subject:(oceanography)

1. Li, Qing. Langmuir Turbulence and Its Effects on Global Climate.

Degree: Department of Earth, Environmental, and Planetary Sciences, 2018, Brown University

URL: https://repository.library.brown.edu/studio/item/bdr:792672/

► Ocean surface gravity waves, especially the resulting Langmuir turbulence, affect the ocean surface vertical mixing, yet are missing in most of the global climate models… (more)

▼ Ocean surface gravity waves, especially the resulting Langmuir turbulence, affect the ocean surface vertical mixing, yet are missing in most of the global climate models (GCM). The lack of explicit representation of such effects in GCMs may contribute to persistent biases in the simulated ocean mixed layer depth (MLD), air-sea fluxes and temperature distribution and tracer concentrations in the upper ocean. To assess the effects of Langmuir turbulence on the simulation of global climate, parameterizations are developed based on large eddy simulations (LES) of the ocean surface boundary layer (OSBL), which are able to simulate some of the key features of Langmuir turbulence. In particular, two effects of Langmuir turbulence are distinguished: enhanced vertical mixing within the OSBL, and enhanced entrainment at the base of the OSBL. The former is parameterized by a wave-related enhancement factor on the turbulent velocity scale in the K-Profile Parameterization (KPP) based on the scaling law of the root-mean-square vertical velocity from previous studies. The latter is parameterized by a wave-related unresolved shear term in KPP based on the scaling law of the entrainment buoyancy flux from a new set of LES experiments. The latter approach is supported by further analyses of the structure and anisotropy of Langmuir turbulence, which show no significant impact of Langmuir turbulence on the predominant processes that drive entrainment at the base of the OSBL except the extra energy through enhanced downward TKE transport. The modified KPP is then implemented and tested in the NCAR earth system model, CESM. A state-of-the-art ocean surface wave model, WAVEWATCH III, is incorporated into CESM to provide the necessary wave information. It is found that accounting for both effects of Langmuir turbulence in CESM significantly reduces the shallow MLD biases in the Southern Ocean, and improves the simulated intermediate water ventilation and ocean subsurface temperature. To avoid large computational and code development expenses of coupling a prognostic wave model with a climate model, two statistical approaches to parameterize the effects of Langmuir turbulence are explored and tested in CESM. Both appear to reproduce the effects of Langmuir turbulence as estimated using WAVEWATCH III with significantly less computational cost. Advisors/Committee Members: Fox-Kemper, Baylor (Advisor), Russell, James (Reader), Parmentier, Edgar (Reader), Marston, John (Reader), Lynch, Amanda (Reader), Hara, Tetsu (Reader).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Li, Q. (2018). Langmuir Turbulence and Its Effects on Global Climate. (Thesis). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:792672/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Li, Qing. “Langmuir Turbulence and Its Effects on Global Climate.” 2018. Thesis, Brown University. Accessed March 04, 2021. https://repository.library.brown.edu/studio/item/bdr:792672/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Li, Qing. “Langmuir Turbulence and Its Effects on Global Climate.” 2018. Web. 04 Mar 2021.

Vancouver:

Li Q. Langmuir Turbulence and Its Effects on Global Climate. [Internet] [Thesis]. Brown University; 2018. [cited 2021 Mar 04]. Available from: https://repository.library.brown.edu/studio/item/bdr:792672/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Li Q. Langmuir Turbulence and Its Effects on Global Climate. [Thesis]. Brown University; 2018. Available from: https://repository.library.brown.edu/studio/item/bdr:792672/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

College of William and Mary

2. Du, Jiabi. Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay.

Degree: PhD, Virginia Institute of Marine Science, 2017, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1516639465

► The efficiencies of water exchanges in both vertical and horizontal directions reflect the overall impact of various physical processes and serve as important indicators… (more)

▼ The efficiencies of water exchanges in both vertical and horizontal directions reflect the overall impact of various physical processes and serve as important indicators of physical control over a variety of ecological and biogeochemical processes. The vertical exchange between surface layers and bottom layers of a waterbody has proved to exert great control over the hypoxic condition, while the horizontal exchange between an estuary and coastal ocean determines the flushing capacity of the estuary and the retention rate of riverine materials. Various processes, such as tidal flushing, tidal mixing, gravitational circulation, and lateral circulation, can affect water exchange. Therefore, water exchange processes are complex and varying in time and space in estuaries. Besides the impact of numerous forcing variables, large-scale climate oscillation, sea-level rise, and human activities can result in a change of estuarine dynamics. Two biologically relevant timescales, residence time (RT) and vertical exchange time (VET), are used in this study to quantify the overall horizontal and vertical exchange, aiming to understand the physical transport control over the ecosystem functioning in a simpler way. A long-term simulation of VET in the Chesapeake Bay over the period of 1980-2012 revealed a high spatial and seasonal similarity between VET and the dissolved oxygen (DO) level in the mainstem of the Chesapeake Bay, suggesting a major control over the DO condition from the physical transport. Over the past three decades, a VET of about 20 days in the summer usually indicates a hypoxic condition in the mainstem. Strong correlation among southerly wind strength, North Atlantic Oscillation index, and VET demonstrates that the physical condition in the Chesapeake Bay is highly controlled by the large-scale climate variation. The relationship is most significant during the summer, during which time the southerly wind dominates throughout the Chesapeake Bay. By combining the observed DO data with modeled VET, decoupling the physical and biological effect on the DO condition becomes possible. Bottom DO consumption rate was estimated through a conceptual model that links DO with VET. Using observed DO data and modeled VET, the overall biological effect on the DO condition can be quantified. The estimated bottom DO consumption rate shows strong seasonal variation and its interannual variation is highly correlated with the nutrient loading. The response of an estuary ecosystem to a change of nutrient loading depends on the flushing capacity of the estuary, which is related to the horizontal water exchange. The overall flushing capacity can be quantified by resident time, which determines the retention and export rates of materials discharged in the estuary. The horizontal exchange in Chesapeake Bay was investigated over the period of 1980-2012. Quantified by the residence time (RT), the horizontal exchange in Chesapeake Bay exhibits high interannual and spatial variability. The 33-year simulation results show that…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Du, J. (2017). Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1516639465

Chicago Manual of Style (16^th Edition):

Du, Jiabi. “Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay.” 2017. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1516639465.

MLA Handbook (7^th Edition):

Du, Jiabi. “Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay.” 2017. Web. 04 Mar 2021.

Vancouver:

Du J. Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay. [Internet] [Doctoral dissertation]. College of William and Mary; 2017. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1516639465.

Council of Science Editors:

Du J. Impact of Climate Variation and Human Adaptation on the Physical Transport Processes and Water Exchange in Chesapeake Bay. [Doctoral Dissertation]. College of William and Mary; 2017. Available from: https://scholarworks.wm.edu/etd/1516639465

College of William and Mary

3. Irby, Isaac. Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts.

Degree: PhD, Virginia Institute of Marine Science, 2017, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1516639464

► Human impacts on the Chesapeake Bay through increased nutrient run-off as a result of land-use change, urbanization, and industrialization, have resulted in a degradation… (more)

▼ Human impacts on the Chesapeake Bay through increased nutrient run-off as a result of land-use change, urbanization, and industrialization, have resulted in a degradation of water quality over the last half-century. These direct impacts, compounded with human-induced climate changes such as warming, rising sea-level, and changes in precipitation, have elevated the conversation surrounding the future of water quality in the Bay. The overall goal of this dissertation project is to use a combination of models and data to better understand and quantify the impact of changes in nutrient loads and climate on water quality in the Chesapeake Bay. This research achieves that goal in three parts. First, a set of eight water quality models is used to establish a model mean and assess model skill. All models were found to exhibit similar skill in resolving dissolved oxygen concentrations as well as a number of dissolved oxygen-influencing variables (temperature, salinity, stratification, chlorophyll and nitrate) and the model mean exhibited the highest individual skill. The location of stratification within the water column was found to be a limiting factor in the models’ ability to adequately simulate habitat compression resulting from low-oxygen conditions. Second, two of the previous models underwent the regulatory Chesapeake Bay pollution diet mandated by the Environmental Protection Agency. Both models exhibited a similar relative improvement in dissolved oxygen concentrations as a result of the reduction of nutrients stipulated in the pollution diet. A Confidence Index was developed to identify the locations of the Bay where the models are in agreement and disagreement regarding the impacts of the pollution diet. The models were least certain in the deep part of the upper main stem of the Bay and the uncertainty primarily stemmed from the post-processing methodology. Finally, by projecting the impacts of climate change in 2050 on the Bay, the potential success of the pollution diet in light of future projections for air temperature, sea level, and precipitation was examined. While a changing climate will reduce the ability of the nutrient reduction to improve oxygen concentrations, that effect is trumped by the improvements in dissolved oxygen stemming from the pollution diet itself. However, climate change still has the potential to cause the current level of nutrient reduction to be inadequate. This is primarily due to the fact that low-oxygen conditions are predicted to start one week earlier, on average, in the future, with the primary changes resulting from the increase in temperature. Overall, this research lends an increased degree of confidence in the water quality modeling of the potential impact of the Chesapeake Bay pollution diet. This research also establishes the efficacy of utilizing a multiple model approach to examining projected changes in water quality while establishing that the pollution diet trumps the impact from climate change. This work will lead directly to advances…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Irby, I. (2017). Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1516639464

Chicago Manual of Style (16^th Edition):

Irby, Isaac. “Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts.” 2017. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1516639464.

MLA Handbook (7^th Edition):

Irby, Isaac. “Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts.” 2017. Web. 04 Mar 2021.

Vancouver:

Irby I. Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts. [Internet] [Doctoral dissertation]. College of William and Mary; 2017. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1516639464.

Council of Science Editors:

Irby I. Using Water Quality Models in Management - A Multiple Model Assessment, Analysis of Confidence, and Evaluation of Climate Change Impacts. [Doctoral Dissertation]. College of William and Mary; 2017. Available from: https://scholarworks.wm.edu/etd/1516639464

College of William and Mary

4. Ye, Fei. Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling.

Degree: PhD, Virginia Institute of Marine Science, 2017, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1516639591

► Geophysical fluid dynamics (GFD) models have progressed greatly in simulating the world’s oceans and estuaries in the past three decades, thanks to the development… (more)

▼ Geophysical fluid dynamics (GFD) models have progressed greatly in simulating the world’s oceans and estuaries in the past three decades, thanks to the development of novel numerical algorithms and the advent of massively parallel high-performance computing platforms. Study of inter-related processes on multi-scales (e.g., between large-scale (remote) processes and small-scale (local) processes) has always been an important theme for GFD modeling. For this purpose, models based on unstructured-grid (UG) have shown great potential because of their superior abilities in enabling multi-resolution and in fitting geometry and boundary. Despite UG models’ successful applications on coastal systems, significant obstacles still exist that have so far prevented UG models from realizing their full cross-scale capability. The pressing issues include the computation overhead resulting from large contrasts in the spatial resolutions, and the relative lack of skill for UG model in the eddying regime. Specifically for our own implicit UG model (SCHISM), the transport solver often emerges as a major bottleneck for both accuracy and efficiency. The overall goal of this dissertation is two-fold. The first goal is to address the challenges in tracer transport by developing efficient high-order schemes for the transport processes and test them in the framework of a community supported modeling system (SCHISM: Semi-implicit Cross-scale Hydroscience Integrated System Model) for cross-scale processes. The second goal is to utilize the new schemes developed in this dissertation and elsewhere to build a bona fide cross-scale Chesapeake Bay model and use it to address some key knowledge gaps in the physical processes in this system and to better assist decision makers of coastal resource management. The work on numerical scheme development has resulted in two new high-order transport solvers. The first solver tackles the vertical transport that often imposes the most stringent constraint on model efficiency (Chapter 2). With an implicit method and two flux limiters in both space and time, the new TVD2 solver leads to a speed-up of 1.6-6.0 in various cross-scale applications as compared to traditional explicit methods, while achieving 2nd-order accuracy in both space and time. Together with a flexible vertical gridding system, the flow over steep slopes can be faithfully simulated efficiently and accurately without altering the underlying bathymetry. The second scheme aims at improving the model skill in the eddying ocean (Chapter 4). UG coastal models tend to under-resolve features like meso-scale eddies and meanders, and this issue is partially attributed to the numerical diffusion in the transport schemes that are originally developed for estuarine applications. to address this issue, a 3rd-order transport scheme based on WENO formulation is developed, and is demonstrated to improve the meso-scale features. The new solvers are then tested in the Chesapeake Bay and adjacent Atlantic Ocean on small, medium and large domains respectively,…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Ye, F. (2017). Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1516639591

Chicago Manual of Style (16^th Edition):

Ye, Fei. “Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling.” 2017. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1516639591.

MLA Handbook (7^th Edition):

Ye, Fei. “Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling.” 2017. Web. 04 Mar 2021.

Vancouver:

Ye F. Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling. [Internet] [Doctoral dissertation]. College of William and Mary; 2017. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1516639591.

Council of Science Editors:

Ye F. Developing Efficient High-Order Transport Schemes for Cross-Scale Coupled Estuary-Ocean Modeling. [Doctoral Dissertation]. College of William and Mary; 2017. Available from: https://scholarworks.wm.edu/etd/1516639591

College of William and Mary

5. Wang, Zhengui. The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies.

Degree: PhD, Virginia Institute of Marine Science, 2017, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1516639690

► Algal blooms occur annually in many parts of the Chesapeake Bay. The causes of algal blooms are complex and can be different in different regions.… (more)

▼ Algal blooms occur annually in many parts of the Chesapeake Bay. The causes of algal blooms are complex and can be different in different regions. In this study, we will conduct data analysis for the observed data and adopt various methods to investigate algal bloom phenomenon in three separate regions in the oligo/poly-haline portion of the Bay. Chapter 1 provides a general introduction of the algal bloom research in the Chesapeake Bay. In Chapter 2, an observational analysis and a numerical study on the algal blooms in Back River were conducted. A hypothesis was made that high pH can trigger sediment phosphorus release, which in turn can enhance chlorophyll-a and further increase pH to form a positive feedback loop. to test this theory, water quality model ICM coupled onto SCHISM was applied in Back River to study the phenomenon. Moreover, a pH model was developed to describe the aquatic chemistry. The model results with and without pH model were compared with Bay Program observations for verifying our hypothesis. It proves the importance of sediment phosphorus release on the algal blooms in Back River. In Chapter 3, a theoretical study combined with data analysis on cyanobacteria blooms dynamics was conducted in the upper tidal James River. The theory integrates the physical transport and biological effects, which leads to a simple governing equation composed of an advection term and a phytoplankton net growth term, in both linear and nonlinear forms. In this study, we derived a general analytic solution to the equation. Then, we applied the theory in the tidal freshwater portion of the James River. The theoretical predictions of chlorophyll concentrations were compared with observational data and verified the validity of the solution. In addition, the factors related to the local chlorophyll maximum in tidal freshwater rivers were discussed. In Chapter 4, an observational analysis and numerical experiments were performed to investigate the algal bloom in the polyhaline of the Chesapeake Bay. This exploratory study is aimed to explain the broad distribution of C. polykrikoides blooms in the lower Bay and the sudden disappearance of the bloom in 2014. A hypothesis is made regarding the origin of C. polykrikoides cysts. In this hypothesis, the cysts are considered to be originated from coastal ocean and their transport is under the influence of wind patterns and gravitational circulation. In this study, the hydrodynamics in the lower Chesapeake Bay was first analyzed. Then, a series of particle tracking experiments were conducted for investigating the physical transport of C. polykrikoides cysts under different environmental conditions. Finally, water quality model ICM was used to simulate the algal blooms caused by C. polykrikoides in the lower Bay by incorporating the biological features of C. polykrikoides. The model can generate reasonable magnitude of the algal blooms in 2012, 2013 and simulate no algal bloom condition in 2014.The result indicates that C. polykrikoides cysts could be originated from the…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wang, Z. (2017). The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1516639690

Chicago Manual of Style (16^th Edition):

Wang, Zhengui. “The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies.” 2017. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1516639690.

MLA Handbook (7^th Edition):

Wang, Zhengui. “The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies.” 2017. Web. 04 Mar 2021.

Vancouver:

Wang Z. The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies. [Internet] [Doctoral dissertation]. College of William and Mary; 2017. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1516639690.

Council of Science Editors:

Wang Z. The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies. [Doctoral Dissertation]. College of William and Mary; 2017. Available from: https://scholarworks.wm.edu/etd/1516639690

College of William and Mary

6. Cai, Xun. Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study.

Degree: MS, Virginia Institute of Marine Science, 2018, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1550153628

► Submerged aquatic vegetation (SAV) plays a significant role in many aquatic systems, and impacts both physical and ecological quantities. It can baffle currents, attenuate waves,… (more)

▼ Submerged aquatic vegetation (SAV) plays a significant role in many aquatic systems, and impacts both physical and ecological quantities. It can baffle currents, attenuate waves, recycle nitrogen and phosphorus from the sediment bed, perform ecosystem function as a primary producer, and provide critical habitat for many aquatic species. Conversely, the invasive SAV, Egeria densa (Brazilian waterweed), in the San Francisco Bay & Delta has been a nuisance since its introduction into the system in the 1960s. It has displaced most of the native submersed aquatic plant species in the Delta and restructured the ecosystem, thus threatening the survival of several endangered native fishes such as Delta Smelt. Its impacts on the ecological system remain largely unknown and the need for assessment is growing. This multi-interdisciplinary study, incorporating biogeochemistry, hydrodynamics, and numerical computing and field survey data, accomplishes two main goals. The first goal is to develop a new SAV model imbedded into the unstructured-grid SCHISM-ICM framework. in addition to the advantages of directly simulating the SAV impact on hydrodynamics using high-resolution unstructured grids, this new SAV model can also simulate the competition between SAV and phytoplankton for light and nutrient supplies. The second goal is to apply the new model to Cache Slough Complex, Sacramento-San Joaquin Delta, to estimate the impact on the water quality from intervening SAV removal. Removal of SAV is already being studied in Little Hastings Tract and this study can serve to develop hypotheses for monitoring and ultimately guidance for managing SAV removal in the Bay-Delta region. We benchmark the new SAV model with the tests on the SAV biomass, growth and impacts on light supply and nutrient budget in the water column and sediment bed, respectively. Starting from a uniform biomass distribution, we simulate the evolution of biomass over seasonal scales and validate the calculated distribution with the observed distribution. The model is able to successfully simulate the SAV die-off process in areas where it is known to be unable to colonize. By applying the fully coupled SCHISM-ICM-SAV model in the Cache Slough Complex area, the changes of the water quality state variables due to SAV are estimated over spatial and seasonal scales. Generally, SAV increases the accumulation of phytoplankton by locally reducing flushing and thus increasing the residence time, but in the meantime, reduces its local growth rate due to light shading and nutrient competition. A combination of direct impact from SAV and indirect impact through changed phytoplankton results in changes in other water quality variables: dissolved oxygen and nutrients. SAV tends to increase oxygen and organic nutrients while decreasing inorganic nutrients. For this system, the feedback loop from SAV to the hydrodynamics plays the most important role in the water quality variables among all feedback loops.

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cai, X. (2018). Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1550153628

Chicago Manual of Style (16^th Edition):

Cai, Xun. “Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study.” 2018. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1550153628.

MLA Handbook (7^th Edition):

Cai, Xun. “Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study.” 2018. Web. 04 Mar 2021.

Vancouver:

Cai X. Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study. [Internet] [Masters thesis]. College of William and Mary; 2018. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1550153628.

Council of Science Editors:

Cai X. Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study. [Masters Thesis]. College of William and Mary; 2018. Available from: https://scholarworks.wm.edu/etd/1550153628

College of William and Mary

7. Liu, Zhuo. Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications.

Degree: PhD, Virginia Institute of Marine Science, 2018, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1550153651

► Storm surge and inundation induced by hurricanes and nor'easters pose a profound threat to coastal communities and ecosystems. These storm events with powerful winds, heavy… (more)

▼ Storm surge and inundation induced by hurricanes and nor'easters pose a profound threat to coastal communities and ecosystems. These storm events with powerful winds, heavy precipitation, and strong wind waves can lead to major flooding for cities along U.S. Coasts. Recent examples of Hurricane Irene (2011) in North Carolina and Virginia and Hurricane Sandy (2012) in New York City not only demonstrated the immense destructive power by the storms, but also revealed the obvious, crucial need for improved forecasting of storm tide and inundation. in part I, a large-scale unstructured-grid 3-D barotropic storm tide model SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) is developed with open ocean boundary aligning along the 60-degree West longitude to catch most Atlantic hurricanes that may make landfall along U.S. East and Gulf Coasts. The model, driven by high-resolution NAM (North America Mesoscale) and ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric fields, was coupled with Wind Wave Model (WWMIII) to account for wave effects, and used to simulate storm surge in 3-D barotropic mode rather than the traditional 2-D vertical average mode. For Hurricane Sandy, the fully coupled wave-current interaction 3-D model using ECMWF atmospheric forcing performs the best. The storm tide results match well with observation at all nine NOAA tidal gauges along the East Coast. The maximum total water level in New York City, is accurately simulated with absolute error of amplitude less than 8 cm, and timing difference within 10 minutes. The scenarios of "2-D" versus "3-D" and "with" versus "without" wind wave model were compared and discussed in details. Overall, the wave contribution amounts to 5-10% of surge elevation during the event. Also, the large-scale model with similar setup is applied to hindcasting storm tide during Hurricane Irene and the results are excellent when compared with observed water level along Southeast Coast and inside Chesapeake Bay. in part II, a high-resolution sub-grid inundation model ELCIRC-sub (Eulerian-Lagrangian CIRCulation) was developed from the original finite-volume-based ELCIRC model. It utilized the sub-grid method for imbedding high-resolution topography/bathymetry data into the traditional model grid and delivering the inundation simulation on the street level scale. The ELCIRC-sub contains an efficient non-linear solver to increase the accuracy and was executed in the MPI (Message Passing Interface) parallel computing platform to vastly enlarge the water shed coverage, and to expand the numbers of sub-grids allowed. The ELCIRC-sub is first validated with a wetting/drying analytic solution and then applied in New York City for Hurricane Sandy (2012). Temporal comparisons with NOAA and USGS water level gauges showed excellent performance with an average error on the order of 10 cm. It accurately captured the highest surge (during Hurricane Sandy) at Kings Point on both maximum surge height and the explosive surge profile. Spatial comparisons of the…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Liu, Z. (2018). Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1550153651

Chicago Manual of Style (16^th Edition):

Liu, Zhuo. “Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications.” 2018. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1550153651.

MLA Handbook (7^th Edition):

Liu, Zhuo. “Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications.” 2018. Web. 04 Mar 2021.

Vancouver:

Liu Z. Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications. [Internet] [Doctoral dissertation]. College of William and Mary; 2018. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1550153651.

Council of Science Editors:

Liu Z. Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications. [Doctoral Dissertation]. College of William and Mary; 2018. Available from: https://scholarworks.wm.edu/etd/1550153651

College of William and Mary

8. Qin, Qubin. Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms.

Degree: PhD, Virginia Institute of Marine Science, 2019, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1550153910

► The spatial and temporal variability of phytoplankton biomass in estuaries is determined by both local processes and transport processes. Local processes include biological processes (e.g.,… (more)

▼ The spatial and temporal variability of phytoplankton biomass in estuaries is determined by both local processes and transport processes. Local processes include biological processes (e.g., photosynthesis, respiration/excretion, and grazing) and settling, whereas transport processes include advective and diffusive transports. Transport processes have been demonstrated to regulate phytoplankton dynamics significantly by distributing both phytoplankton and other dissolved and particulate substances (e.g., nutrients, salts, sediments, and chromophoric dissolved organic matter). Yet, these transport properties lack a framework that unifies the pieced description of their various effects, and quantification of their importance under various environmental conditions. This dissertation highlights the role of horizontal transport processes on phytoplankton dynamics in estuaries, including the initiation of harmful algal blooms (HABs). in Chapter 2, the flushing effect of transport processes and its interaction with local processes are exclusively examined, and its relative importance on the variability of phytoplankton biomass is quantified and compared to that of the local processes over timescales from hours to years, using an introduced concept of transport rate that can be numerically computed. in Chapter 3, a simple yet inclusive mathematical model is developed to examine the temporal and spatial variabilities in phytoplankton biomass in response to the various effects of physical transport, under nutrient and light limiting conditions. For estuaries whose dominant nutrient loading is from river input, three basic patterns are revealed for the relationships between phytoplankton biomass and flushing time under various environmental conditions. in Chapters 4 and 5, the flushing effect of transport processes on the initiation of harmful algal blooms (HABs) in estuaries is investigated, which is then applied to examine the location and timing of the initiation of an annual Cochlodinium (recently renamed Margalefidinium) polykrikoides bloom in the lower James River. Theoretical analysis shows that the flushing is the key factor that affects HAB initiation in multiple interconnected systems, and a relatively long period of time (weeks) is required for a successful bloom. A HAB tends to be observed first in locations with relatively long residence time, such as tributaries or areas with large eddies. Multiple unconnected originating locations can co-exist within an estuary that highly depends on hydrodynamics and salinity. A numerical module for C. polykrikoides bloom is developed and built into a 3D numerical model - EFDC, which considers the competitive advantages of C. polykrikoides such as mixotrophic growth, swimming, grazing suppression, and resting cyst germination. Numerical model results show that the flushing effect determines the origins of C. polykrikoides blooms in the lower James River, and the sub-tributary of Lafayette River, which is characterized by relatively long residence time, is favorable for the…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Qin, Q. (2019). Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1550153910

Chicago Manual of Style (16^th Edition):

Qin, Qubin. “Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms.” 2019. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1550153910.

MLA Handbook (7^th Edition):

Qin, Qubin. “Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms.” 2019. Web. 04 Mar 2021.

Vancouver:

Qin Q. Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms. [Internet] [Doctoral dissertation]. College of William and Mary; 2019. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1550153910.

Council of Science Editors:

Qin Q. Impacts of Physical Transport on Estuarine Phytoplankton Dynamics and Harmful Algal Blooms. [Doctoral Dissertation]. College of William and Mary; 2019. Available from: https://scholarworks.wm.edu/etd/1550153910

College of William and Mary

9. Wang, Haixing. On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight.

Degree: MS, Virginia Institute of Marine Science, 2016, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1539617966

► The physical exchanges between shelf and slope water masses are important drivers of biological productivity in the shelfbreak region of the Mid-Atlantic Bight (MAB).… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wang, H. (2016). On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1539617966

Chicago Manual of Style (16^th Edition):

Wang, Haixing. “On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight.” 2016. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1539617966.

MLA Handbook (7^th Edition):

Wang, Haixing. “On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight.” 2016. Web. 04 Mar 2021.

Vancouver:

Wang H. On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight. [Internet] [Masters thesis]. College of William and Mary; 2016. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1539617966.

Council of Science Editors:

Wang H. On Shelf-Slope Water Mass Exchanges Near Washington Canyon and Norfolk Canyon in the Mid-Atlantic Bight. [Masters Thesis]. College of William and Mary; 2016. Available from: https://scholarworks.wm.edu/etd/1539617966

College of William and Mary

10. Wilkerson, Carissa N. Analysis of Extreme Water Levels in the Lower Chesapeake Bay.

Degree: MS, Virginia Institute of Marine Science, 2013, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1539617934

► In order to better understand storm tides in the Lower Chesapeake Bay, water levels during eleven storms at eight stations were analyzed using several… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wilkerson, C. N. (2013). Analysis of Extreme Water Levels in the Lower Chesapeake Bay. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1539617934

Chicago Manual of Style (16^th Edition):

Wilkerson, Carissa N. “Analysis of Extreme Water Levels in the Lower Chesapeake Bay.” 2013. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1539617934.

MLA Handbook (7^th Edition):

Wilkerson, Carissa N. “Analysis of Extreme Water Levels in the Lower Chesapeake Bay.” 2013. Web. 04 Mar 2021.

Vancouver:

Wilkerson CN. Analysis of Extreme Water Levels in the Lower Chesapeake Bay. [Internet] [Masters thesis]. College of William and Mary; 2013. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1539617934.

Council of Science Editors:

Wilkerson CN. Analysis of Extreme Water Levels in the Lower Chesapeake Bay. [Masters Thesis]. College of William and Mary; 2013. Available from: https://scholarworks.wm.edu/etd/1539617934

College of William and Mary

11. Moriarty, Julia M. Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits.

Degree: MS, Virginia Institute of Marine Science, 2012, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1539617920

► As part of a large interdisciplinary study, particulate fluxes in the Waipaoa River sedimentary system in New Zealand have been studied from the terrestrial… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Moriarty, J. M. (2012). Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1539617920

Chicago Manual of Style (16^th Edition):

Moriarty, Julia M. “Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits.” 2012. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1539617920.

MLA Handbook (7^th Edition):

Moriarty, Julia M. “Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits.” 2012. Web. 04 Mar 2021.

Vancouver:

Moriarty JM. Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits. [Internet] [Masters thesis]. College of William and Mary; 2012. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1539617920.

Council of Science Editors:

Moriarty JM. Transport and Fate of Sediment on the Waipaoa River Continental Shelf: Implications for the Formation and Reworking of Flood Deposits. [Masters Thesis]. College of William and Mary; 2012. Available from: https://scholarworks.wm.edu/etd/1539617920

College of William and Mary

12. Whitehead, Meaghan L. The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC.

Degree: MS, Virginia Institute of Marine Science, 2012, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1539617919

► Nitrogen (N) has been shown to limit primary production in many estuarine systems, including the New River Estuary (NRE), NC, a moderately eutrophied system… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Whitehead, M. L. (2012). The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1539617919

Chicago Manual of Style (16^th Edition):

Whitehead, Meaghan L. “The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC.” 2012. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1539617919.

MLA Handbook (7^th Edition):

Whitehead, Meaghan L. “The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC.” 2012. Web. 04 Mar 2021.

Vancouver:

Whitehead ML. The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC. [Internet] [Masters thesis]. College of William and Mary; 2012. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1539617919.

Council of Science Editors:

Whitehead ML. The Role of Benthic Nitrogen Fixation as a Source of New Nitrogen to the New River Estuary, NC. [Masters Thesis]. College of William and Mary; 2012. Available from: https://scholarworks.wm.edu/etd/1539617919

College of William and Mary

13. Friedman, Jaclyn Rain. Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem.

Degree: MS, Virginia Institute of Marine Science, 2019, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1582642580

► Declining water quality, in addition to hypoxia and eutrophication, may have a significant impact on the seasonality of biogeochemical parameters throughout the mainstem of the… (more)

▼ Declining water quality, in addition to hypoxia and eutrophication, may have a significant impact on the seasonality of biogeochemical parameters throughout the mainstem of the Chesapeake Bay. The carbonate (CO2) system in the Chesapeake Bay experiences seasonal and spatial complexities and is influenced by both natural and anthropogenic variability. Although site-specific studies investigating CO2-system variability exist within the Chesapeake Bay, few studies have investigated the seasonality of the CO2-system throughout the entire mainstem. Additionally, recent comprehensive studies investigating over 50 estuaries along the East Coast of the United States suggest that estuarine systems are heterotrophic and act as sources of CO2 to the atmosphere; this current paradigm does not apply to the mainstem of the Chesapeake Bay. The research presented here will assess the net annual source/sink status of atmospheric CO2 in the mainstem, along with an evaluation of annual net community production and trophic status, which is assessed based on a mass balance of dissolved inorganic carbon (DIC). Discrete observations of DIC and total alkalinity (TA) are collected at 17 stations throughout the mainstem of the Bay on four cruises between November 2016 and July 2017. The latitudinal salinity gradient along the mainstem of the Bay results in elevated DIC and TA concentrations at the mouth of the Bay associated with inflowing Atlantic Ocean waters. Minimum concentrations of DIC and TA are associated with fresher waters, delivered mainly by the Susquehanna River, at the head of the Bay. The spatial gradients in DIC and TA are observed regardless of season. Spatial variability of the partial pressure of CO2 (pCO2) is observed throughout the surface waters of the estuary, with undersaturation of CO2 with respect to the atmosphere in the upper Bay over the complete seasonal cycle, and supersaturation with respect to atmospheric CO2 in the lower Bay during the warm seasons. The spatial and seasonal distribution of pH and saturation state of aragonite (Ω) are more variable throughout the mainstem, as the seasonality of these parameters are different in each region. The physical (air-sea CO2 exchange and mixing) and biological (photosynthesis and respiration) drivers of CO2-system seasonality is examined throughout the mainstem Bay. In the deep, northern channel of the mainstem, seasonal CO2-system variability is larger than the lower Bay regions that are more directly influenced by exchange with Atlantic Ocean shelf waters. Overall, when averaged over the 2016/2017 seasonal cycle used in this analysis, the mainstem of the Chesapeake Bay is found to be net autotrophic and a sink of atmospheric CO2.

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Friedman, J. R. (2019). Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem. (Masters Thesis). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1582642580

Chicago Manual of Style (16^th Edition):

Friedman, Jaclyn Rain. “Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem.” 2019. Masters Thesis, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1582642580.

MLA Handbook (7^th Edition):

Friedman, Jaclyn Rain. “Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem.” 2019. Web. 04 Mar 2021.

Vancouver:

Friedman JR. Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem. [Internet] [Masters thesis]. College of William and Mary; 2019. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1582642580.

Council of Science Editors:

Friedman JR. Seasonal Variability of the Co2-System Throughout the Chesapeake Bay Mainstem. [Masters Thesis]. College of William and Mary; 2019. Available from: https://scholarworks.wm.edu/etd/1582642580

14. Williams, Rebecca. TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES.

Degree: 2013, University of Rhode Island

URL: https://digitalcommons.uri.edu/oa_diss/130

► Oxygen minimum zones (OMZs) are areas in which midwater oxygen concentration can be significantly lower than in non OMZ areas at comparable depths. OMZs are… (more)

▼ Oxygen minimum zones (OMZs) are areas in which midwater oxygen concentration can be significantly lower than in non OMZ areas at comparable depths. OMZs are of great interest because of the limits oxygen availability places on life. The potential for OMZ expansion with warming of the oceans has refocused attention on the importance of these areas and their potential impacts on the global carbon cycle. The large open ocean OMZs of the Eastern Tropical Pacific and Arabian Sea are notable for their size, thickness, and the intensity of oxygen depletion ( Here, I use measurements of natural abundance carbon and nitrogen stable isotopes (as δ13C and δ15N, respectively) to investigate zooplankton diets within the Eastern Tropical Pacific OMZ. The use of stable isotopes rests on the premise that the δ13C values of consumers are similar to their ultimate organic carbon source, primary producers, while the δ15N values reflect more proximal sources of organic matter and can be used to evaluate trophic position. To examine the energy sources and trophic interactions of zooplankton in the Eastern Tropical North Pacific OMZ, samples were collected in 2007 and 2008 at two stations, the Tehuantepec Bowl (TB) and Costa Rica Dome (CRD), using vertically stratified MOCNESS net tows between 0-1200 m. Environmental data were collected concurrently with zooplankton samples and particulate organic matter (POM) was collected with McLane large volume in situ pumps. Zooplankton samples were separated into four size fractions and processed at sea to select aliquots for bulk (mixed zooplankton) analysis and individual taxa samples were analyzed for stable carbon and nitrogen isotopes. Bulk zooplankton and POM δ13C and δ15N values revealed strong depth gradients associated with oxyclines (oxygen gradients) at the upper and lower OMZ boundaries. While the source of low δ13C values at the upper oxycline could not be determined, the sharp gradient in δ15N values at the lower oxycline indicated a depth zone of increased trophic progression. Furthermore, δ15N values were significantly lower at CRD than at TB, suggesting that nitrogen fixation may have been present at CRD. Low δ13C-δ15N correlations in all zones at CRD suggested that the products of nitrogen fixation were transferred to zooplankton food webs throughout the sampled water column. Stable isotope values of individual zooplankton taxa also suggested that zooplankton collected within and above the OMZ core likely fed on material from the upper 110m of the water column, while lower oxycline zooplankton likely consumed deep POM exiting the OMZ. There were significant differences in the isotope values of zooplankton taxa with different trophic strategies (particle feeders, omnivores, carnivores) in the OMZ core and lower oxycline community, but not for those living in the mixed layer and upper oxycline. Furthermore, calculated trophic levels for lower oxycline taxa were much higher than expected based on a priori trophic level designations. The copepod Eucalanus inermis is thought to diapause…

Subjects/Keywords: Oceanography

3 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Williams, R. (2013). TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES. (Doctoral Dissertation). University of Rhode Island. Retrieved from https://digitalcommons.uri.edu/oa_diss/130

Chicago Manual of Style (16^th Edition):

Williams, Rebecca. “TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES.” 2013. Doctoral Dissertation, University of Rhode Island. Accessed March 04, 2021. https://digitalcommons.uri.edu/oa_diss/130.

MLA Handbook (7^th Edition):

Williams, Rebecca. “TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES.” 2013. Web. 04 Mar 2021.

Vancouver:

Williams R. TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES. [Internet] [Doctoral dissertation]. University of Rhode Island; 2013. [cited 2021 Mar 04]. Available from: https://digitalcommons.uri.edu/oa_diss/130.

Council of Science Editors:

Williams R. TROPHIC ECOLOGY OF OXYGEN MINIMUM ZONE ZOOPLANKTON REVEALED BY CARBON AND NITROGEN STABLE ISOTOPES. [Doctoral Dissertation]. University of Rhode Island; 2013. Available from: https://digitalcommons.uri.edu/oa_diss/130

15. Dilmahamod Ahmad Fehmi. The biophysical processes controlling the South-East Madagascar Bloom.

Degree: PhD, Oceanography, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/29265

► Phytoplankton blooms are ecological hotspots in the ocean, and are fundamental to the biogeochemical cycling of elements, the storage of carbon and the ability to… (more)

▼ Phytoplankton blooms are ecological hotspots in the ocean, and are fundamental to the biogeochemical cycling of elements, the storage of carbon and the ability to regulate the atmospheric carbon dioxide; and the life in the ocean. The South-East Madagascar Bloom, one of the largest blooms in the global ocean, coexists with the poleward flowing South-East Madagascar Current (SEMC), the eastward flowing South Indian Ocean Countercurrent (SICC) as well as westward-propagating surface and subsurface-intensified eddies. This austral summer bloom extends largely towards the open ocean, from the Madagascan coasts up to ~65°E and it exhibits an intriguing interannual variability. A variety of observational datasets as well as a high resolution coupled physical-biogeochemical model, based on CROCOPISCES, are used to explore the biophysical processes associated with the bloom and these westward-propagating eddies. Based on historical observational data, the bloom is shown to occur in a region of shallow mixed layer, with the surface layer exhibiting lower salinity, a possible signature of the coastal poleward flowing SEMC waters. The testing of various hypotheses revealed a dampening of the coastal current-driven upwelling south-east of Madagascar during bloom months. A dipole mesoscale feature is also prevalent close to the Madagascan coast during the bloom, from which a new hypothesis emerges. This new hypothesis states that the region south/south-east of Madagascar, influenced by local mesoscale turbulence, acts as a gate for the SEMC to flow either towards the African continent, or into the bloom region through an early retroflection, hence fertilizing the bloom. The model produces a sporadic enhancement of chlorophyll-a in the subsurface levels, associated with a low-salinity surface signature. The mean local circulation associated with the simulated bloom also reveals a dipole structure, as in observed datasets. Nitrate from subsurface levels (upwelling) as well as from the Madagascan coast (advection) is shown to influence the simulated bloom. A Lagrangian experiment shows dispersion of higher percentages of particles in the bloom region during bloom years and south of Madagascar during non-bloom years. Mesoscale eddies, originating close to Australia and which propagate westward towards southern Africa, can potentially impact the South-East Madagascar Bloom. In this study, a vast majority of these features have been shown to be subsurface-intensified eddies. A co-located eddy tracking dataset with Argo profiling floats are used to devise a subsurface-eddy identification method, which is based on the steric dynamic height anomaly of a specific eddy. Adding to the `eddy-zoo', these eddies are termed `SIDDIES' (South Indian ocean eDDIES), occurring as surface (surfSIDDIES) and subsurface (subSIDDIES) features. They travel along the latitudinal band range of 15°S to 35°S which we name the ‘SIDDIES corridor’. Advecting warm and fresh water during their propagation, cyclonic (anticyclonic) subSIDDIES contribute about 58%… Advisors/Committee Members: Reason Christopher (advisor).

Subjects/Keywords: oceanography

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fehmi, D. A. (2018). The biophysical processes controlling the South-East Madagascar Bloom. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/29265

Chicago Manual of Style (16^th Edition):

Fehmi, Dilmahamod Ahmad. “The biophysical processes controlling the South-East Madagascar Bloom.” 2018. Doctoral Dissertation, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/29265.

MLA Handbook (7^th Edition):

Fehmi, Dilmahamod Ahmad. “The biophysical processes controlling the South-East Madagascar Bloom.” 2018. Web. 04 Mar 2021.

Vancouver:

Fehmi DA. The biophysical processes controlling the South-East Madagascar Bloom. [Internet] [Doctoral dissertation]. University of Cape Town; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/29265.

Council of Science Editors:

Fehmi DA. The biophysical processes controlling the South-East Madagascar Bloom. [Doctoral Dissertation]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/29265

University of Cape Town

16. Bone, Emma Lewis. A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean.

Degree: PhD, Oceanography, 2019, University of Cape Town

URL: http://hdl.handle.net/11427/31089

► The apparent fluorescence quantum yield of chlorophyll-a (ΦF ), i.e. the ratio of photons emitted as chlorophyll-a fluorescence to those absorbed by phytoplankton, serves as… (more)

▼ The apparent fluorescence quantum yield of chlorophyll-a (ΦF ), i.e. the ratio of photons emitted as chlorophyll-a fluorescence to those absorbed by phytoplankton, serves as a first order measure of photosynthetic efficiency and a photophysiological indicator of the resident phytoplankton community. Drivers of ΦF variability, including taxonomy, nutrient availability, and light history, differ in magnitude of influence across various biogeographic provinces and seasons. A Multi-Exciter Fluorometer (MFL, JFE Advantech Co., Ltd.) was selected for use in in situ ΦF derivation and underwent an extensive radiometric calibration for this purpose. Wavelength-specific ΦF was determined for 66 in situ field stations, sampled in the Atlantic Southern Ocean during the austral winter of 2012 and summer of 2013/ 2014. Phytoplankton pigments, macronutrient concentrations, and light levels were simultaneously measured to investigate their influence on ΦF . While no relationship was observed between macronutrient levels and ΦF , an inverse relationship between light and ΦF was apparent. This was likely due to the influence of speciesspecific fluorescence quenching mechanisms employed by local populations. ΦF derived from ocean colour products (Φsat) from the Moderate Resolution Imaging Spectroradiometer (MODIS) were compared to in situ ΦF to assess the performance of three existing Φsat algorithms. Results indicate that accounting for chlorophyll-a fluorescence reabsorption, the inherent optical properties of the surrounding water column, and the sensor angle of observation, is crucial to reducing Φsat uncertainty. A hybrid combination of two of the algorithms performed best, and was used to derive Φsat for stations co-located to in situ iron measurements in the Atlantic Southern Ocean. A significant negative relationship was observed, indicative of the effects of iron availability on quantum yield and its potential as a proxy for iron limitation. However, separating the individual contributions of light, taxonomy, and iron limitation to Φsat variability remains a challenge. A time series analysis of Φsat was also undertaken, which revealed a prominent Φsat seasonal cycle. Ultimately, increased in situ sampling would expedite the development of improved Φsat algorithms; the routine retrieval of Φsat would offer insight into phytoplankton dynamics in undersampled regions such as the climate relevant Southern Ocean. Advisors/Committee Members: Vichi, Marcello (advisor), Thomalla, Sandy J (advisor), Bernard, Stewart (advisor), Smith, Marié E (advisor), Ryan-Keogh, Thomas. J (advisor).

Subjects/Keywords: oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Bone, E. L. (2019). A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/31089

Chicago Manual of Style (16^th Edition):

Bone, Emma Lewis. “A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean.” 2019. Doctoral Dissertation, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/31089.

MLA Handbook (7^th Edition):

Bone, Emma Lewis. “A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean.” 2019. Web. 04 Mar 2021.

Vancouver:

Bone EL. A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean. [Internet] [Doctoral dissertation]. University of Cape Town; 2019. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/31089.

Council of Science Editors:

Bone EL. A novel approach to investigating chlorophyll-a fluorescence quantum yield variability in the Southern Ocean. [Doctoral Dissertation]. University of Cape Town; 2019. Available from: http://hdl.handle.net/11427/31089

University of Cape Town

17. Gamoyo, Majambo J. Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean.

Degree: PhD, Oceanography, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/29633

► Coral reef degradation is happening at an alarming rate all over the world due to multiple stressors with elevated sea surface temperature being the root… (more)

▼ Coral reef degradation is happening at an alarming rate all over the world due to multiple stressors with elevated sea surface temperature being the root cause. Using the Regional Ocean Modelling System and an individual-based model for the western Indian Ocean, this thesis explored the general circulation patterns (both large and mesoscale) important to dispersal and connectivity of broadcast corals while identifying regions that act as a source of larvae and those that receive larvae. Because habitat destruction and fragmentation through severe bleaching and mortality threaten coral reef health, projected thermal stress from Global Climate Models was explored to quantify future bleaching scenarios that might impact the reproductive timing and larval dispersal. Evaluation of the ROMS configuration for the western Indian Ocean shows that the basin-scale circulation patterns of the region are appropriately captured with the mean volume transports consistent with those derived from observation. Using the eddy detection algorithm, a description of the Southern Gyre as a key aspect of the Somali Current system was identified. The Southern Gyre is associated with barotropic instabilities associated with the northward flowing Somali Current. Rossby waves arriving at the East African coast and the strength of the monsoon winds are also responsible for the evolution and intensification of the gyre. The aggregated trajectories from the Lagrangian model highlight the dominant dispersal pathways and barriers to dispersal following release. The general circulation plays an important role in the dispersal of reef larvae over the study region. At a short pelagic larval duration, most of the released larvae settle back to or near natal reefs, but as the pelagic duration increases, the number of isolated reefs and islands decreases. Even with increased pelagic duration, some reefs (e.g., Agalega and Tromelin) are completely isolated. The mean dispersal distance from release to settlement varied across the region with larvae released along the East African coast dispersed an average of 405 km before settling while those in the Seychelles archipelago dispersed about 101 km. Different blocks of clusters were observed with 16 clusters observed when the pelagic duration is shorter (5 days), compared to seven clusters when the pelagic duration is longer (60 days). The warming trends and bleaching thermal stress shows that among the 636 reef pixels in the study region, about 56% showed positive sea surface temperature trends during the study period (1985- 2016). The frequency of bleaching level thermal stress has also increased over the same period, a tendency that climate models project to continue. Even under optimistic scenarios (such as the Representative Concentration Pathway RCP 4.5), most coral reefs are projected to experience severe bleaching and possible mortality by the 2050s. Low to moderate thermal stress are projected over reefs along the East African coast and near the northwest tip of Madagascar and thus these regions may… Advisors/Committee Members: Reason, Christopher (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gamoyo, M. J. (2018). Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/29633

Chicago Manual of Style (16^th Edition):

Gamoyo, Majambo J. “Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean.” 2018. Doctoral Dissertation, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/29633.

MLA Handbook (7^th Edition):

Gamoyo, Majambo J. “Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean.” 2018. Web. 04 Mar 2021.

Vancouver:

Gamoyo MJ. Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean. [Internet] [Doctoral dissertation]. University of Cape Town; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/29633.

Council of Science Editors:

Gamoyo MJ. Modelling dispersal and connectivity of broadcast spawning corals in the Western Indian Ocean. [Doctoral Dissertation]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/29633

University of Cape Town

18. Philibert, Marie Catherine Raïssa. A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters.

Degree: Image, Oceanography, 2015, University of Cape Town

URL: http://hdl.handle.net/11427/16794

► Nitrification is the oxidation of ammonium to nitrate through a two step biological process. Nitrification in the euphotic zone has, in the past, been considered… (more)

▼ Nitrification is the oxidation of ammonium to nitrate through a two step biological process. Nitrification in the euphotic zone has, in the past, been considered negligible even though quantifying this process correctly is important when linking carbon export to nitrate uptake by phytoplankton. However, studies of both nitrogen uptake and nitrification rates in surface waters are rare. This thesis presents such data for the Southern Ocean and St-Helena Bay, located in the Southern Benguela upwelling system. Using 15N tracers, Nitrogen uptake and regeneration rates were measured in the Southern Ocean (during a winter cruise in July 2012 and a summer cruise in February-March 2013) and St-Helena Bay (during three studies in November 2011, March 2012 and March 2013). In St-Helena Bay, the upwelling (bloom) cycle was one of the main drivers of the nitrogen cycle. As the bloom cycle started, nitrate uptake rates (5:47 ± 670:48nmol∙L⁻¹∙h⁻¹) and nitrite regeneration (4:36 - 1:28 ± 22:83 - 1:63nmol∙L⁻¹∙h⁻¹) were high but the contribution of nitrification to the nitrate demand was low. Nitrite regeneration at this time could have been driven by phytoplankton excretion. In contrast, at the end of the bloom cycle, nitrate uptake rates were low and was exceeded by nitrate regeneration rates (25:34 - 6:16 ± 82:74 - 34:41nmol∙L⁻¹∙h⁻¹). Nitrite regeneration decreased and was most likely due to ammonium oxidation at this stage of the upwelling cycle. Nitrification in the Southern Ocean was more variable than in St-Helena Bay. It was only detected at five stations out of fifteen and the accuracy of the high nitrite oxidation rates (37:21 - 9:13 ± 217 - 88nmol∙L⁻¹∙h⁻¹) observed can only be assessed with repeat measurements. Nitrate uptake rates ranged from 0.07 to 57:00nmol∙L⁻¹∙h⁻¹ while ammonium uptake rates ranged from 0.81 - 160:94nmol∙L⁻¹∙h⁻¹. The nitrogen uptake rates were similar for both seasons. Using multivariate statistical approach, it was found that during winter, in the Southern Ocean, light and ammonium availability were the most important factors regulating nitrogen uptake while in the late summer, changes in the mixed layer depth had a larger effect. This study provides new observational data for two undersampled regions and contributes to further the mechanistic understanding of the factors regulating nitrogen uptake and nitrification in the Southern Ocean and St-Helena Bay. Advisors/Committee Members: Waldron, Howard (advisor), Clark, Darren (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Philibert, M. C. R. (2015). A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/16794

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Philibert, Marie Catherine Raïssa. “A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters.” 2015. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/16794.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Philibert, Marie Catherine Raïssa. “A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters.” 2015. Web. 04 Mar 2021.

Vancouver:

Philibert MCR. A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters. [Internet] [Thesis]. University of Cape Town; 2015. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/16794.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Philibert MCR. A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters. [Thesis]. University of Cape Town; 2015. Available from: http://hdl.handle.net/11427/16794

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

19. Mashifane, Thulwaneng. Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system.

Degree: Image, Oceanography, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/27309

► Two coupled physical-biogeochemical models namely, (Regional Ocean Modelling System and Biogeochemical of Eastern Boundary Upwelling Systems) ROMS-BioEBUS (3D) and (Nucleus for European Modelling of the… (more)

▼ Two coupled physical-biogeochemical models namely, (Regional Ocean Modelling System and Biogeochemical of Eastern Boundary Upwelling Systems) ROMS-BioEBUS (3D) and (Nucleus for European Modelling of the Ocean and Biogeochemical Flux Model) NEMO-BFM (1D) are applied in the Benguela upwelling system to understand biogeochemical interactions and their related feedback processes. The models are formulated differently but achieve similar objectives with respect to the physics and biogeochemistry. The BioEBUS model is used to simulate nitrogen processes under oxic and suboxic conditions in upwelling systems with no option for other cycles. Intermediary nitrogen processes, nitrous oxide production and nitrogen loss mechanisms are studied using this model. Physical and advection processes that drive the oceanic nitrogen cycle in the region are also studied with BioEBUS. The BFM is used to understand the implications of the nitrogen loss and suboxic-anoxic conditions on related biogeochemical cycles. The 1D model was selected for its low computational costs and flexibility for addition of new code. BFM includes the carbon, nitrogen, phosphorus, silicate, iron cycles and hydrogen sulphide production, which is a known occurrence in the Namibian shelf waters. New variables, nitrite and nitrous oxide production, are added in BFM to complete the nitrogen cycle. The nitrification process in BFM is also formulated in two stages as in BioEBUS to obtain comparative results in both models. Both models are compared and validated with data from the Maria S. Merian (MSM) 19/1b cruise and available products respectively. Simulated results from BioEBUS show primary and secondary nitrite maxima in the Benguela shelf waters. The primary nitrite maxima are attributed to nitrification and nitrate assimilation. Secondary nitrite maxima accumulate in the Angola-Benguela Front (ABF) oxygen minimum zone (OMZ) and are attributed to denitrification. Off Walvis Bay, these secondary nitrite maxima and ammonium are thought to be consumed by high rates of anaerobic ammonium oxidation (anammox). The nitrite maxima are restricted to the shelf off Walvis Bay and advected offshore in the ABF region. Interchanges between the poleward South Atlantic Central Water (SACW) and the equatorward, well-oxygenated Eastern South Atlantic Central Water (ESACW) drive the seasonality of nitrogen processes in the Benguela. Nitrous oxide concentrations are high in the ABF as a result of nitrification and accelerated production under suboxic conditions. Off Walvis Bay, nitrous oxide production is low when compared to the ABF. Nitrous oxide production in the ABF occurs in thermocline, intermediate and deeper water masses. Off Walvis Bay, nitrous oxide production in deeper water masses is missing because of the shallow coast. High fixed nitrogen fluxes in the Benguela are attributed to nitrification rather than anammox and denitrification. Simulated results show denitrification to be the dominant nitrogen loss mechanism in the Benguela shelf waters. Simulated results from BFM… Advisors/Committee Members: Vichi, Marcello (advisor), Waldron, Howard (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mashifane, T. (2017). Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/27309

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Mashifane, Thulwaneng. “Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system.” 2017. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/27309.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Mashifane, Thulwaneng. “Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system.” 2017. Web. 04 Mar 2021.

Vancouver:

Mashifane T. Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/27309.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Mashifane T. Shelf biogeochemical interactions and feedback processes in the Benguela upwelling system. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/27309

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

20. Robertson Lain, Elisabeth. The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal.

Degree: Image, Oceanography, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/27856

► There is increasing interdisciplinary interest in phytoplankton community dynamics as the growing environmental problems of water quality (particularly eutrophication) and climate change demand attention. This… (more)

▼ There is increasing interdisciplinary interest in phytoplankton community dynamics as the growing environmental problems of water quality (particularly eutrophication) and climate change demand attention. This has led to a pressing need for improved biophysical and causal understanding of Phytoplankton Functional Type (PFT) optical signals, in order that satellite radiometry may be used to detect ecologically relevant phytoplankton assemblage changes. This understanding can best be achieved with biophysically and biogeochemically consistent phytoplankton Inherent Optical Property (IOP) models, as it is only via modelling that phytoplankton assemblage characteristics can be examined systematically in relation to the bulk optical water-leaving signal. Harmful Algal Bloom (HAB) conditions in the Southern Benguela and various inland waters of Southern Africa require continuous observation by satellite due to the potential for significant negative environmental impacts. Current oceanic bio-optical models do not perform well in elevated Chlorophyll a conditions, but the high biomass conditions of Southern African inland and coastal waters lend themselves extremely well to the development of phytoplankton IOP models as the water-leaving signal is overwhelmingly phytoplankton-dominated. An initial validation of a new model of Equivalent Algal Populations (EAP) is presented here, and comparison is made with two prominent phytoplankton IOP models. The EAP model places emphasis on explicit biophysical modelling of the phytoplankton population as a holistic determinant of IOPs. By necessity due to its origins in highly scattering waters, a distinctive attribute of the EAP model is its comprehensive handling of the spectral and angular character of phytoplankton scattering. This emphasis is shown to have an impact on the ability to retrieve the detailed phytoplankton spectral scattering information necessary for PFT applications and to successfully simulate waterleaving reflectance across wide ranges of physical environments, biomass, and assemblage characteristics. The accurate description of a water body's Volume Scattering Function (VSF), and hence its phase functions, is critical to the determination of the constituent IOPs, the associated spectral water-leaving reflectance, and consequently the retrieval of PFT information. The EAP model offers the ability to provide phytoplankton population-specific phase functions, unveiling an opportunity to gain further insight into the causality of the PFT signal. This is a new modelling capability, and its application in case studies and sensitivity analyses has resulted in improved understanding of the PFT/assemblage-related signal, in particular the discovery that phytoplankton spectral scattering is the primary driver of the PFT-related signal. The required thresholds of PFT detection with respect to biomass, IOP budget and assemblage effective diameter are quantified. Key findings are that the backscattering-driven signal in the 520 to 600 nm region is the critical PFT identifier… Advisors/Committee Members: Reason, Christopher (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Robertson Lain, E. (2018). The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/27856

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Robertson Lain, Elisabeth. “The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal.” 2018. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/27856.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Robertson Lain, Elisabeth. “The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal.” 2018. Web. 04 Mar 2021.

Vancouver:

Robertson Lain E. The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal. [Internet] [Thesis]. University of Cape Town; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/27856.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Robertson Lain E. The fundamental role of spectral scattering in the ocean colour Phytoplankton Functional Type signal. [Thesis]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/27856

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

21. Cossa, Obadias J. Modelling the oceanic circulation in the Delagoa Bight.

Degree: Image, Oceanography, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/27911

► The ROMS is used to investigate the oceanic circulation in the Delagoa Bight region, near the southwestern end of the Mozambique Channel. The model is… (more)

▼ The ROMS is used to investigate the oceanic circulation in the Delagoa Bight region, near the southwestern end of the Mozambique Channel. The model is initially configured at a horizontal resolution of 1/10° (9.9km) over the domain 30.1-43°E,22.13-30.8° S. Subsequent configurations nested an inner grid of resolution 1/30° (3.3km) over the region 32.43-36.43°E,24.09-27.71°S Several sensitivity experiments were performed with and without the inner grid or with or without tidal forcing. Using only the outer coarse resolution grid, the first experiment (DELAGI) does not include tidal forcing whereas tides are included in the second (DELAG-II) experiment. DELAG-III and DELAG-IV both use the inner higher resolution grid but exclude and include tidal forcing respectively. The model was evaluated against observations, namely the WOA, Pathfinder SST and AVISO SSH. The results showed that ROMS adequately resolves the oceanic features in the region, namely the pathways of the anticyclonic eddies from the northern Mozambique Channel and from Madagascar, and the instances when the DBLE is present or absent. The model is also able to reproduce the main water masses and their sources in the region. Water masses found in the centre of the Bight enter through the northeastern sector, either by intrusion of pulses or instabilities of the southwards flowing current. When the DBLE is well established, upwelling is likely to contribute to the water masses in the lower layers. The transport of water towards the Bight from the east was found to be less than that from the north. The model also succeeds in representing the thermocline structure of the DBLE but it fails to capture the local salinity maximum. When tidal forcing is included, the speed of the flow close to the coast increases. The model also revealed the influence of the Inhambane Cyclone on the Delagoa Bight as well as on the region to its south. This cyclone, which is generated in the flow near Inhambane, is similar to Natal Pulses which occur in the Agulhas Current. An eddy detecting and tracking system was used with both the model outputs and VISO SSH to determine the statistics of the DBLE, namely its dimensions, amplitudes and life-times. A maximum radius of 59.52 km, life span of 126 days and an amplitude of 27.27 cm were found. It was also demonstrated that this feature is generated northeast of the Bight. When the inner grid was included in the simulations, anticyclonic features were generated within the Bight with a maximum diameter of 85.4 km and life span of 12 day. These anticyclonic features dominate the circulation when the DBLE is absent (less than 30 percent of the total period of the simulation). The possibility of several cyclonic cores existing simultaneously in the Bight was also demonstrated. Two cores were found with life spans of more than 12 days. When the number of cores is greater than two, they tend to be short lived. Analysis of energy conversion rates showed that the generation of both the DBLE and the Inhambane cyclones is mainly by barotropic… Advisors/Committee Members: Reason, Chris (advisor), Pous, Stéphane (advisor), Penven, Pierrick (advisor).

Subjects/Keywords: Oceanography

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cossa, O. J. (2018). Modelling the oceanic circulation in the Delagoa Bight. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/27911

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Cossa, Obadias J. “Modelling the oceanic circulation in the Delagoa Bight.” 2018. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/27911.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Cossa, Obadias J. “Modelling the oceanic circulation in the Delagoa Bight.” 2018. Web. 04 Mar 2021.

Vancouver:

Cossa OJ. Modelling the oceanic circulation in the Delagoa Bight. [Internet] [Thesis]. University of Cape Town; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/27911.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Cossa OJ. Modelling the oceanic circulation in the Delagoa Bight. [Thesis]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/27911

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

22. Mawren, Daneeja. Upper ocean variability and tropical cyclones in the South West Indian Ocean.

Degree: PhD, Oceanography, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/29219

► Tropical cyclones (TCs) are the most devastating weather phenomenon in nature with the powerful storm surge events occurring when severe and large TCs make landfall… (more)

▼ Tropical cyclones (TCs) are the most devastating weather phenomenon in nature with the powerful storm surge events occurring when severe and large TCs make landfall along coastlines. Although there have been significant strides in the TC track forecasts over the last 30 years, skills in TC intensity prediction still lag behind. Intensity may be impacted by the mixing length temperature (known as Tdy) and barrier layer thickness (BLT). Similar to cyclones in other tropical ocean basins, tropical cyclones in the South West Indian Ocean also cause significant social and economic damage in southeastern Africa and Madagascar. To forecast TC intensity more accurately, monitoring upper ocean conditions in the South Indian Ocean is of top priority. Two areas in the relatively poorly studied South Indian Ocean where such upper ocean characteristics of relevance to tropical cyclones need to be better understood are the Seychelles Chagos Thermocline Ridge (SCTR) and the Mozambique Channel. In the first part of the study, the variability of Tdy and BLT in the South West Indian Ocean, focused on the SCTR region and their relationships with tropical cyclones are investigated. It is shown that rapid cyclone intensification is influenced by large Tdy values, thick barrier layers and the presence of anticyclonic eddies. Both BLT and Tdy fields are modulated by the westward propagation of Rossby waves, which are often associated with ENSO. For example, the 1997-1998 El Nino shows a strong signal in Tdy, SST and BLT over the South West Indian Ocean. After this event, an increasing trend in Tdy occurred over most of the basin which may be associated with changes in atmospheric circulation. A rise in SST, Power Dissipation Index and frequency of Category-5 tropical cyclones also occurred post-1998. A case study of TC Bansi in the South West Indian Ocean and its relation to upper ocean heat content was presented. This tropical cyclone is of interest due to its unusual track and also because of all the damage it caused. Anomalously deep thermocline and high Tdy values were observed around December 2014-January 2015 in the South West Indian Ocean and analysis of the upper ocean structure during Bansi showed that its rapid intensification to Category 4 was related to its passage over a high Tdy (warm core) eddy region and a deep barrier layer. The second area focussed on, the Mozambique Channel, is not only a region of relatively high TC activity with highly vulnerable coastal populations, but also very energetic in terms of mesoscale ocean eddies and tidal forcing. Changes in upper ocean characteristics in the Mozambique Channel due to tidal forcing are examined as they may have significant impacts on the upper ocean structure and thus influence tropical cyclones which often occur in this region. Two experiments were conducted using the Regional Ocean Modelling System (ROMS); one forced with tides (Tide) and the other experiment without tidal forcing (NoTide). On seasonal time scales, the tidal forcing simulation shows warmer temperatures… Advisors/Committee Members: Reason, Christopher (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mawren, D. (2018). Upper ocean variability and tropical cyclones in the South West Indian Ocean. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/29219

Chicago Manual of Style (16^th Edition):

Mawren, Daneeja. “Upper ocean variability and tropical cyclones in the South West Indian Ocean.” 2018. Doctoral Dissertation, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/29219.

MLA Handbook (7^th Edition):

Mawren, Daneeja. “Upper ocean variability and tropical cyclones in the South West Indian Ocean.” 2018. Web. 04 Mar 2021.

Vancouver:

Mawren D. Upper ocean variability and tropical cyclones in the South West Indian Ocean. [Internet] [Doctoral dissertation]. University of Cape Town; 2018. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/29219.

Council of Science Editors:

Mawren D. Upper ocean variability and tropical cyclones in the South West Indian Ocean. [Doctoral Dissertation]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/29219

University of Cape Town

23. Halo, Issufo F M. The Mozambique Channel eddies : characteristics and mechanisms of formation.

Degree: Image, Oceanography, 2012, University of Cape Town

URL: http://hdl.handle.net/11427/6477

► The model outputs and the satellite data have shown a number of cyclonic and anticyclonic eddies being generated within the Mozambique Channel. The eddies were… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Halo, I. F. M. (2012). The Mozambique Channel eddies : characteristics and mechanisms of formation. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/6477

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Halo, Issufo F M. “The Mozambique Channel eddies : characteristics and mechanisms of formation.” 2012. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/6477.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Halo, Issufo F M. “The Mozambique Channel eddies : characteristics and mechanisms of formation.” 2012. Web. 04 Mar 2021.

Vancouver:

Halo IFM. The Mozambique Channel eddies : characteristics and mechanisms of formation. [Internet] [Thesis]. University of Cape Town; 2012. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/6477.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Halo IFM. The Mozambique Channel eddies : characteristics and mechanisms of formation. [Thesis]. University of Cape Town; 2012. Available from: http://hdl.handle.net/11427/6477

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

College of William and Mary

24. Fall, Kelsey. Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation.

Degree: PhD, Virginia Institute of Marine Science, 2020, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1593091656

► Understanding the nature of suspended particles is crucial to explaining water clarity issues in many estuaries, including the Chesapeake Bay and its tidal tributaries. Typical… (more)

▼ Understanding the nature of suspended particles is crucial to explaining water clarity issues in many estuaries, including the Chesapeake Bay and its tidal tributaries. Typical near surface estuarine particles are not individual sediment grains, but rather are clusters of inorganic and organic components known as flocs. Because of their fragile nature, flocs are challenging to observe in-situ, so their influence on the optical properties of the system are not well-known. This dissertation used a combination of state-of-the-art optical instrumentation, including laser scattering and transmissometry, a high-definition particle imaging camera system (PICS), and irradiance meters, along with supporting laboratory analysis techniques to investigate the surface waters of the York River estuary. This work characterized estuarine floc properties while simultaneously identifying relationships between estuarine light attenuation, absorption, and scattering due to flocs as well as other water column constituents. The relative organic fraction of suspended solids was found to be an important control on the fractal nature of estuarine flocs, including primary particle size and density, as well as bulk floc properties. A new approach is presented here that simultaneously solves for multiple floc fractal characteristics (e.g., fractal dimension, primary particle size, and primary particle density) and identifies whether simple fractal models are appropriate to describe individual suspensions. Results indicate that suspensions in the York River estuary with lower organic fraction and higher total suspended solids (TSS) are dominated by larger flocs composed of smaller, denser primary particles. In contrast, suspensions with higher organic fraction and lower TSS are composed of smaller flocs with larger, less dense primary particles. Paradoxically, the organic-rich flocs containing larger, lower density primary particles are, in terms of solids content, actually denser overall. This is because the larger, organic-rich primary particles take up more space within the flocs, leaving less room for water. Diffuse light attenuation, scattering, and absorption were related to the nature of the flocs in the York estuary, as well as to other water column constituents. It was found that as TSS increases, larger, lower density flocs containing less organic matter and more water increasingly dominate. This causes scattering to increase more quickly than TSS. In contrast, absorption increased more slowly than TSS. This is because the organics more prevalent at low TSS absorb more light per mass than the inorganic solids that dominate suspensions with higher TSS. Under most conditions, total scattering was dominated by inorganic particles. However, the combined effects of other components (the water itself, colored dissolved organic matter, phytoplankton, plus non-algal organic solids) typically dominated both absorption and attenuation. The importance of phytoplankton and organic solids relative to inorganic solids from land runoff have important…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Fall, K. (2020). Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1593091656

Chicago Manual of Style (16^th Edition):

Fall, Kelsey. “Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation.” 2020. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1593091656.

MLA Handbook (7^th Edition):

Fall, Kelsey. “Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation.” 2020. Web. 04 Mar 2021.

Vancouver:

Fall K. Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation. [Internet] [Doctoral dissertation]. College of William and Mary; 2020. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1593091656.

Council of Science Editors:

Fall K. Influence Of Suspended Particle Size And Composition On Particle Image Processing, Estuarine Floc Fractal Properties, And Resulting Estuarine Light Attenuation. [Doctoral Dissertation]. College of William and Mary; 2020. Available from: https://scholarworks.wm.edu/etd/1593091656

College of William and Mary

25. Tarpley, Danielle. Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations.

Degree: PhD, Virginia Institute of Marine Science, 2020, College of William and Mary

URL: https://scholarworks.wm.edu/etd/1593091925

► Fine-grained material such as silts and clays are the predominant sediment type in low energy systems such as micro-tidal embayments and estuaries. Due to its… (more)

▼ Fine-grained material such as silts and clays are the predominant sediment type in low energy systems such as micro-tidal embayments and estuaries. Due to its cohesive nature, fine sediment typically moves through marine systems as aggregated particles, or flocs, rather than as individual mineral grains. The particle's components, local hydrodynamics, and concentration influence floc size, density, and fall velocity. These, in turn, impact suspended sediment transport, which complicates predictions of the fate of sediment for water quality, contaminant distribution, and dredging purposes in these systems. This dissertation used a state-of-the-art modeling system and observations to examine the variability in sediment distribution due to cohesive processes along a partially mixed estuary and to determine the role of flocculation on sediment transport for a muddy site within the York River estuary, Virginia. The Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system was used to simulate the hydrodynamics and suspended sediment transport in a muddy estuarine system. The model accounted for flocculation dynamics with a population balance model, FLOCMOD, changes in the erosion of sediment from the bed due to compaction or bed consolidation, and sediment-induced density gradients. The sensitivity of the sediment distribution was performed using an idealized two-dimensional (vertical and longitudinal) model that produced key estuarine features such as salinity-driven circulation and an estuarine turbidity maximum (ETM). The reference model included the effects of flocculation, bed consolidation, and sediment-induced density gradients. Results from the reference model were compared to test cases, each of which removed one of these processes. This showed that the effects of flocculation on suspended sediment concentrations (SSC) were most significant in the surface waters and in the ETM; whereas bed consolidation decreased SSC along the full length of the estuary. Another test case demonstrated that calculations of SSC and median floc diameter (D50) were sensitive to the number of sediment classes used to represent the floc population. The capabilities of the idealized two-dimensional estuary were extended and used to examine the contribution of flocculation compared to other sediment transport mechanisms such as advection, diffusion, settling, and erosion. The dominant processes that impacted the sediment mass balance in the idealized estuary were flocculation, vertical diffusion, and erosion. Next, the D50 produced by FLOCMOD in the idealized estuary was compared to a theoretical equilibrium floc size (Deq) estimated based on the ratio of SSC to the square root of the shear rate (G). This analysis also produced an estimate for a timescale for flocculation. In general, D50 reached Deq in the bottom boundary of the estuary when the flocculation timescales were on the order of minutes. However, immediately above the sediment bed, Deq was very similar to D50 when erosion was minimal or when finer flocs were…

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Tarpley, D. (2020). Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations. (Doctoral Dissertation). College of William and Mary. Retrieved from https://scholarworks.wm.edu/etd/1593091925

Chicago Manual of Style (16^th Edition):

Tarpley, Danielle. “Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations.” 2020. Doctoral Dissertation, College of William and Mary. Accessed March 04, 2021. https://scholarworks.wm.edu/etd/1593091925.

MLA Handbook (7^th Edition):

Tarpley, Danielle. “Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations.” 2020. Web. 04 Mar 2021.

Vancouver:

Tarpley D. Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations. [Internet] [Doctoral dissertation]. College of William and Mary; 2020. [cited 2021 Mar 04]. Available from: https://scholarworks.wm.edu/etd/1593091925.

Council of Science Editors:

Tarpley D. Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations. [Doctoral Dissertation]. College of William and Mary; 2020. Available from: https://scholarworks.wm.edu/etd/1593091925

University of Cape Town

26. Vianello, Patrick Angus. A qualitative and physical analysis of processes around the Mascarene plateau.

Degree: Image, Oceanography, 2015, University of Cape Town

URL: http://hdl.handle.net/11427/16940

► The Mascarene Plateau is a submerged volcanic plateau to the east of Madagascar which extends over 2200 km between the Seychelles and Mauritius. It is… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Vianello, P. A. (2015). A qualitative and physical analysis of processes around the Mascarene plateau. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/16940

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Vianello, Patrick Angus. “A qualitative and physical analysis of processes around the Mascarene plateau.” 2015. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/16940.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Vianello, Patrick Angus. “A qualitative and physical analysis of processes around the Mascarene plateau.” 2015. Web. 04 Mar 2021.

Vancouver:

Vianello PA. A qualitative and physical analysis of processes around the Mascarene plateau. [Internet] [Thesis]. University of Cape Town; 2015. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/16940.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Vianello PA. A qualitative and physical analysis of processes around the Mascarene plateau. [Thesis]. University of Cape Town; 2015. Available from: http://hdl.handle.net/11427/16940

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

27. Gregor, Luke. Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean.

Degree: Image, Oceanography, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/25320

► The Southern Ocean plays an important role in mitigating the effects of anthropogenically driven climate change. The region accounts for 43% of oceanic uptake of… (more)

▼ The Southern Ocean plays an important role in mitigating the effects of anthropogenically driven climate change. The region accounts for 43% of oceanic uptake of anthropogenic carbon dioxide (CO₂). This is foreseen to change with increasing greenhouse gas emissions due to ocean chemistry and climate feedbacks that regulate the carbon cycle in the Southern Ocean. Studies have already shown that Southern Ocean CO₂ is subject to interannual variability. Measuring and understanding this change has been difficult due to sparse observational data that is biased toward summer. This leaves a crucial gap in our understanding of the Southern Ocean CO₂ seasonal cycle, which needs to be resolved to adequately monitor change and gain insight into the drivers of interannual variability. Machine learning has been successful in estimating CO₂ in may parts of the ocean by extrapolating existing data with satellite measurements of proxy variables of CO₂. However, in the Southern Ocean machine learning has proven less successful. Large differences between machine learning estimates stem from the paucity of data and complexity of the mechanisms that drive CO₂. In this study the aim is to reduce the uncertainty of estimates, advance our understanding of the interannual drivers, and optimise sampling of CO₂ in the Southern Ocean. Improving the estimates of CO₂ was achieved by investigating: the impact of increasing the gridding resolution of input data and proxy variables, and Support vector regression (SVR) and Random Forest Regression (RFR) as alternate machine learning methods. It was found that the improvement gained by increasing gridding resolution was minimal and only RFR was able to improve on existing error estimates. Yet, there was good agreement of the seasonal cycle and interannual trends between RFR, SVR and estimates from the literature. The ensemble mean of these methods was used to investigate the variability and interannual trends of CO₂ in the Southern Ocean. The interannual trends of the ensemble confirmed trends reported in the literature. A weakening of the sink in the early 2000's, followed by a strengthening a strengthening of the sink into the early 2010's. Wind was the overall driver of dominant decadal interannual trends, being more important during winter due to the increased efficacy of entrainment processes. Summer interannual variability of CO₂ was driven primarily by chlorophyll, which responded to basin scale changes in drivers by the complex interaction with underlying physics and possibly sub-mesoscale processes. Lastly CO₂ sampling platforms, namely ships, profiling floats and moorings, were tested in an idealised simulated model environment using a machine learning approach. Ships, simulated from existing cruise tracks, failed to adequately resolve CO₂ below the uncertainty threshold that is required to resolve the seasonal cycle of Southern Ocean CO₂. Eight high frequency sampling moorings narrowly outperformed 200 profiling floats, which were both able to adequately resolve the seasonal cycle. Though,… Advisors/Committee Members: Monteiro, Pedro M S (advisor), Vichi, Marcello (advisor), Kok, Schalk (advisor).

Subjects/Keywords: Oceanography

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gregor, L. (2017). Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/25320

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Gregor, Luke. “Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean.” 2017. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/25320.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Gregor, Luke. “Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean.” 2017. Web. 04 Mar 2021.

Vancouver:

Gregor L. Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/25320.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Gregor L. Improved estimates and understanding of interannual trends of CO₂ fluxes in the Southern Ocean. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/25320

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

28. Rouault, Marjolaine. Agulhas current variability determined from space : a multi-sensor approach.

Degree: Image, Oceanography, 2011, University of Cape Town

URL: http://hdl.handle.net/11427/8500

► Satellite remote sensing datasets including more than 6 years of high frequency Sea Surface Temperature (SST) imagery as well as surface current observations derived from… (more)

▼ Satellite remote sensing datasets including more than 6 years of high frequency Sea Surface Temperature (SST) imagery as well as surface current observations derived from 18 years of merged-altimetry and over 2 years of Advanced Synthetic Aperture Radar (ASAR) observations are combined to study the variability of the Agulhas Current. The newly available rangedirected surface currents velocities from ASAR, which rely on the careful analysis of the measured Doppler shift, show strong promise for monitoring the meso to sub-mesoscale features of the surface circulation. While the accuracy of ASAR surface current velocities suffers from occasional bias due to our current inability to systematically account for the wind-induced contribution to the Doppler shift signal, the ASAR surface current velocities are able to consistently highlight regions of strong current and shear. The synaptic nature and relatively high resolution of ASAR acquisitions make the ASAR derived current velocities a good complement to altimetry for the study of sub-mesoscale processes and western boundary current dynamics. Time-averaged range-directed surface currents derived from ASAR provide an improved map of the mean Agulhas Current flow, clearly showing the location of the Agulhas Current core over the 1000 m isobath and identifying the region at the shelf edge of the north-eastern Agulhas Bank as one of the most variable within the Agulhas Current. To determine the variability of the Agulhas Current, an algorithm to track the position of the current is developed and applied to the longer merged-altimetry and SST records. Limitations associated with altimetry near the coast favour the use of the SST dataset to track the position of the Agulhas Current in its northern region. In the southern Agulhas, where the current lies further from the coast, altimetry is suited to monitoring the position of the Agulhas Current. The front detection analysis conducted on the SST dataset in the northern Agulhas reveals the complex nature of Natal Pulses. The downstream passage of the Natal Pulses is associated with the generation of secondary offshore meanders at the inshore edge of the current. Perturbations formed during the passage of Natal Pulses evolve rapidly to either dissipate, re-merge with the initial Natal Pulse or in some rare occasion, detach from the Agulhas Current. Advisors/Committee Members: Shillington, Frank (advisor).

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Rouault, M. (2011). Agulhas current variability determined from space : a multi-sensor approach. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/8500

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Rouault, Marjolaine. “Agulhas current variability determined from space : a multi-sensor approach.” 2011. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/8500.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Rouault, Marjolaine. “Agulhas current variability determined from space : a multi-sensor approach.” 2011. Web. 04 Mar 2021.

Vancouver:

Rouault M. Agulhas current variability determined from space : a multi-sensor approach. [Internet] [Thesis]. University of Cape Town; 2011. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/8500.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Rouault M. Agulhas current variability determined from space : a multi-sensor approach. [Thesis]. University of Cape Town; 2011. Available from: http://hdl.handle.net/11427/8500

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

29. Collins, Charine. The dynamics and physical processes of the Comoros Basin.

Degree: Image, Oceanography, 2013, University of Cape Town

URL: http://hdl.handle.net/11427/6467

► The main objective of this thesis was to investigate the circulation in the ComorosBasin using observed and model datasets. These data were used to establish… (more)

Subjects/Keywords: Oceanography

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Collins, C. (2013). The dynamics and physical processes of the Comoros Basin. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/6467

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Collins, Charine. “The dynamics and physical processes of the Comoros Basin.” 2013. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/6467.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Collins, Charine. “The dynamics and physical processes of the Comoros Basin.” 2013. Web. 04 Mar 2021.

Vancouver:

Collins C. The dynamics and physical processes of the Comoros Basin. [Internet] [Thesis]. University of Cape Town; 2013. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/6467.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Collins C. The dynamics and physical processes of the Comoros Basin. [Thesis]. University of Cape Town; 2013. Available from: http://hdl.handle.net/11427/6467

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

30. Atkins, Josephine ffion. Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela.

Degree: Image, Oceanography, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/25208

► Phytoplankton are a key component in the functioning of marine ecosystems and play a central role in the cycling of nitrogen and other elements. Metrics… (more)

▼ Phytoplankton are a key component in the functioning of marine ecosystems and play a central role in the cycling of nitrogen and other elements. Metrics that can adequately represent the biogeochemical processes associated with phytoplankton diversity are needed in order to make use of remote sensing and modeling platforms. A single-value size proxy, effective diameter (Deff ), represents the mean volume to surface area ratio across the nano and micro plankton size fraction (2-200µm) in the southern Benguela, but has yet to be tested regarding its biogeochemical relevance. Cell size imposes overarching constraints on phytoplankton metabolism; there are therefore strong grounds for evaluating the usefulness of the metric (Deff ) in studies of nitrogen dynamics in diverse, natural assemblages. Three case studies were used to explore the nitrogen dynamics in naturally occurring assemblages and to evaluate the relationships between Deff and the uptake of the different sources of nitrogen. Two of the case studies comprised high biomass, harmful algal blooms observed off Lamberts Bay during an upwelling/downwelling cycle. The third case study used bi-monthly sampling over a full year in Saldanha Bay. The Lamberts Bay case studies involved blooms occasionally dominated by HAB-forming species: a mixotrophic ciliate, Myrionecta rubra, and a dinoflagellate, Prorocentrum triestinum. The nitrogen uptake rates followed the well observed pattern of high nitrate uptake by large cells and regenerated nitrogen uptake by small cells. Myrionecta rubra had a wide range of nitrate (O₃⁻ ) uptake rates (0.02-0.3 µmol N L⁻¹ h⁻¹). Prorocentrum triestinum showed slower rates of O₃⁻ uptake (0.01-0.2 µmol N L⁻¹ h⁻¹) and dominated in low O₃⁻ , stratified conditions. Diatoms were the most efficient utilisers of O₃⁻ and total nitrogen in these cases. The effective diameter was significantly related to the uptake rates of ammonium (NH₄⁺ ) (r=-0.54, p<0.005) and urea (r=-0.59, p<0.005), but not O₃⁻ (r=0.27, p=0.11). This was attributed to some instances of bi-modality in observed size distributions as well as potentially specialist nutrient uptake strategies employed by diatoms. The year-round data from Saldanha Bay indicated the system was diatom-dominated and was used to assess 1 how well Deff could represent the nitrogen uptake strategies employed by the diverse diatom assemblages. The Saldanha Bay system has O₃⁻ limited surface waters during summer, and light-limited bottom waters during winter. No significant relationship was found between Deff and the mass-specific uptake rates of the different nitrogen species in this data set. This was attributed to the complex shapes of the size distributions and the comparatively low biomass observed. Uptake kinetic experiments revealed high variability for maximum uptake rates (Vmax) and half saturation values (Ks) for both O₃⁻ and NH₄⁺ . For O₃⁻ : Vmax ranged 0.007-0.17 µmol N L⁻¹ h⁻¹, and Ks ranged between 0.2-42.5 µmol N L⁻¹. For NH₄⁺ Vmax was observed between 0.02-2.7 µmol N L⁻¹ h⁻¹; and Ks values… Advisors/Committee Members: Moloney, Coleen L (advisor), Bernard, Stewart (advisor), Machu, Eric (advisor).

Subjects/Keywords: Oceanography

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Atkins, J. f. (2017). Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/25208

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Atkins, Josephine ffion. “Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela.” 2017. Thesis, University of Cape Town. Accessed March 04, 2021. http://hdl.handle.net/11427/25208.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Atkins, Josephine ffion. “Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela.” 2017. Web. 04 Mar 2021.

Vancouver:

Atkins Jf. Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 04]. Available from: http://hdl.handle.net/11427/25208.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Atkins Jf. Using cell size to represent phytoplankton diversity in studies of nitrogen dynamics in the southern Benguela. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/25208

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Open Access Theses and Dissertations