Chemical and isotopic snow variability along the 1998 ITASE traverse from Terra Nova Bay to Dome C, East Antarctica

Abstract

In the framework of the PNRA-ITASE (Programma Nazionale di Ricerche in Antartide-International Trans-Antarctic Scientific Expedition) project, during the field season 1998/99, surface snow (1 m cores and pits) and shallow firn cores (10-50 m) were collected along a traverse from Terra Nova Bay (northern Victoria Land) to Dome C (East Antarctic ice sheet). Results of chemical, tritium and stable-isotope composition are presented here for the 1 m cores, some snow pits and the first 2 m of some shallow firn cores. The δ18O values show a regular trend with altitude, and the regression line between δ18O and surface temperature is δ18O = 0.99T (°C) - 0.67. Primary aerosol components such as Na+, Cl-, Ca2+, Mg2+ and K+ show high concentrations decreasing with increasing altitude in the first 250-350 km from the coast. At greater distances, concentrations of these species remain more constant. NO3- concentration shows an irregular profile with a progressive decreasing trend as altitude increases. Non-sea-salt (nss) SO42- concentration decreases up to about 250 km from the coast, increases 250-770 km from the coast and remains relatively constant in the most remote stations. Methanesulphonate (MSA concentration shows high variability. The MSA/nssSO42- ratio exhibits a decreasing trend 250-550 km from the coast. With increasing distance, the ratio shows moderate oscillations. nssCl- concentration shows a progressive increase as distance from the coast increases, in agreement with the increasing influence of HCl on the Cl- budget of the inland Antarctic atmosphere. Post-depositional re-emissions of Cl- and NO3- were found at stations characterized at the surface by long-term accumulation hiatus (wind crusts). The chemical-species distribution is consistent with the presence in the studied area of local and long-range transport processes, post-depositional effects and snow-accumulation variations observed along the traverse.