Seasonality of Airmass Pathways to Coastal Antarctica: Ramifications for Interpreting High-Resolution Ice Core Records

Understanding airmass pathways is critical for ice core interpretation, and the ability to determine the broadscale characteristics and seasonality of synoptic-scale flow using paleoclimate records offers great potential to improve the understanding of past atmospheric circulation. The dominant airmass pathways to a coastal Antarctic ice core site at the Whitehall Glacier in the Ross Sea are modeled using snowfall and high-resolution stable isotope data between 1979 and 2006, combined with back trajectories produced from both NCEP-NCAR and ECMWF Interim Re-Analysis (ERA-Interim) data. Back trajectories generated from both datasets produce comparable results. They show that high snowfall is associated with cyclonic airflow in the Ross Sea with a strong meridional component along the western Ross Sea coast. Over a 28-yr time frame, trajectories also reveal a clear distinction between flow paths associated with above-and below-average annual temperatures (high and low delta D) in the ice core record. In cold months (low delta D), when there is a strengthened trough of low pressure around the continent, synoptically driven incursions of marine air across West Antarctica and trajectories originating from coastal East Antarctica are dominant. Conversely, in warmer months (high delta D), airmass pathways are centered over the Ross Sea and the adjacent Southern Ocean. These trajectories are slower moving and are expected to draw marine moisture from high-latitude seasonally open oceans.