The Multi-decadal Collapse of East Antarctica’s Conger-Glenzer Ice Shelf

Abstract Antarctica is losing net mass to the ocean; most of this loss has occurred in West Antarctica and the Antarctic Peninsula, which together hold ~5.5 m of sea level rise (SLR) potential. The East Antarctic Ice Sheet (EAIS) stores almost 10x more ice, and contributes the largest uncertainty to SLR projections, primarily due to insufficient process-scale observations. While EAIS has largely remained stable, it has recently started showing signs of change around its margins. We report the first-ever major ice shelf collapse observed in EAIS, culminating with the March 2022 disintegration of the Conger-Glenzer Ice Shelf, formerly comprising the eastern portion of Shackleton Ice Shelf (SIS) on Knox Coast. Overall, the collapse had four stages spanning several decades starting 1997-2000 when small calving events isolated it from SIS; in 2011, it retreated from a central pinning point, followed by relative quiescence for a decade; the remaining ~1200 km2 area disintegrated over a few days in mid-March 2022. While the pace of most previous ice shelf collapses has prevented detailed sampling, this long-term, multi-stage event provided the opportunity to sample and isolate processes involved in ice shelf collapse, enabling crucial data for early warning indicators and enhancing our understanding of EAIS dynamics and response to future ocean and atmospheric forcing.