Measuring properties such as snow and soil temperature and deformation with high vertical and lateral resolution is critical for advancing the predictive understanding of thermal, hydro-biogeochemical and geomechanical processes that govern the behavior of environmental systems. Vertically resolved temperature measurements enable the estimation of thermal regimes, soil freeze/thaw layer thickness, thermal parameters, and heat and/or water fluxes. Depth resolved measurements of soil deformation are crucial to inform on geomechanical processes, evaluate their controls, as well as their implication for carbon fluxes or slope stability.  However, all the above-mentioned measurements are challenging to acquire using conventional approaches due to their total cost, their limited vertical resolution, and their large installation footprint. To address these measurement challenges, we developed a novel acquisition system composed of a miniaturized, wirelessly connectable, ultra-low power logger linked to an array of digital sensors. From an electromechanical perspective, we developed a novel solderless board-to-board connection method that enables narrow, semi-flexible sensor arrays and a streamlined assembly process. In a first configuration, temperature sensors are cascaded to provide unprecedented, finely resolved depth profiles of soil or snowpack. A novel calibration approach adapted to the temperature sensors confirms the factory-assured sensor accuracy of ±0.1 oC and enables improving it to ±0.015 oC. In a second configuration, temperature sensors are alternated with accelerometers for soil deformation measurements. The characterization of the system accuracy indicated that deformation measurements can be performed with an accuracy of ±0.73 mm per meter of probe length. The deployment of the system at various sites indicates it reliably captures the dynamics in snow depth, and soil freezing and thawing depth, enabling advances in understanding the intensity and timing in surface processes and their impact on subsurface thermal-hydrological regimes. The combination of depth-resolved measurements of deformation and temperature captures the soil movement and how a slip plane collocated with the interface between frozen and unfrozen soil is driving it (Figure). Overall, the developed system fulfills the needs for data accuracy, minimal power consumption, and low total cost, opening the door for the multiscale understanding of various cryospheric, hydro-biogeochemical and geomorphological processes that critically impact water and carbon fluxes in the Arctic.

Dafflon B, S Wielandt, J Lamb, P McClure, I Shirley, S Uhlemann, C Wang, S Fiolleau, C Brunetti, FH Akins, J Fitzpatrick, S Pullman, R Busey, C Ulrich, J Peterson, and SS Hubbard (2022). A distributed temperature profiling system for vertically and laterally dense acquisition of soil and snow temperature. The Cryosphere 16: 719-736. https://doi.org/10.5194/tc-16-719-2022

Wielandt S, S Uhlemann, S Fiolleau, and B Dafflon (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

Contact and email address: Stijn Wielandt (stijnwielandt@lbl.gov), Sebastian Uhlemann (suhlemann@lbl.gov), and Baptiste Dafflon (bdafflon@lbl.gov)