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(by Karl Magnus Eger)



Sea ice conditions on the NWP are very complex. Observations of minimum sea-ice extent in the eastern and western regions of the NWP, illustrates the extraordinary inter-annual variability of the ice conditions. Although the trends in sea ice extent are negative in both regions over the period, the year to year variability is extreme and sometimes differs between the two regions. For example, one of the largest observed minimum extents in the western region (1969-2003) occurred in 1991, while in the eastern region the minimum sea ice extent that year was relatively low. While these observations indicate a recent overall decrease in the extent of sea ice in the NWP, the inter annual and spatial variability is not conducive to planning a reliable marine transportation system1 .

Although climate models for the Arctic, like the ACIA models, indicate a general retreat of sea ice throughout the 21 Century, the designated projection models provide no information on ice thickness (a critical factor for navigation). It is important to note that the horizontal resolution of these models (generally 200 kilometres) is not fine enough to take into account the complexity of the Canadian Archipelago. Hence there is more uncertainty when it comes to predicting future ice conditions in the NWP based solely on the output of climate models.

There are potentially seven routes through the Canadian Archipelago, of which three are considered as being practical for routine marine traffic. This includes: 1) M’Clure Strait, 2) Prince of Wales Strait and 3) Peel Sound. And the fourth which is less so: 4) Fury and Hecla Strait (see figure 4.7). Although much has been written and said about the impact of climate change and that an ice free Arctic will likely occur, it is important to note that such ice free conditions are not likely to occur prior to 2070. Even then, the Arctic will continue to be ice covered during the winter and large seasonal, annual and year to year variations will continue to occur. Ice conditions will continue to impede shipping through a major portion of the year. On the NWP, large quantities of drifting ice will continue despite Arctic warming and shipping through the Northwest Passage will remain risky.

Natural Conditions and Shipping through the M’Clure Strait

The first NWP-route passes through (from east to west): Davis Strait, Lancaster Sound, Barrow Strait, Viscount Melville Sound, M’Clure Strait, Beaufort Sea, Chukchi Sea, Bering Strait and Bering Sea. This is the shortest and deepest route with no draft restrictions, but the most difficult way due to the severe ice in the M’Clure Strait (120 kilometres wide at east end, 275 kilometres to the Beaufort Sea and depth at over 400 meters). Old, hard and dangerous ice is present most of the time which can seriously hamper progress and potentially damaging to even ice strengthened ships.

Projections done by the Canadian Arctic Shipping Assessment (CASA) anticipates that by 2020, the frequency of an open summer passage will increase2 . Even in those years when M’Clure Strait is passable there will be a risk of encountering old/multiyear ice. It is likely that this passage will remain ice packed most years. Since M’Clure Strait is considered to be the constraining point for this route, the historical minimum ice period data that is provided, indicates that significant multi-year ice is the norm.

The trend for the 1968-2006 periods indicates a gradual decrease in ice coverage. However, little change is expected before 20503 . This route, based on the Zone/Date System, is closed to vessels below Arctic Class 3 which can operate there between 20 August and 30 September (See Appendix, chapter 5). In a warm year the season could be extended to an estimated 10-15 days. During a cold year it would likely remain closed3 .

Fig. 4.6: Route Alternatives on the NWP


Source: CASA (2007)

Natural Conditions and Shipping through the Prince of Wales Strait

The second NWP-route passes through (from east to west): Davis Strait, Lancaster Sound, Barrow Strait, Viscount Melville Sound, Prince of Wales Strait, Amundsen Gulf, Beaufort Sea, Chukchi Sea, Bering Strait and Bering Sea. This is an easier deep draft alternate route which avoids severe ice in M’Clure Strait. However, the passage through the Prince of Wales strait (minimum width of less than 10 kilometres about half way through the strait, 230 kilometres long) has an average depth of 32 meters which tends to be the limiting factor.

Normally this strait is open during September, but there continues to be a threat of encountering some old ice. Projection based on certain changing climate indicators anticipates that by 2020 this route could be open for 8-10 weeks during some summers. Large inter annual variability will continue and icebreaker escort services will be required. The potential shipping season through this passage will continue to increase through 2050 but the threat of encountering old ice during most years will be significant.

There could be an increase in the presence of old ice as the decrease in land-fast ice in the western part of the Archipelago would allow more old ice from the Arctic Ocean to pass into channels between the islands. The historical minimum ice data that is provided indicates that significant multi-year ice is the norm. There is a stronger decreasing trend than that of M’Clure Strait for the same period (1968-2006). The “SS Manhattan” succeeded a westerly transit of this route in 1969. However, shipping will have to contend with significant amounts of old ice through the year 20504 .

Natural Conditions and Shipping through the Peel Sound

The third NWP-route passes through (from east to west): Davis Strait, Lancaster Sound, Barrow Strait, Peel Sound, Franklin Strait, Victoria Strait, Coronation Gulf, Amundsen Gulf, Beaufort Sea, Chukchi Sea, Bering Strait and Bering Sea. This is the longest transit and the most frequently used. Compared to sailing through: 1) James Ross Strait – Rae Strait – Simpson Strait, and through 2) Prince Regent Inlet – Bellot Strait, the sailing route through Peel sound is considered as the best option4 . However, navigation of this route is more challenging and the route is limited to ships having a draft of less than 10 metres.

Currently this route is passable from mid-August to mid-September. It is expected that the active shipping for this passage will continue to increase. However, old ice will continue to be a significant navigation hazard and there will continue to be large year-to-year variability. Data from the period of 1968-2006, for conditions at or near the ice minimum, indicates presence of old ice throughout the shipping season for the Peel Sound. The trend indicates a slight increase in the amount of ice presences3 . Historical data for the ice choke point of this route, which include the Larsen Sea and the Victoria Strait, shows a higher concentrations of old ice, which constrains access to the entrance to the Western Arctic Waterway of the Northwest Passage. Once again there has been a decreasing trend over the last 36 years. Even though this decreasing trend is expected to continue, significant amounts of old ice will persist through 2050 and caution will be required3 .

Natural Conditions and Shipping through the Fury and Hecla Strait

The fourth route, connecting the Arctic Bridge and the NWP, passes through Hudson Strait, Foxe Basin, Fury and Hecla Strait (160 kilometres long), Bellot Strait, Franklin Strait, Victoria Strait, Coronation Gulf, Amundsen Gulf, Beaufort Sea, Chukchi Sea, Bering Strait, Bering Sea. This route also has a draft limit of 10 metres.

It has had light ice years but it will likely remain difficult through 2020. Foxe Basin and the Gulf of Boothia can have significant amounts of ice through mid-August. Severe ice conditions at and in the vicinity of the western approaches to Fury and Hecla can be expected. Bellot Strait will generally be passable during the latter part of August and through-mid September but strong tidal currents will continue to be a factor for both the movement of ice and ships. By 2050 the frequency of ice free conditions throughout this route will increase. However, it is not likely that this route will be of interest to those shipping activities requiring reliable transit times as the probability of requiring an icebreaker escort is much higher than other NWP alternatives. The decreasing trend for this area is more pronounced than the other three routes, but it is clearly evident that significant amounts of old ice are likely to be present most years. Consequently Route 4 is going to be a challenge most years for a Type B vessel.

In addition to frequent congestion in Fury and Hecla Strait, there are potential ice problem in both Bellot Strait and Franklin Strait. Based on the Zone/Date System the season would begin 25 August and close 30 September. During a warm year the closing could be extended by almost 30 days. During a cold summer season it would likely remain impassable for most vessels3 . This route is not generally considered as a viable commercial passage for moderate to deep draft ships.

Natural Conditions and the Shipping Route to Churchill 

The port of Churchill is not a part of the NWP. However, the port of Churchill is an important destination of cargo from international markets, for instance, as the west endpoint of the Arctic Bridge. As well as an important destination point when considering intra-Arctic, Destination-Arctic and Transit route alternatives. The shipping route to Churchill is by the Labrador Sea, through Hudson Strait and then directly across the Bay to Churchill or alternatively just south of Southampton Island south-westward toward the western shoreline and then south into Churchill.

Usually the route through Hudson Strait opens around the beginning of July, but can be delayed by almost a month during colder years. Churchill and the western shore of Hudson Bay are generally open by the first week of July but can be delayed up to four weeks in colder years, or if the prevailing westerly winds are absent. Over the last decade this area has had generally lighter ice conditions than in the previous two decades with navigation conditions that would warrant an extension to the closing of the shipping season by 2-3 weeks. Climate change will likely increase the probability of a two to three week extension to the closing date, but it is unlikely that there will a significant impact on the opening date for this route through 2020. By 2050 the frequency of an earlier opening date will increase. Large inter annual and year to year variations will continue throughout the first half of the 21st century3 .


  •  1. ACIA (2005), Arctic Climate Impact Assessment, Cambridge University Press, Cambridge 2005
  •  2. CASA (2007), Canadian Arctic Shipping Assessment, By The Mainport Group Ltd. for Transport Canada, June 2007
  •  3. Canadian Ice Service: http://ice-glaces.ec.gc.ca/IceGraph/IceGraph-GraphdesGlaces.jsf
  •  4. AMSA (2009), Arctic Marine Shipping Assessment, Report, PAME, Arctic Council, Terragraphica, Anchorage, April 2009

Karl Magnus Eger, 2010, Natural Conditions and Navigation through the Northwest Passage, CHNL.©