Grant: Discovery Grants Program - Individual

Glaciers and ice sheets are declining worldwide due to climate change, contributing to global sea level rise and threatening freshwater security in many of the world's mountain regions. The rate of glacier mass loss has accelerated over the last 30 years, partly due to rising temperatures and partly due to positive feedbacks associated with glacier response to climate change. Within these positive feedbacks, albedo reductions are widely reported due to a variety of mechanisms, including increased biological and algal activity, dust loading from freshly deglaciated terrain, enhanced concentrations of impurities due to higher melt, and a greater temporal and spatial extent of exposed glacier ice, which has a lower albedo than seasonal snow or firn. In some regions, glaciers are also subject to more frequent wildfire deposition in recent years, which includes organic matter and black carbon that can contribute significantly to glacier `darkening'. Increased understanding of these different processes is important for improved projections of glacier and ice sheet response to climate change and to attribute the magnitude of glacier change that is due to climate forcing vs. feedbacks. Current models of glacier melt and mass balance use simplified approaches that don't explicitly include albedo or treat it as a constant. This neglects the seasonal evolution, interannual variability, and potential long-term trends in surface albedo that may be important to adequately capture glacier sensitivity to climate change. The over-simplification in melt models is largely a matter of complexity. The sources of impurities, their radiative properties, and processes of deposition, concentration, and `cleansing' from snowmelt- or rainfall-runoff likely differ across glacier sites and are not easily modelled. Parameterizations developed for one glacier are not likely transferable to different environments. The proposed research aims to study seasonal and interannual albedo variability, the chemical composition and concentrations of impurities in supraglacial snow, firn, and ice, and processes of impurity loading and flushing at glacier sites in western and Arctic Canada. Albedo monitoring through the melt season will be supplemented by surface sampling, modelling of atmospheric deposition, and the development of a numerical model of albedo evolution as a function of impurity content. These process models will be added to an existing model of glacier energy and mass balance developed by my research group, and the mass balance model is coupled with a model of glacier dynamics for simulation of glacier response to climate change under different climate scenarios. The long-term objective is to embed the glacier system model in high-resolution Earth system models for improved weather, climate, and hydrological predictions that better account for albedo feedbacks that are known to accelerate glacier and ice sheet melt.