Grounding line reconfiguration before and during lake drainage at Subglacial Lake Engelhardt, West Antarctica

Antarctica has an active subglacial hydrological system, with interconnected subglacial lakes fed by subglacial melt water. Subglacial hydrology can influence basal sliding, inject freshwater into the sub ice cavity and impact sediment transport and deposition which can stabilise grounding lines (GL). We use ICESat, ICESat-2 and CryoSat-2 altimetry to document the latest drainage of Subglacial Lake Engelhardt (SLE), which began in July 2021 and discharged >1.2 km3 of subglacial water into the Ross Ice Shelf cavity. We use RADARSAT-2 and TerraSAR-X interferometry to show the GL has retreated by 13 km downstream of the lake since the previous drainage in 2003-06. We evaluate the mechanism triggering SLE drainage, the cause of the observed GL retreat, and the interplay between subglacial hydrology and GL dynamics, including the growth of a grounded promontory protruding >27 km seaward from the GL.