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

Abstract

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.

摘 要

土壤冻融过程影响冻土区土壤的导热率、热容、导水率等物理性质,进而影响土壤的能量、水文、碳氮循环过程。本研究将计算冻融界面的参数化方案应用于中国科学院地球系统模式(CAS-ESM)及其陆面分量CoLM,研究冻融界面动态变化及其影响。结果表明:所发展的考虑冻融界面动态变化的模式能够准确模拟土壤冻融过程以及冻融界面的动态变化。多年冻土区活动层厚度为1.92 m,变化趋势为+0.35 cm yr–1。季节性冻土区最大冻结深度为2.15 m,变化趋势为-0.48 cm yr–1。活动层厚度逐年增大,最大冻结深度逐年减小。这些结果有助于更好地理解冻土的冻融循环过程。