Overcoming data scarcity of active layer thicknesses using geophysics

• Main Authors: Saintenoy, Albane, Pohl, Eric, Grenier, Christophe, Séjourné, Antoine, Khristoforov, Ivan, Konstantinov, Pavel, Danilov, Kencheeri, Bazhin, Kirill, Fedorov, Alexander
• Other Authors: Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Melnikov Permafrost Institut, Russian Academy of Sciences Moscow (RAS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2018
• Subjects: Ground-Penetrating Radar; Electrical Resistivity Tomography; Active Layer; River Influence; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Active layer thickness; permafrost; Yakutia; Siberia
• Online Access: https://hal.science/hal-04455462; https://hal.science/hal-04455462/document; https://hal.science/hal-04455462/file/Saintenoy-EUCOP2018-abstract.pdf

International audience The thermal imprint of a typical river in the continuous permafrost of Central Yakutia (Siberia, Russia) is studied by active layer thickness measurements along six cross sections, either directly or with geophysical methods. Ground-Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) measurements provide permafrost depths comparable to direct measurements acquired in boreholes and pits when available. Geophysical data interpretations complement non-instrumented cross-sections and show that the unfrozen/frozen interface is deeper below the riverbed for all studied cross sections and depends on the local river width. GPR data provide depths of 1 to 2 m with a sampling step as small as 5 cm when the riverbed width is less than 8 m. Where riverbeds are wider, ERT data are more adapted than GPR in imaging the unfrozen layer. ERT data indicates a permafrost boundary as deep as 6 m for the wide river cases, compared to less than 2 m for the narrower ones. The geophysical data enabled us to reveal an exceptional spatial variability in active layer depths that could not be attributed with in situ measurements before.