State and parameter estimation for Ronne Ice Shelf over 1992–2018

Abstract. Projections of sea level change require ice sheet models that reconcile observations with ice flow dynamics to constrain poorly observed processes and parameters. We use the Ice-sheet and Sea-level System Model (ISSM) to construct a state and parameter estimate of Ronne Ice Shelf (RIS) and its drainage basin from 1992 to 2018. We assimilate time-varying observations of surface velocity and elevation change to reconstruct a dynamically consistent model of time-mean basal friction and ice rheology, and sub-shelf basal melting rates. Relative to existing methods, we reduce uncertainty weighted root mean square errors (RMSE) in elevation change and velocity by 21.2 % and 43.6 %, respectively. Our inferred basal melt estimates capture spatio-temporal patterns driven by ocean currents at 5 km spatial resolution, and match monthly amplitudes 43.1 % closer to observations relative to existing estimates. Detrended mass change in the upstream grounded basin also correlates with Gravity Recovery and Climate Experiment (GRACE-GFZ) estimates (R = 0.754). This physically-consistent 26-year reconstruction provides a framework for applications to Antarctica and beyond, with implications for prognostic modeling and future sea level projections.