Observed trends in the river ice regimes of northwest Canada

Yukon air temperature trends have been observed to change over the last several decades with an increase in annual, summer and winter air temperatures, while changes in precipitation have not been consistent. An assessment of freeze-up and break-up dates indicates that the ice cover season is becoming shorter with delays in freeze-up and advances in break-up timing. Mid-winter break-up events and associated flooding have been observed for the first time. Break-up water level trends suggest that break-up severity is increasing. These changes cannot be definitely attributed to climate change as there is some evidence suggesting that teleconnections may be a factor. The observed changes have significant implications pertaining to public safety, and economic impacts on property and infrastructure, transportation networks and hydroelectric operations. Ice jams and associated backwater and surges also affect aquatic ecosystems through impacts on biological and chemical processes.