Browsing by Subject "Oceanography"
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Item 3-D seismic investigations of northern Cascadia marine gas hydrates(2018-10-23) Riedel, Michael; Hyndman, R. D.This dissertation presents results from 3-D (parallel 2-D) high resolution seismic surveys and associated studies over an area with deep sea gas hydrate occurrence. The study area is located on the accretionary prism of the northern Cascadia subduction zone offshore Vancouver Island, Canada. The major objectives of this study were the imaging of a gas/fluid vent field found in the study area and detailed mapping of the tectonic setting and geological controls on fluid/gas venting. Secondary objectives were the characterization of the gas hydrate occurrence and constraints on the seismic nature of the bottom-simulating reflector (BSR) and its spatial distribution. The main grid was 40 lines at 100 m spacing with eight perpendicular crossing lines of multichannel and single channel seismic reflection, and 3.5 kHz subbottom profiler data. In addition to the main 3-D seismic grid, two smaller single channel grids (25 m spacing) were collected over the vent field. The multichannel seismic data acquired with the Canadian Ocean Acoustic Measurement System (COAMS) streamer required correction for irregular towing depth and shot point spacing. A new array element localization (AEL) technique was developed to calculate receiver depth and offset. The individual receiver depths along the COAMS streamer varied between 10-40 m, which resulted in the occurrence of a prominent receiver ghost that could not be completely removed from the seismic data. The ghost resulted in limited vertical resolution and a coarse velocity depth function. The vent field is characterized by several blank zones that are related to near-surface deformation and faulting. These zones are 80-400 m wide and can be traced downward through the upper 100-200 m thick slope sediment section until they are lost in the accreted sediments that lack coherent layered reflectivity. The blank zones are also characterized by high amplitude rims that are concluded to result from the interference effect of diffractions. These diffractions result due to relatively sharp discontinuities in the sediment physical properties at the blank zone boundary. 2-D vertical incidence seismic modeling suggests an increase in P-wave velocity inside of the blank zone with only minor changes in density. Blanking is believed to be mainly the effect of increased hydrate formation within the fault planes. The faults are conduits for upward migrating fluids and methane gas that is converted into hydrate once it reaches the hydrate stability field. Carbonate formations at the seafloor can also contribute to blanking especially at higher frequencies. Free gas may be present in case of full hydrate saturation or strong fluid flow. Geochemical analyses of pore water and water-column samples carried out in cooperation with Scripps Institute of Oceanography indicate relatively low fluid fluxes of less than 1 mm/yr and there is no heat flow anomaly present over the vent field. Methane concentrations of 20 n-moles/L (about 8 times the ocean background concentration) were detected in water-column samples of the first 100-200 m above the main blank zone of the vent field. Venting is also believed to be strongly episodic with a recently more quiet time. However, the observed carbonate crusts indicate a long-term activity of the vents.Item A chemical characterization of the Endeavour non-buoyant plume, Juan de Fuca Ridge(2024) Zee, Meghan; Cullen, Jay T.This study aims to provide a quantitative chemical characterization of the Endeavour non-buoyant plume and examine the processes that impact trace metal transport from vent sites to the ocean interior. The chemistry of the Endeavour non-buoyant plume was analyzed using filtered and unfiltered seawater samples collected at 5 stations, starting on-axis at the Main Endeavour Vent field and extending ~45 km southwest of the axial valley. The spatial distribution of these trace metals is likely controlled by a number of processes, including metal sulfide precipitation, oxidation, sedimentation, and plume mixing. Iron (Fe) and manganese (Mn) are limiting or co-limiting nutrients for primary productivity, nitrogen fixation and other biogeochemically important processes in the ocean. The transport of metals associated with hydrothermal plumes and the processes that impact their fate are poorly understood. High concentrations of dFe (24-68 nmol kg-1) and dMn (46-98 nmol kg-1), relative to ambient seawater concentrations at similar depths in the region, were observed proximal to the vent field, followed by a sharp decrease to 1.2-2.9 nmol kg-1 dFe and 0.76-1.4 nmol kg-1 dMn 45 km southwest of the axial valley. Roughly 66% of the Fe present in the non-buoyant plume proximal to the vent field is in the particulate phase (defined as the difference between total dissolvable and dissolved). The particulate phase decreases to ~45% at the most distal station. Particulate Mn increases with distance from the vent field with 25% proximal to the vent field and 56% 45 km off-axis. This study hypothesizes that the spatial distribution and size partitioning of Fe and Mn can be explained by a combination of sulfide precipitation near-field, oxidation and oxide formation, and plume mixing with surrounding seawater. Chalcophile elements including cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd), are trace metals often associated with hydrothermal systems. Due to precipitation processes, these trace metals are not typically found in non-buoyant plumes far from vent fields. Correlations between these chalcophile elements with particulate Fe at END1 indicate similar removal pathways and highlight the importance near-field processes (precipitation, oxidation, mixing) play in controlling their net-input to the ocean. When compared to the geochemistry of sediments at the Main Endeavour Vent field, non-buoyant plume chemistry shows similar spatial trends. Furthermore, high mass accumulations of Fe, Zn and Cu on-axis along with the presence of chalcopyrite, pyrite, and sphalerite help explain the higher proportion of the particulate phase of these elements proximal to the vent field.Item Analysis of MODIS-Aqua imagery to determine spring phytoplankton phenology in the Strait of Georgia, Canada(2015-12-21) Carswell, Tyson Kyle; Costa, MayciraThe goal of this research was to construct a time series of accurate chlorophyll-a concentration for the Strait of Georgia (SoG), Canada, using an improved atmospheric correction scheme and workflow for the Moderate Resolution Imaging Spectroradiometer AQUA (MODIS) satellite instrument to describe the chla dynamics and spring bloom phenology in the SoG. In situ radiometric samples were acquired via Aerosol Robotic Network (AERONET), and hyperspectral data collected from a Hyperspectral Surface Acquisition System (HyperSAS) to assess three potential atmospheric correction schemes. Water property samples including total suspended material (TSM), chromophoric dissolved organic matter (CDOM), and chlorophyll concentrations (chla) were collected to further assess atmospheric corrections and the applied ‘Ocean Color 3 Modis’ (OC3M) standard chlorophyll algorithm. Regression, Absolute percentage difference (APD), Relative Percentage difference (RPD), and Root mean squared error (RMSE) analysis revealed the most appropriate method to be the ‘Management Unit of the North Seas Mathematical Models’ (MUMM) using the shortwave infrared spectrum (SWIR) to determine NIR-derived aerosol model. This method was used to construct a time series (July 2002-June 2014) of daily chlorophyll maps for all available imagery. Files were spatially binned into 8-day composites for the North and Central SoG where a modified threshold-based definition was used to determine the start of the spring phytoplankton bloom period, as well as timing of maxima and duration of the largest spring bloom. Results indicate Central SoG start dates range from late February to late April, with an average start date at the last week of March. These results compare favorably to Hindcast predictive modelling of bloom start dates. The Northern SoG bloom phenology starts on average 9 days earlier, and experiences lower chlorophyll-a magnitudes. Hierarchical clustering with correlation similarity of spring seasons indicate 2008 and 2007 were anomalous, while 2009 and 2012 were the most correlated for blooms occurring in the spring season.Item Contrasting lateral stirring regimes along line P modulated by intermittent mesoscale eddies(2025) Talbot, Lauryn; Klymak, Jody Michael; Ross, TetjanaLateral stirring is a key process shaping the physical and biogeochemical state of the ocean, yet it remains under-sampled and poorly understood, particularly at submesoscales (1–100 km). Along Line P in the Northeast Pacific, lateral stirring was characterized using 15 glider transects at 3 km horizontal resolution, collected from September 2019 to December 2024. Normalized isopycnal temperature anomalies, $\theta^{*}$, equivalent to normalized spice anomalies, reveal significant spatial and temporal variability in lateral variance across meso- and submesoscale ranges. Nearshore tracer spectra follow a power-law slope of $k^{0.2}$, with more high wavenumber variance than many previously reported values, but less than predicted by Surface Quasi-Geostrophy (SQG). Offshore, tracer spectra vary with eddy activity: slopes follow $k^0$ during active periods and $k^{1/3}$ during quieter phases, consistent with Kolmogorov scaling. Large-scale temporal changes are also evident, marked by shifts in water mass structure and temperature range, though the driving mechanisms remain uncertain. To contextualize these observations, a regional model is analyzed. Simulation-derived temperature variability diverges from glider observations across multiple spatial scales, including the mesoscale (e.g., eddies), and submesoscale (<80 km). These discrepancies suggest deficiencies in the model’s physical representation and parameterizations of lateral stirring.Item The distribution of aluminum in Beaufort Sea and the development of a sequential injection method for the determination of aluminum in natural waters(2010-04-29T23:26:48Z) Giesbrecht, Timothy; Cullen, Jay T.; Berg, David JayHere we report vertical profiles of dissolved (0.2 um filtered) Aluminum (Al) for eight stations in the Beaufort Sea in the Canadian Arctic, six of which are along a transect extending from the coastal shelf northeast of the Mackenzie River delta out to the Beaufort Sea. Sampling was performed aboard the CCGS Sir Wilfrid Laurier in September 2007 and all analyses were performed in a Class 100 clean space at the University of Victoria. Vertical profiles of dissolved Al in the water column displayed surface maxima, subsurface minima and a general increase in concentration with depth as is characteristic of a “scavenged” trace element in seawater. Concentrations of dissolved Al for the upper 1000 m were generally low ranging from the < 1 nmol kg-1 observed in the sub-surface minimum corresponding to the Pacific inflow layer and increasing to ~6-10 nmol kg-1 with depth. The surface maxima at stations for Al was associated with relatively fresh surface water (26-30 PSS) that is believed to be the result of seasonal sea-ice melt. This correlation suggests that the melting of sea-ice with entrained sediments may be an important mechanism for the delivery of Al and associated trace metals to the water column of the Beaufort Sea. We also report measurements of “total Al” (unfiltered and acidified to pH 1.7 for two year prior to analysis) for the Arctic Ocean which indicate that a significant proportion of Al in the water column is present in the > 0.2 um fraction. These measurements and the hydrographic data along the transect indicate the transport of a cold, saline, metal enriched water mass off of the continental shelf into the Canada Basin. This water mass appears to reflect the return of cold, high salinity slope water originally emplaced on the shelf by upwelling favourable winds. Alternatively, this water mass may be the product of brine exclusion from sea-ice formation during the previous winter that was unable to vacate the shelf due to the persistent upwelling observed throughout 2007. This finding suggests that the convection of cold, dense shelf water may be a mechanism for supplying the deep waters of the Arctic with an injection of water containing a significant Al content. In addition, a low volume sequential injection analysis (SIA) method is proposed for determination of elevated concentrations of Al, like those typically observed in coastal and river waters. A thorough optimization of the chemistry and instrumental parameters was performed along with an extensive investigation into potential interferents. The method was found to be largely free of interferents at environmentally relevant concentrations and was determined to have a detection limit of 24 nM. The precision of the method was reported to be 2% at 75 nmol kg-1 and analysis of the SLRS-4 certified reference material validated the accuracy of the method. Analysis of several samples that were previously analyzed via flow injection analysis (FIA) and standardized with consensus values of an open ocean reference material indicated the method returned comparable values for the Al concentration in the samples. Development and optimization of the SIA has resulted in an accurate and precise low-cost method of analysis that is both sensitive and relatively free from interference for the detection of nano-molar levels of Al in coastal and natural waters.Item Fine-scale structure in the ecology of juvenile Chinook Salmon at sea(2021-01-05) Duguid, William; Juanes, FrancisFisheries oceanography often aims to link large scale atmospheric and oceanic processes to variability and trends in the productivity of economically and ecologically valuable fish species. Declines in productivity of multiple species of Pacific Salmon (genus Oncorhynchus) in recent decades have spurred the search for a ‘smoking gun;’ an explanation that could explain trends in productivity across populations, regions and species. Despite extensive investment of research effort and funding, such an explanation remains elusive. The lack of a unifying explanation for declining productivity of Pacific Salmon may be due to the spatial and temporal complexity of their interactions with the marine environment. This complexity has historically been understudied, in part due to logistical limitations of research on Pacific Salmon at sea. This dissertation reports the results of a detailed study of how juvenile Chinook Salmon O. tshawytscha interact with marine habitats during their first summer and fall at sea. I first developed and validated a novel, hook and line-based method of sampling juvenile Chinook Salmon (microtrolling). I then reviewed and empirically compared methods (insulin like growth factor-1 concentration, RNA to DNA ratio, and scale circulus spacing) for indexing growth rate of juvenile salmon sampled in the ocean, a variable which is hypothesized to be related to subsequent survival. I integrated microtrolling with small vessel oceanography to relate distribution, diet, size and growth of juvenile Chinook Salmon to local scale variation in water column properties (stratification) and zooplankton community composition and abundance for five sites in the Southern Gulf Islands of the Salish Sea during a single summer (2015). While both stratification and zooplankton abundance and composition varied between sites, I failed to find support for the hypothesis that juvenile salmon distribution and growth was positively related to water column stratification at fine spatial scales. Juvenile Chinook Salmon were larger and faster growing where juvenile Pacific Herring Clupea pallasii were important in their diets, suggesting that Pacific Herring may play an important role in structuring the ecology of juvenile Chinook Salmon at sea. I built on 2015 results to conduct a detailed case study of juvenile Chinook Salmon ecology at two sites in the Southern Gulf Islands: Sansum Narrows and Maple Bay. Juvenile Chinook Salmon were consistently larger, more piscivorous, and faster growing at Sansum Narrows than Maple Bay across two years (2015 and 2016) despite lower zooplankton abundance at Sansum Narrows. Hydroacoustic surveys in September 2017 confirmed prior qualitative observations of elevated occurrence of forage fish schools (likely age-0 Pacific Herring) at Sansum Narrows, and a novel, mobile acoustic tag tracking survey suggested that fish tagged at Sansum Narrows may co-locate with juvenile Pacific Herring over the tidal cycle. By relating a scale circulus spacing-based growth index to reconstructed size intervals I found that juvenile Chinook Salmon at Sansum Narrows had been faster growing that those at Maple Bay before the transition to piscivory, and perhaps before migration to the ocean. These results suggest that intrinsic growth potential, or growth conditions during freshwater rearing or the transition to marine residence, interact with fine-scale structure in marine habitats to regulate growth potential of juvenile Chinook Salmon at sea. These factors also likely interact with the basin and interannual scale processes that have received extensive study as regulators of marine survival of juvenile Pacific salmon. These complex interactions should be taken into account when designing or interpreting studies to determine factors limiting productivity of Pacific Salmon populations.Item Flow and turbulence in a tidal channel(2017-06-26) Lu, Youyu; Lueck, R. G.An acoustic Doppler current profiler (ADCP) has been tried and found suitable for taking profiles of the time-mean three-dimensional velocity, vertical shear. Reynolds stress and turbulent kinetic energy (TKE) density in a coastal tidal channel. The velocity profiles have been used to reveal the existence of a log-layer. The data collected with the ADCP have been combined with fine- and microstructure data collected with a moored instrument (TAMI) to examine the TKE budget and turbulence characteristics in tidal flows. The ADCP was rigidly mounted to the bottom of the channel and the instrument was set to rapidly collect samples of along-beam velocities. In the derivation of the mean flow vector and the second-order turbulent moments, one must assume that the mean flow and turbulence statistics are homogeneous over the distance separating beam pairs. A comparison of the estimated mean velocity against the “error” velocity provides an explicit test for the assumption of homogeneity of the mean flow. The number of horizontal velocity estimates that pass a simple test for homogeneity increases rapidly with increasing averaging distance, exceeding 95% for distances longer than 55 beam separations. The Reynolds stress and TKE density are estimated from the variances of the along-beam velocities. Doppler noise causes a systematic bias in the estimates of the TKE density but not in the Reynolds stress. With increasing TKE density, the statistical uncertainty of the Reynolds stress estimates increases, whereas the relative uncertainty decreases. The spectra of the Reynolds stress and the TKE density are usually resolved; velocity fluctuations with periods longer than 20 minutes contribute little to the estimates. Stratification in the channel varies with the strength of the tidal flow and is weak below mid- depth. The ADCP measurements provide clear examples of secondary circulation, intense up/down- welling events, shear reversals, and transverse velocity shear. Profiles of the streamwise velocity are fitted to a logarithmic form with 1% accuracy up to a height, defined as the height of the log-layer, that varies tidally and reaches 20 m above the bottom during peak flows of 1 m s ⁻¹. The height is well predicted by 0.04u*/ω, where u * is the friction velocity and ω is the angular frequency of the dominant tidal constituent. The mean non-dimensional shear, [special characters omitted],is within 1% of unity at the 95% level of confidence inside the log-layer. Estimates of the rates of the TKE production and dissipation, eddy viscosity and diffusivity coefficients and mixing length, are derived by combining measurements with the ADCP and TAMI located at mid-depth. Near the bottom (z = 3.6 m), the production rate is 100 times larger than all other measurable terms in the TKE equation. Hence, the rate of production of TKE must be balanced by dissipation. The observed rate of production is proportional to the rate of dissipation calculated using the observed TKE density and mixing length, following the closure scheme of Mellor and Yamada (1974). This proportionality holds for the entire 3 decades of the observed variations in the rate of TKE production. At mid-depth, the eddy diffusivity of density and heat, deduced from microstructure measurements, agrees with the eddy viscosity derived from measurements with the ADCP. The scaling of the log-layer height with tidal frequency in the channel is comparable to the scaling with Coriolis parameter for the log-layer in steady planetary boundary layer. However, some results are inconsistent with those from boundary layers over horizontal homogeneous bottoms. The Reynolds stress is not constant within the log-layer, and its magnitude at 3.6 m above the bottom is 3 times smaller than the shear velocity squared [special characters omitted] derived from log-layer fitting. The peak of the non-dimensional spectrum for the Reynolds stress, when compared to measurements from atmospheric boundary layer, is shifted to higher wavenumbers by a factor of 2.5. One possible explanation for these discrepancies is the influence of horizontal inhomogeneity caused by bed forms.Item Invasion dynamics of a non-indigenous bivalve, Nuttallia obscurata, (Reeve 1857), in the Northeast Pacific(2005-12-31T01:04:51Z) Dudas, Sarah; Dower, John FThis thesis describes how life history characteristics of the varnish clam (Nuttallia obscurata), and interactions with the physical environment and other species, have contributed to its successful invasion in coastal British Columbia. Lab and field experiments were conducted to investigate varnish clam larval ecology (i.e. larval rearing experiments), adult population dynamics (i.e. annual population surveys, mark-recapture and length-frequency analysis, growth modeling) and ecological interactions with native species (i.e. predator/prey preference feeding trials). Using these results, a matrix demographic model was developed to determine which life history stage contributes the most to varnish clam population growth. Larval rearing experiments indicated that temperature and salinity tolerances of varnish clam larvae are comparable to native species, however the planktonic phase is slightly longer (3-8 weeks). Based on local oceanographic circulation, varnish clam larvae have the potential to disperse throughout their entire geographic range in just one reproductive season. Varnish clam population surveys revealed spatiotemporal variation in density and size. No relationships were evident between varnish clam density and the number or density of co-occurring bivalve species. Length-frequency analysis suggested that recruitment varies among sites, with high post-settlement mortality coinciding with high recruitment. The presence of similar recruitment pulses at geographically separate sites indicates regional scale processes may influence recruitment. Individual growth rates iii varied among sites, with higher growth corresponding to lower population densities and water temperature. Monthly survival rates ranged from 0.81 – 0.99 and were lower for clams 10-30 mm. Predator/prey preference feeding trials showed that crabs prefer varnish clams to local species when clam burial depth is limited. Crabs therefore have the potential to influence varnish clam distributions, particularly on beaches where the varnish clam is unable to bury deeply. Based on matrix demographic analysis, adult survival (e.g. clams ≥ 40 mm) is the most crucial factor for varnish clam population growth, and drives the observed population growth differences between sites. This study of the varnish clam invasion demonstrates that its success lies in both species (e.g. lengthy planktonic phase, high survival) and regional (e.g. favourable ocean circulation patterns for rapid dispersal) characteristics. Measures to reduce introductions should be targeted in areas where introductions are likely to have the furthest reaching impacts.Item Measurements of turbulence paramaters and observations of multipath arrivals in two contrasting coastal environments using acoustical scintillation analysis(2014-12-08) Di Iorio, Daniela; Farmer, David M.; Watton, ArthurItem Mixing and secondary circulation in Juan de Fuca Strait(2018-02-23) Ott, Michael William; Garrett, Christopher J. R.Estuaries, the regions where runoff of fresh water, soil, and contaminants first encounter the ocean, are also primary fishing and recreation areas. It is therefore important to understand the dynamics associated with mixing and currents within these bodies of water. Pollutants and fresh water from river runoff flow out to sea in the upper layer, while nutrient-carrying oceanic water returns beneath. While there have been many studies of the processes involved in this exchange flow, the dynamics and vertical structure of transverse flows are much less understood, despite the role these currents play in redistributing water properties and momentum throughout the estuary. One such estuary, Juan de Fuca Strait, is an ideal location in which to study estuarine exchange and the resulting cross-channel flows induced by internal friction, primarily because its length and smooth topography reduce the topograpic steering of currents. Historical current meter data from a number of deployments in Juan de Fuca Strait reveal that, while mean along-channel currents are roughly consistent with the thermal wind equation, cross-channel flows are not, particularly at mid-depths where transverse currents are largest. A momentum balance using historical sea level and current meter data suggests that the vertical eddy viscosity Aᵥ ≈ 0.02 m²s⁻¹ at interfacial depths in May. The mean circulation in Juan de Fuca Strait-depths is highly seasonal in nature, however, and larger values may be more appropriate in summer when the estuarine exchange peaks due to the freshet. Stronger friction is in turn associated with elevated mixing rates and increased transverse velocities. An Acoustic Doppler Current Profiler deployed in Juan de Fuca Strait in the summer of 1996 resolved the vertical structure of these velocities. Concurrent Current-Temperature-Depth data reveal that neither the along- nor the cross-channel currents are in geostrophic balance with the hydrographic structure, suggesting that the physical processes associatd with these currents are more localised than the five kilometre scales over which the hydrography was measured. Zooplankton within Juan de Fuca Strait comprise a significant part of the scattering cross-section upon which the ADCP depends. During their dusk migration into the euphotic zone to feed and dawn descent to escape predation, they do not act as passive backscatter targets for the Acoustic Doppler Current Profiler. Vertical migration velocities, measured from the backscatter intensity record, reached 0.03 m s⁻¹, suggesting that significant biases in the measured vertical velocity could be introduced. Little effect was actually seen in the velocity fields, however, even though the cross-sectional fraction of the zooplankton was an order of magnitude larger than the background. Mean currents in Juan du Fuca Strait reveal strong transverse flows at mid-depths, suggestive of interfacial Ekman layers. The along-channel estuarine exchange is significantly enhanced at neap tide, consistent with weaker mixing upstream. The cross-channel flows at interfacial depths are also substantially larger during neap tide, implying a fortnightly modulation of mixing rates within the strait. The ADCP was also used to measure the Reynolds stresses directly. These were found to be more than an order of magnitude larger at neap tide than during spring tide and were consistent with changes in the mean current over the spring-neap cycle. Reynolds stresses were maximal at mid-depth on the transition from ebb to flood, at which time the gradient Richardson numbers were smallest, suggesting that critical layer absorption of internal waves are important dynamically.Item Modelling of barotropic M2 tidal circulation with friction effects in Kyuquot Sound(2013-12-20) Wan, Di; Klymak, Jody Michael; Foreman, Michael George GarvinThis thesis examines the barotropic M2 tidal circulation and associated oceanographic properties in the Kyuquot Sound. The main contribution of this thesis is the development of a simple analytical model based on results from a Finite-Volume Coastal Ocean Model (FVCOM), describing a two-channel system. The simple analytical model allows us to estimate the energy dissipation rate in Crowther Channel and recognizes that friction is responsible for phase difference (between currents and elevation) variations as we move along the channel. This is done without running complex numerical models or collecting extensive observation data. We found a difference in velocity phases between a dominant channel (Kyuquot Channel) and a secondary channel (Crowther Channel) in Kyuquot Sound. The velocity phase response in the secondary channel is out of phase with the dominant channel, and varies when we move along the channel, while the elevation phases are consistent between the two channels. This result has a potentially significant impact on future biological and navigation decisions. Our research is also focused on getting a general understanding of the circulation in Kyuquot Sound, and offers an energy budget comparison between the analytical and numerical model results. These results allow the contrast between the simple analytical and the numerical model to be clarified, as the advantages and limitations of both are discussed in detail.Item Morphodynamics of a bedrock confined estuary and delta: The Skeena River Estuary(2020-12-07) Wild, Amanda Lily; Kwoll, Eva; Lintern, GwynBedrock islands add variation to the estuarine system that results in deviations from typical unconfined estuarine sediment transport patterns. Limited literature exists regarding the dynamics of seabed morphology, delta formation, sediment divergence patterns, and sedimentary facies classifications of non-fjordic bedrock confined systems. Such knowledge is critical to address coastal management concerns adequately. This research presents insights from the Skeena Estuary, a macrotidal estuary in northwestern Canada with a high fluvial sediment input (21.2-25.5 Mtyr-1). Descriptions on sub-environments, stratification, and sediment accumulation within the Skeena Estuary utilize HydroTrend model outputs of riverine sediment and discharge, Natural Resources Canada radiocarbon-dated sediment cores and grain size samples, and acoustic Doppler current profiler and conductivity-temperature-depth measurements from three field campaigns. Research findings delineate a fragmented delta structure with elongated mudflats and select areas of slope instability. Variations from well-mixed water circulation to lateral stratification, govern the slack tide flow transition and sediment transport pathways within seaward and landward passages of the estuary. Fostering a comprehensive understanding of bedrock confined estuary and delta systems has implications for the assessment of coastal management strategies, the productivity of ecological habitats, and the impacts of climate change within coastal areas.Item Oceanography and underwater acoustics in Resolute Bay, Nunavut: 2012-2015(2016-07-12) O'Neill, Caitlin; Vagle, Svein; Dosso, Stanley EdwardResolute Bay, a remote Arctic bay opening into Parry Channel, in the Canadian Arctic Archipelago, hosts diverse populations of marine mammals and fish at various times each year. These animals migrate through the bay following patterns linked to food availability and oceanographic conditions; however, these patterns are not well understood. The focus of this study was to measure the oceanographic properties of the waters in and around Resolute Bay and to record underwater sounds to obtain marine mammal temporal patterns and ambient sound levels. Results showed the water properties in Resolute Bay differed from the waters outside of the bay. Dissolved oxygen saturation levels in Resolute Bay decreased during ice-covered times, with lowest levels between May and July. Dissolved oxygen was replenished after the ice left the bay. Sudden changes in salinity, temperature, and dissolved oxygen were observed in Resolute Bay when outside waters entered. Mean third-octave band sound pressure levels were 85.3 dB re 1 μPa during high ice concentration, and 95.6 dB re 1 μPa during ice-free and freeze-up periods, and reached a maximum of 145.3 dB re 1 μPa when vessels were present. Belugas (Delphinapterus leucas) and narwhals (Monodon monocero) were only present in periods of low ice concentration, while bearded seals (Erignathus barbatus) and ringed seals (Pusa hispida) remained throughout the entire year.Item Optical properties of the waters of the Strait of Georgia, BC, Canada(2009-09-15T15:03:04Z) Loos, Eduardo Araujo; Costa, MayciraOcean optical studies have been conducted extensively in open ocean waters but less so in coastal waters where the influence of human population is increasing dramatically. The waters of the Strait of Georgia, British Columbia, Canada, are very important to the rearing of young salmon and herring, and to the fishing industry of British Columbia overall. The oceanography and plankton communities of the Strait have been researched extensively, however the forces behind the frequent occurrence of phytoplankton blooms in these waters still causes debate among researchers. In order to shed some light onto this topic and increase our knowledge of the characteristics of the waters of the Strait of Georgia, optical and bio-physical data were measured in the euphotic waters of the Strait in late spring and early summer of 2006. Hyperspectral optical data were measured for the first time in these waters using in situ optical profilers to collect inherent optical properties and radiometric quantities that were later used to derive apparent optical properties. The inherent optical properties included absorption coefficient, spectral beam attenuation coefficient, chromophoric dissolved organic matter absorption coefficient, particulate absorption coefficient, and particulate scattering coefficient. In situ irradiances and radiances were used to derive various diffuse attenuation coefficients. Water masses in the euphotic zone of the Strait of Georgia were then classified into three optical water masses according to their inherent optical properties using a clustering algorithm. OM1 waters were characterized by high and spectrally-invariant particulate scattering due to inorganic particles carried by the Fraser River plume. Absorption and scattering showed some spectral dependence in OM2 waters, with particles and chromophoric dissolved organic matter contributing equally to light absorption. The deepest waters, OM3, were the least influenced by the Fraser River, and the contribution of chromophoric dissolved organic matter to absorption was greater than in OM1 and OM2. A radiative transfer model, Hydrolight, was used to model some of the optical properties that were not collected in situ and then used to assess the magnitude of light available to phytoplankton in the Strait. Based on the minimum light requirements for photosynthesis of two of the main phytoplankton species in the Strait, the analysis presented here showed that there was enough light available for photosynthesis in the photosynthetically-available radiation range for the two phytoplankton species in all three optical water masses.Item Reconstructing Holocene East Asian climate and oceanographic history of the northern South China Sea: high-resolution records of pollen, spores, and dinoflagellate cysts(2019-01-02) Li, Zhen; Pospelova, VeraThis study contributes to developing terrestrial and marine palynological indicators of winter or summer monsoon signals as well as oceanographic environments of the South China Sea (SCS). The high-resolution reconstructions of Holocene East Asian Monsoon (EAM) climate and oceanographic condition of the northern SCS provide insights into regional climate events in the western low-latitude Pacific Ocean and their impacts on local oceanography and ecology. Sediment trap samples from the southwest Taiwan waters of the SCS in winter monsoon (March-April) and summer monsoon (July-August) seasons identify abundances of Pinus and Ulmus pollen as indicators of the winter monsoon whereas fern spores appeared to be indicators of the summer monsoon. The increased fluxes of dinoflagellate cyst (DC) taxa during summer are correlated with decreased sea-surface salinity (SSS) associated with nutrient-rich river inputs. DC distributions across the SCS show that some taxa are good indicators of changes in sea-surface temperature (SST), SSS, water depth and chlorophyll-a (chl-a) concentrations associated with EAM and oceanographic conditions. In particular, the concenrations of Brigantedinium spp. and cysts of Protoperidinium together with Echinidinium spp. are positively correlatd with SST in January and SST in July, and chl-a concentrations, respectively, which are linked to past monsoon strength and primary productivity. In total, four high cyst concentration regions have been observed off southern Vietnam, Borneo, Hainan, and South China. High-resolution palynological records from a sediment core in the northern SCS reflect several EAM climatic and oceanographic events over the last 12.5 kyr. A short-term Impagidinium decrease implied that the Taiwan Strait opened at ~11.7–11.0 cal kyr BP, with reduced Kuroshio Current influence when the East China Sea waters entered through the strait. Three Holocene relative sea-level stages were identified in the palynomorph records. The highest herb pollen abundances were observed before ~10.4 cal kyr BP, reflecting the shortest distance from the grassland sources on the exposed shelf at the low sea-level stand. High Brigantedinium and cysts of Protoperidinium abundances also indicate a near-shore environment. During ~10.4- ~6.8-6.0 cal kyr BP at the rising sea-level stage, fern spore abundances increased and DC abundances decreased. Consistently low total DC concentrations and high fern spore abundance were observed after ~6.8-6.0 cal kyr BP when the present oceanographic conditions were formed. Increased abundances of Pinus pollen reflected three strengthened winter monsoon intervals at ~5.5, 4.0 and 2.5 cal kyr BP under the present oceanographic conditions. The highest Dapsilidinium pastielsii abundances reflected the warmest interval at ~6.8-5.5 cal kyr BP of the northern SCS.Item Remote sensing chlorophyll-a in the Strait of Georgia(2007-12-17T17:20:04Z) Komick, Nicholas; Costa, MayciraThe main objective of this thesis was to evaluate the use of Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua imagery to estimate chlorophyll-a (chl) concentrations in the surface waters of the Strait of Georgia, located off the southwest coast of Canada. To meet this objective two components were addressed: (1) evaluate chl algorithms using ship-based radiometric and biophysical measurements, (2) evaluate atmospheric correction methods in conjunction with chl algorithms using MODIS Aqua imagery. In Chapter 2, biophysical and above-water reflectance measurements collected in 2006 were used to evaluate the OC3M, standard Garver-Siegel-Maritorena version~1 (GSM01), and a modified version of the GSM01 algorithms for estimating chl concentrations in the Strait. The Strait was generally classified as a case 2 water body, transitioning from chromophoric dissolved organic matter (CDOM) dominant in the central region to possibly particulate dominant in the Fraser River plume region. From these biophysical measurements, results showed that the OC3M algorithm was somewhat effective (r^2 = 0.552) outside the most turbid areas of the Fraser River plume. However, a systematic overestimation of lower chl concentrations was found, which may have been related to the higher CDOM absorption observed throughout the Strait. The standard GSM01 algorithm had moderately good agreement with measured CDOM absorption (r^2 = 0.584) and total suspended solids (TSS) concentrations (r^2 = 0.866), but was ineffective at estimating chl concentrations. Localized characterization of the CDOM absorption, through a hyperbolic CDOM model, improved the modified GSM01 results by providing better agreement with measured CDOM absorption (r^2 = 0.620) and TSS concentrations (r^2 = 0.935). By limiting the GSM01 algorithm to regions with lower combined CDOM and non-algal particulate absorption, the statistical relationship between measured and estimated chl improved (r^2 = 0.690). The further re-interpretation of phytoplankton absorption from the modified GSM01 algorithm with a two-component phytoplankton model resulted in a chl relationship with an r^2 = 0.702 and a linear slope closer to one. However, due to the nature of the GSM01 algorithm, its effectiveness is dependent the accurate characterization of the absorption and backscattering of the optically significant water constituents, which is not always available. Furthermore, the GSM01 algorithm effectiveness is contingent upon the accurate atmospheric correction of the shorter blue wavelengths within satellite imagery. Using unattended fluorometric chl measurements, different atmospheric correction approaches in conjunction with the standard OC3M chl algorithm and modified GSM01 algorithm from Chapter 2 were evaluated in Chapter 3. Atmospheric correction methods that were evaluated included: the standard near infrared (NIR) correction, a shortwave infrared (SWIR) correction, and an adapted version of the correction developed at the Management Unit of the North Sea Mathematical Models (MUMM). The NIR correction with the OC3M algorithm was statistically significant with an adjusted r^2 = 0.759 outside the most turbid portions of the Strait, but had a relatively large RMSE of 0.523, was limited to chl < 21 mg m^-3, and only estimated concentrations for 63% of the pixels. Effectiveness of the SWIR correction was limited with the OC3M algorithm because of the low percentage of estimated chl concentrations (21% of the pixels) and a lower adjusted r^2 = 0.572 outside the more turbid portion of the Strait. The adapted MUMM correction was the most effective, using the spatially averaged aerosol properties from the SWIR correction with the fixed NIR water-reflectance ratio defined by the MUMM method. The MUMM correction with the OC3M algorithm, when limited to pixels outside the Fraser River influence, had an adjusted r^2 = 0.720 and provided chl estimates for 84% of the pixels. The modified GSM01 algorithm was ineffective with all three atmospheric corrections due to the overcorrection of the 412 nm band. Several possible reasons for this overcorrection were identified, including the presence of absorbing aerosols and absorption from atmospheric nitrogen dioxide. When comparing spatial-temporal patterns in the MUMM corrected OC3M image with chl measurements, general spatial patterns and temporal trends match, with some explainable exceptions. Firstly, turbidity typically found near Fraser River plume makes the OC3M algorithm ineffective. Secondly, under lower aerosol reflectance conditions, the signal-to-noise ratio of the SWIR bands can make the spatial identification of the aerosol properties difficult.Item Sound scattering from oceanic turbulence(2008-11-25T23:05:09Z) Ross, Tetjana; Lueck, R. G.; Garrett, J. R.Co-located measurements of acoustic backscatter and temperature/velocity microstructure are used to confirm theoretical predictions of sound scatter from oceanic turbulence. The data were collected with a torpedo-shaped vehicle carrying four shear probes and two thermistors on its nose, and forward-looking 44.7 and 307 kilohertz echosounders (mounted 20 centimetres below the turbulence sensors). The vehicle was towed through the stratified turbulence that forms tidally over the lee side of a sill in a British Columbia fjord. Conventional downward-looking echosounder measurements were also made with a 100 kilohertz sounder mounted in the ship’s hull. Populations of amphipods, euphausiids, copepods and gastropods were present in the fjord (sampled with 335-micrometre mesh vertical net-hauls) and could be seen in the sounder data. These plankton net-hauls indicated that there were too few zooplankton in the turbulent regions to account for the scattering intensity. At both 44.7 and 307 kilohertz, scatter that is unambiguously correlated with turbulence was observed. Turbulent scatter is much stronger at the higher frequency, illustrating the mportance of salinity microstructure—long neglected in turbulent scattering models—and shedding some light on the form of the turbulent temperature-salinity co-spectrum. The turbulent temperature-salinity co-spectrum has never been measured directly. Although several models have been proposed for the form of the co-spectrum, they all produce unsatisfactory results when applied to the turbulent scattering equations (either predicting negative scattering cross-sections in some density regimes or predicting implausible levels of correlation between temperature and salinity at some scales). A new co-spectrum model is proposed and shown to be not only physically plausible in all density regimes, but also in reasonable agreement with the scattering data. At 307 kilohertz, the backscatter is mostly from salinity microstructure and, depending on the strength of the stratification, can be as strong as—or stronger than—the signal from a zooplankton scattering layer. This could easily confound zooplankton biomass estimates in turbulent regions. The two targets’ different natures (discrete targets versus a volume effect) often allow them to be distinguished even when they occur simultaneously. The key is sampling the same targets at multiple ranges. At long-range, discrete targets have a constant volume scattering strength proportional to their number density. The sampling volume, however, decreases as the targets approach the sounder. At some range there will be only one (or no) target in the sampling volume and the volume scattering strength will increase (or disappear) as the target continues to near the sounder. Turbulence, as a volume scattering effect, has no range dependence to its volume scattering strength. Thus, by examining the scattering nature at close range we can distinguish discrete targets (like zooplankton) from turbulence.Item A study of dissolved gaseous oxygen and nitrogen fluxes in the upper ocean(2015-08-31) McNeil, Craig Logan; Farmer, David M.