Impacts of meteoric sulfur in the Earth's atmosphere

A meteoric sulfur input function and a sulfur ion chemistry scheme have been incorporated into a chemistry‐climate model, in order to study the speciation of sulfur between the stratosphere and the thermosphere (~20–120 km) and the impact of the sulfur input from ablation of cosmic dust. The simulations have been compared to rocket observations of SO + between 85 and 110 km, MIPAS observations of SO 2 between 20 and 45 km, and stratospheric balloon‐borne measurements of H 2 SO 4 vapor and sulfate aerosol. These observations constrain the present‐day global flux of meteoric sulfur to ≤1.0 t S d −1 , i.e., 2 orders of magnitude smaller than the flux of S into the stratosphere from OCS photooxidation and explosive volcanic SO 2 injection. However, the meteoric sulfur flux is strongly focused into the polar vortices by the meridional circulation, and therefore, the contribution of SO 2 of meteoric origin to the polar upper stratosphere during winter is substantial (~ 30% at 50 km for a flux of 1.0 t S d −1 ). The Antarctic spring sulfate aerosol layer is found to be very sensitive to a moderate increase of the input rate of meteoric sulfur, showing a factor of 2 enhancement in total sulfate aerosol number density at 30 km for an input of 3.0 t S d −1 . The input rate estimate of 1.0 t S d −1 suggests an enrichment of sodium relative to sulfur of 2.7 ± 1.5 and is consistent with a total cosmic dust input rate of 44 t d −1 .