Distribution of oxygen isotope ratios and snow accumulation rates in Wilhelm II Land, East Antarctica

Records of recent oxygen isotope ratios (δ18O) and accumulation rates are presented for the region of Wilhelm II Land, East Antarctica, between 78° and 93° E and from the coast to 2100 m elevation. These records were derived from analysis of 21 shallow firn cores collected during the 1997/98 and 1998/99 Australian National Antarctic Research Expeditions summer operations. The accumulation rates were determined using comparisons between detailed analyses of density, δ18O, hydrogen peroxide (H2O2) levels and electrical conductivity. The δ18O distribution follows an approximately linear relationship with snow surface elevation, with values from -22‰ near the coast to -32‰ towards 2000 m elevation. Accumulation-rate distribution does not display this simple relationship with topography. South of the West Ice Shelf the contours run parallel to lines of latitude (oblique to the coast and topography), with 400 kg m-2 a-1 towards the coast and 2000 m elevation, and a lower zone of 300 kg m-2 a-1 along an axis of 68.4° S. This pattern of accumulation is also evident along the Mirny-Vostok traverse route. Southwest of the West Ice Shelf the rate of accumulation drops gradually from 300 to 200 kg m-2 a-1 towards Lambert Glacier basin. Surface-snow redistribution and variations in accumulation rate cause variability in the clarity of core records, but several sites show sufficient stratigraphic preservation to suggest potential for extraction of extended palaeoenvironmental records through further drilling.