Interaction of the Atmospheric Boundary Layer with degrading Arctic permafrost: A numerical study

The vulnerability of Arctic permafrost to climate change is evident, with anticipated widespread enhanced thawing under climate warming. This process may release substantial amounts of organic carbon. The positive feedback mechanism resulting from accelerated thaw and increased carbon emission is suspected to be a potential tipping element, possibly occurring within the 1.5 °C global warming range of the Paris Agreement. The consequences of Arctic permafrost thaw extend beyond carbon release, with the capability to drastically alter Earth's surface in Northern high latitudes.

This study employs high-resolution Large Eddy Simulations to investigate the impact of changing surfaces in the Arctic region on the neutrally stratified Atmospheric Boundary Layer. Utilizing a stochastic land cover model based on Gaussian Random Fields, representative permafrost landscapes are classified by distinct surface features. Experiments varying the areal fraction and surface correlation length of these surface features reveal significant insights into the sensitivity of the boundary layer to surface heterogeneity.

Key findings include a substantial impact of areal fraction of open water bodies on aggregated sensible heat flux at the blending height, suggesting a potential feedback mechanism: The smaller the areal fraction of open water bodies, the greater the sensible heat flux, the warmer the surface. Additionally, the blending height is significantly influenced by the correlation length of surface features. A longer surface correlation length leads to an increased blending height, highlighting the relevance of this metric for land surface models focused on Arctic permafrost.