located on the bottom of the sea, oil transportation by sea. Places where pollutants enter with river flow are 90% concentrated in the Northern Caspian, industrial ones are confined mainly to the area of ​​the Absheron Peninsula, and increased oil pollution of the Southern Caspian is associated with oil production and oil exploration drilling, as well as with active volcanic activity (mud) in the area oil and gas bearing structures.

From the territory of Russia, about 55 thousand tons of petroleum products enter the Northern Caspian annually, including 35 thousand tons (65%) from the Volga River and 130 tons (2.5%) from the runoff of the Terek and Sulak rivers.

Thickening of the film on the water surface to 0.01 mm disrupts gas exchange processes and threatens the death of hydrobiota. The concentration of petroleum products is toxic to fish at 0.01 mg/l and to phytoplankton at 0.1 mg/l.

The development of oil and gas resources on the bottom of the Caspian Sea, the forecast reserves of which are estimated at 12–15 billion tons of standard fuel, will become the main factor in the anthropogenic load on the sea ecosystem in the coming decades.

Caspian autochthonous fauna. The total number of autochthons is 513 species or 43.8% of the entire fauna, which include herring, gobies, mollusks, etc.

Arctic species. The total number of the Arctic group is 14 species and subspecies, or only 1.2% of the entire Caspian fauna (mysids, sea cockroach, whitefish, Caspian salmon, Caspian seal, etc.). The basis of the Arctic fauna are crustaceans (71.4%), which easily tolerate desalination and live at great depths of the Middle and Southern Caspian Sea (from 200 to 700 m), since the lowest water temperatures are maintained here throughout the year (4.9– 5.9°C).

Mediterranean species. These are 2 types of mollusks, needle fish, etc. At the beginning of the 20s of our century, the mollusk mytileaster entered here, later 2 types of shrimp (with mullet, during their acclimatization), 2 types of mullet and flounder. Some species entered the Caspian Sea after the opening of the Volga-Don Canal. Mediterranean species play a significant role in the food supply of fish in the Caspian Sea.

Freshwater fauna (228 species). This group includes anadromous and semi-anadromous fish (sturgeon, salmon, pike, catfish, carp, and also rotifers).

Marine species. These are ciliates (386 forms), 2 species of foraminifera. There are especially many endemics among higher crustaceans (31 species), gastropods (74 species and subspecies), bivalves (28 species and subspecies) and fish (63 species and subspecies). The abundance of endemics in the Caspian Sea makes it one of the most unique brackish bodies of water on the planet.

The Caspian Sea produces more than 80% of the world's sturgeon catches, the bulk of which occur in the Northern Caspian Sea.

To increase sturgeon catches, which sharply decreased during the years of falling sea levels, a set of measures is being implemented. Among them are a complete ban on sturgeon fishing in the sea and its regulation in rivers, and an increase in sturgeon factory farming.

The Caspian Sea is the largest lake on Earth, located at the junction of Europe and Asia and called the sea because of its size. The Caspian Sea is an endorheic lake, and the water in it is salty, from 0.05 ‰ near the mouth of the Volga to 11-13 ‰ in the southeast. The water level is subject to fluctuations, currently approximately −28 m below sea level. The area of ​​the Caspian Sea is currently approximately 371,000 km², the maximum depth is 1025 m.

The Caspian Sea is located at the junction of two parts of the Eurasian continent - Europe and Asia. The Caspian Sea is shaped like the Latin letter S, the length of the Caspian Sea from north to south is approximately 1200 kilometers (36°34′ - 47°13′ N), from west to east - from 195 to 435 kilometers, on average 310-320 kilometers (46° - 56° E).

The Caspian Sea is conventionally divided according to physical and geographical conditions into 3 parts - the Northern Caspian, the Middle Caspian and the Southern Caspian. The conditional border between the Northern and Middle Caspian Seas is along the line Chechen (island) - Tyub-Karagansky Cape, between the Middle and Southern Caspian Seas - along the line Zhilaya (island) - Gan-Gulu (cape). The area of ​​the Northern, Middle and Southern Caspian Sea is 25, 36, 39 percent, respectively.

Origin

According to one hypothesis, the Caspian Sea received its name in honor of the ancient tribes of horse breeders - the Caspians, who lived BC on the southwestern coast of the Caspian Sea. Throughout the history of its existence, the Caspian Sea had about 70 names among different tribes and peoples: the Hyrcanian Sea; The Khvalyn Sea or the Khvalis Sea is an ancient Russian name, derived from the name of the inhabitants of Khorezm who traded in the Caspian Sea - Khvalis; Khazar Sea - name in Arabic (Bahr-al-Khazar), Persian (Darya-e Khazar), Turkish and Azerbaijani (Khazar Denizi) languages; Abeskun Sea; Sarayskoye Sea; Derbent Sea; Xihai and other names. In Iran, the Caspian Sea is still called the Khazar or Mazandaran Sea (after the name of the people inhabiting the coastal province of Iran of the same name).

Data

The coastline of the Caspian Sea is estimated at approximately 6,500 - 6,700 kilometers, with islands - up to 7,000 kilometers. The shores of the Caspian Sea in most of its territory are low-lying and smooth. In the northern part, the coastline is indented by water streams and islands of the Volga and Ural deltas, the banks are low and swampy, and the water surface in many places is covered with thickets. The east coast is dominated by limestone shores adjacent to semi-deserts and deserts. The most winding shores are on the western coast in the area of ​​the Absheron Peninsula and on the eastern coast in the area of ​​the Kazakh Gulf and Kara-Bogaz-Gol.

Islands

Large peninsulas of the Caspian Sea: Agrakhan Peninsula, Absheron Peninsula, Buzachi, Mangyshlak, Miankale, Tub-Karagan.

There are about 50 large and medium-sized islands in the Caspian Sea with a total area of ​​approximately 350 square kilometers. The largest islands: Ashur-Ada, Garasu, Gum, Dash, Zira (island), Zyanbil, Kur Dashi, Khara-Zira, Sengi-Mugan, Chechen (island), Chygyl.

Bays

Large bays of the Caspian Sea: Agrakhan Bay, Komsomolets (bay) (formerly Dead Kultuk, formerly Tsesarevich Bay), Kaydak, Mangyshlak, Kazakh (bay), Turkmenbashi (bay) (formerly Krasnovodsk), Turkmen (bay), Gizylagach, Astrakhan ( Bay), Gizlar, Girkan (formerly Astarabad) and Anzali (formerly Pahlavi).

Nearby lakes

On the eastern coast is the salt lake Kara Bogaz Gol, which until 1980 was a bay-lagoon of the Caspian Sea, connected to it by a narrow strait. In 1980, a dam was built separating Kara-Bogaz-Gol from the Caspian Sea, and in 1984 a culvert was built, after which the level of Kara-Bogaz-Gol dropped by several meters. In 1992, the strait was restored, through which water flows from the Caspian Sea to Kara-Bogaz-Gol and evaporates there. Every year, 8-10 cubic kilometers of water (according to other sources - 25 thousand kilometers) and about 150 thousand tons of salt flow into Kara-Bogaz-Gol from the Caspian Sea.

Rivers

130 rivers flow into the Caspian Sea, of which 9 rivers have a delta-shaped mouth. Large rivers flowing into the Caspian Sea are the Volga, Terek (Russia), Ural, Emba (Kazakhstan), Kura (Azerbaijan), Samur (Russian border with Azerbaijan), Atrek (Turkmenistan) and others. The largest river flowing into the Caspian Sea is the Volga, its average annual flow is 215-224 cubic kilometers. The Volga, Ural, Terek and Emba provide up to 88 - 90% of the annual runoff of the Caspian Sea.

Pool

The area of ​​the Caspian Sea basin is approximately 3.1 - 3.5 million square kilometers, which is approximately 10 percent of the world's closed water basin area. The length of the Caspian Sea basin from north to south is about 2500 kilometers, from west to east - about 1000 kilometers. The Caspian Sea basin covers 9 states - Azerbaijan, Armenia, Georgia, Iran, Kazakhstan, Russia, Uzbekistan, Turkey and Turkmenistan.

Cities and states

The Caspian Sea washes the shores of five coastal states:

Russia (Dagestan, Kalmykia and Astrakhan region) - in the west and north-west, coastline length 695 kilometers
Kazakhstan - in the north, northeast and east, the length of the coastline is 2320 kilometers
Turkmenistan - in the southeast, the length of the coastline is 1200 kilometers
Iran - in the south, coastline length - 724 kilometers
Azerbaijan - in the southwest, the length of the coastline is 955 kilometers
The largest city and port on the Caspian Sea is Baku, the capital of Azerbaijan, which is located in the southern part of the Absheron Peninsula and has a population of 2,070 thousand people (2003). Other major Azerbaijani Caspian cities are Sumgait, which is located in the northern part of the Absheron Peninsula, and Lankaran, which is located near the southern border of Azerbaijan. To the southeast of the Absheron Peninsula, there is an oil workers’ settlement called Neftyanye Kamni, whose structures are located on artificial islands, overpasses and technological sites.

Large Russian cities - the capital of Dagestan, Makhachkala, and the southernmost city of Russia, Derbent - are located on the western coast of the Caspian Sea. Astrakhan is also considered a port city of the Caspian Sea, which, however, is not located on the shores of the Caspian Sea, but in the Volga delta, 60 kilometers from the northern coast of the Caspian Sea.

On the eastern shore of the Caspian Sea there is a Kazakh city - the port of Aktau, in the north in the Ural delta, 20 km from the sea, the city of Atyrau is located, south of Kara-Bogaz-Gol on the northern shore of the Krasnovodsk Bay - the Turkmen city of Turkmenbashi, former Krasnovodsk. Several Caspian cities are located on the southern (Iranian) coast, the largest of them is Anzeli.

Dimensions

The area and volume of water of the Caspian Sea varies significantly depending on fluctuations in water levels. At a water level of −26.75 m, the area was approximately 392,600 square kilometers, the volume of water was 78,648 cubic kilometers, which is approximately 44 percent of the world's lake water reserves. The maximum depth of the Caspian Sea is in the South Caspian depression, 1025 meters from its surface level. In terms of maximum depth, the Caspian Sea is second only to Baikal (1620 m) and Tanganyika (1435 m). The average depth of the Caspian Sea, calculated from the bathygraphic curve, is 208 meters. At the same time, the northern part of the Caspian Sea is shallow, its maximum depth does not exceed 25 meters, and the average depth is 4 meters.

The water level in the Caspian Sea is subject to significant fluctuations. According to modern science, over the past 3 thousand years the amplitude of changes in the water level of the Caspian Sea has been 15 meters. Instrumental measurements of the level of the Caspian Sea and systematic observations of its fluctuations have been carried out since 1837, during which time the highest water level was recorded in 1882 (-25.2 m), the lowest in 1977 (-29.0 m) , since 1978 the water level has risen and in 1995 reached −26.7 m; since 1996, a downward trend has emerged again. Scientists associate the reasons for changes in the water level of the Caspian Sea with climatic, geological and anthropogenic factors.

Climate

Water temperature is subject to significant latitudinal changes, most clearly expressed in winter, when the temperature varies from 0 - 0.5 °C at the ice edge in the north of the sea to 10 - 11 °C in the south, that is, the difference in water temperature is about 10 °C. For shallow water areas with depths less than 25 m, the annual amplitude can reach 25 - 26 °C. On average, the water temperature off the west coast is 1 - 2 °C higher than that on the east, and in the open sea the water temperature is 2 - 4 °C higher than on the coasts. Based on the nature of the horizontal structure of the temperature field in the annual cycle of variability, three time periods can be distinguished in the upper 2-meter layer. From October to March, the water temperature increases in the southern and eastern regions, which is especially clearly visible in the Middle Caspian. Two stable quasi-latitudinal zones can be distinguished, where temperature gradients are increased. This is, firstly, the border between the Northern and Middle Caspian, and, secondly, between the Middle and Southern. At the ice edge, in the northern frontal zone, the temperature in February-March increases from 0 to 5 °C, in the southern frontal zone, in the area of ​​the Absheron threshold, from 7 to 10 °C. During this period, the least cooled waters are in the center of the South Caspian Sea, which form a quasi-stationary core. In April-May, the area of ​​minimum temperatures moves to the Middle Caspian Sea, which is associated with faster heating of waters in the shallow northern part of the sea. True, at the beginning of the season in the northern part of the sea a large amount of heat is spent on melting ice, but already in May the temperature here rises to 16 - 17 °C. In the middle part the temperature at this time is 13 - 15 °C, and in the south it increases to 17 - 18 °C. Spring warming of water evens out horizontal gradients, and the temperature difference between coastal areas and the open sea does not exceed 0.5 °C. Warming of the surface layer, which begins in March, disrupts the uniformity of temperature distribution with depth. In June-September, horizontal uniformity in the temperature distribution in the surface layer is observed. In August, which is the month of greatest warming, the water temperature throughout the sea is 24 - 26 °C, and in the southern regions it rises to 28 °C. In August, the water temperature in shallow bays, for example, in Krasnovodsk, can reach 32 °C. The main feature of the water temperature field at this time is upwelling. It is observed annually along the entire eastern coast of the Middle Caspian and partially penetrates even into the Southern Caspian. The rise of cold deep waters occurs with varying intensity as a result of the influence of northwest winds prevailing in the summer season. The wind in this direction causes the outflow of warm surface waters from the coast and the rise of colder waters from the intermediate layers. Upwelling begins in June, but it reaches its greatest intensity in July-August. As a result, a decrease in temperature is observed on the surface of the water (7 - 15 °C). Horizontal temperature gradients reach 2.3 °C on the surface and 4.2 °C at a depth of 20 m. The source of upwelling gradually shifts from 41 - 42° N. in June to 43 - 45° N. in September. Summer upwelling is of great importance for the Caspian Sea, radically changing the dynamic processes in the deep-water area. In open areas of the sea, at the end of May - beginning of June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often it is located between horizons of 20 and 30 m in the middle part of the sea and 30 and 40 m in the southern part. Vertical temperature gradients in the shock layer are very significant and can reach several degrees per meter. In the middle part of the sea, due to the surge off the eastern coast, the shock layer rises close to the surface. Since in the Caspian Sea there is no stable baroclinic layer with a large reserve of potential energy similar to the main thermocline of the World Ocean, then with the cessation of the prevailing winds causing upwelling and with the beginning of autumn-winter convection in October-November, a rapid restructuring of temperature fields to the winter regime occurs. In the open sea, the water temperature in the surface layer drops in the middle part to 12 - 13 °C, in the southern part to 16 - 17 °C. In the vertical structure, the shock layer is eroded due to convective mixing and disappears by the end of November.

Compound

The salt composition of the waters of the closed Caspian Sea differs from the oceanic one. There are significant differences in the ratios of concentrations of salt-forming ions, especially for waters in areas directly influenced by continental runoff. The process of metamorphization of sea waters under the influence of continental runoff leads to a decrease in the relative content of chlorides in the total amount of salts of sea waters, an increase in the relative amount of carbonates, sulfates, calcium, which are the main components in the chemical composition of river waters. The most conservative ions are potassium, sodium, chlorine and magnesium. The least conservative are calcium and bicarbonate ions. In the Caspian Sea, the content of calcium and magnesium cations is almost two times higher than in the Sea of ​​Azov, and the sulfate anion is three times higher. Water salinity changes especially sharply in the northern part of the sea: from 0.1 units. psu in the mouth areas of the Volga and Ural up to 10 - 11 units. psu on the border with the Middle Caspian. Mineralization in shallow salty bays-kultuks can reach 60 - 100 g/kg. In the Northern Caspian, during the entire ice-free period from April to November, a salinity front of a quasi-latitudinal location is observed. The greatest desalination, associated with the spread of river flow across the sea, is observed in June. The formation of the salinity field in the Northern Caspian Sea is greatly influenced by the wind field. In the middle and southern parts of the sea, salinity fluctuations are small. Basically it is 11.2 - 12.8 units. psu, increasing in the southern and eastern directions. With depth, salinity increases slightly (by 0.1 - 0.2 units psu). In the deep-sea part of the Caspian Sea, in the vertical profile of salinity, characteristic deflections of isohalines and local extrema are observed in the area of ​​the eastern continental slope, which indicate the processes of bottom sliding of waters salinizing in the eastern shallow waters of the South Caspian. The magnitude of salinity also strongly depends on sea level and (which is interconnected) on the volume of continental runoff.

General information

The relief of the northern part of the Caspian Sea is a shallow undulating plain with banks and accumulative islands, the average depth of the Northern Caspian Sea is about 4 - 8 meters, the maximum does not exceed 25 meters. The Mangyshlak threshold separates the Northern Caspian from the Middle Caspian. The Middle Caspian is quite deep, the water depth in the Derbent depression reaches 788 meters. The Absheron threshold separates the Middle and Southern Caspian Seas. The Southern Caspian is considered deep-sea; the water depth in the South Caspian depression reaches 1025 meters from the surface of the Caspian Sea. Shell sands are widespread on the Caspian shelf, deep-sea areas are covered with silty sediments, and in some areas there is an outcrop of bedrock.

The climate of the Caspian Sea is continental in the northern part, temperate in the middle and subtropical in the southern part. In winter, the average monthly temperature of the Caspian Sea varies from −8 −10 in the northern part to +8 - +10 in the southern part, in summer - from +24 - +25 in the northern part to +26 - +27 in the southern part. The maximum temperature recorded on the east coast was 44 degrees.

The average annual precipitation is 200 millimeters per year, ranging from 90-100 millimeters in the arid eastern part to 1,700 millimeters along the southwestern subtropical coast. Evaporation of water from the surface of the Caspian Sea is about 1000 millimeters per year, the most intense evaporation in the area of ​​the Absheron Peninsula and in the eastern part of the South Caspian Sea is up to 1400 millimeters per year.

On the territory of the Caspian Sea, winds often blow, their average annual speed is 3-7 meters per second, and northern winds predominate in the wind rose. In the autumn and winter months, winds become stronger, with wind speeds often reaching 35-40 meters per second. The most windy areas are the Absheron Peninsula and the environs of Makhachkala - Derbent, where the highest wave was recorded - 11 meters.

Water circulation in the Caspian Sea is related to runoff and winds. Since most of the drainage occurs in the Northern Caspian Sea, northern currents predominate. An intense northern current carries water from the Northern Caspian along the western coast to the Absheron Peninsula, where the current divides into two branches, one of which moves further along the western coast, the other goes to the Eastern Caspian.

The fauna of the Caspian Sea is represented by 1809 species, of which 415 are vertebrates. 101 species of fish are registered in the Caspian world, where most of the world's sturgeon reserves are concentrated, as well as freshwater fish such as roach, carp, and pike perch. The Caspian Sea is the habitat of fish such as carp, mullet, sprat, kutum, bream, salmon, perch, and pike. The Caspian Sea is also home to a marine mammal - the Caspian seal. Since March 31, 2008, 363 dead seals have been found on the coast of the Caspian Sea in Kazakhstan.

The flora of the Caspian Sea and its coast is represented by 728 species. Among the plants in the Caspian Sea, the predominant algae are blue-green, diatoms, red, brown, characeae and others, and among the flowering plants - zoster and ruppia. In origin, the flora is predominantly of Neogene age, but some plants were brought into the Caspian Sea by humans deliberately or on the bottoms of ships.

(Visited 722 times, 1 visits today)

The Caspian Sea is located on the continent of Eurasia. The surprising thing is that the Caspian Sea, with an area of ​​370 thousand square kilometers, is actually the largest lake, since it has no connection with the ocean. Although it is difficult to call it a lake, because the composition of the water, flora and fauna are similar to those of the sea. The salinity of the water is close to oceanic (from 0.05% to 13%).

Photo: Seagulls on the shores of the Caspian Sea.

About 50 million years ago, the Tethys Sea was located on the territory of Eastern Europe, which, when drying up, was divided into several large bodies of water - the Caspian, Black and Mediterranean seas.

Thanks to mineral waters and healing mud, the Caspian Sea has great recreational and health potential. Therefore, there is an increase in the popularity of the coasts of Turkmenistan, Iran, Azerbaijan and Russian Dagestan among tourists.

Particularly popular is the resort area in the Baku region, where the popular resort in Amburan is located, as well as the area of ​​​​the village of Nardaran, sanatoriums in the villages of Zagulba and Bilgah. In the north of Azerbaijan, the resort in Nabran is gaining popularity.

Unfortunately, tourism in Turkmenistan is poorly developed, which is due to the policy of isolation. And in Iran, Sharia law prohibits foreign tourists from vacationing on the coast.

But if you decide to relax on the Caspian Lake, then you will enjoy walking through protected areas; you will see extraordinary floating islands, various plants and animals that live in fresh and salt waters.

There is a greater variety of ways to have a good time throughout the year. For example, you can go on ship cruises, go fishing or waterfowl hunting, or you can simply enjoy the healing waters, looking at seals and a variety of birds. The protected areas of the sea coast are very beautiful, for example the Astrakhan International Biosphere Reserve and the Volga delta with lotus fields.

A special feature of the Caspian zone is the oriental flavor with hookah and mesmerizing dances. Traditional music will delight your ears, and East Asian cuisine will satisfy your hunger.

See where the Caspian Sea is located on the world map.

Sorry, the card is temporarily unavailable Sorry, the card is temporarily unavailable

Video: Caspian Sea. Storm. 07/08/2012.