Sentinel-1 Detection of Ice Slabs on the Greenland Ice Sheet

Abstract

Abstract. Ice slabs are multi-meter thick layers of refrozen ice that limit meltwater storage in firn, leading to enhanced surface runoff and ice sheet mass loss. To date, ice slabs have largely been mapped using airborne ice-penetrating radar, which has limited spatial and temporal coverage. This makes it difficult to fully assess the current extent and continuity of ice slabs or to validate predictive models of ice slab evolution that are key to understanding their impact on Greenland’s surface mass balance. Here, for the first time, we map the extent of ice slabs and similar superimposed ice facies across the entire Greenland Ice Sheet at 500 m resolution using dual-polarization Sentinel-1 (S-1) synthetic aperture radar data collected in winter 2016–2017. The S-1 inferred ice slab extent is in excellent agreement with ice-penetrating radar ice slab detections from spring 2017, as well as the extent of the visible runoff zone as mapped from optical imagery. Our results show that ice slabs are nearly continuous around the entire margin of the ice sheet, including regions in Southwest Greenland where ice slabs have not been previously identified. The algorithm developed here also lays the groundwork for long-term monitoring of ice slab expansion with current and future C-band satellite systems and highlights the added value of future L-band missions for near-surface studies in Greenland.