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TitleAn ecoregional assessment of freezing season air and ground surface temperature in the Mackenzie Valley corridor, NWT, Canada
AuthorSmith, S LORCID logo; Riseborough, D W; Bonnaventure, P P; Duchesne, CORCID logo
SourceCold Regions Science and Technology vol. 125, 2016 p. 152-161,
Alt SeriesEarth Sciences Sector, Contribution Series 20150154
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS85C; 85D; 85E; 85F; 85K; 85L; 85M; 85N; 86C; 86D; 86E; 86F; 86K; 86L; 86M; 86N; 87B; 87C; 95; 96; 97A; 97B; 97C; 97D; 105; 106; 107A; 107B; 107C; 107D; 115A; 115B; 115G; 115H; 115I; 115J; 115O; 115P; 116A; 116B; 116G; 116H; 116I; 116J; 116O; 116P; 117A; 117D
Arealow artic tundra; taiga plains
Lat/Long WENS-140.0000 -116.0000 70.0000 60.0000
Subjectsenvironmental geology; hydrogeology; soils science; Nature and Environment; groundwater; soil properties; soils; permafrost; freezing ground; ecosystems; ground temperatures
Illustrationslocation maps; tables; graphs; equations
ProgramClimate Change Geoscience Land-based Infrastructure
Released2016 05 01
AbstractData from a network of air and ground surface temperature monitoring sites along a transect fromthe lowarctic tundra to the taiga plains and the midboreal forest were utilized to explore latitudinal and temporal trends in various derived temperature indices. Parameters examined include air and ground surface mean annual temperatures, freezing degree-days, as well as freezing n-factors, and timing of the onset and completion of freezing at the ground surface. Temperature data show an N-S trend of about 0.75 °C increase per degree of latitude in the air,while ground surface temperatures increase by 0.9 °C per degree of latitude. Local ranges around the regional trend are between about ±1 °C to ±2 °C in the air and about ±2 °C to ±6 °C at the ground surface, with the range increasing northward for both sets of data. The appropriateness of using a common air-freezing index threshold value as an indicator of sufficient ground freezing for winter construction and transportation activities was investigated by determining the accumulated surface freezing degree-days (FDDS) on the date the air-freezing index reached 300 degree-days. This FDDS value was highly variable and in 20% of caseswas less than 10. These lowvalues reflect a slower rate of the active layer freeze-back, especially formore southerly study siteswhere the value of the freezing n-factor is low(0.1-0.3) and the active layer is thick (1-1.5 m). In the north, analysis shows a substantial range in the freezing n-factor, the greatest range in active layer freeze-back and the highest range in near-surface ground temperatures, suggesting that a single air temperature index is perhaps not appropriate for all sites within the ecoregions examined.
Summary(Plain Language Summary, not published)
To minimize surface and ecosystem disturbance, travel and construction activities in northern Canada often conducted in the winter when frozen ground provides a stable surface. Long-term records of air and near-surface ground temperatures from a network of field sites in the Mackenzie Valley have been analysed to investigate spatial and temporal variability of the timing of ground freezing. Air freezing indices are commonly used to determine when the ground is sufficiently frozen. However, results of this study show that limited ground freezing may have occurred, especially in taiga and boreal ecoregions, when the threshold value for the air freezing index is reached. These results can inform development of guidelines regarding the timing of winter construction and transportation activities. Information is also provided to support infrastructure design and climate change adaptation planning in northern Canada.

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