DC Electrical Resistivity Imaging at a High-Arctic Continuous Permafrost in Svalbard, Norway

Direct-Current (DC) electrical resistivity imaging has proven to be a suitable technique for a number of permafrost related questions. We present measurements from a high-arctic continuous, maritime permafrost site near Ny Alesund, Svalbard (Norway). The area under investigation features a great diversity of soil types and soil water contents. Sparse vegetation alternating with rock fields and exposed soil characterize the surface.A total of 25 different transects each of 47.5m length were investigated using a DC-Resistivity and Electrode Control System (RESECS) with 96 electrodes at a spacing of 0.5m in Wenner-alpha configuration. At three transects, fixed electrode arrays were installed and measured on a weekly basis in order to capture temporal changes. The study was conducted from August until mid-September, thus covering the period of maximum active layer thickness and the beginning of freeze-up.The specific resistivities at the surface ranged from less than 50 Ohm m in areas with damp clay to more than 1000 Ohm m in rock fields and on dry hill crests. In most cases, areas with such high resistivities only extended to depths of less than 1 m. From depths between 1m and 1.5m onwards, specific resistivities increased continuously, indicating the position of the freeze-thaw interface. This agrees well with thaw depths that were determined by point measurements along individual transects using a drill.The repeated measurements of the fixed electrode arrays displayed the most pronounced changes in the beginning of August, where decreases in specific resistivities of up to 40% over one week period were detected at depths between 1m and 2m. Afterwards, only insignificant changes were observed at these depths. This is interpreted to be the seasonal thawing of the active layer, which stagnates during in the second half of August. At depths less than 1m, both decreases and increases in specific resistivities were detected, most likely due to changes in the water content of the soil