Sea currents of the Baltic Sea briefly. Everything about the Baltic Sea: map, description, photo and video. Relief and depths

1) Baltic Sea.
2) The Baltic Sea belongs to the basin Atlantic Ocean.
3). Its area is 415 thousand sq. km. For comparison, the Black Sea is 422 thousand sq. km., Azov, only 39 thousand sq. km. .sq.km. Beloe - 90 thousand sq. km. Karskoe - 883 thousand sq. km., Laptev Sea - 650 thousand sq. km., East Siberian - 901 thousand sq. km., Chukchi - 582 thousand sq. km. .km., Beringovo-2314 thousand sq. km., Okhotsk-1590 thousand sq. km. and Japanese - 978 thousand square kilometers. These are the seas washing Russia.
4)Temperature water in the Gulf of Finland in summer 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. In winter average temperature water + 6 * C.
5)If you look at the outlines of the sea, you can see its dissection. Its separate parts - Katgegat and the straits of the Small and Big Belt, form a natural transition between the Baltic and the North Sea, and in the north and east the bays adjoin the sea: Bothnian, Finnish and Riga.
6) The islands of the Baltic Sea - Muhu, Pel, Aland, Ven, Zeeland, Merket, Gotland, about, Haiumaa and others.
7) The Baltic Sea is an inland sea. Its volume is 21.5 thousand km³ , average depth - 51 m, greatest depth- 470 m. The deeper, the lower the temperature.
8) The salinity of the Baltic Sea is low, it has different layers in terms of salinity.
The salinity of surface waters is 7-8 ppm, at the bottom it is much saltier.
9) About a hundred rivers, large and small, flow into the Baltic Sea, of which
Neman, Vistula, Pregolya, Pene, Oder, Leba, Lielupe, Daugava, Pärnu, Narva, Ne-va, Turne-Elv and others.
10) Biological resources. - herring and cod, which make up about 90% of all production. In addition, flounder and salmon are caught. There are large stocks of crustaceans, as well as molluscs.
11) A large amount of chemical toxic waste has been dumped into the Baltic Sea. There are many ships sunk during the war, downed aircraft with undecontaminated ammunition., On the one hand, the waste waters of enterprises and factories are drained. And on the other hand, a huge amount of cargo is transported by sea and through it around the world.
12) The Baltic Sea is covered with ice in some places. . The largest ice cover is reached at the beginning of March, the fixed ice occupies northern part Gulf of Bothnia, eastern part of Finland. And floating ice is in the center. IN harsh winters ice thickness reaches 1 m, and floating ice - 40-60 cm. Melting begins at the end of March, the sea is annually cleared of ice.
13) In question 10, the answer can be added that a lot of fish are still caught, such as salmon, herring, sprats.
14) Ecological problems covered in question 11. It can be added that due to runoff into the sea, a huge amount of algae began to grow in it, violating the ecosystem of the sea. Measures are needed to neutralize chemical waste from the sea.

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).

Deeply cut into the land, the Baltic Sea has a very complex outline of the coast and forms large bays: Bothnian, Finnish and Riga. This sea has almost everywhere land borders, and only from the Danish Straits (Great and Small Belt, Sound, Farman Belt) it is separated by conditional lines passing between certain points on their coasts. Due to the peculiar regime, the Danish Straits do not belong to the Baltic Sea. They link it to the North Sea and through it to the Atlantic Ocean. The depths above the rapids separating the Baltic Sea from the straits are small: above the Darser threshold - 18 m, above the Drogden threshold - 7 m. The cross-sectional area in these places is 0.225 and 0.08 km 2, respectively. The Baltic Sea is weakly connected with the North Sea and has limited water exchange with it, and even more so with the Atlantic Ocean.

It belongs to the type of inland seas. Its area is 419 thousand km 2, volume - 21.5 thousand km 3, average depth - 51 m, maximum depth - 470 m.

Bottom relief

The bottom relief of the Baltic Sea is uneven. The sea lies entirely within the shelf. The bottom of its basin is indented by underwater depressions, separated by hills and socles of islands. In the western part of the sea there are shallow Arkon (53 m) and Bornholm (105 m) depressions, separated by about. Bornholm. In the central regions of the sea, rather vast areas are occupied by the Gotland (up to 250 m) and Gdansk (up to 116 m) basins. North of about. Gotland lies the Landsort Depression, where the greatest depth of the Baltic Sea is recorded. This depression forms a narrow trench with depths of more than 400 m, which stretches from the northeast to the southwest, and then to the south. Between this trough and the Norrköping depression located to the south, an underwater hill stretches with depths of about 112 m. Further south, the depths again increase slightly. On the border of the central regions with the Gulf of Finland, the depth is about 100 m, with the Bothnian - about 50 m, and with the Riga - 25-30 m. The bottom relief of these bays is very complex.

Bottom relief and currents of the Baltic Sea

Climate

The climate of the Baltic Sea is of maritime temperate latitudes with features of continentality. The peculiar configuration of the sea and a significant extent from north to south and from west to east create differences climatic conditions V different areas seas.

The Icelandic low, as well as the Siberian and Azores anticyclones, most significantly affect the weather. The nature of their interaction determines the seasonal features of the weather. In autumn and especially winter time Icelandic Low and Siberian High interact intensively, which enhances cyclonic activity over the sea. In this regard, in autumn and winter, deep cyclones often pass, which bring with them cloudy weather with strong southwestern and western winds.

In the coldest months - January and February - the average air temperature in the central part of the sea is -3° in the north and -5-8° in the east. With rare and short-term intrusions of cold Arctic air associated with the strengthening of the Polar High, the air temperature over the sea drops to -30° and even to -35°.

In the spring-summer season, the Siberian High collapses, and the Baltic Sea is affected by the Icelandic Low, the Azores and, to some extent, the Polar High. The sea itself is located in a zone of low pressure, along which cyclones from the Atlantic Ocean are less deep than in winter. In this regard, in spring the winds are very unstable in direction and low in speed. Northerly winds are responsible for the usually cold spring in the Baltic Sea.

In summer, predominantly western, northwestern and southwestern weak to moderate winds blow. They are associated with the cool and humid summer weather characteristic of the sea. The average monthly temperature of the warmest month - July - is 14-15° in the Gulf of Bothnia and 16-18° in other areas of the sea. Hot weather is rare. It is caused by short-term inflows of warm Mediterranean air.

Hydrology

About 250 rivers flow into the Baltic Sea. The largest number waters are brought per year by the Neva - an average of 83.5 km 3, the Vistula - 30 km 3, the Neman - 21 km 3, the Daugava - about 20 km 3. The runoff is unevenly distributed across the regions. So, in the Gulf of Bothnia it is 181 km 3 /year, in Finland - 110, in Riga - 37, in the central part of the Baltic - 112 km 3 /year.

Geographical position, shallow water, complex bottom topography, limited water exchange with the North Sea, significant river runoff, and climate features have a decisive influence on hydrological conditions.

The Baltic Sea is characterized by some features of the eastern subtype of the subarctic structure. However, in the shallow Baltic Sea, it is represented mainly by surface and partially intermediate waters, significantly transformed under the influence of local conditions (limited water exchange, river runoff, etc.). The water masses that make up the structure of the waters of the Baltic Sea are not identical in their characteristics in different areas and change with the seasons. This is one of the distinguishing features of the Baltic Sea.

Water temperature and salinity

In most areas of the Baltic Sea, surface and deep water masses are distinguished, between which lies a transitional layer.

Surface water (0-20 m, in some places 0-90 m) with a temperature of 0 to 20°C, a salinity of approximately 7-8‰ is formed in the sea itself as a result of its interaction with the atmosphere (precipitation, evaporation) and with the waters of the continental runoff. This water has winter and summer modifications. In the warm season, a cold intermediate layer is developed in it, the formation of which is associated with a significant summer heating of the sea surface.

The temperature of deep water (50-60 m - bottom, 100 m - bottom) - from 1 to 15 °, salinity - 10-18.5‰. Its formation is associated with the entry of deep waters into the sea through the Danish straits and with mixing processes.

The transitional layer (20-60 m, 90-100 m) has a temperature of 2-6°C, salinity of 8-10‰, and is formed mainly by mixing surface and deep waters.

In some areas of the sea, the structure of the waters has its own characteristics. For example, in the Arkon region, there is no cold intermediate layer in summer, which is explained by the relatively shallow depth of this part of the sea and the influence of horizontal advection. The Bornholm region is characterized by a warm layer (7-11°) observed in winter and summer. It is formed by warm waters coming here from the slightly warmer Arkona basin.

In winter, the water temperature is somewhat lower near the coast than in the open parts of the sea, while it is slightly higher near the western coast than near the eastern one. So, average monthly temperature water in February near Ventspils is 0.7 °, at the same latitude in the open sea - about 2 °, and near the western coast - 1 °.

Water temperature and salinity at the surface of the Baltic Sea in summer

In summer, the temperature of surface waters is not the same in different parts of the sea.

The decrease in temperature near the western shores, in the central and southern regions is explained by the predominance of westerly winds, which drive the surface layers of water away from the western shores. Colder underlying waters rise to the surface. In addition, a cold current from the Gulf of Bothnia passes along the Swedish coast to the south.

well-defined seasonal changes water temperatures cover only the upper 50-60 m, deeper the temperature changes very little. In the cold season, it remains approximately the same from the surface to the horizons of 50-60 m, and deeper it drops somewhat to the bottom.

Water temperature (°С) on a longitudinal section in the Baltic Sea

In the warm season, the increase in water temperature as a result of mixing extends to horizons of 20–30 m. From there, it abruptly decreases to horizons of 50–60 m and then again rises somewhat towards the bottom. The cold intermediate layer persists in summer, when the surface layer warms up and the thermocline is more pronounced than in spring.

Limited water exchange with the North Sea and significant river runoff result in low salinity. On the sea surface, it decreases from west to east, which is associated with the predominant flow of river waters into the eastern part of the Baltic. In the northern and central regions of the basin, salinity decreases somewhat from east to west, since in cyclonic circulation, saline waters are transported from south to northeast along east coast sea ​​further than along the western. A decrease in surface salinity can also be traced from south to north, as well as in bays.

In the autumn-winter season, the salinity of the upper layers slightly increases due to a decrease in river runoff and salinization during ice formation. In spring and summer, salinity on the surface decreases by 0.2-0.5‰ compared to the cold half-year. This is explained by the desalination effect of continental runoff and the spring melting of ice. Almost throughout the sea, a significant increase in salinity from the surface to the bottom is noticeable.

For example, in the Bornholm Basin, salinity at the surface is 7‰ and about 20‰ at the bottom. The change in salinity with depth is basically the same throughout the sea, with the exception of the Gulf of Bothnia. In the southwestern and partly central regions of the sea, it gradually and slightly increases from the surface to horizons of 30-50 m, below, between 60-80 m, there is a sharp layer of a jump (halocline), deeper than which the salinity again slightly increases towards the bottom. In the central and northeastern parts, salinity increases very slowly from the surface to 70–80 m horizons; deeper, at 80–100 m horizons, there is a halo wedge, and then salinity slightly increases to the bottom. In the Gulf of Bothnia, salinity increases from the surface to the bottom by only 1-2‰.

In autumn-winter time, the flow of North Sea waters into the Baltic Sea increases, and in summer-autumn it somewhat decreases, which leads to an increase or decrease in the salinity of deep waters, respectively.

In addition to seasonal fluctuations in salinity, the Baltic Sea, unlike many seas of the World Ocean, is characterized by its significant interannual changes.

Observations of salinity in the Baltic Sea from the beginning of this century until recent years show that it tends to increase, against which short-term fluctuations appear. Changes in salinity in the basins of the sea are determined by the inflow of water through the Danish Straits, which in turn depends on hydrometeorological processes. These include, in particular, the variability of large-scale atmospheric circulation. The long-term weakening of cyclonic activity and the long-term development of anticyclonic conditions over Europe lead to a decrease in precipitation and, as a consequence, to a decrease in river runoff. Changes in salinity in the Baltic Sea are also associated with fluctuations in the values ​​of continental runoff. With a large river runoff, the level of the Baltic Sea slightly rises and the sewage flow from it intensifies, which in the shallow zone of the Danish Straits (the smallest depth here is 18 m) limits the access of salt water from the Kattegat to the Baltic. With a decrease in river flow, saline waters more freely penetrate into the sea. In this regard, fluctuations in the inflow of saline waters into the Baltic are in good agreement with changes in the water content of the rivers of the Baltic basin. IN last years an increase in salinity is noted not only in the bottom layers of the basins, but also in the upper horizons. At present, the salinity of the upper layer (20-40 m) has increased by 0.5‰ compared to the average long-term value.

Salinity (‰) on a longitudinal section in the Baltic Sea

Salinity variability in the Baltic Sea is one of the most important factors regulating many physical, chemical and biological processes. Due to the low salinity of the surface waters of the sea, their density is also low and decreases from south to north, varying slightly from season to season. Density increases with depth. In the areas of distribution of saline Kattegat waters, especially in basins at the horizons of 50-70 m, a constant layer of a density jump (pycnocline) is created. Above it, in the surface horizons (20-30 m), a seasonal layer of large vertical density gradients is formed, due to a sharp change in water temperature at these horizons.

Water circulation and currents

In the Gulf of Bothnia and in the shallow area adjacent to it, a density jump is observed only in the upper (20-30 m) layer, where it is formed in spring due to freshening by river runoff, and in summer due to heating of the surface layer of the sea. A permanent lower layer of the density jump is not formed in these parts of the sea, since deep saline waters do not penetrate here and year-round stratification of waters does not exist here.

Water circulation in the Baltic Sea

The vertical distribution of oceanological characteristics in the Baltic Sea shows that in the southern and central regions the sea is divided by a density jump layer into upper (0-70 m) and lower (from 70 m to the bottom) layers. In late summer - early autumn, when the sea is dominated by light winds, wind mixing extends to horizons of 10-15 m in the northern part of the sea and to horizons of 5-10 m in the central and southern parts and serves as the main factor in the formation of the upper homogeneous layer. During autumn and winter, with an increase in wind speeds over the sea, mixing penetrates to horizons of 20–30 m in the central and southern regions, and up to 10–15 m in the east, since relatively weak winds blow here. As autumn cooling intensifies (October - November), the intensity of convective mixing increases. During these months, in the central and southern regions of the sea, in the Arkon, Gotland and Bornholm depressions, it covers a layer from the surface up to about 50-60 m. ) and is limited by the density jump layer. In the northern part of the sea, in the Gulf of Bothnia and in the west of the Gulf of Finland, where autumn cooling is more significant than in other areas, convection penetrates to horizons of 60-70 m.

The renewal of deep waters, the sea occurs mainly due to the inflow of the Kattegat waters. With their active inflow, the deep and bottom layers of the Baltic Sea are well ventilated, and with small amounts of salt water flowing into the sea, great depths stagnation occurs in the depressions up to the formation of hydrogen sulfide.

The strongest wind waves are observed in autumn and winter in open, deep areas of the sea with prolonged and strong southwestern winds. Stormy 7-8-point winds develop waves up to 5-6 m high and 50-70 m long. In the Gulf of Finland strong winds these directions form waves with a height of 3-4 m. In the Gulf of Bothnia, storm waves reach a height of 4-5 m. The largest waves occur in November. In winter, with stronger winds, the formation of high and long waves is prevented by ice.

As in other seas of the northern hemisphere, the surface circulation of the Baltic Sea has a general cyclonic character. Surface currents are formed in the northern part of the sea as a result of the confluence of waters leaving the Bothnian and Gulf of Finland. The general flow is directed along the Scandinavian coast to the southwest. Going around on both sides about. Bornholm, he is heading through the Danish Straits to the North Sea. At south coast the current is directed to the east. Near the Gulf of Gdansk, it turns north and moves along the eastern coast to about. Khnum. Here it branches into three streams. One of them goes through the Irben Strait to the Gulf of Riga, where, together with the waters of the Daugava, it creates a circular current directed counterclockwise. Another stream enters the Gulf of Finland and along its southern coast extends almost to the mouth of the Neva, then turns to the northwest and, moving along the northern coast, leaves the bay together with river waters. The third flow goes to the north and through the straits of the Aland skerries penetrates into the Gulf of Bothnia. Here the current along the Finnish coast rises to the north, bends around north coast bay and along the coast of Sweden descends to the south. In the central part of the bay, there is a closed circular counterclockwise current.

The speed of the permanent currents of the Baltic Sea is very low and is approximately 3-4 cm/s. Sometimes it increases to 10-15 cm/s. The current pattern is very unstable and is often disturbed by the wind.

The prevailing wind currents in the sea are especially intense in autumn and winter, and during strong storms their speed can reach 100-150 cm/s.

Deep circulation in the Baltic Sea is determined by the flow of water through the Danish straits. The inlet current in them usually passes to horizons of 10-15 m. Then this water, being denser, descends into the underlying layers and is slowly transported by the deep current, first to the east and then to the north. With strong westerly winds, water from the Kattegat flows into the Baltic Sea almost along the entire cross section of the straits. Eastern winds, on the contrary, intensify the outlet current, which extends to the horizons of 20 m, and the inlet current remains only near the bottom.

Due to the high degree of isolation from the World Ocean, the tides in the Baltic Sea are almost invisible. Fluctuations in the level of the tidal character in individual points do not exceed 10-20 cm. The average sea level experiences secular, long-term, inter-annual and intra-annual fluctuations. They can be associated with a change in the volume of water in the sea as a whole and then have the same value for any point in the sea. The secular level fluctuations (except for changes in the volume of water in the sea) reflect the vertical movements of the shores. These movements are most noticeable in the north of the Gulf of Bothnia, where the rate of land rise reaches 0.90-0.95 cm/year, while in the south the rise is replaced by the sinking of the coast at a rate of 0.05-0.15 cm/year.

In the seasonal course of the Baltic Sea level, two minima and two maxima are clearly expressed. The lowest level is observed in spring. With the arrival of spring flood waters, it gradually rises, reaching a maximum in August or September. After that, the level goes down. The secondary autumn low is coming. With the development of intense cyclonic activity, westerly winds drive water through the straits into the sea, the level rises again and reaches a secondary, but less pronounced maximum in winter. The height difference between the summer maximum and the spring minimum is 22-28 cm. It is greater in the bays and less in the open sea.

Surge fluctuations in the level occur quite quickly and reach significant values. In open areas of the sea, they are approximately 0.5 m, and at the tops of bays and bays they are 1-1.5 and even 2 m. -26 h. Level changes associated with seiches do not exceed 20-30 cm in the open part of the sea and reach 1.5 m in the Neva Bay. Complex seiche level fluctuations are one of the characteristic features regime of the Baltic Sea.

The catastrophic St. Petersburg floods are connected with sea level fluctuations. They occur when the level rise is due to the simultaneous action of several factors. Cyclones that cross the Baltic Sea from the southwest to the northeast cause winds that drive water from western regions sea ​​and overtake it in the north-eastern part of the Gulf of Finland, where the sea level rises. Passing cyclones also cause seiche fluctuations in the level, at which the level rises in the Aland region. From here, a free seiche wave, driven by western winds, enters the Gulf of Finland and, together with the surge of water, causes a significant increase (up to 1-2 m and even 3-4 m) in the level at its top. This prevents the flow of the Neva water into the Gulf of Finland. The water level in the Neva is rapidly rising, which leads to floods, including catastrophic ones.

ice coverage

The Baltic Sea is covered with ice in some areas. The earliest (around the beginning of November) ice forms in the northeastern part of the Gulf of Bothnia, in small bays and off the coast. Then the shallow areas of the Gulf of Finland begin to freeze. The maximum development of the ice cover reaches in early March. By this time, motionless ice occupies the northern part of the Gulf of Bothnia, the region of the Aland skerries and the eastern part of the Gulf of Finland. Floating ice occurs in the open areas of the northeastern part of the sea.

The distribution of fixed and floating ice in the Baltic Sea depends on the severity of the winter. Moreover, in mild winters, ice, having appeared, may completely disappear, and then appear again. In severe winters, the thickness of immobile ice reaches 1 m, and floating ice - 40-60 cm.

Melting begins in late March - early April. Liberation of the sea ice is coming from southwest to northeast.

Only in severe winters in the north of the Gulf of Bothnia, ice can be found in June. However, the sea is cleared of ice every year.

Economic importance

Freshwater fish species live in the significantly freshened waters of the bays of the Baltic Sea: crucian carp, bream, chub, pike, etc. There are also fish that spend only part of their lives in fresh waters, the rest of the time they live in the salty waters of the sea. These are now rare Baltic whitefish, typical inhabitants of the cold and clean lakes of Karelia and Siberia.

A particularly valuable fish is the Baltic salmon (salmon), which forms an isolated herd here. The main habitats of salmon are the rivers of the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga. She spends the first two or three years of her life mainly in the southern part of the Baltic Sea, and then goes to spawn in the rivers.

Purely marine fish species are common in the central regions of the Baltic, where salinity is relatively high, although some of them also enter fairly fresh bays. For example, herring lives in the Gulf of Finland and Riga. More saltwater fish - Baltic cod - do not enter the fresh and warm bays. Eel is a unique species.

In fishing, the main place is occupied by herring, sprat, cod, river flounder, smelt, perch and different kinds freshwater fish.

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. The coast of Bothnia and a significant part of the coast (except the southern 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

Temperature surface layers water in the Gulf of Finland in summer 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 is the northern marginal body of water in Eurasia. It cuts deep into the land, and due to this it belongs to the water flows of the internal type. The sea fills the waters of the Atlantic. It is located in Northern Europe. The Baltic countries have access to the Baltic Sea. And also such states as: Denmark, Sweden, Finland, Germany, Russia and Poland. The stream connects with the ocean through the system and the North Sea.

The area of ​​the reservoir is about 415 thousand square km. The volume of the water mirror is more than 20 thousand cubic meters. km. The deepest gutter is 470 meters.

Hydrology

The Baltic Sea, whose salinity greatly affects the flora and fauna, is filled with a huge amount of fresh water. Precipitation is their constant source. Salt streams penetrate into the reservoir due to bays and tributaries. The tides have insignificant levels and, as a rule, their magnitude is not more than 20 cm.

Constantly located within a radius of one mark. Air masses can exert a strong influence on it. Near the coast, the water level can rise up to 50 cm, in narrower places - up to 2 meters.

There are practically no storms on the water stream. Like other seas washing Russia, the Baltic reservoir is calm, and rarely when its waves are able to reach a height of 4 meters. Most of all it storms in autumn, in November. Maximum fluctuations - 7-8 points. In winter, they practically stop, this is facilitated by ice.
The constant flow of the Baltic Sea is small. Within 10-15 cm/s. The maximum current increases during storms up to 100-150 cm/s.
The tides of the Baltic Sea are almost imperceptible. This is facilitated by the isolation of the water flow to a greater extent. Their level varies within 20 meters. The maximum increase in water level is in August and September.

A significant part of the coast is covered with ice from October to April. South part and the center of the sea, but glaciers can drift along them during the thawing period (June-August).

The Baltic Sea is rich in Natural resources. Oil reserves are hidden here, new deposits are being developed. Large deposits of amber have also recently been found. The Nord Stream gas route runs along the bottom of the sea.

And the Baltic Sea is rich in fish and seafood. In recent years, the ecology of the stream has deteriorated significantly. The waters are clogged with toxins coming out of major rivers. The presence of dumps of chemical weapons is also recorded.

Due to the shallow depth of the sea, shipping is not very developed here. Only light craft are able to cross the watercourse without problems. The largest ports of the Baltic Sea: Vyborg, Kaliningrad, Gdansk, Copenhagen, Tallinn, St. Petersburg, Stockholm.

The waters of this reservoir are unsuitable for the development of resort tourism, but nevertheless there are sanatoriums and clinics on the coastal part. These are Russian resort cities Svetlogorsk, Zelenogorsk, Sestroretsk, Latvian Jurmala, Lithuanian Neringa, Polish Koszalin and Sopot, German Albek and Binz.

Brief description of water temperature and sea salinity

In the central part of the Baltic Sea, as a rule, the temperature rarely exceeds 15-18 ° C. At the bottom, it is about 4 degrees. The bay often has calm weather and +9..+12 o C.

The Baltic Sea, whose salinity decreases in the direction from west to east, at the beginning of the current has an official indicator of 20 ppm. At depth, this figure increases by 1.5 times.

Name

For the first time, the etymological name "Baltic" is found in a historical treatise of the 11th century. More early title seas - Varangian. It is it that is mentioned in the famous Tale of Bygone Years.

extreme points

Extreme points of the Baltic Sea:

• southern - Wismar (Germany), coordinates - 53° 45` N. sh.;
• north - Arctic Circle coordinates - 65° 40` s. sh.;
• eastern - St. Petersburg (Russia), coordinates - 30 ° 15` in. d.;
• western - Flensburg (Germany), coordinates - 9 ° 10` in. d.

Geographical characteristics: territory, tributaries and bays

The Baltic Sea (salinity and its characteristics are described below) is extended from the southwest to the northeast for 1360 km. The greatest width is located between the cities of Stockholm and St. Petersburg. It is 650 kilometers.

According to historical data, the Baltic Sea has existed for about 4 thousand years. In the same period of time, the Neva (74 km) begins its existence, which flows into this reservoir. In addition to it, more than 250 rivers merge with the stream. The largest of them are Vistula, Oder, Narva, Neman, Zapadnaya Dvina.

Some ports of the Baltic Sea lie on its large bays. In the north is the Gulf of Bothnia, the largest and deepest. In the east - Riga, located between Estonia and Latvia, Finnish, washing the shores of Finland, Estonia, Russia, and Due to the fact that the latter is separated from the sea by a sandy spit, the water in the stream is almost fresh. This is a unique feature.

The average depth of the Baltic Sea is 50 meters, the bottom is completely within the mainland. This nuance makes it possible to attribute it to inland continental water bodies.

Islands

More than 200 islands of different sizes are located in the sea. They are located unevenly both near the coast and far from them. The largest islands in the Baltic are Zealand, Falster, Mön, Langeland, Lolland, Bornholm, Funen (belong to Denmark); Öland and Gotland (Swedish islands); Fehmarn and Rügen (refers to Germany); Hiiumaa, Saaremaa (Estonia).

Coastline

The Baltic Sea (the ocean strongly affects it with its waters) has a different coastline along the entire perimeter of the waters. In the northern part, the bottom is uneven, rocky, and the coast is indented with small bays, ledges and small islands. The southern part, on the contrary, has a flat bottom, and a low coast, with sandy beach, which in some areas is represented by small dunes. A frequent occurrence on the young coast - sandbars deep into the sea.
The sedimentary bottom is represented by green, black silt (has glacial origin) and sand, and the ground consists of stones and boulders.

Salinity and its regular changes

Due to the large amount of precipitation and powerful water flow from the rivers, the Baltic Sea (the salinity of the reservoir is relatively low) is filled in excess fresh water. It is distributed unevenly. Where the Baltic reservoir enters deep into the shore, the water is practically fresh, and the North Sea influences its salinity. This position is not permanent. Storm winds contribute to the mixing of water.
Based on this, the salinity of the Baltic Sea is low. A decrease in its level is typical for the coastline, the largest number of ppm is at the bottom.
In the territory where the watercourse meets the straits in the west, the salinity of the waters is up to 20 ‰ on the sea surface, at the bottom - 30 ‰. Off the coast of the Gulf of Bothnia and the Gulf of Finland, the lowest indicator. It does not exceed 3‰. The level from 6 to 8‰ is characteristic of the waters of the central part.

Seasonality also affects the distribution of salinity in the Baltic Sea. So, in the spring-summer season, it decreases by 0.5-0.2 ppm. This is due to the fact that melted rivers carry fresh water in the sea. And in autumn and winter, on the contrary, it increases due to the influx of cold northern masses.

The change in the salinity of the sea is one of the important reasons that regulate the biological, physical and chemical processes on the coast. Partly due to the freshness of the water, the coast has a loose structure.