Quantifying shifts in the magnitude and timing of glacier melt contributions to streamflow across the Canadian Cordillera

Abstract:

Glacial thinning and retreat in response to climate change increases discharge variability and drives seasonal shifts in peak flows in glacier-fed rivers, with critical hydrological and socio-ecological consequences for downstream catchments within and beyond the mountain water towers. Attempts to predict changes in glacier runoff due to deglaciation are typically conducted using sparse climate data and averaged at the larger basin scale. This often underrepresents the spatial and temporal variation of these changes occurring within high mountain catchments, particularly in sparsely populated regions.

Here we present the spatial and temporal variability of contemporary glacier runoff across the Canadian Cordillera, one of the major Water Towers of North America, and explore the variations in the magnitude and timing of peak water across western Canada. We employ a temperature-index model to obtain a first-order estimate of individual meltwater contributions from the 17,000+ glaciers in the Canadian Cordillera, using a combination of daily climate reanalysis data from the NCEP-NCAR and ERA5-Land Global Climate Reanalysis datasets for 2007 – 2019 and the Randolph Glacier Inventory version 6.0.

Sixteen index glaciers were selected due to the availability of published mass balance, melt, or melt factor data within the time period. These index glaciers range in latitude from 49^o – 60^o, and represent both continental and maritime climates, allowing for analysis that accounts for the spatial variability of the study region. For index glaciers lacking published melt factors, one was calculated using available mass balance and/or melt data along with the climate reanalysis data.

Modeled monthly glacier runoff for each basin was compared to streamflow data from Environment and Climate Change Canada’s Water Office in order to estimate the glacial contribution to runoff within each basin, as well as seasonal variations in these contributions. Our preliminary modeling results suggest that the variability in patterns of deglaciation across the Canadian Cordillera significantly modifies the magnitude and timing of peak water across the region, with implications for water security across western Canada in the near future.