Ephemeral grounding on the Pine Island Ice Shelf, West Antarctica, from 2014 to 2023

Abstract. Ephemeral grounding sites form when ice shelves thin or relative sea level rises, causing pinning points to ground intermittently over tidal cycles. Vertical displacements derived from Sentinel-1A/B imagery reveal the ephemeral grounding history of the Pine Island Ice Shelf from 2014 to 2023. We found that the ephemeral grounding site disappeared after the ice shelf calved in 2020 and appeared again after October 2021. We conclude that basal melting directly influences the occurrence of ephemeral grounding at the central ice shelf. Ice shelf calving and atmospheric forcings, such as La Niña and the positive phase of the Antarctic Oscillation, are indirect factors that affect ephemeral grounding. We propose that the ephemeral grounding site at the central ice shelf may evolve into a final pinning point and may influence future ice shelf calving events. Further studies on ice shelf modeling are needed to understand the interaction between ephemeral grounding and rift propagation.