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

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