This paper uses satellite observations and an ice-flow model to quantify the impact of sea-ice buttressing on ice streams on the Antarctic Peninsula. The evacuation of 11-year-old land-fast sea ice in the Larsen-B Embayment on the eastern Antarctic Peninsula in January 2022 was closely followed by major changes in the calving behaviour and dynamics of the ocean-terminating glaciers in the region. Following a decade of gradual slowdown and ice-shelf advance, Hektoria, Green and Crane Glaciers were found to have accelerated by approximately 30% since February 2022, while their ice shelves had almost completely disintegrated.
Previous studies suggested that coupling between land and sea ice may be related to a buttressing effect exerted by land-fast sea ice on glaciers, in a manner similar to the effect of confined ice shelves on upstream glaciers. This study addresses that question using the BISICLES ice-sheet model together with satellite observations applied to a real-world case study. Land-fast sea ice was represented as a thin, viscously deforming ice shelf to derive an upper bound on its ability to alter englacial stress. The results demonstrate that sea-ice buttressing played a negligible direct role in the observed dynamic changes in the Larsen-B Embayment, either through altering stresses on grounded glaciers or by preventing ice-shelf fragmentation. Most significantly, the study provides quantitative evidence and clarification regarding an effect that has frequently been referenced in recent literature, particularly within the land-ice research community.
In addition to the modelling assessment, the study presents new datasets describing the environmental forcing mechanisms active during the sea-ice breakup and subsequent land-ice dynamic response. These include measurements of glacier calving fronts, ice-shelf basal melt rates, which serve as a proxy for ocean temperatures during the study period, air-temperature and wind-speed anomalies, and sea-ice freeboards. The data indicate that, alongside the atmospheric temperature anomaly, a contemporaneous ocean-temperature anomaly was also likely present and contributed to changes affecting the floating ice.
Overall, the paper documents a significant and recent episode of rapid change on the Antarctic Peninsula. The findings have broader implications for studies of glaciological change in other ice-sheet regions, demonstrating that even thick, laterally constrained sea ice exerts negligible buttressing force on grounded ice. This conclusion is directly relevant to other sectors of the Antarctic continent.
Surawy-Stepney, T., Hogg, A. E., Cornford, S. L., Wallis, B. J., Davison, B. J., Selley, H. L., Slater, R. A. W., Lie, E. K., Jakob, L., Ridout, A., Gourmelen, N., Freer, B. I. D., Wilson, S. F., and Shepherd, A.: The effect of landfast sea ice buttressing on ice dynamic speedup in the Larsen B embayment, Antarctica, The Cryosphere, 18, 977–993, https://doi.org/10.5194/tc-18-977-2024, 2024.