Simulations of desert dust and sea-salt aerosols in Antarctica with a general circulation model of the atmosphere

A coupled aerosol/climate model, elaborated on the basis of a general circulation model of the atmosphere, is used to study the features of desert dust and sea-salt aerosols in the Antarctic region. Some of the observed seasonal characteristics of the two tracers are well simulated, and they are interpreted in terms of their relations with components of the atmospheric circulation. The model exhibits a strong influence of the boundary layer stability on the aerosols' vertical distributions near the surface. Observation at surface level may therefore be very misleading with respect to concentrations and seasonal variability higher in the atmosphere. An ice age experiment is run with the same aerosol/climate model, but fails to reproduce an expected large increase of dust and sea-salt concentrations in surface snow. The simulated enhancements of the production rates and atmospheric transport efficiency are weak. Changes in the distribution of the sources of dust, ignored in the experiment, could therefore have largely contributed to the last ice age dust increase. Sea-salt results suggest that the aerosol/climate model shortcomings are nevertheless not confined to source uncertainties, unless the complexity of the sources of sea-salt aerosol is also overlooked, for instance with respect to their relations with partial sea-ice cover.