Fine-Scale Ground Surface Vertical Displacement and Soil Water Processes in the Canadian High Arctic

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Mcfadden, Sarah
permafrost , Arctic , soil water , ground surface vertical displacement
The fine-scale physical response of soils to thaw, ice content and soil water conditions in the High Arctic are poorly understood. This thesis introduces the topic and identifies knowledge gaps in the literature and secondly, addresses these gaps through the investigation of the spatiotemporal relationship between ground surface vertical displacement (GSVD) and active layer water level conditions during the summer thaw season at the Cape Bounty Arctic Watershed Observatory, Nunavut. GSVD and water level were monitored simultaneously at five measurement stations consisting of a new inclinometer system (accuracy ±0.15 mm) and a shallow subsurface well logged with pressure transducers. Diel cyclicity in both GSVD (± 0.5 mm) and water level (± 0.2 m) was present at two of the stations and synoptic scale variability characterized the others. The records indicate a close association between GSVD and water level at multiple short-term time scales. Active layer soil physics appear to be controlled by soil water content on both synoptic and diel timescales. Ground ice thaw appeared to be the primary source of water within the diel systems, while synoptic variability was associated with rainfall events. The diel systems were inferred to be primarily driven by large-scale (>258 m2) upslope contributing areas which facilitated diel water level and GSVD fluctuations due to the amplification of thaw-derived water accumulation downslope. These results improve our knowledge of the physical response of High Arctic soils to changes in soil water conditions and active layer thaw, critical for future landscape stability monitoring and geohazard prediction.
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