Discrepancy in Satellite Altimetry Products Hinders Robust Retrieval of GIA Signals From Bedrock GNSS Data in Greenland

Isolating glacial isostatic adjustment (GIA) signals from Global Navigation Satellite System (GNSS) observations of vertical land motion (VLM) in Greenland requires removal of elastic solid Earth response to contemporary ice mass change. This elastic correction depends on ice‐surface elevation changes derived from satellite altimetry and firn corrections, which differ substantially across available products, yet these uncertainties are rarely accounted for in GNSS‐based GIA inferences. Here we quantify the sensitivity of elastic VLM at 53 Greenland stations to six contemporary ice‐loading products derived from altimetry and firn‐height corrections provided by three processing centers. Inter‐product spreads in elastic VLM predictions exceed 1 mm/yr at 34 stations and exceed 5 mm/yr at several sites in northwestern and southeastern Greenland. These regions also exhibit persistent underprediction of modeled uplift relative to GNSS observations, even after accounting for uncertainties associated with contemporary loading and contributions from peripheral glaciers and paleo and historical ice mass change.