Spatial and temporal trends in North American snow depth and relationships with streamflow and ablation

This dissertation examines secular trends in North American snow depth from 1960-2000. Results show substantial decreases in snow depth across much of the continent during the late winter and early spring, with the most pronounced negative trends in central Canada since the mid 1980s. These findings support previous research documenting decreased snow cover extent and duration using satellite observations since 1966. Decreased March snow depth is shown to be related to the increased frequency and intensity of snow ablation, suggesting an earlier onset of spring melt. A significant positive trend in the frequency of warmer air masses over central Canada during March is related to the increased frequency of ablation events. The change in frequency of warmer air masses is also associated with an increase in sensible heat advection over this region. As snowmelt runoff resulting from snow ablation is the major source of water for many major North American watersheds, the relationship between snow volume (snow depth over a unit area) and hydrology for five major North American watersheds is examined. Results indicate that snow volume provides important information on spring streamflow in the Yukon, Mackenzie and Saskatchewan Rivers.