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TitleGround temperature, active-layer thickness and ground-ice conditions in the vicinity of Rankin Inlet, Nunavut
AuthorLeBlanc, A -MORCID logo; Oldenborger, G AORCID logo
SourceCanada-Nunavut Geoscience Office, Summary of Activities 2020, 2021 p. 63-72 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20200673
PublisherCanada-Nunavut Geoscience Office
Mediaon-line; digital
File formatpdf
AreaRankin Inlet; Kivalliq Region
Lat/Long WENS -92.4100 -92.0781 62.8950 62.8031
Subjectssurficial geology/geomorphology; environmental geology; Nature and Environment; Science and Technology; permafrost; ground ice; ground temperatures; climate effects; organic deposits; glacial deposits; tills; soil moisture; drainage; snow; Climate change; Infrastructures; marine nearshore sediments; alluvial sediments
Illustrationslocation maps; tables; profiles; time series
ProgramCanada-Nunavut Geoscience Office, Funding Program
Released2021 01 18
AbstractThe Kivalliq Region of Nunavut is undergoing significant infrastructure development, for which information on permafrost is required to ensure resilience in the context of climate change. Measurements of ground temperature and observations of ground-ice conditions are critical for permafrost characterization but are sparse in the Kivalliq Region. This paper reports on shallow (<3 m) and deep (>6 m) ground-temperature measurements made in the vicinity of Rankin Inlet since 2016. Study site locations were chosen to represent a variety of conditions, including developed and undeveloped land, and different geological settings. Ground-ice conditions are reported upon, where observed. The top of permafrost is ice rich in nearshore marine polygons and in poorly drained alluvial and marine sediments. Although thick lenses of segregated ice are present near the top of permafrost in till, the first decimetres may not be particularly ice rich. The mean annual ground temperature (MAGT) at the top of permafrost ranges between -9.5 and -5.5°C. The MAGT at a depth of close to 7mis approximately -6.7°C in undisturbed ground and approximately -5.5°C in developed land within the Hamlet. Active-layer thickness (ALT) ranges between 0.6-0.7m, under a thick organic layer overlying alluvial-marine sediments, and 1.6minmarine and till sediments. Surface conditions, including soil moisture, drainage and snow cover, are the main factors explaining the ground-temperature differences across the sites. The cold but wet year of 2018-2019 contributed to higher ground temperatures and a thicker active layer. Current MAGT and ALT are both greater than those measured in 1974-1976.
Summary(Plain Language Summary, not published)
Measurements of ground temperature and observations of ground-ice conditions are critical for permafrost characterization but are sparse in the Kivalliq Region of Nunavut. Between 2016 and 2019, two deep (>6 m) and eight shallow (<3 m) ground-temperature monitoring sites were established in the vicinity of Rankin Inlet, including one site within the hamlet. In this paper, the thermal regime of those 10 sites is summarized. Ground temperatures are used to estimate the active-layer thickness, which is the layer above the permafrost that annually freezes and thaws. Frozen cores from the active layer and top of permafrost were also collected and ground-ice conditions are reported upon, where observed. The ground temperatures in Rankin Inlet vary according to the area in which they are taken and strongly depend on surface conditions, including snow cover. At a depth of 7 m, the permafrost temperature varies between -6.7°C, away from town, and -5.5°C, within the hamlet, whereas the active-layer thickness varies between 0.6 and 1.6 m. Ground temperature also varies annually; both warm and dry climate and cold and wet climate led to warmer ground compared to a climate considered as normal (average of 1981-2019). Ice-rich top of permafrost is found in different geological settings under both dry and wet surface conditions. A comparison between the results of this study and historical ground temperatures and active-layer thicknesses from 1974-1976 indicates warmer ground and thicker active layer than those recorded in the past. These new ground-temperature data and permafrost information for Rankin Inlet will be useful for land-use planning and risk mitigation associated with infrastructure management in areas of thaw-sensitive substrate.

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