RESPONSE OF CANADIAN ROCKIES GLACIER HYDROLOGY TO CHANGING CLIMATE

Abstract

This thesis investigates the impact of snow and glaciers in mountain hydrology under changing climate conditions and glacier configurations in the Canadian Rockies, where a warming climate and glacier retreat cause concern about changes in mountain hydrology for water availability downstream. The general objectives of the study are (1) to model snow and glacier ablation and accumulation dynamics, (2) to determine how they influence high mountain hydrology, and (3) to improve hydrological modeling capacity in high mountain cold regions. The specific objectives are: (1) to develop a new model to estimate shortwave irradiance from temperature and humidity observations; (2) to include snow redistribution and the full energy and mass budget in a glacier hydrological modelling platform; (3) to apply the model to diagnose the individual and combined impacts of changes in climate and glacier mass on headwater hydrology. The thesis has four major parts. First, it describes the methodology used to produce meteorological data to force a hydrological model for the Peyto Glacier Research Basin (PGRB) in the Canadian Rockies. Second, it develops a new approach for estimating shortwave irradiance based on temperature and humidity observations that is suitable for snow and ice melt calculations for mountains and other cold regions around the world. Observations from thirty mostly mountain sites in South and North America, Europe and the Himalayas were used to evaluate existing algorithms and reanalysis products. The new algorithm, coupled to an existing extraterrestrial shortwave irradiance model, permitted more accurate estimation of shortwave irradiance from standard meteorological observations than was previously possible. The globally available reanalysis products also offer the potential for application to large-scale hydrological models. Third, the thesis develops a novel glacier hydrology model, developed within the Cold Regions Hydrological Model platform (CRHM), which is a physically based, integrated model capable of simulating the hydrology of both ice-covered and ice-free areas within a mountain basin. Fourth, the thesis focuses on diagnosing the impacts of climate change and changing glacier configuration on mountain headwater hydrology. The modelling results reveal that glacier retreat and ablation are due to the joint effect of a warming climate and an increase in ice exposure, which increase both seasonal melt and runoff. Increased streamflow is due to climate warming. However, the increases in melt and runoff are reduced somewhat by the reduction in glacial area. Such a modelling approach is important for diagnosing the hydrological responses from a glacierized basin in the context of climate change and variability and change in glacier configuration.