NWT RESEARCH DATABASE

Tags: physical sciences, environmental assessment, geology, permafrost, glaciology, treeline

Objective(s): “Environmental Studies across Treeline (ESAT) in the Mackenzie Delta region” is a northern based collaborative program with an objective to enhance the understanding of environmental conditions in the Mackenzie Delta region through scientific studies and monitoring.

Project Description: “Environmental Studies across Treeline (ESAT) in the Mackenzie Delta region” is a northern based collaborative program with an objective to enhance the understanding of environmental conditions in the Mackenzie Delta region through scientific studies and monitoring. Specific studies include: 1) monitoring permafrost conditions in the Mackenzie Delta region; 2) examining freeze-back of the active layer and associated strength properties of freezing soil; 3) examining the influence of shrub removal on frozen ground and snow conditions at abandoned drilling-mud sumps; 4) investigating the effectiveness of different soil sampling protocols on delineating contaminants in permafrost soils; 5) monitoring the water quality of tundra lakes; and 6) examining the ground thermal regime near proposed Mackenzie Gas Pipeline stream crossings. This project is a multi-year project and is the continuation of previously approved work. Where possible, to reduce the environmental impact, time and travel costs, multiple sites will be visited in a single trip to an area. 1) Permafrost Monitoring: At each site, shallow temperature cables have previously been installed in the active layer, and near-surface permafrost and air temperatures are recorded by data loggers. Cables up to 20 m depth measure the permafrost temperatures. Snow depth and density are measured along 70 m transects using snow probes. Field sampling at some sites may also involve the collection of near-surface permafrost and active layer soil samples (approximately 100 g) using a hand held portable auger. The samples will be analysed for ice content and soil chemistry, which will help us understand baseline soil and permafrost conditions and the sensitivity of terrain to disturbance. The field itinerary includes: - Day visits to record ground temperatures and snow characteristics in late March. - Day and possibly overnight visits to record ground temperatures during late August. - Day visits to record ground temperatures in early November 2) Active layer freezeback: Examining freeze-back of the active layer and associated strength properties of freezing soil. Two study sites were established in four terrain types of the outer Mackenzie Delta. The objective is to understand how the active layer freezes back in the winter. Sites that freeze back more slowly may be more sensitive to impacts from overland winter travel. Each site consists of six 20 m transects along which snow conditions, ground hardness, active-layer thickness, and vegetation cover are measured. Shallow (1 m) ground temperature cables were previously installed in the active layer. Meteorological stations were set up at Harry Channel and Fish Island to continuously measure climate data including air temperature and snow. The field itinerary includes: - Sites will visited in late August to download ground temperatures and meteorological station data, and to measure the active layer and vegetation cover. - Sites will be visited to measure snow conditions and ground hardness on a monthly basis from October to March, with each visit lasting less than several hours. - In fall 2010 a Snowcat will be used to pack snow over the site to simulate building an overland winter road. Environmental conditions along the transects will be measured in the following summer to determine if there were any effects. 3) Shrub removal: Examining the effects of shrub removal on the ground-thermal regime of drilling-mud sumps. Many drilling-mud sump caps revegetate with tall shrubs that retain snow, leading to warmer ground temperatures and potentially thawing sump contents. The objective of this work is to determine the thermal effect of removing tall shrubs from a sump cap. We hypothesize that shrub removal will lead to cooling of the sump cap. This shrub removal technique may be useful for the long term management of sump integrity. Two sumps were instrumented with shallow (1 m) ground temperature cables in summer 2009. Following discussions with Imperial Oil we will remove tall shrubs on one of the drilling-mud sumps. We plan to cut and remove the shrubs in summer 2010. Snow depths and ground temperatures will be measured on a monthly basis during the winter months. The field itinerary includes: - Sites will be visited in late August 2010 to cut and remove the shrubs. - Sites will be visited monthly during the winter to measure snow depths. 4) Contaminant movement. The objective of this work is to determine an appropriate soil sampling study design to evaluate salt contamination in areas of patterned ground (ice-wedges and hummocks). This design will be used to delineate movement of salts from spills or unfrozen sumps. Soil sampling has previously been conducted near 11 sumps in patterned ground of the Mackenzie Delta. Results have shown greater concentrations of salt contaminants in trough features, indicating that soil sampling designs should account for differences in microtopography. To test this hypothesis in a field setting, in summer 2010 an environmentally benign tracer (lithium chloride) will be applied at the Navy Road quarry. Soil samples will be taken prior to the tracer application and at monthly intervals afterwards to determine contaminant pathways. Field methods will include the collection of about 25 small (100 g) soil samples using a hand auger. The field itinerary includes: - The site will be visited for tracer application and soil sampling one day in June, July and August 5) Tundra Lakes: Monitoring lake water quality The research team is monitoring the influence of natural disturbance (thaw slumping) on the water quality of tundra lakes. Fieldwork includes the collection of several small soil samples (100g) using a hand auger, and the collection of lake water samples (<1 L) at each study lake. - Lakes will be visited in late March to collect water samples. - Lakes will be revisited in late August to collect water samples, and soil samples at some lakes. 6) Stream Crossings: Investigation of permafrost conditions at stream crossings along the proposed MGP corridor. Each site is instrumented with 2 deep ground temperature cables (15 m deep), 4 shallow temperature cables (1.5 m deep) and two in-stream water temperature loggers. The deep ground temperature cables are installed using a water jet drill system, which uses a fire pump and 3/4” steel piping to concentrate the water flow so that it may be used to drill into the ground. The shallow thermistors are installed using a hand drill, and the in-stream loggers are installed in waterproof containers and are weighted down to lie on the bottom of the stream bed. We also measure vegetation height and snow depth on a transect across each of the streams, taking measurements every 5 meters. Over the past year, researchers of the ESAT program have been involved in the establishment of community-based environmental monitoring sites in partnership with the Inuvialuit Joint Secretariat. We plan to partner with the Gwich’in in 2010/11 to implement a community-based monitoring program. The fieldwork for this study will be conducted from March 15, 2010 to December 31, 2010.