Icebreaker

Icebreaker, vessel designed to make or keep open a navigable passage through ice. Icebreakers shatter the portion of the ice sheet directly ahead of them either by ramming the ice or by running up onto it and letting the weight of the ship break through the ice sheet; icebreakers are heavily built to withstand the shocks involved in these processes. Icebreakers are equipped with a heavy, usually overhanging bow, and armored sides. These ships also normally have both forward and aft propellers to provide greater maneuverability and to create suction under the ice to facilitate its breaking.

Icebreakers have been used mainly to clear channels during the winter in bodies of water such as the Great Lakes and the Baltic Sea, but in recent years they have been increasingly used in exploration of the Arctic and Antarctica. The former Union of Soviet Socialist Republics employed nuclear power in at least one icebreaker used in Arctic waters. In 1969 the oil tanker SS Manhattan was converted into an icebreaker and became the first commercial ship to travel from the Atlantic Ocean to northern Alaska via the frozen Northwest Passage.