Firn, the compacted snow layer covering glaciers and ice sheets, controls how surface meltwater is stored or runs off to the ocean and therefore influences sea-level rise. While firn can buffer meltwater and delay runoff, the widespread expansion of ice layers, observed by in situ and remote sensing measurements, may limit storage and enhance runoff. Firn hydrology lies at the intersection of multiphase flow, thermodynamics, and phase change in porous media. However, many large-scale models rely on simplified representations that obscure key physical processes. This talk presents recent theoretical and numerical advances toward a mechanistic understanding of meltwater dynamics and ice layer formation in firn across spatial scales, with direct implications for next-generation ice sheet and Earth system models.

Speaker-recommended reading: The Firn Symposium team. Firn on ice sheets. Nat Rev Earth Environ 5, 79–99 (2024). https://doi.org/10.1038/s43017-023-00507-9