Surface melt driven changes to ice properties for a marine-based ice shelf and the influence on fracture propagation: Insights from a core on the Brunt Ice Shelf

Fracture-induced ice shelf instability is a critical contributor to uncertainties in sea level projections, which are central to global flood mitigation planning. While the occurrence of ice fracturing at critical stress thresholds is well-documented, the mechanisms governing fracture timing, rate, and orientation remain poorly understood, particularly across ice shelves with varying ice properties and provenance. Observations on the Brunt Ice Shelf reveal unique fracture behaviours, where rifts deviate from their stress-predicted pathways to avoid blocks of meteoric ice, and preferentially fracture through thinner marine ice. The speed of propagation is also influenced by these differences in ice type.   

To improve our understanding of these fracture dynamics, a 37 m firn core through thin, marine-based ice was collected in 2024 on the Brunt Ice Shelf. This core provides a high-resolution record of precipitation and climate changes over the past 40 years, with saline layers at the base. Biogenic species within the core trace variations in summer sea ice extent and proximity to open water, including the A-81 calving in 2023, while an increasing prevalence of melt layers highlights a rise in surface melt. By integrating fracture toughness measurements from layers with varying melt and accumulation conditions, we demonstrate how climatic and environmental shifts could influence ice shelf susceptibility to fracture propagation.