Reverse flow in the Baltic Sea. Svetlovodsk and Zelenogradsk are the best Russian resorts. Climatic conditions of the Baltic

Bottom relief

Hydrological regime

Compared to other seas, the waves in the Baltic Sea are insignificant. In the center of the sea there are waves up to 3.5 meters high, sometimes higher than 4 meters. In shallow bays, the wave height does not exceed 3 meters, but they are steeper. However, it is not uncommon for the formation big waves, with a height of more than 10 meters, in conditions when storm winds form waves going from deep water areas to shallow water. For example, in the area of ​​the Elands-Sedra-Grunt bank, a wave height of 11 meters was instrumentally recorded. The low salinity of the surface layer contributes to a rapid change in the state of the sea. In winter navigation conditions, ships are threatened by icing. These features of the Baltic, along with a high level of shipping, big amount navigational hazards make navigation in this sea a difficult task. The transparency of water decreases from the center of the sea to its shores. The most transparent water in the center of the sea and the Gulf of Bothnia, where the water has a bluish-green color. In coastal areas, the color of the water is yellow-green, sometimes brownish. The lowest transparency is observed in summer due to the development of plankton. Sea ice first appears in the bays in October - November. Coast of Bothnia and a significant part of the coast (except south coast) of the Gulf of Finland are covered with fast ice up to 65 centimeters thick. The central and southern parts of the sea are usually not covered with ice. The ice melts in April, although in the north of the Gulf of Bothnia, drifting ice can occur in June. Floating bottom ice is often found.

Temperature regime

The temperature of the surface layers of water in summer Gulf of Finland is 15-17 °C, in the Gulf of Bothnia - 9-13 °C, in the center of the sea - 14-17 °C. With increasing depth, the temperature slowly decreases to the depth of the thermocline (20-40 meters), where there is a sharp jump to 0.2-0.5 ° C, then the temperature rises, reaching 4-5 ° C at the bottom.

Salinity

The Baltic Sea washes nine countries: Latvia, Lithuania, Estonia, Russia, Poland, Germany, Finland, Sweden and Denmark.

The coastline of the sea is 8.000 km. , and the area of ​​the sea is 415.000 sq. km.

It is believed that the sea was formed 14,000 years ago, but in the modern outline of the boundaries there are 4,000 years.

The sea has four bays, the largest Bothnian(washes Sweden and Finland), Finnish(washes Finland, Russia and Estonia), Riga(washes Estonia and Latvia) and freshwater Curonian(washes Russia and Lithuania).

Salinity of waters oceans, is the main feature that distinguishes them from the waters of the land.

In oceanology, deer sea water defined as the total amount of solids in grams (all substances dissolved in water, not just salts) dissolved in 1 kg of sea water, provided that all halogens are replaced by an equivalent amount of chlorine, all carbonates are converted to oxides, organic matter is burned. Salinity measured in "‰" ("ppm").

The average salinity of the world's oceans is 35 ‰. , that is, in 1 kg of sea water, an average of 35 grams of various substances are dissolved. The standard is a water sample taken in Bay of Biscay, with salinity close to 35 ‰. It is used to calibrate instruments.

The salinity of sea waters is of ancient origin; salts entered the ocean water simultaneously with the emergence of the oceans themselves. During the formation of the earth's crust, which occurred at high temperatures, various substances were released from the earth into the atmosphere in the form of gases. The subsequent cooling of the earth's crust caused heavy rains. They took those substances with them and filled huge pits on the surface of the earth.

The salinity of the ocean waters is not the same everywhere. Salinity is influenced by the following processes:

1.Evaporation of water.

2. Formation of ice.

3. Precipitation.

4. Stock river waters.

5. Melting ice.

At the same time, evaporation and ice formation contribute to an increase in salinity, while precipitation, river water runoff, and melting ice lower it.

The influence of biochemical processes on salinity is negligible.

Water mixing (diffusion) and advection of salts by currents are also involved in the formation of salinity. The salinity of deep and near-bottom waters is determined exclusively by these 2 processes, since there are no internal sources and sinks of salts at depths and at the bottom of the ocean.

The main role in the change in salinity belongs to evaporation and precipitation. Therefore salinity surface layers, as well as temperature, depends on the climatic conditions associated with geographical location seas.

The Red Sea is the saltiest sea in the world's oceans. Its salinity reaches 42 ‰. This is due to its location in tropical latitudes. There is very little atmospheric precipitation here, the evaporation of water from strong heating by the sun is very large. The water evaporates from the sea, but the salt remains. Not a single river flows into the Red Sea, and the only source of replenishment of the water balance is the flow of water from Gulf of Aden. Approximately 1,000 cubic meters of gas is brought into the sea through the Bab el-Mandeb Strait during the year. km of water is more than is taken out of it. According to calculations, it takes 15 years for the complete exchange of the waters of the Red Sea.

The water in the Red Sea is evenly mixed throughout the year. In winter, surface waters cool down, become denser and sink down, and rise up warm waters from depth. In summer, water evaporates from the surface of the sea, and the rest becomes more salty, heavy and sinks down. Less salty water rises in its place. Therefore, the Red Sea is the same in temperature and salinity throughout its volume.

Hot brine troughs have also been found in the Red Sea. Currently, more than 20 such depressions are known. The depressions are heated from below by the internal heat of the Earth. The brines in the depressions do not merge with the surrounding water, but are clearly distinguished from it and look like muddy ground covered with ripples, or like swirling fog. The content of many metals, including precious ones, in the brines of the Red Sea is hundreds and thousands of times higher than in ordinary sea water.

The absence of river runoff and rain streams, and hence dirt from land, ensures the transparency of the Red Sea water and the constancy of its salinity.

In the Baltic Sea, water forms layers of different salinity. The average salinity of the Baltic Sea is not higher than 1%o, and that of its surface waters is -5-8°/oo. This is due to the fact that this sea is located in climate zone, where there is less evaporation, but drops out more precipitation. In coastal areas for salinity big influence renders river runoff, and in the polar regions - the processes of formation and melting of ice. When water freezes and sea ice builds up, part of the salts drain into the water and salinity increases; when melting sea ​​ice and icebergs, it is decreasing. Fresh water enters the Baltic Sea from 250 rivers, while salt water enters only from the narrow Danish straits. As a result, salinity is highest in
Southwest of the Baltic, and decreases as you move to the east. However, the overall picture can be disturbed by currents.

Salty waters, falling into the Baltic Sea, sink to the bottom, forming a highly saline layer there. At depths of 70-80 meters, the salt content increases dramatically. This jump is called a halocline. A halocline occurs where the movements of the water mass caused by storms cease to reach.
Dead organic matter constantly sinks to the bottom of the sea. About once every 15 years, such large masses of water enter the Baltic Sea from the North Sea that stagnant water is pushed aside. The stagnant waters pushed into the northern and deepest parts of the Baltic gradually mix with the surrounding water there. At the beginning of the movement of stagnant waters, an increase in the salinity of the waters of the Baltic Sea occurs.

Baltic Sea(also called East Sea) is considered an inland sea that penetrates deep into the continent.

The northern extreme point of the Baltic Sea is located near the Arctic Circle, the southern one is near the German city of Wismar, the western one is near the city of Flensburg, and the eastern one is near St. Petersburg. This sea belongs to the ocean.

General information about the Baltic

The area of ​​the sea (excluding islands) is 415 km. sq. It washes the shores of such states:

• Estonia;
• Russia;
• Lithuania;
• Germany;
• Latvia;
• Poland
• Latvia;
• Denmark;
• Finland;
• * Sweden.

Large bays are: Bothnian, Finnish, Riga, Curonian (separated by a scythe). The largest islands: Eland, Wolin, Aland, Gotland, Als, Saaremaaa, Muhu, Men, Usedom, Fore and others. Most big rivers: Zapadnya Dvina, Neva, Vistula, Venta, Narva, Pregolya.

The Baltic Sea through the Volga-Baltic basin comes to and is located on the continental shelf. In the area of ​​islands, shoals and banks, the depth varies within 12 meters. There are a couple of basins where the depth reaches 200 meters. The Landsort basin is considered the deepest (470 meters), the basin depth reaches 250 meters, and in the Gulf of Bothnia - 254 meters.

IN southern region the seabed is flat, and in the north it is predominantly rocky. A huge part of the bottom is covered with deposits of glacial origin of various colors (green, brown, black).

A feature of the Baltic Sea is that there is an excess of fresh water here, which is formed due to river runoff and precipitation.

Its surface brackish waters constantly go into. During storms, the exchange between these seas changes, as in the straits the water mixes from the bottom. The salinity of the sea is on the wane from the Danish Straits (20 ppm) to the east (in the Gulf of Bothnia 3 ppm, and in Finland - 2 ppm). Tides can be diurnal and semidiurnal (do not exceed 20 cm).

Compared to other seas, the disturbances of the Baltic Sea are quite insignificant. In the central parts of the sea, waves can reach 3-3.5 meters, less often - 4 meters. During large storms, waves 10-11 meters high were recorded. The most transparent water with a bluish-green tint is observed in the Gulf of Bothnia, in coastal areas it is more turbid and has a yellowish-green color. Due to the development of plankton, the lowest water transparency can be traced in summer. soils coastal zone varied: in southern regions- sand, in the east - silt and sand, and on the north coast - stone.

Climate of the Baltic Sea

The sea temperature is generally lower than in other seas. On mornings in the summer, due to southerly winds that drive the upper warm layers into the ocean, the temperature sometimes drops below 12 degrees. When they start to blow northern winds, surface waters become much warmer. The highest temperature is in August - about 18 C. In January, it varies from 0 to 3 C.

Due to low salinity, harsh winters and shallow depths, the Baltic Sea often freezes over, although not every winter.

Flora and fauna

The water in the Baltic Sea changes from sea salt to fresh water. Marine mollusks live only in the western region of the sea, where the water is saltier. Of the fish, sprat, cod, herring are represented here. Smelt, vendace salmon and others are found in the Gulf of Finland. Near Åland Islands seals live.

Due to the presence of many islands, rocks, reefs in the sea, navigation in the Baltic Sea is quite dangerous. This danger is somewhat reduced due to the presence of a large number of lighthouses here (most of them). The largest cruise ships leave the Danish straits and enter the Atlantic Ocean. The most difficult place is the Great Belt Bridge. The largest ports: Tallinn, Baltiysk, Lubeck, Riga, Stockholm, Szczecin, Rostock, Kiel, Vyborg, Gdansk, St. Petersburg;

• Ptolemy called this sea the Venedian, which comes from the name of the Slavic peoples who lived in ancient times in the southern part of the coast - Wends or Wends;
• The famous route from the Varangians to the Greeks ran across the Baltic Sea;
• The Tale of Bygone Years calls him by the Varangian Sea;
• The name "Baltic Sea" is found for the first time in the treatise of Adam of Bremen in 1080;
• This sea is rich in oil, manganese, iron and amber. The Nord Stream gas pipeline runs along its bottom;
• Every year March 22 is the day of protection environment the Baltic Sea. This decision was taken by the Helsinki Commission in 1986.

Resorts

Among the resorts of the Baltic Sea, the most famous are: Zelenogorsk, Svetlogorsk, Zelenogradsk, Pioneer (Russia), Saulkrasti and

The Baltic Sea is connected to the North Sea by the Øresund Straits. (Sound), large and small Belts, Kattegat and Skagerrak. Washes the shores of Russia, Estonia, Latvia, Lithuania, Poland, Germany, Denmark, Sweden, Finland.

The maritime boundary of the Baltic Sea runs along the southern entrances of the Øresund straits, the Greater and Lesser Belta. The area is 386 thousand km². The average depth is 71 m. The shores of the Baltic Sea in the south and Yu.-V. predominantly low-lying, sandy, lagoon type; from the land side - dunes covered with forest, from the sea side - sandy and pebble beaches. In the north, the shores are high, rocky, mostly of the skerry type. The coastline is strongly indented, forming numerous bays and coves.

The largest bays: Bothnian (according to physical and geographical conditions, it is the sea), Finnish, Riga, Curonian, Gdansk Bay, Szczecin, etc.

Islands of the Baltic Sea mainland origin. There are many small rocky islets - skerries, located along the northern shores and concentrated in the groups of the Vasi and Aland Islands. The largest islands: Gotland, Bornholm, Sarema, Muhu, Khiuma, Eland, Rügen, etc. It flows into the Baltic Sea a large number of rivers, the largest of which are the Neva, Western Dvina, Neman, Vistula, Odra, etc.

The Baltic Sea is a shallow shelf sea. Depths of 40-100 m predominate. The most shallow water areas are the Kattegat straits. (average depth 28 m), Øresund, large and small belts, the eastern parts of the Gulf of Finland and the Gulf of Bothnia and the Gulf of Riga. These areas of the sea 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, there are relatively deep basins: the Gotland (249 m), Bornholmskaya (96 m), in the Södra-Kvarken Strait (244 m) and the deepest - Landsortsjupet south of Stockholm (459 m). There are numerous stone ridges, ledges are traced in the central part of the sea - continuations of the Cambrian-Ordovician (from north coast Estonia to the northern tip of the island of Öland) and Silurian glints, underwater valleys, glacial-accumulative landforms flooded by the sea.

The Baltic Sea occupies a depression tectonic origin, which is a structural element of the Baltic Shield and its slope. According to modern concepts, the main irregularities of the sea bottom are due to block tectonics and structural denudation processes. The latter, in particular, owe their origin to the underwater ledges of the glints. Northern part The bottom of the sea is composed mainly of Precambrian rocks overlain by a discontinuous cover of glacial and recent marine sediments.

In the central part of the sea, the bottom is composed of Silurian and Devonian rocks, hidden to the south under a layer of glacial and marine sediments of considerable thickness.

The presence of underwater river valleys and the absence of marine sediments under the glacial deposits indicate that in the pre-glacial period there was land on the site of the Baltic Sea. During at least the last ice age, the basin of the Baltic Sea was completely occupied by ice. Only about 13 thousand years ago there was a connection with the ocean, and sea ​​waters filled a hole; formed the Yoldian Sea (for the mollusc Joldia). The phase of the Yoldian Sea is somewhat earlier (15 thousand years ago) preceded by a phase of the Baltic glacial lake not yet in contact with the sea. About 9-7.5 thousand years ago, as a result of tectonic uplift in Central Sweden the connection of the Yoldian Sea with the ocean ceased, and the Baltic Sea again became a lake. This phase of the development of the Baltic Sea is known as Lake Ancylus. (for the mollusc Ancylus). A new land subsidence in the region of the modern Danish straits, which occurred about 7-7.5 thousand years ago, and extensive transgression led to the resumption of communication with the ocean and the formation of the Littorina Sea. The level of the last sea was several meters higher than the modern one, and the salinity was higher. Littorina transgression deposits are widely known on modern coast the Baltic Sea. The secular rise in the northern part of the Baltic Sea basin continues now, reaching 1 m per hundred years in the north of the Gulf of Bothnia and gradually decreasing to the south.

The climate of the Baltic Sea is maritime temperate, strongly influenced by the Atlantic Ocean. It is characterized by relatively small annual temperature fluctuations, frequent precipitation, fairly evenly distributed throughout the year, and fog during the cold and transitional seasons. During the year, westerly winds prevail, which are associated with cyclones coming from the Atlantic Ocean. Cyclonic activity reaches its highest intensity in the autumn-winter months. At this time, cyclones are accompanied by strong winds, frequent storms and cause large rises in water levels off the coast. In the summer months, cyclones weaken and their frequency decreases. The invasion of anticyclones is accompanied by easterly winds.

The stretching of the Baltic Sea by 12° along the meridian determines the noticeable differences in the climatic conditions of its individual regions. average temperature air of the southern part of the Baltic Sea: in January -1.1°C, in July 17.5°C; middle part: in January -2.3°C, in July 16.5°C; Gulf of Finland: in January -5°C, in July 17°C; northern part of the Gulf of Bothnia: in January -10.3°C, in July 15.6°C. Cloudiness in summer about 60%, in winter more than 80%. The average annual rainfall in the north is about 500 mm, in the south over 600 mm, and in some areas up to 1000 mm. The largest number of days with fog falls on the southern and middle parts of the Baltic Sea, where it reaches an average of 59 days a year, the smallest - in the north. Gulf of Bothnia (up to 22 days a year).

The hydrological conditions of the Baltic Sea are determined mainly by its climate, abundance of fresh water and water exchange with the North Sea. An excess of fresh water, equal to 472 km3 per year, is formed due to continental runoff. The amount of water entering in precipitation (172.0 km³ per year) is equal to evaporation. Water exchange with the North Sea averages 1659 km3 per year (salt water 1187 km³ per year, fresh water - 472 km³ per year). Fresh water flows from the Baltic Sea to the North Sea in a runoff current, salty water flows through the straits from the North Sea to the Baltic Sea through the deep current. Strong westerly winds usually cause influx and east winds- the flow of water from the Baltic Sea through all sections of the Øresund straits, the large and small Belts.

The currents of the Baltic Sea form a counter-clockwise circulation. Along the southern coast, the current is directed to the east, along the eastern coast - to the north, along the western coast - to the south, and near the northern coast - to the west. The speed of these currents ranges from 5 to 20 m/sec. Under the influence of winds, currents can change direction and their speed near the coast can reach 80 cm/sec or more, and in the open part - 30 cm/sec.

The surface water temperature in August in the Gulf of Finland is 15°C, 17°C; in the Gulf of Bothnia 9°C, 13°C and in the central part of the sea 14°C, 18°C, and in the south it reaches 20°C. In February - March, the temperature in the open part of the sea is 1°С-3°С, in the Gulf of Bothnia, Finland, Riga and other bays and bays below 0°С. The salinity of surface water decreases rapidly with distance from the straits from 11‰ to 6-8‰ (1‰-0.1%) in the central part of the sea. In the Gulf of Bothnia it is 4-5‰ (in the north of the bay 2‰), in the Gulf of Finland 3-6‰ (at the top of the bay 2‰ and less). In the deep and near-bottom water layers, the temperature is 5°C or more, and salinity varies from 16‰ in the west to 12–13‰ in the central part and 10‰ in the north of the sea. In years of increased water inflow, salinity rises to 20‰ in the west, to 14–15‰ in the central part of the sea, and in years of reduced inflow it drops to 11‰ in the middle parts of the sea.

Ice usually appears in early November to the north of the Gulf of Bothnia and reaches its greatest distribution in early March. At this time, a significant part of the Gulf of Riga, the Gulf of Finland and the Gulf of Bothnia is covered with immovable ice. central part seas are usually free of ice.

The amount of ice in the Baltic Sea varies from year to year. In exclusively harsh winters almost the entire sea is covered with ice, in soft ones - only bays. The northern part of the Gulf of Bothnia is covered with ice 210 days a year, the middle part - 185 days; Gulf of Riga - 80-90 days, Danish Straits - 16-45 days.

The level of the Baltic Sea is subject to fluctuations under the influence of changes in wind direction, atmospheric pressure (translational-standing long waves, seiches), inflow of river waters and waters of the North Sea. The period of these changes varies from several hours to several days. Rapidly changing cyclones cause level fluctuations of up to 0.5 m or more off the coast of the open sea and up to 1.5-3 m at the tops of bays and bays. Particularly large water rises, which, as a rule, are the result of the superposition of a wind surge on the crest of a long wave, occur in the Neva Bay. The greatest rise in water in Leningrad was noted in November 1824 (about 410 cm) and in September 1924 (369 cm).

Level fluctuations associated with tides are extremely small. The tides have irregular semidiurnal, irregular diurnal and diurnal character. Their size varies from 4 cm (Klaipeda) up to 10 cm (The Gulf of Finland).

The fauna of the Baltic Sea is poor in species, but rich in quantity. The brackish-water race of the Atlantic herring lives in the Baltic Sea (herring), Baltic sprat, as well as cod, flounder, salmon, eel, smelt, vendace, whitefish, perch. From mammals - the Baltic seal. There is an intensive fishery in the Baltic Sea.

Russian hydrographic and cartographic work began in the Gulf of Finland at the beginning of the 18th century. In 1738, F. I. Soimonov published an atlas of the Baltic Sea, compiled from Russian and foreign sources. In the middle of the 18th century many years of research in the Baltic Sea was carried out by A.I. Nagaev, who compiled a detailed sailing position. The first deep-sea hydrological research in the mid-1880s. were performed by S. O. Makarov. Since 1920, hydrological work was carried out by the Hydrographic Department, the State Hydrological Institute, and after Patriotic War From 1941 to 1945, extensive comprehensive research was launched under the direction of the Leningrad branch of the State Oceanographic Institute of the USSR.