Influence of Pore-Scale Convection on Sea Ice Melt Rate

Sea ice is a porous medium of solid ice and brine pockets. Accurate prediction of its formation and long-term evolution requires understanding its pore-scale processes. While sea ice formation by directional freezing of seawater into a mushy layer is well studied, microscopic melting dynamics remain less understood. To address this, we present a phase-field model for bottom-up sea-ice melting driven by ambient seawater. It employs a temperature‐ and salinity‐dependent Gibbs free energy functional derived from alloy solidification theory to recover the seawater phase diagram without empirical constraints and integrates multi-physics evolution with buoyancy‐driven Hele-Shaw flow.

Model fidelity is validated against analog experiments. We then perform centimeter-scale simulations of salinity- and temperature-driven melting in the low-Reynolds regime, capturing key phenomena such as salt rejection and stratification. Notably, density-driven convection suppresses local melting by exporting solutes away from the interface, which alters the thermodynamic balance and modulates phase change rates. These results highlight the critical role of microscale hydrodynamics during sea ice melting, which involves the coupling of heat and solute transport and buoyancy-driven flow within an evolving porous structure. This work provides a foundation for linking pore-scale processes to large-scale sea-ice melt rates.