Numerical modeling of snow cover over polar ice sheets

Abstract

Crocus, a one-dimensional model of snow-cover stratigraphy and evolution, was developed by the Cenire d’Etudes de la Neige (CEN, Météo-France) and extensively validated in temperate Alpine conditions. We present here a study of Crocus’s ability to reproduce the characteristics of polar snow at the surface of ice sheets. Crocus simulates the evolution of the thermal and structural features of snow cover as a function of meteorological parameters at the snow-atmosphere interface. Only models can provide the necessary meteorologic at information with full ice-sheet spatial coverage, and with the temporal resolution needed by Crocus. Meteorological data have been extracted from the European Centre for Medium-Range Weather Forecasts (ECMWF) archives (analyses and short-term predictions), over the entire surface of Antarctica with a spatial resolution of 1.5°. Here, the ECMWF data from the South Pole are first compared with observations to check their quality. Then, 20 year simulations of snow covet are computed to test the sensitivity of Crocus to inaccuracies in the meteorological input. The simulated snow characteristics exhibit a strong sensitivity to air temperature, accumulation rate and the initial density of depositing snow. However, even with no major model adaptation to polar conditions, Crocus does reproduce a number of thermal and structural features of polar snow.