Strong-wind events and their influence on the formation of snow dunes: observations from Kohnen station, Dronning Maud Land, Antarctica

Analyses of shallow cores obtained at the European Project for Ice Coring in Antarctica (EPICA) drilling site Kohnen station (75 degrees 00' S, 00 degrees 04' E; 2892 m a.s.l.) on the plateau of Dronning Maud Land reveal the presence of conserved snow dunes in the firn. In situ observations during three dune formation events in the 2005/06 austral summer at Kohnen station show that these periods were characterized by a phase of 2 or 3 days with snowdrift prior to dune formation which only occurred during high wind speeds of >10 m s(-1) at 2 m height caused by the influence of a low-pressure system. The dune surface coverage after a formation event varied between 5% and 15%, with a typical dune size of (4 +/- 2) m x (8 +/- 3) m, a maximum height of 0.2 +/- 0.1 m and a periodicity length of about 30 m. The mean density within a snow dune varied between 380 and 500 kg m(-3), whereas the mean density at the surrounding surface was 330 +/- 5 kg m(-3). The firn cores covering a time-span of 22 +/- 2 years reveal that approximately three to eight events per year occurred, during which snow dunes had been formed and were preserved in the urn.