NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: permafrost, permafrost degradation

Objective(s): (1) Fly multiple lines of airborne electromagnetic (AEM) geophysical data (between 4 and 6 parallel lines ~100 m apart) between Inuvik and Tuktoyaktuk, beginning and ending just outside the communities; (2) Using the geophysical and geological data, produce maps of the ITH corridor of permafrost and ground ice distribution, areas of thaw, and aggregate potential; and (3) Using these data, produce maps of ground hazards (areas of potential thaw) along the corridor.

Project Description: This licence has been issued for the scientific research application No. 5688. The objectives of this research project are to: 1) fly multiple lines of airborne electromagnetic (AEM) geophysical data (between 4 and 6 parallel lines ~100 m apart) between Inuvik and Tuktoyaktuk, beginning and ending just outside the communities; 2) using the geophysical and geological data, produce maps of the Inuvik Tuktoyaktuk Highway (ITH) corridor of permafrost and ground ice distribution, areas of thaw, and aggregate potential; 3) using these data, produce maps of ground hazards (areas of potential thaw) along the corridor. The research team will use airborne geophysics (helicopter-based surveys) flying along the ITH corridor to map permafrost across different landforms and terrain types. These data will be used by graduate students at the University of Alberta and University of British Columbia as part of their PhD Research in Earth Sciences and Geophysics. The research team will use airborne geophysics—Airborne Electromagnetic Methods (AEM) – an approach used successfully in Alaska to map permafrost, areas of thawed ground within permafrost (taliks), groundwater interactions with permafrost, and ground ice. AEM geophysical surveys allow 3-D snapshots, over large distances quickly, and identify relations between surface water and geological features and the underlying permafrost and ground ice. One of the main insights from the work in Alaska has been to understand the influence of surface water and groundwater on permafrost and how that affects permafrost distribution and potential areas of thaw. The AEM method works by having pairs of coils in a sensor (fibre glass and Kevlar tube about 10 m long that looks like a torpedo) that is suspended below a helicopter that flies about 60 m above the ground surface. Each pair of coils operates at a different frequency (400 Hz to 140,000 Hz) but at levels safe to humans and animals and well below Health Canada and U.S. IEEE guidelines for exposure to electromagnetic signals. In an AEM survey the sensor transmits an electromagnetic signal at multiple frequencies and reads back the reflection from the ground. Longer wavelengths penetrate deeper into the earth while shorter wavelengths image shallower layers. More conductive layers return a stronger signal while less conductive (more resistive) layers return a weaker signal. In permafrost areas, frozen ground is strongly resistive while thawed ground and water is much more conductive. Combining these measurements with knowledge of the geology (from existing borehole and earlier geological work) the ground subsurface, including whether permafrost distribution, its thickness and ground ice content can be mapped. The variations of these signals allow permafrost to be imaged in the ground from these data. This will allow the research team to understand how groundwater interacts with permafrost, where permafrost is present, and areas that are ice-rich and ground hazards might be present. The study in Alaska was carried out near Fort Yukon where permafrost is about 50 m thick. A similar study with much deeper permafrost, as would be expected along the ITH, has not been previously carried out making this an important study location A comparable set of surveys will be carried out between Norman Wells and Wrigley also late this summer or early Fall. The research team will utilize the Resolve system from XCalibur MultiPhysics which uses multiple frequencies close to radio waves (from 400 and 140,000 Hz). These frequencies are transmitted and measured from a sensor suspended below the aircraft. Typically, the aircraft will fly at relatively low speed (a few 10s of metres per second). The helicopter will fly at about 60 m above the ground surface (and any obstacles) with the sensor suspended about 30 m below the aircraft. These flights will take place between 7 am and 8 pm usually in 3 trips lasting 2.5-3 hours each. The helicopter flying crew is supported by a ground crew that aids with calibration of the sensor. The pilot is guided by a GPS navigation system and radar altimeter in the helicopter. The survey lines are pre-programmed in the navigation system and provide guidance to the pilot. The surveys consist of 4 to 6 closely spaced lines flown in blocks. These blocks will be analyzed to produce a 3D image of each block. The helicopter is equipped with a satellite phone system allowing ground to air communications. Survey flights follow Transport Canada regulations for underslung load operations. The helicopter pilot will avoid overflight of people, vehicles or structures that could contain people. Following the AEM surveys, the research team will pair these data with their existing geological studies that the research team has been carrying out within the Inuvik area (PhD work of Alejandro Alvarez supervised by Duane Froese at the University of Alberta and Steve Kokelj at the Northwest Territories Geological Survey). A Geophysics PhD student will be working on the geophysics parts of this project. The research team will utilize the geological data, collected previously in the area, with existing drilling data associated with the ITH. The research team estimates that they will fly about 800 km of AEM surveys between Inuvik and Tuktoyaktuk. Once the research team has these data and have developed its relations to geology and permafrost conditions, they will use these data to map larger areas of the delta and uplands outside of the immediate transportation corridor. These data will be especially valuable in trying to understand why some areas of permafrost are changing rapidly while other areas are relatively stable. Ultimately, the research team believes these data will become valuable for future planning through the region. The research team would like to give community presentations on the work either in person (or remote), depending on community interest and timing, following the approach the team used communicating their past work in the Sahtu region. This would include in-person presentations in the communities closely associated with the proposed permafrost surveys (Inuvik and Tuktoyaktuk), or remote presentations that coincide with existing meetings. The research team would coordinate these with Aurora Research Institute. The team used both methods this past year in the Sahtu region, and found using both options to be effective opportunities to present research but also to hear about community concerns, input and observations related to changing permafrost conditions. The surveys and all the data will (likely 2024) be published in an Open File Report by the Northwest Territories Geological Survey ensuring the data are available to anyone interested in permafrost within the areas flown in the surveys. The fieldwork for this study will be conducted from: August 07 - December 31, 2023