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TitleMonitoring changes in unfrozen water content with electrical resistivity surveys in cold continuous permafrost
AuthorOldenborger, G A; LeBlanc, A -M
SourceGeophysical Journal International vol. 215, issue 2, 2018 p. 965-977,
Alt SeriesNatural Resources Canada, Contribution Series 20170326
PublisherOxford Academic
Mediapaper; on-line; digital
File formatpdf; html
AreaCanadian Arctic; Iqaluit
Lat/Long WENS -68.5622 -68.5458 63.7606 63.7567
Subjectssurficial geology/geomorphology; environmental geology; geophysics; Transport; engineering geology; permafrost; thermal analyses; modelling; geophysical surveys; electrical resistivity; ground temperatures; ground ice; groundwater movement; salinity; in-field instrumentation; climate, arctic; unfrozen water content; permafrost thaw; permafrost degradation; monitoring; infrastructures; airports; data processing; electrical resistivity tomography; climate change; lacustrine veneer; glaciofluvial outwash plain sediments; glaciomarine deltaic sediments; till blanket; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; photographs; profiles; plots; models; time series; cross-sections
ProgramPermafrost, Climate Change Geoscience
Released2018 08 08
AbstractFor permafrost, information on unfrozen water content is critical for thermal modelling, understanding permafrost evolution and for predicting thaw susceptibility for infrastructure. We utilize electrical resistivity surveys for the detection and monitoring of unfrozen water content in cold continuous permafrost. We develop a data processing scheme based on a common subset of reciprocal measurements to filter data from irregular acquisitions in variable environmental conditions to a standard noise level, such that models recovered from disparate data sets can be compared quantitatively. Using temperature-corrected post-inversion model differencing, changes in recovered electrical resistivity models are used to calculate the relative change in unfrozen water content over common regions of high model resolution. The technique is applied to electrical resistivity data collected seasonally using a permanent electrode installation in cold continuous permafrost alongside airport infrastructure in the Canadian Arctic. The number of healthy data decreases over the experiment duration, with a correlation between data quality and ground surface temperature. Using the resistivity models, relative changes in unfrozen water content are estimated that are consistent with temperature records. Results are compared to an empirical temperature-dependent water content model obtained via calibrated thermal modelling at the study site. When compared to the empirical model, the changes in resistivity overpredict the changes in unfrozen water content due to temperature-induced phase changes alone after one year of acquisition. Prevalent changes in unfrozen water content occur in a zone below the active layer at temperatures of approximately 0 to -4.5 °C, and may be indicative of permafrost evolution involving ice formation or water movement over many months in moderately-saline permafrost beneath airport infrastructure.
Summary(Plain Language Summary, not published)
Permafrost is perennially frozen ground. Permafrost properties such as the amount of unfrozen water are critical for thermal modelling of the response of permafrost to climate forcing, understanding contaminant flow and transport, or for predicting the behaviour of permafrost as an engineering substrate. We utilize geophysical surveys to monitor changes in unfrozen water content for cold continuous permafrost at Iqaluit International Airport in the Canadian Arctic from 2012/08 to 2015/06. We develop a novel data processing scheme and calculate changes in unfrozen water content that appear consistent with temperature records and can be used to monitor active permafrost processes and evolution.