CryoGrid is a one-dimensional land surface model dedicated to simulate ground temperatures in permafrost environments.
The model calculates the surface energy balance in order  to  represent energy transfer processes between the atmosphere and the ground. These processes include the radiation balance, the exchange of sensible heat, as well as evaporation and condensation. For a realistic representation of the thermal dynamics of the ground, the model includes processes such as the phase change of soil water and an insulating snow cover during winter.
Further developments of CryoGrid already enable the model to represent processes such as ground subsidence and the formation of thermokarst due to melting of excess ground ice. The implemented lake module (FLAKE) allows CryoGrid also to simulate heat transfer processes of tundra landscapes that are densely populated by lakes and ponds.

Simulation Results

The animation shows the seasonal variations in soil temperature at various depths - under a thermokarst lake and in the non-lake-covered tundra environment. The simulation starts in 1950 and runs up to the year 2100 assuming strong climate warming (RCP8.5 scenario). (The animation shows in extracts the first and last ten years, as well as the decade from 2017 to 2027, in which the ground under the lake is no longer freezing completely in winter for the first time.) Red shades illustrate thawed areas whereas blue shades show frozen areas in the ground and the lake respectively.
Underneath thermokarst lakes, the ground heats up much stronger than in the surroundings. As a result, the thawing front reaches significantly deeper soil layers. This is especially to be expected in warmer climates, when the lake does not longer freezes to the ground. and increases in depth due to the melt of excess ground ice (blue dashed line). Under these circumstances permanently thawed areas (so-called taliks) start to develop.
The different soil temperature profiles are the result of the surface energy balance, which is controlled by the net radiation flux and the sensible and latent heat fluxes (colored arrows). In addition, lateral heat flow in the subsurface leads to a partial convergence of the temperature profiles.