Abstract

In this study, a simple stochastic representation of the microscale spatial variability in thaw depth in permafrost regions was proposed. Thaw depth distribution measured in the two larch-type forests in eastern Siberia, Spasskaya Pad and Elgeeii, showed different spatial, seasonal, and interannual variability, respectively. Minor year-to-year variation in active-layer thickness was observed in Spasskaya Pad, where a transient layer may constrain further thawing. A gamma distribution accurately represented the thaw depth spatial variability in both sites as the cumulative probability. Thus, a simple model illustrating the spatiotemporal variation in thaw depth as a function of the mean thaw depth was developed using the gamma distribution. A hierarchy of models was introduced that sequentially considered the constant state, linearity, and non-linearity in the dependence of the rate parameter of the gamma distribution for the mean thaw depth. Although the requirements of the model levels differed between Spasskaya Pad and Elgeeii, the proposed model successfully represented the spatial variability in thaw depth at both sites during different thaw seasons.