|Title||Permafrost modelling in the Mackenzie Valley|
|Download||Download (whole publication) |
|Licence||Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences.|
Ednie, M; Wright, F; Côté, M; Riseborough, D|
|Source||Permafrost science at ESS: a workshop on GSC/CCRS scientific opportunities; by Wolfe, S A (ed.); Geological Survey of Canada, Open File 6531, 2010 p. 10-11; 1 CD-ROM, https://doi.org/10.4095/263375 Open Access|
|Publisher||Natural Resources Canada|
|Meeting||Workshop on GSC/CCRS Scientific Opportunities; Ottawa, ON; CA; November 26, 2009|
|Media||CD-ROM; on-line; digital|
|Related||This publication is contained in Permafrost science at ESS:
a workshop on GSC/CCRS scientific opportunities |
|NTS||95; 96; 106; 107|
|Lat/Long WENS||-134.0000 -120.0000 68.0000 61.0000|
|Subjects||surficial geology/geomorphology; engineering geology; Nature and Environment; permafrost; freezing ground; ground ice; ground temperatures; terrain sensitivity; terrain types; terrain analysis; arctic
geology; modelling; mapping techniques|
|Released||2010 01 01|
|Abstract||The actual distribution and character of permafrost across Canada is poorly understood and in most cases is represented by the highly generalized Permafrost Map of Canada which describes only broad
zones of continuous, discontinuous, or sporadic permafrost. While this map is useful for visualization on a small scale (eg 1:7 000 000), it is inadequate for addressing climate change issues because it contains no information about the actual
distribution of frozen vs. unfrozen ground, probable ranges of ground temperature, or local/regional variations in permafrost thickness. Modeling at small scale (1 km resolution) may be suitable for policy development, but intermediate scale modeling
(30 m resolution) is more appropriate for planning purposes. High-resolution information about permafrost and associated geotechnical characteristics is required by engineers, regulators, and community stakeholders responsible for assessing potential
risks to infrastructure and traditional northern lifestyles in the face of climate change. |
The Geological Survey of Canada has developed transient numerical modeling to help estimate the current distribution and thickness of frozen ground in the
Mackenzie River valley and to generate time-series predictions of future impacts to permafrost under a progressively warming climate. A one-dimensional finite element heat conduction model (T-ONE), integrated into an ArcGIS spatial analysis platform,
enables pseudo 3-dimensional modeling of ground thermal conditions across extensive geographic areas.
Ground and surface temperatures from instrumented boreholes and active layer measurements were used to calibrate the model and validate outputs.
The model is physically-based, incorporating key climate and terrain factors considered to exert significant influence on the ground thermal state.
Current permafrost characteristics as well as predictions of possible impacts of climate change
are necessary for engineers and decision-makers who are responsible for the maintenance and planning of infrastructure projects. This model was used to predict current ground thermal conditions and permafrost characteristics along NWT highways and
roads, and potential climate-induced changes to permafrost that may be realized over practical engineering time frames. These predictions were used to identify areas within the transportation corridors that would have significantly greater thaw
depths leading to possible subsidence and terrain instability.
The application of transient numerical modeling to geo-statistical methods can be used to generate secondary knowledge products. Using a Weight-of-Evidence based landscape-process
model, multiple terrain factors such as geology, permafrost, topography/topology and surface hydrology are used to identify and map terrain susceptibility to various types of terrain instability, including retrogressive thaw flows and rotational
slides. For the T-ONE transient results, limited ground truthing and statistical validation of modeling outputs have established a reasonable level of confidence in model performance within the broader Mackenzie Valley. Several data and knowledge
gaps remain, such as surface organic layer thickness and properties, snow cover, up to date forest fire distribution, as well as location and persistence of air temperature inversions. Also, the correlation between geomorphologic units
andmoisture/ice content is mostly based on expert knowledge. A more rigorous approach to quantify the amount and distribution of frozen and unfrozen water at various scales would help resolves some latent heat issues.