The soil freezing and thawing process affects soil physical properties, such as heat conductivity, heat capacity, and hydraulic conductivity in frozen ground regions, and further affects the processes of soil energy, hydrology, and carbon and nitrogen cycles. In this study, the calculation of freezing and thawing front parameterization was implemented into the earth system model of the Chinese Academy of Sciences (CAS-ESM) and its land component, the Common Land Model (CoLM), to investigate the dynamic change of freezing and thawing fronts and their effects. Our results showed that the developed models could reproduce the soil freezing and thawing process and the dynamic change of freezing and thawing fronts. The regionally averaged value of active layer thickness in the permafrost regions was 1.92 m, and the regionally averaged trend value was 0.35 cm yr(-1). The regionally averaged value of maximum freezing depth in the seasonally frozen ground regions was 2.15 m, and the regionally averaged trend value was -0.48 cm yr(-1). The active layer thickness increased while the maximum freezing depth decreased year by year. These results contribute to a better understanding of the freezing and thawing cycle process.

In this study, we implement a new frozen-soil parameterization scheme into the climate system model CAS-FGOALS-g3 to investigate the dynamic changes of freezing and thawing fronts and the effects arising from thermal processes and climate. Simulations are conducted using the developed model to validate its performance relative to multi-source observations. It is shown that the model could reasonably reproduce soil freezing and thawing processes, including dynamic changes in freezing and thawing fronts. The historical simulation shows that the maximum freeze depth increases with an increase of latitude in seasonally frozen ground, and the active layer thickness decreases with an increase of latitude in permafrost regions. The active layer thickness shows increasing trends while the maximum freeze depth shows decreasing trends, which is consistent with change in the 2-m air temperature. In conclusion, these results have the potential to further deepen our understanding of the freeze-thaw cycle process and the historical response of permafrost to climate change.