Spatial distribution and post-depositional diffusion of stable water isotopes in East Antarctica

Abstract. We have analysed the spatial variations in the mean stable water isotopic values, snow accumulation patterns and moisture sources along coast to inland transects in central Dronning Maud Land (cDML) and Princess Elizabeth Land (PEL) regions of East Antarctica. The δD and δ¹⁸O varied systematically from coastal to inland regions in cDML and PEL regions in response to the surface air temperature. While the elevation effect was not clearly visible, the isotope variations appeared to be associated with snow accumulation in cDML region and temperature in PEL region, which ultimately are associated with elevation. Further, a clear influence of topography on the snow accumulation was observed in cDML region. Such an observation was not recorded in PEL transect, apparently due to the strong snow redistribution in this region due to katabatic winds. The moisture sources to the study areas were identified using HYSPLIT backtrajectory calculations. The major sources of precipitation during summer arrived from the south Atlantic ocean in the cDML and the Indian Ocean in PEL. During winter, the sources of precipitation in cDML extended to Weddell Sea while in PEL, the sources extended up to 50° S in the Indian Ocean. In order to understand the post-depositional isotope diffusion processes in firn, a firn core which was drilled close to the cDML transect, five years after the snow core transect, was analysed in comparison with snow records. Our study showed a significant isotope amplitude diffusion with a diffusion length of 6 cm from the surface to 4 m depth in 5 years.