The majority of high-latitude Arctic land surface is underlain by permafrost. The high degree of permafrost sensitivity from climatic as well as anthropogenic factors leads to surface deformation and changing active layer. This is typically due to thawing in warmer seasons and refreezing in colder seasons. Such changes can have significant impacts on the infrastructure and hydroecological environment. Hence, the objectives of this study aimed at identifying spatial pattern and magnitude of surface deformation (uplifting and subsidence) from 2015 to 2018 using Sentinel-1A images in an army installation – Donnelly Training Area (DTA), Alaska. To achieve the objectives, Interferometric Synthetic Aperture Radar (InSAR) method was applied to 11 descending Level-1 Single Look Complex (SLC) images in thawing seasons, spanning from 8th May 2015 to 25th September 2018 with perpendicular baseline up to ±90 m. A Digital Elevation Model (DEM) of 30 m spatial resolution was employed to remove the phase contributed by altitude, to increase the accuracy of differential interferogram and for geocoding. Multilooking, Goldstein phase filtering and phase unwrapping using Minimum Cost Flow (MCF) were conducted on the resulting phase. The unwrapped phase was converted into displacement and it was then terrain-corrected. The collocation of terrain-corrected coherence and displacement was applied followed by the extraction of displacements in the areas where coherence exceeded 0.4 and the displacement was interpolated. Wilcoxon’s signed ranked test was conducted to test if the median displacements were significantly different from zero. The results showed seasonal deformation ranging from -0.43 meter to +0.34 meters. Subsidence was commonly observed between June and July when temperature was high and, uplifting was noticed as a prominent phenomenon after July and before June due to the expansive nature of silty soil and clays. However, the secular changes from May 2015 to May 2018 showed subsidence as a major phenomenon. This could be attributed to the thawing of ice-rich permafrost underneath probably due to global warming and military training activities. Deformations in all pairs were found to be significantly different from zero. These results corroborate with deformation studies conducted in other parts of Alaska and these findings are useful to researchers, decision-makers, and planners of land management.

Permanent electrode arrays were set up at ten monitoring sites from Whitehorse, Yukon, to Fort St. John, British Columbia, in order to gain a clearer perspective of the effectiveness of electrical resistivity tomography (ERT) monitoring over an annual cycle of freezing and thawing. This research forms part of a longer-term project that is attempting to use ERT to examine changes in permafrost resulting from climate change. Inter-site and intra-site variability were examined by installing and maintaining data-loggers to monitor active layer and shallow permafrost temperatures, air temperatures, and snow depths at each site from August 2010 – August 2011. Additional site information was collected on each ERT survey date, including frost table depths, snow depths, and vegetation heights. Based on nearby community records, the climate in the region has been warming by a rate of 0.3 to 0.5 °C per decade since 1970. The permafrost at all ten sites was characteristic of sporadic discontinuous and isolated patches permafrost zones, and is classified as Ecosystem-protected. Nine of the ten permafrost sites had permafrost that was thinner than the 14 or 7 m penetration depth of the ERT survey (three-layer system consisting of an active layer, permafrost, and sub-permafrost perennially unfrozen zone). The most predictable results were achieved at the two-layer system site (active layer overlying permafrost to the base of the profile) in each of its virtual resistivity boreholes, relative resistivity change comparisons, and mean near-surface apparent resistivity progressions. ERT is an effective method of delineating permafrost boundaries in thin permafrost environments and does show strength when monitoring areas of seasonally frozen ground. Repeat surveys at a site indicate seasonal changes in three-layer conditions, but not as predictably as those in a two-layer system. In order to receive the most accurate information regarding permafrost extent and thickness, it appears ideal to conduct ERT surveys annually, within the same month as the previous year’s survey.

The objective of this study was to determine the dominant biogeochemical controls on mercury partitioning in super-permafrost groundwater at Truelove Lowland, Devon Island, Nunavut. Mercury partitioning in snow, ephemeral standing water, and super-permafrost groundwater was investigated. <p>Results indicate that partitioning differs between matrices, and that particulate mercury is spatially and temporally dynamic in Truelove Lowland groundwater. Particulate mercury in groundwater was 73 % of total mercury, while snow had only 22 % particulate mercury. Particulate mercury in groundwater rose by over 20 % from Julian day 181 to 189, and decreased slightly on Julian day 191. No single geochemical parameter was a good predictor of particulate mercury concentrations. To expand upon the findings of the field study a laboratory microcosm study was conducted to determine whether certain biogeochemical processes influence mercury partitioning in super-permafrost groundwater. Particulate mercury in the dissimilatory iron reducing bacteria inhibited microcosm was 61 % of total mercury, approximately 18 % lower than in all other treatments. Iron (III) concentrations had a positive correlation with particulate mercury while chloride concentrations had a negative correlation with particulate mercury. Sulfate reducing bacteria were not found to influence mercury partitioning.

This study investigates how the estimated thickening of the active layer will affectthe soil organic carbon in permafrost soils. The focus lies on estimating how muchof the upper permafrost soil organic carbon will be affected by the active layerdeepening due to global warming, on what timescale the deepening will take placeand if the estimated changes differ depending on the extent of permafrost in theregion. A model made in a Geographic Information System (GIS) combines datasetsfrom The Northern Circumpolar Soil Carbon Database, field data of soil organiccarbon content (SOCC) in different permafrost soil horizons in the Usa basin anddata of recent and future active layer depth from a spatially distributed permafrostdynamics model in the Pechora River Basin. The model shows that in 1980, 75% ofthe available 0–100 cm Gelisol soil organic carbon mass (SOCM) has affected byseasonal thawing. In 2050 the proportion is increased to 86% and by 2090 almostthe whole study area has an active layer deeper than 1 meter (98%). This indicatesan increase from approximately 0.64% to 0.84% of the total 1–100 cm SOCM in thenorthern permafrost region. The change is more gradual in the isolated and thesporadic permafrost zones and more abrupt in the continuous and discontinuous regions.

The objective of this study was to determine the dominant biogeochemical controls on mercury partitioning in super-permafrost groundwater at Truelove Lowland, Devon Island, Nunavut. Mercury partitioning in snow, ephemeral standing water, and super-permafrost groundwater was investigated. <p>Results indicate that partitioning differs between matrices, and that particulate mercury is spatially and temporally dynamic in Truelove Lowland groundwater. Particulate mercury in groundwater was 73 % of total mercury, while snow had only 22 % particulate mercury. Particulate mercury in groundwater rose by over 20 % from Julian day 181 to 189, and decreased slightly on Julian day 191. No single geochemical parameter was a good predictor of particulate mercury concentrations. To expand upon the findings of the field study a laboratory microcosm study was conducted to determine whether certain biogeochemical processes influence mercury partitioning in super-permafrost groundwater. Particulate mercury in the dissimilatory iron reducing bacteria inhibited microcosm was 61 % of total mercury, approximately 18 % lower than in all other treatments. Iron (III) concentrations had a positive correlation with particulate mercury while chloride concentrations had a negative correlation with particulate mercury. Sulfate reducing bacteria were not found to influence mercury partitioning.

Arctic ecosystems are experiencing rapid changes as a result of climate warming and more frequent natural and human-caused disturbances. Disturbances can have particularly large effects on high-latitude ecosystems because ecosystem structure and function is controlled by strong feedbacks between soil conditions, vegetation, and ground thermal regime. My MSc. research used fieldwork and broad-scale GIS data to investigate post-disturbance ecosystem recovery along roads in two permafrost zones (discontinuous and continuous). In the first of two case studies, I focussed on tall shrub proliferation along the Dempster Highway at the Peel Plateau, NT. To explore the drivers of tall shrub proliferation and to quantify shrub expansion in this region of continuous permafrost, greyscale air photos (1975) and Quickbird satellite imagery (2008) were used to map landcover change within a 1.2 km buffer next to the road and inside a buffer 500 m away from the road. Extensive tall shrub proliferation in the study area indicates that warming air temperatures and disturbance both facilitate vegetation change in tundra environments. My findings also indicate that accelerated shrub expansion adjacent to the road was caused by increased soil moisture. Tall shrub proliferation adjacent to the road occurred at lower elevation sites characterized by wetter soils with thicker organic layers. Areas that resisted tall shrub encroachment were located at higher elevations and had drier soils with thin organic layers. These observations also support previous work that illustrates that tall shrub expansion next to the highway promotes strong positive feedbacks to ongoing shrub growth and proliferation. In a second case study I examined ecosystem recovery in an area of discontinuous permafrost 30 years after construction and abandonment of a winter access road in Nahanni National Park Reserve. Ecosystem recovery was studied by comparing disturbed (road) and undisturbed (adjacent to the road) sites in spruce muskeg, black spruce parkland, deciduous forest, and alpine treeline terrain. Field data showed that disturbances to discontinuous permafrost terrain can lead to large and persistent changes to ecosystem composition and structure. In spruce muskeg, permafrost thaw triggered by road construction dramatically increased soil moisture and facilitated a transition from spruce muskeg to sedge wetland. At alpine treeline the removal of stabilizing vegetation and organic soil during construction slowed subsequent ecosystem recovery. These findings are consistent with resilience theory that predicts that changes to key environmental factors will increase the likelihood of regime shifts. In terrain types where disturbance fundamentally alters ecosystem processes, the management of disturbance impacts in NNPR will be extremely difficult. Overall, this thesis contributes to our understanding of effects of disturbance on vegetation and abiotic conditions, and provides insight into the future of high-latitude ecosystems in a warmer climate with increased disturbance. / Graduate

Degradation of permafrost in peatlands can convert forested peat plateaus to inundated collapse bogs. Due to increased unfrozen soil carbon stocks and more saturated conditions, collapse bogs can potentially be large emitters of methane. Using a network of bubble traps permanently installed in peat, I tested several hypotheses about controls on ebullition in collapse bogs with varying time since thaw in interior Alaska. Ebullition increased during the growing season, likely due to increased substrate availability and warmer soils. Bubbles were found primarily in shallow peat layers, and were dominated by modern carbon. Ebullition hot spots were associated with high sedge density throughout the collapse sites. Episodic ebullition occurred during atmospheric pressure changes. Overall, my study demonstrated that permafrost thaw in peatlands will result in methane emissions through ebullition that include both young and old carbon, contradictory to the generally accepted paradigm; that ebullition in peatlands is solely a surface process.

Rock glaciers are common features in high alpine settings of the southeastern British Columbia Coast Mountains. The spatial distribution and characteristics of these periglacial features have not previously been documented. The goal of this research was to determine the distribution and activity of these rock glaciers in order to characterize their periglacial response to climatic variability. A high-resolution aerial inventory documented the presence of 187 rock glaciers between Lat. 50° 10’ - 52° 08’ N. These rock glaciers occur at sites located between 1900 m and 2400 m above sea level, where rain shadow effects and continental air masses result in persistent dry cold conditions. Intact rock glaciers were the most prevalent form and accounted for almost 90% of the rock glaciers included in the inventory. Glacier-derived features outnumbered talus-derived features by a ratio of 4:1 and only 22 relict rock glaciers were identified. Rock glaciers in this region occupy predominately northwest- to northeast-facing slopes, with talus-derived rock glaciers largely restricted to north-facing slopes. All rock glaciers were found at locations above presumed Younger Dryas terminal moraines, suggesting that they began to form after 9390 BP. Rock glacier activity during the Late Holocene was characterized using lichenometric methods to establish the relative surface age of three talus-derived features at Perkins Peak. Sustained periods of cool-wet climates activated pulses of rock glacier surface instability and movement, while a shift to warmer, drier conditions resulted in the loss of internal ice and increased surface stability. Varying degrees of present-day activity highlight a local topoclimatic control on talus-derived rock glacier behaviour. A dendrogeomorphological investigation at nearby Hellraving rock glacier indicated that it has been steadily advancing into surrounding forest since the beginning of the late Little Ice Age. Its continued advance in the face of warming temperatures suggests the internal thermodynamics of this rock glacier may be out of equilibrium with the contemporary climate. This research is the first to document and characterize rock glaciers in the Coast Mountains and challenges previous understandings of permafrost distribution in the southwestern Canadian Cordillera. / Graduate

This study aimed to gain an understanding of changing active layer dynamics in the High Arctic, specifically in terms of understanding the spatial distribution of mudboils to identify climatic and landscape controls, and active layer processes driving their formation. Systematic mapping of mudboils and sediment and water sampling was undertaken at the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut in 2012 and 2013. Based on borehole stratigraphic profiles taken at CBAWO, three primary soil units were determined: mudboils at surface; overburden (soil) material; and a grey, fine-grained layer at approximately 80cm depth. These soil classes were used for comparison to gain an understanding of the properties and origins of the mudboil materials. Results indicate that these features only occur late in the melt season during exceptionally warm years (2007, 2011, and 2012) and in some cases closely follow major rainfall events. High-resolution satellite imagery was analyzed to determine landscape controls over mudboil formation. Notably, mudboils were significantly associated with bare soil and polar semi-desert vegetation settings, corresponding to increased active layer depth and rate of thaw when compared to more vegetated areas. Further, localized occurrence of mudboils appears to be related to differential soil moisture retention and spatially heterogeneous soil water pressurization due to thaw into the ice-rich transient layer in warm years. We hypothesize that the locally drier locations develop soil ped structures that contribute to diapir development and mud ejection when seasonal melt and hydraulic conditions pressurize soil water. Geotechnical and geochemical analysis of soil samples indicates that mudboils at surface do not significantly differ in terms of composition and physical properties from the undisturbed overburden material. This is consistent with a fine-grained slurry likely being generated in situ from a parent bed and subsequently ejected to surface. This research provides insights into the processes and landscape controls over mudboil formation to aid in understanding localized soil water response to deep summer thaw, with implications for surface water quality and predictions and potential mitigation of permafrost-related degradation and disturbance. / Thesis (Master, Geography) -- Queen's University, 2014-05-22 13:56:49.078

Thesis (M.Sc.). / Written for the Dept. of Geography. Title from title page of PDF (viewed 2008/12/05). Includes bibliographical references.