GCM SIMULATIONS OF ATMOSPHERIC TRACERS IN THE POLAR LATITUDES - SOUTH-POLE (ANTARCTICA) AND SUMMIT (GREENLAND) CASES

Simulation results from two global atmospheric tracer/climate models i n the interior of the two major ice sheets at high northern and southe rn latitudes are presented and discussed. The models are based on two existing general circulation models (GCMs) of the atmosphere, compleme nted with tracer formulations (sources, transport, mixing, deposition, etc.). The seasonal and shorter term variability of desert dust, sea salt, Rn-222, Pb-210, and Be-7 has been studied at the South Pole in A ntarctica and at Summit in Greenland. This choice of tracers and test regions serves to focus on the interactions between atmospheric parame ters (e.g. the strong and durable surface inversions characteristic of the ice sheets) and tracers, and to limit other influences such as so urce variability and chemistry. Comparison with available observations is not consistently favorable. Short-term variability in the atmosphe re (Rn-222 and Pb-210) appears qualitatively reasonable. Seasonal cycl es are in some instances opposite to those observed, and mean depositi on is clearly too high. The coarseness of model resolution at the high latitudes and the difficulty of setting up efficient formulations for microphysical tracer processes (e.g. dry and wet deposition) are majo r sources of problems. If these obstacles are overcome, the combined t racer/climate modelling approach can offer quantitative interpretation of the observed features of atmospheric contaminants, or sensitive te sts of GCM simulated atmospheric circulation.