Experimental Insights Into Freeze‐Thaw Effects on Fine‐Grained Sediment Rheology Under Thermokarst Development

Abstract With rising global atmospheric temperatures, permafrost is rapidly degrading, forming thermokarst. These landscapes release large quantities of stored carbon into the atmosphere and threaten infrastructure. As thermokarst develops, freshly exposed permafrost enters the freeze‐thaw cycle, altering sediment properties. While freezing and thawing have been shown to reduce sediment strength and increase mobility, their effects under thermokarst conditions remain unexamined. To address this gap, we performed classical friction mechanics (slide‐hold‐slide and velocity stepping) experiments on fine‐grained sediments to examine the effects of a single freeze‐thaw cycle on the steady‐state and transient rheology under near‐surface pressures. Additionally, we applied Rate‐and‐State Friction laws to model transient localized deformation, revealing altered behavior in the rate‐dependent response and frictional healing potential following freeze‐thaw. Our results suggest that freeze‐thaw decreases the shear strength of fine‐grained sediments and increases mobilization potential in ways currently unaccounted for in future thermokarst development predictions and cold regions land surface hazards.