Undergraduate Honours Theses (Earth and Ocean Sciences)
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Item Mitigating anthropogenic climate change with aqueous green energy: Direct air carbon dioxide capture and storage powered by ocean thermal energy conversion(University of Victoria, 2023) Olim, SophiaIn the 2015 Paris Accords, 196 nations agreed to keep global warming below 2°C and to pursue efforts to limit it to below 1.5°C. The Earth has already warmed by around 1.1°C since preindustrial times ( Masson-Delmotte et al., 2022; Shukla et al., 2022). If worldwide fossil fuel combustion was immediately eliminated, the direct and indirect net cooling effect of atmospheric aerosol loading would rapidly dissipate. The aerosol cooling realised since the preindustrial era would be eliminated, resulting in an additional warming of around 0.6°C and taking the Earth rapidly to an around 1.7°C warming. In 2018 the Intergovernmental Panel on Climate Change noted the requirement of widespread negative emissions technology in order to meet this 1.5°C target (Masson-Delmotte et al., 2022; Rumjaun et al., 2018). In direct air CO2 capture and storage (DACCS), CO2 is scrubbed from the atmosphere and injected into underground geological formations (Keith et al., 2018). Carbon dioxide is a potent greenhouse gas and is the focus of many negative emissions technologies. Ocean thermal energy conversion (OTEC) is a form of electricity production that exploits the temperature difference between deep and shallow ocean waters, analogous to land-based heat pumps. OTEC requires a temperature gradient of at least 18°C and is most efficient in the tropics, due to the high temperature gradient between shallow warm water (around 25 metres deep) and deep cold waters (around 1000 metres deep) (Nihous, 2005). The UVic Earth System Climate Model (UVic ESCM) is used to explore the feasibility of using OTEC to power DACCS as a negative emissions technology in order to help mitigate anthropogenic climate change. Once this CO2 has been removed from the atmosphere, it needs to be injected where it can remain safely stored. In marine environments, sedimentary basins along continental shelves, such as depleted oil and gas fields, are the most geologically sound choice for this (Celia et al., 2015; Strutt et al., 2003). In order to maximise OTEC power production while limiting the need to transport this energy away from the source, offshore OTEC plants are used to power DACCS in two selected oil and gas basins of suitable size in the tropics. OTEC power production of 3 TW of electricity powering DACCS can result in a global relative decrease of 277 parts per million CO2 by 2100 and a relative temperature decrease of 1.18°C, compared to diagnosed emissions from the IPCC 2018 “business as usual” RCP 8.5 scenario. There are potential negative impacts to implementing OTEC on a large scale including changes in ocean temperatures, biological productivity, precipitation patterns, and atmosphere-ocean variability (Rau and Baird, 2018; Devault and Péné-Annette, 2017; Rajagopalan and Nihous, 2013; Nihous, 2005). While these must be considered, this combination of green energy and negative emission technology offers an exciting new approach to help mitigate anthropogenic climate change. Supervisors: Andrew Weaver and Michael EbyItem CO2 degassing and metal enrichments during magma-carbonate interactions in the Jurassic Bonanza Arc(University of Victoria, 2024) Arndt, GrahamThe long term (>1 Myr) atmospheric carbon budget is dominated by the carbon cycle and has great implications on habitability. One potential source of degassed carbon can be derived from the overlying continental plate where CO2 is produced from magma-carbonate interactions. Limestone assimilation is a local process that is relegated to the vicinity of the sidewall around a magma chamber (Iacono Marziano et al., 2008). As such, the network of dykes and sills offer more surface area to interact with carbonate rock opposed to voluminous plutons. Meter-scale dyke and sill samples from the Jurassic Bonanza Arc were collected from the Merry Widow Mountain region to quantify the degree of limestone assimilation. Two types of samples were investigated: (1) bulk rock samples and (2) milli-slices sampled from a single 25 cm cross-section of dyke 79B. Major and trace element chemistry was gathered by LA-ICP-MS. We discovered that the dykes show anomalous elemental abundances for Sr, U, MnO2, and Na2O. In particular, the dykes appear super-enriched in Sr opposed to their parent basalt and limestone endmembers. The enriched Sr concentrations can be explained using a binary mixing model which indicates that the dykes assimilated up to 80 wt% limestone from a primitive carbonate source. This magnitude of limestone assimilation could generate up to 35 wt% CO2 during the decarbonization of limestone into basaltic dykes. Furthermore, limestone assimilation causes desilication and calcium enrichment of the basaltic melt adjacent to the contact region (Barnes et al., 2005; Iacono Marziano et al., 2008,). Consequently, this change in melt chemistry enhances the dyke’s sulfur saturation limit and therefore its capacity to transport sulfur species. SCSS calculations indicate that the dyke contact may hold up to three times more sulfur than the dyke interior as the result of partial assimilation by limestone. An increase in sulfur saturation has important implications because it can assist in the partitioning of chalcophile elements out of a silica-rich melt, and the dissolved sulfur species can later be degassed at volcanic arcs which impacts global climate (McLinden et al. 2016; D’Souza & Canil, 2018). Overall, sulfur saturation can help model the process by which sulfide immiscibility melts form in a magma body which is a critical step in the development of ore deposits (Haldar, 2018). Supervisors: Dante Canil and Rebecca MorrisItem Ocean optics: Development of glider-based productivity analysis in BC waters using backscatter(2025) Koopmans, EmilyThe ocean plays a crucial role in regulating atmospheric carbon dioxide yet quantifying the processes that govern its carbon storage remains a challenge. The biological pump, which converts dissolved carbon into organic particles through biological processes, is a key component of this cycle. While some particles remain suspended in the upper ocean, others sink, either individually or as larger aggregates, contributing to long-term carbon sequestration. Understanding the distribution and size of these particles is essential, but measurements are difficult to obtain since particle dynamics fluctuate with biological activity, ocean currents, and seasonal changes. Optical backscatter offers a valuable tool to address this challenge. We developed a method to process backscatter sensor data from autonomous ocean gliders, adapting a technique originally designed for Argo floats. Our approach partitions raw backscatter into three components: scattering from large aggregates, smaller particles, and instrument noise. A two-filter method was used to isolate scattering from small particles, while the deepest backscatter measurements provided an estimate of background noise. The remaining signal was attributed to large aggregates. We applied this method to data from a Canadian-Pacific Robotic Ocean Observing Facility (C-PROOF) glider mission in offshore British Columbia waters. By comparing size-resolved backscatter and chlorophyll fluorescence, we observed distinct differences in particle dynamics, with small-particle backscatter strongly correlated with chlorophyll and large-particle backscatter showing weaker associations. We identified contrasting high-productivity regions: one dominated by smaller particles, and another dominated by large aggregates. These patterns suggest that areas with similar chlorophyll concentrations can differ significantly in their potential for carbon export, depending on particle composition and sinking behavior. This approach also revealed important oceanographic features, including a subsurface chlorophyll maximum, sediment resuspension layers, and a small but persistent zone of elevated productivity likely influenced by large-scale ocean circulation. These features highlight how regional carbon export can be enhanced by subtle physical changes such as fronts or circulation boundaries—emphasizing the need to consider both biological and physical drivers when studying oceanic carbon cycling. By enabling size-resolved analysis of particulate matter, our method enhances the utility of gliders for carbon cycle research. Its application across other missions could help identify export hotspots, track seasonal variability, and improve estimates of oceanic carbon sequestration in a changing climate. Supervisor: Roberta HammeItem Recovery on the rocks: Can we use carbon isotope variability to constrain the Early-Middle Triassic Boundary?(2025) Lovett, KasciaFollowing Earth’s largest mass extinction, the Early Triassic represents a time of continued environmental disruption that has been recorded in the rock record. Specifically, marine carbonate rocks of this time indicate large perturbations to the global carbon cycle. These perturbations can be utilized as a proxy to help identify the Early Triassic Stage in the sedimentary rock record. As the boundary between the Early and Middle Triassic has had issues with its biostratigraphy, this study aims to use chemostratigraphy to further constrain its dating as the North American fossil record is limited. The Union Wash Formation in the Inyo Mountains of eastern California is composed of marine sedimentary rocks of Early Triassic age deposited along the eastern Panthalassa Ocean coastline. It consists of deep water, low energy mixed carbonate and siliciclastic lithologies with three major lithologic units based on carbonate or siliciclastic dominance. The stratigraphically lowest unit features an initially high organic matter content with no fossils while the two upper units are each host to ammonoids from the Neopopanoceras haugi Zone indicating a late Spathian age. Stable isotope geochemistry indicates high variability in the δ¹³C values of carbonate sediments throughout the formation. This trend is like that found globally throughout the late Early Triassic but shows evidence of diagenetic overprinting of δ¹³Ccarb and δ18Ocarb. There is also a possible facies dependence resulting from local variations in the carbon cycle, with low δ¹³Ccarb values within siliciclastic-dominant lithologies and higher δ¹³Ccarb values within carbonate-dominant lithologies. The similarities between global isotopic data and the Union Wash Formation are compelling but the evidence of local control on δ¹³Ccarb values (e.g. facies dependence) and possible diagenetic overprinting needs further investigation. Supervisor: Jon HussonItem Application of the derivative and van der Kamp methods: Enhancing the interpretation of pumping tests for fractured bedrock aquifers on Vancouver Island, BC(2025) Abel, MalakyeInterpreting pumping test responses for fractured bedrock aquifers is challenging, particularly when estimating the transmissivity of an aquifer and the long-term sustainable yield of a well. This study applies the derivative method (e.g., Renard et al., 2009) on the pumping and recovery phase of six pumping tests from bedrock wells on Vancouver Island and the Gulf Islands, sourced from local consultants, to characterize flow regimes to determine how transmissivity calculations can be improved. The van der Kamp method (van der Kamp, 1989) was also tested for its effectiveness in the extrapolation of pumping responses and its potential for improving the ability to estimate a sustainable pumping rate for a 100-day dry season (Q100) that is often prescribed when licencing a well. Two pumping tests studied were for fractured sedimentary bedrock aquifers while four were for fractured crystalline bedrock aquifers. The tests lasted 12-72 hours and were followed by recovery monitoring of a similar duration. The results showed that for the fractured sedimentary bedrock aquifers, linear flow may precede infinite-acting radial flow for several hundred minutes. For the tests that exhibited infinite-acting radial flow as the final derivative response, the duration was approximately 0.3 log cycles of time, cut off when pumping ended. Infinite-acting radial flow identified using the recovery phase derivative often matched the pumping phase derivative in symmetry, though was sometimes different in magnitude. Identifying periods of radial flow from the pumping and recovery phases facilitated the calculation of transmissivity using various analytical solutions. Transmissivity values calculated using the Theis curve-matching (Theis, 1935) and Cooper-Jacob (Cooper & Jacob, 1946) methods, from the same radial drawdown data, were similar (within 0.5 log transmissivity values). For three pumping tests, transmissivity values calculated from the symmetrical recovery phase using the Theis recovery method (Theis, 1935) were noticeably different (over 0.19 orders of magnitude smaller or larger) than those calculated from the pumping phase. The van der Kamp method did not work for all pumping tests analyzed. The extended drawdown calculated using the van der Kamp method for the same three tests exhibited various non-ideal responses. Two tests exhibited a rising static water level, where the water level in the well at the start of the pumping test was erroneously assumed to be not changing. An unaccounted-for rising static water level induces a drift in the drawdown and subsequent recovery data, causing a discrepancy in the transmissivity calculated from the pumping and recovery phase, evident by a difference in the magnitude of the pumping and recovery derivative plots. The third test may have been subject to dewatering or a falling static water level late in the recovery phase which caused a steepening of the extended drawdown. When the “static” water level is not static, the extended drawdown does not improve the extrapolation of the drawdown to 100 days, which is required when estimating Q100. When the static water level was stable, as for the three other pumping tests, it lent confidence to the extrapolation of drawdown to 100 days to calculate Q100, reducing the reliance on an empirical straight-line extrapolation of drawdown to 100 days. A rising static water level, if not identified before pumping, negatively affects Q100 estimates; especially for high-yield wells where the drawdown rate is slower and may be more sensitive to static water level shifts. The drawdown rate drifts do not as negatively alter transmissivity calculations because transmissivity values are log-normally distributed. Minor drifts in drawdown rate have less impact on the relative accuracy. To enhance test reliability and facilitate the application of the van der Kamp method, future tests should confirm a “static” water level before proceeding with testing. Additionally, to extract maximal utilization of the van der Kamp method and recovery derivative, the recovery phase should last at least as long as the pumping phase, rather than ending at 90% recovery as is currently recommended by the B.C. Ministry of Environment (MoE, n.d.). Supervisors: Mike Wei and Lucinda LeonardItem Variations in earthquake detection across Ocean Networks Canada’s early warning system(2025) McMartin, KatieOcean Networks Canada’s Earthquake Early Warning (EEW) system has been in operation since 2023. This system uses P wave parameters measured at onshore and offshore stations to predict strong ground shaking and provide advance warning to operators of infrastructure (e.g., trains, planes) and other subscribers. Since its launch the system has detected hundreds of earthquakes. However, when compared to other organizations, the system is missing events. To investigate, Ocean Networks Canada’s earthquake catalog was first compared to those of Natural Resources Canada and the United States Geological Survey. It was found that events are primarily being missed in the northwest and southwest portions of the EEW grid (i.e., in the Explorer plate region south of Haida Gwaii and along the Explorer-Pacific divergent margin) with the system doing a good job of detecting events near Vancouver Island and the Nootka fault zone. In order to determine if events are going undetected because of station geometry (i.e., not enough stations are close enough to the epicentre for P waves to be detected), modelling using ground motion prediction equations was carried out to estimate the minimum detectable magnitude across the grid. In addition, a case study was investigated on a significant undetected event to assess the role of other aspects of the EEW detection algorithm (e.g., epicentre determination). The results showed that the likely reason events are going undetected across the EEW grid is a combination of the geometry of the stations and other aspects of the detection algorithm. The addition of stations from nearby networks (e.g., in Haida Gwaii) and improvements to the epicentre determination algorithm would increase the detection of events across the Ocean Networks Canada Earthquake Early Warning system. Supervisors: Lucinda Leonard and Alireza Mahani