1Department of Earth Science, University of Siena, Via Laterina 8, 53100 Siena, Italy
2Institute for the Dynamics of Environmental Processes – CNR, University of Venice, Dorsoduro 2137, 30123 Venice, Italy
3Centre for Ice and Climate, Niels Bohr Institute, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
4School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
5Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, Dorsoduro 2137, 30123 Venice, Italy
6Laboratoire de Glaciologie et Géophysique de l'Environnement (UMR UJF/CNRS 5183), 54, Rue Molière, Domaine Universitaire, BP 96, 38402 Saint Martin d' Hères, France
Abstract. Sea ice is an integral part of the Earth's climate system because it affects planetary albedo, sea surface salinity, and the atmosphere-ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organo-iodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO) and iodine oxide (IO) decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE) ice core (159°11' E, 72°49' S, 2315 m a.s.l.) spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br−) is positively correlated with temperature and negatively correlated with sodium (Na). Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I−) and iodate (IO3−), peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial-interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.