Laboratory simulation of retrogressive thaw slumps

Over the last decades, the ice-rich permafrost (with ice wedges and massive ice) of Central Yakutia (Eastern Siberia) was highly vulnerable and prone to extensive degradation named thermokarst. The presence of large scale thermokarst slumps were observed whose name is Retrogressive thaw slumps. Here, we present results of a full-scale physical modelling of such retrogressive thaw slumps in a cold room. We used the cold-room at the GEOPS laboratory (CNRS/University of Paris Saclay, France) dedicated to the physical modelling in periglacial geomorphology. These experiments were instrumented using temperature sensors to survey the freezing and thawing front vs. time. Our results show that heterogeneous frozen soil with ice wedges undergoes a strong decohesion of its structure during the thawing phase and an easier circulation of warm air.

Data were collected using a rectangular box of 2.5 m x 2.5 m wide and 0.5 m depth in which a ground surface of fine sand (D50 = 200 µm; Wp (max) = 20 %) materials was saturated with water. These experiments were instrumented using 10 temperature sensors (platinum resistance thermometers Pt100 with ±0.1°C accuracy) to survey the freezing and thawing front vs. time. All data are in °C and registered in a data-logger. During each simulation, we also analyzed the development of associated thermokarst degradation landforms using time-lapse photography with a video camera.

File name thermokarst1: Time-lapse of the RTS experiment with artificial ice wedges (experiment 1).

File name thermokarst 2: RTS experiment with icy layers (experiment 2).