NWT RESEARCH DATABASE

Tags: physical sciences, water quality, permafrost, climate change, thaw slump

Objective(s): To obtain information, on sediments collected from retrogressive permafrost thaw shoreline slumps affecting numerous Arctic tundra lakes in the Mackenzie Upland Region east of the Mackenzie Delta.

Project Description: The overall goal of this study is to obtain information, through laboratory experiments (rainfall simulator; 2m annular flume) on sediments collected from retrogressive permafrost thaw shoreline slumps affecting numerous Arctic tundra lakes in the Mackenzie Upland Region east of the Mackenzie Delta, on the physical processes through which slump material is transported and delivered to a receiving lake. This information is crucial for development and optimization of appropriate physically-based sediment transport algorithms for improving modelling capability of the potential impacts on tundra lakes of increasing permafrost thaw shoreline slumping under a warming climate. Field Collection of Permafrost Slump Material: In September, 2017, a field crew will visit the slump on Lake 5B (. Transportation to and from the site will be by helicopter on skids out of Inuvik. A total of five containers, about 19 L per container, of sediment will be removed from the slump for laboratory experiments simply using a shovel. Atotal of about 95 L (less than 1 cubic meter) of slump material will be collected. The collected slump material will be shipped to the Environment and Climate Change Canada Hydraulics Lab located at the Canadian Centre for Inland Waters (CCIW) in Burlington, Ontario. Laboratory Experiments – Rainfall Simulator: Utilizing the newly engineered and fully operational rainfall simulator at CCIW, crucial information required for development of appropriate modelling algorithms for runoff generation and sediment transport will be obtained (e.g., threshold rainfall amounts before surface flow is initiated, flow velocities required to entrain slump material, importance of splash detachment and surface sealing on flow and sediment transport, etc.). The rainfall simulator has been calibrated using a variety of spray nozzles, which allow for simulating rain events typical for the western Arctic ranging from relatively low rainfall intensities for relatively longer periods of time (frontal rain events) to high intensity shorter duration events typical of thunder storm activity (convectional rain events). Using the material collected from the slump on Lake 5B, determine the physical, chemical and biological dynamics of sediments eroded using a variety of rainfall intensities and durations (rainfall intensities and durations dictated by climate change modelling predictions) coupled with various levels/rates of thaw. It is notable that we will have to ability to rain on frozen or partly frozen material, as well as fully thawed material (with the degree of thaw artificially controlled by refrigeration). Laboratory Experiments – 2m Annular Flume: Using runoff collected from the rainfall/thaw simulations, the physical, chemical and biological dynamics of particulate material delivered to the lake will be determined (using the 2m annular flume connected with the rainfall simulator). The flume work will provide key information on under what conditions in the lake do the various fine-grained slump sediment fractions settle out of the water column and become deposited on the lake bed – and conversely, under what energy conditions in the lake can the lake bed sediment become re-entrained into suspension (e.g., due to wave action). In addition, flume experiments will be run on the “parent” slump material to see how it behaves in the lake water if it were input directly from the slump to the lake (for example, via shoreline collapse directly into the lake), rather than transported to the lake through snowmelt/rainfall - surface runoff - sediment transport processes. There will likely be opportunities for Northerners to be trained to assist with fieldwork (monitoring rainfall/runoff and shoreline permafrost thaw slump sediment delivery to tundra lakes). Northerners (northern students; community members; etc.) to assist in the field program will be identified through the Inuvialuit Joint Secretariat and the Aurora Research Institute. Wildlife Monitors will be utilized when necessary. To communicate results to individuals and communities, the research team plan to hold community-based meetings and consultations in northern communities to inform local residents in the region of the nature and significance of the research, what the team are trying to find out and why, and to provide updates on what has been learned (key findings) as the work progresses. Information will also be made available through such things as posters, brochures, fact sheets, journal publications, etc. The fieldwork for this study will be conducted from September 1, 2017 to September 30, 2017.