Ice navigation in the context of Ymer (1976 icebreaker)

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, and the power to push through sea ice.

The Northwest Passage (NWP) is the sea lane between the Atlantic and Pacific oceans through the Arctic Ocean, near the northern coast of North America via waterways through the Arctic Archipelago of Canada. The eastern route along the Arctic coasts of Norway and Siberia is accordingly called the Northeast Passage (NEP).The various islands of the archipelago are separated from one another and from mainland Canada by a series of Arctic waterways collectively known as the Northwest Passages, Northwestern Passages or the Canadian Internal Waters. In British English it is often spelled North-west Passage.

For centuries, European explorers, beginning with Christopher Columbus in 1492, sought a navigable passage as a possible trade route to Asia, but were blocked by North, Central, and South America; by ice, or by rough waters (e.g. Tierra del Fuego). An ice-bound northern route was discovered in 1850 by the Irish explorer Robert McClure, whose expedition completed the passage by hauling sledges. Scotsman John Rae explored a more southerly area in 1854 through which Norwegian Roald Amundsen made the first complete passage entirely by ship in 1903–1906. Until 2009, the Arctic pack ice prevented regular marine shipping throughout most of the year. Arctic sea ice decline, linked primarily to climate change, has rendered the waterways more navigable for ice navigation.