Electrical resistivity tomography and electromagnetic induction and measurements at Bogg Creek, Sahtu Settlement Area, Northwest Territories. Sahtu Region, Canada

GeoNetwork: www.gwfnet.net/geonetwork/srv/eng/catalog.search#/metadata/13100_iso.xml Polar Data Catalogue: https://www.polardata.ca/pdcsearch/PDCSearch.jsp?doi_id=13100

Global climate change has had a significant effect on the permafrost landscape in Northern cold regions. Due to natural processes such as precipitation change and rising temperatures, in addition to anthropogenic intervention, we notice a steadily increasing, and systemic pattern of permafrost thaw. The fieldwork took place in the Sahtu region of the Northwest Territories, specifically within the Bogg Creek Watershed, located 30 kilometers South of the Town of Norman Wells. Our work seeks to use two geophysical methods, electrical resistivity tomography (ERT) and electromagnetic induction (EMI) to estimate the permafrost table depth in areas with local landscape features such as lakes and clear cuts. The purpose of this research is also to benchmark a non-ground coupled system (EMI) against the more classical ground-coupled methods (ERT). The ERT system we used is the Syscal Junior 48, and the EMI system was the Geonics Inc EM-31 and EM-34. The field mission lasted four days, and we collected permafrost probe, ERT, and EMI measurements along three survey lines. Two lines (Line 001 and Line 002) were located at a drill pad site, labeled as MW04T, and another line (Line 004) was located near a lake’s shoreline, labeled as “Marg Lake”. The permafrost probe showed a clear plunging of the permafrost table at the tree line at MW04T, and another plunge towards the lakeshore. The ERT data showed similar trends where the regions of high resistivity, representing ice/permafrost, plunged similar to our permafrost probe measurements. Our EMI measurements and interpretation also agreed with the permafrost probe measurements and ERT measurements, whereby a deepening of the permafrost table manifested itself in the data as increasing conductivity. This work successfully demonstrated that small ground-based EMI systems are suitable equipment for use in detecting permafrost thaw in Northern settings.

Northern cold regions are especially susceptible to climatic variations, and as a result of global climate change, it is important to understand the permafrost distribution using more efficient methods. Surficial alterations, both natural and anthropogenic, can be indicators of permafrost degradation. The objectives of this research are to execute the geophysical surveys using electrical resistivity tomography (ERT) and electromagnetic induction (EMI) to detect changes in permafrost table depth and to assess the efficiency of the EMI method versus ERT method within the Sahtu Region in the Northwest Territories. This data set will also support the objectives of projects titled Transformative sensor Technologies and Smart Watersheds (TTWS) and the Northern Water Futures (NWF). These projects are Pillar 3 projects under the Global Water Futures Program funded by Canada First Research Excellence Fund.

Rudolph, D., & Salman, M. (2018). Electrical resistivity tomography and electromagnetic induction and measurements at Bogg Creek, Sahtu Settlement Area, Northwest Territories. Sahtu Region, Canada: Canadian Cryospheric Information Network (CCIN). (Unpublished Data).

https://www.polardata.ca/pdcsearch/PDCSearchDOI.jsp?doi_id=13100