Three-dimensional distribution and evolution of permafrost temperatures in idealized high-mountain topography

Permafrost degradation is regarded as a crucial factor influencing the stability of steep rockwalls in alpine areas. Discernment of zones of fast temperature changes requires knowledge about the temperature distribution and evolution at and below the surface of steep rock. In complex high-mountain topography, strong lateral heat fluxes result from topography and variable surface temperatures and profoundly influence the subsurface thermal field. To investigate such three-dimensional effects, numerical experimentation was conducted using typical idealized geometries of high-mountain topography, such as ridges, peaks, or spurs. The approach combines a surface energy balance model with a three-dimensional ground heat conduction scheme to investigate belowground temperature distribution and permafrost occurrence in high-mountain topography. Time-dependent simulations are based on scenario data gained from regional climate models. Results indicate complex three-dimensional patterns of temperature distribution and heat flow density below mountainous topography for equilibrium conditions, which are additionally perturbed by transient effects. Permafrost occurs at many locations where temperatures at the surface do not indicate it, e. g., on the south face of ridges or below the edges of a peak. The modeling tools applied have potential for a number of studies in high mountains addressing questions related to permafrost distribution and evolution at depth in real topographies, for instance, the reanalysis of temperature-related instabilities.