Determination of accumulation rates from a shallow firn core of the West Antarctic Ice Sheet

In recent decades the West Antarctic Ice Sheet has experienced warming and glacial retreat. Despite receiving growing attention, knowledge of glacial dynamics in this region remains limited. Snow accumulation data is sparse and fails to capture true spatial variability. A shallow firn core, drilled at the triple ice divide between Pine Island Glacier, Institute Ice Stream, and Rutford Ice Stream, was glaciochemically analysed. Oxygen and hydrogen stable isotopes measured using Cavity Ringdown Spectroscopy exhibited seasonal oscillations. Ion concentrations measured with Ion Chromatography likewise varied seasonally, with maximum sodium, chloride and potassium concentrations in winter and maximum methanesulfonate, sulphate and nitrate concentrations in summer. Despite melt damage to the core during transport, it was possible to determine 18 annual layers and calculate an average accumulation rate of around 25 cm water equivalent per year (minimum 10.11, maximum 46.7 cm water equivalent). Analysis of a radargram from the site, with knowledge of this accumulation rate, indicated that reflectance horizons were not annual and that radar surveys with this frequency may not be suitable for gathering further snow accumulation data. The findings suggest that this triple ice divide is suited to glaciochemistry studies and that the retrieval of additional firn or ice cores, without melt influence, could contribute valuable data regarding the West Antarctic.