Magnitude-order improvements to the measurement precision of Antarctic grounding zone dynamics using SAR satellite constellations

Evan L Kramer , Brent M Minchew

Glacier loss in Antarctica is strongly influenced by melt in the grounding zone, the transition between grounded and floating ice. Thwaites Glacier is a critical region, with 65 cm of sea-level-equivalent ice. A recent dataset tracks grounding line retreat for Thwaites and other Antarctic ice streams over 30 years. Despite this long-term record, significant uncertainty remains in predictions of ice sheet stability. An important source and diagnostic of this uncertainty is the poorly constrained response of grounding zones to high-frequency tidal forcing, driven by a lack of observations at the temporal resolution needed to capture short-timescale viscoelastic ice flexure. Commercial SAR constellations offer an opportunity to close this gap. We demonstrate this by identifying on-orbit InSAR-capable commercial SAR satellites suitable for ice shelf monitoring and propagating their orbits over four tidal beat cycles for the dominant constituents near Thwaites. The Cramer-Rao lower bounds on secular ice velocity and vertical tidal displacement reveal a two to three-fold improvement in measurement precision for an observation campaign using current commercial SAR satellites compared to the NISAR satellite. Further analysis shows that three orders of magnitude improvement in measurement precision can be achieved through the cross-satellite multi-plane TWIST InSAR architecture that enables sub-daily temporal baselines and breaks the K1 tidal aliasing barrier of one-day repeat sampling. Full inversions of synthetic surface displacement confirm the complete recovery of composite tidal forcing signals. The results offer a practical pathway for acquiring consistent observations that improve understanding of ice dynamics and projections of sea level rise.