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

Abstract. Ephemeral grounding refers to the intermittent contact between an ice shelf and elevated seafloor features. The evolution of ephemeral grounding of an ice shelf can affect buttressing, alter ice flow dynamics, and influence ice shelf stability. Long-term observations of ephemeral grounding sites are crucial for understanding how thickness, basal conditions, and tidal interactions evolve over time. Vertical displacement data derived from Sentinel-1A/B imagery reveals the history of ephemeral grounding events at PIIS from 2014–2023. Our results suggest that ephemeral grounding at an ice rumple is modulated by the interaction between tidal forcing, ice shelf thickness, and evolving sub-ice-shelf geometry. A prominent central keel, shaped by inherited bed topography, promotes repeated contact with a submarine ridge. Landsat-8 images reveal that the rifts that cause the 2020 calving event may have formed due to the ice shelf grounding at the study site. These findings provide new insights into the mechanisms driving ephemeral grounding behaviour and highlight its potential role in modulating ice shelf stability.