Event-driven deposition of snow on the Antarctic Plateau: analyzing field measurements with SNOWPACK

Abstract

Abstract. Antarctic surface snow has been studied by means of continuous measurements and observations over a period of 3 yr at Dome C. Snow observations include solid deposits in form of precipitation, diamond dust, or hoar, snow temperatures at several depths, records of deposition and erosion on the surface, and snow profiles. Together with meteorological data from automatic weather stations, this forms a unique dataset of snow conditions on the Antarctic Plateau. Large differences in snow amounts and density exist between solid deposits measured 1 m above the surface and deposition at the surface. We used the snow-cover model SNOWPACK to simulate the snow-cover evolution for different deposition parameterizations. The main adaptation of the model described here is a new event-driven deposition scheme. The scheme assumes that snow is added to the snow cover permanently only during periods of strong winds. This assumption followed from the comparison between observations of solid deposits and daily records of changes in snow height: solid deposits could be observed on tables 1 m above the surface on 94 out of 235 days (40 %) while deposition at the surface occurred on 59 days (25 %) during the same period, but both happened concurrently on 33 days (14 %) only. This confirms that precipitation is not necessarily the driving force behind non-temporary snow height changes. A comparison of simulated snow height to stake farm measurements over 3 yr showed that we underestimate the total accumulation by at least 33 %, when the total snow deposition is constrained by the measurements of solid deposits on tables 1 m above the surface. During shorter time periods, however, we may miss over 50 % of the deposited mass. This suggests that the solid deposits measured above the surface and used to drive the model, even though comparable to ECMWF forecasts in its total magnitude, should be seen as a lower boundary. As a result of the new deposition mechanism, we found a good agreement between model results and measurements of snow temperatures and recorded snow profiles. In spite of the underestimated deposition, the results thus suggest that we can obtain quite realistic simulations of the Antarctic snow cover by the introduction of event-driven snow deposition.

Archival processes of the water stable isotope signal in East Antarctic ice cores

“…As a result, accumulation of snow at Dome C is not a homogeneous process affecting a flat surface, and the snow deposition is patchy and strongly dependant of the surface roughness (Groot Zwaaftink et al, 2013;Libois et al, 2014;Picard et al, 2016a). As a result, a small but significant contribution to the annual mass balance comes from sublimation/condensation directly at the surface .…”

Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

“…They used a simple snow evolution model to support their hypothesis, but these features of the seasonal cycle of SSA have never been simulated with a more detailed snowpack model such as Crocus (Brun et al, 1989(Brun et al, , 1992. In fact, such models are usually not fully adequate to polar environments (Dang et al, 1997;Groot Zwaaftink et al, 2013). Their semi-empirical parameterizations for e.g.…”

“…In addition, the few studies dedicated to the simulation of snow physical properties on the Antarctic Plateau focus on the evolution of the snowpack internal and surface temperatures (e.g. Brun et al, 2011;Fréville et al, 2014) or on punctual profiles (Dang et al, 1997;Groot Zwaaftink et al, 2013), rather than on temporal evolution of snow properties. Nevertheless, correctly simulating SSA evolution remains crucial to better understand the sensitivity of this region to future changes in precipitation and air temperature (Krinner et al, 2006).…”

Simulating the influence of snow surface processes on soil moisture dynamics and streamflow generation in an alpine catchment

“…For describing the high spatial variability in incoming and outgoing long-and short-wave radiation, including shadowing effects and the surface reflections of short-wave radiation, a detailed energy balance module is available (Michlmayr et al, 2008). An additional module considers drifting snow Mott et al, 2010), including sublimation processes (Groot Zwaaftink et al, 2013). These drifting snow modules are not used in this study, as the locations of the measurement sites are not prone to significant drifting snow effects, except for the Grossalp station.…”

“…The fully distributed Alpine3D model is typically applied for detailed studies of small scale surface processes in alpine catchments where snow plays an important role (Lehning et al, 2006;Mott et al, 2008;Groot Zwaaftink et al, 2013). In alpine terrain, considering the length scales less than a few 100 m is important as on these scales, wind drifts determine the snow accumulation and local topography heavily influences the energy balance via the slope aspect, angle and local shading.…”