Freeze‐Thaw Processes Induce Convective Fingering in Saline Soils

Abstract Saline soils in cold regions are often affected by freeze‐thaw processes, yet how these processes affect two‐dimensional salt transport dynamics remains poorly understood. Here, we show the importance of two‐dimensional flow induced by seasonal freeze‐thaw processes based on a validated numerical model. Under horizontally uniform boundary conditions, cryosuction and salt exclusion during freezing concentrate salts near the freezing front. During thawing, the recovery of permeability and presence of high salinity gradients promote gravitational instabilities, inducing convective fingering after thawing. This process facilitates downward salt transport, preventing long‐term salt accumulation in the shallow soil layer. Further quantitative analysis showed that deeper frost depths or lower water tables favor fingering formation. Based on these results, a new hypothesis regarding salt redistribution in seasonally frozen soils is proposed. It has important implications for understanding salinity dynamics and contaminant migration in cold‐region environments.