Glacier Mass Balance and Hydrological Modeling with the WRF-Hydro/Glacier System

Abstract:

A detailed, physically based one dimensional, column snowpack model (Crocus)­ has been incorporated into the hydrological model WRF-Hydro. This allows for direct surface mass balance simulation of glaciers and subsequent modeling of meltwater discharge from glaciers. This new system (WRF-Hydro/Glacier) has been successfully evaluated over a glacier in Southern Norway (Hardangerjøkulen) where WRF model simulations were downscaled to 1 km grid spacing to provide meteorological forcing data to the WRF-Hydro/Glacier system at 100 m grid spacing. The WRF-Hydro/Glacier system reproduced the glacier surface winter/summer and net mass balance, snow depth, surface albedo and glacier runoff well compared to observations. The WRF-Hydro/Glacier system is only activated over a priori designated glacier areas. This glacier area is initialized with observed glacier thickness and assumed to be pure ice (with corresponding ice density). This allows for melt of the glacier to continue after all accumulated snow has melted. Furthermore, the simulation of surface albedo over the glacier is more realistic as surface albedo is represented by snow where there is accumulated snow, and glacier ice when all accumulated snow is melted. The improved estimation of albedo has an appreciable impact on the discharge from the glacier during late summer. The WRF-Hydro/Glacier system is being tested for incorporation within the NOAA National Water Model version 3.0 to run over South-Central Alaska at 1 km grid spacing. Along with evaluation of WRF-Hydro/Glacier over Hardangerjøkulen, we will show results from prototype National Water Model simulations over South-Central Alaska.