Hydroclimate influences ice jam dynamics in southern Quebec watersheds through competing effects on ice cover resistance and dislocation forces

Climate change impacts river ice phenomena, influencing ice jam regimes. The complex formation of ice jams, which depends on a combination of morphological and hydrometeorological conditions, varies interannually and between watersheds. This research aims to identify the hydroclimatic conditions, associated with the balance between resisting and dislocating forces exerted on ice, that influence the spatiotemporal variability of seasonal ice jams in ten watersheds in southern Quebec, Canada. Generalized additive mixed-effects models were used to quantify the effect of potential hydroclimatic predictors on winter and spring number of ice jams at the watershed scale during the 2005–2018 period. Winter ice jams were not frequent (n = 114) and occurred only in a few locations. A higher number of winter ice jams was found to be associated with extreme seasonal hydroclimatic conditions, including higher peak rainfall or streamflow that dislocated the ice, while the role of snowfall remains uncertain in winter. The spring breakup favors a higher number of ice jams (n = 219), particularly in conjunction with high peak flows and sustained rainfall. The number of spring ice jams also increased in response to higher antecedent winter snowfall, hinting at the importance of white ice as a mechanism for the growth of river ice cover. In spring, hydroclimatic predictors alone offered greater explanatory potential (deviance explained = 34.5%) than in winter (deviance explained =