Gulf of Bothnia Between Finland and Sweden64.4N 21.9E
The large body of water extending from the center to the lower part of this image is the Gulf of Bothnia, the northernmost arm of the Baltic Sea. It is situated between Finland’s west coast and Sweden’s east coast.
In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea. The gulf is 725 km (450 mi) long, 80–240 km (50-150 mi) wide and has an average depth of 60 m (200 ft, 33 fathoms). The maximum depth is 295 m (965 ft, 161 fathoms). The surface area is 117,000 km² (45,200 sq mi).
Into the gulf flow a number of rivers from both sides; consequently, a salinity gradient exists from north to south. In the south the water is the normal brackish water of the Baltic Sea, but in the north, in the Bothnian Bay, the salinity is very low. Being nearly fresh, the gulf is frozen over five months every year.