Bothnian Bay

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

Bothnian Bay
The rocky shoreline of Ohtakari, in the southeast of the bay
Bothnian Bay is located in Europe
Bothnian Bay
Bothnian Bay
Location in Europe
Coordinates65°N 023°E / 65°N 23°ECoordinates: 65°N 023°E / 65°N 23°E
Primary outflowsBothnian Sea
Catchment area260,675 km2 (100,647 sq mi)
Basin countriesFinland, Sweden, Norway
Surface area36,800 km2 (14,200 sq mi)
Average depth43 m (141 ft)
Max. depth147 m (482 ft)
Water volume1,490 km3 (360 cu mi)
Frozen110–190 days annually


The bay is divided from the Bothnian Sea, the southern part of the Gulf of Bothnia, by the Northern Quark (Kvarken) strait. The Northern Quark has a greatest depth of 65 metres (213 ft), with two ridges that are just 25 metres (82 ft) deep. It lies between a group of islands off Vaasa in Finland and another group at Holmöarna in Sweden.[1] The bay is bounded by Finland to the east and Sweden to the west. The bay is asymmetric, with a smoother and shallower bottom slope on the Finnish side, and a deeper bottom with a steeper and more rugged coast on the Swedish side.[1]

The Bothnian Bay has a catchment area of 260,675 square kilometres (100,647 sq mi). Of this, 56% lies in Finland, 44% in Sweden and less than 1% in Norway.[2] The catchment contains about 11,500,000 hectares (28,000,000 acres) of forest, split roughly equally between Sweden and Finland.[3]

The average depth is 41 metres (135 ft). The Luleå Deep is the deepest part of the bay, at 146 metres (479 ft), southeast of the town of Luleå.[4] On the Finnish side the average depth is 30 metres (98 ft). The deepest part is near the island of Lönkytin, with a depth of 50 metres (160 ft).[5]


Map of the Gulf of Bothnia showing location of Bothnian Bay (shaded and labelled Bottenviken)

Bothnian Bay map-fi

Finnish map of the bay – click to enlarge

Scandinavia M2002074 lrg

Satellite image of Fennoscandia with sea ice covering the Bothnian Bay (white region in center)

Isostatic rebound

The bay lies in the area in Northern Europe where the ice was at its thickest during the last ice age.[6] The Bay of Bothnia was under ice until the "Ancylus Lake" period (7500–6000 BC), when the ice sheet withdrew to the mountains of Northern Scandinavia.[7] The land is now rising by post-glacial rebound at the highest rate in the Baltic Sea, at an estimated rate of 9 millimetres (0.35 in) a year.[8] Today the Bothnian Bay lies around 300 metres (980 ft) higher than it did at the end of the Ice age.[6] The local population has seen the sea retreating during their lifetimes from piers and boathouses, leaving them stranded on land. Some former islands such as Porsön and Hertsön near the city of Luleå are still called islands, but are now connected to the mainland.[9]

The maximum depth at the Kvarken sound today is around 20 metres (66 ft). In not less 2,000 years the exit from the bay at Kvarken will be raised above sea level, which will result in it becoming Europe's largest lake.[10]


Vihreasaari Oulu 2006 11 04
A cargo ship approaching the Vihreäsaari harbour in Oulu, Finland, while the Bay of Bothnia starts to freeze for this winter

The Bothnian Bay has a harsher environment than other parts of the greater Baltic sea.[11] The bay is ice-covered for 110 to 190 days each year.[12] Tides have little effect, but high winds driving the water from the south or north may cause the water level to rise or fall by 1.5 metres (4 ft 11 in).[9]

Major rivers that flow into the bay include:

River Country Discharge
Kemijoki Finland 556 m3/s (19,600 cu ft/s)
Lule River Sweden 506 m3/s (17,900 cu ft/s)
Torne River Sweden and Finland 388 m3/s (13,700 cu ft/s)
Kalix River Sweden 295 m3/s (10,400 cu ft/s)
Oulujoki Finland 250 m3/s (8,800 cu ft/s)
Pite River Sweden 167 m3/s (5,900 cu ft/s)
Skellefte River Sweden 162 m3/s (5,700 cu ft/s)
Iijoki Finland 164 m3/s (5,800 cu ft/s)

The salinity is only about 0.2 psu in the northern part of the bay, dropping almost to zero in some of the archipelagos with large river inflows.[13] The low salinity and cold temperatures in winter results in ice that is considerably stronger than more saline or warmer ice.[14]


Hermanni Islands in Oulu 2006 11 04
The Hermanni islands. A wintery view of a group of small islands in the Bothnian Bay near Oulu, Finland
Ronnskar fyren
The lighthouse on the island of Pite-Rönnskär in Bothnian Bay

If an island is defined as an area of land more than 20 square metres (220 sq ft) that is surrounded by water, the Bay of Bothnia has 4,001 islands.[9] The largest island is Hailuoto.[1] The north of the bay contains a large archipelago area.[1] The Swedish portion of this area is the Norrbotten archipelago.[15] This is divided into the Piteå, Luleå, Kalix and Haparanda archipelagos.[16] Many of the islands are uninhabited and in a natural state.[17] In the winter the larger islands may be accessed via ice roads. Some of them are inhabited or have seasonal fishing villages used by people from the mainland.[9]

The Swedish Haparanda Archipelago National Park (Swedish: Haparanda skärgårds nationalpark) occupies the Haparanda group of islands, bordering the Finnish Bothnian Bay National Park. It includes the larger islands of Sandskär and Seskar Furö, and some smaller islands and skerries. All of these islands have emerged in the last 1,500 years as the bed of the bay has risen.[18] The Bay of Bothnia National Park in the Finnish section (Finnish: Perämeren kansallispuisto, Swedish: Bottenvikens nationalpark), established in 1991, is located in the archipelago offshore from Tornio and Kemi. It covers 157 square kilometres (61 sq mi) of which about 2.5 square kilometres (0.97 sq mi) is land.[19]


The Quark ridge at the south of the bay defines the dividing line beyond which many salt water species are unable to survive.[20] Instead of the red and brown algae found further south, the bay has predominantly green algae and phanerogams.[11] Annual plant species are almost completely dominant. The only perennials are a few specimens of the freshwater cryptogram Isoetes echinospora and the moss Fontinalis dalecarlica.[21] Often the green algae have a dense covering of epiphytic diatoms.[22] The shores, beaches and shallows include a variety of northern plant species including the endemic yellow hair grass (Deschampsia bottnica).[9]

The only filter feeders are Ephydatia and, at the river mouths, small numbers of freshwater mussels.[22] Bivalves make up 9% of animal biomass. Crustaceans, mostly Saduria entomon make up 45% and gastropoda 30%.[23] The gastropoda are grazing snails related to freshwater species.[24]

Fish species found in the area's lakes and rivers also live in the bay, including roach, perch, pike and grayling.[20]

Ringed seal, grey seal, cod, herring and salmon may also be found in the bay.[9] In the 16th century seals were hunted in the Bay of Bothnia. Ringed seals were captured using nets in the inshore open water, and were stalked and captured in their dens or at breathing holes. Both grey and ringed seals were hunted along the edge of the ice.[25] Wild salmon roe harvested from the Kalix River, known as Kalix Löjrom or as sea gold, is a delicacy with a European protected designation of origin.[26]

Birdlife includes the black guillemot, velvet scoter, oystercatcher, lesser black-backed gull, western capercaillie and willow ptarmigan. Moose and hare are found on the islands, as on the mainland.[9]

Occasionally, whales have been observed in Bothnian Sea[27] and remains of extinct Atlantic gray whale was found from Gräsö[28] while it is not clear whether or not whales might once reached Bothnian Bay historically.


Raahe Old Town 2008 07 10
Old Raahe, Finland
Lulea industry
Industrial zone in Luleå

Ports on the Finnish side include Haukipudas, Jakobstad, Kemi, Kokkola, Oulu, Raahe and Tornio.[29] The largest towns by population on the Finnish side as of 2013 were Oulu (192,680), Tornio (22,374), Kemi (22,157), Kempele (16,549), Raahe (25,641), Kalajoki (12,637), Kokkola (46,697) and Jakobstad (19,636).[30] In Finland the catchment area included about 544,000 hectares (1,340,000 acres) of arable land as of 1993. There were four Finnish pulp and paper mills, of which two (Veitsiluoto Oy and Metsä Botnia Oy) were producing bleached kraft paper.[31]

On the Swedish side ports include Haparanda, Karlsborg, Kalix, Luleå, Piteå and Skellefteå.[29] The largest towns on the Swedish side as of 2013 were Luleå (74,000), Skellefteå (71,641), Piteå (40,860) and Kalix (16,926). Luleå is the largest city in Norrbotten, with the largest airport. The 1,312 islands of the Luleå archipelago are an important tourist attraction, as is the Gammelstad church village, listed as a Unesco World Heritage site.[26] As of 1993 there were about 113,000 hectares (280,000 acres) of arable land in the Swedish part of the catchment basin, mostly used for small-scale low-intensity farming. There were five pulp and paper mills, of which one produced bleached kraft paper.[31]

In the late 1960s the bay was being used to transport fuel oil to the Finnish settlements around the bay. In 1968 about 950,000 tons of cellulose and 230,600 tons of paper and cardboard were exported, a figure that was rising.[32] In 1968 ships calling at the Finnish ports carried about 388,872 tons of iron bars and 64,326 tons of steel sheets. Mining and mineral products such as coal and ore were carried to and from the ports, and steel products were exported.[33] Sea transport continued throughout the winter.[32] In 1993 there were two non-ferrous heavy metal smelters, in Rönnskär and Kokkola, emitting significant quantities of heavy metals. Efforts were being made to reduce emissions. The drainage basin also held three iron and steel plants and a number of mines.[31]

Human activities have affected the fragile sub-arctic environment. Dredging and other activities related to sea transport affect marine life. Agriculture, forestry and peat mining in the catchment basin add nutrients to the bay, affecting the ecological balance, while pollutants are delivered from steel mills and from pulp and paper mills around the bay, as well as from sewage treatment plants.[34] Steel mills and stainless steel plants may have released nickel and chromium.[2] Efforts have been made to reduce pollution through improved technology, but some areas along the Finnish coastline show evidence of eutrophication.[34] Compared to other parts of the Baltic, higher levels of nitrate have been found in the Bothnian Bay and lower levels of phosphate and silicates.[35]


Seskaro bridge

The bridge to Seskarö, Sweden

Icebreaker Fennica

Finnish icebreaker MSV Fennica in the Bay


Looking back from the Icebreaker Sampo near Kemi, Finland

Outokumpu mill in Tornio 20121015

Outokumpu mill in Tornio

Oulu Toppila

Old mill buildings and harbour in Toppila, Oulu, Finland

20080227 Varessäikkä Siikajoki

Buildings and the birdwatching tower at Varessäikkä harbour, Siikajoki, Finland

Mökki Pallosessa

Old fisherman's cottage


Lönkytin island

Kahvankari Oulu

The island of Kahvankari in Oulu, Finland

Kraaseli in Kello

The eastern shore of the Kellon Kraaseli island, Haukipudas, Finland

Bothnian Bay Kemi

Bothnian Bay in Kemi, Finland


Sunset at Hiekkasärkät, Kalajoki, Finland



  1. ^ a b c d Leppäranta & Myrberg 2009, p. 55.
  2. ^ a b Szefer 2002, p. 11.
  3. ^ Baltic Sea Joint Comprehensive Environmental Action, pp. 2–3.
  4. ^ Leppäranta & Myrberg 2009, p. 56.
  5. ^ Merikartta Perämeri osa 57.
  6. ^ a b Røed 2011.
  7. ^ Leppäranta & Myrberg 2009, p. 11.
  8. ^ Nesje 2006.
  9. ^ a b c d e f g About the Bay ... Bottenvikens skärgård.
  10. ^ Tikkanen, Matti; Oksanen, Juha (2002). "Late Weichselian and Holocene shore displacement history of the Baltic Sea in Finland". Fennia. 180 (1–2). Retrieved December 22, 2017.
  11. ^ a b Eleftheriou, Smith & Ansell 1995, p. 23.
  12. ^ Müller 1982, p. 8.
  13. ^ Eleftheriou, Smith & Ansell 1995, p. 24.
  14. ^ Mäkinen 1972, p. 3.
  15. ^ Ankre 2005, p. 8.
  16. ^ Index:
  17. ^ Sweden: Rough Guides 2003 403.
  18. ^ Haparanda Skärgård National Park.
  19. ^ Bay of Bothnia National Park.
  20. ^ a b Bottniska viken: Stockholms universitets.
  21. ^ Eleftheriou, Smith & Ansell 1995, p. 25.
  22. ^ a b Eleftheriou, Smith & Ansell 1995, p. 26.
  23. ^ Eleftheriou, Smith & Ansell 1995, p. 33.
  24. ^ Eleftheriou, Smith & Ansell 1995, p. 29.
  25. ^ Kvist 1991, p. 339.
  26. ^ a b Swedish Lapland: The destination.
  27. ^ Yle Uutiset. 2006. Humpback Whale Spotted in Gulf of Bothnia. Retrieved on September 05, 2017
  28. ^ Jones L.M..Swartz L.S.. Leatherwood S.. The Gray Whale: Eschrichtius Robustus. "Eastern Atlantic Specimens". pp 41-44. Academic Press. Retrieved on September 05, 2017
  29. ^ a b Bothnian Bay: Port Map.
  30. ^ Väestötietojärjestelmä Rekisteritilanne.
  31. ^ a b c Baltic Sea Joint Comprehensive Environmental Action, pp. 2-3.
  32. ^ a b Mäkinen 1972, p. 4.
  33. ^ Mäkinen 1972, p. 5.
  34. ^ a b Laine 2013, p. 1.
  35. ^ Szefer 2002, p. 134.


Bothnia (disambiguation)

Bothnia or Bothnian may refer to:

Gulf of Bothnia, a gulf of the Baltic Sea between Sweden and Finland

Bothnian Bay, the northernmost waters of the gulf

Bothnian Sea, the southernmost waters of the gulf

Provinces in Sweden and Finland named after the gulf:

Ostrobothnia (disambiguation), multiple entities

West Bothnia, located west of the gulf

North Bothnia, located northwest of the gulf

SS Bothnia, transatlantic steamship (1874–99)

Bothnia Line, high speed railway in northern Sweden

Bothnian Bay National Park

Bothnian Bay National Park (Finnish: Perämeren kansallispuisto, Swedish: Bottenvikens nationalpark) is a national park in Lapland, Finland. The park which was established in 1991, covers 157 square kilometres (61 sq mi) of which 2.5 square kilometres (0.97 sq mi) is on land. It is maintained by Metsähallitus.

The islands in the area have been formed by post-glacial rebound, and the scenery is still in a constant state of change. There are also numerous traditional fishing bases.

The national park is reachable by boat although visiting is only recommended for experienced boaters.

Bothnian Sea

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

Coregonus albula

Coregonus albula, known as the vendace or as the European cisco, is a species of freshwater whitefish in the family Salmonidae. It is found in lakes in northern Europe, especially Finland, Sweden, Russia and Estonia, and in some lakes of Norway, the United Kingdom, northern Germany, and Poland. It is also found in diluted brackish water in the Gulfs of Finland and Bothnia, both of which are in the Baltic Sea.The length of an adult is normally about 20 cm (8 in). The maximum age is about ten years.

The vendace is traditionally the most important target of freshwater fisheries in parts of Fennoscandia and Russia. Vendace roe is considered a delicacy, which has been granted a PDO status in the Swedish Bothnian Bay archipelago (Kalix löjrom).

Haparanda Archipelago National Park

Haparanda Archipelago National Park (Swedish: Haparanda skärgårds nationalpark) is a national park in Haparanda Municipality, Norrbotten County, Sweden.

The park covers part of the Haparanda archipelago in the northeast of the Bothnian Bay near the border with Finland.

There are two relatively large islands, Sandskär and Seskar Furö, and several smaller islands and reefs.

The park is to the west of the Finnish Perämeri National Park.All of the islands in the Haparanda archipelago have emerged in the last 1,500 years or so, as the bed of the bay has risen due to post-glacial rebound following the last ice age.The land continues to rise at about 8.5 millimetres (0.33 in) per year, so the islands are steadily expanding.

The water surrounding the islands is shallow, making it difficult to land.

The islands are typified by large dunes.


Hertsön is a Swedish island in the Bothnian Bay, largely occupied by the eastern districts of the city of Luleå.

Due to post-glacial rebound, the islands Svartön, Mulön, Granön and Björkön have merged with the island. The size of the island is around 73 km², making it the twelfth largest island in Sweden.

Ii, Finland

Ii (Finnish pronunciation: [iː]; Swedish: Ijo) is a municipality of Finland.

It is situated by the Bothnian Bay, at the mouth of river Iijoki, and it is part of the Northern Ostrobothnia region. The municipality has a population of 9,889 (31 January 2019) and covers an area of 2,872.44 km2 (1,109.06 sq mi) of which 1,256.69 km2 (485.21 sq mi) is water. The population density is 6.37/km2 (16.5/sq mi).

The municipality is unilingually Finnish.

Ii merged with Kuivaniemi on 1 January 2007. The formed municipality is called Ii but it adopted the coat of arms of Kuivaniemi. Ii is notable for having the shortest place name in Finland, and also one of the shortest ones in the world. The etymology is not definitively established; options are either Germanic origin or Sami origin. In the latter, it would mean "a place to stay overnight in"; cf. Northern Sami idja "night".Beginning in 2008, Ii is home to the ART Ii Biennale of Northern Environmental and Sculpture Art, an international art fair.


Jormasjärvi is a lake in Sotkamo, eastern Finland. It is part of the Oulujoki basin, which drains west to the Bothnian Bay.

The area of the lake is 20.5 square kilometres, and maximum depth 28 m.


Kemi (Northern Sami: Giepma) is a town and municipality of Finland. It is located very near the city of Tornio and the Swedish border. It was founded in 1869 by decree of Russian Emperor Alexander II because of its proximity to a deep water harbour.

Kemi is situated by the Bothnian Bay, at the mouth of river Kemijoki, and it is part of Lapland region. The town has a population of 20,991 (31 January 2019) and covers an area of 747.28 square kilometres (288.53 sq mi) of which 652.1 km2 (251.8 sq mi) is water. The population density is 220.17 inhabitants per square kilometre (570.2/sq mi).


Kvarken (Swedish Kvarken or Norra Kvarken (as opposed to South Kvarken), Finnish Merenkurkku lit. "throat of the sea") is the narrow region in the Gulf of Bothnia separating the Bothnian Bay (the inner part of the gulf) from the Bothnian Sea. The distance from Swedish mainland to Finnish mainland is around 80 km (50 mi) while the distance between the outmost islands is only 25 km (16 mi). The water depth in the Kvarken region is only around 25 metres (82 ft). The region also has an unusual rate of land rising at about 10 mm (0.39 inches) a year.

On the Finnish side of Kvarken, there is a large archipelago, the Kvarken Archipelago, which includes the large islands Replot, Björkö and a large number of smaller islands. Most of it is belongs to the municipality of Korsholm. Most of the small islands are inhabited. The archipelago is smaller on the Swedish side of the region, and the islands have much steeper shores. The Kvarken region was historically important also, because mail was delivered across Kvarken when the sea was completely frozen from the Swedish to the Finnish coast. This mail route was used frequently during the period of Swedish rule.

In the group of islands in the “middle” of the Kvarken region, in Swedish called Valsörarna – Finnish Valassaaret, is a 36-metre-high (118 ft) lighthouse designed by Henry Lepaute who worked for Gustave Eiffel's engineering bureau. The structural similarity between the lighthouse (built in 1885) and the Eiffel tower (built in 1889) is quite obvious. The lighthouse is now automated as are most lighthouses in Finland.

Several attempts to cross the strait swimming have been made but cold water and currents have usually been insurmountable obstacle. The first successful attempt was carried out by Lennart Flygare, Pavio Grzelewski and Tore Klingberg, who on the 24:th of July 2018 swam from Valassaaret (Valsörarna) on the Finnish side to Holmögadd in Sweden. It took them 12 hours 2 minutes to cross the strait.


Langon may refer to:

Langon, Gironde, a commune in the Gironde department, France

Langon, Ille-et-Vilaine, a commune in the Ille-et-Vilaine department, France

Langon, Loir-et-Cher, a commune in the Loir-et-Cher department, France

Långön, an island in the Luleå archipelago in the Swedish part of the Bothnian Bay

Le Langon

Arrondissement of Langon

List of islands of Bothnian Bay

A list of islands of Bothnian Bay would include 4,001 islands if an island is defined as an area of land more than 20 square metres (220 sq ft) that is surrounded by water.Bothnian Bay (Swedish: Bottenviken, Finnish: Perämeri) is divided between northern Sweden and Finland.

The north of the bay contains a large archipelago area.

The largest island is Hailuoto, further south on the Finnish side.

In the winter the larger islands may be accessed via ice roads. Some of them are inhabited or have seasonal fishing villages used by people from the mainland.

Ostrobothnia (historical province)

Ostrobothnia, Swedish: Österbotten (literally "Eastern Bottom", "botten" deriving from Old Norse botn in the meaning of 'bay', and Latinized "bothnia"), Finnish: Pohjanmaa (literally "Bottom (low) lands") is a historical province comprising a large western and northern part of modern Finland (which was then the "eastern half" of Sweden). It is bounded by Karelia, Savonia, Tavastia and Satakunda in the south, the Bothnian Sea, Bothnian Bay and Swedish Västerbotten in the west, Laponia in the north and Russia in the east.


Oulujoki, Swedish: Ule älv (in modern Finnish literally "Oulu River", originally in old Northern Ostrobothnian dialect literally "Flood River", is a river in Oulu province, Finland.

Its origin is Oulujärvi and its watershed area covers a significant part of Kainuu region.

It flows into the Bothnian Bay at Oulu. Port of Oulu is located at the mouth of the river.


Simojoki is a river of Finland in the region of Lapland. It flows for 193 kilometres (120 mi) into the Bothnian Bay at Simo.

Stora Hamnskär

Stora Hamnskär is an island in the northeast of the Swedish sector of the Bothnian Bay, in the Haparanda archipelago.


Torne-Furö is an island in the northeast of the Swedish sector of the Bothnian Bay, in the Haparanda archipelago.


Töre (Kalix Language: te'or) is a locality situated in Kalix Municipality, Norrbotten County, Sweden with 1,099 inhabitants in 2010.Its harbour is the northernmost of the Bothnian Bay (and thus, of the Baltic Sea) that is accessible to commercial vessels. The European route E10 passes through Töre.

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