How does soil water content influence permafrost evolution on the Qinghai-Tibet Plateau under climate warming?

Abstract

The active layer thickness (ALT) in permafrost regions regulates hydrological cycles, water sustainability, and ecosystem functions in the cryosphere and is extremely sensitive to climate change. Previous studies often focused on the impacts of rising temperature on the ALT, while the roles of soil water content and soil granularity have rarely been investigated. Here, we incorporate alterations of soil water contents in soil thermal properties across various soil granularities and assess spatiotemporal ALT dynamics on the Qinghai-Tibet Plateau (QTP). The regional average ALT on the QTP is projected to be nearly 4 m by 2100. Our results indicate that soil wetting decelerates the active layer thickening in response to warming, while latent heat exerts stronger control on ALTs than thermal conductivity does. Under similar warming conditions, active layers thicken faster in coarse soils than in fine soils. An important ramification of this study is that neglecting soil wetting may cause overestimations of active layer thickening on the QTP.