The Geophysical Institute Permafrost Lab (GIPL) model was developed specifically to assess the effect of a changing climate on permafrost. The GIPL 1.0 model is a quasi-transitional, spatially distributed, equilibrium model for calculating the active layer thickness and mean annual ground temperature. The GIPL-1 model accounts effectively for the effects of snow cover, vegetation, soil moisture, and soil thermal properties. The GIPL-1 model allows for the calculation of maximum active layer thickness (ALT) and mean annual ground temperatures (MAGT) at the bottom of the active layer. The approach to determine the ALT and MAGT is based on an approximate analytical solution that includes freezing/thawing processes and provides an estimation of thermal offset due to the difference in frozen and thawed soil thermal properties (Kudryavtsev, et al., 1974). It uses the idea of applying the Fourier temperature wave propagation theory to a medium with phase transitions, such as freezing/thawing ground. Application of this approach resulted in the discovery of the thermal offset and an understanding of the laws that govern the dynamics of the ground thermal regime. These discoveries led to an understanding of the effects that the thermal properties of the ground have upon the MAGTs and ALT, and how periodically (seasonally) varying climatic parameters affect permafrost dynamics. The output parameters of this method are given as annual averages.
