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Alison J. Cook, Jackie Dawson, Stephen E. L. Howell, Jean E. Holloway & Mike Brady, Communications Earth & EnvironmentThe map shows all ship tracks 1990–2018 (grey lines), and shipping routes (four different line colors) along the Northwest Passage. Map republished under CC By 4.0 license from Cook, A.J., Dawson, J., Howell, S.E.L. et al. Sea ice choke points reduce the length of the shipping season in the Northwest Passage. Commun Earth Environ 5, 362 (2024). https://doi.org/10.1038/s43247-024-01477-6. Ship tracks from Pizzolato et al.; updated. Land relief from the International Bathymetric Chart of the Arctic Ocean V3 (IBCAO).
From Harvard Kennedy School by Justin Barnes
With climate change accelerating and global interest in transiting the Passage rising, the unresolved debate over the Northwest Passage's legal status could have geopolitical implications for North America and maritime claims elsewhere in the world.
Arctic Initiative Predoctoral Research Fellow Justin Barnes produced this explainer ahead of participating in the course Arctic Future Pathfinders, a part of the One Ocean Expedition. Justin sailed aboard the S/S Statsraad Lehmkuhl from Nuuk, Greenland, into Baffin Bay, until ice conditions forced the expedition to cancel its planned voyage through the Northwest Passage. We are grateful to UiT the Arctic University of Norway for supporting Justin's participation in the course. Learn more about Arctic Future Pathfinders.
The Northwest Passage (NWP or Passage) is a series of maritime routes that run through Canada’s Arctic Archipelago. European explorers began to seek the Passage in the 16th century as part of a shortcut between the Atlantic and Pacific Oceans to enhance trade with Asia, but a navigable route eluded them until the early 20th century due to thick sea ice and challenging conditions. Meanwhile, Inuit have lived and successfully navigated the land, waters, and ice of the NWP for time immemorial.
In recent decades, technological advances paired with the impacts of climate change on sea ice have made transiting the NWP more feasible under certain conditions, renewing interest in the Passage for shipping, tourism, and access to Arctic resources. The NWP is often hailed as a potentially valuable shortcut between East Asia and Western Europe – shaving upwards of 7,000km (~3,480 nautical miles) off the route through the Panama Canal – but unreliable conditions, sparse infrastructure, and high risks make its real-world value far less certain.
With climate trends accelerating and global interest in the Arctic rising, interest in transiting the NWP for shipping or military purposes could reignite an unresolved – yet peacefully managed – debate between Canada and the United States on the legal status of the NWP.
As strategic interests converge in the Arctic, important questions about the future of the NWP could arise: Who controls - or should control - these waters? How will Indigenous rights and voices shape the rules of transit through Inuit homelands, including areas previously frozen for centuries? Can navigation of the Passage be made safe without sacrificing fragile ecosystems? The answers to these questions could have geopolitical implications for North America, as well as the maritime claims of the United States, Russia, and China elsewhere in the world.
Is it possible to navigate the Northwest Passage?
The NWP is a network of possible routes passing through Canada’s Arctic Archipelago. It is possible to navigate through the NWP during certain parts of the year, but all routes are relatively narrow, shallow in places, and seasonally choked with shifting sea ice and icebergs flowing from higher latitude areas. Uncharted sea lanes along with limited marine support or response infrastructure pose significant hazards for regular shipping through the Passage. Although the NWP has seen an overall increase in vessel traffic in its various sections, the challenging geography and conditions mean that even in summer, navigation requires caution, ice-capable vessels, and often icebreaker escort.
Historically Impassable: For most of history, multi-year sea ice made the Passage effectively non-navigable year-round to European vessels. Norwegian explorer Roald Amundsen took three years to make the first complete journey through the Passage, finishing in 1906. From 1906 to 2006, only 69 complete voyages transited the NWP. It was not until 1944 that the NWP was transited during a single navigation season. However, in recent decades, global warming has dramatically reduced sea ice coverage; in summer 2007, the NWP experienced a record retreat in sea ice that marked the first full opening of the Passage in recorded history.
Experts Are Divided: Scientific projections strongly support the idea that the NWP will be open for shipping every summer for a window of time by mid-century. More recent studies have pushed back on this claim, however, suggesting that reductions in sea ice do not necessarily equate to increased ship navigability. A key 2024 study indicates that, despite recent changes along individual sections of the NWP, the overall shipping season along the route has instead been shortening since 2007. According to this study, multi-year ice is flushed southward from high-latitude regions, maintaining “choke points” along certain route sections and adding to the difficulty of routine shipping through the NWP. Nonetheless, transits are increasing as ice conditions become more navigable: it took 100 years to accumulate 69 transits, then just the next 5 years (2006–2010) to log another 69 transits.
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NASA image created by Jesse Allen, using data obtained courtesy of the National Snow and Ice Data Center.This image shows sea ice around the Northwest Passage as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA’s Aqua satellite on August 22, 2007. McClure Strait, Parry Channel, Victoria Strait, and McClintock Channel (north of Victoria Strait), all appear nearly ice-free. North of McClure Strait, an area of sea ice remains, but it is fragmented.
Who's Using It? Destination vs. Trans-Arctic Navigation: An Arctic Council report found that the number of unique ships entering the NWP area increased by 44% from 2013 – 2019 and the distance sailed by vessels increased by 107%. Most vessels operating in the NWP are re-supply cargo ships servicing communities and mines, local and commercial fishing vessels, tankers, tourist vessels (including pleasure craft), and military/research vessels, with pleasure crafts being the fastest growing sector by far. The majority of commercial ships operating in the NWP during this period were Canadian. The Scott Polar Research Institute’s record of “complete” transits by vessels that used the NWP to travel between the Atlantic and Pacific Oceans also shows a steady increase, with all-time highs reached in 2023 (41 transits) and 2024 (38 transits). Between 2020 – 2024, 117 “complete” transits took place, made up of 48 (41%) yachts or other private vessels, 39 (30%) commercial vessels, 28 (23%) passenger ships, and 2 (1.7%) research or survey vessels. Although the NWP has experienced an increase in both destination and trans-Arctic passages, both pale in comparison to the 36-38 ships that pass through the Panama Canal per day under normal operation.
Risky Business: The Passage is still a risky and uncertain corridor for regular commercial shipping due to unpredictable ice conditions, a lack of deep sea ports, poor charting relative to other passages, and high insurance costs. Comparisons to the Northern Sea Route, another passage along the Arctic coast of Russia, have made the case that the NWP is much more constrained and unpredictable. Shipping companies have been cautious, and few commercial ships (47) and passenger vessels (91) have ever attempted full transits. The overall increase in vessel traffic in the NWP could lead to an increase in accidents requiring an environmental and rescue response. A lack of support infrastructure and an overall decrease in highly strengthened ships operating in the Canadian Arctic more broadly exacerbates these risks.
Captain Wayne Duffet, Commander Corey Gleason, and Commander Michele Tessier of the Royal Canadian Navy explain the difficulties of operating in the harsh ice conditions of the Canadian Arctic.
The legal status of the Northwest Passage: International strait or internal waters of Canada and Inuit Nunangat?
The international legal status of the Northwest Passage remains unresolved. Canada maintains that the Passage lies within its internal waters, under full Canadian sovereignty. Whereas the United States has taken the position that it is an international strait, through which foreign vessels can transit freely without Canadian consent.
The U.S. Argument for an International Strait: The United States asserts that the NWP qualifies as an international strait under Article 37 of the United Nations Convention on the Law of the Sea (UNCLOS), arguing that the NWP connects the Atlantic and Pacific Oceans and thus must be treated as a strait with a right of transit passage for all nations. The U.S. position on international straits is that they do not depend on a waterway being ice-free or frequently used historically – if a passage connects two high seas/exclusive economic zone (EEZ) areas, it can be considered an international strait subject to transit rights. The United States has never accepted Canada’s historic waters claim and regularly reasserts that the Passage is an international waterway.
The Canadian Argument for Internal Waters: Canada’s position is that the NWP lies entirely within Canada’s territorial waters. In 1985, Canada drew baselines around its Arctic Archipelago that define the outer limit of Canada’s historic internal waters. Canada asserts that it has full sovereignty over the “historic internal waters” winding through the islands of the Arctic Archipelago that is based on historical exploration and effective governance of these waters. As part of this assertion, Canadian officials have emphasized that from time immemorial Inuit have used and occupied the waters and sea ice between these islands “as they have used and occupied the land,” which for Canada, strengthens its historic title.
Inuit – Historic Use and Indigenous Rights: Inuit in Canada emphasize that the NWP is inseparable from their homeland, Inuit Nunangat, and must not be regarded purely as an external or strategic waterway, necessitating legal recognition of Indigenous rights and Inuit-led co management in any governance or policy framework. Inuit assert that their continuous presence for millennia and relationship with the local environment establishes both ancestral rights and stewardship responsibilities. The Inuit Circumpolar Council (ICC) Canada has argued that the U.S. position is inconsistent with the United Nations Declaration on the Rights of Indigenous Peoples (UNDRIP), noting that Inuit have rights to the lands, waters, and ice they have “traditionally owned, occupied or otherwise used or acquired.” This position is based on treaties and constructive agreements between Inuit and the Government of Canada, including the Nunavut Land Claims Agreement among others, that “recognize both Inuit sovereignty and Canadian sovereignty over the Arctic, including the Northwest Passage.” The Inuit Tapiriit Kanatami’s (the national representation organization for Inuit in Canada) Nilliajut 2 report asserts that Inuit voices are essential in defining the Passage’s future, stating that “we must be consulted before any decisions are made and any research is done.”
Perspectives from Russia and China: Russia’s interpretation mirrors Canada's, which is central to its sovereign control over the Northern Sea Route. Parallels have also been made between the NWP debate and China’s claim that the Qiongzhou Strait in the South China Sea is part of China’s internal waters, an assertion that the United States formally rejects. However, the Chinese government has never explicitly recognized the Canadian position. China, as a self-proclaimed “near-Arctic state,” has been more cautious and ambiguous, formally respecting Arctic states’ jurisdiction but emphasizing international law and freedom of navigation as it pursues its “Polar Silk Road” across the Arctic.
Agree to Disagree? The U.S.-Canada 1988 Arctic Cooperation Agreement: Two diplomatic incidents - the transiting of the NWP by the U.S. tanker SS Manhattan in 1969 and the U.S. Coast Guard icebreaker Polar Sea in 1985 - sparked strong public and political reactions in Canada. In both instances, despite important contexts unique to each case, the United States did not formally request permission but coordinated with Canada throughout the passage.
To manage tensions, the two countries signed the 1988 Arctic Cooperation Agreement: the United States would notify Canada of voyages of American icebreakers conducting research while transiting the NWP without officially asking for permission, and Canada would grant consent routinely without the United States officially asking for it. The deal preserved both sides’ legal positions while serving as a model for Ottawa and Washington to manage the NWP disagreement. This has been described as a pragmatic “agree-to-disagree” framework that eased tensions but left the underlying legal debate unresolved.
For now, the official line on both sides remains unchanged. Some observers have proposed that the two nations find a mutually beneficial resolution (for instance, a joint management regime that acknowledges Canadian legal control while assuring innocent passage to foreign ships). Other experts feel that any negotiation could risk one side’s core interests, and that the existing compromise, ambiguous as it is, has worked without major incident. This longstanding debate has been generally well-managed, and so far, poses “no acute sovereignty or security concerns to Canada.”
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AP Photo/David GoldmanThe Finnish icebreaker MSV Nordica, pushes through floating sea ice on the Victoria Strait while traversing the Northwest Passage in the Canadian Arctic Archipelago, Friday, July 21, 2017. The voyage was registered with Canadian authorities.
AP Photo/David GoldmanThe Finnish icebreaker MSV Nordica, pushes through floating sea ice on the Victoria Strait while traversing the Northwest Passage in the Canadian Arctic Archipelago, Friday, July 21, 2017. The voyage was registered with Canadian authorities.
Why does the legal status of the Northwest Passage matter?
Geopolitical Implications: Both the United States and Canada want to avoid creating unwanted precedents. For example, a concession by the United States in the NWP could undermine the U.S. stance against excessive maritime claims elsewhere in the world, as well as its own freedom of navigation in other strategically important regions. The United States maintains an active Freedom of Navigation Operations (FONOPs) program to contest such claims and preserve global maritime access.
North American Security: Some analysts note that unregulated access by potentially any nation’s vessels (including strategic rivals) could harm North American security. If the Passage is considered an international strait, there would also be an international air corridor above each of its routes. Foreign military or criminal vessels and/or aircraft might attempt to use it to transit through North America’s northern flank – a scenario that would be a major concern for both the United States and Canada. If Canada’s internal-waters claim were accepted, Canada could legally bar or strictly control foreign vessels and aircraft, preventing, for example, Russian or Chinese naval use of the Passage – a result the United States might quietly appreciate.
Environmental Protection: The possibility for increased shipping raises concerns over the impacts of oil spills and pollution on Arctic ecosystems. If the NWP is recognized as Canadian internal waters, Canada could continue to enforce its domestic laws and environmental standards. However, if it is instead treated as an international strait, Canada could only impose internationally approved environmental standards under UNCLOS, which are less strict than Canadian rules in certain areas. This distinction carries consequences for managing oil spill risks, protecting Arctic ecosystems, and safeguarding the food security of Indigenous communities that rely on marine resources.
Respect for Indigenous Rights: Deeming the NWP an international strait would have deep implications for Inuit, who hold legal agreements with the Government of Canada regarding co-management and self-government. It is unclear in this case how the respect for these rights could be negotiated into a multilateral agreement about the NWP, but a legal outcome that bypasses Indigenous input would undermine modern land claims agreements and UNDRIP.
Search and Rescue (SAR): SAR challenges in the NWP, like the North American Arctic broadly, result from minimal infrastructure, limited communication coverage, and harsh weather conditions. Long distances between communities, unpredictable sea ice conditions, and a lack of nearby ports or airfields mean that emergency response times can be dangerously slow. Currently, cooperative frameworks like the 2011 Arctic Search and Rescue Agreement mitigate these concerns, with Canada’s zone of responsibility covering the passages through its Archipelago while stipulating that these boundaries do not affect sovereignty claims. This arrangement ensures that regardless of the NWP’s legal status, Canada and its Arctic partners can effectively cooperate on SAR operations in the region. However, if the NWP is deemed an international strait, Canada could not deny vessels that do not meet its domestic standards, potentially straining Canada’s already limited capacity to respond to incidents.
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Peter Prokosch via GRID-ArendalAn Inuit hunter captures a ring seal in Mittimatalik (Pond Inlet), Nunavut, Canada, where seal hunting on the sea ice is an important part of life. Inuit in Canada emphasize that the Northwest Passage is inseparable from their homeland. Increased ship traffic through the Northwest Passage could raise the risk of pollution and endanger the marine resources on which Indigenous communities rely.
Peter Prokosch via GRID-ArendalAn Inuit hunter captures a ring seal in Mittimatalik (Pond Inlet), Nunavut, Canada, where seal hunting on the sea ice is an important part of life. Inuit in Canada emphasize that the Northwest Passage is inseparable from their homeland. Increased ship traffic through the Northwest Passage could raise the risk of pollution and endanger the marine resources on which Indigenous communities rely.
Conclusion
At this time, both the United States and Canada “agree to disagree” on the status of the NWP. Looking forward, how the Passage is managed in the future will depend on the rate of change and whether collaborative frameworks continue to exist to manage different perspectives. Whether the NWP becomes a space of peaceful governance or contested access will depend on proactive diplomacy, and would benefit from a commitment to Indigenous co-management and continued investment in environmental protection and maritime safety.
Rockhopper penguin (Eudyptes chrysocome moseleyi) Gough Island, South Atlantic, Islands in the southern oceans
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Imagery of the Clipper Endeavour wreckage, discovered more than seven decades after the aircraft disappeared. (Image courtesy: Air/Sea Heritage Foundation and Deep Sea Vision)