A distributed, physically based snow melt and runoff model for alpine glaciers
Fox, A. M.
PublisherUniversity of Cambridge
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This thesis describes the development, testing and use of a distributed, physically based model of snow melt and runoff for alpine glaciers. A distributed version of a one-dimensional energy and mass balance snowpack model, SNTHERM, is coupled to a two-dimensional saturated flow model, MODFLOW, and is used to simulate meltwater production, vertical and lateral routing, storage and runoff across the temperate Haut Glacier d’Arolla, Switzerland at the beginning of the 2000 melt season. SNTHERM was first modified to incorporate an albedo scheme parameterised for this glacier, and to stimulate melt and runoff from glacier ice in additional to the seasonal snowpack. The performance of this 1-D model was tested against a suite of observations made on the glacier during spring 2000. It was found to reproduce observed rates of snowpack ablation and unsaturated meltwater movement through the snowpack well. The model was then used to investigate the relative contribution of the surface energy balance components to surface melt, and the delay in runoff and short-term storage of meltwater caused by unsaturated flow. A distributed version of SNTHERM was developed for use across the glacier. A digital elevation model (DEM) of the glacier surface and surrounding topography, together with data from a weather station located on the glacier, were used to calculate input variables of slope angle, aspect, shading and meteorological conditions across the glacier surface on a grid with a spatial resolution of 50 m. Initial snowpack depths and densities at the start of melt were determined from a snow survey conducted around the time of peak accumulation, with snow depth measurements interpolated onto a grid with the same resolution as the meteorological variables. SNTHERM was then run for each grid cell at an hourly resolution. Model performance was shown to be good when tested against repeat measurements of snow depth and albedo made along a glacier centreline stake network.