Investigation of a wind-packing event in Queen Maud Land, Antarctica

Surface snow in polar and mountainous regions is often mobile and this mobility influences surface mass balance and isotopic composition before final deposition, which is poorly understood thus far. In December 2016 and January 2017, during a field campaign in Queen Maud Land, Antarctica, a snowfall and subsequent drifting snow events were recorded by meteorological and drifting snow stations. Associated small-scale topography changes and snow hardness changes were measured by terrestrial laser scanning and with a SnowMicroPen. The polar field measurements show that drifting snow is necessary for wind packing and thereby confirm previous findings from wind tunnel experiments. However, the snow hardness in Antarctica was significantly higher than what was achieved in the wind tunnel. This is most likely due to higher wind speeds and more intense saltation in the natural environment. As in the wind tunnel, no influence of time at a scale of days was observed on the hardness. This suggests that time and sintering are not the dominating processes in wind packing but that the impact compaction at the moment of deposition may be more important. Furthermore, it is quantitatively demonstrated how the reorganization of fresh snow into barchan dunes during subsequent drifting snow events is accompanied by significant increases in surface hardness at all locations on the dune. However, with the available data, the hardness variability on the dune could not be explained satisfactorily. In particular and unlike in the wind tunnel, there was no correlation between the hardness and the wind exposure parameter Sx. This is most likely because the measurements of hardness and the wind exposure situation were not simultaneous. This shows that highly temporally resolved snow depth data are necessary to investigate wind packing in more detail. These results form an important step in understanding how drifting snow links precipitation to deposition via snow hardening.