Subsidence, or the sinking of land, threatens the U.S. Gulf Coast, where millions face growing flood risks from sea-level rise. Measuring the subsidence is essential for coastal planning and climate adaptation. Satellite radar (InSAR) is widely used to measure subsidence, but studies often disagree. Comparing two recent datasets, we found widespread disagreements except in dense urban areas. Decision makers should use coastal InSAR products with caution until these discrepancies are resolved.

Antarctic ice shelves help slow ice flow into the ocean, but their stability depends partly on the upper firn layer. Air in firn affects how much meltwater can be stored, while grain size helps describe firn structure. We combined fifteen years of satellite radar data with physical models to estimate these properties across Antarctic ice shelves. Our results provide a new way to monitor conditions linked to meltwater build-up and possible instability.