Physical Modeling of Coastal Permafrost Erosion: A New Model for Predicting Niche Depth Evolution

Abstract Permafrost coastal systems are critical to Arctic environmental processes, and understanding their erosion dynamics is essential for addressing climate change impacts. These coastlines undergo unique thermomechanical erosion, where wave action, rising sea levels, and thermal degradation jointly drive a rapid coastline recession. This study demonstrates advancements in physically modeling coastal permafrost erosion using a laboratory setup that replicates natural Arctic coastal conditions. A wave flume with a representative nearshore slope and reproducible permafrost specimen preparation methodology allowed isolation of the hydrodynamic and thermodynamic effects. Distinct erosion patterns and rates were quantified under varying wave heights, periods, and thermal conditions. Results indicate that wave height is a dominant mechanical driver, with mean erosion rates increasing by over 100% from low to high wave conditions. Even low‐energy waves ( H = 0.02 m) enhanced erosion by more than 50% compared to still‐water conditions. Additionally, a higher ice content reduced niche deepening rates by 38%, which is attributed to latent heat delaying thawing. A new scalable thermomechanical model for erosional niche incision on an Arctic bluff is proposed based on a power‐law relationship that integrates the Froude, Iribarren, and Stefan numbers. This dimensionless approach captures the coupled influence of wave‐induced forces and permafrost thermal properties, exhibiting a strong predictive capability ( R 2 = 0.90) and outperforming existing analytical models. The experimental framework and new model offer new insights into Arctic coastal retreat mechanisms and provide a promising foundation for regional‐scale applications in coastal management under changing climatic conditions.