Modelling near-surface ice content and midwinter melt events in mineral soils

Over winter freeze–thaw events are notoriously difficult to represent in hydrologic models and have serious implications for the hydrologic function of intermittently freezing regions. Changing climate is leading to more frequent mid-winter thaw events. Midwinter thaw events are often the cause of flooding due to the combined impacts of snowmelt, precipitation, and limited soil infiltrability. A numerically efficient, semi-analytical coupled thermal and mass transport model is presented that represents the ice content of near-surface soil, and reports the depth of freezing/thawing. The model tracks pore ice formation and mean soil temperature in terms of enthalpy. It is tested against data collected in Southern Saskatchewan and is shown to capably reproduce field observations of frozen, thawed or transitioning soils. This numerically efficient model can be incorporated into regional hydrologic models where it is expected to improve predictions of soil ice content, leading to improved estimates of over-winter streamflow and flood potential. • An interface model is presented to predict the freeze/thaw state of near-surface soil. • Model is benchmarked using midwinter freeze–thaw data from Southern Saskatchewan. • Algorithm is efficient and accurate and is recommended for use in hydrologic models.