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Regional-scale distributed modelling of glacier meteorology and melt, southern Coast Mountains, Canada Shea, Joseph Michael


Spatially distributed regional scale models of glacier melt are required to assess the potential impacts of climate change on glacier response and proglacial streamflow. The objective of this study was to address the challenges associated with regional scale modelling of glacier melt, specifically by (1) developing methods for estimating regional fields of the meteorological variables required to run melt models, and (2) testing models with a range of complexity against observed snow and ice melt at four glaciers in the southern Coast Mountains, ranging in size from a small cirque glacier to a large valley glacier. Near-surface air temperature and humidity measured over four glaciers in the southern Coast Mountains of British Columbia were compared to ambient values estimated from a regional network of off-glacier weather stations. Systematic differences between measured and ambient conditions represent the effects of katabatic flow, and were modelled as a function of flow path length calculated from glacier digital elevation models. Near-surface wind speeds were classified as either katabatic or channelled, and were modelled based on Prandtl flow (for katabatic winds) or gradient wind speeds. Models for atmospheric transmissivity, snow and ice albedo, and incoming longwave radiation were tested and developed from observations of incident and reflected shortwave radiation and incoming longwave radiation. Data from a regional climate network were used to run a degree-day model, a radiation-indexed degree-day model, a simple energy balance model (including tuned parameters for turbulent exchange) and two full energy balance models (incorporating stability corrections, with and without corrections for katabatic effects on air temperature and humidity). Modelled melt was compared to mass balance measurements of seasonal snow and ice melt. Models were also compared based on their ability to predict date of snow disappearance, given an initial snowpack water equivalence. The degree-day model outperformed the simple energy balance and radiation-indexed degree-day approaches, while the full energy balance model without katabatic boundary layer corrections yielded the lowest errors.

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