NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: permafrost, pingos

Objective(s): To investigate the three-dimensional internal structure of pingos in the Mackenzie Delta Region.

Project Description: This licence has been issued for the scientific research application No. 5921. This project aims to investigate the three-dimensional internal structure of pingos in the Mackenzie Delta Region. The focus is on small-scale heterogeneities and a detailed delineation of ice-rich or unfrozen areas within, underneath and in close proximity to different pingos. High-resolution, 3D information gathered by geophysical surveying will help to understand the formation and further development of pingos throughout their typical lifecycle. Especially surface-subsurface interactions during the process of permafrost aggradation in drained lake basins and during the development of pingos should be investigated in detail using a combined methodological approach of geophysical surveying, remote sensing and various in-situ data. Also the development of taliks during the lifecycle of pingos but also independent from pingo formation should be investigated to gain further knowledge about water pathways within permafrost and their future development, especially in the context of ongoing global warming. This project is carried out in collaboration with Dr. Peter Morse (Geological Survey of Canada), NWT research license 17466: “Studies of greenhouse gas release and associated environmental processes with thawing permafrost in the Inuvialuit Settlement Region (Application 5797)” (1) Minimally-invasive electrical resistivity tomography (ERT) soundings will be conducted at each field site. Seventy-two small stainless-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. 2D and 3D models of the subsurface can be generated. Especially for delineation of frozen and unfrozen areas the method is quite common. All probes placed in the ground for ERT soundings 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. (2) Minimally-invasive electrical resistivity tomography (ERT) monitoring is planned at two sites. In total seventy-two small stainless-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 1 meter and will remain there throughout the year. Only a small part of the rods will be above the ground surface and will therefore not affect wildlife. Single repeated ERT measurements will be carried out this year and in the following years during fieldwork to investigate the seasonal and interannual changes of frozen and unfrozen parts in the subsurface. Observation of these developments is of high importance in the context of climatic and environmental changes. All probes placed in the ground for ERT monitoring will be removed in the end of the project (scheduled for 2026). (3) Non-invasive ground penetrating radar (GPR) data will be recorded at each field site. The GPR system will be pulled over the ground surface along individual transects. The system works by actively sending electromagnetic pulses into the ground at frequencies of 100 and 200 MHz (i.e. microwaves). The pulses reflect and scatter at layers in the ground that have different physical properties. For example, reflections of the GPR signal will be returned at the permafrost table. GPR allows for a highly detailed measurement of active layer thickness within the upper soil layers (i.e. properties of the subsurface) without the need for digging, thus leaving soils and plants undisturbed. (4) Minimally-invasive steel rod probing of the active layer thickness will be conducted at intervals of 3 meter 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. (5) Each field site will be photographed using a small (under 2 kg), battery-powered, unmanned aerial vehicle (UAV) or a photo-pole. 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 and we have already applied for a SFOC. (6) In cooperation with the Geological Survey of Canada (Dr. Peter Morse), drillings will be performed at several pingo sites (see table above). The drillings will allow a validation of the multi-dimensional geophysical data sets and, in addition, the installation of thermistor strings to monitor the ground temperatures within and below the pingos. The boreholes will be about 5 cm in diameter and up to 10 m deep. Drillings have already been planned for 2023 but had to be postponed due to the wildfire situation in NWT in Aug / Sep 2023. (7) To investigate spatial variabilities in ground thermal regime, small temperature loggers were installed at several sites. The data loggers measure the ground surface temperature in an hourly interval over the entire project period. Loggers installed in 2023 will be read out using a wireless antenna. Some additional small temperature loggers (2 cm x 10 cm) will be installed near the planned equipped boreholes (6). To prevent direct solar radiation, the sensors will be slightly pushed into the ground or below cushions of moss, so that the sensor is located a few centimetres below the surface. After the project, the loggers will be collected and nothing is left behind in the field. The research team plans to contact and inform every NWT stakeholders and community organizations, which are involved in our field work, prior to our campaign. Following the fieldwork, an annual report is created in which all conducted research activities and the results are described. We will shortly apply for a Land Use Permit at the Inuvialuit Land Administration (ILA) via the LUAS system. We received ILA licenses for this and a previous project using the same approach in 2018, 2019, 2022 and 2023. The fieldwork for this study will be conducted from: June 15 - September 30, 2024