Modelling snowdrift sublimation on an Antarctic ice shelf

In this paper, we estimate the contribution of snowdrift sublimation (SU(ds)) to the surface mass balance at Neumayer, located on the Ekstrom ice shelf in Eastern Antarctica. A single column version of the RACMO2-ANT model is used as a physical interpolation tool of high-quality radiosonde and surface measurements for a 15-yr period (1993-2007), and combined with a routine to calculate snowdrift sublimation and horizontal snow transport. The site is characterised by a relatively mild, wet and windy climate, so snowdrift is a common phenomenon. The modelled timing and frequency of snowdrift events compares well with observations. This is further illustrated by an additional simulation for Kohnen base, where the timing of snowdrift is realistic, although the modelled horizontal transport is overestimated. Snowdrift sublimation is mainly dependent on wind speed, but also on relative humidity and temperature. During high wind speeds, SU(ds) saturates and cools the air, limiting its own strength. We estimate that SU(ds) removes around 16%+/- 8% of the accumulated snow from the surface. The total sublimation more than triples when snowdrift is considered, although snowdrift sublimation limits sublimation at the surface. SU(ds) shows a strong seasonal cycle, as well as large inter-annual variability. This variability can be related to the variability of the atmospheric conditions in the surface layer.