Quantifying the Buttressing Contribution of Sea Ice to Crane Glacier

Antarctic sea ice extent reached a record minimum in 2023. Whilst the buttressing resistance provided by ice shelves has been quantified through past numerical studies, the degree to which sea ice can buttress and regulate upstream ice flow is not known. If significant, a future decline in sea ice extent would lead to increased ice discharge rates and a higher global mean sea level.The January 2022 disintegration of landfast sea ice in the Larsen B embayment was closely followed by a significant increase in ice flow velocities and retreat rates of numerous outlet glaciers in the region. Notably, Crane glacier saw an initial ~8km retreat over six weeks, during which time a 5% increase in velocity was observed. Afterwards, the full evacuation of ambient sea ice between October and November was accompanied by the most significant monthly increase in velocities.We use the numerical ice flow model, Ua, to investigate the buttressing effect of sea ice to Crane glacier. The ice-sheet model was initialised with sea ice included and constrained with observational velocity and geometry data sets. We conducted perturbation experiments on sea ice properties to explore its impact on the glacier. The results suggest that sea ice provided significant buttressing to the glacier before its collapse.