In This Space
Permafrost Zone Stability/ frost heaving/discontinuous permafrost
Image credit: Arctic Technology Conference – 2014
Permafrost zone stability products can be delivered from the scale of a licensed project site that has monitoring conditions attached to the license to a regional scale that looks at the total route plan for a pipeline or road infrastructure project. They are useful in the planning stages for infrastructure development, monitoring of infrastructure impacts on permafrost, and monitoring return of permafrost post-decommissioning and remediation. Some guidance is available to industry, such as the Canadian Standards Association standard for moderating infrastructure degradation due to permafrost. Permafrost monitoring is performed with both radar and optical imagery.
Products derived from radar (SAR) imagery:
The main radar derived product is InSAR monitoring on a seasonal and annual basis.
InSAR derived ground deformations will provide seasonal information on the freeze/thaw movement related to the active layer above the permafrost. Correlating these movements annually to determine a yearly trend line will identify zones that are stable versus areas that exhibit overall permafrost deterioration trends.
If archived data are available, a historical trend line would be extremely useful.
Products derived from Optical imagery:
Multi-spectral optical images can be used to generate a surficial sediment map. This is a special form of land cover and incorporates northern land classes such as organics, clays, bedrock, silt, sand/gravel, water, till, etc. Surficial sediment maps highlight stable areas (e.g., bedrock), areas where there is potential to disturb permafrost (i.e., removal of organics), and where existing water bodies present a challenge for infrastructure development.
Permafrost models are important to determine the longer term impacts of warming temperatures on highly susceptible areas. This includes permafrost depth, thickness, and temperature profiles, and surficial cover. The models are developed with field information and extrapolation techniques. Various climate change models are then applied to the permafrost model to determine the likelihood of permafrost degradation with changing air and ground temperatures over several decades.
With the combined EO based analysis and permafrost models, a prediction of the most stable routes or sites can be made for infrastructure development. Predictions can include assessment of the amount of surface removal that the permafrost can withstand, and when climate change would become a factor in ground stability.
The permafrost monitoring product provides colour coded maps indicating relative magnitude of deformations, and stable zones, including correlations with previous years. A report on routing alternatives can be generated. Raster or vector model outputs can also be provided.
Known restrictions / limitations
Highly vegetated or hilly areas can interfere with ground motion estimation and limit the utility of the methods. Another limitation is the ability to correlate seasonal measurements from multiple years to determine annual trends. Areas of persistent snow cover can also present technical issues.
Approaches to mitigate these issues include:
1) Using radar with longer wavelength (e.g., L-band) that provides better penetration of a vegetation canopy;
2) Using existing infrastructure and buildings data to improve the quantity of coherent scatterers;
3) Using shorter repeat cycles (e.g., Sentinel 1); and
4) Multi-year datasets.
The main limitation with optical products is the short growing season in cold climates, and therefore the availability of suitable data sets for sediment maps. The use of Landsat-8 with Sentinel 2 will help mitigate this issue with additional images over the area of interest.
The permafrost models are typically derived from surface geophysical measurements. These can be expensive and therefore control sites must be carefully chosen and surface/sub-surface lithology correlations must be used to extrapolate site measurements over wider areas. Some of these formation maps are available from local Geoscience offices.
Lifecycle stage and demand
Pre-License: Information on historical deformation zones to support identification of high risk areas. Also new monitoring programs to capture several years of deformation maps and routing options. Generation of baseline trends of ground deformation are a major capital cost driver at this stage, and influence the likelihood of regulatory approvals.
Exploration: Information from assessments made during the Pre-license stage support mitigation measures that could be implemented and tested for high risk areas (river crossings, critical habitat, etc.).
Development: Information from assessments made during the Pre-license stage support design for areas of concern and further evaluation of mitigation strategies.
Production: Information from assessments made during the Pre-license stage support monitoring for areas of concern.
Decommissioning: Baseline information supports return to stable permafrost regimes or identification of deterioration due to climate change.
Geographic coverage and demand
Coverage and demand is for northern development globally in both continuous and discontinuous permafrost zones.
Input data sources
Optical: HR1, HR2
Radar: HR1, HR2
Spatial resolution and coverage
Spatial resolution: 10 m radar and optical imagery is adequate to highlight areas of active movement and areas of consistently standing water that impact permafrost.
Coverage: Over hundreds of km up to several thousand km.
Minimum Mapping Unit (MMU)
National map sheet scales for initial planning of options, then route specific or site specific scales.
Accuracy / constraints
Deformation accuracy: High relative accuracy within the area of interest is the most important factor.
Thematic accuracy: 80-90%.
Spatial accuracy: The goal would be 1 pixel, but depends on reference data used (i.e., range in metres corresponding to input data).
Accuracy assessment approach & quality control measures
Control sites with borehole sampling, field sampling, and manual surveys.
Frequency / timeliness
Observation frequency: deformation maps at a maximum of 24 days. 10 days preferred during freeze/thaw cycles.
Timeliness of delivery: It is important to capture permafrost status immediately prior to spring thaw and continue the monitoring until after the fall/winter freeze-up; however due to the potential for highly active areas a short revisit is required during the thaw/freeze timeframes. Seasonal maps can be completed during the winter season.
On-demand availability from commercial suppliers. New acquisitions can be requested globally.
Archived products are available for public search. Availability may be limited for specific dates.
Delivery / output format
Peer Reviewer: OTM/TRE
Permafrost Zone Stability/ frost heaving/discontinuous permafrost / Historical Surface Deformation
# of Pages:
Internal – Project consortium and science partners
External – ESA
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