Enabling Subglacial Geodesy Through High-Precision Radar Sounding and GNSS Time Series Observations

Our capacity to estimate vertical motion of the solid Earth with high precision has transformed our understanding of a variety of Earth processes, including mantle dynamics, plate tectonics, volcanic hazards, earthquake rupture, and surface-water balance. Geodetic observations of solid Earth deformation were first achieved on land with conventional surveying techniques, global navigation satellite system (GNSS) deployment, and satellite remote sensing, then expanded to the global ocean with seafloor geodesy techniques like GNSS-Acoustic (GNSS-A) experiments and fiber-optic sensing. Although we can now assess solid Earth deformation nearly everywhere on Earth, we still have not achieved subglacial geodesy: directly observing uplift or subsidence beneath glaciers and ice sheets. Due to decreasing ice mass, we expect high rates of uplift beneath Earth’s ice masses (i.e., glacial isostatic adjustment, or GIA), but available GNSS observations from exposed rock on the periphery of the Greenland and Antarctic ice sheets suggest uplift rates can be highly variable on 10s of km length scales. Recent observational and modeling studies have suggested that GIA could provide a critical stabilizing feedback for ice-sheet mass loss on decadal and centennial timescales, therefore developing and deploying the technology needed for subglacial geodesy is critical for accurate projections of sea level change, particularly in Antarctica where areas of exposed bedrock are rare. To address this challenge, we present a suite of combined radar sounding / GNSS experiments and systems under development to constrain uplift rates beneath both slow-flowing (< 10 m/yr) and fast-flowing ( > 10 m/yr) ice. We also discuss a range of related systems and experiments under development to constrain and correct for potentially confounding firn compaction signals.