Coupling of the Calculated Freezing and Thawing Front Parameterization in the Earth System Model CAS-ESM.

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. [ABSTRACT FROM AUTHOR]