Parker Ice Tongue collapse, Antarctica, triggered by loss of stabilizing land-fast sea ice

After a likely multi-century period of intermittent calving, the full length of Parker Ice Tongue (18 km or 41 km2), calved in March 2020 co-incident with repeated summer break-outs of the surrounding land-fast sea ice. A complete ice tongue collapse for these otherwise stable glaciological landmarks along the Victoria Land Coast is previously unrecorded. Prior to break-off, we found an inverse correlation between fast ice extent and ice tongue velocities (R = − 0.62; R 2 = 0.39). The short summer period, characterized by decreased land-fast sea ice extent, showed around 11% higher velocities compared to winter. Any previous events of comparable magnitude could not have occurred since at least ∼1850, assuming continuous growth ( ∼ 193m yr−1) derived from the last 60 years of satellite observations. We highlight the vulnerability of the ice tongue once left exposed to oceanic processes, which poses questions about the fate of other ice tongues if land-fast sea ice decreases more broadly in the future.