The Northwest Passage (NWP) is the sea route between the Atlantic and Pacific oceans through the Arctic Ocean, along the northern coast of North America via waterways through the Canadian Arctic Archipelago. 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 or Northwestern Passages.
For centuries, European explorers sought a navigable passage as a possible trade route to Asia, but were blocked by ice. An ice-bound northern route was discovered in 1850 by the Irish explorer Robert McClure. Scotsman John Rae explored a more southerly area in 1854 through which Norwegian Roald Amundsen found a route, making the first complete passage in 1903–1906. Until 2009, the Arctic pack ice prevented regular marine shipping throughout most of the year. Arctic sea ice decline has rendered the waterways more navigable for ice navigation.
The contested sovereignty claims over the waters may complicate future shipping through the region: the Canadian government maintains that the Northwestern Passages are part of Canadian Internal Waters, but the United States and various European countries claim that they are an international strait and transit passage, allowing free and unencumbered passage. If, as has been claimed, parts of the eastern end of the Passage are barely 15 metres (49 ft) deep, the route's viability as a Euro-Asian shipping route is reduced. In 2016, a Chinese shipping line expressed a desire to make regular voyages of cargo ships using the passage to the eastern United States and Europe, after a successful passage by Nordic Orion of 73,500 tonnes deadweight tonnage in September 2013.[needs update] Fully loaded, Nordic Orion sat too deep in the water to sail through the Panama Canal.