Abstract
Abstract. A comprehensive understanding of the state and dynamics of the land cryosphere and associated sea level rise is not possible without taking into consideration the intrinsic timescales of the continental ice sheets. At the same time, the ice sheet mass balance is the result of seasonal variations in the meteorological conditions. Simulations of the coupled climate–ice-sheet system thus face the dilemma of skillfully resolving short-lived phenomena, while also being computationally fast enough to run over tens of thousands of years. As a possible solution, we present the BErgen Snow SImulator (BESSI), a surface energy and mass balance model that achieves computational efficiency while simulating all surface and internal fluxes of heat and mass explicitly, based on physical first principles. In its current configuration it covers most land areas of the Northern Hemisphere. Input data are daily values of surface air temperature, total precipitation, and shortwave radiation. The model is calibrated using present-day observations of Greenland firn temperature, cumulative Greenland mass changes, and monthly snow extent over the entire domain. The results of the calibrated simulations are then discussed. Finally, as a first application of the model and to illustrate its numerical efficiency, we present the results of a large ensemble of simulations to assess the model's sensitivity to variations in temperature and precipitation.
Highlights
Polar ice sheets are an important component of the earth system with far-reaching impacts on global climate
While the interpolation of time slice simulations is a viable alternative (e.g. Abe-Ouchi et al, 2013), climate models of reduced complexity provide a solution that foregoes the problematic temporal interpolation and achieves a more direct coupling (Bonelli et al, 2009; Robinson et al, 2011). The interface for this coupling between ice and climate is provided by surface mass balance (SMB) models of different complexities, ranging from empirical temperature index models, known as positive degree day (PDD) models (Reeh, 1991; Ohmura, 2001), to comprehensive physical energy balance models that resolve the snow surface at millimetre scale and with an evolving snow grain microstructure (Bartelt and Lehning, 2002)
In this study we present the BErgen Snow SImulator (BESSI), an efficient surface energy and mass balance model designed for use with coarse-resolution earth system models
Summary
Polar ice sheets are an important component of the earth system with far-reaching impacts on global climate. The loss of ice causes profound changes in the local atmospheric circulation, which feed back into the energy and mass balance (Merz et al, 2014a, b) This complexity calls for the bidirectional coupling of ice sheet and climate models. Abe-Ouchi et al, 2013), climate models of reduced complexity provide a solution that foregoes the problematic temporal interpolation and achieves a more direct coupling (Bonelli et al, 2009; Robinson et al, 2011) The interface for this coupling between ice and climate is provided by surface mass balance (SMB) models of different complexities, ranging from empirical temperature index models, known as positive degree day (PDD) models (Reeh, 1991; Ohmura, 2001), to comprehensive physical energy balance models that resolve the snow surface at millimetre scale and with an evolving snow grain microstructure (Bartelt and Lehning, 2002). We conclude our results in the final section, Sect. 6
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