Basal reflectance and melt rates across the Ross Ice Shelf, Antarctica, from grounding line to ice shelf front

We present a 1000 km transect of Autonomous phase-sensitive Radio Echo Sounding (ApRES) measurements of ice thickness, basal reflection strength, basal melting, and ice-column deformation across the Ross Ice Shelf (RIS). Measurements were gathered across 32 repeat measurement sites and over five austral summers (2015-2020) connecting the grounding line with the distant ice shelf front. ApRES identifies varying basal reflection strength revealing a variety of basal conditions influenced by ice flow and by ice-ocean interaction at the ice base. Reflection strength is lower across the central RIS, characterised by higher strengths from major glaciers and ice streams and lower strengths in shear margins and suture zones. Strong reflections in the near-front and near-grounding line regions correspond with higher basal melt rates, up to 0.47 ± 0.02 m a^-1 in the north. Melting from atmospherically warmed surface water is shown to extend 150-170 km south of the RIS front. Melt rates up to 0.29 ± 0.03 m a^-1 and 0.15 ± 0.03 m a^-1 are observed near the grounding lines of the Whillans and Kamb Ice Stream, respectively. Our surface-based observations generally agree with the basal melt pattern provided by satellite-based methods but provide a distinctly smoother pattern.