Amundsen Sea Embayment accumulation variability measured with global navigation satellite system interferometric reflectometry

Abstract. Understanding how water vapor is transported to Antarctica and leads to snowfall is crucial for improving ice-sheet mass balance projections and interpreting ice-core records. Global navigation satellite system (GNSS) receivers distributed across Antarctica to monitor ice velocity and solid Earth motion can be used to understand accumulation, ablation, and snow redistribution at the ice-sheet surface on sub-daily timescales. Here, we present a forward model for reflector height change between the GNSS antenna phase center and the snow surface and an inverse framework to determine accumulation rate and near-surface firn densification from the reflector height time series. We use this model to determine accumulation at three long-term GNSS sites located in the Amundsen Sea Embayment (ASE) and at an array of GNSS receivers deployed in the 2007–2008 and 2008–2009 austral summers. From the GNSS interferometric reflectometry (IR) accumulation time series, we find that extreme precipitation (i.e., the 90th percentile of accumulation events) dominates total precipitation and that extreme event frequency varies seasonally. We use our GNSS-IR accumulation time series together with reanalysis products to characterize the atmospheric conditions that promote extreme snowfall in the ASE. The blocking pressure systems that promote extreme accumulation on Thwaites Glacier are facilitated by tropical teleconnections, specifically convection that promotes Rossby wave trains from the western Pacific, Indian, and Atlantic oceans to the Amundsen and Bellingshausen seas.