NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: physical sciences, permafrost thaw, permafrost mapping, thaw slump

Objective(s): To investigate the three-dimensional subsurface structures in the vicinity of active retrogressive thaw slumps and their relationship to spatio-temporal slump-development.

Project Description: This licence has been issued for the scientific research application No. 5655. This project aims to investigate the three-dimensional subsurface structures in the vicinity of active retrogressive thaw slumps and their relationship to spatio-temporal slump-development. The number and activity of retrogressive thaw slumps have increased during the last decades due to climatic, hydrologic and thermal changes. This study aims to highlight the influence of small-scale heterogeneities within the subsurface on the development of retrogressive thaw slumps along lake shores on the Tuktoyaktuk Peninsula and within the Inuvik-Tuktoyaktuk-Highway corridor. Especially linkages between vegetation cover, active layer thickness, ground ice content and water pathways within the subsurface will be investigated in detail. High-resolution, three-dimensional geophysical subsurface models will enable the delineation of frozen and unfrozen areas and should help to better understand linkages between water pathways, sub-lake taliks and permafrost thaw. In addition to the still unaffected areas adjacent to the retreating headwall, the slump-floor areas will also be studied in detail to generate a better understanding of the thermal and hydrological impact of the slumps. The results will be compared with previously collected data from the Peel Plateau and Herschel Island to better understand and compare the mechanisms of different slump types in different environments. Minimally-invasive electrical resistivity tomography (ERT) will be conducted at each field site. Seventy-two small steel rods with a diameter of about 0.8 cm and a length of 40 cm will be pushed into the ground at intervals of 3 meters. These rods will be connected with a cable; the electrical resistivity of the ground at various depths will then be measured. This method allows for the investigation of active layer thickness, subsurface moisture conditions, ground-ice content, and permafrost table topography. For delineation of frozen and unfrozen areas, the use of this method is quite common. All probes placed in the ground are non-permanent and will be removed from the ground once measurements are taken. The electrical currents used by the system are low voltage and will have no impact on plants or animals. Minimally-invasive steel rod probing of the active layer thickness will be conducted at intervals of 3 meters at each sampling location. A steel rod with a diameter of about 1 cm and a length of 120 cm will be pushed into the ground until the permafrost table is reached. This technique allows for the quick measurement of active layer thickness without the need for digging. Each field site will be photographed using a small (under 2 kg), battery-powered, unmanned aerial vehicle (UAV). The in-air-time of this UAV will be approximately 20 minutes for each plot and the UAV will be raised to a maximum elevation of 60 meters (200 ft). The UAV will carry standard photographic equipment (i.e. a camera). The images recorded by the UAV will allow for the creation of a digital representation of the terrain surface and will support the vegetation mapping efforts. The low altitude, small airframe size, and minimal flying time will be minimally disruptive to local wildlife. Further, the UAV will not be used in the presence of wildlife, nor will it be used to photograph or harass wildlife. The drone operator has a valid RPAS certificate. To collect validation data for the three-dimensional, geophysical models, drillings should be conducted in cooperation with members of the NWT Geological Survey. The samples will allow a detailed calibration and provide additional information on ice content and crystallography. The drilling diameter will be only a few centimeters and drilling depth will be a maximum of 3 to 4 m maximum. The environmental impact will be kept as low as possible. The research team plans to contact and inform every NWT stakeholder and community organizations, which are involved in this field work, prior to the campaign. During the stay in the field, the team will communicate their exact plans and any changes to the contact persons at Aurora Research Institute in Inuvik. Following the fieldwork, an annual report is created in which all conducted research activities and the results are described. The fieldwork for this study will be conducted from August 15, 2023 to September 15, 2023.