Abstract
Abstract. In this paper, we estimate the contribution of snowdrift sublimation (SUds) to the surface mass balance at Neumayer, located on the Ekström 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, SUds saturates and cools the air, limiting its own strength. We estimate that SUds 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. SUds 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.
Highlights
The surface mass balance (SMB), together with the flow of ice, determines the net mass change of the Antarctic ice sheet and the corresponding sea-level change (Vaughan et al, 1999; Rignot et al, 2008)
The snowdrift sublimation process depends on near-surface wind speed, temperature and relative humidity
SUds shows a clear annual cycle, and is stronger in winter than in summer, which is mainly related to the annual cycle in wind speed
Summary
The surface mass balance (SMB), together with the flow of ice, determines the net mass change of the Antarctic ice sheet and the corresponding sea-level change (Vaughan et al, 1999; Rignot et al, 2008). The specific SMB of a snow/ice surface (mm yr−1, Van de Berg et al, 2006) can be written as the annual sum of precipitation (P), sublimation at the surface (SU), runoff (RU) and erosion (∇·TRds) and sublimation (SUds) of drifting snow: SMB = (P − SU − RU − ∇ · TRds − SUds)dt (1) year. Assumed important on a local scale, earlier studies considered snowdrift sublimation to be a negligible term in the continent-wide surface mass budget (e.g., Turner et al, 1999). Different modelling studies demonstrated that sublimation due to snowdrift equals surface sublimation (King et al, 1996; Mann et al, 2000) or even exceeds surface sublimation at coastal and katabatic wind-controlled Antarctic sites (Bintanja, 2001a; Bintanja and Reijmer, 2001; Frezzotti et al, 2004).
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