The Baltic Sea

The Baltic Sea is an ancient proglacial freshwater lake. It is an intracontinental and inland sea of 432,800 km², located in Northern Europe, and connected to the Atlantic Ocean by the North Sea.

The Gulf of Bosnia to the north and the Gulf of Finland to the east are part of the Baltic Sea. It communicates to the southwest, near Denmark, with the North Sea via the Kattegat and Skagerrak waterways.

The tide is very low (around 0.30 meters). and can sometimes be masked by temporary climatic variations.

What sets the Baltic Sea apart is its low salinity. It is much less saline than other seas, having only 10 g/l of salt, compared to 34.3/l for other bodies of salt water. The reason is simple: rivers contribute significantly, especially when the snow melts. Natural evaporation is barely equivalent to direct precipitation. Sea salinity follows the opposite rhythm to that of river salinity. In February, when the rivers are at their lowest, the sea reaches its highest salinity. In May, when the rivers are full of water from melting snow, salinity is at its lowest. In general, the waters in the east and on the sea surface are slightly salty (10‰ in the Danish Straits and 5‰ in the Gulf of Bothnia).

As for the waters of the Baltic Sea, they experience notable thermal variations. In summer, they reach 16°C in the south, while they stabilize around 12°C in the Gulf of Bothnia. In winter, it's a completely different story: pack ice covers the bottom of the gulfs of Bothnia and Finland, as well as many coasts, mainly the areas located to the north of the island of Gotland, off the coast of Stockholm.

This Baltic Sea owes its existence to several rivers which generously feed it. Among them are Göta Canal, Dalälven, Indalsälven, Ångermanälven, Umeälven, Skellefteälven, Luleälven, Kalixälven, Torne älv in Sweden, Kemijoki, Oulujoki, Kokemäenjoki, Kymijoki in Finland, the Neva, the Pregolia in Russia, the Narva and the Pärnu in Estonia, the Daugava, the Lielupe and the Venta in Latvia, as well as the Niemen in Lithuania, the Pasleka, the Vistula, the Wieprza and the Oder (Odra ) in Poland, and finally Uecker, Peene, Recknitz, Warnow, Schwentine and Trave in Germany.

The Baltic Sea is bordered by nine countries. To the northwest, Sweden, to the northeast, Finland, to the east, the three Baltic countries (Estonia, Latvia and Lithuania), as well as Russia in its regions of Kaliningrad and the Gulf of Finland. To the west is Denmark, and finally to the south, the coast is shared between Poland and Germany. As a result, some 85 million people live along the shores, privileged witnesses to this sea of a thousand lakeside splendors.

Coastal[2]  cities play a fundamental role and certain cities stand out for their population. In Russia, Saint Petersburg is a major metropolis with 4,700,000 city dwellers, followed by Kaliningrad 400,000. In Sweden, Stockholm is an emblematic city with its 743,703 inhabitants (and its agglomeration totalling 1,823,210 people), accompanied by Malmö which has 259,579 souls, as well as Visby, capital of the island of Gotland, more modest with its 23 000 inhabitants. In Poland, the tri-city (Gdańsk, Gdynia and Sopot) forms a dynamic agglomeration of 1,041,000 residents, while Kolobrzeg is home to 50,000 souls. In Finland, Helsinki shines with its 559,700 inhabitants (conurbation of 980,000), followed by Turku, proud of its 174,906 inhabitants, Oulu which has 130,126, Pori with its 76,000 residents and Kotka which welcomes 55,000 people. Riga, Latvia is a bustling city home to 760,000 people, as well as Liepāja (87,000 inhabitants) and Ventspils (44,000 inhabitants). Germany also contributes to this coastal panorama with Kiel and its 250,000 inhabitants, Lübeck with 216,100 inhabitants, and Rostock which has 212,700. Tallinn, in Estonia is a citadel city where a community of 387,200 inhabitants reside, while Klaipeda in Lithuania has 194,400 souls.​

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