Permafrost Mapping with Electrical Resistivity Tomography in Two Wetland Systems North of the Tanana River, Interior Alaska

Surface-based 2D electrical resistivity tomography (ERT) surveys were used to investigate the distribution of permafrost at wetland sites on the alluvial plain north of the Tanana River, 20 km southwest of Fairbanks, Alaska, in June and September 2014. The sites contained landscape features characteristic of interior Alaska, including thermokarst bog, forested permafrost plateau, and a rich fen. These sites range from treed to open and vary in groundcover vegetation and peat thickness. At a bog site, two profiles of roughly 200 m distance were surveyed across a thermokarst bog bordered by spruce forest and forested permafrost plateau. At a fen site, a 180 m profile was run from a mixed spruce forest (Picea mariana and Betula papyrifera) across a vegetation gradient into an open fen. Different electrode array types, including dipole-dipole, extended dipole-dipole, and Wenner-Schlumberger, were compared and showed similar profile results. Overall, the results highlight the relationships between vegetation type and permafrost occurrence, and the results demonstrate the utility of ERT in characterizing thaw features in a lowland permafrost setting. The depth of thaw and thermal influence from the surface shown in the results are important in understanding the depth to which permafrost degradation may affect carbon storage and biogeochemical phenomena.