Baltic Sea

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Baltic Sea
Baltic Sea map.png
Map of the Baltic Sea region
Location Europe
Coordinates 58°N20°E / 58°N 20°E / 58; 20 Coordinates: 58°N20°E / 58°N 20°E / 58; 20 (slightly east of the north tip of Gotland Island)
Type Sea
Primary inflows Daugava, Kemijoki, Neman (Nemunas), Neva, Oder, Vistula, Lule, Narva, Torne
Primary outflows The Danish Straits
Catchment area 1,641,650 km2 (633,840 sq mi)
Basin  countriesCoastal: Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden
Non-coastal: Belarus, Czech Republic, Hungary, Norway, Slovakia, Ukraine [1]
Max. length1,601 km (995 mi)
Max. width193 km (120 mi)
Surface area377,000 km2 (146,000 sq mi)
Average depth55 m (180 ft)
Max. depth459 m (1,506 ft)
Water volume21,700 km3 (1.76×1010 acre⋅ft)
Residence time 25 years
Shore length18,000 km (5,000 mi)
Islands Abruka, Aegna, Archipelago Sea Islands (Åland Islands), Bornholm, Dänholm, Ertholmene, Falster, Fårö, Fehmarn, Gotland, Hailuoto, Hiddensee, Hiiumaa, Holmöarna, Kassari, Kesselaid, Kihnu, Kimitoön, Kõinastu, Kotlin, Laajasalo, Lauttasaari, Lidingö, Ljusterö, Lolland, Manilaid, Mohni, Møn, Muhu, Poel, Prangli, Osmussaar, Öland, Replot, Ruhnu, Rügen, Saaremaa, Stora Karlsö, Suomenlinna, Suur-Pakri and Väike-Pakri, Ummanz, Usedom/Uznam, Väddö, Värmdö, Vilsandi, Vormsi, Wolin
Settlements Copenhagen, Gdańsk, Gdynia, Haapsalu, Helsinki, Kaliningrad, Kiel, Klaipėda, Kuressaare, Kärdla, Lübeck, Luleå, Oulu, Paldiski, Pärnu, Riga, Rostock, Saint Petersburg, Stockholm, Tallinn, Turku
References [2]
1 Shore length is not a well-defined measure.

The Baltic Sea is a mediterranean sea of the Atlantic Ocean, enclosed by Denmark, Estonia, Finland, Latvia, Lithuania, Sweden, northeast Germany, Poland, Russia and the North and Central European Plain.


The sea stretches from 53°N to 66°N latitude and from 10°E to 30°E longitude. A marginal sea of the Atlantic, with limited water exchange between the two water bodies, the Baltic Sea drains through the Danish Straits into the Kattegat by way of the Øresund, Great Belt and Little Belt. It includes the Gulf of Bothnia, the Bay of Bothnia, the Gulf of Finland, the Gulf of Riga and the Bay of Gdańsk.

The Baltic Proper is bordered on its northern edge, at the latitude 60°N, by the Åland islands and the Gulf of Bothnia, on its northeastern edge by the Gulf of Finland, on its eastern edge by the Gulf of Riga, and in the west by the Swedish part of the southern Scandinavian Peninsula.

The Baltic Sea is connected by artificial waterways to the White Sea via the White Sea Canal and to the German Bight of the North Sea via the Kiel Canal.


Danish Straits and southwestern Baltic Sea Belte inter.png
Danish Straits and southwestern Baltic Sea


The Helsinki Convention on the Protection of the Marine Environment of the Baltic Sea Area includes the Baltic Sea and the Kattegat, without calling Kattegat a part of the Baltic Sea, "For the purposes of this Convention the 'Baltic Sea Area' shall be the Baltic Sea and the Entrance to the Baltic Sea, bounded by the parallel of the Skaw in the Skagerrak at 57°44.43'N." [3]

Traffic history

Historically, the Kingdom of Denmark collected Sound Dues from ships at the border between the ocean and the land-locked Baltic Sea, in tandem: in the Øresund at Kronborg castle near Helsingør; in the Great Belt at Nyborg; and in the Little Belt at its narrowest part then Fredericia, after that stronghold was built. The narrowest part of Little Belt is the "Middelfart Sund" near Middelfart. [4]


Geographers widely agree that the preferred physical border of the Baltic is a line drawn through the southern Danish islands, Drogden-Sill and Langeland. [5] The Drogden Sill is situated north of Køge Bugt and connects Dragør in the south of Copenhagen to Malmö; it is used by the Øresund Bridge, including the Drogden Tunnel. By this definition, the Danish Straits are part of the entrance, but the Bay of Mecklenburg and the Bay of Kiel are parts of the Baltic Sea. Another usual border is the line between Falsterbo, Sweden and Stevns Klint, Denmark, as this is the southern border of Øresund. It's also the border between the shallow southern Øresund (with a typical depth of 5–10 meters only) and notably deeper water.

Hydrography and biology

Drogden Sill (depth of 7 m (23 ft)) sets a limit to Øresund and Darss Sill (depth of 18 m (59 ft)), and a limit to the Belt Sea. [6] The shallow sills are obstacles to the flow of heavy salt water from the Kattegat into the basins around Bornholm and Gotland.

The Kattegat and the southwestern Baltic Sea are well oxygenated and have a rich biology. The remainder of the Sea is brackish, poor in oxygen and in species. Thus, statistically, the more of the entrance that is included in its definition, the healthier the Baltic appears; conversely, the more narrowly it is defined, the more endangered its biology appears.

Etymology and Nomenclature

Tacitus called it Mare Suebicum after the Germanic people of the Suebi, [7] and Ptolemy Sarmatian Ocean after the Sarmatians, [8] but the first to name it the Baltic Sea ( Mare Balticum ) was the eleventh-century German chronicler Adam of Bremen. The origin of the latter name is speculative and it was adopted into Slavic and Finnic languages spoken around the sea, very likely due to the role of Medieval Latin in cartography. 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 directly derived from the source of the Germanic word, Latin balteus "belt". [9] Adam of Bremen himself compared the sea with a belt, stating that it is so named 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 the name of a legendary island mentioned in the Natural History of 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 an island named Basilia ("the royal") in On the Ocean by Pytheas. Baltia also might be derived from belt and mean "near belt of sea, strait".

Meanwhile, others have suggested that the name of the island originates from the Proto-Indo-European root *bhel meaning "white, fair". [10] This root and its basic meaning were retained in Lithuanian (as baltas), Latvian (as balts) and Slavic (as bely). On this basis, a related hypothesis holds that the name originated from this Indo-European root via a Baltic language such as Lithuanian. [11] Another explanation is that, while derived from the aforementioned root, the name of the sea is related to names for various forms of water and related substances in several European languages, that might have been originally associated with colors found in swamps (compare Proto-Slavic *bolto "swamp"). Yet another explanation is that the name originally meant "enclosed sea, bay" as opposed to open sea. [12] Some Swedish historians believe the name derives from the god Baldr of Nordic mythology.

In the Middle Ages the sea was known by a variety of names. The name Baltic Sea became dominant only after 1600. Usage of Baltic and similar terms to denote the region east of the sea started only in 19th century.

Name in other languages

The Baltic Sea was known in ancient Latin language sources as Mare Suebicum or even Mare Germanicum. [13] Older native names in languages that used to be spoken on the shores of the sea or near it usually indicate the geographical location of the sea (in Germanic languages), or its size in relation to smaller gulfs (in Old Latvian), or tribes associated with it (in Old Russian the sea was known as the Varanghian Sea). In modern languages it is known by the equivalents of "East Sea", "West Sea", or "Baltic Sea" in different languages:


Classical world

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 where the ice broke apart and chunks floated about. The Suebi eventually migrated southwest to temporarily reside in the Rhineland area of modern Germany, where their name survives in the historic region known as Swabia. Jordanes called it the Germanic Sea in his work, the Getica .

Middle Ages

Cape Arkona on the island of Rugen in Germany, was a sacred site of the Slavs before Christianization. Putgarten, Kap Arkona (2011-05-21) 3.JPG
Cape Arkona on the island of Rügen in Germany, was a sacred site of the Slavs before Christianization.

In the early Middle Ages, Norse (Scandinavian) merchants built a trade empire all around the Baltic. Later, the Norse fought for control of the Baltic against Wendish tribes dwelling on the southern shore. The Norse also used the rivers of Russia for trade routes, finding their way eventually to the Black Sea and southern Russia. This Norse-dominated period is referred to as the Viking Age.

Since the Viking age, the Scandinavians have referred to the Baltic Sea as Austmarr ("Eastern Lake"). "Eastern Sea", appears in the Heimskringla and Eystra salt appears in Sörla þáttr . 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 within today's borders of Poland, Russia and Lithuania. First mentions of amber deposits on the South coast of the Baltic Sea date back to the 12th century. [14] The bordering countries have also traditionally exported lumber, wood tar, flax, hemp and furs by ship across the Baltic. Sweden had from early medieval times exported iron and silver mined there, while Poland had and still has extensive salt mines. Thus the Baltic Sea has long been crossed by much merchant shipping.

The lands on the Baltic's eastern shore were among the last in Europe to be converted to Christianity. This finally happened during the Northern Crusades: Finland in the twelfth century by Swedes, and what are now Estonia and Latvia in the early thirteenth century by Danes and Germans (Livonian Brothers of the Sword). The Teutonic Order gained control over parts of the southern and eastern shore of the Baltic Sea, where they set up their monastic state. Lithuania was the last European state to convert to Christianity.

An arena of conflict

Main trading routes of the Hanseatic League (Hanse). Haupthandelsroute Hanse.png
Main trading routes of the Hanseatic League (Hanse).
In 1649 the settlement of the Latvian-speaking Kursenieki spanned from Klaipeda to Gdansk along the coast of the Baltic Sea. Curonians kursenieki in 1649.png
In 1649 the settlement of the Latvian-speaking Kursenieki spanned from Klaipėda to Gdańsk along the coast of the Baltic Sea.

In the period between the 8th and 14th centuries, there was much piracy in the Baltic from the coasts of Pomerania and Prussia, and the Victual Brothers held Gotland.

Starting in the 11th century, the southern and eastern shores of the Baltic were settled by migrants mainly from Germany, a movement called the Ostsiedlung ("east settling"). Other settlers were from the Netherlands, Denmark, and Scotland. The Polabian Slavs were gradually assimilated by the Germans. [15] 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.

The naval Battle of the Sound took place on 8 November 1658 during the Dano-Swedish War. Eerste fase van de Zeeslag in de Sont - First phase of the Battle of the Sound - November 8 1658 (Jan Abrahamsz Beerstraten, 1660).jpg
The naval Battle of the Sound took place on 8 November 1658 during the Dano-Swedish War.
The burning Cap Arcona shortly after the attacks, 3 May 1945. Only 350 survived of the 4,500 prisoners who had been aboard Cap Arcona burning.jpg
The burning Cap Arcona shortly after the attacks, 3 May 1945. Only 350 survived of the 4,500 prisoners who had been aboard

In the 13th to 16th centuries, the strongest economic force in Northern Europe was the Hanseatic League, a federation of merchant cities around the Baltic Sea and the North Sea. In the sixteenth and early seventeenth centuries, Poland, Denmark, and Sweden fought wars for Dominium maris baltici ("Lordship over the Baltic Sea"). Eventually, it was Sweden that virtually encompassed the Baltic Sea. In Sweden the sea was then referred to as Mare Nostrum Balticum ("Our Baltic Sea"). The goal of Swedish warfare during the 17th century was to make the Baltic Sea an all-Swedish sea (Ett Svenskt innanhav), something that was accomplished except the part between Riga in Latvia and Stettin in Pomerania. However, the Dutch dominated Baltic trade in the seventeenth century.

In the eighteenth century, Russia and Prussia became the leading powers over the sea. Sweden's defeat in the Great Northern War brought Russia to the eastern coast. Russia became and remained 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 in the Baltic. They bombarded Sveaborg, which guards Helsinki; and Kronstadt, which guards Saint Petersburg; and they destroyed Bomarsund in the Åland Islands. After the unification of Germany in 1871, the whole southern coast became German. World War I 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 World War II, Germany reclaimed all of the southern and much of the eastern shore 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 Wilhelm Gustloff remains the worst maritime disaster in history, 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 World War II, on the bottom of the sea.

Since World War II

Since the end of World War II, various nations, including the Soviet Union, the United Kingdom and the United States have disposed of chemical weapons in the Baltic Sea, raising concerns of environmental contamination. [16] Today, fishermen occasionally find some of these materials: the most recent available report from the Helsinki Commission notes that four small scale catches of chemical munitions representing approximately 105 kg (231 lb) of material were reported in 2005. This is a reduction from the 25 incidents representing 1,110 kg (2,450 lb) of material in 2003. [17] Until now, the U.S. Government refuses to disclose the exact coordinates of the wreck sites. Deteriorating bottles leak mustard gas and other substances, thus slowly poisoning a substantial part of the Baltic Sea.

After 1945, the German population was expelled from all areas east of the Oder-Neisse line, making room for displaced Poles and Russians. Poland gained most of the southern shore. The Soviet Union gained another access to the Baltic with the Kaliningrad Oblast. The Baltic states on the eastern shore were annexed by the Soviet Union. The Baltic then separated opposing military blocs: NATO and the Warsaw Pact. Had war broken out, the Polish navy was prepared to invade the Danish isles. Neutral Sweden developed incident weapons to defend its territorial waters after the Swedish submarine incidents. [18] This border status restricted trade and travel. It ended only after the collapse of the Communist regimes in Central and Eastern Europe in the late 1980s.

Since May 2004, with the accession of the Baltic states and Poland, the Baltic Sea has been almost entirely surrounded by countries of the European Union (EU). The remaining non-EU shore areas are Russian: the Saint Petersburg area and the Kaliningrad Oblast exclave.

Winter storms begin arriving in the region during October. These have caused numerous shipwrecks, and contributed to the extreme difficulties of rescuing passengers of the ferry M/S Estonia en route from Tallinn, Estonia, to Stockholm, Sweden, in September 1994, which claimed the lives of 852 people. 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.

Storm floods

Storm surge floodings are generally taken to occur when the water level is more than one metre above normal. In Warnemünde about 110 floods occurred from 1950 to 2000, an average of just over two per year. [19]

Historic flood events were the All Saints' Flood of 1304 and other floods in the years 1320, 1449, 1625, 1694, 1784 and 1825. Little is known of their extent. [20] From 1872, there exist regular and reliable records of water levels in the Baltic Sea. The highest was the flood of 1872 when the water was an average of 2.43 m (8 ft 0 in) above sea level at Warnemünde and a maximum of 2.83 m (9 ft 3 in) above sea level in Warnemünde. In the last very heavy floods the average water levels reached 1.88 m (6 ft 2 in) above sea level in 1904, 1.89 m (6 ft 2 in) in 1913, 1.73 m (5 ft 8 in) in January 1954, 1.68 m (5 ft 6 in) on 2–4 November 1995 and 1.65 m (5 ft 5 in) on 21 February 2002. [21]


Geophysical data

Baltic drainage basins (catchment area), with depth, elevation, major rivers and lakes Baltic drainage basins (catchment area).svg
Baltic drainage basins (catchment area), with depth, elevation, major rivers and lakes
Curonian Spit in Kaliningrad Oblast, Russia Curonian Spit NP 05-2017 img17 aerial view at Epha Dune.jpg
Curonian Spit in Kaliningrad Oblast, Russia

An arm of the North Atlantic Ocean, the Baltic Sea is enclosed by Sweden and Denmark to the west, Finland to the northeast, the Baltic countries to the southeast, and the North European Plain to the southwest.

It is about 1,600 km (990 mi) long, an average of 193 km (120 mi) wide, and an average of 55 metres (180 ft) deep. The maximum depth is 459 m (1,506 ft) which is on the Swedish side of the center. The surface area is about 349,644 km2 (134,998 sq mi) [22] and the volume is about 20,000 km3 (4,800 cu mi). The periphery amounts to about 8,000 km (5,000 mi) of coastline. [23]

The Baltic Sea is one of the largest brackish inland seas by area, and occupies a basin (a zungenbecken ) formed by glacial erosion during the last few ice ages.

Physical characteristics of the Baltic Sea, its main sub-regions, and the transition zone to the Skagerrak/North Sea area [24]

Sub-areaAreaVolumeMaximum depthAverage depth
1. Baltic proper211,06913,04545962.1
2. Gulf of Bothnia115,5166,38923060.2
3. Gulf of Finland29,6001,10012338.0
4. Gulf of Riga16,300424> 6026.0
5. Belt Sea/Kattegat42,40880210918.9
Total Baltic Sea415,26621,72145952.3


The International Hydrographic Organization defines the limits of the Baltic Sea as follows: [25]

Bordered by the coasts of Germany, Denmark, Poland, Sweden, Finland, Russia, Estonia, Latvia and Lithuania, it extends north-eastward of the following limits:


Regions and basins of the Baltic Sea:
1 = Bothnian Bay
2 = Bothnian Sea
1 + 2 = Gulf of Bothnia, partly also 3 & 4
3 = Archipelago Sea
4 = Aland Sea
5 = Gulf of Finland
6 = Northern Baltic Proper
7 = Western Gotland Basin
8 = Eastern Gotland Basin
9 = Gulf of Riga
10 = Bay of Gdansk/Gdansk Basin
11 = Bornholm Basin and Hano Bight
12 = Arkona Basin
6-12 = Baltic Proper
13 = Kattegat, not an integral part of the Baltic Sea
14 = Belt Sea (Little Belt and Great Belt)
15 = Oresund (The Sound)
14 + 15 = Danish Straits, not an integral part of the Baltic Sea Baltic marine subdivisions and drainage basins.gif
Regions and basins of the Baltic Sea:
1 = Bothnian Bay
2 = Bothnian Sea
1 + 2 = Gulf of Bothnia, partly also 3 & 4
3 = Archipelago Sea
4 = Åland Sea
5 = Gulf of Finland
6 = Northern Baltic Proper
7 = Western Gotland Basin
8 = Eastern Gotland Basin
9 = Gulf of Riga
10 = Bay of Gdańsk/Gdansk Basin
11 = Bornholm Basin and Hanö Bight
12 = Arkona Basin
6–12 = Baltic Proper
13 = Kattegat, not an integral part of the Baltic Sea
14 = Belt Sea (Little Belt and Great Belt)
15 = Öresund (The Sound)
14 + 15 = Danish Straits, not an integral part of the Baltic Sea

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 the Sambia Peninsula 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 (Öresund/Øresund), connect the Baltic Sea with the Kattegat and Skagerrak strait in the North Sea.

Temperature and ice

Satellite image of the Baltic Sea in a mild winter BalticSea March2000 NASA-S2000084115409.png
Satellite image of the Baltic Sea in a mild winter
Traversing Baltic Sea and ice Baltic Sea 1551 (5496745361).jpg
Traversing Baltic Sea and ice

The water temperature of the Baltic Sea varies significantly depending on exact location, season and depth. At the Bornholm Basin, which is located directly east of the island of the same name, the surface temperature typically falls to 0–5 °C (32–41 °F) during the peak of the winter and rises to 15–20 °C (59–68 °F) during the peak of the summer, with an annual average of around 9–10 °C (48–50 °F). [27] A similar pattern can be seen in the Gotland Basin, which is located between the island of Gotland and Latvia. In the deep of these basins the temperature variations are smaller. At the bottom of the Bornholm Basin, deeper than 80 m (260 ft), the temperature typically is 1–10 °C (34–50 °F), and at the bottom of the Gotland Basin, at depths greater than 225 m (738 ft), the temperature typically is 4–7 °C (39–45 °F). [27]

On the long-term average, the Baltic Sea is ice-covered at the annual maximum for about 45% of its surface area. The ice-covered area during such a typical winter includes the Gulf of Bothnia, the Gulf of Finland, the Gulf of Riga, the archipelago west of Estonia, the Stockholm archipelago, and the Archipelago Sea southwest of Finland. The remainder of the Baltic does not freeze during a normal winter, except 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 extremities of the Gulf of Bothnia typically in the middle of November, reaching the open waters of the Bothnian Bay in early January. The Bothnian Sea, the basin south of Kvarken, freezes on average in late February. The Gulf of Finland and the Gulf of Riga freeze typically in late January. In 2011, the Gulf of Finland was completely frozen on 15 February. [28]

The ice extent depends on whether the winter is mild, moderate, or severe. In severe winters ice can form around southern Sweden and even in the Danish straits. According to the 18th-century natural historian William Derham, during the severe winters of 1703 and 1708, the ice cover reached as far as the Danish straits. [29] Frequently, parts of the Gulf of Bothnia and Gulf of Finland are frozen, in addition to coastal fringes in more southerly locations such as the Gulf of Riga. This description meant that the whole of the Baltic Sea was covered with ice.

Since 1720, the Baltic Sea has frozen over entirely 20 times, most recently in early 1987, which was the most severe winter in Scandinavia since 1720. The ice then covered 400,000 km2 (150,000 sq mi). During the winter of 2010–11, which was quite severe compared to those of the last decades, the maximum ice cover was 315,000 km2 (122,000 sq mi), which was reached on 25 February 2011. The ice then extended from the north down to the northern tip of Gotland, with small ice-free areas on either side, and the east coast of the Baltic Sea was covered by an ice sheet about 25 to 100 km (16 to 62 mi) wide all the way to Gdańsk. This was brought about by a stagnant high-pressure area that lingered over central and northern Scandinavia from around 10 to 24 February. After this, strong southern winds pushed the ice further into the north, and much of the waters north of Gotland were again free of ice, which had then packed against the shores of southern Finland. [30] The effects of the afore-mentioned high-pressure area did not reach the southern parts of the Baltic Sea, and thus the entire sea did not freeze over. However, floating ice was additionally observed near Świnoujście harbour in January 2010.

In recent years before 2011, the Bothnian Bay and the Bothnian Sea were frozen with solid ice near the Baltic coast and dense floating ice far from it. In 2008, almost no ice formed except for a short period in March. [31]

Piles of drift ice on the shore of Puhtulaid, near Virtsu, Estonia, in late April Jaamaed Puhtulaiul 1.JPG
Piles of drift ice on the shore of Puhtulaid, near Virtsu, Estonia, in late April

During winter, fast ice, which is attached to the shoreline, develops first, rendering ports unusable without the services of icebreakers. Level ice, ice sludge, pancake ice, and 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 (49 ft). Offshore of the landfast ice, the ice remains very dynamic all year, and it is relatively easily moved around by winds and therefore forms pack ice, made up of large piles and ridges pushed against the landfast ice and shores.

In spring, the Gulf of Finland and the Gulf of Bothnia normally thaw in late April, with some ice ridges persisting until May in the eastern extremities of the 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. However, in the famine year of 1867 remnants of ice were observed as late as July 17 near Uddskär. [32] Even as far south as Øresund, remnants of ice have been observed in May on several occasions; near Taarbaek on May 15, 1942 and near Copenhagen on May 11, 1771. Drift ice was also observed on May 11, 1799. [33] [34] [35]

The ice cover is the main habitat for two large mammals, the grey seal (Halichoerus grypus) and the Baltic ringed seal (Pusa hispida botnica), both of which feed underneath the ice and breed on its surface. Of these two seals, only the Baltic ringed seal suffers when there is not adequate ice in the Baltic Sea, as it feeds its young only while on ice. The grey seal is adapted to reproducing also with no ice in the sea. The sea ice also harbours several species of algae that live in the bottom and inside unfrozen brine pockets in the ice.


Depths of the Baltic Sea in metres Ostseetiefen.png
Depths of the Baltic Sea in metres

The Baltic Sea flows out through the Danish straits; however, the flow is complex. A surface layer of brackish water discharges 940 km3 (230 cu mi) per year into the North Sea. Due to the difference in salinity, by salinity permeation principle, a sub-surface layer of more saline water moving in the opposite direction brings in 475 km3 (114 cu mi) 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 (130 to 230 ft) deep. The general circulation is anti-clockwise: northwards along its eastern boundary, and south along the western one . [36]

The difference between the outflow and the inflow comes entirely from fresh water. More than 250 streams drain a basin of about 1,600,000 km2 (620,000 sq mi), contributing a volume of 660 km3 (160 cu mi) 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, are important to the Baltic ecosystem because of the oxygen they transport into the Baltic deeps, used to happen regularly until the 1980s. In recent decades they have become less frequent. The latest four occurred in 1983, 1993, 2003 and 2014 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. Quite violent, sudden storms sweep the surface ten or more times a year, 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 (1 ft 8 in) . [36]


Baltic Sea near Klaipeda (Karkle). Sunny day on the coast on Baltic sea.jpg
Baltic Sea near Klaipėda (Karklė).

The Baltic Sea is the world's largest inland brackish sea. [37] Only two other brackish waters are larger on some measurements: The Black Sea is larger in both surface area and water volume, but most of it is located outside the continental shelf (only a small percentage is inland). The Caspian Sea is larger in water volume, but—despite its name—it is a lake rather than a sea. [37]

The Baltic Sea's salinity is much lower than that of ocean water (which averages 3.5%), as a result of abundant freshwater runoff from the surrounding land (rivers, streams and alike), combined with the shallowness of the sea itself; runoff contributes roughly one-fortieth its total volume per year, as the volume of the basin is about 21,000 km3 (5,000 cu mi) and yearly runoff is about 500 km3 (120 cu mi).[ citation needed ]

The open surface waters of the Baltic Sea "proper" generally have a salinity of 0.3 to 0.9%, which is border-line freshwater. The flow of fresh water into the sea from approximately two hundred rivers and the introduction of salt from the southwest builds up a gradient of salinity in the Baltic Sea. The highest surface salinities, generally 0.7–0.9%, is in the southwestern-most part of the Baltic, in the Arkona and Bornholm basins (the former located roughly between southeast Zealand and Bornholm, and the latter directly east of Bornholm). It gradually falls further east and north, reaching the lowest in the Bothnian Bay at around 0.3%. [38] Drinking the surface water of the Baltic as a means of survival would actually hydrate the body instead of dehydrating, as is the case with ocean water. [note 1] [ citation needed ]

As salt water is denser than fresh water, the bottom of the Baltic Sea is saltier than the surface. This creates a vertical stratification of the water column, a halocline, that represents a barrier to the exchange of oxygen and nutrients, and fosters completely separate maritime environments. [39] The difference between the bottom and surface salinities vary depending on location. Overall it follows the same southwest to east and north pattern as the surface. At the bottom of the Arkona Basin (equalling depths greater than 40 m or 130 ft) and Bornholm Basin (depths greater than 80 m or 260 ft) it is typically 1.4–1.8%. Further east and north the salinity at the bottom is consistently lower, being the lowest in Bothnian Bay (depths greater than 120 m or 390 ft) where it is slightly below 0.4%, or only marginally higher than the surface in the same region. [38]

In contrast, the salinity of the Danish straits, which connect the Baltic Sea and Kattegat, tends to be significantly higher, but with major variations from year to year. For example, the surface and bottom salinity in the Great Belt is typically around 2.0% and 2.8% respectively, which is only somewhat below that of the Kattegat. [38] The water surplus caused by the continuous inflow of rivers and streams to the Baltic Sea means that there generally is a flow of brackish water out though the Danish straits to the Kattegat (and eventually the Atlantic). [40] Significant flows in the opposite direction, salt water from the Kattegat through the Danish straits to the Baltic Sea, are less regular. From 1880 to 1980 inflows occurred on average six to seven times per decade. Since 1980 it has been much less frequent, although a very large inflow occurred in 2014. [27]

Major tributaries

The rating of mean discharges differs from the ranking of hydrological lengths (from the most distant source to the sea) and the rating of the nominal lengths. Göta älv, a tributary of the Kattegat, is not listed, as due to the northward upper low-salinity-flow in the sea, its water hardly reaches the Baltic proper:

Length (km)Basin (km2)States sharing the basinLongest watercourse
Neva 250074 (nominal)
860 (hydrological)
281,000 Russia, Finland (Ladoga-affluent Vuoksi) Suna (280 km) → Lake Onega (160 km) →
Svir (224 km) → Lake Ladoga (122 km) → Neva
Vistula 10801047194,424 Poland, tributaries: Belarus, Ukraine, Slovakia
Daugava 678102087,900 Russia (source), Belarus, Latvia
Neman 67893798,200 Belarus (source), Lithuania, Russia
Kemijoki 556550 (main river)
600 (river system)
51,127 Finland, Norway (source of Ounasjoki)longer tributary Kitinen
Oder 540866118,861 Czech Republic (source), Poland, Germany
Lule älv 50646125,240 Sweden
Narva 41577 (nominal)
652 (hydrological)
56,200 Russia (Source of Velikaya), Estonia Velikaya (430 km) → Lake Peipus (145 km) → Narva
Torne älv 388520 (nominal)
630 (hydrological)
40,131 Norway (source), Sweden, Finland Válfojohka → Kamajåkka → Abiskojaure → Abiskojokk
(total 40 km) → Torneträsk (70 km) → Torne älv

Islands and archipelagoes

Skerries form an integral and typical part of many of the archipelagos of the Baltic Sea, such as these in the archipelago of the Aland Islands, Finland. Archipelago062009.jpg
Skerries form an integral and typical part of many of the archipelagos of the Baltic Sea, such as these in the archipelago of the Åland Islands, Finland.
Stockholm archipelago Korso Krokso Sandon February 2013.jpg
Stockholm archipelago
Aerial view of Bornholm, Denmark Bornholm luftaufnahme.jpg
Aerial view of Bornholm, Denmark

Coastal countries

Vast coastal dunes are characteristic for large parts of the southern shore of the Baltic Sea. Kursiu Nerija National Park in Lithuania (pictured) is a part of the Curonian Spit World Heritage Site. Image-Lithuania Juodkrante sand dunes.jpg
Vast coastal dunes are characteristic for large parts of the southern shore of the Baltic Sea. Kuršių Nerija National Park in Lithuania (pictured) is a part of the Curonian Spit World Heritage Site.
Population density in the Baltic Sea catchment area Population density in the Baltic Sea catchment area.svg
Population density in the Baltic Sea catchment area

Countries that border the sea:

Flag of Denmark.svg  Denmark, Flag of Estonia.svg  Estonia, Flag of Finland.svg  Finland, Flag of Germany.svg  Germany, Flag of Latvia.svg  Latvia, Flag of Lithuania.svg  Lithuania, Flag of Poland.svg  Poland, Flag of Russia.svg  Russia, Flag of Sweden.svg  Sweden.

Countries lands in the outer drainage basin:

Flag of Belarus.svg  Belarus, Flag of the Czech Republic.svg  Czech Republic, Flag of Norway.svg  Norway, Flag of Slovakia.svg  Slovakia, Flag of Ukraine.svg  Ukraine.

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 less than 6% each. [41]

Tallinn in Estonia Tallin. - panoramio.jpg
Tallinn in Estonia
Helsinki in Finland Paasitorni by the sea.jpg
Helsinki in Finland
Stockholm in Sweden Stockholm 8721-B (9870833193).jpg
Stockholm in Sweden
Vasilyevsky Island in Saint Petersburg, Russia Spb 06-2017 img01 Spit of Vasilievsky Island.jpg
Vasilyevsky Island in Saint Petersburg, Russia


The biggest coastal cities (by population):

Other important ports:


Baltic History 7500-BC.svg
Ancylus Lake around 8700 years BP. The relic of Scandinavian Glacier in white. The rivers Svea älv (Svea river) and Göta älv formed an outlet to the Atlantic.
Suomi jaakauden jalkeen.png
Much of modern Finland is former seabed or archipelago: illustrated are sea levels immediately after the last ice age.

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 great river that paleontologists call the Eridanos. Several Pleistocene glacial episodes 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.

The land is still emerging isostatically from its depressed state, which was caused by the weight of ice during 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 sloping, leading to large areas of land being reclaimed in what are, geologically speaking, relatively short periods (decades and centuries).

The "Baltic Sea anomaly"

The "Baltic Sea anomaly" refers to interpretations of an indistinct sonar image taken by Swedish salvage divers on the floor of the northern Baltic Sea in June 2011. The treasure hunters suggested the image showed an object with unusual features of seemingly extraordinary origin. Speculation published in tabloid newspapers claimed that the object was a sunken UFO. A consensus of experts and scientists say that the image most likely shows a natural geological formation. [43] [44] [45] [46] [47]


Fauna and flora

The fauna of the Baltic Sea is a mixture of marine and freshwater species. Among marine fishes are Atlantic cod, Atlantic herring, European hake, European plaice, European flounder, shorthorn sculpin and turbot, and examples of freshwater species include European perch, northern pike, whitefish and common roach. Freshwater species may occur at outflows of rivers or streams in all coastal sections of the Baltic Sea. Otherwise marine species dominate in most sections of the Baltic, at least as far north as Gävle, where less than one-tenth are freshwater species. Further north the pattern is inverted. In the Bothnian Bay, roughly two-thirds of the species are freshwater. In the far north of this bay, saltwater species are almost entirely absent. [27] For example, the common starfish and shore crab, two species that are very widespread along European coasts, are both unable to cope with the significantly lower salinity. Their range limit is west of Bornholm, meaning that they are absent from the vast majority of the Baltic Sea. [27] Some marine species, like the Atlantic cod and European flounder, can survive at relatively low salinities, but need higher salinities to breed, which therefore occurs in deeper parts of the Baltic Sea. [48] [49]

There is a decrease in species richness from the Danish belts to the Gulf of Bothnia. The decreasing salinity along this path causes restrictions in both physiology and habitats. [50] At more than 600 species of invertebrates, fish, aquatic mammals, aquatic birds and macrophytes, the Arkona Basin (roughly between southeast Zealand and Bornholm) is far richer than other more eastern and northern basins in the Baltic Sea, which all have less than 400 species from these groups, with the exception of the Gulf of Finland with more than 750 species. However, even the most diverse sections of the Baltic Sea have far less species than the almost-full saltwater Kattegat, which is home to more than 1600 species from these groups. [27] The lack of tides has affected the marine species as compared with the Atlantic.

Since the Baltic Sea is so young there are only two or three known endemic species: the brown alga Fucus radicans and the flounder Platichthys solemdali . Both appear to have evolved in the Baltic basin and were only recognized as species in 2005 and 2018 respectively, having formerly been confused with more widespread relatives. [49] [51] The tiny Copenhagen cockle (Parvicardium hauniense), a rare mussel, is sometimes considered endemic, but has now been recorded in the Mediterranean. [52] However, some consider non-Baltic records to be misidentifications of juvenile lagoon cockles (Cerastoderma glaucum). [53] Several widespread marine species have distinctive subpopulations in the Baltic Sea adapted to the low salinity, such as the Baltic Sea forms of the Atlantic herring and lumpsucker, which are smaller than the widespread forms in the North Atlantic. [40]

A peculiar feature of the fauna is that it contains a number of glacial relict species, isolated populations of arctic species which have remained in the Baltic Sea since the last glaciation, such as the large isopod Saduria entomon , the Baltic subspecies of ringed seal, and the fourhorn sculpin. Some of these relicts are derived from glacial lakes, such as Monoporeia affinis , which is a main element in the benthic fauna of the low-salinity Bothnian Bay.

Cetaceans in Baltic Sea have been monitored by the ASCOBANS. Critically endangered populations of Atlantic white-sided dolphins and harbor porpoises inhabit the sea where white-colored porpoises have been recorded, [54] and occasionally oceanic and out-of-range species such as minke whales, [55] bottlenose dolphins, [56] beluga whales, [57] orcas, [58] and beaked whales [59] visit the waters. In recent years, very small, but with increasing rates, fin whales [60] [61] [62] [63] and humpback whales migrate into Baltic sea including mother and calf pair. [64] Now extinct Atlantic grey whales (remains found from Gräsö along Bothnian Sea/southern Bothnian Gulf [65] and Ystad [66] ) and eastern population of North Atlantic right whales that is facing functional extinction [67] once migrated into Baltic Sea. [68]

Other notable megafauna include the basking sharks. [69]

Environmental status

Phytoplankton algal bloom in the Baltic Proper, July 2001 Phytoplankton bloom in the Baltic Sea (July 3, 2001).jpg
Phytoplankton algal bloom in the Baltic Proper, July 2001

Satellite images taken in July 2010 revealed a massive algal bloom covering 377,000 square kilometres (146,000 sq mi) in the Baltic Sea. The area of the bloom extended from Germany and Poland to Finland. Researchers of the phenomenon have indicated that algal blooms have occurred every summer for decades. Fertilizer runoff from surrounding agricultural land has exacerbated the problem and led to increased eutrophication. [70]

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.

Plans to artificially oxygenate areas of the Baltic that have experienced eutrophication have been proposed by the University of Gothenburg and Inocean AB. The proposal intends to use wind-driven pumps to inject oxygen (air) into waters at, or around, 130m below sea level. [71]

After World War II, Germany had to be disarmed and large quantities of ammunition stockpiles were disposed directly into the Baltic Sea and the North Sea. Environmental experts and marine biologists warn that these ammunition dumps pose a major environmental threat with potentially life-threatening consequences to the health and safety of humans on the coastlines of these seas. [72]


Pedestrian pier at Palanga, the most popular sea resort in Lithuania Palangos tiltas1.jpg
Pedestrian pier at Palanga, the most popular sea resort in Lithuania

Construction of the Great Belt Bridge in Denmark (completed 1997) and the Øresund Bridge-Tunnel (completed 1999), linking Denmark with Sweden, provided a highway and railroad connection between Sweden and the Danish mainland (the Jutland Peninsula, precisely the Zealand). The undersea tunnel of the Øresund 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 and Malmö, Sweden; Rauma, Turku, and Helsinki, Finland; Riga, Ventspils, and Liepāja, Latvia; Klaipėda, Lithuania; and Saint Petersburg, Russia.

There are several cargo and passenger ferries that operate on the Baltic Sea, such as Scandlines, Silja Line, Polferries, the Viking Line, Tallink, and Superfast Ferries.


Svetlogorsk resort town in Kaliningrad Oblast, Russia Pliazh v Svetlogorske - panoramio.jpg
Svetlogorsk resort town in Kaliningrad Oblast, Russia
Mrzezyno beach in Poland Mrzezyno east beach 2010-07 A.jpg
Mrzeżyno beach in Poland

The Helsinki Convention

1974 Convention

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.

1992 Convention

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, [73] 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.

See also

Related Research Articles

Gulf of Finland arm of the Baltic Sea

The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn. The eastern parts of the Gulf of Finland belong to Russia, and some of Russia's most important oil harbours are located farthest in, near Saint Petersburg. As the seaway to Saint Petersburg, the Gulf of Finland has been and continues to be of considerable strategic importance to Russia. Some of the environmental problems affecting the Baltic Sea are at their most pronounced in the shallow gulf.

Kattegat Sea area between Denmark and Sweden

The Kattegat is a 30,000 km2 (12,000 sq mi) sea area bounded by the Jutlandic peninsula in the west, the Danish Straits islands of Denmark to the south and the provinces of Västergötland, Scania, Halland and Bohuslän in Sweden in the east. The Baltic Sea drains into the Kattegat through the Danish Straits. The sea area is a continuation of the Skagerrak and may be seen as a bay of the Baltic Sea or the North Sea or, as in traditional Scandinavian usage, neither of these.

Scandinavian Peninsula peninsula in Northern Europe, which covers Norway, Sweden and most of northern Finland

The Scandinavian Peninsula is a peninsula of Eurasia located in Northern Europe, which roughly comprises the mainland of Sweden, the mainland of Norway, and the northwestern area of Finland.

Øresund The strait between Denmark and Sweden

Øresund or Öresund, commonly known in English as the Sound, is a strait which forms the Danish–Swedish border, separating Zealand (Denmark) from Scania (Sweden). The strait has a length of 118 kilometres (73 mi) and the width varies from 4 kilometres (2.5 mi) to 28 kilometres (17 mi). It is 4 kilometres (2.5 mi) wide at its narrowest point between Helsingør in Denmark and Helsingborg in Sweden.

Gulf of Bothnia the northernmost arm of the Baltic Sea

The Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.

Great Belt Strait in Denmark linking the Baltic Sea to the Kattegat strait and the Atlantic Ocean

The Great Belt is a strait between the major islands of Zealand (Sjælland) and Funen (Fyn) in Denmark. It is one of the three Danish Straits.

Baltic region Geographic region in Northern Europe

The terms Baltic region, Baltic Rim countries, and the Baltic Sea countries refer to slightly different combinations of countries in the general area surrounding the Baltic Sea in Northern Europe.

Gulf of Riga A bay of the Baltic Sea between Latvia and Estonia

The Gulf of Riga, Bay of Riga, or Gulf of Livonia is a bay of the Baltic Sea between Latvia and Estonia.

Archipelago Sea A part of the Baltic Sea between the Gulf of Bothnia, the Gulf of Finland and the Sea of Åland, within Finnish territorial waters

The Archipelago Sea is a part of the Baltic Sea between the Gulf of Bothnia, the Gulf of Finland and the Sea of Åland, within Finnish territorial waters. By some definitions it contains the largest archipelago in the world by the number of islands, although many of the islands are very small and tightly clustered.

Bothnian Sea Southern part of the Gulf of Bothnia

The Bothnian Sea links the Bothnian Bay with the Baltic proper. Kvarken is situated between the two. Together, the Bothnian Sea and Bay make up a larger geographical entity, the Gulf of Bothnia, where the Bothnian Sea is the southern part. The whole Gulf of Bothnia is situated between Sweden, to the West, Finland, to the East, and the Sea of Åland and Archipelago Sea to the South. The surface area of Bothnian Sea is approximately 79,000 km². The largest coastal towns, from south to north, are Rauma and Pori in Finland, and Gävle and Sundsvall in Sweden. Umeå (Sweden) and Vaasa (Finland) lie in the extreme north, near Bothnian Bay.

Baltic Ice Lake Prehistoric freshwater lake in the Baltic Sea basin formed from receding glaciers

The Baltic Ice Lake is a name given by geologists to a freshwater lake that gradually formed in the Baltic Sea basin as glaciation retreated from that region at the end of the Pleistocene. The lake, dated to 12,600-10,300 BP, is roughly contemporaneous with the three Pleistocene Blytt-Sernander periods. The lake followed a period of massive glaciation in the region, which followed the end of the Eemian Sea. The post-glacial Yoldia Sea was immediately subsequent to the Baltic Ice Lake.

Yoldia Sea is a name given by geologists to a variable brackish-water stage in the Baltic Sea basin that prevailed after the Baltic ice lake was drained to sea level during the Weichsel glaciation. Dates for the Yoldia sea are obtained mainly by radiocarbon dating material from ancient sediments and shore lines and from clay-varve chronology. They tend to vary by as much as a thousand years, but a good estimate is 10,300 – 9500 radiocarbon years BP, equivalent to ca 11,700-10,700 calendar years BP. The sea ended gradually when isostatic rise of Scandinavia closed or nearly closed its effluents, altering the balance between saline and fresh water. The Yoldia Sea became Ancylus Lake. The Yoldia Sea stage had three phases of which only the middle phase had brackish water.

Ancylus Lake is a name given by geologists to a large freshwater lake that existed in northern Europe approximately from 9500 to 8000 years B.P. being in effect one of various predecessors to the modern Baltic Sea.

Bothnian Bay northernmost part of the Gulf of Bothnia

The Bothnian Bay or Bay of Bothnia is the northernmost part of the Gulf of Bothnia, which is in turn the northern part of the Baltic Sea. The land holding the bay is still rising after the weight of ice-age glaciers has been removed, and within 2,000 years the bay will be a large freshwater lake. The bay today is fed by several large rivers, and is relatively unaffected by tides, so has low salinity. It freezes each year for up to six months. Compared to other parts of the Baltic it has little plant or animal life.

Amager Strandpark park in Copenhagen Municipality, Denmark

Amager Strandpark is a seaside public park in Copenhagen, Denmark. It is located on the island of Amager and includes an artificial island and offers a total of 4.6 km (2.9 mi) of beaches. From the beach, the Middelgrunden wind farm can be seen on the horizon.

Bothnia or Bothnian may refer to:

<i>Fucus radicans</i> species of chromista

Fucus radicans is a species of brown algae in the family Fucaceae, endemic to and recently evolved within the Baltic Sea. The species was first described by Lena Bergström and Lena Kautsky in 2005 from a location in Ångermanland, Sweden. The specific epithet is from the Latin and means "rooting", referring to the fact that this species primarily reproduces by the taking root of detached fragments.

Säppi Lighthouse Lighthouse in Finland

Säppi Lighthouse is a lighthouse on the coast of Bothnian Sea, located outside the city of Pori in the island of Säppi. The lighthouse stands approximately 14 kilometers Southwest of the Port of Pori on the area of Eurajoki municipality. It was designed by Finnish architect Axel Hampus Dalström and first lit in 1873.

The geology of the Baltic Sea is characterized by having areas located both at the Baltic Shield of the East European Craton and in the Danish-North German-Polish Caledonides. Historical geologists make a distinction between the current Baltic Sea depression, formed in the Cenozoic era, and the much older sedimentary basins whose sediments are preserved in the zone. Although glacial erosion has contributed to shape the present depression, the Baltic trough is largely a depression of tectonic origin that existed long before the Quaternary glaciation.



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Further reading