Geography - Theses, Dissertations, and other Required Graduate Degree Essays

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Projected changes in Northern Hemisphere permafrost in temperature stabilization and overshoot scenarios

Author: 
Date created: 
2020-01-20
Abstract: 

Achieving the Paris Agreement goal of “holding the increase in global temperature to well below 2°C above pre-industrial levels” is increasingly challenging. Overshoot trajectories, which assume that a temperature target is reached after temporarily exceeding it, are becoming prominent in policy discussions. This thesis explores the long-term response of northern permafrost in temperature overshoot and stabilization scenarios used for the 6th Phase of the Coupled Model Intercomparison Project (CMIP6). The University of Victoria Earth System Climate Model, an Earth System model of intermediate complexity, is forced with a range of CMIP6 scenarios. Results suggest that permafrost recovery lags the decrease in surface air temperature associated with overshoot scenarios. Depending on the scenario, 15-30% of permafrost area is lost at the time temperature is restored to the level prior to the overshoot. Furthermore, in high temperature stabilization scenarios permafrost continues to thaw after global mean temperature is stabilized.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Kirsten Zickfeld
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.Sc.

Spatial distribution of soil class and soil pH in the Thompson-Okanagan region, British Columbia

Author: 
Date created: 
2019-09-24
Abstract: 

Soils are facing great threats from climate change and anthropogenic activities. It is essential to understand the characteristics of soils, such as class and pH, especially when it comes to the issue of evaluating soil quality. In the Thompson–Okanagan region, previous soil surveys covered most parts of the region in polygon data form; however, it would be beneficial if soil data were available at a finer resolution and with uniform soil categories. The digital soil mapping (DSM) approach has shown promising results over various landscapes with limited available data. The main objective of this study was to use an ensemble learning approach to map the spatial distribution of soil classes and soil pH at 25-meter resolution in the Thompson-Okanagan region, BC. Random Forest (RF) was used to map 16 soil subgroups. Overall prediction accuracy was 65.4% with an independent validation dataset. The study of spatial patterns of soil pH was tested with a combination of multiple base learners, which included a Multilinear Regression (GLM) learner, Stepwise Regression (STEP) learner, Lasso and Elastic-Net regularized Generalized Linear Regression (GLMNET) learner, a Kernel-based Support Vector Machine (KSVM) learner, and RF. Base learners with higher prediction accuracy were used to develop a Super Learner (SL). The fitted SL was then used to predict soil pH for three depth intervals (0 – 5cm, 5 – 15cm, and 15 – 30cm) at 25–meter resolution. For all three depth intervals, the SL proved to have the lowest MSE value and better prediction accuracy than was obtained from just using one of the base learners.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Margaret Schmidt
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.Sc.

Regulating in the public interest? Canadian energy regulation as an institutional fix for sovereign legitimacy

Author: 
Date created: 
2019-08-22
Abstract: 

Perhaps the most visible and pressing pipeline conflict in Canadian history, the proposed Trans Mountain Pipeline expansion has yet to see shovels break ground as the project is bound up in a web of legal challenges and political controversy. At the centre of the debate is the National Energy Board (NEB)—Canada’s energy regulator—responsible for regulating interjurisdictional pipelines. Recently, the NEB’s legitimacy has been called into question amid criticisms of being an untrustworthy, industry-captured regulator. In this thesis, I argue that the NEB operates as an institutional fix for state sovereignty, primarily through its mandate to determine if a proposed project is in the “public” or “national interest”. By aggregating benefits and localizing consequences, the NEB’s “public interest” mandate has become a means of circumventing the thorny politics of deliberative consultation—especially regarding Indigenous jurisdiction—to capture legitimacy and ensure projects proceed.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Geoff Mann
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.A.

The making of a middle class housing crisis: the ideology and politics of foreign real estate investment in Vancouver 2008 - 2018

Author: 
Date created: 
2019-08-02
Abstract: 

This study examines the ideological and structural factors that underpinned the politicization of foreign investment in real estate in Vancouver between 2008 and 2018. In the span of a couple of years, foreign investment in real estate emerged from obscurity to become the dominant explanation of the housing crisis, and one of the most pressing political issues in British Columbia. Based on a content analysis of news articles and secondary literature, this paper argues that the focus on foreign property investment shifted the public discourse about the housing crisis toward homeownership issues, and the experiences and needs of middle-class residents. It created a binary between deserving and undeserving homeowners along class and race lines, and constructed speculation as foreign, rather than as an inherent part of the local capitalist real estate economy.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Geoff Mann
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.A.

Exploring the relationship between vertical mixing, overturning circulation, AABW volume, and ventilation age during the last glacial maximum

Author: 
Date created: 
2019-06-26
Abstract: 

One interpretation of Last Glacial Maximum (LGM) paleo-environmental data is the expansion of poorly ventilated Antarctic Bottom Water (AABW) coinciding with weakened AABW overturning, which is reflected in few modelling efforts. This research addresses the relationship between vertical mixing, AABW volume, overturning circulation, and ventilation age using the UVic Earth System Climate Model with five vertical mixing parameterizations that differ in the value of diapycnal diffusivity in the deep ocean. In all simulations AABW volume and overturning strength increases during the LGM relative to pre-industrial (PI), with small differences between mixing schemes. All mixing schemes yield older bottom water during the LGM relative to PI, indicating that a decrease in overturning strength is not required to decrease ventilation age. Our results offer insights into the relationship between AABW overturning, volume, and ventilation, with little impact based on mixing scheme.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Kirsten Zickfeld
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.Sc.

Evaluating heat vulnerability and the impact of urban street tree planting on radiant heat exposure: examples from Vancouver’s neighborhoods

Author: 
Date created: 
2019-06-13
Abstract: 

Extensive impervious surface cover, anthropogenic heat, building structure and lack of vegetation contribute to the formation of distinct urban microclimates where higher air and surface temperature as well as lack of shade intensify outdoor heat exposure and thermal discomfort for humans. The objectives of this thesis are to explore the determinants of heat vulnerability across Vancouver’s neighborhoods and assess the impact of increasing street tree cover on extreme radiant heat exposure in different neighborhoods classified into local climate zones (LCZs) under present and future climate. To achieve these goals, first, the determinants of heat vulnerability in Vancouver’s neighborhoods were identified and population groups most vulnerable to extreme heat exposure were mapped by spatially superimposing multiple layers of socio-economic, environmental, and infrastructural data. Secondly, the influence of added street trees on radiant heat exposure across six different LCZs was investigated under present climate. This was done by employing the SOlar and LongWave Environmental Irradiance Geometry (SOLWEIG) model. The radiant cooling effect of increased street tree cover during the hottest day on record for Vancouver (July 29, 2009) was modeled by quantifying the spatiotemporal changes to mean radiant temperature (Tmrt). Results indicated a 2.1–4.2 °C reduction in spatially-averaged Tmrt during the hottest period of day. Lastly, this thesis sought to explore how changes in temperature and solar radiation under future climate projections would change Tmrt in Vancouver over the 2070-2100 period and the extent to which these changes could be mitigated by increased street tree cover. To this scope SOLWEIG was driven with downscaled climate projections using Representative Concentration Pathways (RCP) 4.5 and 8.5. Results showed that days with extreme radiant heat exposure were predicted to increase three- to five-fold under RCP 4.5 and 8.5, respectively. The addition of street trees can mitigate the increase in Tmrt under RCP 4.5 but is not sufficient to compensate for the Tmrt increase under RCP 8.5. The results of this thesis provide valuable insights to city decision-makers and urban planners regarding effective heat mitigation and adaptation interventions and guide future research seeking to simulate the effect of heat mitigation measures under current and future climates.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Kirsten Zickfeld
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) Ph.D.

Carbon quality and quantity in lake sediments and their relationship with pore-water and lake-water methane among lakes of the Mackenzie River Delta, Western Canadian Arctic

Author: 
Date created: 
2019-04-26
Abstract: 

Sediment cores were taken from lakes in the Mackenzie Delta to assess how carbon-content in the lake sediments, and their dissolved organic matter (DOM) quantity and quality, affects methane (CH4) concentrations in the pore-waters and lake-waters. Cores were taken just before ice-out (34 lakes), then bi-weekly (6 lakes) until late open-water, in combination with CH4 oxidation (MOX) measurements at the sediment-water interface. Fluorescence components derived from Parallel Factor Analysis of pore-water DOM (four under-ice, six open-water) revealed carbon-quality patterns related to river-to-lake connection times and pore-water CH4. Pore-water CH4 was lower concentration and less depleted in 13C in near-surface relative to deeper sediments. Anaerobic electron-acceptor concentrations were well-related to near-surface CH4 concentrations, but varied by lake, whereas DOM-quality measures were more strongly related to pore-water CH4 at deeper depths. MOX rates ranged from 2.72 to -0.19 umol CH4 m-3 s-1 and were related to CH4 substrate concentrations and sediment-N content.

Document type: 
Thesis
Senior supervisor: 
Lance Lesack
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.Sc.

Controls on dune dimensions in rivers

Date created: 
2018-07-03
Abstract: 

Dunes are bedforms commonly found in sand-bedded rivers. They are important sources of flow resistance and mechanisms for sediment transport, so there is a practical need to directly predict dune dimensions. Migrating dunes also leave signatures of their presence and evolution as cross-strata in sand deposits, which can be used to indirectly hindcast paleo-flows. The most common method to predict dimensions in modern flows or hindcast paleo-flows is depth-scaling relations, which assume a depth control on dunes. There is substantial scatter about depth-scaling relations, suggesting that other physical processes may control dimensions. This study identifies primary controls on dune dimensions in rivers through a meta-analysis of published dune data, and a series of flume experiments. The data compilation shows approximately two orders of magnitude variation in dune height and length at any given flow depth. Dune heights in shallow flows (< 2.5 m), where asymmetric dunes with high lee angles are common, grow relatively higher in the flow than symmetrical low lee angle dunes in deeper channels (> 2.5 m). The data set is used to provide depth-scaling relations with added statistical uncertainty. Scatter about the scaling relations is attributed to natural variability in dune dimensions and transport stage effects. Flume experiments are used to better identify controls on dune dimensions. Results confirm dune-depth scaling is weak and that transport stage is a fundamental control. The experimental data are used to derive new non-linear scaling relations between equilibrium dune dimensions and transport stage. The relations provide a physically-sound method to guide predictions of dune dimensions in rivers and paleo-reconstructions from estimated dune dimensions in the rock record. A series of experimental observations of dune growth from a flat bed were also made. The results show that growth behaviour also depends on transport stage, and the time to equilibrium dimensions decreases non-linearly with transport stage. The observations are used to propose a series of relations that can predict dune dimensions through time as they respond to an imposed flow.

Document type: 
Thesis
File(s): 
etd10769-15-thldeq.mp4
etd10769-15-bdldeq.mp4
etd10769-15-lmixeq.mp4
etd10769-15-umixeq.mp4
etd10769-15-spsneq.mp4
etd10769-20-thldeq.mp4
etd10769-20-bdldeq.mp4
etd10769-20-lmixeq.mp4
etd10769-20-umixeq.mp4
etd10769-20-spsneq.mp4
etd10769-25-thldeq.mp4
etd10769-25-bdldeq.mp4
etd10769-15-thld.mp4
etd10769-15-bdld.mp4
etd10769-15-lmix.mp4
etd10769-15-lmix-short.mp4
etd10769-15-umix.mp4
etd10769-15-umix-short.mp4
etd10769-15-spsn.mp4
etd10769-20-thld.mp4
etd10769-20-bdld.mp4
etd10769-20-lmix.mp4
etd10769-20-lmix-short.mp4
etd10769-20-umix.mp4
etd10769-20-umix-short.mp4
etd10769-20-spsn.mp4
etd10769-25-thld.mp4
etd10769-25-bdld.mp4
Senior supervisor: 
Jeremy Venditti
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) Ph.D.

Arctic deltas as biogeochemical hotspots affecting the delivery of nutrients and dissolved organic matter to the Arctic Ocean

Author: 
Date created: 
2018-12-04
Abstract: 

The Mackenzie River and Delta were sampled during hydrologically-defined seasons in four consecutive years to assess 1) the importance of sampling during the rising limb of the flood hydrograph (rising freshet) for accurately characterizing constituent fluxes and quality, and 2) how floodplain processes affect discharge to the Arctic Ocean. Including rising freshet samples had a modest effect on annual sediment and nutrient flux estimates for the Mackenzie River (-9 to +26% difference). Nutrient quality was very different during the rising freshet, however, with relatively high concentrations of carbon-rich dissolved organic matter (DOM), phosphorus-rich particles, and nitrogen-rich inorganic nutrients. Mackenzie River DOM quality was relatively fresher, more terrigenous, and younger (radiocarbon values suggesting ages < 15 years) during the rising freshet, indicating a high proportion of recently-fixed vascular plant material. The Mackenzie was also a net absorber of carbon dioxide during the rising freshet (-112 to -258 mg-C m-2 d-1), switching to net emission after peak flood. Open water (freshet through summer) fluxes of dissolved organic carbon (1.4 Tg) and lignin (7.1 Gg) in the Mackenzie River were greater than previously reported total annual fluxes, likely due to the inclusion of rising freshet data herein. Optical parameters, and statistical relations between fluorescence components derived from Parallel Factor Analysis (PARAFAC; six in delta channels, five in delta lakes) and chemical biomarkers (e.g. lignin phenols), suggest substantial modification of DOM in delta lakes and on the floodplain during downstream transport. When incubated (14 days) under solar conditions similar to those on the floodplain, Mackenzie River DOM (isolated during peak flood) experienced photochemical changes on par with those observed in delta lakes over the entire open water period. Photodegraded DOM significantly reduced abundances but fueled per-cell growth in bacterial populations from delta habitats, indicating rapid shifts in community composition. Gradients in chemical biomarkers were related to the delta-wide gradient of lake hydrological connectivity. These results emphasize the importance of the rising freshet in accurately characterizing Mackenzie River DOM quality and carbon fluxes, and the need to sample downstream sites in lake-rich circumpolar deltas to constrain flux estimates and characterize discharge to the Arctic Ocean.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Lance Lesack
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) Ph.D.

Composition of aquatic microbial communities and their relation to water-column methane cycling among Mackenzie Delta lakes, western Canadian Arctic

Date created: 
2018-11-29
Abstract: 

Seasonal dynamics of water-column microbial communities and methanotrophs were monitored in six lakes of the Mackenzie River Delta using gene sequencing of 16S rRNA gene and qPCR of the 16S rRNA and methane monooxygenase (pmoA) genes. Selected lakes varied in biogeochemistry based on annual river-to-lake connection times, which we hypothesized would impact bacterial community composition and methanotroph relative abundance. River-to-lake and seasonal influences on carbon bioavailability and quantity, nutrients, temperature and flooding correlated with seasonal changes in microbial composition. Methanotroph groups including Methylobacter and methylotrophs Candidatus Methylopumilus and Candidatus Methylophilaceae were detected in all lakes but at higher relative abundance in the winter and spring when lake-water methane concentrations were highest. Open-water methanotroph abundance was highest in spring. In experimental enclosures, methanogenesis was detected in oxygenated lake-water and rates varied by lake type. Nutrient enhancements altered microbial composition and increased rates of methane oxidation with increasing lake isolation.

Document type: 
Thesis
Senior supervisor: 
Lance Lesack
Department: 
Environment: Department of Geography
Thesis type: 
(Thesis) M.Sc.