Investigating effects of thermokarst lakes on permafrost under equilibrium conditions

The degradation of permafrost due to climate change has significant effects on the hydrological processes and ecosystems in arctic and subarctic regions. Thermokarst lakes, formed from permafrost thaw and subsidence, play a crucial role in this process by influencing heat storage and exchange and accelerating the thaw rate of the surrounding permafrost. A direct effect of these lakes is the formation of taliks, perennially thawed soil. We present a two-dimensional coupled thermodynamic equilibrium model that is used to study the influence of thermokarst lakes on talik size and stability. Factors such as lake size, temperature and pressure boundary conditions, and geothermal heat flux are investigated to determine their relative effect on thaw depth and average soil pore ice fraction. Results show that air temperature and lake size primarily dictate talik thickness and shape, not pressure-induced refill. Additionally, for lakes with a depth of over 2.5 m, the thaw is predicted to extend to the permafrost base, creating an open talik for all realistic air and water equilibrium temperatures. These findings underscore the importance of considering temperature trends and establishing tools to understand permafrost dynamics through remote monitoring of lake size and depth. Understanding these processes allows us to assess permafrost stability and informs land management and infrastructure planning in cold regions.