|Max length||1,600 km (990 mi)|
|Max width||193 km (120 mi)|
|Surface area||377,000 km2 (146,000 sq mi)|
|Average depth||55 m (180 ft)|
|Water volume||20,000 km3 (4,800 cu mi)|
The Baltic Sea is a brackish inland sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and the Little Belt. The Kattegat continues through Skagerrak into the North Sea and the Atlantic Ocean. The Baltic Sea is connected by man-made waterways to the White Sea via the White Sea Canal, and to the North Sea via the Kiel Canal. The Baltic Sea might be considered to be bordered on its northern edge by the Gulf of Bothnia, on its northeastern edge by the Gulf of Finland, and on its eastern edge by the Gulf of Riga. However, these various gulfs can be considered to be simply offshoots of the Baltic Sea, and therefore parts of it.
The Baltic Sea is a brackish inland sea, allegedly the largest body of brackish water in the world (other possibilities include the Black Sea and Hudson Bay). The Baltic Sea occupies a basin formed by glacial erosion during the last few Ice Ages.
The Baltic sea is about 1600 km (1000 mi) long, an average of 193 km (120 mi) wide, and an average of 55 m (180 ft, 30 fathoms) deep. The maximum depth is 459 m (1506 ft), on the Swedish side of the center. The surface area is about 377,000 km² (145,522 sq mi) and the volume is about 20,000 km³ (5040 cubic miles). The periphery amounts to about 8000 km (4968 mi) of coastline. 
While Tacitus called it Mare Suebicum after the Germanic people of the Suebi, the first to name it also as the Baltic Sea (Mare Balticum) was eleventh century German chronicler Adam of Bremen. The origin of the latter name is speculative. It might be connected to the Germanic word belt, a name used for two of the Danish straits, the Belts, while others claim it to be derived from Latin balteus (belt). However it should be noted that the name of the Belts might be connected to Danish bælte, which also means belt. Furthermore Adam of Bremen himself compared the Sea with a belt stating that the Sea is named so because it stretches through the land as a belt (Balticus, eo quod in modum baltei longo tractu per Scithicas regiones tendatur usque in Greciam). He might also have been influenced by name of legendary island mentioned in The Natural History by Pliny the Elder. Pliny mentions an island named Baltia (or Balcia) with reference to accounts of Pytheas and Xenophon. It is possible that Pliny refers to island named Basilia ("kingdom" or "royal") in On the Ocean by Pytheas. Baltia also might be derived from "belt" and means "near belt of sea (strait)". Meanwhile others have concluded that the name of the island originates from the Indo-European root *bhel meaning white, fair. Yet another explanation is that, while derived from the afore mentioned root, the name of the sea is related to naming for various forms of water and related substances in several European languages, that might have been originally associated colors found in swamps. Another explanation is that the name was related to swamp and originally meant "enclosed sea, bay" as opposed to open sea.
In the Middle Ages the sea was known by variety of names, the name Baltic Sea started to dominate only after 16th century. Usage of Baltic and similar terms to denote the region east from the sea started only in 19th century.
On the long-term average, the Baltic Sea is ice covered for about 45% of its surface area at the maximum annually. The ice-covered area during such a typical winter includes the Gulf of Bothnia, the Gulf of Finland, Gulf of Riga, Väinameri in the Estonian archipelago, the Stockholm archipelago and the Archipelago Sea. The remainder of the Baltic itself does not freeze during a normal winter, with the exception of sheltered bays and shallow lagoons such as the Curonian Lagoon. The ice reaches its maximum extent in February or March; typical ice thickness in the northernmost areas in the Bothnian Bay, the northern basin of the Gulf of Bothnia, is about 70 cm (28 in) for landfast sea ice. The thickness decreases farther south.
Freezing begins in the northern coast of Gulf of Bothnia typically in middle of November, reaching the open waters of Bothnian Bay in early January. The Bothnian Sea, the basin south of it, freezes on average in late February. The Gulf of Finland and the Gulf of Riga freeze typically in late January.
The ice extent depends on whether the winter is mild, moderate or severe. Severe winters can lead to ice formation around Denmark and southern Sweden. According to William Derham during the severe winters of 1703 and 1708 the ice cover permeated as far as the Danish straits, parts of the Bay of Bothnia and Gulf of Finland, in addition to coastal fringes in more southerly locations such as the Gulf of Riga. In recent years a typical winter produces only ice in the northern and eastern extremities of the Sea. In 2007 there was almost no ice formation except for a short period in March.
In spring, the Gulf of Finland and of Bothnia normally thaw during late April, with some ice ridges persisting until May in the eastern Gulf of Finland. In the northernmost reaches of the Bothnian Bay ice usually stays until late May; by early June it is practically always gone.
During winter, fast ice, which is attached to the shoreline, develops first, rendering the ports unusable without the services of icebreakers. Level ice, ice sludge, pancake ice or rafter ice form in the more open regions. The gleaming expanse of ice is similar to the Arctic, with wind-driven pack ice and ridges up to 15 m, and was noted by the ancients. Offshore of the landfast ice the ice remains very dynamic all year, because of its thickness it is relatively easily moved around by winds and therefore makes up large ridges and piles up against the landfast ice and shores.
The ice cover is the main habitat only for a few larger species. The largest of them are the seals that both feed and breed on the ice, although the sea ice also harbors several species of algae that live in the bottom and inside brine pockets in the ice.
The Baltic Sea flows out through the Danish straits; however, the flow is complex. A surface layer of brackish water discharges 940 km³ per year into the North Sea. Due to the difference in salinity, a sub-surface layer of more saline water moving in the opposite direction brings in 475 km³ per year. It mixes very slowly with the upper waters, resulting in a salinity gradient from top to bottom, with most of the salt water remaining below 40 to 70 m deep. The general circulation is counter-clockwise: northwards along its eastern boundary, and south along the western one (Alhonen 88).
The difference between the outflow and the inflow comes entirely from fresh water. More than 250 streams drain a basin of about 1.6 million km², contributing a volume of 660 km³ per year to the Baltic. They include the major rivers of north Europe, such as the Oder, the Vistula, the Neman, the Daugava and the Neva. Additional fresh water comes from the difference of precipitation less evaporation, which is positive.
An important source of salty water are infrequent inflows of North Sea water into the Baltic. Such inflows, important to the Baltic ecosystem because of the oxygen they transport into the Baltic deeps, used to happen on average every four to five years until the 1980s. In recent decades they have become less frequent. The latest three occurred in 1983, 1993 and 2003 suggesting a new inter-inflow period of about ten years.
The water level is generally far more dependent on the regional wind situation than on tidal effects. However, tidal currents occur in narrow passages in the western parts of the Baltic Sea.
The significant wave height is generally much lower than that of the North Sea. Violent and sudden storms often sweep the surface, due to large transient temperature differences and a long reach of wind. Seasonal winds also cause small changes in sea level, of the order of 0.5 m (Alhonen 88).
The Baltic Sea's salinity is much lower than that of ocean water (which averages 3.5%, or 35‰), as a result of abundant freshwater runoff from the surrounding land; indeed, runoff contributes roughly one-fortieth its total volume per year, as the volume of the basin is about 21,000 km³ and yearly runoff is about 500 km³. The open surface waters of the central basin have salinity of 6 to 8 ‰. At the semi-enclosed bays with major freshwater inflows, such as head of Finnish Gulf with Neva mouth and head of Bothnian gulf with close mouths of Lule, Tornio and Kemi, the salinity is considerably lower. Below 40 to 70 m, the salinity is between 10 and 15 ‰ in the open Baltic Sea, and more than this near Danish Straits.
The flow of fresh water into the sea from approximately two-hundred rivers and the introduction of salt from the South builds up a gradient of salinity in the Baltic Sea. Near the Danish straits the salinity is close to that of the Kattegat, but still not fully oceanic, because the saltiest water that passes the straits is still already mixed with considerable amounts of outflow water. The salinity steadily decreases towards North and East. At the northern part of the Gulf of Bothnia the water is no longer salty and many fresh water species live in the sea. The salinity gradient is paralleled by a temperature gradient. These two factors limit many species of animals and plants to a relatively narrow region of Baltic Sea.
The most saline water is vertically stratified in the water column to the north, creating a barrier to the exchange of oxygen and nutrients, and fostering completely separate maritime environments.
The land is still emerging isostatically from its subsident state, which was caused by the weight of the last glaciation. The phenomenon is known as post-glacial rebound. Consequently, the surface area and the depth of the sea are diminishing. The uplift is about eight millimetres per year on the Finnish coast of the northernmost Gulf of Bothnia. In the area, the former seabed is only gently sloped, leading to large areas of land being reclaimed in, geologically speaking, relatively short periods (decades and centuries).
Bordered by the coasts of Denmark, Sweden, Finland, Russia, Estonia, Latvia, Lithuania, Poland and Germany extends north-eastward of the following limits:
In the Little Belt. A line joining Falshöft ( ) and Vejsnæs Nakke (Ærö: ).
In Guldborg Sound. A line joining Flinthorne-Rev and Skjelby ( ).
The northern part of the Baltic Sea is known as the Gulf of Bothnia, of which the northernmost part is the Bay of Bothnia or Bothnian Bay. The more rounded southern basin of the gulf is called Bothnian Sea and immediately to the south of it lies the Sea of Åland. The Gulf of Finland connects the Baltic Sea with Saint Petersburg. The Gulf of Riga lies between the Latvian capital city of Riga and the Estonian island of Saaremaa.
The Northern Baltic Sea lies between the Stockholm area, southwestern Finland and Estonia. The Western and Eastern Gotland Basins form the major parts of the Central Baltic Sea or Baltic proper. The Bornholm Basin is the area east of Bornholm, and the shallower Arkona Basin extends from Bornholm to the Danish isles of Falster and Zealand.
In the south, the Bay of Gdańsk lies east of the Hel peninsula on the Polish coast and west of Sambia in Kaliningrad Oblast. The Bay of Pomerania lies north of the islands of Usedom and Wolin, east of Rügen. Between Falster and the German coast lie the Bay of Mecklenburg and Bay of Lübeck. The westernmost part of the Baltic Sea is the Bay of Kiel. The three Danish straits, the Great Belt, the Little Belt and The Sound (Ö/Øresund), connect the Baltic Sea with the Kattegat bay and Skagerrak strait in the North Sea. The confluence of these two seas at Skagen on the northern tip of Denmark is a visual spectacle visited by many tourists each year.
The Baltic sea drainage basin is roughly four times the surface area of the sea itself. About 48% of the region is forested, with Sweden and Finland containing the majority of the forest, especially around the Gulfs of Bothnia and Finland.
About 20% of the land is used for agriculture and pasture, mainly in Poland and around the edge of the Baltic Proper, in Germany, Denmark and Sweden. About 17% of the basin is unused open land with another 8% of wetlands. Most of the latter are in the Gulfs of Bothnia and Finland.
The rest of the land is heavily populated.
About 85 million people live in the Baltic drainage basin, 15 million within 10 km (6 mi) of the coast and 29 million within 50 km (31 mi) of the coast. Around 22 million live in population centers of over 250,000. 90% of these are concentrated in the 10 km (6 mi) band around the coast. Of the nations containing all or part of the basin, Poland includes 45% of the 85 million, Russia 12%, Sweden 10% and the others (see below) less than 6% each.
The Baltic Sea somewhat resembles a riverbed, with two tributaries, the Gulf of Finland and Gulf of Bothnia. Geological surveys show that before the Pleistocene instead of the Baltic Sea, there was a wide plain around a big river called the Eridanos. Several glaciation episodes during the Pleistocene scooped out the river bed into the sea basin. By the time of the last, or Eemian Stage (MIS 5e), the Eemian sea was in place. Instead of a true sea, the Baltic can even today also be understood as the common estuary of all rivers flowing into it.
From that time the waters underwent a geologic history summarized under the names listed below. Many of the stages are named after marine animals (e.g. the Littorina mollusk) that are clear markers of changing water temperatures and salinity.
The factors that determined the sea's characteristics were the submergence or emergence of the region due to the weight of ice and subsequent isostatic readjustment, and the connecting channels it found to the North Sea-Atlantic, either through the straits of Denmark or at what are now the large lakes of Sweden, and the White Sea-Arctic Sea.
At the time of the Roman Empire, the Baltic Sea was known as the Mare Suebicum or Mare Sarmaticum. Tacitus in his AD 98 Agricola and Germania described the Mare Suebicum, named for the Suebi tribe, during the spring months, as a brackish sea when the ice on the Baltic Sea broke apart and chunks floated about. The Suebi eventually migrated south west to reside for a while in the Rhineland area of modern Germany, where their name survives in the historic region known as Swabia. The Sarmatian tribes inhabited Eastern Europe and southern Russia. Jordanes called it the Germanic Sea in his work the Getica.
Since the Viking age, the Scandinavians have called it "the Eastern Lake" (Austmarr, "Eastern Sea", appears in the Heimskringla and Eystra salt appears in Sörla þáttr), but Saxo Grammaticus recorded in Gesta Danorum an older name Gandvik, "-vik" being Old Norse for "bay", which implies that the Vikings correctly regarded it as an inlet of the sea. (Another form of the name, "Grandvik", attested in at least one English translation of Gesta Danorum, is likely to be a misspelling.)
In addition to fish the sea also provides amber, especially from its southern shores. The bordering countries have traditionally provided lumber, wood tar, flax, hemp, and furs. Sweden had from early medieval times also a flourishing mining industry, especially on iron ore and silver. Poland had and still has extensive salt mines. All this has provided for rich trading since the Roman times.
In the early Middle Ages, Vikings of Scandinavia built their trade empire all around the Baltic. Later, there were fights for control over the sea with Wendish tribes dwelling on the southern shore. The Vikings also used the rivers of Russia for trade routes, finding their way eventually to the Black Sea and southern Russia. This Viking-dominated period is also referred to as Viking Age.
Lands next to the sea's eastern shore were among the last in Europe to be converted into Christianity in the Northern Crusades: Finland in the twelfth century by the Swedes, and what are now Estonia and Latvia in the early thirteenth century by the Danes and the Germans (Livonian Brothers of the Sword). The Teutonic Knights gained control over parts of the southern and eastern shore of the Baltic Sea, where they set up their monastic state while fighting the Poles, the Danes, the Swedes, the Russians of ancient Novgorod, and the Lithuanians (the last Europeans to convert to Christianity).
In the 12th century, there was intensification of Slavic piracy. Starting in the 11th century, the southern and eastern shores of the Baltic were settled by Germans (and to a lesser extent by Dutch, Danes and Scots) in the course of the Ostsiedlung. The Polabian Slavs were gradually assimilated by the Germans. Denmark gradually gained control over most of the Baltic coast, until she lost much of her possessions after being defeated in the 1227 Battle of Bornhöved.
In the 13th to 17th centuries, the strongest economic force in Northern Europe became the Hanseatic league, which used the Baltic Sea to establish trade routes between its member cities. In the sixteenth and early seventeenth centuries, Polish-Lithuanian Commonwealth, Denmark and Sweden fought wars for Dominium Maris Baltici ("Ruling over the Baltic Sea"). Eventually, it was the Swedish Empire that virtually encompassed the Baltic Sea. In Sweden the sea was then referred to as Mare Nostrum Balticum ("Our Baltic Sea").
In the eighteenth century, Russia and Prussia became the leading powers over the sea. The Great Northern War, ending with Sweden's defeat, brought Russia to the eastern coast. Since then, Russia was a dominating power in the Baltic. Russia's Peter the Great saw the strategic importance of the Baltic and decided to found his new capital, Saint Petersburg at the mouth of the Neva river at the east end of the Gulf of Finland. There was much trading not just within the Baltic region but also with the North Sea region, especially eastern England and the Netherlands: their fleets needed the Baltic timber, tar, flax and hemp.
During the Crimean War, a joint British and French fleet attacked the Russian fortresses by bombarding Sveaborg, which guards Helsinki; Kronstadt, which guards Saint Petersburg; and by destroying Bomarsund in the Åland Islands. After the unification of Germany in 1871, the whole southern coast became German. The First World War was partly fought in the Baltic Sea. After 1920 Poland was connected to the Baltic Sea by the Polish Corridor and enlarged the port of Gdynia in rivalry with the port of the Free City of Danzig.
During the Second World War, Germany reclaimed all of the southern shore and much of the eastern by occupying Poland and the Baltic states. In 1945, the Baltic Sea became a mass grave for retreating soldiers and refugees on torpedoed troop transports. The sinking of the MV Wilhelm Gustloff remains the worst maritime disaster, killing (very roughly) 9,000 people. In 2005, a Russian group of scientists found over five thousand airplane wrecks, sunken warships, and other material mainly from the Second World War, lying at the bottom of the sea.
Since the end of World War II, various nations, including the Soviet Union, the United Kingdom, the United States, and Germany, have disposed of chemical weapons in the Baltic Sea, raising concerns of environmental contamination. Even now fisherman accidentally retrieve some of these materials: the most recent available report from the Helsinki Commission notes that four small scale catches of CW munitions representing approximately 105 kilograms (231 lbs) of material were reported in 2005. This is a reduction from the 25 incidents representing 1,110 kilograms (2,447 lbs) of material in 2003.
After 1945, the German population was expelled from all areas east of the Oder-Neisse line, making room for Polish and Russian settlers. Poland gained a vast stretch of the southern shore, Russia gained another access to the Baltic with the Kaliningrad oblast. The Baltic states on the eastern shore were occupied by the Soviet Union, Poland and East Germany became communist states. The sea then was a border between opposing military blocks: in the case of military conflict, in parallel with a Soviet offensive towards the Atlantic Ocean, communist Poland's fleet was prepared to invade the Danish isles. This border status also impacted trade and travel, and came to an end only after the collapse of the communist regimes in Eastern and Central Europe in the late 1980s.
Since May 2004, on the accession of the Baltic states and Poland, the Baltic Sea has been almost entirely surrounded by countries of the European Union (EU). The only remaining non-EU areas are the Russian metropolis of Saint Petersburg and the Kaliningrad Oblast exclave.
Winter storms begin arriving in the region during October. These have caused numerous shipwrecks, such as the sinking of the ferry M/S Estonia en route from Tallinn, Estonia, to Stockholm, Sweden, in 1994, which claimed the lives of hundreds. Older, wood-based shipwrecks such as the Vasa tend to remain well-preserved, as the Baltic's cold and brackish water does not suit the shipworm.
Approximately 100,000 km2 (38,610 sq mi) of the Baltic's seafloor (a quarter of its total area) is a variable dead zone. The more saline (and therefore denser) water remains on the bottom, isolating it from surface waters and the atmosphere. This leads to decreased oxygen concentrations within the zone. It is mainly bacteria that grow in it, digesting organic material and releasing hydrogen sulfide. Because of this large anaerobic zone, the seafloor ecology differs from that of the neighbouring Atlantic.
The low salinity of the Baltic sea has led to the evolution of many slightly divergent species, such as the Baltic Sea herring, which is a smaller variant of the Atlantic herring. The benthic fauna consists mainly of Monoporeia affinis, which is originally a freshwater species. The lack of tides has affected the marine species as compared with the Atlantic.
Construction of the Great Belt Bridge in Denmark (completed 1997) and the Oresund Bridge-Tunnel (completed 1999), linking Denmark with Sweden, provided a highway and railroad connection between Sweden and the Danish mainland (the Jutland Peninsula). The undersea tunnel of the Oresund Bridge-Tunnel provides for navigation of large ships into and out of the Baltic Sea. The Baltic Sea is the main trade route for export of Russian petroleum. Many of the countries neighboring the Baltic Sea have been concerned about this, since a major oil leak in a seagoing tanker would be disastrous for the Baltic—given the slow exchange of water. The tourism industry surrounding the Baltic Sea is naturally concerned about oil pollution.
Much shipbuilding is carried out in the shipyards around the Baltic Sea. The largest shipyards are at Gdańsk, Gdynia, and Szczecin, Poland; Kiel, Germany; Karlskrona, Sweden; Malmö, Sweden; Rauma, Turku, and Helsinki, Finland; Riga, Ventspils, and Liepāja (Latvia); Klaipėda (Lithuania); and St. Petersburg, Russia.
European Route of Brick Gothic is a touristic route connecting cities with Brick Gothic architecture in seven countries along the Baltic Sea: Sweden, Denmark, Germany, Poland, Lithuania, Latvia and Estonia.
For the first time ever, all the sources of pollution around an entire sea were made subject to a single convention, signed in 1974 by the then seven Baltic coastal states. The 1974 Convention entered into force on 3 May 1980.
In the light of political changes and developments in international environmental and maritime law, a new convention was signed in 1992 by all the states bordering on the Baltic Sea, and the European Community. After ratification the Convention entered into force on 17 January 2000. The Convention covers the whole of the Baltic Sea area, including inland waters and the water of the sea itself, as well as the seabed. Measures are also taken in the whole catchment area of the Baltic Sea to reduce land-based pollution. The Convention on the Protection of the Marine Environment of the Baltic Sea Area, 1992, entered into force on 17 January 2000.
The governing body of the Convention is the Helsinki Commission, also known as HELCOM, or Baltic Marine Environment Protection Commission. The present contracting parties are Denmark, Estonia, the European Community, Finland, Germany, Latvia, Lithuania, Poland, Russia and Sweden.
The ratification instruments were deposited by the European Community, Germany, Latvia and Sweden in 1994, by Estonia and Finland in 1995, by Denmark in 1996, by Lithuania in 1997 and by Poland and Russia in November 1999.
Countries that border on the sea:
Countries that are in the drainage basin but do not border on the sea:
The biggest coastal cities (by population):
Important ports (though not big cities):
North to South:
Despite the three nations' similarities in culture and history, their languages belong to two distinct language families. The Latvian and Lithuanian languages make up the group of Baltic languages which belongs to the Indo-European language family. The Estonian language, on the other hand, is a non-Indo-European language and instead belongs to the Baltic-Finnic subgroup of the Finno-Ugric languages, sharing close cultural and historical ties with the Finnish language and culture.
The peoples of the Baltic countries also belong to different Christian denominations. Believers in Latvia and Estonia are mostly Lutheran (except for Eastern part of Latvia, which is Catholic). Lithuania is principally Catholic.
Each of the three Baltic countries has the language of their respective titular nationality as an official language. Russian is spoken by the majority of the population in all three countries, and English is increasingly spoken as well, especially by the younger generations. Any attempt to speak the native language will be greatly appreciated. German is also spoken by some in all three countries; Finnish is understood in Estonia due to the similarity of Finnish and Estonian, and some Polish is also spoken in Lithuania.
Note on Russian: as the status of the Russian language has been a contentious issue since the collapse of the USSR, and due to heated anti-Russian sentiment, it is advised that if you speak Russian, you attempt to first communicate in the native language, at least to issue greetings and ask if the person speaks Russian. The greatest hostility towards Russian tends to be found in Estonia and Latvia, while Lithuania seems to have the least anti-Russian language sentiment. In the cities, especially Riga, many people may be native speakers of Russian, but in rural areas Russian will be spoken much less.
The international bicycle project, BaltiCCycle  may provide you with a lot of information and help.
|This article is an outline and needs more content. It has a template, but there is not enough information present. Please plunge forward and help it grow!|
BALTIC SEA (Scand. and Ger. Ostsee; Russ. Baltiyskoe More), a sea extending between 54° and 66° N. lat., and 9° and 30 E. long., surrounded by the territories of Sweden, Russia, Germany and Denmark. Its greatest length is about 960 m.; greatest breadth about 400 m.; and length of coast-line, 5000 m.; the central axis runs approximately from south-west to north-east. The Baltic is connected with North Sea by the winding channel between the south of Scandinavia and the Cimbrian peninsula. This channel is usually included in the Baltic. The part of it west of a line joining the Skaw with Christiania fjord receives the name of Skagerrak; the part east of this line is called the Kattegat. At its southern end the Kattegat is blocked by the Danish islands, and it communicates with the Baltic proper by narrow channels called the Sound, the Great Belt and the Little Belt. The real physical boundary between the North Sea and the Baltic is formed by the plateau on which the islands Zealand, Fiinen and Laaland are situated, and its prolongation from the islands Falster and Moen to the coasts of Mecklenburg and Riigen.
East of this plateau the Baltic proper forms a series of hollows or troughs. The first, or Bornholm deep, lies east of the island of Bornholm, and is separated from the next, or Gotland deep, by the Middelbank. Beyond the Middelbank the Danziger Tiefe, an isolated depression, lies to the south-east, while to the northeast the Gotland basin, the largest and deepest of all, extends north-eastwards to the Gulf of Finland. Along the Swedish coast a deep channel runs northward from outside the island of Oland; this is entirely cut off to the south and east by a bank which sweeps eastward and northward from near Karlskrona, and on which the island of Gotland stands, but it communicates at its northern end with the Gotland deep, and near the junction opposite Landsort is the deepest hole in the Baltic (420 metres = 2 3 o fathoms).
An unbroken ridge, extending from Stockholm to Hango in Finland, separates the Baltic basin proper from the depression between Sweden and the Aland Isles, to which the name Aland Haf has been given. North of the Aland Haf a ridge defines the southern edge of another depression, the Bothnian Sea, which in turn is separated from the most northerly division, the Gulf of Bothnia, by a ridge across the narrow Quarken or Kvarken Strait. The Gotland deep may be said to extend directly into the Gulf of Finland, an arm of the Baltic, running eastwards for about 250 m., and separating Finland from Esthonia. Between Esthonia and Courland is the Gulf of Riga, a shallow inlet of roughly circular form, about loo m. in diameter, and nowhere more than 27 fathoms deep.
According to recent computations the total area of the Baltic, including the Skagerrak and Kattegat, is 166,397 sq. m., and its volume 6907 cub. m., giving a mean depth of 36 fathoms, which is markedly less than that of any other arm of the sea of similar area.
In the deeper hollows in the south part of the Baltic the bottom consists almost invariably of either soft brown or grey mud or hard clay, while on the shallow banks and near the low coasts fine sand, of white, yellow or brown colour with small pebbles, is usually found.
At the time of the last great subsidence, in glacial times, an arm of the sea extended across Sweden, submerging a great part of the littoral up to the Gulf of Bothnia, and including the Plies period the this of themnorthe and Baltic were s fg ficiently salt for oysters to flourish. The subsequent upheaval restricted direct communication with the open sea to the Danish channels, and the Baltic waters became fresher: the oyster disappeared, but a number of cold salt-water fishes and crustaceans, and even seals, became acclimatized. It has been suggested that the presence of the remains of these animals indicates a communication to the north with the Arctic Ocean; but in view of the severe climatic conditions still prevailing at the time, this seems an unnecessary assumption. In the next stage of its history the Baltic is transformed by further elevation into a vast freshwater lake, the Ancylus lake of G. de Geer (named from the remains of the mollusc Ancylus fluviatilis), which is supposed to have covered an area of about 220,000 sq. m., including the whole of the present Baltic area and a large part of Finland, with Lake Ladoga. Then followed a subsidence, which not only re-established communication through the Danish channels, but allowed the Baltic to become sufficiently salt for such forms as Cardium edule and Littorina littorea. At this time the Gulf of Bothnia must have suffered greater depression than the Baltic proper, for the deposits of that epoch show a thickness of 100 metres (328 ft.) near Hernosand, but of only 25 metres (82 ft.) in the neighbourhood of Gotland. After this period of subsidence the process of elevation set in which gave the Baltic its present form and physical condition, and appears to be still in progress. Dr R. Sieger has traced a series of isobasic lines, or lines of equal rate of elevation, for portions of Sweden and Finland; these indicate that the movement is now almost nil along the axial lines of the Baltic and the Gulf of Finland, but increases in amplitude northwards to the Gulf of Bothnia and in the direction of the main ridge of the massif of southern Sweden. At Stockholm the rate of elevation is approximately 0.47 metre (=1.54 ft.) in a century.
The coast of the Baltic is rocky only in the island-studded region at the head of the Baltic basin proper - a submerged lake-districtand the littoral generally is a typical morainic land, the work of the last great Baltic glacier. The southern margin of the. Baltic is of peculiar interest. From Schleswig eastwards to Lubeck Bay the coast is pierced by a number of narrow openings or Fohrden, the result of encroachment of the sea caused by subsidence. East of Lubeck, as far as the mouth of the Oder, these give place to Bodden, ramified openings studded with islands: the structure here resembles that of Scania in southern Sweden, a region once joined to both Denmark and Pomerania by an isthmus which was severed by tectonic movements. Beyond the Oder the coast-line is unbroken as far as the Gulf of Danzig. It is then cut into by the estuaries of the Vistula, the Pregel and the Memel. Here the westerly winds have full play, and the coast is rimmed by a continuous line of dunes, which cut off the two great lagoons of the Frisches Haff and Kurisches Haff by sandspits or Nehrungen. The drainage area of the Baltic is relatively large. According to the measurements of Sir J. Murray it extends to 461,450 sq. sea m. (=611,700 sq. English m.) The largest river-basin included in it is that of the Neva in the east, and next in size come the Vistula and the Oder in the south. The narrow parallel troughs, at right angles to the coast, which form the drainage-system of Sweden and western Finland, are a remarkable feature.
Levellings from Swinemunde show that the mean level of the surface of the Baltic at that point is 0.093 metres (_ 305 ft.) below. the surface of the North Sea at Amsterdam, and 0.066 metres (= 216 ft.) below its level at Ostend. A line of levels from Swinemunde through Eger to the Adriatic showed the mean level of the surface of the Baltic to be o 499 metres (1.6 ft.) above that of the Adriatic Sea. The mean level of the surface of the Baltic rises about 0.5 metres (1.6 ft.) from the coast of Holstein to Memel, probably as a result of the prevailing westerly winds; this mean difference is exceeded with strong westerly winds, and disappears or is reversed with easterly winds. The waves of the Baltic are usually short and irregular, often dangerous to navigation. Destructive waves, probably caused by distant earthquakes, called Seebciren (cf. English "bores") have been recorded.
The range of the tides is about one foot at Copenhagen; within the Baltic proper ordinary tides are scarcely perceptible. There is, however, a distinctly marked annual rise and fall due to meteorological influences having a mean range of about 11.4 cm. (0.37 ft.), at Travemunde, and 13.9 cm. (0.46 ft.) at Swinemunde, the maximum occurring at the end of the summer rainy period in August.
The circulation of water in the Baltic proper must be considered apart from the circulation in the channels connecting it with the Circu1 North Sea; and in this relation the plateau connecting the islands Falster and Moen with the coast of Mecklen burg and Rugen must be taken as the dividing line. In the great basins and hollows from Rugen to the Gulfs of Bothnia and Finland the upper layers of water, from 30 to 70 metres (16 to 38 fathoms) in thickness, have almost the same salinity throughout. In these waters a vertical circulation is kept up by convection 287 currents. Beneath these layers are masses of salter water, through which a thermal wave of small amplitude is slowly propagated to the bottom by conduction. These strata are practically stagnant, deficient in oxygen and surcharged with carbonic acid. Their salter waters must have been originally derived from outside, and must therefore have passed over the plateau between Falster and Mecklenburg, but their horizontal extension is checked by the ridges separating the deep hollows in the Baltic from each other. The inflow to the deep basins is intermittent, probably with a long period of flux and reflux.
The circulation in the channels connecting the Baltic proper with the North Sea is of a complex character. It is necessary in the first place to distinguish clearly between outflowing and inflowing waters; in practice this is easily done, as the outflowing water always contains less than 30 parts pro male of salt, and the inflowing water more than 32 pro male. The Baltic receives much more water by rainfall, discharge of rivers, &c., than it loses by evaporation; hence a surplus must be got rid of by an outflowing current which may be named the "Baltic Stream." The following general laws may be laid down with regard to this I. That the Baltic Stream must be a surface current, because it originates from a redundancy of fresh water.
2. That, on account of the earth's rotation, the main part of the Baltic Stream must keep close to the coast of the Scandinavian peninsula.
3. That it must be a periodic stream, because the discharge of the rivers into the Baltic varies with the season of the year. In spring and summer the water from the Baltic is sufficiently abundant to inundate the whole surface of the Kattegat and Skagerrak, but in winter the sources of the Baltic current are for the most part dried up by the freezing of the land water.
All the waters which enter the Skagerrak or Kattegat as undercurrents can be found at the surface of the North Sea. They may be divided according to their origin and salinity as follows: - (a) Ocean water of 35 pro male salinity or more.
(b) North Sea water, the predominant water in the North Sea area, of 34 to 35 pro male salinity.
The deepest water stratum in the Skagerrak is certainly of oceanic origin; it has been found to suffer changes of long period, and it is probably not always composed of water derived from the same part or the same depth of the North Atlantic; this water is, as a rule, deficient in oxygen. The "North Sea" water, of 34 to 35 pro male salinity, does not appear at the surface in the Skagerrak, except as a strip along part of the coast of Jutland, but it is always found as an undercurrent overlying the oceanic water. It enters into all the deep coast channels, and into the Christiania fjord, but it is not always found in the deep channels of the Kattegat. The principal time of inflow of North Sea water is during spring and summer. The bank-water of 32 to 34 pro male salinity is found all along the continental coast of the North Sea and North Atlantic, and it may therefore enter the Skagerrak either from the North Sea or from the north along the coast of Norway. It is probable indeed that an influx of this water occurs from both directions - in August and September from the south, and in the late winter and early spring from the north. The seasonal changes in the distribution of the bank-waters in different parts of the coast are too complex to be briefly explained; their relations to the times of occurrence of various fisheries of the region present many remarkable features, which have been investigated in recent years by the Swedish Commission.
On the west and south coasts of Sweden, and in the Skagerrak south-east of Norway, navigation is interfered with by ice only in severe winters, and then the ice is usually drifting, compact sea-ice being very rare. Between Stockholm and Visby navigation usually ceases at the end of December and begins again about the 10th of April. During very severe winters the Aland Sea is covered with thick ice available for traffic. The south part of the Gulf of Bothnia is covered with ice every winter along the coasts, but rarely, if ever, in its central part. Navigation is interrupted by drifting ice from about the middle of November to the beginning of May, though the port of HernOsand has been known to remain open during a whole winter. The northern Quarken is covered with traversable ice every third or fourth year. The northern part of the Gulf of Bothnia is frozen every winter. In the Gulf of Finland the sea is closed to navigation by ice for about 150 days in the year; but navigation is rendered possible throughout the winter by the use of ice-breakers.
See references to different parts of the subject in the standard books of A. Penck, A. de Lapparent, E. Suess and others. Also Credner, Die Entstehung der Ostsee (Leipzig, 1895); G. de Geer; Om Skandinaviens niveif orandringar under quartarperioden (Stockholm, 1888); R. Sieger, Seeenschwankungen and Strandverschiebungen in Skandinavien (Berlin, 1893); O. Pettersson, "Review of Swedish Hydrographic Research," Scottish Geographical Magazine (1894) N. Ekholm, Om klimatets andringar i geologisk och historisk tid. Ymer (Stockholm, 1899) Publications of the International Council for the Study of the Sea (Copenhagen, since 1902). (H. N. D.)
Many big rivers in the surrounding countries drain into the Baltic Sea. The Baltic Sea is connected to the ocean through the narrow and shallow Danish straits and belts. For this reason, the water has a low content of salt, so the northern parts of the sea freeze over in the winter. The ice can carry cars, and roads are established every winter between the islands in the archipelagos between Sweden and Finland.
For several thousand years the Baltic Sea has connected the countries at her shores. For that reason you will find many cultural similarities in these countries. And since most of these countries are European, this sea is also considered European.frr:Ååstsiie