oa Geophysical Characterization of Permafrost Distribution in the Yukon River Basin, Alaska

Geophysical Tools including airborne electromagnetic (HEM), time domain electromagnetic (TDEM), DC resistivity and continuous resistivity profiling (CRP) are used to evaluate permafrost distribution in the Yukon River Basin in the area of fort Yukon, Alaska. Permafrost is a primary control on hydraulic processes in interior Alaska, but its distribution is poorly characterized. Major questions about the distribution of permafrost limit understanding of hydrology such as the thickness of the permafrost layer, the geometry of taliks and their role in the hydrogeologic framework, and the connection between surface water and groundwater. Electrical and electromagnetic geophysical technologies can be used to characterize permafrost distribution by exploiting the high resistivity contrast of frozen and liquid water phases. these techniques can provide improved spatial coverage at a higher resolution and lower cost than traditional direct sampling techniques, which remain sparse in the area. in an effort to develop geophysical techniques for characterizing permafrost and inform hydrologic models, Initial campaigns of geophysical data collection were conducted during the summer of 2010. HEM data was collected from a helicopter in the region surrounding fort Yukon, Alaska, including the Yukon River and the Porcupine River. using Initial results of the HEM surveys, sites were chosen to collect ground based geophysics to investigate anomalies that appear to relate to the hydrogeologic framework of the area. the ground based geophysical campaign included TDEM, DC resistivity, and CRP. Initial results from this campaign show that the techniques can be successfully used to map thickness and distribution of permafrost in the area.