ABSTRACT: -Integrated geophysical approach for the detection and assessment of ground ice at Parsons Lake, NWT and Herschel Island, YT.

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The mapping of ground ice distribution is fundamentally important for natural resource development in the Arctic, because the melting of ice within permafrost destabilizes the ground, which could lead to the destruction of infrastructure. Although borehole drilling provides accurate information, the process is expensive, time consuming, and only generates point samples. Surface based geophysical techniques, however, are non-destructive,relatively cheap, and can survey a large area. My research focuses on the detection and characterization of ground ice using ground-penetrating radar (GPR) and capacitively coupled resistivity (CCR) at Parsons Lake, NWT, anatural gas fi eld 75 km north of Inuvik. Using detailed borehole logs from March 2004, the fi rst phase of my MSc is to evaluate how well geophysical tools predict ice content under various ground thermal regimes, ground icestructures, and enclosing sediments. Fieldwork activities were conducted at Parsons Lake in winter 2010, as well as summers 2009 and 2010. Preliminary graphs showing the relationship between electrical resistivity and ice content(measured gravimetrically) in summer reveal clusters of points associated with varying types enclosing materials, including ice, peat, as well as coarse-grained and fine-grained sediments. The scattering of points within clusters can be partially explained by the fact that additional environmental factors like ground temperatures control resistivity values, especially in summer. In summer, warmer ground temperatures lead to a greater prevalence of unfrozen water content. Further analysis shows that the range of ice content is high for values of high resistivity and low ground temperatures. Hence, one can be observing enclosing sediment types of ice, ice/coarse, or coarse material.Current results, however, demonstrate that GPR is capable of mapping contacts between the aforementioned materials. On the subject of seasonal changes, it is clear that there is a better relationship between resistivity and ice content in winter rather than summer. This could be due to the fact that in winter, ground temperatures are much lower, and hence, the prevalence of unfrozen water content is reduced. For all summer data points (includes all enclosing sediments as one group), ground temperature is signif cant at 95% confi dence. For all winter data points, the natural log of ice content is signifi cant for 95% confi dence. Due to changes in the prevalence of unfrozen water content, there is a seasonal shift in terms of which variable is most important in controlling resistivity. Multiple regression models including the aforementioned variables produce R-squared values of 0.57 and 0.50 for summer and winter respectively. In order to improve the model, quantitativeestimates of unfrozen water content will be made. In order to accomplish the latter, the borehole data must be used in conjunction with Inuvik weather data from 2010 to generate a ground thermal regime model for 2010. Secondly, GPR must be applied to quantify ice structure, which affects unfrozen water connectivity, and thus, electrical resistivity. The knowledge gained from Parsons Lake will be used to help model thermokarst development adjacentto retrogressive thaw slumps on Herschel Island, Yukon Territory

Bibliography of Canadian Geomorphology