Baltic Sea

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Baltic Sea,

arm of the Atlantic Ocean, c.163,000 sq mi (422,170 sq km), including the Kattegat strait, its northwestern extension. The Øresund, Store Bælt, and Lille Bælt connect the Baltic Sea with the Kattegat and Skagerrak straits, which lead to the North Sea; the Kiel Canal, across the Jutland peninsula, is a more direct connection with the North Sea. The Baltic Sea is connected with the White Sea by the White Sea–Baltic Canal, and with the Volga River by the Volga-Baltic Waterway. The Gulf of Bothnia, the Gulf of Finland, and the Gulf of Riga are the chief arms of the Baltic Sea. Of the many islands in the sea, the principal ones are Sjælland, Fyn, Lolland, Falster, and Bornholm (Denmark); Öland and Gotland (Sweden); the Åland Islands (Finland); Saaremaa (Estonia); and Rügen (Germany). Most of the Baltic is shallow, and its tides are less pronounced than those of the North Sea. The salinity of the sea is reduced by the many rivers that enter it (the Oder, Vistula, Dvina, Tornälven, Umeälv, Angermanälven, and Dalälven), and parts of the sea freeze over in winter. The Baltic was frequented from ancient times, especially because of the amber found along the coast. In the late Middle Ages commerce on the Baltic was dominated by the Hanseatic LeagueHanseatic League
, mercantile league of medieval German towns. It was amorphous in character; its origin cannot be dated exactly. Originally a Hansa was a company of merchants trading with foreign lands.
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. Copenhagen, Szczecin, Gdańsk, Riga, St. Petersburg, Helsinki, and Stockholm are the chief ports. Heavy industrialization of the countries bordering the Baltic in the 20th cent. has resulted in the massive environmental degradation of the sea and the endangerment of many of its wildlife species. This problem began to be addressed in the 1990s.

Baltic Sea

 

called the Varangian Sea by the ancient Slavs.

Physical geographic survey. The Baltic Sea is a mediterranean (intracontinental) sea of the Atlantic Ocean; it extends deeply into the European continent. It is connected with the North Sea by the Øresund (the Sound), the Store Baelt, the Lille Baelt, the Kattegat, and the Skagerrak. The Baltic is surrounded by the coasts of the USSR, Poland, the German Democratic Republic, the Federal Republic of Germany, Denmark, Sweden, and Finland. The seaward boundary of the Baltic Sea runs along the southern entrances of the Øresund Strait, the Store Baelt, and the Lille Baelt. The area of the Baltic is 386,000 sq km, the average depth is 71 m, and the average volume of water is 22,000 cu km. The shores of the Baltic Sea on the south and southeast are predominantly lowland, sandy, and characterized by lagoons. On the landward side are dunes covered with forest; the seaward side has sandy and pebbly beaches. In the north the shores are high and rocky, predominantly of the skerry type. The shoreline, greatly incised, forms numerous bays and gulfs.

Among the largest gulfs are the Gulf of Bothnia (a sea, according to physical geographic standards), Gulf of Finland, Gulf of Riga, Courland Gulf (in Russian, Kurshskii Zaliv), Gulf of Gdansk, and Stettin Lagoon. The islands of the Baltic Sea are of continental origin. There are numerous small rocky islands or skerries, located along the northern coasts and concentrated in the groups of the Vaasa and Ahvenanmaa islands. Among the largest of them are Gotland, Bornholm, Saaremaa, Muhu, Hiumaa, Åland, and Rügen. A large number of rivers flow into the Baltic, the largest being the Neva, the Zapadnaia Dvina, Neman, Vistula (in Russian, Visla), Oder, and others.

GEOLOGICAL STRUCTURE AND RELIEF OF THE BOTTOM. The Baltic Sea is a shallow shelf sea. Depths of 40–100 m predominate. The shallowest regions are the straits of the Kattegat (average depth of 28 m), Øresund, the Store Baelt and Lille Baelt, the eastern parts of the Gulf of Finland and the Gulf of Bothnia, and the Gulf of Riga. These parts of the sea bottom have an even aggradation relief and a well-developed cover of loose deposits. The larger part of the floor of the Baltic Sea is characterized by very rugged relief, and there are relatively deep troughs such as the Gotland (249 m), the Bornholm (96 m), the trough off the Kvarken Islands (244 m), and the deepest, the Landsort to the south of Stockholm (459 m). There are numerous stony ridges, and in the central portion of the sea one can trace scarps which are the continuations of Cambrian-Ordovician (from the north coast of Estonia to the northern extremity of Aland Island) and Silurian glints (a local type of precipice), underwater valleys, and glacial aggradation landforms which have been flooded by the sea.

The Baltic Sea occupies a depression of tectonic origin, and this depression is a structural element of the Fennoscandian Shield and its slope. According to present-day theories, the basic unevennesses of the sea’s floor have been caused by block tectonics and by structural denudation processes. The latter, in particular, have been the origin of the underwater scarps of glints. The northern portion of the sea bottom is composed predominantly of Precambrian rock overlaid with a broken cover of glacial and recent sea deposits. In the central portion of the sea, the bottom is composed of Silurian and Devonian rock, covered toward the south by a series of glacial and sea sediments of considerable thickness.

The presence of underwater river valleys and the absence of sea sediments beneath the series of glacial deposits show that in preglacial times the Baltic Sea was dry land. During at least the last Ice Age, the basin of the Baltic Sea was completely covered with ice. Only about 13,000 years ago the Baltic was connected with the ocean, allowing seawater to fill the basin. The Yoldia Sea was formed (named after the Yol-dia mollusk). A somewhat earlier phase (15,000 years ago) of the Yoldia Sea was preceded by the phase of the Baltic Glacial Lake, which did not communicate with the sea. Around 7,500–9,000 years ago, as a result of tectonic uplifting in central Sweden, the connection of the Yoldia Sea with the ocean was broken, and the Baltic Sea again became a lake. This phase in the development of the Baltic Sea is known as the Ancylus Lake (from the Ancylus mollusk). A new subsidence of dry land in the region of the present-day Danish Straits, occurring around 7,000–7,500 years ago, and a broad transgression led to the restoration of the connection with the ocean and to the formation of the Litorina Sea. The level of the last sea was several meters higher than the present-day Baltic, and the salinity was greater. The deposits of the Litorina transgression are widely known on the present-day coast of the Baltic Sea. The age-old uplifting in the northern part of the Baltic Sea basin is still continuing, reaching 1 m per century in the north of the Gulf of Bothnia and gradually diminishing to the south.

CLIMATE. The climate of the Baltic Sea is marine and temperate, being under the strong influence of the Atlantic Ocean. The climate is characterized by comparatively small annual fluctuations in temperature, by frequent precipitation which is rather evenly distributed over the year, and by fogs in the cold and transitional seasons. During the year, westerly winds prevail, caused by the cyclones coming in from the Atlantic. Cyclonic activity reaches its greatest intensity during the autumn and winter months. At this time the cyclones, accompanied by strong winds and frequent storms, cause major rises in the water level along the coast. During the summer months the cyclones weaken and become less frequent. The incursion of anticyclones is accompanied by easterly winds.

The extension of the Baltic Sea across 12 meridian degrees determines the marked differences in the climatic conditions of its individual regions. The mean air temperature in the southern part of the Baltic Sea is -1.1° C in January and 17.5° C in July; in the middle section the mean temperature is -2.3° C in January and 16.5° C in July. In the Gulf of Finland, the mean temperature in January is -5° C and in July 17° C. In the northern part of the Gulf of Bothnia the mean temperature in January is -10.3°C and in July, 15.6° C. Cloudiness in the summer is around 60 percent and in the winter more than 80 percent. The mean annual amount of precipitation in the north is around 500 mm and in the south over 600 mm; in certain regions it reaches 1,000 mm. Fogs occur most often in the southern and middle portions of the Baltic Sea, an average of nearly 59 days a year, and least often in the north of the Gulf of Bothnia (up to 22 days per year).

HYDROLOGICAL CONDITIONS. The hydrological conditions of the Baltic Sea are determined basically by its climate, by the excess of fresh water, and by the exchange of water with the North Sea. The surplus of fresh water, equivalent to 472 cu km per year, is formed from continental drainage. The quantity of water received in precipitation (172.0 cu km per year) equals the evaporation. The exchange with the North Sea averages 1,659 cu km per year (1,187 cu km of saltwater and 472 cu km of fresh water). Fresh water leaves the Baltic Sea for the North Sea via the outflow current, and salty water is carried by an abyssal current through the straits from the North Sea into the Baltic. The strong westerlies usually cause an influx of water, whereas easterlies cause an outflow of water from the Baltic Sea through all the sections of the 0resund Straits, the Store Bælt, and the Lille Bælt.

The currents of the Baltic Sea form a counterclockwise circulation. Along the southern coasts, the current heads east; along the east coast, it moves to the north; along the western coast it flows south; and along the northern coast, it moves to the west. The speed of these currents varies from 5 to 20 cm per second. Under the influence of winds, the currents can change direction, and their speed close to shore can reach 80 cm per second and more, and in the open sea, 30 cm per second.

The water temperature on the surface in August is 15–17° C in the Gulf of Finland, 9–13° C in the Gulf of Bothnia, 14–18° C in the central portion of the sea, and up to 20° C in the south. In February and March, the temperature in the open sea is 1–3° C; in the Gulf of Bothnia, the Gulf of Finland, the Gulf of Riga, and other gulfs and bays, it is below 0° C. Salinity of the surface water rapidly decreases as one moves from the straits from 11 parts per thousand (‰) to 6–8‰ (1‰ = 0.1 percent) in the central part of the sea. In the Gulf of Bothnia salinity equals 4–5‰ (in the north of the gulf 2‰), and in the Gulf of Finland 3–6‰ (in the head of the gulf 2‰ and less). In the abyssal and benthic waters, the temperature is 5° C and higher, and salinity varies from 16 ‰ in the west to 12–13‰ in the center and 10°‰ in the north of the sea. During years when there is an increase in the influx of water, salinity rises in the west to 20‰, and in the central portion of the sea to 14–15‰, but during years when there is a reduced influx, it declines to 11‰ in the middle portion of the sea.

Ice ordinarily appears at the beginning of November in the north of the Gulf of Bothnia and reaches its greatest extent at the beginning of March. At this time, much of the Gulf of Riga, the Gulf of Finland, and the Gulf of Bothnia is covered with fixed ice. The central part of the sea ordinarily is free of ice.

The quantity of ice in the Baltic Sea varies from year to year. During exceptionally severe winters, virtually the entire sea is covered with ice, but in mild ones only the gulfs. The northern portion of the Gulf of Bothnia is covered with ice 210 days a year, and in the middle section, 185 days. The Gulf of Riga is covered 80–90 days, and the Danish Straits some 16–45 days.

The level of the Baltic Sea is subject to fluctuation under the influence of changes in wind direction, atmospheric pressure (seiches—periodic long waves), and the influx of river water and water from the North Sea. The period of these changes varies from several hours to several days. Cyclones in rapid succession cause fluctuations in the level of up to 0.5 m and more along the shores of the open sea and up to 1.5–3 m in the heads of bays and gulfs. Particularly great increases in the water level occur in the inlet of the Neva; these increases as a rule are a consequence of the effect of the wind on the crest of a long wave. The greatest rise in the water level in Leningrad was noted in November 1824 (around 410 cm) and in September 1924 (369 cm).

The fluctuations of the level caused by tidal action are extremely slight. The tides are of an irregular semidiurnal, irregular diurnal, and diurnal character. The amount varies from 4 cm (Klaipeda) to 10 cm (the Gulf of Finland).

FAUNA. The fauna of the Baltic Sea includes relatively few species but is rich quantitatively. Inhabitants of the Baltic Sea are a brackish water race’ of Atlantic herring (Baltic herring), the Baltic sprat, cod, flounder, salmon, eel, smelt, the European cisco (Coregonus albula), whitefish, and perch. Mammals are represented by the Baltic seal. Intensive fishing is carried out in the Baltic Sea.

History of research. Russian hydrographic and cartographic work started in the Gulf of Finland at the beginning of the 18th century. In 1738, F. I. Soimonov published an atlas of the Baltic Sea, which had been compiled using Russian and foreign sources. In the middle of the 18th century, A. I. Nagaev conducted many years of research in the Baltic Sea, and he compiled detailed sailing directions. The first deep-water hydrological research was carried out in the middle of the 1880’s by S. O. Makarov. Since 1920, hydrological work has been carried out by the Hydrographic Administration and the State Hydrological Institute; after the Great Patriotic War of 1941–45, extensive interdisciplinary research was undertaken under the leadership of the Leningrad Division of the USSR State Oceanographic Institute.

IU. D. MIKHAILOV and O. K. LEONT’EV

Historical survey. In the history of the peoples of Europe, the Baltic Sea since antiquity has played an important role. In the early Middle Ages, the chief role in trade and navigation on the Baltic was played by the Scandinavians (the Varangians; hence the ancient Slavic name of the Baltic Sea, the Varangian Sea), and the Slavs. From the end of the 10th century and the beginning of the 11th century, the German merchants began to be more and more active. The major centers of early medieval Baltic trade were Hedeby (on the Jutland Peninsula), Birka (on Lake Malaren), Visby (on the island of Gotland), and somewhat later, Sigtuna, Schleswig, Wolin, Novgorod, Gdansk, and others. The advance of German, Danish, and Swedish feudal lords in the Baltic in the 12th and 13th centuries and the capturing of the southeastern coast of the Baltic by the Teutonic Knights caused serious harm to the positions of the Slavic states on the Baltic Sea. In the 13th and 14th centuries, the dominant role in Baltic trade began to be played by the North German Hanseatic League and its main center, Lübeck (particularly after the victorious Hanseatic war against Denmark, which up to this time had controlled the trade route between the Baltic and the North Sea). The significance of the Baltic Sea as the main water artery for contacts between Eastern and Western Europe (in the north of the continent) became particularly great in the 16th and 17th centuries because of the growing role of trade in the economy and politics of the European states. Between the Eastern European powers, the struggle developed for hegemony on the Baltic Sea (“Dominium maris Baltici” in Latin, the diplomatic language of that age). This struggle played a major role in the general European and regional conflicts of the era, such as the Livonian War of 1558–83 (which for the Russian state was an important stage in the struggle to reach the Baltic) and the numerous Danish-Swedish and Polish-Swedish wars, as well as the Thirty Years’ War of 1618–48. As a result of these wars, Swedish hegemony over the Baltic Sea was established in the middle of the 17th century. The victory of Russia over Sweden in the Northern War of 1700–21 provided Russia with an egress to the Baltic and established Russian hegemony in the eastern Baltic. Russia took possession of the eastern coast of the Baltic Sea with the very important ports of Revel (Tallin), Narva, and Riga, the fortress of Vyborg, and others. Founded in 1703, St. Petersburg soon became the country’s main foreign trade port on the Baltic, with Kronstadt becoming the main naval fortress and the main base for the first Russian Baltic Fleet. From the end of the 19th century, the position of Germany was significantly strengthened; the Germans built a strong navy and a number of naval bases. It also built the Kiel Canal (1886–95), which connected the Baltic and the North Sea. The situation changed after the defeat of Germany in World War I. (The basic forces of the German Navy were destroyed, and the naval armament of Germany was limited.) After the Nazis seized power (1933), German imperialism, with support from the Western powers (the Anglo-German Naval Agreement of 1935 and others), endeavored to resurrect a navy on the Baltic. The defeat of fascist Germany in World War II, the strengthening of Soviet positions on the Baltic, and the creation of the Polish People’s Republic and the German Democratic Republic fundamentally altered the balance of forces and the entire situation on the Baltic in favor of the socialist nations.

Economic geographic survey. The economic significance of the Baltic is determined by its central position in relation to the economically developed states located along its shores—that is, the USSR, Poland, East Germany, West Germany, Denmark, Sweden, and Finland. Approximately 140 million persons live in these nations (the USSR being considered as those RSFSR oblasts adjacent to the Baltic Sea and the Union republics of Estonia, Latvia, and Lithuania), producing around 15 percent of the world’s industrial product. The Baltic Sea serves as the shortest outlet from the regions of the Central, West, and Northwest USSR to the world seaways of the Atlantic Ocean. Extensive coastal shipping is also carried out along the Baltic, and goods are shipped between the Black Sea ports and the Baltic. On the Baltic coast are also located the bases of the Soviet expeditionary fishing fleet which fishes in the Atlantic Ocean. A large portion of the foreign trade of Poland, East Germany, Sweden, and Denmark as well as a predominant portion of Finland’s exports and imports pass through the Baltic Sea. Predominating in the cargo turnover of the Baltic Sea are oil products (from the Soviet ports and from the Atlantic Ocean), coal (from Poland and the USSR), lumber (from Finland, Sweden, and the USSR), pulp and paper (from Sweden and Finland), and iron ore (from Sweden). Machinery and equipment also play an important role in cargo turnover, and all the nations located on the coasts and in the basin of the Baltic Sea are major producers and consumers of these products. The outlet from the Baltic to the Atlantic Ocean is through the Øresund Strait, which belongs to the territorial waters of Sweden and Denmark, as well as through the Kiel Canal, which has international status. The major ports of the Baltic Sea are Leningrad, Tallin, Riga, and Kaliningrad (USSR); Gdańsk, Gdynia, and Szczecin (Poland); Rostock-Warnemünde (East Germany); Lübeck and Kiel (West Germany); Copenhagen (Denmark); Malmö, Stockholm, Sundsvall, and Luleå (Sweden); and Turku, Helsinki, and Kotka (Finland).

The Baltic Sea has the following ferry routes: between Copenhagen and Malmö, Trelleborg and Sassnitz (railway ferries), Norrtälje and Turku (auto ferry), and others.

The modern military and political status of the Baltic Sea region is characterized on the one hand by the attempt of imperialist circles to turn the Baltic into one of the NATO bridgeheads (locating NATO air force and naval bases in the western part of the Baltic, and in particular on West German and Danish territories) and on the other by a desire of the progressive forces to turn the Baltic Sea into a zone of peace.

M. N. SOKOLOV

REFERENCES

Betin, V. V. “Ledovye usloviia v raione Baltiiskogo moria i na podkhodakh k nemu i ikh mnogoletnie izmeneniia.” Tr. Gosudar-stvennogo okeanograficheskogo in-ta, 1957, issue 41.
Gidrokhimicheskii rezhim Baltiiskogo moria. Leningrad, 1965.
Egor’eva, A. V. Baltiiskoe more. Moscow, 1961.
Zenkevich, L. A. Biologiia morei SSSR. Moscow, 1963.
Soskin, I. M. Mnogoletnie izmeneniia gidrologicheskikh kharak-teristik Baltiiskogo moria. Leningrad, 1963.

Baltic Sea

[′bȯl·tik ′sē]
(geography)
An intracontinental, Mediterranean-type sea, connected with the North Sea and surrounded by Sweden, Denmark, Germany, Poland, the Baltic States, and Finland.

Baltic Sea

a sea in N Europe, connected with the North Sea by the Skagerrak, Kattegat, and Öresund; shallow, with low salinity and small tides

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