Numerical simulations and observations of the role of katabatic winds in the creation and maintenance of Scharffenbergbotnen blue ice area, Antarctica

Abstract. We model the role of katabatic winds in the formation and maintenance of a blue ice area in Scharffenbergbotnen valley, Antarctica, using the finite element code Elmer. The high-horizontal-resolution (50–200 m) numerical simulations of the local wind flow from katabatic wind fronts show high spatial variability in wind-impact patterns and good congruence between places with high near-surface wind speeds and the blue ice area. In addition we perform wind simulations on an altered glacier geometry that resembles the thicker ice cover at the Late Glacial Maximum (LGM). These simulations indicate that the pronounced spatial wind-impact patterns depend on present-day geometry and did not occur during the LGM. This leads to the conclusion that the formation of the inner blue ice area of the Scharffenbergbotnen valley started only after the lowering of the ice surface, i.e. after the LGM. Experiments with smoothed surface topography suggest that detailed positions of the high wind regions, and hence individual blue ice fields, may have varied as the ice sheet lowered. The simulation results obtained with the present-day geometry were fortuitously confirmed by the destruction of a field camp located in a high-wind-speed area and its subsequent redistribution to low-velocity areas. The experiments and the field observations are consistent with localized violent katabatic events rather than synoptic-scale storms, playing the dominant role in the formation and maintenance of this and perhaps many blue ice areas.