Synthetic Aperture Radar (SAR) revealed ice features of unknown origin in southwest Greenland’s ablation zone. Using SAR techniques, we identified low-backscatter areas with surface scattering, contrasting with surrounding high-backscatter areas from the subsurface. Our theory relates the low backscatter to residual liquid water in a weathering crust and the surrounding to bare glacier ice, suggesting that long-wavelength SAR could help monitor crust formation and near-surface meltwater storage.