Weather, snow and ice: Hydrological and landscape changes in the Canadian Rockies headwaters

Abstract:

Glacierized mountains are witnessing strong changes in their streamflow generation processes, influencing their capacity to provide runoff to support downstream water resources and ecosystems. Shifting precipitation patterns, a warming climate, changing snow dynamics and retreating glaciers are occurring simultaneously, driven by complex physical feedbacks. To predict future hydrological behaviour in these glacierized catchments, a coarsely distributed, physically based cold regions process hydrological model including on and off-glacier process representations was used at the Peyto Glacier Research Basin, a 21 km² alpine catchment in the Canadian Rockies. The model was forced with bias-corrected outputs from a high-resolution pseudo-global warming Weather and Research Forecasting (WRF-PGW) simulation, for the 2000-2015 and 2085-2100 period under a business-as-usual scenario. The simulations show that the end-of-century increase in precipitation nearly compensates the decreased ice melt associated with almost complete deglaciation, resulting in a decrease of 7% in annual streamflow. However, the timing of streamflow is drastically advanced, with peak flow shifting from July to June, and August streamflow dropping by 67%. To examine the sensitivity of future hydrology to possible future post-glacial landscapes, the end-of-century simulations were run under a range of initial conditions. Specifically, vegetation change, proglacial lake formation, glacier extent and groundwater storage were varied. The high-resolution atmospheric modelling, unprecedented on and off-glacier process-representation in a physically based hydrological simulation and examination of sensitivity to future landscapes and deglaciations provides a comprehensive examination of the water future of a rapidly deglaciating high-mountain environment.