GEOSCAN Search Results: Fastlink


TitlePermafrost conditions mapping in support to climate change adaptation in Pangnirtung, Baffin Island
AuthorCarbonneau, A S; Allard, M; L'Hérault, E; LeBlanc, A -M
SourceIPY 2012 Conference, From Knowledge to Action, abstracts volume; 2012 p. 1
Alt SeriesEarth Sciences Sector, Contribution Series 20110387
MeetingIPY 2012 Conference From Knowledge to Action; Montreal; CA; April 22-27, 2012
Mediaon-line; digital
File formatpdf
AreaPangnirtung; Baffin Island
Lat/Long WENS -66.0000 -65.5000 66.2500 66.0000
Subjectssurficial geology/geomorphology; environmental geology; permafrost; freezing ground; ground ice; ground temperatures; environmental impacts; environmental studies; climate change
ProgramProgram Management - Climate Change Science, Climate Change Geoscience
AbstractA study of permafrost conditions was undertaken in the Hamlet of Pangnirtung, Nunavut, by the Geological Survey of Canada (GSC) and Université Laval's Centre d'études nordiques (CEN) to support decision makers in their community planning work.The methods used for this project were based on geophysical and geomorphological approaches, including permafrost cores drilled in surficial deposits and ground penetrating radar surveys. Airphoto interpretation was first made to delineate the surficial deposits and the periglacial features. Laboratory analysis allowed a detailed characterization of permafrost in terms of water contents, salinity and grain size.
Radiocarbon dates of shells, buried organic matter and paleosoils from permafrost cores provided a time framework for the accretion of colluvium over the terrain surface and the age of local deglaciation and emergence. Also, cryostratigraphic analysis was done via CT-Scan imagery of frozen cores using medical imaging softwares such as ImageJ. This non-destructive method allows the 3D imaging of the entire core in order to determine the volumetric ice content and also interpret the ice-formation processes that took place during freezing of the permafrost. Our new map of the permafrost conditions in Pangnirtung illustrates that the dominant mapping unit consist of ice-rich colluvial deposits. Aggradationnal ice formed syngenitically with slope sedimentation. Buried soils were found imbedded in this colluvial layer and indicate that colluviation associated with overland-flow during snowmelt occurred almost continuously since 7080 cal. BP. In the eastern sector of town, the 1 to 4 meters thick colluviums cover till and a network of ice wedges that were revealed as regularly spaced hyperbolic reflectors on GPR profiles. The colluviums also cover ice-rich marine silt and bedrock in the western sector of the hamlet; marine shells found in a permafrost core yielded a radiocarbon date of 9553 cal. BP which provides a revised age for the local deglaciation and also a revised marine submergence limit.
Among the applied methods, shallow drilling in coarse grained permafrost, core recovery and CTScan allowed the discovery of the importance of Holocene slope processes on shaping the surface of the terrain and leading to the observed cryostructures and ice contents in the near surface permafrost. Difference in sediment types, ice content and permafrost temperatures will eventually lead to a spatially variable thermal and physical response of the permafrost to climate warming. The ground thermal regime is expected to respond more rapidly to climate warming in the ice-rich colluvial deposits and will lead to significant thaw settlement. Ultimately, results of this study will provide further tools for decision making regarding the expansion of the community in a time of climate warming.