Baltic Sea

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Coordinates: 58°N 20°E / 58°N 20°E / 58; 20
Source: Wikipedia, the free encyclopedia.

Baltic Sea region
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
References[2]
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.

The sea stretches from 53°N to 66°N latitude and from 10°E to 30°E longitude. It is a

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.

Definitions

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

Administration

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]

Oceanography

Geographers widely agree that the preferred physical border between the Baltic and North Seas is the Langelandsbælt (the southern part of 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

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

the Belts, while others claim it to be directly derived from the source of the Germanic word, Latin balteus "belt".[10] 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

Baltic language such as Lithuanian.[13] 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.[14]

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.[15] 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:

History

Classical world

At the time of the

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

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.[18] 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

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.[19] 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.

Dano-Swedish War
.
Nautical chart of the Baltic Sea in 1919.
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,

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

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

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

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

exclave
.

Winter storms begin arriving in the region during October. These have caused numerous

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 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.[25]

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.[26] 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.[27]

Geography

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) [28] 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.[29]

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[30]
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

Extent

The International Hydrographic Organization defines the limits of the Baltic Sea as follows:[31]

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

Subdivisions

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

Zealand
.

In the south, the

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).[33] 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).[33] 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

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.[34]

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.[35] 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.[36] 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.[37]

Piles of drift ice on the shore of Puhtulaid, near Virtsu, Estonia, in late April

During winter,

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

Taarbaek on 15 May 1942 and near Copenhagen on 11 May 1771. Drift ice was also observed on 11 May 1799.[39][40][41]

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.

Hydrography

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 .[42]

The difference between the outflow and the inflow comes entirely from fresh

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.[43][44]

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.[45]

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) .[42] 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.[46]

Salinity

Baltic Sea near Klaipėda (Karklė).

The Baltic Sea is the world's largest inland

brackish sea.[47] 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.[47]

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 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%.[48] 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 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.[49] 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.[48]

In contrast, the salinity of the

major Baltic inflows (MBIs)
.

Major tributaries

See also: List of rivers of the Baltic Sea

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
Discharge
(m3/s)		 Length (km) Basin (km2) States sharing the basin Longest watercourse
Neva 2500 74 (nominal)
860 (hydrological)		 281,000 Russia, Finland (Ladoga-affluent Vuoksi)
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

Main article: List of islands in the Baltic Sea
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.[51]

Cities

Main article: List of cities and towns around the Baltic Sea
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:

Geology

Main article: Geology of the Baltic Sea
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.
Evolution of the Baltic Sea
Pleistocene
Eemian Sea (130,000–115,000 BC)
Ice sheets and seas (115,000–12,600 BC)
Holocene
Baltic Ice Lake (12,600–10,300 BC)
Yoldia Sea (10,300–9,500 BC)
Ancylus Lake (9,500–8,000 BC)
Mastogloia Sea (8,000–7,500 BC)
Littorina Sea (7,500–4,000 BC)
Modern Baltic Sea (4,000 BC–present)

The Baltic Sea somewhat resembles a

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

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

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"

Main article: Baltic Sea anomaly

The "Baltic Sea anomaly" is a feature on an indistinct

UFO. A consensus of experts and scientists say that the image most likely shows a natural geological formation.[53][54][55][56][57]

Biology

Fauna and flora

See also: List of fish in Sweden

The fauna of the Baltic Sea is a mixture of marine and freshwater species. Among marine fishes are

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.[33] 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.[58][59] The common blue mussel is the dominating animal species, and makes up more than 90% of the total animal biomass in the sea.[60]

There is a decrease in species richness from the Danish belts to the

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.[33] 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

lumpsucker, which are smaller than the widespread forms in the North Atlantic.[50]

A peculiar feature of the fauna is that it contains a number of glacial

Monoporeia affinis, which is a main element in the benthic fauna of the low-salinity Bothnian Bay
.

Bothnian Gulf[75] and Ystad[76]) and eastern population of North Atlantic right whales that is facing functional extinction[77] once migrated into Baltic Sea.[78]

Other notable megafauna include the basking sharks.[79]

Environmental status

Further information: Baltic Sea hypoxia
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.[80]

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.[81]

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.[82]

Economy

See also: Baltic Sea cruiseferries, Ports of the Baltic Sea, and List of oil and gas fields of the Baltic Sea
Pedestrian pier in Sellin, Germany

Construction of the

oil pollution.[citation needed
]

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.[83]

Tourism

Klaipėda county
, Lithuania
Svetlogorsk resort town in Kaliningrad Oblast, Russia
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

Main article: Helsinki Convention on the Protection of the Marine Environment of the Baltic Sea Area

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,[84] 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

Notes

  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.
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Further reading

Historical

External links

Wikimedia Commons has media related to Baltic Sea.
American Cyclopædia article Baltic Sea
.
Wikisource has the text of the 1911 Encyclopædia Britannica article "Baltic Sea".
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