A model study on the relation between atmospheric boundary-layer dynamics and poleward atmospheric moisture transport in Antarctica

Abstract

A regional atmospheric model was used to study the relationship between atmospheric boundary-layerdynamics and moisture transport toward the Antarctic grounded ice sheet. The model was integratedfor a 14-yr period (1980—1993) using a grid spacing of 55 km. Re-analyses from the European centrefor medium-range weather forecasts were used to force the model from the lateral boundaries. Seasurface temperature and sea ice extent were prescribed from daily observations. It was found that theboundary layer responds passively to the large-scale circulation rather than being the driving force forthe meridional circulation and moisture advection toward the ice sheet. Moisture transport by the meancirculation is directed from the ice sheet toward the Southern Ocean and transient eddies are responsiblefor the moisture transport toward the ice sheet. Frequent interruption of the katabatic winds by passinglow-pressure systems characterise years with a large poleward moisture transport. Therefore there isa negative correlation between the annual mean poleward moisture transport and both the directionalconstancy and the southerly wind component in the boundary layer near the ice edge. A case study forJuly 1980 shows that the wind and the specific humidity in the middle and higher troposphere determinethe poleward atmospheric moisture transport in Wilkes Land and that the moisture advection in theboundary layer is insignificant in this region.