Imminent calving accelerated by increased instability of the Brunt Ice Shelf, in response to climate warming

Abstract Ice shelves in the Southern Weddell Sea have large areas and volumes, and have previously been stable due to their setting in a region of cold near-surface and sub-surface ocean water. The Brunt Ice Shelf (BIS), one of the ice shelves closest to the continental shelf break in the region, just released an iceberg with an area of ∼1,270 km2 in late February 2021 and another large calving event is imminent. However, recent changes in the BIS, since 2017, have not been studied to date. In this study, we used multi-source remote sensing data (including satellite images, ice flow velocity products, digital elevation models, and altimetry data) to conclude that the instability of the ice shelf has been increasing. The increased instability is manifested by rapidly increasing ice flow velocity and the propagation rate of full-thickness rifts. The velocity at the front of the BIS accelerated by more than doubled from 2013–2021, and the width of Chasm 1 increased by almost three-fold from 2012–2021. Based on the expansion of Chasm 1 and the strain rate changes, an iceberg with an area of ∼1,675 km2 is predicted to be released from the BIS during October 2022. We used meteorological data, ocean synthesis, and field observations to attribute the increased instability of the BIS to warm inflow onto the continental shelf, which emphasizes the importance of further observation and analysis. Additionally, owing to its special location, the BIS could be an indicator of the evolution of other ice shelves in the Southern Weddell Sea.