Baltic sea. Everything about the Baltic Sea: map, description, photo and video
Heavily cut into the mainland. Its not as severe as the climate of the Arctic seas, although the Baltic Sea is located in the northwestern part of Russia. This sea is almost completely limited by land. Only from the southwest is this sea connected to the waters by various straits. The Baltic Sea belongs to the type of inland seas.
The shores that this sea washes have a different origin. Quite complicated and. At Baltic Sea rather small depth, due to the fact that it is located within the boundaries of the continental shelf.
The greatest depth of the Baltic Sea was recorded in the Landsort Basin. The Danish Straits are characterized by shallow depths. The depth of the Great Belt is 10 - 25 m, the Small Belt - 10 - 35 m. The waters of the Sound have a depth of 7 to 15 m. The shallow depths of the straits interfere with the unhindered exchange of water between the Baltic Sea and. The Baltic Sea covers an area equal to 419 thousand km2. The volume of water is 321.5 km3. The average water depth is about 51 m. The maximum sea depth is 470 m.
The climate of the Baltic Sea is influenced by its location in the zone of temperate latitudes, the proximity of the Atlantic Ocean and the location of a large part of the sea inside the mainland. All these factors contribute to the fact that the climate of the Baltic Sea is in many respects close to the maritime climate of temperate latitudes, and there are also some features of the continental climate. Due to the relatively large extent of the sea, there are some distinctive features climate in various parts seas.
In the Baltic, it is largely due to the influence of the Icelandic low, the Siberian and. Depending on whose influence is dominant, seasonal features differ. In autumn and winter, the Baltic Sea is influenced by the Icelandic Low and the Siberian High. As a result of this, the sea is in power, which spread in autumn from west to east, and in winter to the northeast. This period is characterized by cloudy weather with large southwestern and western winds.
In January and February, when the lowest temperature is observed, the average monthly temperature in the central part of the sea is -3°C, and in the north and east - 5-8°C. With the strengthening of the Polar High, cold ones enter the Baltic Sea. As a result, it drops to – 30 – 35°C. But such cold snaps are quite rare and, as a rule, they are short-lived.
V spring-summer period The Siberian High is losing its strength, and the Azores and, to a lesser extent, the Polar High have a dominant effect on the Baltic Sea. At this time, the sea is observed. Cyclones coming to the Baltic from the Atlantic Ocean are not as significant as in winter. All this causes the unstable direction of the winds, which have low speeds. In the spring season, northerly winds have a great influence on the weather, they bring cold air.
In summer, winds from the western and northwestern directions prevail. These winds are predominantly weak or. Due to their influence, cool and humid weather is observed in summer. average temperature July reaches + 14 - 15°С in the Gulf of Bothnia and +16 - 18°С in other areas of the sea. Very rarely, warm air masses enter the Baltic, which cause hot weather.
The temperature of the waters of the Baltic Sea depends on the specific location. V winter time the temperature of the waters near the coast is lower than in the open sea. In the western part, the sea is warmer than in the eastern part, which is associated with the cooling effect of the land. In summer, the coldest waters are near the western coasts in the central and southern zones of the sea. Such a distribution of temperatures is due to the fact that the western ones move the heated upper waters from the western shores. Their place is taken by cold deep waters.
Coast of the Baltic Sea
Approximately 250 large and small rivers carry their waters into the Baltic Sea. During the year they give the sea about 433 km 3, which is 2.1% of the total volume of the sea. The most full-flowing are: the Neva, which pours 83.5 km 3 per year, the Vistula (30.4 km 3 per year), the Neman (20.8 km 3 per year) and the Daugava (19.7 km 3 per year). In different areas of the Baltic Sea, the proportion is not the same. For example, in the Gulf of Bothnia, rivers give 188 km 3 per year, the volume of continental waters is 109.8 km 3 / year. The Gulf of Riga receives 36.7 km 3 /year and in the central part of the Baltic is 111.6 km 3 /year. Thus, the eastern regions of the sea receive more than half of all continental waters.
During the year, rivers bring an unequal amount of water to the sea. If the full flow of rivers is regulated by a lake, as, for example, near the Neva River, then a greater flow occurs in the spring-summer period. If the full flow of rivers is not regulated by lakes, as, for example, near the Daugava River, then the maximum flow is noted in spring and a slight increase in autumn.
are practically not observed. The current affecting surface waters arises under the influence of winds and river runoff. In winter, the waters of the Baltic Sea are covered with ice. But during one and the same winter, the ice can melt several times and again bind the waters. This sea is never completely covered with ice.
Fishing is widely developed in the Baltic Sea. Baltic herring, sprat, cod, whitefish, lamprey, salmon and other types of fish are caught here. Also in these waters, a large amount of algae is mined. There are many marine farms on the Baltic Sea where the most sought-after fish species are grown. There are a large number of placers on the coast of the Baltic Sea. Amber mining works are carried out in the region. There is oil in the bowels of the Baltic Sea.
Navigation is widely developed in the waters of the Baltic Sea. Sea transportation of various goods is constantly carried out here. Thanks to the Baltic Sea, it maintains close economic and trade relations with Western European countries. There are a large number of ports on the coast of the Baltic Sea.
Window to Europe
The Baltic Sea is an inland sea of the Atlantic Ocean basin and is located in a shallow depression between the Scandinavian Peninsula and the European continent. Through the system of the Danish Straits, through the North Sea, the Baltic Sea is connected to the ocean.
The surface area is 386 thousand sq. km, the average depth is 71 m, the maximum depth is 459 m (Landsortsupet basin south of Stockholm).
The ancient Slavs called this sea the 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 depression in which the sea is now located was filled with ice, the process of melting of which led to the formation of a lake with fresh water.
About 14 thousand years ago, this lake joined the ocean as a result of the sinking of land areas - the lake turned into a sea. Then, after the next rise of land in the region of Central Sweden, the connection between the sea and the ocean broke, and it again turned into a closed lake-type reservoir.
Approximately 7 thousand years ago, another land subsidence occurred in the area of the modern Danish Straits and the connection of the lake with the Atlantic resumed.
Subsequent fluctuations in land level led to the formation of the modern Baltic Sea.
The rise of land in the area continues at the present time. Thus, in the area of the Gulf of Bothnia, the bottom rise is approximately 1 m per 100 years.
Climate in the area of marine temperate, characterized by small seasonal temperature fluctuations, frequent precipitation in the form of rain, fog and snow.
Temperature surface water in summer it reaches +20 degrees C. As you move 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 temperature and the northern bays of the sea are covered with ice. The central and southern regions usually remain ice-free, but in exceptionally cold winters the sea can become completely ice-covered.
Water in the sea it is highly desalinated, 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 Neva, Narva, Vistula, Kemijoki, Zapadnaya Dvina, Neman, Odra can be noted.
currents in the sea they form a cyclonic circulation, often their direction and speed are corrected by the winds.
tides in the sea are very low - 5-10 cm, however, wind surges of water, 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 south, the rocks and stones are replaced by sand-pebble mixtures and sand. Here the shores are low and flat.
Islands of mainland origin, especially many small rocky islets in the northern part of the sea. Large islands: Gotland, Bornholm, Sarema.
Bottom relief the sea is complex. There are many ups and downs here, which appeared as a result of the activity of glaciers, river beds, land fluctuations. However, the elevation changes are small - the sea is shallow.
Animal world The Baltic Sea is relatively poor in represented species. A feature of the marine fauna is the distribution of freshwater and marine animal species in different areas. In the northern, fresher regions, especially near the mouths of the rivers, live mainly freshwater animals and species that easily tolerate desalination. Closer to the Danish Straits, the waters of the sea are much saltier, so you can meet many typical marine life here. The general species composition of the sea is scarce, but rather rich in quantitative terms.
The poverty of the fauna of the sea is also explained by its youth, because in the form that it has now, its age is estimated at only five millennia. According to scientists, another 5,000 years will pass, and the Baltic Sea will again lose contact with the ocean and turn into a large fresh 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 animals living in the Baltic Sea is quite large.
Bottom animal species are represented mainly by worms, gastropods and bivalve mollusks, small crustaceans and bottom fish - flounder, gobies. In some places you can meet the mitten crab - an alien from the North Sea and accustomed here. Near the Danish Straits, there is even a giant among jellyfish - cyanide. 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 only three species of seals are represented in the Baltic Sea: the gray seal (tuvyak), the common seal (seal), and the harbor porpoise, which belongs to toothed cetaceans.
sharks in the Baltic Sea are represented only by the ubiquitous katrans - a small spiny shark, which is dangerous to humans only for its spines on the dorsal fins. But these fish are not settled in all areas of the sea - too desalinated and shallow areas are not suitable for them to live.
However, in the area of the Danish Straits, connecting the Baltic with the North Sea, other predators are sometimes found - herring sharks. No such guests have been registered off the Russian shores of the Baltic Sea.
In conclusion, I would like to note that at present the Baltic Sea is heavily polluted by various chemical and biochemical effluents, as well as by trace elements contained in precipitation. This leads to the mass death of microflora and microfauna, which settle to the bottom in large quantities 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 measures are 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 oceans, 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 during the reign of Peter the Great that became the window to Europe.
general characteristics
The average depth of the Baltic Sea is about 50 meters, the largest recorded depth is 470 meters. The deepest sections are located in the region of Scandinavia, the smallest sections are in the area of the Curonian Spit, 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 thickness of the ice reaches 60 cm. The southern regions of the sea can remain without ice cover all winter. Sometimes floating ice floes are found near the northern shores even in summer. The last case of complete freezing of the Baltic Sea was recorded in 1987.
In the autumn winter period The inflow of North Sea salt waters is increasing due to the decrease in water temperature. Because of this, the salinity in the sea increases.
Geographic features
The Baltic Sea is located in the northwest of Europe. In the north, it reaches almost the Arctic Circle itself, the coordinates of the extreme northern point of the sea are 65 degrees 40 minutes s. sh. In the south, it reaches 53 degrees 45 minutes N. 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 on almost all sides by the coastline, only in the west it has access to the North Sea. The 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 - Bothnian, Curonian, Finnish and Riga. The Curonian Lagoon is separated by the Curonian Spit, territorially belongs to Lithuania and Russia (Kaliningrad region). The Gulf of Bothnia is located between Sweden and Finland, it houses the archipelago of the Åland Islands. The Gulf of Finland is located in the east, adjacent to it are the shores of Finland, Estonia and Russia (St. Petersburg).
Baltic Sea: salinity and temperature regime
The temperature of the water surface in the central part is 15-17 degrees. In the Gulf of Bothnia, this figure does not rise above 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 in this sea, the salinity is low. In addition, it does not have constant indicators. So, in the area of the Danish coast, the salinity of the water of the Baltic Sea is 20 ppm on the surface. At depth, the indicator can reach up to 30 ppm. The salinity of the surface waters of the Baltic Sea changes the amount in an easterly direction to a smaller side. In the Gulf of Finland, this figure is not more than 3 ppm.
Observations in last years recorded a tendency to increase the percentage of salinity. This figure has increased by 0.5% compared to 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.
Climate of the Baltic Sea
The Baltic has 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 currents from the Arctic drops the temperature to -35 degrees for a short time. In winter, the north wind prevails, which causes cold winter and a long, drawn-out spring.
In summer, the wind direction changes to west and southwest. On the coast, rainy and cool summer weather is established. Dry hot days in the Baltic are a rarity. The average July temperature here is 14-19 degrees.
The average salinity of the surface waters of the Baltic Sea depends on the season. The period of strong winds falls on the end of autumn and winter. During a storm in November, the waves rise to 6 meters. In winter, ice prevents the formation of high waves. At this time, salinity decreases.
Animal world
The Baltic Sea, the salinity of which has different indicators in different places, 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 - the mitten crab.
Most commercial fish species choose central waters for habitat, where the average salinity of the surface waters of the Baltic Sea is 7-9 ppm.
In bays with almost fresh water, there are pike, bream, crucian carp, roach, ide, burbot, eel. On an industrial scale, Baltic herring, cod, sprat, salmon and sea trout are caught here.
Spa vacation
Due to the cool climate, the resorts of the Amber Region 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 to even 20 degrees.
However, not everyone likes hot crowded beaches. Many people prefer to combine a beach holiday with an active one, for example, with the study of culture and sights. The beaches of the Baltic Sea are very a good option. You can choose the resort of Palanga, Jurmala, Gdansk, Sopot, Svetlogorsk and others. The ideal time to relax here is July and the first half of August, when the water temperature warms up to 25 degrees. Temperatures of 25-27 degrees were recorded in the shallow waters of the Gulf of Riga.
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 the only exit through the Danish straits, there is no possibility of natural self-purification.
The following main water pollutants can be distinguished:
- industrial waste, Agriculture and utilities that come from urban sewers, often led directly into the sea;
- heavy metals - come from city drains, some fall out with precipitation;
- spilled oil products - in the era of the development of shipping, the 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 termination of oxygen access to its inhabitants.
The main sources of water pollution:
- active shipping;
- accidents on industrial enterprises and power plants;
- industrial and household drains;
- polluted rivers flowing into the sea.
Helsinki Convention
In 1992, nine states of the Baltic basin signed a convention on the observance of environmental and maritime rights. The main body is the commission headquartered in Helsinki. The main goal of the commission is to develop and carry out activities aimed at protecting the ecology of the marine environment, conducting research, and promoting the safe navigation of ships.
At the head of the commission for a period of two years are alternately states with access to the sea. From 2008 to 2010, Russia held the chairmanship.
Drunken forest and amber
In the Kaliningrad region on the Curonian Spit there is an unusual place, popularly referred to as the Dancing or Drunken Forest. On a small area (within 1 square km), pine trees planted under the USSR grow. The bottom line is that the trees are strangely curved, and some are even twisted into a loop. Scientists cannot accurately explain this phenomenon. Versions are different: the climatic factor, genetics, attack pests and even the influence of space. There are rumors that there are no sounds in the forest and mobile communications are lost. The mystery of the forest annually attracts domestic and foreign tourists.
In autumn, when a storm begins, along with the sand, the sea throws amber ashore. Mainly on the coast of Poland, Russia, Germany. This period is awaited by local craftsmen and visiting adventurers. There is a belief that amber is a wish fulfillment stone. 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 its uniqueness.
Baltic "Titanic"
In 1994, on the night of September 28, a disaster occurred at sea, the mystery of which remains a mystery to this day. On the evening of September 27, the ferry "Estonia" left Tallinn for its last voyage. There were about 1,000 passengers and crew on board. The ship has been making a regular voyage to Stockholm for a long time. The route is familiar, no unforeseen situations were expected on the route. The sea was stormy, but neither the passengers nor the crew members were bothered by this. The usual Baltic autumn, it was believed that a storm was not terrible for a ship of this type.
Closer to midnight, the storm intensified, but the passengers were calm and prepared for bed. By that time, the ferry had departed from the port for 350 km. At this time, the ferry met with the oncoming ship "Mariella". After one in the morning, a distress signal was received from the ferry, after which the ship disappeared from the radar. "Mariella" and the ships nearby hurried to the place of the tragedy. By 3:00 am, 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, it enters 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 channels with the North and White seas. In the first case, this is the Kiel Canal (length 98 km). It allows ships, without going around Jutland, to immediately enter the North Sea. In the eastern part of the channel is the German city of Kiel, in the western city of Brunsbüttel. Concerning White Sea, then the path to it passes through the Belomorkanal.
In a natural way, the Baltic is connected with the North Sea through the Kattegat (200 km long) and Skagerrak (240 km long) straits. This is a body of water between Jutland and Scandinavia.
gulfs
There are the following large bays in the Baltic: Botanical, Finnish, Riga, Curonian.
Botanical Bay is located in the northern part of the reservoir between Sweden and Finland. In the southern part it has the Åland 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 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. At the junction of this small body of water with the sea is the city of Klaipeda.
Islands
The Åland Islands are an archipelago in the Botanical Bay. It has 6757 islands, but only 60 people live. The largest island is Aland with an area of 685 sq. km. The total area of the archipelago is 1552 sq. km.
Gotland Island (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 will live on it.
Another Swedish island is called Öland. Its area is 1342 sq. km. 25 thousand people live on this piece of land. Every summer they receive at least 500 thousand tourists.
The island of Bornholm, although located not far from the Swedish coast, belongs to Denmark. Its area is 588 sq. km. 42 thousand people live on it. From the island to Copenhagen 169 km, and to Sweden 35 km.
Poland owns the island of Wolin with an area of 265 sq. km. On it is the city of Wolin 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 is wholly owned by Estonia. As for Saaremaa, its area is 2.7 thousand square meters. km with a population of 35 thousand people. There are 4 large and approximately 500 small islands in the archipelago. Their total area is about 4 thousand square meters. km.
Rivers flowing into the Baltic Sea
Rivers such 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) flow into the salty reservoir. ), 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 fresh water. They come from rivers and as a result of precipitation. Surface saline 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 small. Their size does not exceed 20 cm.
The wind has a much greater influence on the water level off 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 oscillation amplitude reaches 50 cm.
As for storms, the Baltic Sea is generally calm. The height of the waves does not exceed 4 meters. In rare cases, winds can create waves with a height of 10 meters. Since the salinity of the water is low, in winter the hulls of ships may be subject to icing.
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 up to 60-65 cm. The southern and central parts of the reservoir are not covered with ice. The ice cover melts in April. In the north, floating ice floes can be found in the month of June. Since 1720, the reservoir has completely frozen over 20 times. The last such case was recorded in January 1987. During this period, there was an extremely severe 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. The cause of poor transparency is often plankton.
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 are 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.
In 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 it reaches 30 ppm. In the center of the reservoir, salinity at the surface is 7-8 ppm. In the north it is 3 ppm, and in the east 2 ppm. With depth, these figures increase and reach 13-14 ppm.
Helsinki Convention 1992
In 1992, the states whose shores are washed by the Baltic Sea signed a convention on 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 Commission for the Protection of the Marine Environment. The contracting parties are Russia, Sweden, Finland, Estonia, Latvia, Lithuania, Denmark, Germany, Poland. Instruments of ratification were deposited by 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 have towards the unique region formed by the Baltic waters. Its flora and fauna should not be at risk of ecological catastrophe.
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 outskirts of the Gulf of Finland (the territory of the Leningrad Region).
The Baltic Sea is deeply incised into the northwestern part of Eurasia. This is an inland sea, connected with the North Sea of the Atlantic Ocean by the system of the Øresund (Sund), Great Belt, Small Belt straits, known collectively as the Danish Straits. They pass into the deep and wide straits of the Skagerrak, Kattegat, which already belong to the North Sea, which is directly connected with.
The area of the Baltic Sea is 419 thousand km2, the volume is 21.5 thousand km3, the average depth is 51 m, the greatest depth is 470 m.
About 250 rivers flow into the Baltic Sea. The largest rivers are Vistula, Oder, Neman, Daugava, Neva. The Neva brings the largest amount of water per year - an average of 83.5 km3.
The Baltic Sea stretches from the southwest to the northeast, and its greatest length is 1360 km. The widest point of the sea is 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 sea lies entirely within the shelf. The bottom of its basin is indented by underwater depressions, separated by hills and socles of islands.
The Baltic Sea is characterized by a long coastline. It has many bays, coves and big number islands. The sea represents a set of individual basins: the zone of the Danish Straits, the open or central part of the sea and three large bays - Bothnian, Finnish and Riga, which account for almost half of the sea.
Numerous islands of the Baltic Sea are located both off 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, Fyn, Lolland, Falster, Langeland, Mön, Bornholm; Swedish - Gotland, Eland; German - Rügen and Fehmarn; - Saaremaa and Hiiumaa.
The coasts 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 gulfs, framed by islands composed of crystalline rocks. They are mostly low, sometimes naked, and in some places overgrown with coniferous forest. The southern shores are low-lying, consist of sand and have a large number of shoals. In some places, along the coast, chains of sand dunes stretch here, and long spits protrude into the sea, forming large lagoons desalinated by the flow of rivers. The largest of these shallow bays are Curonian and Vistula.
The 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, 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 of the Neva river delta, somewhat elongated along the strike of the gulf. 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 of maritime temperate latitudes with features of continentality. The peculiar configuration of the sea and a significant length from north to south and from west to east create differences in climatic conditions in 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 in winter, the Icelandic Low and the Siberian High interact intensively, which intensifies 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 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 High, the air temperature over the sea drops to –30°С and even to –35°С.
In summer, predominantly western, northwestern 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°C in the Gulf of Bothnia and 16–18°C in the rest of the sea. Hot weather is rare. It is caused by short-term inflows of warm Mediterranean air.
The temperature conditions of the waters of the Baltic Sea in different parts of it are not the same and depend not only on geographical location places, but also on the meteorological and hydrological features of the area. The heating of the surface by the rays of the sun, the runoff of river waters and the inflow of deep oceanic waters are of the greatest importance for the temperature regime of the Baltic Sea. 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°С in the southern part of the sea and near zero in the northern Bothnian region.
During the summer months, surface water temperatures are generally close to air temperatures. Near the eastern shores, the water temperature is higher due to the influence of warm, southward land masses, and along the western, Swedish, coast, it 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 chilled land masses of the mainland, and the western parts of the sea during this period experience a regular influx of warm air masses from 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 inflow of river waters from the eastern Baltic. In the northern and central regions of the basin, salinity somewhat decreases from east to west, since in 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 the bays.
Almost throughout the sea, a significant increase in salinity from the surface to the bottom is noticeable. 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 shock layer (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 horizons of 70–80 m; deeper, at 80–100 m, there is a halocline, and then salinity slightly increases to the bottom. In the Gulf of Bothnia, salinity increases from the surface to the bottom only by 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 salinity, respectively. deep waters. In the autumn-winter season, salinity upper layers increases slightly due to contraction and deflection during ice formation. In spring and summer, salinity on the surface decreases by 0.2–0.5‰ compared to the cold half of the year. This is explained by the desalination effect of continental runoff and the spring melting of ice. In addition to seasonal fluctuations in salinity, the Baltic Sea, unlike many seas of the World Ocean, is characterized by its significant interannual changes. 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.
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 3–4 m long. The largest waves occur in November. In winter, with more strong 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 waters 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 emerging from the Gulf of Bothnia and the Gulf of Finland. 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 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 passes to a horizon 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.
Due to the high degree of isolation from the World Ocean, the tides in the Baltic Sea are almost invisible. Fluctuations in the tidal level at individual points do not exceed 10–20 cm. Two minimums and two maxima are clearly expressed in the seasonal course of the Baltic Sea level. lowest level 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 difference in level heights between the summer maximum and the spring minimum is 22–28 cm. It is larger in bays and smaller in the open sea.
Surge fluctuations in sea 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. 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 of the Baltic Sea regime.
Associated with sea level fluctuations catastrophic floods v .
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 main problems of the Baltic Sea are related to the gradual deterioration of oxygen conditions in the deep layers of the sea, which has been observed in recent decades. In some years, oxygen disappears completely already at a depth of 150 m, where it forms hydrogen sulfide. These changes are the result of both natural changes in the environment, mainly temperature, water salinity and water exchange, and anthropogenic impact, which is expressed mainly in an increase in the supply of nutrient salts in the form various forms nitrogen and phosphorus.
The importance of the Baltic Sea in national economy countries of the region and the ever-increasing negative impact of anthropogenic factors on the quality of the marine environment require urgent measures to be taken to guarantee the cleanliness of the sea.
Pollution enters the sea directly from sewage or from ships, diffusely across rivers or . The main mass of pollutants is brought into the sea with the flow of rivers (Neva, Vistula) both in a dissolved state and adsorbed on suspension. 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. Every year, about 300 tons of oil products enter the Gulf of Finland from various sources. The main mass of nitrogenous compounds enters the sea diffusely, as well as sulfur compounds, which enter the marine environment mainly through the atmosphere. Toxic substances are discharged mainly by industry. different character pollution complicates the struggle for the purity of the marine environment and requires the implementation of 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 constant representative points of the reservoir.
The quality of the marine environment of the Baltic Sea as a whole 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. Great harm is caused by accidental spills of oil products from tankers. The monitoring results will make it possible to periodically check the state of the marine environment, i.e., to identify the dynamics of marine pollution.
Russian-owned two small plots the bottom of the coastal part of the Baltic Sea are sharply different in relation to 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 that part of the bay, which is located east of Kotlin Island, between it and the Neva delta. This happened several years ago after the construction of a dam running from Kotlin Island to the northern and southern mainland shores. An important element geoecological situation in the eastern part of the Gulf of Finland are 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 bottom and coasts.
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