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Baltic Sea region
Map of the Baltic Sea region
Coordinates58°N 20°E / 58°N 20°E / 58; 20 (slightly east of the north tip of Gotland Island)
Primary inflowsDaugava, Kemijoki, Neman (Nemunas), Neva, Oder, Vistula, Lule, Narva, Torne
Primary outflowsDanish straits
Catchment area1,641,650 km2 (633,840 sq mi)
Basin countriesCoastal: Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden
Non-coastal: Belarus, Czech Republic, 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 time25 years
Shore length18,000 km (5,000 mi)
IslandsAbruka, Aegna, Archipelago Sea Islands (Åland), 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
SettlementsCopenhagen, Gdańsk, Gdynia, Greifswald, Haapsalu, Helsinki, Jūrmala, Kaliningrad, Kiel, Klaipėda, Kuressaare, Kärdla, Lübeck, Luleå, Mariehamn, Oulu, Palanga, Paldiski, Pärnu, Riga, Rostock, Saint Petersburg, Liepāja, Stockholm, Tallinn, Turku, Ventspils
1 Shore length is not a well-defined measure.

The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North and Central European Plain.[3]

The sea stretches from 53°N to 66°N latitude and from 10°E to 30°E longitude. It is a shelf sea and marginal sea of the Atlantic with limited water exchange between the two, making it an inland sea. 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 (divided into the Bothnian Bay and the Bothnian Sea), the Gulf of Finland, the Gulf of Riga and the Bay of Gdańsk.

The "Baltic Proper" is bordered on its northern edge, at latitude 60°N, by Åland 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–Baltic Canal and to the German Bight of the North Sea via the Kiel Canal.


Hel Peninsula
Danish straits and southwestern Baltic Sea
Åland between Baltic Sea and the Gulf of Bothnia


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."[4]

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.[5]


Geographers widely agree that the preferred physical border between the Baltic and North Seas is the Langelandsbælt (the southern part of the Great Belt strait near Langeland) and the Drogden-Sill strait.[6] 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 is 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 is 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.[7] 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 the Suebic Sea, Latin: Mare Suebicum after the Germanic people of the Suebi,[8][9] and Ptolemy Sarmatian Ocean after the Sarmatians,[10] but the first to name it the Baltic Sea (Medieval Latin: 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".[11] 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 therein mean "near belt of sea, strait".

Others have suggested that the name of the island originates from the Proto-Indo-European root *bʰel meaning "white, fair",[12] which may echo the naming of seas after colours relating to the cardinal points (as per Black Sea and Red Sea).[13] This '*bʰel' root and 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.[14] 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.[15]

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 the 19th century.

Name in other languages

The Baltic Sea was known in ancient Latin language sources as Mare Suebicum or even Mare Germanicum.[16] 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 Rügen in Germany, was a sacred site of the Rani tribe 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.[21] 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).

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.[22] 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.
Nautical chart of the Baltic Sea in 1919.
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 the 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; the case is also known as the Åland War. They bombarded Sveaborg, which guards Helsinki; and Kronstadt, which guards Saint Petersburg; and they destroyed Bomarsund in Åland. 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 granted access to the Baltic Sea at the expense of Germany by the Polish Corridor and enlarged the port of Gdynia in rivalry with the port of the Free City of Danzig.

After the Nazis' rise to power, Germany reclaimed the Memelland and after the outbreak of the Eastern Front (World War II) occupied 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.[23] 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.[24] 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 new Polish and Russian settlement. Poland gained most of the southern shore. The Soviet Union gained another access to the Baltic with the Kaliningrad Oblast, that had been part of German-settled East Prussia. 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. Neutral Sweden developed incident weapons to defend its territorial waters after the Swedish submarine incidents.[25] 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. Finland and Sweden joined NATO in 2023 and 2024, respectively, making the Baltic Sea almost entirely surrounded by the alliance's members.[26][27] Such an arrangement has also existed for the European Union (EU) since May 2004 following the accession of the Baltic states and Poland. The remaining non-NATO and -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.

Finland and Sweden joining NATO in 2023 and 2024, respectively, led some to label the sea a ″NATO lake″, as all the countries surrounding the Baltic Sea except Russia had become members of NATO.[28][29][27][30]

Storm floods

Storm surge floods 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.[31]

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.[32] 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.[33]


Geophysical data

Baltic drainage basins (catchment area), with depth, elevation, major rivers and lakes
Curonian Lagoon, Spit and Klaipėda

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

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) [34] 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.[35]

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[36]
Sub-area Area Volume Maximum depth Average depth
km2 km3 m m
Baltic proper 211,069 13,045 459 62.1
Gulf of Bothnia 115,516 6,389 230 60.2
Gulf of Finland 29,600 1,100 123 38.0
Gulf of Riga 16,300 424 > 60 26.0
Belt Sea/Kattegat 42,408 802 109 18.9
Total Baltic Sea 415,266 21,721 459 52.3


The International Hydrographic Organization defines the limits of the Baltic Sea as follows:[37]

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:[38]
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/Uznam 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
Traversing Baltic Sea and ice
On particularly cold winters, the coastal parts of the Baltic Sea freeze into ice thick enough to walk or ski on.

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).[39] 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).[39] Generally, offshore locations, lower latitudes and islands maintain maritime climates, but adjacent to the water continental climates are common, especially on the Gulf of Finland. In the northern tributaries the climates transition from moderate continental to subarctic on the northernmost coastlines.

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.[40]

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.[41] Frequently, parts of the Gulf of Bothnia and the 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.[42] 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 harbor 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.[43]

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 17 July near Uddskär.[44] Even as far south as Øresund, remnants of ice have been observed in May on several occasions; near Taarbaek on 15 May 1942 and near Copenhagen on 11 May 1771. Drift ice was also observed on 11 May 1799.[45][46][47]

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 harbors several species of algae that live in the bottom and inside unfrozen brine pockets in the ice.

Due to the often fluctuating winter temperatures between above and below freezing, the saltwater ice of the Baltic Sea can be treacherous and hazardous to walk on, in particular in comparison to the more stable fresh water-ice sheets in the interior lakes.


Depths of the Baltic Sea in meters

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 saltwater 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 with the western one .[48]

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 is infrequent inflows (also known as major Baltic inflows or MBIs) of North Sea water into the Baltic. Such inflows, important to the Baltic ecosystem because of the oxygen they transport into the Baltic deeps, happen on average once per year, but large pulses that can replace the anoxic deep water in the Gotland Deep occur about once in ten years. Previously, it was believed that the frequency of MBIs had declined since 1980, but recent studies have challenged this view and no longer display a clear change in the frequency or intensity of saline inflows. Instead, a decadal variability in the intensities of MBIs is observed with a main period of approximately 30 years.[49][50]

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. Tides can reach 17 to 19 cm (6.7 to 7.5 in) in the Gulf of Finland.[51]

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 the wind. Seasonal winds also cause small changes in sea level, of the order of 0.5 m (1 ft 8 in) .[48] According to the media, during a storm in January 2017, an extreme wave above 14 m (46 ft) has been measured and significant wave height of around 8 m (26 ft) has been measured by the FMI. A numerical study has shown the presence of events with 8 to 10 m (26 to 33 ft) significant wave heights. Those extreme waves events can play an important role in the coastal zone on erosion and sea dynamics.[52]


Baltic Sea near Klaipėda (Karklė).

The Baltic Sea is the world's largest inland brackish sea.[53] Only two other brackish waters are larger according to 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 fraction is inland). The Caspian Sea is larger in water volume, but—despite its name—it is a lake rather than a sea.[53]

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).

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 freshwater 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%, are in the southwesternmost 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%.[54] 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]

As saltwater is denser than freshwater, 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.[55] The difference between the bottom and surface salinities varies 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.[54]

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.[54] 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 through the Danish straits to the Kattegat (and eventually the Atlantic).[56] Significant flows in the opposite direction, salt water from the Kattegat through the Danish straits to the Baltic Sea, are less regular and are known as major Baltic inflows (MBIs).

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:

Name Mean
Length (km) Basin (km2) States sharing the basin Longest watercourse
Neva 2500 74 (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 1080 1047 194,424 Poland, tributaries: Belarus, Ukraine, Slovakia Bug (774 km) → Narew (22 km) → Vistula (156 km) total 1204 km
Daugava 678 1020 87,900 Russia (source), Belarus, Latvia
Neman 678 937 98,200 Belarus (source), Lithuania, Russia
Kemijoki 556 550 (main river)
600 (river system)
51,127 Finland, Norway (source of Ounasjoki) longer tributary Kitinen
Oder 540 866 118,861 Czech Republic (source), Poland, Germany Warta (808 km) → Oder (180 km) total: 928 km
Lule älv 506 461 25,240 Sweden
Narva 415 77 (nominal)
652 (hydrological)
56,200 Russia (source of Velikaya), Estonia Velikaya (430 km) → Lake Peipus (145 km) → Narva
Torne älv 388 520 (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 Åland, Finland.
Stockholm archipelago
Aerial view of Bornholm, Denmark

Coastal countries

Population density in the Baltic Sea catchment area

Countries that border the sea: Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden.

Countries lands in the outer drainage basin: Belarus, Czech Republic, Norway, Slovakia, 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.[57]


Vasilyevsky Island in Saint Petersburg, Russia
Stockholm in Sweden
Riga in Latvia
Helsinki in Finland
Gdańsk in Poland
Tallinn in Estonia

The biggest coastal cities (by population):

Other important ports:


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.
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 millimeters 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" is a feature on 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.[59][60][61][62][63]


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.[39] 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.[39] 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.[64][65] The common blue mussel is the dominating animal species, and makes up more than 90% of the total animal biomass in the sea.[66]

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.[67] 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 fewer species than the almost-full saltwater Kattegat, which is home to more than 1600 species from these groups.[39] 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.[65][68] The tiny Copenhagen cockle (Parvicardium hauniense), a rare mussel, is sometimes considered endemic, but has now been recorded in the Mediterranean.[69] However, some consider non-Baltic records to be misidentifications of juvenile lagoon cockles (Cerastoderma glaucum).[70] 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.[56]

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 the Baltic Sea are monitored by the countries bordering the sea and data compiled by various intergovernmental bodies, such as ASCOBANS. A critically endangered population of harbor porpoise inhabit the Baltic proper, whereas the species is abundant in the outer Baltic (Western Baltic and Danish straits) and occasionally oceanic and out-of-range species such as minke whales,[71] bottlenose dolphins,[72] beluga whales,[73] orcas,[74] and beaked whales[75] visit the waters. In recent years, very small, but with increasing rates, fin whales[76][77][78][79] and humpback whales migrate into Baltic sea including mother and calf pair.[80] Now extinct Atlantic grey whales (remains found from Gräsö along Bothnian Sea/southern Bothnian Gulf[81] and Ystad[82]) and eastern population of North Atlantic right whales that is facing functional extinction[83] once migrated into Baltic Sea.[84]

Other notable megafauna include the basking sharks.[85]

Environmental status

Satellite photo of the Baltic Sea surrounding Gotland, Sweden, with algae bloom (phytoplankton) swirling in the water

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.[86]

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 neighboring 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.[87]

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.[88]


Pedestrian pier in Sellin, Germany

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 the 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.

Construction of the Fehmarn Belt Fixed Link between Denmark and Germany is due to finish in 2029. It will be a three-bore tunnel carrying four motorway lanes and two rail tracks.

Through the development of offshore wind power the Baltic Sea is expected to become a major source of energy for countries in the region. According to the Marienborg Declaration, signed in 2022, all EU Baltic Sea states have announced their intentions to have 19.6 gigawatts of offshore wind in operation by 2030.[89]


Nida resort town in Klaipėda county, Lithuania
Svetlogorsk resort town in Kaliningrad Oblast, Russia
Mrzeżyno beach in Poland


Resort towns

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,[90] 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.

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  1. ^ A healthy serum concentration of sodium is around 0.8–0.85%, and healthy kidneys can concentrate salt in urine to at least 1.4%.


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  • Alhonen, Pentti (1966). "Baltic Sea". In Fairbridge, Rhodes (ed.). The Encyclopedia of Oceanography. New York: Van Nostrand Reinhold Company. pp. 87–91.
  • Schmitt, Rüdiger (1989). "BLACK SEA". Black Sea – Encyclopaedia Iranica. Encyclopaedia Iranica, Vol. IV, Fasc. 3. pp. 310–313.

Further reading


  • Bogucka, Maria. "The Role of Baltic Trade in European Development from the XVIth to the XVIIIth Centuries". Journal of European Economic History 9 (1980): 5–20.
  • Davey, James. The Transformation of British Naval Strategy: Seapower and Supply in Northern Europe, 1808–1812 (Boydell, 2012).
  • Dickson, Henry Newton (1911). "Baltic Sea" . Encyclopædia Britannica. Vol. 3 (11th ed.). pp. 286–287.
  • Fedorowicz, Jan K. England's Baltic Trade in the Early Seventeenth Century: A Study in Anglo-Polish Commercial Diplomacy (Cambridge UP, 2008).
  • Frost, Robert I. The Northern Wars: War, State, and Society in Northeastern Europe, 1558–1721 (Longman, 2000).
  • Grainger, John D. The British Navy in the Baltic (Boydell, 2014).
  • Kent, Heinz S. K. War and Trade in Northern Seas: Anglo-Scandinavian Economic Relations in the Mid Eighteenth Century (Cambridge UP, 1973).
  • Koningsbrugge, Hans van. "In War and Peace: The Dutch and the Baltic in Early Modern Times". Tijdschrift voor Skandinavistiek 16 (1995): 189–200.
  • Lindblad, Jan Thomas. "Structural Change in the Dutch Trade in the Baltic in the Eighteenth Century". Scandinavian Economic History Review 33 (1985): 193–207.
  • Lisk, Jill. The Struggle for Supremacy in the Baltic, 1600–1725 (U of London Press, 1967).
  • Niktalab, Poopak (2024). Over the Alps: History of Children and Youth literature in Europe (Chapter 2 Baltic sails: the evolution of children's and youth literature in the Baltic countries) (in Persian) (1st ed.). Tehran, Iran: Faradid Publisher. pp. 85–124. ISBN 9786225740457.
  • Roberts, Michael. The Early Vasas: A History of Sweden, 1523–1611 (Cambridge UP, 1968).
  • Rystad, Göran, Klaus-R. Böhme, and Wilhelm M. Carlgren, eds. In Quest of Trade and Security: The Baltic in Power Politics, 1500–1990. Vol. 1, 1500–1890. Stockholm: Probus, 1994.
  • Salmon, Patrick, and Tony Barrow, eds. Britain and the Baltic: Studies in Commercial, Political and Cultural Relations (Sunderland University Press, 2003).
  • Stiles, Andrina. Sweden and the Baltic 1523–1721 (1992).
  • Thomson, Erik. "Beyond the Military State: Sweden's Great Power Period in Recent Historiography". History Compass 9 (2011): 269–283. doi:10.1111/j.1478-0542.2011.00761.x
  • Tielhof, Milja van. The "Mother of All Trades": The Baltic Grain Trade in Amsterdam from the Late 16th to Early 19th Century. Leiden, The Netherlands: Brill, 2002.
  • Warner, Richard. "British Merchants and Russian Men-of-War: The Rise of the Russian Baltic Fleet". In Peter the Great and the West: New Perspectives. Edited by Lindsey Hughes, 105–117. Basingstoke, UK: Palgrave Macmillan, 2001.

External links

13 Annotations

Third Reading

San Diego Sarah  •  Link

The Baltic countries are Sweden, Finland, Estonia, Latvia, Lithuania, Poland, Denmark, Germany, and Russia, and their ports were used by cities in the Hansiatic League which, by the 17th century, was almost irrelevant. Trade was thriving, but the merchants no longer needed a League.

The Hanseatic League ports mostly traded fish (herring and stock fish), lumber, hemp, flax, grain, honey, fur, tar, salt, iron, silver, amber, spices, wine, cloth, and leather. England particularly liked their masts.

London was considered an outlier Hansiatic port, but to trade with the Baltic in the 17th century meant dodging pirates and privateers. Therefore, the Navy provided armed escorts for fleets of merchantmen.

Lithuania’s union with Poland consisted of a loose alliance. In 1569, the union was refashioned by a joint parliament in Lublin into a Commonwealth of Two Peoples. While the state entity now had a common elected sovereign and a joint parliament, the legal and administrative structures of the two lands, as well as their armies, remained separate. This arrangement lasted 200 years.

The Polish-Lithuanian union brought a time of political glory, prosperity, and cultural development. Until the middle of the 17th century, the Commonwealth contained the threat from Moscow. During the Time of Troubles in Muscovy at the beginning of the 17th century, a Polish-Lithuanian force occupied Moscow. The Catholic Counter-Reformation that accompanied the union placed an indelible stamp on Lithuania. Vilnius emerged as a centre of Baroque culture. Its university, founded in 1579, is the oldest institution of higher learning in that part of the world.

The Confederation was unable to withstand the onslaughts of Tsar Ivan IV (the Terrible), who in 1558 claimed the region in order to gain a sea port. The region broke into 3 duchies — Courland, Livonia, and Estland — which lasted until 1917.

Estland, the northern part of modern Estonia, came under Swedish rule. Livonia, with its capital, Riga, became a part of Lithuania, while Courland became a hereditary duchy nominally under Lithuanian suzerainty.

In 1592 Sweden threatened the Baltic lands in the Polish-Lithuanian Commonwealth. The bulk of Livonia, with Riga, was ceded to Sweden in 1629. The southeastern portion, Latgale, remained a part of Lithuania.

The Swedish period brought peace between Estonia and Latvia. The Swedish kings, used to a free peasantry, made the local nobles improve the serfs' conditions. Compulsory elementary education was introduced, the Bible was translated into indigenous languages, a secondary school was opened in Riga in 1631 and a university in Dorpat in 1632. But more Swedish efforts were largely thwarted by wars.

Courland, nominally under Lithuania, developed as an independent state. Duke Jacob (1642–82) encouraged trade, industry and created a navy. He acquired 2 colonies: Tobago in the West Indies and a settlement in Gambia on the west coast of Africa.

San Diego Sarah  •  Link


From the second half of the 17th century, the Baltic region faced increasing Russian pressure. Lübeck lost its place as the main trading post.

In the mid-17th century, peasant unrest among Ukrainean Cossacks and war with Sweden over Livonia strained the Polish-Lithuanian Commonwealth resources.
Vilnius was taken by a Russian army in 1655.
The Truce of Andrusovo in 1667 reestablished a balance with Moscow.

Excerpted from…

L&M Companion: The Steelyard: On the south side of (Upper) Thames St., now covered by Cannon Street Station.
Once the London house of the Hansa merchants. The property extended to the river, its 4 acres including the merchants' hall, wharves, warehouses, and private dwelling houses, and in earlier centuries had been an important factor in the life of the city.

"Their hall," says Stow, "is large, built of stone, with three arched gates towards the street, the middlemost whereof is far bigger than the others, and is seldom opened; the other two bemured up; the same is now called the old hall."

More about the remaining Hansiatic League participants in London at…

San Diego Sarah  •  Link

February 24, 1659 -- Parliament votes to send a fleet to the Baltic for the preservation of Commonwealth trade and commerce. RCII

(End of March) Edward Montagu appointed commander of a fleet of 40 ships to sail for the Baltic to defend England's commercial interests and to counteract Dutch attempts to intervene in the war between Sweden and Denmark. CN

April 6, 1659 -- Montagu's fleet arrives at Elsinore to find the forces of Charles X of Sweden besieging Copenhagen. Montagu attempts to persuade the Dutch not to intervene on Denmark's side. ODNB

May 11, 1659 -- A treaty signed at The Hague between England, France and the United Provinces to mediate for peace between Denmark and Sweden. RCII

May 25 -- Richard Cromwell's abdication of his offices read in Parliament together with a schedule of his debts. Parliament agrees to assume his public debts and appoints a committee to consider a comfortable subsistence for him. RCII

July 8, 1659 -- The Council of State orders Vice-Adm. John Lawson to sea with a squadron to watch the Flanders coast for signs of preparation for a Royalist invasion force. All infantry and cavalry regiments to be recruited to full strength. The garrisons at Newark and Nottingham strengthened with troops from Newcastle. RCII

August 24, 1650 -- Montagu's fleet sails from the Baltic Sound for England, greatly weakening the influence of the English commissioners. CN

September 6, 1659 -- Montagu's fleet arrives back in England. CN

September 10 -- General-at-Sea Edward Montagu reports to the Council of State. Under suspicion of involvement in Royalist conspiracies, his commission is revoked and he retires to his country estate. TR…


In March 1659, Montagu commanded a fleet sent to the Baltic to defend England's commercial interests and to counteract a Dutch attempt to intervene in the war between Sweden and Denmark, but his diplomatic efforts were interrupted by the fall of the Protectorate and the return to power of the Rump Parliament in May 1659. Republicans mistrusted Montagu and suspected that he was in contact with Royalists, particularly as his return to England coincided with Booth's Uprising and a series of planned Royalist insurrections around the country. Montagu protested his loyalty before Parliament. Although no evidence could be found against him, his commission was revoked and he retired once again to Hinchingbrooke.…

San Diego Sarah  •  Link

Edward Montagu was an English admiral and nobleman who served in the English fleet which became involved in the hostilities between Sweden and Denmark-Norway in 1659.

That year Montagu maintained a correspondence with the Swedish king.
He informed Karl X that Richard Cromwell was keen to encourage a peace between the two parties, and had commanded Montagu to sail into the area to help keep the peace.

When Montagu wrote to Karl X in mid-April he was quite negative toward him for not having signed the Treaty of Roskilde and for not keeping him informed of developments. As Cromwell was a guarantor of the Treaty it was important for Sweden to sign, as otherwise if England continued to support Sweden she was liable to attack from the Dutch and this was not a desired outcome!

On 20 May Montagu explained that the fleet was maintaining its position in the Skagen near Jutland, and that he was required to transport the Duke of Holstein and so would not be able to have an audience with Karl X.

He also sent a letter to the speaker of the English parliament, W. Lenthall, from aboard the 'Näsbye' in the Sound, regarding peace negotiations between Denmark and Sweden.

Swedish Riksarkiv, Anglica 522;
Bodleian Library Tanner MSS;
L. Bittner and L. Gross, Reportorium der diplomatischen vertreter aller lander, vol. 1, 1648-1715 (Oldenburg and Berlin, 1936), pp.183, 199;
G. M. Bell, A Handlist of British Diplomatic Representatives 1509-1688 (London, 1990); PRO, SP/75/16-17;
Swedish Riksarkiv, Svenske Sändebuds till Utländske Hof och Deras Sändebud till Sverige, 1841, p.84.

Service record
Arrived 1659-06-30, as ADMIRAL
Departed 1659-09-13, as ADMIRAL


San Diego Sarah  •  Link

For a deep dive into the Baltic affaires that had Montagu sent there with 41 ships in the summer of 1659, see
"Ships, sailors, and mediators: England's naval aid to Sweden 1658-1659"
by Mary Elizabeth Ailes, an associate professor in the History Department at the University of Nebraska at Kearney.…

The universal silence about Montagu's outreach to Charles II indicates how secret it was -- nothing official must exist.

San Diego Sarah  •  Link

On 25 June, 1660, Pepys records: "Dined with young Mr. Powell, lately come from the Sound, ..."

Paul Brewster on 26 Jun 2003 said "L&M annotate this reference with a discussion of Montagu's service in the Baltic."

I've searched both my 1660 Diary and my Companion and not found any discussion of Montagu's service in the Baltic. In his personal biography there is less detail than I found (above) apart from a reference to this being the time he started communications with Charles II -- no specifics given about that either.

Can anyone fill in the gap?

San Diego Sarah  •  Link

My guess about what Mr. Powell was doing in the Spring of 1660:

"In February 1660, Charles X Gustavus died and with his death, the impetus to continue the war from the Swedish viewpoint vanished.
Because of war weariness and the need to consolidate the regency of the new king, Charles XI, the Swedish Council of the Realm entered into serious peace negotiations with the Danes.
Throughout the spring of 1660, the English, Dutch, and French mediators hammered out a treaty based upon the agreements they had concluded at the Hague during the previous summer.
The end result was that on 27 May 1660 the Treaty of Copenhagen was signed which, confirming the stipulations of the peace settlement created 2 years earlier at Roskilde, permanently divided geographical control of the Sound and thus produced a balance of power between the Swedish and Danish kingdoms.

"Even though the English squadron was not in the Baltic during the negotiations' last stages, its presence during the crucial period of the summer of 1659 had helped to safeguard both English and Swedish interests.
By the summer of 1658, the Dutch naval presence in the Baltic had begun to swing the balance of naval power in the Danes's favor. The English squadron's entrance into the conflict helped to recreate the balance of naval power between the two combatants and their allies and helped to prevent Dutch or Danish attacks upon the Swedish navy or Swedish territory.
Even after Montagu's forces sailed back to England, the potential threat that a new English squadron might return to the Baltic helped to legitimize the English mediators' roles at the peace negotiations.
As George Downing, the English representative at The Hague wrote to Secretary Thurloe and to the Council of State, the Dutch government encouraged a speedy resolution to the war, during the winter of 1660, partly because it feared that the English Parliament would send another squadron to the Baltic when the weather cleared in the spring, which would hamper its efforts to gain economic advantages from the peace settlement.
Additionally, the Dutch rulers feared that if they broke the agreements concluded the previous summer at The Hague, the English and the French would combine forces with the Swedes to attack them, which would entangle them in a more wide-scale conflict.
Because all concerned parties knew that the English were willing to use their fleet to intervene in Scandinavian affairs, the English government's concerns and interests were taken into account in the peace settlement. In the end, the balance of power between the two sides allowed the mediators to create a treaty that reconfirmed the existing status quo of a divided Sound, and which thereby served the economic interests of both English and Dutch merchants.

San Diego Sarah  •  Link


"The English naval intervention in Scandinavian affairs in 1658 and 1659 represented the growing military strength and diplomatic utility of the English navy.
Throughout the 1650s, the government had poured many resources into expanding the navy and through engagements against Royalists, the Dutch, and the Spanish created a professional officer corps and gained experienced, veteran sailors.
Because of the navy's military capabilities and proven loyalty to the Protectorate, in 1658 the government used it to promote the state's interests overseas.
Rather than providing military defense or attacking England's enemies, the navy now used its might to intervene in a foreign conflict and to encourage the combatants and their allies to accept policies that favored English interests.
Such actions by the navy would become commonplace after this point. ...
Thus, the English naval involvement in Scandinavian affairs during the 1650s represents the first steps into a new era when the state possessed a professional navy, which was used increasingly to express the government's policies abroad."


Mr. Powell appears to have been involved, along with George Downing, in the 27 May, 1660, signing of the Treaty of Copenhagen.

San Diego Sarah  •  Link

Why did Joint General Edward Montagu abandon his extreme anti-royalist position to embrace the Restoration?

A readable account is given in the biography, "Algernon Sidney, The Porcupine: the Life of Algernon Sidney" by John Carswell (1989), John Murray, Publishers.

Years ago I found a website devoted to the Montagu family, which sadly has disappeared. But I copied their extracted explanation of Adm. Montagu's switch in position, told from the perspective of Algernon Sidney.
The editing is theirs:

The balance of power in the Northern Kingdoms had greatly changed ... the Danish King had complete control of the narrow international waterway leading to ... the Baltic ... the Sound ... they levied a toll on every cargo ...
... the emerging power of Sweden... had broken Danish control... France, Britain, and the Netherlands had therefore found common ground ... in May 1659 to impose peace ... All 3 sent special missions to Denmark... and in the case of the English and Dutch, the greater part of their navies...
... the three powers ... had their differences ... The Dutch favored the Danes, the English the Swedes ... It was highly probably, given the immense concentration of Dutch, English, Danish, and Swedish naval and military force round the Sound, that the intervention for peace would end in a general war.

On 18 July, 1659, the Langport cast anchor off Elsinore ... Parliament, following its usual cautious habits, had given Algernon Sidney colleagues [SIC] ... The remaining commissioner was Adm. Sir Edward Montagu, commanding the English fleet in the Sound, who welcomed his colleagues on board his flagship, the Naseby.
The welcome was no doubt the more splendid because Sidney and Montagu were related, although distantly.
In attendance on Edward Montagu was a young secretary, Samuel Pepys, and it is a pity he had not yet begun his diary.
Algernon Sidney had been warned about Edward Montagu by spy-master John Thurloe ... and told that if the Admiral showed any sign of disaffection he should be put under arrest.

Ever since the beginning of the Civil Wars, Edward Montagu had been steady in the Parliamentary cause, but now his loyalty to the republic was doubtful. As a Cavalier agent ... had secretly written to ... the exiled Charles II's chief advisor, `When Montagu doth come home he will either lay by himself, or be laid by by the Parliament. This is the most favorable occasion that ever was to tempt him.'
From this arose the journey of the Cavalier emissary, Capt. [Sir Thomas] Whetstone ...

San Diego Sarah  •  Link


As Pepys discovered later, Adm. Montagu had no religious ideals, but he had a principle, which was settled government. `I had rather the nation were settled', he said later shortly before the Restoration, `though I and my whole family should suffer by it.'
The second half of this remark was cant, as Montagu fully intended he and his family should prosper, but he did not seek office for himself. His aim, which it was to take a long time to achieve, was stability. The navy which he commanded had been a major, perhaps decisive, factor in the defeat of King Charles.

Less than a year after Algernon Sidney's arrival at Elsinore, that navy would carry Charles II back to his throne, and Montagu would bear the sword of state before Charles II at his coronation just as he had borne it before the Lord Protector Oliver at his installation.

Thoughts of this kind had probably crossed Montagu's mind even before he sailed with his fleet from England, but his mind was made up in the Sound.

Montagu's conversion to Charles II's cause, he later told Pepys, 'commenced from his being in the Sound, when he found what usage he was likely to have from the Commonwealth.' It is difficult to believe that Algernon Sidney's uncompromising rectitude ... did not contribute to this decision, and Montagu often afterwards referred to him as 'my mortal enemy' ...

For 40 days ... Algernon Sidney ... was to have total control of the Fleet assembled there. But it had already been on station for several months and was in urgent need of rest and refit ...

Montagu did not fail to impress these facts on his guests ... He showed them around his fleet, dwelling on the need for a refit and the longing of every man from the admiral downwards to be home again after spending so long at sea. Crews, he pointed out, had been thinned by death and sickness, and there were no replacements ...

(By this time, things were also getting out of control on land, and even the Dane's German allies were beginning to show up for the fight. At this point, Algernon Sidney pulled off a diplomatic coup, by taking decisive action, using the fleet as a threat, staring everybody involved down (including his allies), and acting like he was completely in charge, even with respect to Frederik III of Denmark and Charles X of Sweden... alas, it was not to last long... ed.)

... The Cavalier agent [Whetstone] arrived in Denmark only a week or so after Algernon Sidney ... and immediately put himself in Montagu's way, first at a public dinner, where he professed not to recognize the admiral (who recognized him), and then during a sight-seeing trip ... to Copenhagen. ...

An undersecretary in Parliament, Sir Samuel Morland, was a Cavalier agent. Capt. Whetstone was thus able to give Montagu a copy of Algernon Sidney's full orders, including those ordering his arrest if he appeared disloyal.

San Diego Sarah  •  Link


Two secret meetings followed, at which Charles II's letter to Montagu was delivered and answered, and Whetstone left ... in a ship thoughtfully provided by the Dutch... and ... reported ... that `upon any appearance of disorders in England' Charles II `might expect a good account' of Montagu, who would write further when he got home.

Next day ... Montagu went on board, held a council of war with his officers, and sailed, leaving only one frigate and a ketch behind. ... The arrival of the fleet in England was probably the decisive factor in ending the Republic,

... A third Civil War seemed on the point of breaking out. ... It was just the situation Montagu had foreseen when he assured Charles II through Capt. [Sir Thomas] Whetstone that he would come out for the King `upon any appearance of disorders in England' ... Renewed Civil War was now too high a price to pay for the ideals of parliamentary sovereignty over the Army.

The matter was not decided by politicians but by the soldiers ... In the Civil Wars Englishman had fought Englishman... but the soldiers of 1659 had served together far too long to do that....' (They had a `phony war'. Parliament had given itself direct command of the Army but it was not united; it was using the Army to extend factional political conflict. The soldiers would fire their pistols into the ground and exchange jokes about the incompetence of the politicians when they encountered each other; Parliament and Army leadership were denigrated and lost legitimate 'command authority', ed.)

John Carswell has been able to recreate the mission and orders of the Cavalier agent, Capt. [Sir Thomas] Whetstone, using historical records and letters.

Carsell also notes: `The intermediary between Capt. [Sir Thomas] Whetstone and the Admiral was confusingly also called Edward [Ned] Montagu - a cousin of the admiral and a convinced royalist.'

The fleet did not go to sea again until May 1660 when, with Adm. Edward Montagu once more in command, it ferried Charles II home in triumph.

The useless link is…

Other Resources:……

San Diego Sarah  •  Link

L&M Companion: Edward "Ned" Montagu (1635-65). Eldest son of the 2nd Baron Montagu of Boughton (d. 1684) and Sandwich's first cousin twice removed. M.P. for Sandwich from 1661, and Master of the Horse to Queen Mother Henrietta Maria.
He acted as go-between when the royalist agent Whetstone first made contact with Adm. Montagu on the Baltic voyage in the summer of 1659, ...

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Chart showing the number of references in each month of the diary’s entries.




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