Understanding hillslope deformation mechanisms in permafrost environments using a dense sensor network.

The rapid evolution of the landscape in the Arctic observed over many years is of concern from a climate perspective, but also regarding emerging natural hazards. Part of this evolution involves soil deformation which, by redistributing soil and organic matter, is impacting the soil carbon cycle. The variety and complexity of the mechanisms controlling soil movement is a significant source of uncertainty in estimating current and future soil carbon storage and fluxes. A better understanding of the soil deformation triggers and kinematics will allow us to better understand their impact on climate change.

In this study, we investigate soil deformations and their controls in a discontinuous Arctic permafrost environment using a dense, low-cost sensor network providing depth-resolved deformation and temperature measurements to depths up to 1.8 m (Wielandt et al., 2022). The sensor network was deployed at 59 locations across a 2 km² watershed located near Nome, AK. The deformation and temperature were monitored with a high resolution from May 2022 to September 2022. During this period, the watershed experienced air temperatures exceeding 0°C and numerous rain events, leading to critical conditions for soil deformation. During the monitoring period, displacements of a few millimeters to tens of centimeters were recorded to depths up to 1.8 m. These displacements showed different spatio-temporal patterns that vary as a function of the topographic position, the subsurface structure and the thermal and hydrological states. While some locations showed a clear relationship between seasonal thaw depth and soil deformation, other locations remained either stable or deformed mostly in response to rainfall events. A detailed analysis of the data allowed us to highlight the different factors controlling the deformation (e.g. slope aspect, permafrost depth, bedrock depth, soil moisture, etc.). We were thus able to characterize the impact of each factor on the evolution of the morphology of the watershed. This study provides a better understanding of the mechanisms controlling hillslope deformation and their possible impact on the soil carbon distribution and the hazard they may represent.

Wielandt, S., Uhlemann, S., Fiolleau, S., Dafflon, B., 2022. Low-Power, Flexible Sensor Arrays with Solderless Board-to-Board Connectors for Monitoring Soil Deformation and Temperature. Sensors 22, 2814. https://doi.org/10.3390/s22072814