Numerical modeling of the energy balance and the englacial temperature of Greenland Ice Sheet

The surface mass and energy balance of ice sheets links the response of ice sheets to atmospheric forcing. Historically, ice sheet model have relied on empirical parameterizations of these surface processes (e.g., positive degree days). More recently, global and regional climate models (e.g., RACKMO, MAR) have begun to incorporate sophisticated surface process models in an attempt to simulate ice sheet mass balance using a more physically based modeling approach. In this study we explore the limits of simple downscaling techniques to obtain the appropriate atmospheric forcing for surface energy balance models from global reanalysis products and evaluate the partition of uncertainties associated with downscaling and with various albedo, turbulent energy transfer and densification parameterizations. To accomplish this we have developed a simple physically based numerical model of the coupled radiation, snow and ice system has been developed. The model is a one-dimensional multi-layer snow and ice model that accounts for both the surface energy balance and subsurface heating to evaluate the energy and mass balance in the upper part of Greenland Ice Sheet and calculates the surface energy balance, temperature and density evolution in the uppermost part of ice. It is run over the full annual cycle, simulating melting, temperature and density profiles throughout the seasons. We assess uncertainty in the forcing by driving the model using downscaled ECMWF ERA-Interim reanalysis data and comparing this with forcing derived from in situ AWS stations from Greenland Climate Network Automatic Weather Stations (AWS) data and perform sensitivity studies using a suite of parameterizations for the albedo, turbulent fluxes and densification.