An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels, such as the icebreaking boats that were once used on the canals of the United Kingdom.
For a ship to be considered an icebreaker, it requires three traits most normal ships lack:
- a strengthened hull,
- an ice-clearing shape,
- power to push through sea ice
Icebreakers clear paths by pushing straight into frozen-over water or pack ice. The bending strength of sea ice is low enough that the ice breaks usually without a noticeable change in the vessel’s trim. In cases of very thick ice, an icebreaker can drive its bow onto the ice to break it under the weight of the ship.