Abstract
Exposure of a ground surface to subzero temperatures leads to the formation of a frozen soil layer. Understanding the soil water redistribution associated with thawing of the frozen soil layer is important when considering soil water and nutrient management of farmland. In this study, we performed a one-directional soil column freezing and thawing experiment using unsaturated Andisol, monitored the soil temperature and water profiles in the column, and attempted to simulate the results by using an existing numerical soil freezing model. At the onset of thawing, surface meltwater flowed into and refroze in the middle part of the frozen soil layer. During the thawing, water continued to flow from the unfrozen soil to the frozen soil layer when the soil temperature was lower than -1 °C. When the temperature of the frozen soil layer stagnated at near 0 °C, meltwater infiltrated through the frozen layer, which still contained a certain amount of ice. Two major issues were found for application of the existing soil freezing model to the soil thawing process: (1) modeling the retardation of soil water freezing near 0 °C and (2) improving the hydraulic conductivity model for frozen soil based on the unfrozen water content.
