Year-round record of surface ozone at coastal (Dumont d'Urville) and inland (Concordia) sites in East Antarctica

Abstract : Surface ozone is measured since 2004 at the coastal East Antarctic station of Dumont d'Urville (DDU) and since 2007 at the Concordia station located on the high East Antarctic plateau. Ozone levels at Concordia reach a maximum of 35 ppbv in July and a minimum of 21 ppbv in February. From November to January, sudden increases of the ozone level, up to 15-20 ppbv above average, often take place. They are attributed to local photochemical ozone production as previously seen at the South Pole. The detailed examination of the diurnal ozone record in summer at Concordia suggests a local photochemical ozone production of around 0.2 ppbv h−1 during the morning. The ozone record at DDU exhibits a maximum of 35 ppbv in July and a minimum of 18 ppbv in January. Mixing ratios at DDU are always higher than those at Neumayer (NM), another coastal Antarctic station. A noticeable difference in the ozone records at the two coastal sites lies in the larger ozone depletion events occurring from July to September at NM compared to DDU, likely due to stronger BrO episodes in relation with a larger sea ice coverage offshore that site. A second difference is the large day-to-day fluctuations which are observed from November to January at DDU but not at NM. That is attributed to a stronger impact at DDU than at NM of air masses coming from the Antarctic plateau. The consequences of such a high oxidizing property of the atmosphere over East Antarctica are discussed with regard to the dimethylsulfide (DMS) chemistry.