Quantifying freeze-thaw erosion dynamics in retrogressive thaw slumps: integrating geophysical and experimental approaches

• Integrated approach links freeze–thaw erosion mechanisms to RTS dynamics. • Geophysical surveys reveal 2.2–5.5 m ground ice controlling erosion intensity. • Ground ice content drives freeze–thaw erosion via quadratic relationship. • Freeze-thaw erosion feedbacks accelerate permafrost landscape degradation. While retrogressive thaw slumps (RTSs) are recognized as the most dynamic permafrost degradation features, their comprehensive freeze–thaw erosion mechanisms remain poorly quantified. This study integrates multi-methodological surveys with controlled laboratory experiments to assess RTS-induced erosion impacts. Field investigations employed UAV photogrammetry, electrical resistivity tomography, ground-penetrating radar, and nuclear magnetic resonance at the studied RTS site. Laboratory experiments utilized modified triaxial testing under natural thawing consolidations to simulate ice-rich permafrost thawing. Results reveal maximum headwall retreat rates of 2.8 m/a with 5,418 m 3 total volumetric changes during 2021–2024. Geophysical surveys identified massive ground ice with significant hydraulic parameter modifications in affected zones. Laboratory thawing experiments demonstrated ice-content-dependent thaw settlement mechanisms, with thaw settlement coefficients increasing quadratically. Meltwater analysis revealed dramatic increases in suspended solids (375–866 ppm) and dissolved solids (148–423 ppm) with increasing ice content. The integrated analysis demonstrates that RTS erosion operates through coupled pore pressure increases and ice cementation loss, generating enhanced particle transport and soil instability. Critical infrastructure implications emerge as the studied RTS maintains only 179 m distance from the Qinghai-Tibet Railway, creating cascading hydrological impacts that threaten embankment stability. This integrated multi-method approach provides a quantitative framework for assessing freeze–thaw erosion broader impacts and infrastructure risks under accelerating climate change.