Long-Term effects of climate warming on thermal-hydraulic-carbon-mechanical processes in permafrost slopes of the Qinghai-Tibet plateau

Abstract

Climate warming has caused permafrost degradation. Rising temperatures have triggered frequent permafrost slope hazards, exposing deep soil organic carbon to decomposition, thereby impacting the carbon cycling process. The interactions between water-heat migration, organic carbon decomposition, CO₂ transport, and slope deformation create a complex, multi-physical field coupling problem. This paper develops a thermal-hydraulic-carbon-mechanical coupling model to study the long-term effects of warming. The conclusions are as follows: (1) Rising temperatures warm permafrost slopes, thickening the active layer and reducing ice content. Deep soils are particularly sensitive to temperature changes, causing areas with high ice content to shift from continuous layers to isolated, island-like distributions. (2) Temperature increases accelerate soil organic matter decomposition, raising CO₂ concentrations. Seepage reduces gas diffusion at the slope base, resulting in CO₂ accumulation. (3) As temperatures increase, soil carbon flux rises. Temperature gradients cause deeper soils to have lower carbon flux than shallow soils, with vertical flux exceeds horizontal flux. Additionally, higher water content at the slope base results in a lower carbon flux. (4) Changes in thermal and moisture conditions affect soil mechanics. Creep causes subsidence at the slope top and uplift at the base, with horizontal displacement peaking at mid-slope.