NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: physical sciences, permafrost, discontinuous permafrost, infrastructure planning, community development

Objective(s): To characterize, model and predict permafrost occurrence under varying terrain types and environmental disturbances. Investigations will examine permafrost conditions across environmental transitions at a scale relevant to community and industry infrastructure planning.

Project Description: This activity describes and predicts the occurrence of discontinuous permafrost in the northern Great Slave Lake region to assist in planning, development and maintenance of community and industry infrastructure. Changes in climate are affecting permafrost distribution, temperatures and geotechnical conditions. Different landscapes across the region are exhibiting varying responses to warming. This study collects ground temperature and environmental information to describe the state of permafrost in the area. Supporting data from climatic, soils, vegetation, lakes and hydrological surveys assist in characterizing permafrost distribution. The broad objective is to characterize, model and predict permafrost occurrence under varying terrain types and environmental disturbances. Investigations will examine permafrost conditions across environmental transitions at a scale relevant to community and industry infrastructure planning. Sites are to be selected to characterize the range of permafrost conditions. Local site conditions capture variations in ground temperature conditions across transitions from thick unconsolidated deposits to bedrock, and with proximity to water bodies. Interested parties are consulted, to ensure that sites yield the most locally relevant data. Study design involves instrumentation of thermistors at undisturbed locations within a designated unit, then placing additional thermistors with proximity to adjacent lakes, and along transitions of thinning overburden towards adjacent bedrock outcrops. Near-surface thermistors are instrumented to describe active-layer conditions and freezeback characteristics of respective sites. Bedrock sites may be instrumented opportunistically where exploration or geotechnical investigations are or have taken place. Active layer thicknesses are measured at each site. Active layer and near-surface permafrost samples are obtained for each of the terrain units (with exception of bedrock) to depths of up to 6 m using a 5 cm diameter Cold Regions Research and Engineering Laboratory (CRREL) core barrel. Core samples are analysed for geotechnical and geochemical properties at Taiga Environmental Laboratory in Yellowknife. Surficial geological and ecological data are collected to describe site conditions. Vegetation description includes species and height, ground cover and organic matter thickness, if applicable. Near surface soil samples describe moisture conditions. Seasonal snow accumulation is measured. Ground temperatures across transitions are analyzed along with supplementary data on site conditions so that factors controlling local scale variability in temperature characteristics and sensitivities to thawing are determined. Ground ice conditions are described for the respective terrain units and relations between ice content and environmental variables assessed. An assessment of ground ice volumes in the upper 3 m is made. Models are developed to explain variabilities in temperature and ground ice distributions with a goal towards mapping permafrost distribution and ground thermal conditions, ground ice distribution based on classification of remotely sensed imagery and terrain sensitivity. The project works with communities through the Northwest Territories Geoscience Office and the Cumulative Impact Monitoring Program to implement a community-based monitoring program with a focus on protocols for monitoring climate, soils, vegetation, hydrology and permafrost. Educational opportunities include local excursions to active field sites in Yellowknife and Dettah area, as has been conducted previously by the investigators. Research has supported involvement of local students, government, industry and academic personnel. The results of this work are communicated to NWT communities through workshops organized through the Cumulative Impact Monitoring Program, NWT Chamber of Mines, and Northwest Territories Geoscience Office. The research is also communicated to groups and agencies responsible for managing infrastructure and regulating land and water use. Public lectures and local field tours are also used to communicate results to community and professional stakeholders. Training opportunities with local schools and Aurora College are facilitated as knowledge transfers to NWT residents. The fieldwork for this study will be conducted from February 13, 2016 to September 26, 2016.