Recent changes in glaciers within the upper Yukon River basin and their contribution to discharge at Whitehorse

English Abstract:

Glaciers represent a significant source of stored water, and meltwater released during the spring through fall period provides runoff that can be regionally important. In the headwaters of the Yukon River above Whitehorse, YT, there is uncertainty on how much glaciers contribute to total discharge and how this will change in future under different scenarios of climate change. To begin to address these issues, we examined changes in glacier cover here based on remotely sensed imagery from various periods between 1948 and 2010, and estimated the current glacier volume by applying a volume–area scaling approach with locally derived parameters based on ice-thickness data collected in 2011. Glaciers in 2010 covered an area of 1002 km² and had an estimated total volume of 187 km³; between ~1990–2010 glacier cover declined by about 6% overall, while some individual glaciers lost over 25% or more of their area. We set up the HBV-EC hydrological model over the upper Yukon River basin and some smaller tributary basins using the Green Kenue software tool, and forced the model using extrapolated observations from nearby climatic stations. The model was able to reliably reproduce the magnitude and timing of river discharge along with local snow accumulation, melt, and glacier mass balance. By separating glacial and non-glacial sources of simulated runoff, we estimated that snow and ice melt from glaciers has supplied an average of about 20% of the annual flow volume of the Yukon River above Whitehorse in recent decades, with 30% of this as a result of the net mass loss (i.e. wastage) of glaciers. The model also indicates that the region’s largest glacier, the Llewellyn Glacier (433 km²), was the single most significant contributor of glacially-sourced water, highlighting the importance of this ice mass. Further work will consider future climate scenarios and glacier dynamic modelling to project impacts into the remainder of the 21^st century.