NWT RESEARCH DATABASE

Tags: physical sciences, permafrost, hydrology, glaciology, prediction models, remote sensing

Objective(s): To develop a suite of models for predicting the response of discontinuous permafrost in the Hay River Lowland to climate warming and human disturbance from oil and gas exploration, and the consequent change in landcover and river flow regime.

Project Description: The long-term goal of this research project is to develop a suite of models for predicting the response of discontinuous permafrost in the Hay River Lowland to climate warming and human disturbance from oil and gas exploration, and the consequent change in landcover and river flow regime. This will be achieved by meeting the following short-term objectives: 1) map the spatial distribution of permafrost and its change over the past 60 years using aerial photography and satellite images, 2) develop conceptual and mathematical models of hydrological processes, 3) develop a new model of permafrost to simulate its response to climate warming and human disturbances, and 4) couple the hydrological model with the permafrost model to predict the spatial distribution of permafrost and the river flow regime under possible scenarios of climate warming and human disturbance. The Scotty Creek research basin, 50 km south of Fort Simpson, NWT is the primary site for process studies and model development. The adjacent Jean-Marie River basin will be used to test the transferability of models within the Hay River Lowland, however no field work will be conducted in Jean-Marie. Water-level recorders will be installed along several seismic cutlines to monitor the propagation of storm pulses along their length and throughout the seismic grid. The water storage capacity of bogs and the connectivity between bogs and fens changes dynamically with water level. Using the high-resolution (1 m horizontal, 0.2 m vertical), Light Detection And Ranging (LiDAR)-derived digital elevation model, the water storage, wetland connectivity, and hydraulic gradients between adjacent wetlands for different water levels will be defined. Using the hydraulic roughness and connectivity, a water-level dependent hydraulic transfer function between grid cells will be developed. An area-average storage function for a grid cell will be defined, based on the statistical distribution of wetland size, geometry, and connectivity indices extracted from the classified image. Permafrost Model Development: a) Field observation of permafrost thaw: Field observations will focus on the receding edges of plateaus. A new 20-m measurement transect perpendicular to the edge of a plateau will be added in the early summer of 2010. Meteorological sensors will be placed in an open (i.e. treeless) bog and below a tree canopy to provide reference data. Several arrays of soil moisture and temperature sensors and ground heat flux sensors will be installed, as well as groundwater monitoring wells along the transect. A similar transect perpendicular to an existing seismic cutline will be installed to examine the effects of linear disturbances on permafrost. Piezometers ranging in depth from 1 m (surface peat) to 4 m (glacial deposit) will be installed in an isolated bog and a fen to examine the dynamics of groundwater flow under recharge (bog) and discharge areas (fen). c) Basin-scale permafrost model development: The Northern Ecosystem Soil Temperature (NEST) model will be modified to simulate discontinuous permafrost. Scotty Creek will be divided into grid cells and, in each cell, the relative proportions of permafrost plateaus, bogs, and channel fens will be defined; as will indices representing the total length of permafrost edges, where the lateral heat transfer between permafrost and non-permafrost occurs. NEST will be modified to include lateral heat transfer due to conduction and advection. Three NEST models will be set-up in a single grid cell (representing plateau, bog and fen surfaces) and run simultaneously so as to include lateral heat transfer among them. Using this method, the model will simulate historical changes in the relative proportion of plateau, bog, and fen, and the permafrost thickness within each landcover type. The model will be run for all grid cells within the Scotty basin to simulate basin-scale permafrost thaw. To test the model, the 1947 permafrost map will be used as the initial condition. The simulated permafrost thaw will be compared with the observed changes in permafrost coverage from the aerial/satellite documentation, including the latest map based on the satellite images from 2010. Model output will also be compared with the temperature profiles measured by the Geological Survey of Canada (GSC) at four 10-20 m deep boreholes within or adjacent to the study area. d) Basin-Scale Model Coupling and Prediction: The basin hydrological and permafrost models will be coupled to simulate the change in stream flow regime as the landscape at Scotty Creek dynamically changes with the thawing of permafrost plateaus. The two models will share common grid cells and will run simultaneously. The hydrological model will feed information on water storage and flow to the permafrost model, while the latter will provide the information on the geometry and areal extent of the permafrost plateaus, bogs, and fens to the hydrological model. The coupled model will be set-up for Scotty Creek and Jean-Marie River to simulate the time period of 1947-2010, and compare the latter with the stream discharge records (1995-2010 for Scotty and 1972-2010 for Jean-Marie) and the time series of permafrost maps. After the model has produced reasonable results for 1947-2010, it will be forced with meteorological data generated by the Canadian Regional Climate Model to simulate the conditions in 2030 and 2050. Guidance to this project will be sought through public consultation with community groups at the villages of Jean-Marie River and Fort Simpson. In the event that fixed-wing (Twin Otter) aircraft transport to the study site is not possible due to poor snow/ice conditions on the lake used for landing, the team will look to local first nation’s communities in the hope of hiring guides that can transport the researchers and their supplies to the camp by snowmobile. This project is also developing a community-based monitoring component within the Cumulative Impact Monitoring Program (CIMP). The researchers continue to host annual community workshops in Yellowknife, and will host a combined CIMP/public meeting in Fort Simpson in March 2012 through collaboration with the Liidlii Kue First Nation (LKFN). Annual reports to the Aurora Research Institute and letters are sent to each supporting community individually that include updates on project activities and copies of key publication / reports from the last 12 months. Project workshops including the annual workshops in Yellowknife are also important means of communication. Informal meetings with communities including First Nations have also proved effective means of communicating. Communication with communities is also facilitated by the Laurier-GNWT Partnership. For example, representatives from the supporting communities are invited to participate at the annual Partnership Workshop in Yellowknife, and information on this project is disseminated through the Partnership's monthly newsletter and website: http://www.wlu.ca/homepage.php?grp_id=12612. The Partnership Liaison (Christine Wenman) also facilitates communication between Partnership projects and community stakeholders. The fieldwork for this study will be conducted from March 15, 2012 to September 15, 2012.