Inclusion of polar sea-ice emissions and sea-salt aerosol recycling of bromine into the global CAM-Chem chemistry-climate model

RAFAEL PEDRO FERNÁNDEZ; CARLOS ORDOÑEZ; DOUGLAS E. KINNISON; JEAN-FRANCOISE LAMARQUE; ALFONSO SAIZ-LOPEZ

Davos

Conferencia; Davos Atmosphere and Cryosphere Assembly (DACA-2013); 2013

International Association of Meteorology and Atmospheric Sciences (IAMAS)

A polar module considering full halogen chemistry and time-varying organic and inorganic halogen emissions into the polar marine boundary layer has been included in the global CAM-Chem chemistry climate model. The baseline CAM-Chem halogen setup includes natural sources of very short-lived (VSL) halocarbons from the oceans; reactive chlorine, bromine and iodine species; related photochemical, gas-phase and heterogeneous reactions, as well as wet and dry deposition for relevant species. The polar module considers sea-salt aerosol recycling of BrONO2, BrNO2 and HOBr and sea-ice emissions of Br2 and BrCl as result of recycling over the deposited snow over sea-ice. The contribution of blowing snow is also considered by means of an enhancement of the recycling efficiency over fresh sea-ice regions. The external brominated sources posses a 2-fold dependence on both solar zenith angle and local sea-ice cover. The time/sea-ice dependent local Br2 flux was scaled to reproduce observations of reactive bromine species over coastal Antarctica, resulting in an Antarctic mean sea-ice flux of ~200 Gg Br yr-1.Model results have been validated locally against boundary layer measurements of BrO performed at several Antarctic stations and with total and tropospheric BrO columns as reported from satellite platforms. Results show a good agreement, reproducing both the BrO seasonality and the springtime maximum peak. The tropospheric BrO cloud distributions is coincident with the Antarctic sea-ice covered regions as seen by satellites. Further work will quantify the potential of bromine and iodine chemistry to influence the oxidation capacity of the polar atmosphere.