Baltic Sea. Everything about the Baltic Sea: map, description, photo and video
It is heavily embedded in the land of the mainland. It is 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 bounded by land. Only from the south-west this sea is connected to the waters by various straits. The Baltic Sea belongs to the type of inland seas.
The shores that are washed by this sea have different origins. Difficult enough and. The Baltic Sea has a rather shallow depth, due to the fact that it is located within the boundaries of the continental shelf.
The greatest depth of the Baltic Sea is 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 waters between the Baltic Sea and. The Baltic Sea covers an area of \u200b\u200b419 thousand km2. The volume of water is 321.5 km 3. 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 continent. All these factors contribute to the fact that the climate of the Baltic Sea is in many respects similar to the maritime climate of temperate latitudes, and there are also some features of the continental climate. Due to the rather large extent of the sea, there are some distinctive features of the climate in different parts of the sea.
In the Baltic, it is largely due to the impact of the Icelandic minimum, Siberian and. Seasonal characteristics differ depending on whose influence is dominant. In autumn and winter, the Baltic Sea is influenced by the Icelandic minimum and the Siberian maximum. As a result, 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 strong southwestern and westerly winds.
In January and February, when the lowest is observed, the average monthly temperature of the central part of the sea is - 3 ° С, and in the north and east - 5 - 8 ° С. With the strengthening of the Polar Maximum, the cold ones fall on the Baltic Sea. As a result, it drops to - 30 - 35 ° С. But such cold snaps occur quite rarely and, as a rule, they are short-lived.
In the spring-summer period, the Siberian maximum loses its strength, and the Azores and, to a lesser extent, the Polar maximum have a dominant effect on the Baltic Sea. At this time the sea is observed. Cyclones arriving in the Baltic from the Atlantic Ocean are not as significant as in winter. All this determines the unstable direction of the winds, which have low speeds. In the spring season, the winds from the northern directions have a great influence on the weather, they bring cold air.
In summer, the winds of the western and north-western directions prevail. These winds are predominantly weak or. Thanks to their influence, the weather is cool and humid 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 Sea, which causes hot weather.
The temperature of the Baltic Sea waters 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, which is associated with the cooling effect of the land. In summer, the coldest waters are near the western shores in the central and southern zones of the sea. This temperature distribution 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.
Baltic Sea coast
Approximately 250 large and small rivers carry their waters to 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 abundant are: the Neva, which flows in 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 regions of the Baltic Sea, the share is not the same. For example, in the Gulf of Bothnia, rivers give 188 km 3 per year, while 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 it is 111.6 km 3 / year. Thus, the eastern regions of the sea receive more than half of all continental waters.
Rivers bring unequal amounts of water to the sea throughout the year. If the river flow is regulated by a lake, as, for example, near the Neva River, then the greater flow occurs in the spring-summer period. If the river flow is not regulated by lakes, as, for example, near the Daugava River, then the maximum flow is observed in spring and a slight increase in autumn.
B practically not observed. The current affecting surface waters is generated by winds and river runoff. In winter, the waters of the Baltic Sea are covered with ice. But during the same winter, ice can melt several times and again fetter the waters. This sea is never completely covered with ice.
Fishing is widely developed in the Baltic Sea. Here they catch Baltic herring, sprat, cod, whitefish, lamprey, salmon and other types of fish. Also in these waters, a large amount of algae is mined. There are many marine farms in the Baltic Sea where the most sought-after fish species are raised. There are a large number of placers on the coast of the Baltic Sea. Amber mining is being carried out in the region. There is oil in the depths of the Baltic Sea.
Shipping is widely developed in the waters of the Baltic Sea. There are constantly carried out sea transportation of various goods. Thanks to the Baltic Sea, it maintains close economic and trade relations with Western European countries. A large number of ports are located on the coast of the Baltic Sea.
Window to Europe
The Baltic Sea is an inland sea of \u200b\u200bthe Atlantic Ocean basin and is located in a shallow basin between the Scandinavian Peninsula and the European continent. The system of the Danish Straits, through the North Sea, connects the Baltic Sea with the ocean.
The surface area is 386 thousand square kilometers, the average depth is 71 m, the maximum is 459 m (the Landsortsjupet basin south of Stockholm).
The ancient Slavs called this sea Varangian.
As a result of studying the bottom topography and the nature of the soils, scientists came to the conclusion that in the preglacial period there was land on the site of the Baltic Sea. Then, during the Ice Age, the basin, which now houses the sea, was filled with ice, the process of melting which led to the formation of a lake with fresh water.
About 14 thousand years ago, this lake merged with the ocean as a result of the subsidence of land areas - the lake turned into a sea. Then, after another land uplift in the region of Central Sweden, the connection between the sea and the ocean was broken, and it again turned into a closed lake-type reservoir.
About 7 thousand years ago, another sinking of the land took place in the area of \u200b\u200bthe modern Danish straits and the connection of the lake with the Atlantic was resumed.
Subsequent fluctuations in land level led to the formation of the modern Baltic Sea.
The rise of land in the area continues to this day. Thus, in the area of \u200b\u200bthe Gulf of Bothnia, the bottom rise is approximately 1 m in 100 years.
Climate in the maritime region is temperate, characterized by small seasonal temperature fluctuations, frequent precipitation in the form of rains, fogs and snow.
Temperature surface water reaches +20 degrees C in summer. As you move to the north, the water is cooler and in the Gulf of Bothnia does not warm up above +9 - +10 degrees C. In winter, the water cools down to freezing point and the northern bays of the sea are covered with ice. The central and southern regions are usually ice-free, but in extremely cold winters, the sea can be completely covered with ice.
Water strongly freshened in the sea, especially in areas remote from the Danish straits. The reason is the numerous rivers and streams (almost 250) flowing into the sea.
Among the major rivers one can note the Neva, Narva, Vistula, Kemijoki, Western Dvina, Neman, Oder.
Currents in the sea they form a cyclonic gyre, often their direction and speed are corrected by the winds.
Tides the sea is very low - 5-10 cm, however, wind surges, especially in narrow bays, can exceed 3-4 meters.
Coastline The Baltic Sea is heavily indented. There are many large and small bays, bays, capes, spits. The northern shores are rocky; as you move to the south, rocks and stones are replaced by sand-pebble mixtures and sand. Here the shores are low and flat.
Islands of continental origin, especially many small rocky islets in the northern part of the sea. Large islands: Gotland, Bornholm, Sarema.
Bottom relief sea \u200b\u200bcomplex. There are many uplifts and depressions that have appeared as a result of the activity of glaciers, river beds, and land fluctuations. However, the elevation differences are small - the sea is shallow.
Animal world The Baltic Sea is relatively poor in represented species. A feature of the sea fauna is the distribution of freshwater and marine animal species in different regions. In the northern, more fresher areas, especially near river mouths, there are mainly freshwater animals and species that easily tolerate water desalination. Closer to the Danish straits, the sea water is much saltier, so many typical marine life can be found here. The general species composition of the sea is scarce, but rather rich in quantitative terms.
The poverty of the sea fauna is also explained by its youth, because in the form that it has now, its age is estimated only five thousand years. Scientists predict that another 5,000 years will pass, and the Baltic Sea will again lose contact with the ocean and turn into a large freshwater lake. Many forms of marine life in such a short time simply did not have time to adapt to local conditions of existence.
Nevertheless, the quantitative composition of the animals living in the Baltic Sea is quite large.
Bottom species of animals are represented mainly by worms, gastropods and bivalve molluscs, small crustaceans and bottom fish - flounder, gobies. In some places you can find a shaggy-hand crab - an alien from the North Sea and has taken root here. Near the Danish straits, there is even a giant among jellyfish - cyanea. And another type of jellyfish - eared aurelia in the Baltic Sea is found almost everywhere. Small schooling fish - three-spined stickleback, Baltic sprat.
In the desalinated areas of the sea, there are many river fish: roach, perch, pike, bream, ide, pike perch, migratory whitefish, burbot, etc.
In the baltic sea hunt such valuable fish as herring (about half of the total fish catch), sprat (sprat), salmon, eel, cod, flounder.
Marine mammals in the Baltic Sea there are only three species of seals: the gray seal (tyvyak), the common seal (seal), and the common porpoise, which belongs to the toothed cetaceans.
Shark in the Baltic Sea, they are represented only by the ubiquitous katrana - a small prickly shark, which is dangerous to humans only by its spines on its dorsal fins. But these fish are not settled in all areas of the sea - too freshened and shallow areas are not suitable for them to live.
However, in the area of \u200b\u200bthe Danish Straits, connecting the Baltic with the North Sea, sometimes other predators are also found - herring sharks. No such guests have been registered on the Russian shores of the Baltic Sea.
In conclusion, I would like to note that at present the Baltic Sea is intensively polluted by various chemical and biochemical effluents, as well as trace elements contained in precipitation. This leads to the mass death of microflora and microfauna, which in large quantities settle to the bottom and are processed by bacteria into hydrogen sulfide. And hydrogen sulfide has a detrimental effect on all living organisms in the bottom layer of water. If urgent action is not taken, the number of aquatic animals in the sea will decrease significantly.
The salinity of which is about 20% of the salinity of the World Ocean, is located in the northern part of Europe. Refers to the type of inland seas. Its area is 419 square kilometers. It was the Baltic Sea that became a window to Europe during the reign of Peter the Great.
general characteristics
The average depth of the Baltic Sea is about 50 meters, the highest recorded depth is 470 meters. The deepest areas are in the Scandinavian region, the shallowest areas are in the Curonian Spit area, there is no depth even 5 meters.
More than two hundred rivers flow into the Baltic Sea. The largest of them are Neman, Daugava, Vistula, Neva. Fresh river water is unevenly distributed in it, so the salinity of the Baltic Sea is not the same.
Ice cover in winter is established in the bays from November to April. The ice thickness reaches 60 cm. The southern regions of the sea can remain without ice cover throughout the winter. Sometimes there are floating ice floes near the northern shores even in summer. The last case of complete freezing of the Baltic Sea was noted in 1987.
In the autumn-winter period, the inflow of North Sea salt water increases due to the decrease in water temperature. This increases the salinity in the sea.
Geographic features
The Baltic Sea is located in the northwest of Europe. In the north, it reaches almost the Arctic Circle, the coordinates of the northernmost point of the sea are 65 degrees 40 minutes s. sh. In the south, it reaches 53 degrees 45 minutes s. sh. From east to west, the Baltic Sea stretches from St. Petersburg (30 degrees 15 minutes E) to the city of Flensburg in Germany (30 degrees 10 minutes E).
The Baltic Sea is surrounded by a coastline on almost all sides, only in the west it has access to the North Sea. Belomorkanal opens access to the White Sea. The largest part of the coast belongs to Sweden and Finland (35% and 17%), Russia has about 7%, the rest of the coastline is divided between Germany, Denmark, Poland, Estonia, Lithuania and Latvia.
There are four large bays in the sea - the Bothnian, Curonian, Finnish and Riga. The Curonian Lagoon is separated by the Curonian Spit, geographically belongs to Lithuania and Russia (Kaliningrad region). The Gulf of Bothnia is located between Sweden and Finland and is home to the Åland Islands archipelago. The Gulf of Finland is in the east, adjacent to the coast of Finland, Estonia and Russia (St. Petersburg).
Baltic Sea: salinity and temperature regime
The water surface temperature in the central part is 15-17 degrees. In the Gulf of Bothnia, this figure does not rise more than 12 degrees. The highest temperature is observed in the Gulf of Finland.
Due to the weak water exchange and the constant flow of river water, this sea has low salinity. In addition, it does not have constant indicators. So, in the area of \u200b\u200bthe Danish coast, the salinity of the Baltic Sea water is 20 ppm at the surface. At a depth, the indicator can reach up to 30 ppm. The salinity of the surface waters of the Baltic Sea changes its quantity towards the east towards a lesser extent. In the Gulf of Finland, this figure is no more than 3 ppm.
Observations in recent years have recorded an upward trend in the percentage of salinity. This figure has increased by 0.5% over previous decades. Now the average salinity of the Baltic Sea is 8 ppm. The figure indicates that a liter of sea water contains 8 g of salt. This is the salinity of the Baltic Sea in grams.
Baltic Sea climate
The Baltic Sea is characterized by a temperate maritime climate. The average January temperature above the sea surface is 1-3 degrees, in the north and east - 4-8 degrees. Sometimes the invasion of cold streams from the Arctic lowers the temperature to -35 degrees for a short time. In winter, the north wind prevails, which leads to cold winters and long, protracted springs.
In summer, the wind direction changes to west and south-west. On the coast, rainy and cool summer weather sets in. Dry hot days in the Baltic are very rare. The average July temperature here is 14-19 degrees.
The average salinity of the Baltic Sea surface waters depends on the seasonality. The period of strong winds occurs at the end of autumn and winter. During a storm in November, the waves rise up to 6 meters. In winter, ice prevents the formation of high waves. At this time, the salinity decreases.
Animal world
The Baltic Sea, the salinity of which has different indicators in different places, is inhabited by a fairly diverse species - from purely marine to freshwater inhabitants. So, in the salty waters of the Danish straits, various mollusks, oysters, crustaceans live. In some places, there is even a guest from the North Sea - a hairy-handed crab.
Most of the commercial fish species for habitation choose the central waters, where the average salinity of the surface waters of the Baltic Sea is 7-9 ppm.
Pike, bream, crucian carp, roach, ide, burbot, eel are found in bays with practically fresh water. Fishing for Baltic herring, cod, sprat, salmon and sea trout is carried out here on an industrial scale.
Spa vacation
Due to the cool climate, the resorts of the Amber Territory are not to everyone's taste. They have little in common with the hot beaches of Turkey, Egypt, Crimea. Officially, the beach season in the Baltic lasts from June to the end of September, while in June the water does not always warm up even to 20 degrees.
However, hot, crowded beaches are not to everyone's taste. Many people prefer to combine a beach holiday with an active one, for example, with the study of culture and attractions. The beaches of the Baltic Sea are a very good option. You can choose the resort Palanga, Jurmala, Gdansk, Sopot, Svetlogorsk and others. The ideal time to relax is July and the first half of August, when the water temperature warms up to 25 degrees. In the shallow waters of the Gulf of Riga, a temperature of 25-27 degrees was recorded.
Environmental problems of the Baltic Sea
In recent years, there has been a significant deterioration in water quality due to pollution. One of the reasons is that the rivers flowing into the sea carry already polluted waters. And since the sea is inland and has only one outlet through the Danish straits, there is no possibility of natural self-purification.
The following main water pollutants can be distinguished:
- industrial, agricultural and municipal waste that comes from urban wastewater, often directly to the sea;
- heavy metals - come from city drains, some fall out with precipitation;
- spilled oil products - in the era of the development of shipping, leakage of oil products is not uncommon.
The consequences of pollution are the formation of a film on the surface of the water and the cessation of oxygen access to its inhabitants.
The main sources of water pollution:
- active shipping;
- accidents at industrial plants and power plants;
- industrial and domestic wastewater;
- polluted rivers flowing into the sea.
Helsinki Convention
In 1992, nine Baltic states signed a convention on the observance of environmental and maritime rights. The main body is a commission headquartered in Helsinki. The main goal of the commission is to develop and carry out measures aimed at protecting the ecology of the marine environment, conducting research, and promoting the safe navigation of ships.
The commission is headed by the states with access to the sea for a period of two years. From 2008 to 2010 Russia was the chairmanship.
Drunken forest and amber
In the Kaliningrad region, on the Curonian Spit, there is an unusual place, popularly called the Dancing or Drunken Forest. Pines planted in the USSR grow on a small area (within 1 square km). The bottom line is that the trees are strangely curved, and some are generally twisted into a loop. Scientists cannot accurately explain this phenomenon. The versions are different: climatic factor, genetics, attack by pests and even the influence of space. Rumor has it that there are no sounds in the forest and mobile communication is lost. The mystery of the forest annually attracts domestic and foreign tourists.
In the autumn, when a storm begins, the sea throws amber onto the shore together with the sand. Mainly on the shores of Poland, Russia, Germany. This period is awaited by local craftsmen and visiting adventurers. There is a belief that amber is a stone for fulfilling desires. Amber souvenirs fill the atmosphere of the house with positive energy, promote harmony in personal relationships.
This is how the Baltic Sea is, the salinity, climate and richness of which attract with their uniqueness.
Baltic "Titanic"
In 1994, on the night of September 28, a disaster struck at sea, the secret of which remains a mystery today. In the evening of September 27, the ferry "Estonia" departed from Tallinn on its last voyage. There were about 1000 passengers and crew on board. The vessel made a regular voyage to Stockholm for a long time. The track is familiar, no unforeseen situations on the route were expected. The sea was stormy, but neither passengers nor crew members were bothered. An ordinary Baltic autumn, it was believed that a storm was not terrible for a vessel of this type.
Toward midnight, the storm intensified, but the passengers were calm and getting ready for bed. By that time, the ferry had departed 350 km from the port. At this time, the ferry met with the oncoming ship "Mariella". After 1 am, a distress signal was received from the ferry, after which the ship disappeared from the radar. The Mariella and the ships nearby hurried to the scene of the tragedy. By three o'clock in the morning, rescue helicopters arrived at the crash site. Many victims no longer needed help - death came from hypothermia. In total, about 200 passengers were rescued, another 95 were identified and officially declared dead.
The Baltic Sea is located between Central and Northern Europe and is part of the Atlantic Ocean basin. The reservoir washes the shores of such states as Russia, the Baltic countries (Estonia, Lithuania, Latvia), Poland, Germany, Denmark, Scandinavian countries (Finland, Sweden). The water surface area is 415 thousand square meters. km. The volume is 21.7 thousand cubic meters. km. The maximum length is 1600 km. The maximum width is 193 km. The average depth corresponds to 55 meters, and the maximum is 459 meters. The length of the coastline is 8 thousand km.
Geography
The reservoir is connected by artificial canals with the North and White Seas. In the first case, it is the Kiel Canal (length 98 km). It allows ships, without skirting Jutland, to immediately get into the North Sea. In the eastern part of the canal is the German city of Kiel, in the western city of Brunsbüttel. As for the White Sea, the way to it passes through the White Sea Canal.
The Baltic is naturally connected to the North Sea through the Kattegat (200 km long) and Skagerrak (240 km long) straits. It is a body of water between Jutland and Scandinavia.
Bays
There are the following large bays in the Baltic: Botanichesky, Finnish, Rizhsky, Curonian.
Botanical Bay is located in the northern part of the reservoir between Sweden and Finland. In the southern part it has the Aland Islands. Its area is 117 thousand square meters. km.
The Gulf of Finland is located in the eastern part of the Baltic. It washes the shores of Estonia, Russia and Finland. Its area is 29.5 thousand square meters. km. On its banks are located such large cities as St. Petersburg, Helsinki and Tallinn.
The Curonian Lagoon is a lagoon separated from the sea by the Curonian Spit. Its area is 1610 sq. km. The waters of the bay belong to Lithuania and the Kaliningrad region of Russia. The city of Klaipeda is located at the junction of this small reservoir with the sea.
Islands
The Aland Islands are an archipelago in the Botanical Bay. It has 6757 islands, but only 60 are people. The largest island is Åland with an area of \u200b\u200b685 sq. km. The total area of \u200b\u200bthe archipelago is 1552 sq. km.
The island of Gotland (Sweden) is located in the central part of the sea and 100 km from the Swedish coast. Its area is almost 3 thousand square meters. km. About 57 thousand people live on it.
Another Swedish island is called Öland. Its area is 1342 sq. km. This piece of land is home to 25 thousand people. They receive at least 500 thousand tourists every summer.
Bornholm Island, although located near the Swedish coast, belongs to Denmark. Its area is 588 sq. km. It is home to 42 thousand people. From the island to Copenhagen 169 km, and to Sweden 35 km.
Poland owns the island of Wolin with an area of \u200b\u200b265 sq. km. On it is the city of Volin with a population of about 5 thousand people.
The island of Rügen belongs to Germany. Its area is 926 sq. km. It is home to 77 thousand people. These are the lands of the Prussian province of Pomerania.
The Estonian island of Saaremaa, which is part of the Moonsund archipelago, also belongs to the large islands. It belongs entirely to Estonia. As for Saaremaa, its area is 2.7 thousand square meters. km with a population of 35 thousand people. The archipelago has 4 large and about 500 small islands. Their total area is about 4 thousand square meters. km.
Rivers flowing into the Baltic Sea
Such rivers as the Neva with a length of 74 km, Narva (77 km), Daugava or Western Dvina (1020 km), Neman (937 km), Vistula (1047 km), Pregolya (123 km), Venta (124 km ), Odra or Oder (903 km).
Baltic Sea on the map
Hydrology
The reservoir is notable for the fact that it constantly contains a large excess of fresh water. They come from rivers and as a result of precipitation. Surface salt water flows into the North Sea through the Kattegat and Skagerrak straits. But salt water enters the Baltic in the same way, but only through a deep current. The tides are slight. Their size does not exceed 20 cm.
Wind has a much greater effect on the water level near the coast. It can raise the level up to 50 cm, and in narrow bays and bays up to 2 meters. If we talk about standing waves (seiches), then here the amplitude of oscillations reaches 50 cm.
In terms of storms, the Baltic Sea is generally calm. The wave height does not exceed 4 meters. On rare occasions, winds can create waves with a height of 10 meters. Since the salinity of the water is low, the hulls of ships can be iced in winter.
Ice appears in the bays in the month of November. This applies to the northern and eastern regions. At the same time, the thickness of the ice crust can reach 60-65 cm. The southern and central parts of the reservoir are not covered with ice. Ice cover melts in the month of April. In the north, floating ice floes can be found in the month of June. Since 1720, the reservoir has frozen completely 20 times. The last such case was recorded in January 1987. During this period there was an extremely harsh winter in Scandinavia.
In the central regions of the sea, the color of the water is bluish-green. It also has maximum transparency. The closer to the coast, the transparency decreases, and the color changes to pale green with a yellowish or brown tint. Plankton is often the cause of poor transparency.
Water temperature and salinity
In the central parts of the sea, the temperature of the surface water layers is 14-17 degrees Celsius. In the Botanical Bay, the corresponding values \u200b\u200bare 9-12 degrees Celsius. But in the Gulf of Finland it is 1 degree warmer than in the central part. At depth, the temperature first decreases and then rises. At the bottom, it is 4-5 degrees Celsius.
Near sea water, salinity decreases from west to east. At the extreme western points, it is equal to 20 ppm at the sea surface. At a depth of 30 ppm. In the center of the reservoir, the salinity at the surface is 7-8 ppm. In the north it is 3 ppm, and in the east it is 2 ppm. With depth, these figures increase and reach 13-14 ppm.
1992 Helsinki Convention
In 1992, the states whose shores are washed by the Baltic Sea signed a convention on the strict observance of environmental and maritime law in the waters of the Baltic. The governing body of the convention is the Helsinki Commission (HELCOM) or the Marine Environment Protection Commission. The contracting parties are Russia, Sweden, Finland, Estonia, Latvia, Lithuania, Denmark, Germany, Poland. The ratified letters were deposited in Germany, Sweden and Latvia in 1994, Finland and Estonia in 1995, Denmark in 1996, Lithuania in 1997, Russia and Poland in 1999.
The convention testifies to the high responsibility that people feel in relation to the unique region formed by the Baltic waters. Its flora and fauna should not be at risk of ecological disaster.
The Baltic Sea washes the shores of the Russian Federation, Denmark, and the Baltic countries. The Russian Federation owns small water areas in the eastern part of the Baltic Sea - the Kaliningrad Bay and part of the Curonian Lagoon (the territory of the Kaliningrad Region) and the eastern edge of the Gulf of Finland (the territory of the Leningrad Region).
The Baltic Sea is deeply cut into the northwestern part of Eurasia. This is an inland sea, connected to the North Sea of \u200b\u200bthe Atlantic Ocean by the system of the Oresund (Sound), Great Belt, Small Belt, known collectively as the Danish Straits. They pass into the deep and wide straits of the Skagerrak, Kattegat, already belonging to the North Sea, which is directly connected with.
The area of \u200b\u200bthe Baltic Sea is 419 thousand km2, the volume is 21.5 thousand km3, the average depth is 51 m, the maximum depth is 470 m.
About 250 rivers flow into the Baltic Sea. The largest rivers are the Vistula, Oder, Neman, Daugava, Neva. The Neva brings the largest amount of water in a year - an average of 83.5 km3.
The Baltic Sea stretches from southwest to northeast, and its maximum length is 1360 km. The widest part of the sea at 60 ° N. sh., between St. Petersburg and Stockholm, it stretches for almost 650 km.
The bottom relief of the Baltic Sea is uneven. The entire sea lies within the shelf. The bottom of its hollow is cut by underwater depressions, separated by uplands and island socles.
The Baltic Sea is characterized by a long coastline. It has many bays, bays and a large number of islands. The sea is a set of separate basins: the zones of the Danish straits, the open or central part of the sea and three large bays - the Bothnian, Finnish and Riga, which account for almost half of the sea area.
Numerous islands of the Baltic Sea are located both on the mainland coast and in the open sea; in some parts of the sea the islands are grouped in large archipelagos, in others they stand alone.
The largest of the islands: Danish - Zealand, Funen, Lolland, Falster, Langeland, Meun, Bornholm; Swedish - Gotland, Oland; German - Rügen and Fehmarn; - Saaremaa and Hiiumaa.
The shores of the northern and southern half of the sea differ sharply in character. The skerry shores of Sweden and Finland are indented with small bays and bays, framed by islets made of crystalline rocks. They are mostly low, sometimes bare, and in some places overgrown with coniferous forest. The southern shores are low-lying, composed of sand and have a large number of shoals. In some places along the coast there are chains of sand dunes, and long spits protrude into the sea, forming large lagoons freshened by river runoff. The largest of these shallow bays are Curonian and Vistula.
Bottom sediments of the Baltic Sea are represented mainly by silts and sand. The soils of the Baltic Sea are characterized by stones and boulders, which are often found at the bottom of the sea. Sandy deposits are common in coastal areas. In the Gulf of Finland, most of the bottom is covered with sands with individual patches of silt, occupying small depressions and forming a field of sediments in the Neva River delta that is somewhat elongated along the strike of the bay. The construction of the dam, which fenced off a significant part of the water area from the open sea, significantly changed the composition and distribution of precipitation that existed in natural conditions.
The climate of the Baltic Sea is maritime temperate latitudes with features of continentality. The peculiar configuration of the sea and its considerable length from north to south and from west to east create differences in climatic conditions in different regions of the sea.
The Icelandic minimum, as well as the Siberian and Azores anticyclones, have the most significant influence on the weather. The nature of their interaction determines the seasonal features of the weather. In autumn and especially winter time, the Icelandic minimum and the Siberian maximum interact intensively, which enhances cyclonic activity over the sea. In this regard, in the autumn-winter time, deep cyclones often pass, which bring with them cloudy weather with strong southwestern and westerly winds.
In the coldest months - January and February - the average in the central part of the sea is –3 ° С in the north and –5 ... –8 ° С in the east. With rare and short-term intrusions of cold Arctic air associated with the strengthening of the Polar Maximum, the air temperature over the sea drops to –30 ° С and even to –35 ° С.
In summer, mainly westerly, northwesterly 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 is 14-15 ° С in the Gulf of Bothnia and 16-18 ° С in the rest of the sea. Hot weather is rare. It is caused by short-term influx of warm Mediterranean air.
The temperature conditions of the Baltic Sea waters in different parts of it are not the same and depend not only on the geographic location of the place, but also on the meteorological and hydrological features of the area. The most important for the temperature regime of the Baltic Sea are surface heating by sun rays, river runoff and the flow of deep oceanic waters. water. This determines the general picture of the temperature conditions of the sea. In the surface layers, the water temperature varies widely. At depths exceeding 50 meters, the water temperature all year round is kept within 3-4 ° C in the southern part of the sea and near zero in the northern Bothnian region.
In the summer months, the surface water temperature is generally close to the air temperature. Near the eastern shores, the water temperature is higher due to the influence of the warmed land masses lying to the south, and along the western, Swedish, coast is lower due to the flow of cold waters from the north, from the Gulf of Bothnia. In winter, on the contrary, the eastern parts of the sea are colder than the western ones; they are subject to the influence of the cooled land masses of the continent, and the western parts of the sea during this period experience a regular influx of warm air masses of the Atlantic.
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 influx of river waters from the eastern Baltic. In the northern and central regions of the basin, salinity slightly decreases from east to west, since in the cyclonic circulation, saline waters are transported from south to northeast along the eastern coast of the sea further than along the western one. A decrease in surface salinity is also traced from south to north in bays.
A significant increase in salinity from the surface to the bottom is noticeable in almost the entire sea. The change in salinity with depth occurs 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 insignificantly increases from the surface to 30–50 m horizons; below, between 60–80 m, there is a sharp jump layer (halocline), deeper than which salinity slightly increases to the bottom. In the central and northeastern parts, salinity very slowly increases from the surface to 70–80 m horizons, a halocline occurs at a depth of 80–100 m, and then salinity slightly increases to the bottom. In the Gulf of Bothnia, salinity increases from the surface to the bottom only at 1–2 ‰.
In the autumn-winter time, the inflow of North Sea waters into the Baltic Sea increases, and in the summer-autumn time it slightly decreases, which leads, respectively, to an increase or decrease in the salinity of deep waters. In the autumn-winter season, the salinity of the upper layers increases somewhat due to the reduction and deviation during ice formation. In spring and summer, salinity on the surface decreases by 0.2–0.5 ‰ in comparison with the cold half-year. This is due to the freshening influence of continental runoff and spring ice melting. In addition to seasonal fluctuations in salinity, the Baltic Sea, in contrast to many seas of the World Ocean, is characterized by its significant interannual changes. The variability of the salinity of the Baltic Sea is one of the most important factors regulating many physical, chemical and biological processes. Due to the low salinity of the sea surface waters, their density is also low and decreases from south to north, slightly varying from season to season. The density increases with depth.
The strongest wind waves are observed in autumn and winter in open, deep sea areas with long and strong southwestern winds. Storm 7–8-point winds develop waves up to 5–6 m high and 3–4 m long. The largest waves occur in November. In winter, with stronger winds, ice prevents the formation of high and long waves. As in other seas of the Northern Hemisphere, the surface circulation of the Baltic Sea waters has a general cyclonic character.
Surface currents are formed in the northern part of the sea as a result of the confluence of waters coming out of the Gulfs of Bothnia and Finland. The speed of the constant currents of the Baltic Sea is very low and is equal to about 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. Wind currents prevailing 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 goes up to a horizon of 10–15 m. Then this water, being denser, sinks into the underlying layers and is slowly transported by a deep current, first to the east and then to the north.
Due to the high degree of isolation from the World Ocean, tides in the Baltic Sea are almost invisible. Fluctuations in the tidal level at some points do not exceed 10–20 cm. In the seasonal variation 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 increases, reaching a maximum in August or September. After that, the level goes down. Secondary autumn low sets in. With the development of intense cyclonic activity, westerly winds overtake water through the straits into the sea, the level rises again and reaches a secondary, but less pronounced maximum in winter. The difference in level heights between the summer maximum and spring minimum is 22–28 cm. It is greater in bays and less in the open sea.
Surge sea level fluctuations occur rather quickly and reach significant values. In the open areas of the sea, they are approximately 0.5 m, and in the tops of bays and gulfs, they are 1–1.5 and even 2 m. The combined effect of the wind and a sharp change (during the passage of cyclones) cause seiche fluctuations of the level surface with a period of 24–26 h. Level changes associated with seiches do not exceed 20–30 cm in the open sea and reach 1.5 m in the Neva Bay. Complex seiche level fluctuations are one of the characteristic features of the Baltic Sea regime.
Sea level fluctuations are associated with catastrophic floods c.
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 coves and off the coast. Then shallow areas of the Gulf of Finland begin to freeze. The ice cover reaches its maximum development in early March. By this time, stationary 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. In the open areas of the northeastern part of the sea, floating ice is found.
The main problems of the Baltic Sea are associated with the gradual deterioration of oxygen conditions in the deep layers of the sea, which has been observed over the past decades. In some years, oxygen disappears completely already at a depth of 150 m, where it forms hydrogen sulfide. These changes are a consequence of both natural changes in the environment, mainly temperature, water salinity and water exchange, and anthropogenic impact, expressed mainly in an increase in the supply of nutrient salts in the form of various forms of nitrogen and phosphorus.
The importance of the Baltic Sea in the national economy of the countries of the region and the ever-increasing negative influence of anthropogenic factors on the quality of the marine environment require urgent measures to guarantee the purity of the sea.
Pollution enters the sea directly from sewage or from ships, diffusely through rivers or. The bulk of pollutants is brought into the sea with river runoff (Neva, Vistula) both in a dissolved state and in adsorbed on suspended matter. In addition, the coastal cities, St. Petersburg, Kronstadt, Vyborg and, to the greatest extent, the merchant and military fleets are sources of pollution of the marine environment with oil products.
The greatest harm to the marine environment is caused by toxic substances (salts of heavy metals, DDT, phenols, etc.), oil products, organic and biogenic substances. About 300 tons of oil products are annually delivered to the Gulf of Finland from various sources. The bulk of nitrogenous compounds enter the sea diffusely, as well as sulfur compounds, which enter the marine environment mainly through the atmosphere. Toxic substances are discharged mainly by industry. The different nature of pollution complicates the struggle for the purity of the marine environment and requires a complex set of water protection measures.
Monitoring of the marine environment is, first of all, the organization of systematic observations of the physicochemical and biological indicators of the marine environment at permanent representative points of the water body.
The quality of the Baltic Sea marine environment in general meets the requirements of water users, however, pollution zones have formed near many large cities. It is alarming that over the past decades, the content of toxic substances in marine living organisms has increased to two orders of magnitude, which once again indicates the need for urgent water protection measures. Accidental spills of oil products from tankers cause great harm. The monitoring results will make it possible to periodically check the state of the marine environment, that is, to reveal the dynamics of sea pollution.
The two small sections of the seabed of the coastal part of the Baltic Sea belonging to Russia are sharply different in terms of the geoecological situation. The most anthropogenic pressure is experienced by the inner, eastern part of the Gulf of Finland within the Leningrad Region. The main pollution zone was the part of the bay located east of Kotlin Island, between it and the Neva delta. This happened a few years ago after the construction of a dam that runs from Kotlin Island to the northern and southern mainland shores. An important element of the geoecological situation in the eastern part of the Gulf of Finland is the numerous underwater quarries for the extraction of construction raw materials, mainly sand, which in the future may pose a threat to the stability of the coastal part of the seabed and shores.
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