Multiple thermophysical effects of aeolian sand cover on permafrost under climate warming and wetting

• A multiphysics coupling model for the freeze–thaw process of aeolian sand is proposed. • Impact mechanism of climatic changes on permafrost under aeolian sand is revealed. • Response of permafrost to the land–atmosphere interaction is discussed. Permafrost degradation on the Tibetan Plateau (TP) poses serious risks to the environment and infrastructure. Permafrost changes are controlled by both climate changes and local factors, including climate warming, wetting, and aeolian desertification, but the heat transfer process and hydrothermal mechanism under aeolian sand cover (ASC) remain poorly understood. Using a model test and a coupling numerical model, this study analyzes the effects and mechanisms of warming and wetting on permafrost under ASC. The results indicate that: Under thin ASC, infiltration is tiny and heat conduction dominates heat transfer, and climate warming increases surface heat flux and accelerates permafrost degradation by enhancing the net radiation and reducing the sensible heat. Under thick ASC, infiltration and heat convection become significant, and climate warming increases the annual infiltration by extending the thawing period, drives the decrease in latent heat of evaporation, and further promotes permafrost degradation. As precipitation increases, thin ASC cools the permafrost by enhancing evaporation and reducing surface heat flux. In contrast, thick ASC warms the permafrost by suppressing evaporation increment and enhancing both surface heat flux and subsurface heat convection.