| Abstract |
The Caspian Sea is inland and is located in an extensive continental depression on the border of Europe and Asia. The Caspian Sea has no connection with the ocean, which formally allows us to call it a lake, but it has all the features of the sea. It is elongated in the meridional direction and is located between 47 degrees. 07 minutes and 36 degrees. 33 minutes s.sh. and 45 degrees. 43 minutes and 54 degrees. 03 minutes v.d. The length of the sea along the meridian is about 1200 km, the average width is 310 km. The sea area at a level mark of 27.5 m BS is 386.4 thousand km.
textPhysically and geographically and according to the nature of the underwater relief, the sea is divided into three parts: northern, middle, and southern. The conditional border between the northern and middle parts runs along the line of Chechen Island - Cape Tyub-Karagan, between the middle and southern parts - along the line of Chechen Island. Residential - M. Kuuli.
The northern part of the sea is shallow, its average depth is 5 - 6 m, maximum depths of 15 - 20 m are located on the border with the middle part of the sea. The bottom relief is complicated by the presence of banks, islands, Borozdin.
The middle part of the sea is a separate basin, the area of the maximum depths of which - the Derbent depression - is shifted to the western coast. The average depth of this part of the sea is 190 m, the greatest is 788 m. The western slope of the Derbent depression is narrow and steep, the eastern slope is strongly stretched. The bottom of the depression is a slightly sloping plain with depths mainly from 400 to 600 m.
The southern part of the sea is separated from the middle Absheron threshold, which is a continuation of the Main Caucasian ridge. The depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian Basin with a maximum depth of 1025 m for the sea is located east of the Kura delta. Several underwater ridges up to 500 m high rise above the bottom of the basin.
Meteorological conditions in different parts of the Caspian Sea are not the same due to its large meridional length. The northern part of the sea is characterized by the prevalence of east and south-east winds for most of the year. In the middle part, winds of the northwestern and southeastern directions prevail, in the area of the Absheron Peninsula due to the orographic effect - the winds of the northern and southern directions. In the southern part of the sea, north and north-east winds prevail in the south-west, north-west winds prevail in the extreme south-east in winter, and south-east in summer.
Strong and stormy winds, mainly of northwestern and southeastern directions, are observed most often in spring and winter near the western coast of the Middle Caspian, especially in the area of the Absheron Peninsula.
Average annual air temperatures vary from 10 degrees C in the northern part of the sea to 17 degrees C in the south. The coldest month is January, the warmest are July and August.
The distribution of precipitation over the sea area is extremely uneven. At the western coast of the southern part of the sea, it ranges from 65 (Oil Rocks) to 1250 mm per year (Lankaran zone). North of the Absheron Peninsula, the amount of precipitation is 400 - 430 mm. The eastern coast is dry, the maximum amount of precipitation does not exceed 15 - 20 mm.
Ice appears in the northern part of the sea every November. In severe winters, the entire water area of the northern part is covered with ice; in mild winters, the ice stays in shallow water within the 2 - 3 meter isobath. The appearance of ice in the middle and southern parts of the sea occurs in December - January.
The water temperature is subject to latitudinal changes, most pronounced in winter, when the temperature changes from 0 - 0.5 degrees C at the ice edge in the north of the sea to 10 - 11 degrees C in the south, i.e. the difference in water temperature is about 10 degrees C. The summer period is characterized by horizontal uniformity in the temperature distribution in the surface layer: in the middle part of the sea 24 - 25 degrees C, in the southern part 25 - 26 degrees C, in the southeast up to 27 - 28 degrees. C. The maximum water temperature is observed in August. Seasonal changes in water temperature are noticeable in the upper 100-meter layer. In the bottom layers of the sea, the temperature during the year is about 4.5 degrees C in the middle part and 5.8 - 5.9 degrees. From the south.
The salinity of water changes especially sharply in the northern part of the sea: from 0.1 ‰ in the mouth areas of the Volga and the Urals to 10 -11 ‰ on the border with the Middle Caspian. In the middle and southern parts of the sea, salinity fluctuations are small. Basically, it is 12.6 - 13.0 ‰, increasing from north to south and from west to east. Salinity increases insignificantly with depth (by 0.1 - 0.2.).
The level of the Caspian Sea is subject to significant fluctuations due to changes in the water balance and, above all, in the Volga runoff. During the historical time, sea level has undergone significant fluctuations, continuing in modern conditions. The annual course of the level is characterized by a maximum in June - July and a minimum in February. The range of intra-annual fluctuations is 30 - 35 cm. Surge fluctuations of the level are manifested throughout the sea, but they are most significant in the shallow northern part, where, with maximum surges, the level can increase by 2.0 - 4.5 m, with surges, decrease by 1, 0 - 2.5 m. |