The sulfur cycle at high-southern latitudes in the LMD-ZT General Circulation Model

This modeling study was motivated by the recent publication of year-round records ofdimethylsulfide (DMS) and dimethylsulfoxide (DMSO) in Antarctica, completing theavailable series of sulfate and methanesulfonic acid (MSA). Sulfur chemistry has beenincorporated in the Laboratoire de Me´te´orologie Dynamique-Zoom Tracers (LMD-ZT)Atmospheric General Circulation Model (AGCM), with high-resolution and improvedphysics at high-southern latitudes. The model predicts the concentration of six major sulfurspecies through emissions, transport, wet and dry deposition, and chemistry in both gas andaqueous phases. Model results are broadly realistic when compared with measurements inair and snow or ice, as well as to results of other modeling studies, at high- and middlesouthernlatitudes. Atmospheric MSA concentrations are underestimated and DMSOconcentrations are overestimated in summer, reflecting the lack of a DMSO heterogeneoussink leading to MSA. Experiments with various recently published estimates of the rateof this sink are reported. Although not corrected in this work, other defects are identifiedand discussed: DMS concentrations are underestimated in winter, MSA and non-sea-salt(nss) sulfate concentrations may be underestimated at the South Pole, the depositionscheme used in the model may not be adapted to polar regions, and the model does notadequately reproduces interannual variability. Oceanic DMS sources have a majorcontribution to the variability of sulfur in these regions. The model results suggest that in alarge part of central Antarctica ground-level atmospheric DMS concentrations are larger inwinter than in summer. At high-southern latitudes, high loads of DMS and DMSO arefound and the main chemical sink of sulfur dioxide (SO2) is aqueous oxidation by ozone(O3), whereas oxidation by hydrogen peroxide (H2O2) dominates at the global scale. Acomprehensive modeled sulfur budget of Antarctica is provided