Ice navigation in Arctic regions is mainly carried out in four areas:

1. The Baltic Sea, which is the only ice-bound sea where year-round traffic is maintained. Except for the Gulf of Bothnia, all main harbours are kept permanently open, even in hard winters; during mild winters, which on average occur once in five years, year-round traffic is maintained even there. This task is accomplished by using some 20 full-size (above 7 000 SHP) icebreakers (two from Denmark, one from West Germany, six to eight from USSR, seven from Finland, four from Sweden), as well as several hundred ice-strengthened cargo ships.