The Baltic Sea is a short description for children. The Baltic Sea and problems of its ecology. Reference. Head - Northwestern District

Baltic Sea(Old Russian Varangian, Lith./Lat. Baltijos/Baltijas jūra, Liv. Vālda mer, Est. Läänemeri, Finnish Itämeri, Swiss Östersjön, Dan. Østersøen, German Ostsee, Kashubian Bôłt, Polish Morze Bałtyckie, Bałtyk, Saami Nuortamearra) inland sea of ​​the Atlantic Ocean. It is located off the coast of Northern and Central Europe. It is connected to the North Sea by the Danish Straits. Square- 419 thousand km2, almost equal to the area of ​​the Black Sea (422 thousand km2). The length of the coastline of the Baltic is 7 thousand km. Extreme north point The Baltic Sea is located near the Arctic Circle, the southern one is near Wismar, the western one is in the Flensburg region, and the eastern one is in the St. Petersburg region. The coast is distributed among the countries as follows: Sweden owns 35% of the coast, Finland - 17%, former USSR had 25% of the coast, Russia now has about 7% (about 500 km). The rest belongs to Lithuania, Latvia, Estonia, Poland, Germany, Denmark.

Dominant Depths 40-100 m, maximum - 470 m. The greatest depths are in the north, off the coast of Sweden, on average 60-150 m. The shallowest is considered Curonian Lagoon where depths do not exceed 5 meters. In some areas there are underwater shoals, which greatly complicates navigation.

From the history of the Baltic Sea
It was formed at the site of a large tectonic trough of the earth's crust during the Alpine era of mountain building at the junction of the Baltic crystalline shield with the sedimentary strata of the Russian Platform. After the melting of the ice sheet, there was a vast expanse of water that connected the North Sea with the White Sea. This process began 18-20 thousand years ago. 13 thousand years ago, the glacier finally left the territory of Lithuania. When the ice melted, the water filled the depressions in the Baltic Sea - this is how the cold glacial Baltic Lake was formed, which at different times was connected to the Atlantic Ocean. This lake existed 13-10 thousand years ago.

Somewhat later, the glacier left the Central Swedish lowland. The resulting channel connected the lake with the Atlantic Ocean. With the new arrival of the glacier, the level of the glacial lake began to rise, and with its departure, it dropped by 40 - 50 m. large areas sushi. This is how the Yoldia Sea was formed, which got its name from the abundance of mollusks that lived in it (from lat. Yoldia arctica). The compensatory uplift of the continental plate, which took place in the southern part of the Baltic Sea basin, deprived the Yoldian Sea of ​​communication with the Atlantic Ocean. The rivers have sharply reduced the salinity of this water basin and raised its level. So, 9 thousand years ago, Ancylus Lake was formed (the name comes from the name of the mollusks Ancylus fluviatilis). Its deposits were preserved at a depth of 16-18 m. At this stage of the formation of the Baltic Sea, the climate was warm and dry.

7.5 thousand years ago, the salty waters of the Atlantic Ocean broke into Lake Antsylovo, and the Littorina Sea was formed (the name comes from the name of the mollusks Littorina littoraea). 4 thousand years ago, the Baltic Sea gradually acquired modern look: its salinity has decreased, modern animals and plants begin to predominate.

Salinity
The Baltic Sea is the largest sea in the world with low salt content. Its waters are a mixture of salt water from the ocean and fresh water from numerous rivers. The degree of salinity of the sea in different places has different indicators from each other, which is due to the weak vertical movement of water layers. If in the southwestern part of the sea it is 8%, in the western part 11%, then in the central water area it is 6%, and in the Gulf of Finland, Riga and Bothnia it barely exceeds 2-3% (cf. the average salinity of the World Ocean is 35%o).

The presence of certain fish species in a particular area is also associated with varying degrees of salinity of the water. The flora and fauna of the Baltic Sea have a transitional character from the sea to a freshwater lake. So, often sea shellfish, like oysters, Mua
trunata, Littorina littoralis, etc. are only in the app. parts of the sea where the water is saltier. Along with marine fish, freshwater fish also live in this sea - perch, bream, grayling, whitefish and others. In areas of high salinity and with great depth, cod predominate, different kinds herring, herring, flounder, kalkan, goby, eelpout, sprat. Less often, but still there are salmon - sea trout (trout), whitefish and Baltic salmon (a type of salmon). A lot of three-spined stickleback, small fish. The Aland Islands have seals.

Tidal fluctuations in the Baltic are only a few centimeters. This is due to the fact that the tidal ocean wave, reaching the coast of Denmark, loses its strength by almost 90% or subsides completely. However, the water level in the Baltic Sea changes frequently and abruptly, due to the western and northwestern winds that drive water into the Kaliningrad and Curonian lagoons, as if locking weak river currents in their channels, preventing them from reaching the sea ​​space. If the winds blow from the south and east, the opposite occurs, and in some places the sea moves away from the coast, forming islands of land, interspersed with areas of sandbars. This is also related to fluctuations in water temperatures. In summer, the water temperature is kept in the range from 14° to 20° (sometimes higher, but the average level is 18-19°). warmed up warm water winds that are frequent in these places are driven away from the coast, and bottom, deep currents bring colder layers of water. So in a short time the water temperature can drop to 8-9 °. Summer in the Baltic is not hot, but winter, in turn, is not cold. In winter, the Baltic Sea freezes, but this happens mainly along the coast, where solid ice forms in a small strip or fills the bays, and the Curonian Lagoon freezes earlier than the Kaliningrad Lagoon. It should be noted that the reliability of the ice cover of bays is not the same everywhere, so fishing from such ice is always associated with a certain risk to life. In addition, in some places the ice has large irregularities and has a significant drift speed. Often, cracks and faults can be observed along the coast, especially if windy weather has set in. The heap of ice sometimes takes on bizarre forms, especially if blocks of ice run into rocks or sandbars. Autumn and winter the role of the winds is increasing. South-westerly Atlantic winds carry heat, and long thaws come, accompanied by sleet and rain.
The most dangerous time for fishing - accompanied strong wind. In a word, the wind is the decisive factor that "makes the weather" throughout the Baltic Sea. Winds in Palanga (Lithuania) have interesting names: maritime(western), predominant in this part of the coast; terrestrial- east wind blowing towards the sea; goat- southeast; Finnish- northwestern. And there is more amber wind(Bernsteinwind - German Bernsteinwind) a weakening north-west wind from the sea on the Baltic coast, which, with sea swell, helps to wash out the so-called amber grass from the exposed amber layers and drives algae with amber to the shore. They flow into the Baltic Sea rivers: Neva, Narva, Western Dvina (Daugava), Venta, Neman, Vistula, Oder. Large islands: Bornholm (Denmark), Gotland, Öland (Sweden), Saaremaa, Hiiumaa (Estonia), Rügen, Usedom (Germany), Alandia. bays: Botanical, Finnish, Riga, Curonian.

Gulf of Riga- a bay in the east of the Baltic Sea between Latvia and Estonia. Partially separated from the rest of the sea by the Estonian island of Ezel (Saaremaa). Major cities off the coast of the Gulf of Riga - Riga and Pärnu. In the Gulf of Riga is Estonian island Ruhnu. total area: 16300 km², max. length: 174 km, max. width: 137 km, max. depth: 67 m, flowing rivers : Zap. Dvina (Daugava), Courland Aa (Lielupe), Livonian Aa (Gauja), Salis (Salats).Main ports: St. Petersburg, Kaliningrad (Russia), Tallinn (Estonia), Riga, Ventspils, Liepaja (Latvia), Klaipeda (Lithuania), Gdansk-Gdynia, Szczecin (Poland), Rostock, Kiel, Lübeck (Germany), Copenhagen, Malmö , Stockholm, Luleå, Umeå, Gävle, Sundsval, Hudikval (Sweden), Turku, Helsinki, Rauma, Pori, Vaasa, Kokkola (Finland).

Resorts: Pärnu (Estonia), Jurmala, Liepaja, Pavilosta (Latvia), Palanga, Sventoji, Neringa (Lithuania), Kolobrzeg, Ustka (Poland), Heringsdorf, Warnemünde, Binz (Germany), etc.

The Baltic Sea (from antiquity until the 18th century in Russia it was known as the "Varangian Sea") is an inland marginal sea, deeply protruding into the mainland. The Baltic Sea is located in northern Europe belongs to the Atlantic Ocean basin.

The northernmost point of the Baltic Sea is located near the Arctic Circle, the southernmost point is near the city of Wismar (Germany). The extreme western point is located near the city of Flensburg (Germany), the extreme eastern one is in the region of St. Petersburg. Due to the large elongation along the meridian and the parallel, certain areas of the Baltic Sea are located in different physiographic and climatic zones. This, in turn, affects the oceanological processes occurring in the sea and its individual regions.
Sea area: 415 thousand kilometers. Depth: average - 52 meters, maximum - 459 meters.

The Baltic Sea has three large bays: Bothnian, Finnish, Riga. About 250 rivers flow into it, including the Neva, Vistula, Neman, Daugava, Oder.

The connection of the Baltic Sea with the Atlantic Ocean is carried out through the North Sea, the Skagerrak, Kattegat and Danish Straits (Great and Small Belt, Øresund (Sund) and Fehmarn Belt), however, this connection is difficult due to the shallowness of the straits (depth at the thresholds of 7- 18 meters). Therefore, the waters of the Baltic are very slowly renewed due to the cleaner Atlantic waters. The period of complete water renewal in the Baltic Sea is about 30-50 years.

The Baltic Sea has a low salt content. Its waters are a mixture of salt water from the ocean and fresh water from numerous rivers. The degree of salinity of the sea in different places has indicators that differ from each other, which is due to the weak vertical movement of water layers. If in the southwestern part of the sea it is 8 ppm (i.e., each kilogram of water contains 8 g of salt), in the western part it is 11 ppm, then in the central water area it is 6 ppm, and in the Gulf of Finland, Riga and Bothnia it barely exceeds a mark of 2-3 ppm (the average salinity of the oceans is 35 ppm).

The length of the Baltic coastline is 7 thousand kilometers. The coast is distributed among the countries as follows: Sweden owns 35% of the coast, Finland - 17%, Russia - about 7% (about 500 kilometers). The rest of the coast is divided among themselves by Lithuania, Latvia, Estonia, Poland, Germany, Denmark. The coast of the sea and adjacent land areas are heavily populated and intensively used by humans. On the coast are transport complexes, large industrial enterprises. The Baltic basin accounts for one tenth of the world's maritime traffic.

The Baltic Sea is heavily polluted as a result of the active activities of the people living on its shores. The environmental problems of the Baltic Sea are related to many aspects of society, such as energy production and consumption, industry, forestry, agriculture, fisheries, tourism, transport, wastewater treatment.

Main ecological problems the Baltics

Firstly, the excess supply of nitrogen and phosphorus to the water area as a result of flushing from fertilized fields, municipal wastewater from cities and waste from some enterprises. Since the water exchange of the Baltic is not very active, the concentration of nitrogen, phosphorus and other wastes in the water becomes very strong. Due to nutrients in the sea, organic matter is not completely recycled, and due to a lack of oxygen, they begin to decompose, releasing harmful to marine life hydrogen sulfide. Dead hydrogen sulfide zones already exist at the bottom of the Gotland, Gdansk, and Bornholm depressions.

The second significant problem in the Baltic is water pollution by oil. Thousands of tons of oil annually enter the water area with various effluents. The film of oil that covers the surface of the water mirror does not allow oxygen to pass into the depths. Also, toxic substances harmful to living organisms accumulate on the surface of the water. Oil spills in most cases occur in coastal and shelf zones, the most productive and at the same time vulnerable areas of the sea.

The third problem in the Baltic Sea is the accumulation of heavy metals. Mercury, lead, copper, zinc, cobalt, nickel mainly enter the Baltic waters with atmospheric precipitation, the rest gets through direct discharge into the water area or with river runoff of household and industrial waste. The amount of copper entering the water area is annually about 4 thousand tons, lead - 3 thousand tons, cadmium - about 50 tons, and mercury - 33 tons, per 21 thousand cubic kilometers of the water volume of the water area.

The Baltic Sea, due to its geographical position, has always been at the crossroads historical events. There is more than one ship graveyard at the bottom of the Baltic. Many wrecks carry dangerous goods. The containers in which the goods are located are destroyed over time.

For decades, the Baltic practiced the flooding and disposal of obsolete bombs, shells, chemical munitions. After the end of World War II, by a joint decision of the countries of the anti-Hitler coalition (USSR, Great Britain and the USA) and in accordance with the decision of the Potsdam Conference in 1951, in various parts of the Baltic, as well as in the straits connecting the Baltic Sea with the North Sea, more than 300 thousand tons were flooded German chemical weapons and ammunition.

For more than half a century, ammunition has been lying on the bottom of the Baltic, creating a potential mortal threat. Metal in sea water is corroded by rust, and toxic substances can enter the water at any time.

The material was prepared on the basis of information from open sources

BALTIC SEA (Late Latin - Mare Balticum, among the ancient Slavs - the Varangian Sea or the Sveisky), the inland sea of ​​the Atlantic Ocean, between Scandinavian peninsula and mainland coasts Northwestern Europe. Washes the shores of Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland, Germany, Denmark. In the southwest it is connected to the North Sea by the Danish Straits. maritime border The Baltic Sea passes through the southern entrances of the Øresund, Great Belt and Small Belt straits. The area is 419 thousand km 2, the volume is 21.5 thousand km 3. Greatest depth 470 m. Depths above the thresholds of the Danish Straits: Darser - 18 m, Drogden - 7 m. The cross section above the thresholds is 0.225 and 0.08 km 2, respectively, which limits water exchange with the North Sea. The Baltic Sea juts deep into the Eurasian continent. The heavily indented coastline forms numerous bays and coves. The largest bays: the Gulf of Bothnia, the Gulf of Finland, the Gulf of Riga, the Curonian Lagoon, the Szczecin Bay, the Gulf of Gdansk. The shores of the Baltic Sea in the north are high, rocky, mostly of skerry and fjord types, in the south and southeast they are mostly low-lying, lagoon-type, with sandy and pebble beaches. The largest islands: Gotland, Bornholm, Saaremaa, Muhu, Hiiumaa, Eland, Rügen. There are many small rocky islets - skerries, located along the northern shores (there are over 6 thousand in the Aland Islands group).

relief and geological structure bottom. The Baltic Sea is shallow, lies completely within the shelf, depths up to 200 m occupy 99.8% of its area. The most shallow are the Gulfs of Finland, Bothnia and Riga. These areas of the bottom have a leveled accumulative relief and a well-developed cover of loose sediments. Most of the bottom of the Baltic Sea is characterized by a strongly dissected relief. The bottom of its basin has depressions delimited by elevations and the bases of the islands: in the west - Bornholmskaya (105 m) and Arkonskaya (53 m), in the center - Gotlandskaya (249 m) and Gdanskaya (116 m); to the north of the island of Gotland, the deepest depression - Landsortskaya (up to 470 m) stretches from the northeast to the southwest. Numerous stone ridges, ledges are traced in the central part of the sea - continuations of glints stretching from the northern coast of Estonia to the northern tip of the island of Öland, underwater valleys, glacial-accumulative landforms flooded by the sea.

The Baltic Sea occupies a depression in the west of the ancient East European Platform. The northern part of the sea is located on the southern slope of the Baltic Shield; the central and southern parts belong to a large negative structure of the ancient platform - the Baltic syneclise. The extreme southwestern part of the sea enters the limits of the young Western European platform. The bottom in the north of the Baltic Sea is composed mainly of Precambrian age complexes overlain by a discontinuous cover of glacial and modern marine deposits. Silurian and Devonian sediments take part in the bottom structure in the central part of the sea. The ledges traced here are formed by the Cambrian-Ordovician and Silurian rocks. The Paleozoic complexes in the south are overlain by a thick layer of glacial and marine sediments.

During the last ice age (late Pleistocene), the Baltic Sea depression was completely covered by an ice sheet, after which the Baltic glacial lake. At the end of the late Pleistocene, about 13 thousand years ago, the lake joined the ocean, and the depression was filled with sea water. Communication with the ocean was interrupted in the interval of 9-7.5 thousand years ago, followed by a marine transgression, the deposits of which are known on modern coast the Baltic Sea. Uplift continues in the northern part of the Baltic Sea, at a rate of up to 1 cm per year.

Bottom sediments at depths of more than 80 m are represented by clayey silts, under which banded clay occurs on glacial deposits; at shallower depths, the silt is mixed with sand, in coastal areas sands are common. There are boulders of glacial origin.

Climate. The Baltic Sea is characterized by a temperate maritime climate with continental features. Its seasonal features are determined by the interaction of baric centers: the Icelandic Low and the Azores High in the west and the Siberian High in the east. Cyclonic activity reaches its greatest intensity in the autumn-winter months, when cyclones bring cloudy, rainy weather with strong western and southwestern winds. average temperature air in February from -1.1°С in the south, -3°С in the central part of the sea, to -8°С in the north and east, in the northern part of the Gulf of Bothnia to -10°С. Rarely and for a short time, the cold arctic air penetrating the Baltic Sea lowers the temperature to -35°C. In summer, westerly winds also blow, but of low strength, bringing cool, humid weather from the Atlantic. The air temperature in July is 14-15°C in the Gulf of Bothnia and 16-18°C in the rest of the sea. Rare inflows of warm Mediterranean air cause short-term temperature rises up to 22-24°C. Annual precipitation varies from 400 mm in the north to 800 mm in the south. The greatest number of days with fogs (up to 59 days a year) is observed in the south and in the central part of the Baltic Sea, the smallest (22 days a year) - in the north of the Gulf of Bothnia.

Hydrological regime. The hydrological conditions of the Baltic Sea are determined by its climate, significant inflow of fresh water and limited water exchange with the North Sea. About 250 rivers flow into the Baltic Sea. River flow averages 472 km 3 per year. Most major rivers: Neva - 83.5 km 3, Vistula - 30, Neman - 21, Western Dvina - 20 km 3 per year. Freshwater runoff is unevenly distributed throughout the territory. The Gulf of Bothnia receives 181, the Gulf of Finland - 110, the Gulf of Riga - 37, central part Baltic Sea - 112 km 3 per year. The amount of fresh water coming with precipitation (172 km 3 per year) is equal to evaporation. Water exchange with the North Sea averages 1660 km 3 per year. Fresher waters with a surface runoff flow from the Baltic Sea to the North Sea, salty North Sea water with a bottom current enters through the straits from North Sea. Strong westerly winds usually increase the inflow, east winds - the outflow of water from the Baltic Sea through the Danish straits.

The hydrological structure of the Baltic Sea in most areas is represented by surface and deep water masses separated by a thin intermediate layer. The surface water mass occupies a layer from 20 to (in some places) 90 m, its temperature during the year varies from 0 to 20 ° C, salinity is usually in the range of 7-8‰. This water mass is formed in the sea itself as a result of the interaction sea ​​waters With fresh water atmospheric precipitation and river runoff. It has winter and summer modifications, which differ mainly in temperature. In the warm season, the presence of a cold intermediate layer is noted, which is associated with the summer heating of water on the surface. The deep water mass occupies a layer from 50-100 m to the bottom, its temperature varies from 1 to 15°C, salinity - from 10.0 to 18.5‰. Deep water is formed in the bottom layer as a result of mixing with high salinity water coming from the North Sea. The renewal and ventilation of bottom waters are highly dependent on the inflow of North Sea water, which is subject to interannual variability. With a reduction in the inflow of salt water into the Baltic Sea by great depths and in the depressions of the bottom relief, conditions are created for the appearance of dead events. Seasonal changes in water temperature capture the layer from the surface to 50-60 m and usually do not penetrate deeper.

Wind waves develop especially strongly in autumn and winter with long and strong southwestern winds, when waves 5-6 m high and 50-70 m long are observed. The highest waves are observed in November. In winter, sea ice prevents the development of waves.

In the Baltic Sea, cyclonic (counterclockwise) water circulation is everywhere, complicated by eddy formations of different scales. The velocities of constant currents are usually about 3-4 cm/s, but in some areas they sometimes increase to 10-15 cm/s. Due to the low velocities of the current, they are unstable, their pattern is often disturbed by the action of winds. Storm winds cause strong wind currents with speeds of up to 150 cm/s, which quickly fade after a storm.

The tides in the Baltic Sea are weakly expressed due to a slight connection with the ocean, the height is 0.1-0.2 m. The surge fluctuations in the level reach significant values ​​(at the tops of the bays up to 2 m). The combined action of the wind and sudden changes in atmospheric pressure cause seiche level fluctuations with a period of 24-26 hours. The magnitude of such fluctuations is from 0.3 m in the open sea to 1.5 m in the Gulf of Finland. Seiche waves with surge western winds sometimes cause a rise in the level at the top of the Gulf of Finland up to 3-4 m, which delays the flow of the Neva and leads to floods in St. Petersburg, sometimes catastrophic: in November 1824, about 410 cm, in September 1924 - 369 cm

The water temperature on the surface of the Baltic Sea varies greatly from season to season. In August in the Gulf of Finland the water warms up to 15-17°С, in the Gulf of Bothnia 9-13°С, in the central part of the sea 14-18°С, in the southern regions it reaches 20°С. In February, in the open part of the sea, the water temperature on the surface is 1-3°C, in bays and bays below 0°C. The salinity of water on the surface is 11‰ at the outlet of the Danish Straits, 6-8‰ in the central part of the sea, 2‰ and less at the tops of the Gulf of Bothnia and the Gulf of Finland.

The Baltic Sea belongs to the so-called brackish basins, in which the temperature of the highest density is above the freezing point, which leads to an intensification of the process of sea ice formation. Ice formation begins in November in the bays and along the coast, later - in the open sea. IN harsh winters ice cover covers the entire northern part seas and coastal waters of its central and southern parts. The thickness of landfast (fixed) ice reaches 1 m, drifting - from 0.4 to 0.6 m. Ice melting begins at the end of March, spreads from southwest to northeast and ends in June.

Research History. The first information about the exploration of the Baltic Sea is associated with the Normans. In the middle of the 7th century they penetrated into the Gulf of Bothnia, discovered the Aland Islands, in the 2nd half of the 7th-8th centuries they reached west coast The Baltics discovered the Moonsund archipelago, for the first time penetrated the Gulf of Riga, in the 9th-10th centuries they used the coast from the mouth of the Neva to the Gdansk Bay for trade and piracy. Russian hydrographic and cartographic work began in the Gulf of Finland in the early 18th century. In 1738, F. I. Soymonov published an atlas of the Baltic Sea, compiled from Russian and foreign sources. In the middle of the 18th century, A. I. Nagaev conducted many years of research, who compiled a detailed sailing chart of the Baltic Sea. The first deep-sea hydrological studies in the mid-1880s were carried out by S. O. Makarov. Since 1920, hydrological work has been carried out by the Hydrographic Department of the Navy, the State Hydrological Institute (Leningrad), and since the 2nd half of the 20th century, extensive comprehensive research has been launched under the guidance of the Leningrad (St. Petersburg) Branch of the State Oceanographic Institute of the Russian Academy of Sciences.

Economic use. Fish resources consist of freshwater species that live in the fresh waters of the bays (crucian carp, bream, pike, pike perch, chub), the Baltic salmon herd and pure marine species, distributed mainly in the central part of the sea (cod, herring, smelt, vendace, sprat). Baltic herring, sprat, herring, smelt, river flounder, cod, perch and others are fished. Unique object fishing - eel. Placers of amber are common on the coast of the Baltic Sea, mining is carried out near Kaliningrad (Russia). Oil reserves have been discovered at the bottom of the sea, and industrial development has begun. Iron ore is mined off the coast of Finland. The significance of the Baltic Sea as a transport artery is great. Large volumes of liquid, bulk and general cargo are transported across the Baltic Sea. A significant part of the foreign trade of Denmark, Germany, Poland, Russia, Lithuania, Latvia, Estonia, Finland, Sweden is carried out through the Baltic Sea.

The cargo turnover is dominated by oil products (from the ports of Russia and from the Atlantic Ocean), coal (from Poland, Russia), timber (from Finland, Sweden, Russia), pulp and paper (from Sweden and Finland), iron ore (from Sweden); An important role is also played by machinery and equipment, the major producers and consumers of which are the countries located on the shores and in the basin of the Baltic Sea. Major ports Baltic Sea: St. Petersburg, Kaliningrad (Russia), Tallinn (Estonia), Riga (Latvia), Gdansk, Gdynia, Szczecin (Poland), Rostock - Warnemünde, Lubeck, Kiel (Germany), Copenhagen (Denmark), Malmö, Stockholm , Lulea (Sweden), Turku, Helsinki, Kotka (Finland). In the Baltic Sea, maritime passenger and ferry traffic: Copenhagen - Malmö, Trelleborg - Sassnitz (rail ferries), Nortelje - Turku (car ferry), etc. On the southern and southeast coasts many resorts.

Ecological state. The Baltic Sea, which has a difficult water exchange with the World Ocean (water renewal lasts about 30 years), is surrounded by industrialized countries and is experiencing an extremely intense anthropogenic load. The main environmental problems are related to the burial of chemical weapons at the bottom of the sea, the discharge of sewage into the sea major cities, washing off chemical fertilizers used in agriculture, and especially with shipping - one of the most intensive in the world (mainly oil tankers). After the entry into force in 1980 of the Convention for the Protection of the Marine Environment of the Baltic Sea ecological situation improved due to the commissioning of a large number of wastewater treatment plants, reducing the use of chemical fertilizers, monitoring the technical condition of ships. The concentration of toxic substances such as DDT and polychlorinated biphenyls, petroleum hydrocarbons has decreased. The content of dioxins in the Baltic herring is 3 times lower than the MPC, the gray seal population has recovered. The issue of giving the Baltic Sea the status of a particularly vulnerable sea area is being considered.

Lit.: Terms. Concepts. Reference tables. M., 1980; Hydrometeorological conditions of the shelf zone of the seas of the USSR. L., 1983. T. 1. Issue. 1: Baltic Sea without bays; Atlantic Ocean. L., 1984; biological resources Atlantic Ocean. M., 1986; Pushcharovsky Yu. M. Tectonics of the Atlantic with elements of nonlinear geodynamics. M., 1994; Hydrometeorology and hydrochemistry of the seas of the USSR. SPb., 1994. T. 3. Issue. 2; Zalogin B. S., Kosarev A. N. Morya. M., 1999.

Heavily cut into the mainland. Its not as severe as the climate of the Arctic seas, although the Baltic Sea is located in the northwestern part of Russia. This sea is almost completely limited by land. Only from the southwest is this sea connected to the waters by various straits. The Baltic Sea belongs to the type of inland seas.

The shores that this sea washes have a different origin. Quite complicated and. The Baltic Sea has a rather small depth, due to the fact that it is located within the boundaries of the continental shelf.

The greatest depth of the Baltic Sea was recorded in the Landsort Basin. The Danish Straits are characterized by shallow depths. The depth of the Great Belt is 10 - 25 m, the Small Belt - 10 - 35 m. The waters of the Sound have a depth of 7 to 15 m. The shallow depths of the straits interfere with the unhindered exchange of water between the Baltic Sea and. The Baltic Sea covers an area equal to 419 thousand km2. The volume of water is 321.5 km3. The average water depth is about 51 m. The maximum sea depth is 470 m.

The climate of the Baltic Sea is influenced by its location in the zone of temperate latitudes, the proximity of the Atlantic Ocean and the location of a large part of the sea inside the mainland. All these factors contribute to the fact that the climate of the Baltic Sea is in many ways close to the maritime climate of temperate latitudes, and there are also some features of the continental climate. Due to the relatively large extent of the sea, there are some distinctive features climate in different parts of the sea.

In the Baltic, it is largely due to the influence of the Icelandic low, the Siberian and. Depending on whose influence is dominant, seasonal features differ. In autumn and winter, the Baltic Sea is influenced by the Icelandic Low and the Siberian High. As a result of this, the sea is in power, which spread in autumn from west to east, and in winter to the northeast. This period is characterized by cloudy weather with large southwestern and western winds.

In January and February, when the lowest is observed, average monthly temperature in the central part of the sea is - 3°C, and in the north and east - 5 - 8°C. With the strengthening of the Polar High, cold ones enter the Baltic Sea. As a result, it drops to – 30 – 35°C. But such cold snaps are quite rare and, as a rule, they are short-lived.

In the spring-summer period, the Siberian High loses its strength, and the Azores and, to a lesser extent, the Polar High have a dominant effect on the Baltic Sea. At this time, the sea is observed. Cyclones coming to the Baltic from the Atlantic Ocean are not as significant as in winter. All this causes the unstable direction of the winds, which have low speeds. In the spring season, northerly winds have a great influence on the weather, they bring cold air.

In summer, winds from the western and northwestern directions prevail. These winds are predominantly weak or. Due to their influence, cool and humid weather is observed in summer. The average July temperature reaches + 14 - 15°С in the Gulf of Bothnia and +16 - 18°С in other areas of the sea. Very rarely, warm air masses enter the Baltic, which cause hot weather.

The temperature of the waters of the Baltic Sea depends on the specific location. In winter, the water temperature near the coast is lower than in the open sea. In the western part, the sea is warmer than in the eastern part, which is associated with the cooling effect of the land. In summer, the coldest waters are near the western coasts in the central and southern zones of the sea. Such a distribution of temperatures is due to the fact that the western ones move the heated upper waters from the western shores. Their place is taken by cold deep waters.

Coast of the Baltic Sea

Approximately 250 large and small rivers carry their waters into the Baltic Sea. During the year they give the sea about 433 km 3, which is 2.1% of the total volume of the sea. The most full-flowing are: the Neva, which pours 83.5 km 3 per year, the Vistula (30.4 km 3 per year), the Neman (20.8 km 3 per year) and the Daugava (19.7 km 3 per year). In different areas of the Baltic Sea, the proportion is not the same. For example, in the Gulf of Bothnia, rivers give 188 km 3 per year, the volume of continental waters is 109.8 km 3 / year. The Gulf of Riga receives 36.7 km 3 /year and in the central part of the Baltic is 111.6 km 3 /year. Thus, the eastern regions of the sea receive more than half of all continental waters.

During the year, rivers bring an unequal amount of water to the sea. If the full flow of rivers is regulated by a lake, as, for example, near the Neva River, then a greater flow occurs in the spring-summer period. If the full flow of rivers is not regulated by lakes, as, for example, near the Daugava River, then the maximum flow is noted in spring and a slight increase in autumn.

are practically not observed. The current affecting surface water, occurs under the influence of winds and river runoff. In winter, the waters of the Baltic Sea are covered with ice. But during one and the same winter, the ice can melt several times and again bind the waters. This sea is never completely covered with ice.

Fishing is widely developed in the Baltic Sea. Baltic herring, sprat, cod, whitefish, lamprey, salmon and other types of fish are caught here. Also in these waters, a large amount of algae is mined. There are many marine farms on the Baltic Sea where the most sought-after fish species are grown. There are a large number of placers on the coast of the Baltic Sea. Amber mining works are carried out in the region. There is oil in the bowels of the Baltic Sea.

Navigation is widely developed in the waters of the Baltic Sea. Sea transportation of various goods is constantly carried out here. Thanks to the Baltic Sea, it maintains close economic and trade relations with Western European countries. There are a large number of ports on the coast of the Baltic Sea.