Climate change impacts on Peace River ice thickness and implications to ice-jam flooding of Peace-Athabasca Delta, Canada

Major ice jams forming in lower reaches of the Peace River during spring breakup have been identified as the main agents of flooding and replenishment of perched basins of the Peace?Athabasca Delta, one of the world?s largest inland freshwater deltas that supports a dynamic and valuable ecosystem. The paucity of ice jamming in the lower Peace River following construction of the Bennett Dam and the potential impacts of climate change have raised concerns regarding habitat degradation. One of the factors controlling ice-jam formation is the thickness of the winter ice cover, which may decrease in the future as a result of climatic warming, known to be most pronounced in northern parts of the globe and during the winter season. Using downscaled daily output from six Global Climate Models under two Representative Concentration Pathway scenarios, ice thickness is calculated for the years 1950 to 2100. Comparisons of monthly model-generated air temperatures and winter snowfall to historical data at nearby Fort Chipewyan indicate satisfactory agreement in terms of both magnitude and variability. Future projections show that under the highest emission scenario, average thickness decreases by about 0.2 m between the 1980s and the 2050s; and by an additional 0.1 m by the 2080s. Projected probability distributions of ice thickness point to increased incidence of thermal breakup, potentially reducing the alreadylow chances of ice-jam flooding. At the same time, a need for enhanced ice thickness monitoring is identified, aiming to develop a database of annual thickness values at selected sites within the lower reach of Peace River.