Trends in the seasonal length and opening dates of a winter road in the western James Bay region, Ontario, Canada

In northern Canada, winter roads are essential for communities. The duration of the winter road season depends on particular meteorological conditions. In this study, we investigated whether there is a temporal relationship between seasonal weather trends and the historical opening dates of the James Bay Winter Road in Ontario’s Far North. The statistical significance of the temporal trends and their magnitude are determined by the Mann-Kendall test and the Theil-Sen method. Results showed that decreasing trends in the freezing degree-days (FDDs) are statistically significant, along with the statistically significant increasing trends of monthly averages of both T min and T mean during the winter months in the western James Bay region for the 1961–2014 period. However, there were no statistically significant linkages between opening dates and FDDs detected, perhaps due to the paucity of opening dates data, although early opening dates in the last 10 years may be the result of larger FDDs. The FDDs during the months of October through December were more closely linked to opening dates than FDDs that were calculated up the opening date (including January dates), suggesting the key role of preconditioning during late fall and early winter. The lowest FDDs for the months of October to December that resulted in a viable winter road were 380 degree-days (°C). This threshold can be potentially used as a lower threshold for winter roads.