A semienclosed brackish sea located in a humic zone, with a positive water balance relative to the adjacent ocean (the North Sea and the North Atlantic). The Baltic is connected to the North Sea by the Great Belt (70% of the water exchange), the Øresund (20% of the water exchange), and the Little Belt. The total area of the Baltic is 147,414 mi² (381,705 km²), its total volume 4982 mi³ (20,764 km³), and its average depth 181 ft (55.2 m). The greatest depth is 1510 ft (459 m), in the Landsort Deep.