Involuted soil horizons and buried organic matter in the active layer and near-surface permafrost provide evidence that soil movement or cryoturbation is occurring within the active layer in hummocky terrain. Cryoturbation in the active layer of permafrost-affected soils could have significant implications in sequestering carbon, including trace metals and contaminants that are absorbed onto organic matter. Though several hummock development theories exist, there has thus far been limited evidence to support them; similarly, few studies have been able to establish hummock age. This study aimed to contribute radiocarbon-dated ages of buried organics in both the active layer and permafrost, as well as provide evidence for the convective cell/equilibrium model and the collapse model. Trenches were dug along a transect at two well-developed hummock sites in the Mackenzie Delta near Inuvik, NWT. Active layer and permafrost samples were analyzed for distribution of gravimetric water content (GWC), organic matter, inorganic carbon, and carbon-14 (C14). Results determined material ranged in age from the modern period (1959-1987AD) to 2300 yr BP with a generally normal distribution. Buried organics within the active layer ranged from 557-670 yr BP and 1023-1240 yr BP, with average displacement rates of 0.43 mm/yr and 0.16 mm/yr, respectively. These results suggest the convective cell/equilibrium and hummock collapse models can function simultaneously.

Rapid climate change is driving increases in tundra vegetation productivity and altering the frequency and severity of natural disturbances across the Arctic. While tundra vegetation change has been widespread, there is still uncertainty about the influence of fine-scale factors on change and the role of interactions between warming, disturbance, and vegetation change. In my MSc research I investigated how Arctic tundra vegetation is responding to ongoing climate change and more severe tundra fire in the western Canadian Arctic. In the first part of my thesis I measured post-fire soil and vegetation recovery along a burn severity gradient at six fires, which burned in 2012 in the Northwest Territories. My observations suggest that deciduous shrub communities (dominated by Betula glandulosa) are resilient to high severity fire and that severe fire promotes edaphic conditions that favor the persistence of this vegetation type. In the second part of my thesis, I investigated the spatial patterns of trends in tundra vegetation productivity over the past three decades using Random Forests machine learning to analyze Enhanced Vegetation Index (EVI) data derived from Landsat imagery. My Random Forests models of the relationship between Landsat EVI trends and biophysical variables showed that two-thirds of the western Canadian Arctic productivity has increased during the past three decades and that this change is occurring most rapidly in dwarf and upright shrub-dominated regions. Taken together, my research demonstrates that shrub tundra communities are well adapted to severe fire and show increasing productivity in response to warming Arctic temperature. My research also indicates that these relationships can be highly complex at finer scales, where they are mediated by local variations in microclimate, topography, and moisture. / Graduate

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This thesis addresses the consequences of the last glaciation on the distribution and genetic diversity of arctic flora. The principal aim is to infer the full-glacial and postglacial migrational history of Dryas integrifolia M. Vahl. (Rosaceae) from the intraspecific phylogeny of cpDNA haplotypes along with pollen and macrofossil distribution data. The results suggest that four refugia existed during the last glaciation and that each served as significant sources of recolonization when the ice retreated. The two most important refugia are located in the northwestern Arctic (Beringia and the High Arctic), with two other refugia located southeast of the ice sheet and along the coastal regions of the eastern Arctic. High genetic substructure among populations is likely attributable to past vicariance and recent recolonization events, whereas high local diversity is probably indicative of recolonization from several sources and high gene flow in recent time.

Primary production was studied in Fram Sound, part of the Hell Gate-Cardigan Strait polynya, from June to August, 1982. Primary production rates, phytoplankton biomass (chlorophyll α), and water transparency were measured and used in conjunction with modelled solar radiation values to numerically model primary production during this time. The major phytoplankton nutrients were also measured. Early season chlorophyll α concentrations were low, and the increased light availability due to reduced ice cover in this area did not appear to enhance early season production. Chlorophyll concentrations peaked twice; the first peak occured on 20 July and the second on 14 August. The mean primary production rate and phytoplankton biomass were 998 mg C.m⁻² .d⁻¹ and 72 mg chl.m⁻² . This production rate is higher than that measured in other High Arctic areas. Nitrogen, phosphorus and silica were essentially homogeneously distributed during the sampling period and these concentrations varied little from June to August except during 5 days in late August, when they decreased by half then returned to previous levels. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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Identifying the drivers of Arctic climate variability is essential for understanding the recent rapid changes in local climate and determining the mechanisms that cause them. Remote tropical sea surface temperatures (SST) have been identified in previous studies as having contributed to the recent positive trends in surface temperature and geopotential height at 200 hPa over north Canada and Greenland (1979-2012) through poleward propagating Rossby waves. However, the source and direction of wave propagation on to north Canada and Greenland (NCG) differs across climate datasets indicating that there are still uncertainties surrounding the mechanisms for how the tropics influence the NCG climate. This thesis aims to further investigate the robustness of the trends over NCG and understand how circulation in this region responds to imposed tropical SST perturbations. The eddy 200 hPa geopotential height (Z200) trends over NCG are assessed in a number of different datasets and compared to the response of eddy Z200 over NCG to imposed tropical SST perturbations in a number of sensitivity studies using the HadGEM3 atmosphere-only model. These model experiments are forced with observed differences in SSTs from the beginning and end of the satellite record (1979-1988 and 2003-2012), with spatial perturbations for [i] the entire tropics, [ii] global SSTs, [iii] the tropical Pacific only, [iv] the tropical Atlantic SST only, [v] the tropical Indian Ocean only. The positive spatial trends of eddy Z200 over NCG from ERA-Interim reanalysis is largely captured in ensemble means of two available climate datasets, UPSCALE and AMIP, indicating that this is a robust climate pattern, however, these trends appear to be stronger in the latter part of the record specifically over the UPSCALE period (1985 to 2011). The model sensitivity studies show that a negative eddy Z200 anomaly over NCG was found in response to all imposed tropical SST perturbations (2003-2012) relative to a background state (1979-1988). This was due a stationary trough over the region that was able to intensify in response to a lack of a strong anomalous wave forcing from changes in mid-tropospheric temperature and zonal winds. The forcing from the tropical Atlantic, relative to the other tropical ocean basins, resulted in the largest eddy Z200 response over NCG, indicating its dominance in forcing the large scale tropical signal. The influence of extratropical SST perturbations relative to tropical SST perturbations were also investigated and it was demonstrated that this negative anomaly is largely driven by the change in tropical sea surface temperatures.

In 1930, A.Y. Jackson and Lawren S. Harris travelled to the Arctic Archipelago as members of Canada’s Eastern Arctic Patrol. The collaborative venture between the Department of the Interior and the noted Group of Seven artists, which followed Jackson’s 1927 voyage aboard the government patrol, was part of a mutual aim to generate popular interest in the Canadian North through art. This thesis examines the underlying political context of both the 1927 and 1930 collaborative efforts. It examines the government patrols in connection with the promotion of Jackson’s and Harris’s Arctic works as part of a larger process of advancing the Arctic as a Canadian possession during a period of increased foreign interest in the region. Drawing on primary source material as well as various print media reports and exhibition reviews, this study provides insight into how the contemporary framing of Jackson’s and Harris’s Arctic sketches and paintings from the government-supported expeditions—the ways in which the works were discussed and understood—contributed not only to the “imagining” of the Arctic as a Canadian possession, but also to the dissemination of Canadian sovereignty efforts in the North. / Thesis (Master, Art History) -- Queen's University, 2012-12-05 15:24:52.546