Dissertations / Theses: 'Oceanography'

1

Buffett, Grant George. "Seismic Oceanography: A New Tool to Characterize Physical Oceanographic Structures and Processes." Doctoral thesis, Universitat de Barcelona, 2011. http://hdl.handle.net/10803/1939.

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Large scale global oceanic circulation redistributes heat and freshwater and therefore affects global climate. One of its main forcing mechanisms is, in addition to surface heat and freshwater fluxes, the diapycnal (across lines of equal density) mixing in the ocean interior. The energy needed to drive the mixing processes is mainly provided by tides and wind [Wunsch, 2002]. It is transformed into internal wave energy, cascading through a range of smaller scales leading finally into turbulence and molecular dissipation. Water masses in the ocean are stratified and often separated by relatively thin layers with strong gradients in temperature and/or salinity across which heat and mass transfer occur in order to maintain global circulation and stratification. However, these processes are difficult to observe in practice. Below a few meters, the ocean is opaque to light, and thus to direct optical observations of deep processes [Thorpe, 2005]. Therefore, the development of scientific methodologies and instruments to directly or indirectly measure processes in the ocean interior are of high importance to understanding those processes and their implications.

The motivation behind this research is two-tier: 1) broadly, and academically, it is the scientific curiosity of understanding the ocean in order to better comprehend its role in the context of Earth systems; 2) expressly, the motivation is to develop the methodological toolset necessary to observe the ocean on a spatial and temporal scale not possible with traditional oceanographic techniques, thus allowing the foundation of more accurate models of ocean circulation and thereby, ocean-climate interactions.

The toolset is emerging as a robust technique of physical oceanography known as 'seismic oceanography'. By definition, seismic oceanography is the application of multichannel seismic (MCS) reflection profiling to physical oceanography. This definition, however, could be subject to future revision and refinement because the development of seismic oceanography observational tools will inevitably lead to newer perspectives.

The Mediterranean Outflow Water (henceforth, MOW) is a natural laboratory for seismic oceanography. The MOW was chosen to test seismic reflection in oceanography for three main reasons: 1) The strong oceanographic signature of the MOW. Due to the penetration of the MOW into the North Atlantic through the Strait of Gibraltar, strong characteristic contrasts in temperature (1.5 °C) and salinity (0.3 psu) and thus, density (0.4 kg/m3) are observed between the MOW and the surrounding Atlantic waters [Baringer and Price, 1997]. These contrasts in density (along with sound speed) are the contributing factors to reflection coefficient, making the identification of structures and processes possible. 2) The large variety of oceanographic and topographic features, such as a continental slope, undulating seafloor (including seamounts and basins) and mesoscale Mediterranean salt lenses (meddies). These structures and processes are believed to play an important role in maintaining the temperature and salinity distribution in the north Atlantic [Bower et. al., 1997]. 3) Finally, extensive archived data sets of bothoceanographic and seismic data place interpretive constraints on the data collected.

Part I of this thesis consists of two peer-reviewed papers published by the author and coauthors (Chapters 1 and 2), one manuscript submitted for publication (Chapter 3) and two published peer-reviewed research letters that the author played a lesser role developing (Chapter 4). Part II of the thesis addresses the seismological (Chapter 5) and oceanographic backgrounds (Chapter 6) in the context of some of the structures and processes that are amenable to seismic ensonification. Part III consists of general discussions and conclusions (Chapter 7) and potential future research and development (Chapter 8).
La motivació que hi ha al darrera d'aquest treball es pot separar en dos nivells: 1) En termes generals, i acadèmicament, és la curiositat purament científica d'estudiar l'oceà per tal de comprendre millor el seu paper en el context de les Ciències de la Terra; 2) Concretament, la motivació és desenvolupar les eines necessàries per a observar l'oceà a una escala espaial i temporal que no és possible amb les tècniques tradicionals oceanogràfiques, permetent així generar models més precisos de circulació oceànica i, per tant, de les interaccions oceà-clima.

L'objectiu a curt i mitjà termini d'aquesta tesi és el desenvolupament de noves eines d'oceanografia física que proporcionin noves perspectives sobre la dinàmica oceànica. Aquest conjunt d'eines està emergint com una metodologia sòlida dins de l'oceanografia física coneguda com 'oceanografia sísmica'. Per definició, l'oceanografia sísmica és l'aplicació de la sísmica de reflexió multicanal (MCS) a l'oceanografia física. Aquesta definició, però, podria estar subjecte a una futura revisió i perfeccionament, ja que el desenvolupament d'eines d'oceanografia sísmica inevitablement donarà lloc a noves perspectives.

La part principal d'aquesta tesi la constitueixen quatre articles, publicats per l'autor i co-autors al llarg del seu període d'investigació (capítols 1, 2 i 4); així com un article sotmès (Capítol 3). En la segona part, com a suport per als lectors no familiaritzats, s'aborden els antecedents sismològics (Capítol 5) i oceanogràfics (Capítol 6) en el context d'algunes de les estructures i processos que són susceptibles de ser identificats mitjançant la sísmica. Les conclusions generals es presenten en el Capítol 7 i en el Capítol 8 es donen algunes recomanacions per a futures investigacions i desenvolupaments (Part III). La tesi es complementa amb quatre apèndixs, on a banda d'un ampli resum en català (Apèndix I), hi ha els diagrames de flux utilitzats per l'autor en el processament de les dades sísmiques (Apèndix II), un conjunt de set desplegables de les seccions sísmiques en gran format (Apèndix III) i finalment un glossari de termes útils per ajudar als lectors no iniciats en qualsevol de les branques de la sismologia o l'oceanografia (Apèndix IV).

2

McGregor, J. A. "HF radar oceanography." Thesis, University of Canterbury. Physics, 1985. http://hdl.handle.net/10092/7578.

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The development of a 26MHz pulsed Doppler radar system for remote sensing of ocean surface conditions is described. This radar obtains Doppler spectra of echoes from ocean waves within the range 10-40 km from the shore. From these Doppler spectra it is possible to estimate oceanographic parameters such as sea state, wind speed, wind direction, radial components of current velocities and properties of swell. The work concentrates on the radar design principles and includes a detailed study of the effect of ground wave propagation conditions on the performance of radar systems of this type. Results obtained with the radar are discussed from the points of view of both the performance of the system and the oceanographic information contained in the Doppler spectra.

3

Veilleux, Lorraine. "Physical oceanography of northern estuaries." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59830.

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Within the context of oceanographic research on northern estuaries in James Bay and Hudson Bay, and in relation with hydroelectric developments and their impact on the physical environment, two studies were undertaken. Both concern the importance of bottom topography, tidal motion and fresh water input on the estuarine processes in these areas.
The first one, in Rupert Bay (south-eastern corner of James Bay), describes tidal and local wind effects on circulation and mixing patterns for summer conditions. An estimate of terms in the lateral momentum equation shows that the centrifugal acceleration, the Coriolis force and the baroclinic pressure gradient are the most important forces at a mid-bay cross section transect.
The second study is concerned with the freshwater plume of Great Whale River (south-eastern Hudson Bay). CTD measurements were used to examine the lift-off point of the plume for under-ice and increasing discharge conditions. Comparison with existing models shows them to be inappropriate for under-ice conditions. Finally, the presence of supercooled water masses in the region of the study is reported.

4

Leathers, Robert A. "Inverse solution methods for optical oceanography /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/7066.

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5

Middleditch, Andrew. "Spectral analysis in high frequency radar oceanography." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/3590/.

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High Frequency radar systems provide a unique opportunity to measure evolving littoral oceanic dynamics at high temporal and spatial resolution. Backscattered electromagnetic signals from ocean waves are modulated by Bragg resonant scattering. A perturbation analysis yields an expression for the spectral content of radar signals which can be exploited to provide estimates of oceanographic parameters: the radial component of surface current can be extracted from the frequency locations of the first order peaks; the ocean wave directional spectrum is related to the second order continuum via a non-linear integral equation. The periodogram, based on a Fourier decomposition of radax data, is the standard method used to derive frequency spectra. Limitations in this approach, caused by inhomogeneities in the underlying ocean field, are investigated. An instantaneous frequency technique is proposed in this thesis which mitigates the spectral distortion by demodulating the backscattered radax signals -a filtering procedure is developed which measures the temporally varying Bragg components. Alternative spectral techniques are analysed in order to validate the filter: an autoregressive paxa, metric modelling approach and an eigendecomposition method. The filter is evaluated, using radar and in situ data, which establishes its potential for ocean remote sensing. Significant improvements in the quantity and accuracy of wave measurements are demonstrated. Properties and constraints of the filter are derived using simulated data. Finally, the generic structure of the extracted instantaneous frequency signals is investigated and related to oceanographic processes.

6

Berry, P. J. "Applications of satellite altimetry to dynamical oceanography." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46961.

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Sheen, Katy Louise. "Seismic oceanography : imaging the antarctic circumpolar current." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609132.

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Coleman, Dwight F. "Archaeological oceanography of inundated coastal prehistoric sites /." View online ; access limited to URI, 2003. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3115624.

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Zarroug, Moundheur. "Asymptotic methods applied to some oceanography-related problems." Doctoral thesis, Stockholm : Department of Meteorology, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-37763.

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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

10

Nerger, Lars. "Parallel filter algorithms for data assimilation in oceanography." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=975524844.

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Koonprasert, Sanoe. "The Sinc-Galerkin Method for Problems in Oceanography." Thesis, Montana State University, 2003. http://etd.lib.Montana.edu/etd/2003/koonprasert/KoonprasertS_03.pdf.

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The model for a wind-driven current with depth-dependent eddy viscosity is developed as a complex velocity formulation and a coupled system formulation. The numerical solutions, calculated by a Sinc-Galerkin method, are compared. A fully Sinc-Galerkin method in both space and time for a partial differential equation with time-dependent boundary conditions is developed. This entirely new technique is applied to the model for a wind-driven current with time-dependent viscosity. Several numerical examples are used to test the performance of the method. This fully Sinc-Galerkin method is then applied to the spin-up and the episodic wind stress oceanography problems.

12

Hinsley, Westley Richard. "Planktonica : a system for doing biological oceanography by computer." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418316.

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Foster, Deborah Anne. "New applications of Â²Â²â¶Ra to oceanography." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409791.

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Domingues, Carla Sofia Portela. "Population genetics of C. Maenas : oceanography and larval dispersal." Doctoral thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/973.

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Doutoramento em Biologia
Decifrar a complexa interacção entre os ciclos de vida de espécies marinhas e a oceanografia revela-se fundamental para a compreensão do fluxo genético e da conectividade no meio marinho. Nas espécies marinhas com desenvolvimento indirecto o fluxo de genes entre populações depende da distância que separa as populações, bem como da interacção entre a duração do desenvolvimento larvar, do comportamento das larvas e dos padrões de circulação oceânica. A conectividade larvar influencia uma variedade de processos como a dinâmica de stocks e de populações, a distribuição e limites geográficos das espécies, a estrutura genética das populações e a dispersão de espécies invasivas e reveste-se consequentemente de uma importância fundamental na identificação das unidades populacionais evolucionariamente relevantes e para a gestão e conservação marinhas. Os marcadores genéticos e os Modelos Individuais Acoplados a Modelos Físico-Biológicos (“ICPBMs”) são actualmente ferramentas fundamentais para o estudo dos padrões de dispersão larvar e para avaliar o nível de conectividade populacional. A presente tese respeita à avaliação das escalas espaciais de conectividade de populações de uma espécie costeira, o caranguejo Carcinus maenas, e utiliza conjuntamente informação de marcadores genéticos, análise de séries temporais de fornecimento de larvas e um modelo numérico de circulação oceânica. O primeiro capítulo introduz a temática da conectividade em espécies marinhas e inclui algumas referências aos métodos moleculares, analíticos e de modelação seguidos ao longo da tese. Através da utilização de múltiplas ferramentas – avaliação da estrutura genética geográfica de C. maenas na sua distribuição nativa com recurso a marcadores de DNA (microssatélites) (Capítulo 2), avaliação da estrutura genética temporal das larvas que formam os eventos de fornecimento larvar à Ria de Aveiro, NW Portugal (Capítulo 3), descrição da variabilidade inter-anual do fornecimento larvar à Ria de Aveiro, NW Portugal (Capítulo 4) e validação de um modelo ICPBM que descreve os padrões observados de fornecimento (Capítulo 5) – esta tese espera poder contribuir para uma melhor compreensão dos mecanismos que regulam o fluxo de genes e a conectividade entre populações de organismos marinhos. No Capítulo 6 são apresentadas as principais conclusões da investigação. A análise genética com recurso a microssatélites indicou que as populações de C. maenas são geneticamente homogéneas ao longo de várias centenas de km, dentro da distribuição nativa da espécie. Paralelamente, não foram encontrados indícios da existência de reprodução por “sweepstakes” em C. maenas de populações da costa oeste da Península Ibérica, visto que não se obtiveram diferenças genéticas significativas entre os eventos larvares. Também não se encontrou qualquer estrutura familiar entre as larvas que formam cada episódio de fornecimento, e não houve nenhuma redução significativa da variabilidade genética das larvas quando comparada com a de caranguejos adultos. A análise de séries temporais de suprimento de larvas na Ria de Aveiro em cinco anos estudados indica que este é um fenómeno episódico e variável, sendo os maiores episódios de fornecimento coincidentes com as marés vivas e acentuados por fortes ventos de sul. O modelo ICPBM foi validado com sucesso e parece fornecer uma estimativa realística das escalas espaciais e temporais de dispersão larvar, de acordo com as observações da estrutura genética e da ausência de reprodução por “sweepstake” em C. maenas da costa oeste da Península Ibérica
Unravelling the interactions between life-history strategies and oceanographic processes is central to the understanding of gene flow and connectivity in the marine environment. In particular, for marine species with indirect development gene flow between populations depends on the distance separating the populations and on the interaction between duration of the larval phase, larval behaviour and current patterns. Larval connectivity affects many processes, including stock and population dynamics, species ranges, population genetic structure, and the spread of invasive species and is therefore an important consideration to identify evolutionary relevant population unit and for marine management and conservation efforts. Genetic markers and Individual-based Coupled Physical-Biological Models (ICPBMs) are two of the tools currently available for tracking dispersal pathways of larvae and to assess the degree of population connectivity. The present thesis concerns the spatial and temporal scale assessment of population connectivity of a coastal marine species, the shore crab Carcinus maenas, making use of genetic markers, time series larval supply analysis and an oceanographic numerical model. Chapter 1 introduces the thematic of marine species connectivity, including a brief reference to the molecular, analytical and modelling methods followed during the study. Making use of an interdisciplinary approach – assessment of genetic geographical structure with microsatellite markers within C. maenas native range (Chapter 2), assessment of temporal genetic structure of larvae forming each supply event to the Ria de Aveiro, NW Portugal (Chapter 3), description of interannual variability of larval supply to the Ria de Aveiro, NW Portugal (Chapter 4) and validation of an ICPBM to describe the observed time series of supply (Chapter 5) – the aims of this thesis is to contribute to our understanding of the mechanisms regulating gene flow and connectivity among marine populations. Finally, in Chapter 6 the main results and conclusions achieved are presented. Microsatellites analysis indicated that C. maenas populations were genetically similar across hundreds of km, within the species native range. Additionally, there was no evidence of sweepstakes reproduction in C. maenas from western Iberian coast populations since there were no significant differences amongst larval events. Among larvae in each episode, no genetic relatedness was found, and larvae did not present reduced genetic variability when compared to adult crabs. On a long time scale, larval supply to the Ria de Aveiro was episodic and variable throughout five different studied years, with highest supply numbers generally occurring around spring tides and enhanced by strong southerly winds. The ICPBM was successfully validated and appears to provide a realistic estimate of the observed spatial and temporal scales of the larval dispersal, consistent with the observations on genetic structure and lack of sweepstake reproduction in C. maenas from western Iberian coast.

15

Mondello, Nicholas. "Physical oceanography off the South Coast of Western Australia." Thesis, Mondello, Nicholas (2017) Physical oceanography off the South Coast of Western Australia. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40163/.

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Compared to neighbouring regions of ocean, the south coast of Western Australia (WA) has received relatively little scientific attention despite a range of Australian Commonwealth marine protected areas having been established in the region as of 2012. The ocean off the south coast of WA is characterised by a canyon-dense continental shelf edge including the Bremer Canyon, a shelf edge canyon of approximately 8 km width. There are also two main currents in the region, the eastward flowing Leeuwin Current (LC) situated above the continental shelf edge, and the westward flowing Flinders Current (FC) situated south of the continental shelf. The Blue-link Reanalysis (BRAN) ocean forecasting model simulates the currents, temperature and salinity around Australia at daily intervals from 1994 – 2016 with 1/10th degree resolution. It has been speculated that these currents may interact with the canyons along the shelf edge to induce oceanographic conditions conducive to increased pelagic productivity and ecological diversity. This study was a two-part investigation of the physical oceanography off the south coast of WA with a focus on shelf edge dynamics near Bremer Canyon. It involved the use of the (BRAN) model and in situ data including conductivity, temperature and depth (CTD) profiles during January 2017 and temperature logger measurements from near Bremer Canyon between 2015 and 2017. The BRAN outputs were in close agreement with previous studies of the LC and FC and showed that the mixed layer depth (MLD) was shallowest (<50 m) in summer and deepest in winter (>200 m), in sync with seasonal heat flux. The CTD results were within one SD of the average BRAN profiles and MLD results for January. The volume transport of the LC and strong westerly wind events were dominant drivers of the temperature variation along the shelf edge during autumn and winter of 2015 as the warm LC water was forced downwards. In spring and summer, the volume transport of the LC was lowest (1.6 Sv) and other factors became dominating drivers of the shelf edge temperature variation including eddy kinetics and canyon-related processes. The BRAN outputs effectively simulated the mesoscale features examined in this study including the volume transport of the LC, westerly wind forced response and the influence of mesoscale eddies. These processes have the potential to influence the pelagic ecology through vertical mixing and upwelling.

16

Djurhuus, Anni. "Microbial oceanography of southern hemisphere seamounts and hydrothermal vents." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:727fb8de-a392-4030-bc86-6390143111fd.

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Microbial biogeography is being increasingly more studied, both in terms of genetic divisions and 'ecotype' variation. This thesis investigates the regional (100-1000s km) and local (10s m) distribution and diversity of microorganisms around hydrothermal vents and seamounts at the East Scotia Ridge and the Southwest Indian Ridge. Microbial communities were characterized using Illumina dye sequencing to de- termine taxon richness and diversity and flow cytometry to obtain cell counts. In addition I investigated the physicochemical environment (nutrients, organic carbon, salinity and temperature) in which the microorganisms persist. Typical deep-sea microorganisms were abundant at vents and below the euphotic zone on the seamounts. The surface layer of the seamounts contained typical open-ocean photoautotrophic organisms. Microbial communities were correlated to or- ganic carbon on both hydrothermal vents and seamounts. With microorganisms possi- bly having a large influence on carbon sequestration into the deep-sea from hydrothermal vents. On a local scale the hydrothermal vents had a relatively higher abundance of chemosynthetic Epsilonproteobacteria and the Gammaproteobacteria family SUP05, which were closely correlated to the redox potential in the vent effluent. This was prominent in both plumes from the East Scotia Ridge and the Southwest Indian Ridge, which also had distinct microbial community structures. Across the Southwest Indian Ocean the microbial communities were firstly segregated by depth. However, on a regional scale their physical environment primarily divided the microbial communities into three biological regimes the sub-tropical, con- vergence zone and the sub-Antarctic. The microbial community structure and biogeography is influenced by steep environmental gradients, displaying a distance-decay relationship between sampling locations. With environmental conditions persisting at different scales, from local (10s m) around the hydrothermal vents to regional (100-1000 km) between the seamounts, driving the microbial community patterns. The same horizontal and vertical patterns for microorganisms and metazoans points to fundamental differences throughout all parts of the ecosystem/food web.

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Jarvis, Marley. "Physical Oceanography, Larval Dispersal, and Settlement Across Nearshore Fronts." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/18711.

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The larvae of coastal species interact with nearshore currents that are complex and can alter dispersal. I investigated two sites in southern Oregon with different nearshore hydrodynamics: the first site, Sunset Bay, is a small cove with a topographic front that extends across the mouth during upwelling-favorable winds. Using holey sock drogues at 1.5 m and 5.5 m depths and surface drifters at 10 cm depth, I found that, when the front was present, water at 1.5 m was retained within the bay whereas water was exchanged across the front at a depth of 5.5 m. Surface drifters indicated a surface convergence. Surface plankton tows on either side and within the frontal convergence (a shore-parallel foam line) found significantly higher concentrations of barnacle cyprids, crab megalopae and zoea, polychaete larvae, platyhelminthes juveniles, isopods, amphipods, harpacticoid copepods, and fish eggs. Crustacean nauplii (barnacle, euphausiid, and copepod) and calanoid copepods were not concentrated in the convergence, and when the front and foam line were absent, no taxa were concentrated. Plankton tows taken within the foam line as it dissipated shoreward during a wind-reversal event found that concentrations of cyprids, megalopae, and gastropod veligers remained high as the foam line moved, suggesting that it acts as a moving convergence propagating competent larvae shoreward. I measured settlement of two taxa at Sunset Bay and Shore Acres, an open-coast site <2 km away. Barnacle settlement measured every other day from June-September 2013 was significantly cross-correlated with the maximum daily tidal height at lags of -2 days at Sunset Bay and +2 and +4 days at Shore Acres. Settlement was also significantly negatively cross-correlated with wave height at a lag of -4 days at Sunset Bay. Coralline algae settlement measured during eight 48-hr periods in July-August 2013 was significantly negatively correlated with wave height (n = 8, R2 = 0.76, P = 0.0049) at Shore Acres but not at Sunset Bay. Despite the close proximity of the Sunset Bay and Shore Acres sites, settlement patterns differed between taxa, suggesting that differences in nearshore hydrodynamics might affect the supply of water and larvae to shore. This dissertation includes unpublished co-authored material.

18

Goodlad, Stephen W., and Stephen W. Goodlad. "Tectonic and sedimentary history of the Mid-Natal Valley (S.W. Indian Ocean)." Doctoral thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/23640.

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The Natal Valley is a sediment-filled marine basin situated between the east coast of southern Africa (Natal) and the Mozambique Ridge. Geophysical and sedimentological techniques are used in a broad geological study of the mid Natal Valley. Major emphasis is directed to: (a) basin history and tectonic evolution; (b) seismic stratigraphy of the basin fill; (c) recent sedimentary processes and responses. General basin morphology is defined by five major physiographic provinces: continental shelf and slope, Tugela Cone, Central Terrace, Mozambique Ridge and deep basin plain. Thinned (20-25 km) continental crust, attenuated and subsided in response to Gondwana rifting and drifting, underlies the Central Terrace, Tugela Cone and Mozambique Ridge. Southern margins of the Central Terrace and Tugela Cone are cored by a series of subsea floor ridge and pinnacle complexes (Naude, East Tugela and South Tugela Ridges). Geochemical analyses of East Tugela Ridge basalts suggest a transitional origin but with continental affinities. These volcanic marginal ridges may approximately delineate the continental-oceanic crust boundary (COB) in the Natal Valley. To the south, the deep basin plain is underlain by oceanic crust.
The Natal Valley is a sediment-filled marine basin situated between the east coast of southern Africa (Natal) and the Mozambique Ridge. Geophysical and sedimentological techniques are used in a broad geological study of the mid Natal Valley. Major emphasis is directed to: (a) basin history and tectonic evolution; (b) seismic stratigraphy of the basin fill; (c) recent sedimentary processes and responses. General basin morphology is defined by five major physiographic provinces: continental shelf and slope, Tugela Cone, Central Terrace, Mozambique Ridge and deep basin plain. Thinned (20-25 km) continental crust, attenuated and subsided in response to Gondwana rifting and drifting, underlies the Central Terrace, Tugela Cone and Mozambique Ridge. Southern margins of the Central Terrace and Tugela Cone are cored by a series of subsea floor ridge and pinnacle complexes (Naude, East Tugela and South Tugela Ridges). Geochemical analyses of East Tugela Ridge basalts suggest a transitional origin but with continental affinities. These volcanic marginal ridges may approximately delineate the continental-oceanic crust boundary (COB) in the Natal Valley. To the south, the deep basin plain is underlain by oceanic crust.

19

Bâcle, Julie. "The physical oceanography of waters under the North Water Polynya /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ64314.pdf.

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20

Pruis, Matthew J. "Energy and volume flux into the deep ocean : examining diffuse hydrothermal systems /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10990.

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Dale, Andrew W. "The oceanography and modelling of the Pontevedra Ria (NW Spain)." Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/1966.

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A multidisciplinary study the oceanography of the Pontevedra Ria (NW Spain), including hydrography, biogeochemistiy and biogeochemical modelling, has been performed. The hydrographical variability of the Pontevedra Ria was dependent on freshwater inputs and upwelling of nutrient-rich East North Atlantic Central Water from the shelf. Intrusions of the Poleward Current were also detected during winter. A stratified box model approach predicted that upwelling water fluxes into the ria of 2-4x10³ m³ s-1, of which >30% rises to the surface waters inside the ria. Freshwater residence time varied from ~4-9 d in the central ria and 1-4 d in the internal ria. Nutrients concentrations showed a strong fluvial and oceanic signal, with a clear zone of near-bed aerobic remineralisation in the internal ria. Nutrient flux experiments showed that high nutrient fluxes, particularly ammonium (3.5 mg N mˉ² hˉ¹), coincided with period of high water influx to the ria. These were related to stirring of quasi-benthic phytodetrital fluff. Denitrification was a major fate for particulate organic nitrogen in the sediment, averaging 2.5 mg N m ˉ² h ˉ¹ for the spring and dry season. A non-steady state nutrient budget revealed that the central and internal zones of the Pontevedra Ria display different biogeochemical characteristics. Net community production (NCP) based on phosphate uptake was spatially and temporally variable, with rates of 9.6 and 20.2 mg C m ˉ² h ˉ¹ in central and internal rias in spring, respectively, and 30.3 and 29.0 mg C m ˉ² h ˉ¹ in the dry season. Previously unquantified benthic nutrient inputs were important, and up to 25% of NCP was due to the sediment nutrient flux in the dry season. Denitrification calculated with the nutrient budget equalled 1.82 and 5.66 mg N m ˉ² h ˉ¹ in the dry season in the central and internal ria, respectively, and was equal to 27 and 42% of dry season NCP. The robustness of the box model was questioned, and found to be an unsuitable modelling approach for the Rias Bajas. This had clear implications for predicting NCP and net nutrient budgets to the coastal zone. Salinity and temperature were simulated with the commercially-available simulation shell, ECoS, to within the analytical error of the observed data. Inorganic nutrient concentrations and benthic effluxes were qualitatively and quantitatively agreeable with observed data. Phytoplankton growth in ECoS was limited by up to 30% by phosphorus rather than nitrogen, as previously believed. The annual evolution of NCP was successfully reproduced by examining the chlorophyll-normalised rate of organic carbon production. Mean NCP In the spring and dry season was 46.5 and 147 mg c m ˉ² h ˉ¹, which agreed well with the literature. There were clear discrepancies between box model and ECoS-derived nutrient export to the Atlantic ocean. The definitions of constituent uptake and remineralisation processes between the two approaches were examined In the context of biogeochemical modelling and environmental management of the Rias Bajas.

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Aravamudhan, Shyam. "Development of micro/nanosensor elements and packaging techniques for oceanography." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002219.

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23

Bain, Cairns Alexander Robertson. "Empirical dynamics of a small scale coastal upwelling region." Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/21855.

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The study investigates the dynamics of a small space scale (less than 10 km) coastal upwelling region at the temporal scales spanning hours to years. Three to four year time series data sets of, sea temperatures at different depths (2m, 5 m and 8,5 m) one kilometer offshore, of wind and of waves, obtained from Eskom for the Koeberg nuclear power station site study near Melkbosstrand (33° 41'S, 18° 26'E) were digitized on an hourly basis. An emphasis is placed on the study of the wind and sea temperature data, the latter being an unique data set in the South African context. The data were filtered into different frequency bands (<12,0 <0,5 <0,025 cpd). Simple statistics, linear correlation and spectral analysis were used to characterize these bands. Dominant temporal scales were identified as the seasonal, event (synoptic) and diurnal time scales. The characterization of the latter two time scales were supplemented with field work which inter alia measured: sea temperature profiles and transects; sea surface temperature distribution with the airborne radiation thermometry technique and Lagrangian currents.

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Steffen, Elizabeth Laird. "Observations of vertical and horizontal aspects of deep convection in the Labrador Sea by fully Lagrangian floats /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11028.

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Le, Quéré Corinne. "Physical oceanography of the Baie des Chaleurs, Gulf of St. Lawrence." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56761.

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Time series of temperature and salinity from current meters moored in 1988 and 1990 along the north shore of Baie des Chaleurs were analyzed to characterize the frequency of upwelling events. Upwelling was found to propagate cyclonically with speeds of 40 to 85 km per day. Moderate correlations between $ sigma sb{ rm t}$ and zonal wind stress were found. The interaction of buoyancy, topography, and oscillating wind stress simulated the upwelling in a reduced gravity model. The dominant frequencies of the upwelling events were approximately 4.5 to 10 days.
Three water masses, one between the surface and the thermocline, one straddling the thermocline, and one at the bottom, were found to describe nicely the TS properties of the water column, as observed from the 1991 CTD data.
The observed circulation, from August to October 1990, was cyclonic, with baroclinicity observed in the bottom two layers, and at two stations in the top layers.

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Pierce, David W. "Rotating convection and the oceanic general circulation /." Thesis, Connect to this title online; UW restricted, 1993. http://hdl.handle.net/1773/10993.

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Laudier, Natalie A. "Wave overtopping of a barrier beach." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep%5FLaudier.pdf.

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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 2009.
Thesis Advisor(s): MacMahan, Jamie. "September 2009." Description based on title screen as viewed on 5 November 2009. Author(s) subject terms: Overtopping, run-up, barrier, natural beach, Carmel River Beach Includes bibliographical references (p. 41-44). Also available in print.

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Horn, Isaac Abraham. "Remote Sensing and Data Collection in a Marine Science Application." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/HornIA2006.pdf.

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Barnes, Brian Burnel. "The Combined Effects of Light and Temperature on Coral Bleaching| A Case Study of the Florida Reef Tract Using Satellite Data." Thesis, University of South Florida, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3604824.

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Coral reefs are greatly impacted by the physical characteristics of the water surrounding them. Incidence and severity of mass coral bleaching and mortality events are increasing worldwide due primarily to increased water temperature, but also in response to other stressors. This decline in reef health demands clearer understanding of the compounding effects of multiple stressors, as well as widespread assessment of coral reef health in near-real time.

Satellites offer a means by which some of the physical stressors on coral reefs can be measured. The synoptic spatial coverage and high repeat sampling frequency of such instruments allow for a quantity of data unattainable by in situ measurements. Unfortunately, errors in cloudmasking algorithms contaminate satellite derived sea surface temperature (SST) measurements, especially during anomalously cold events. Similarly, benthic interference of satellite-derived reflectance signals has resulted in large errors in derivations of water quality or clarity in coral reef environments.

This work provides solutions to these issues for the coral reef environments of the Florida Keys. Specifically, improved SST cloudmasking algorithms were developed for both Advanced Very High Resolution Radiometer (AVHRR; Appendix A) and Moderate Resolution Imaging Spectroradiometer (MODIS) data (Appendix B). Both of these improved algorithms were used to reveal the extent and severity of a January 2010 cold event that resulted in widespread mortality of Florida Keys corals. Applied to SST data from 2010, the improved MODIS cloudmasking algorithm also showed improved quantity of SST retrievals with minimal sacrifice in data quality.

Two separate algorithms to derive water clarity from MODIS measurements of optically shallow waters were developed and validated, one focusing on the diffuse downwelling attenuation coefficient (K_d, m^-1) in visible bands (Appendix C), the other on K_d in the ultraviolet (Appendix D). The former utilized a semi-analytical approach to remove bottom influence, modified from an existing algorithm. The latter relied on empirical relationships between an extensive in situ training dataset and variations in MODIS-derived spectral shape, determined using a stepwise principal components regression. Both of these algorithms showed satisfactory validation statistics, and were used to elucidate spatiotemporal patterns of water clarity in the Florida Keys. Finally, an approach was developed to use Landsat data to detect concurrent MODIS-derived reflectance anomalies with over 90% accuracy (Appendix E). Application of this approach to historical Landsat data allowed for long-term, synoptic assessment of the water environment of the Florida Keys ecosystem. Using this approach, shifts in seagrass density, turbidity increases, black water events, and phytoplankton blooms were detected using Landsat data and corroborated with known environmental events.

Many of these satellite data products were combined with in situ reports of coral bleaching to determine the specific environmental parameters individually and synergistically contributing to coral bleaching. As such, SST and visible light penetration were found to be parsimoniously explaining variance in bleaching intensity, as were the interactions between SST, wind and UV penetration. These relationships were subsequently used to create a predictive model for coral bleaching via canonical analysis of principal coordinates. Leave-one-out-cross-validation indicated that this model predicted `severe bleaching' and `no bleaching' conditions with 64% and 60% classification success, respectively, nearly 3 times greater than that predicted by chance. This model also showed improvement over similar models created using only temperature data, further indicating that satellite assessment of coral bleaching based only on SST data can be improved with other environmental data. Future work should further supplement the environmental parameters considered in this research with databases of other coral stressors, as well as improved quantification of the temperature at the depth of corals, in order to gain a more complete understanding of coral bleaching in response to environmental stress.

Overall, this dissertation presents five new algorithms to the field of satellite oceanography research. Although validated primarily in the Florida Keys region, most of these algorithms should be directly applicable for use in other coastal environments. Identification of the specific environmental factors contributing to coral bleaching enhances understanding of the interplay between multiple causes of reef decline, while the predictive model for coral bleaching may provide researchers and managers with widespread, near real-time assessments of coral reef health.

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Bardin, Ann Marie. "Novel Analysis Tools for Ocean Biogeochemical Models." Thesis, University of California, Irvine, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3646712.

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Ocean general circulation models of the IPCC class have biases even when simulating present-day conditions, which may bring into question their predictions of future conditions. This dissertation is about tools for, and results from assessing biases in the Community Earth System Model (CESM) ocean component, by itself and when combined with the Biological Ecosystem Cycling (BEC) model. Newly developed tools and their applications are listed. 1. An offline matrix tracer transport model for the ocean component of CESM. 2. A fast Newton-Krylov implicit tracer equilibrium solver for both the annually-averaged and the seasonally-varying circulation. 3. An effective preconditioner for the solver simulating radiocarbon. Application results: For a natural radiocarbon simulation, an equilibrium solution was obtained in 23 model-years, a dramatic decrease from the 4000 model-years reported for time-stepping. The modeled circulation in the deep Pacific Ocean produced radiocarbon ages twice those of observations. 4. A capability for computing the surface origin of water mass fractions as well as the age of the various water masses.

Application results: The North Atlantic was the major supplier of ventilated water to not only the Atlantic, but also the Pacific and Indian Oceans. A lack of formation of bottom water in the Southern Ocean was discovered. 5. A capability for restricting the tracer simulation domain to a limited region of the ocean while retaining the effectiveness of advection and diffusion fields on the boundary. This reduces computational costs and allows separating local versus remote impacts of tracer sources on the biogeochemical tracer concentrations. This capability has the potential to provide a platform for further biogeochemical studies.

Application results: The Indian Ocean region was isolated. Global versus regional circulation effects were determined using radiocarbon. Most of the bias within the region was eliminated by using observational, rather than globally calculated values, on the boundaries. Oxygen production and consumption from a CMIP5 BEC simulation were used to drive a regional oxygen model. Boundary values of oxygen from the CMIP5 BEC simulation were replaced with observations, resulting in less bias within the region. However, significant bias in the location of the Arabian Sea oxygen minimum zone remained.

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Pickett, Mark H. "Improving wind-based upwelling estimates off the west coasts of North and South America." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FPickett.%5FPhD.pdf.

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32

Kumar, Vijay. "Modelling the physico-biological processes of eastern Arabian sea." Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7093.

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Booth, Charles W. Gutsch Barbara J. "Military applications of intranet technology : Fleet Numerical Meteorology and Oceanography Center /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA337406.

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Thesis (M.S. in Information Technology Management) Naval Postgraduate School, Sept. 1997.
Thesis advisors, James C. Emery, Frank L. Barrett. Includes bibliographical references (p. 145-146). Also available online.

34

Nieves, Calatrava Verónica U. "Multiscale techniques in turbulence: application to geophysical fluids and operational oceanography." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/21617.

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Syahailatua, Augy BEES UNSW. "Biological oceanography of larval fish diversity and growth off eastern Australia." Awarded by:University of New South Wales. BEES, 2005. http://handle.unsw.edu.au/1959.4/22791.

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Fish larvae in Australian waters have been studied progressively in the last 2-3 decades including the distribution and abundance of taxa, growth and age, their prey and predators. However, the effect of nutrient limitation on ichthyoplankton is unstudied, particularly in the oligotrophic Australian waters. My study was aimed to examine the effect of natural or anthropogenic nutrients on the abundance, distribution, growth and condition of fish larvae along-shore of the NSW coast (latitude 30-34S), where the East Australian Current departs the NSW coast and generates local upwelling of cool nutrient-rich water. This study shows no significant difference in the total abundance or diversity of either larval fishes amongst the 112 taxa (111 families and 1 order), among regions within or upstream of the upwelling. However in both months, there were distinctive ichthyoplankton assemblages at the family level. The Carangidae, Labridae, Lutjanidae, Microcanthidae, Myctophidae and Scombridae were more abundant in the EAC or oceanic water masses, while the Callionymidae, Clupeidae, Platycephalidae, Sillaginidae and Terapontidae were mostly found in the surface or deep upwelled/uplifted water masses. This pattern is observed in other ichthyoplankton studies and may be a general and useful method to determine mixing of water masses. Larvae of silver trevally (Pseudocaranx dentex) and yellowtail scad (Trachurus novaezelandiae) were generally larger and less abundant in the topographically induced upwelling region, than north of the region in pre-upwelled conditions of the East Australian Current. Both species were mostly at the preflexion stage (less than 4.3 mm in body length and less than 10 days old) in the pre-upwelled conditions, particularly during November, and proportionally more larger and older larvae in the upwelled waters (mostly post-flexion, greater than 4.3 mm in body length and greater than 10 days old). Ages from sagittal otoliths ranged from 2-25 increments (~days) and exhibited linear growth for both species and months over the size range (3-15 mm standard length). The otolith radius-length relationship and the growth rates were similar between species and months, despite the 3-4C difference between months. Overall growth rates of the younger larvae were uniform throughout the entire sampling area (0.5-0.6 mm.d-1), while older larvae grew significantly faster in the upwelled water (0.41 mm.d-1) compared to the non-upwelled conditions (0.34 mm.d-1). Both species tended to be depleted in 13C in the upwelling region (from ???18.5 to ???19.0), consistent with expected ratios from deeper water, whereas the 15N composition tended to increase in Pseudocaranx, but decrease in Trachurus indicating different diets and possibly trophic level. The early life history of both species indicates spawning in pre-upwelled waters, but larval transport into upwelled waters is necessary for faster growth in the post-flexion stage. The assemblage of larval fishes did differ between the upwelled region and a region south of Sydney???s deepwater outfalls, but the difference was ascribed to a latitudinal effect and the EAC. Both larval carangids were enriched in 15N, possibly due to the enriched dissolved organic matter of primary treated sewage. In summary, this study found that the larval fish community can provide a biological means to trace water masses, and estimate their degree of mixing. Remarkably there was no significant effect of upwelling or sewage addition to the abundance or diversity of larval fish, in the nutrient poor waters of the East Australian Current. Larval carangids and pilchards were abundant in late spring off northern NSW, and their early life histories were inferred. Both larval carangid species seem to be spawned in the EAC waters, but as post-flexion larvae grew faster in the upwelled zone. Pre-flexion (less than 10 day old) larval carangids of both genera indicated spawning in the EAC, and the rarer post-flexion (greater than 10 days old) carangids grew faster in the upwelled waters. Here, both genera had stable isotope signatures characteristic of upwelled waters for carbon, but had different nitrogen signatures, indicative of different diets and trophic level status. Larval pilchards actually grew more slowly in the upwelling region, as observed in coastal waters off Japan, and their nursery grounds may be further offshore in the Tasman Front, analogous to their early life history in the Kuroshio Extension.

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Nieves, Calatrava Veronica Ursula. "Multiscale techniques in turbulence: application to geophysical fluids and operational oceanography." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/21617.

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37

Booth, Charles W., and Barbara J. Gutsch. "Military applications of intranet technology: Fleet Numerical Meteorology and Oceanography Center." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8677.

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Approved for public release; distribution is unlimited
Intranets are rapidly becoming a corporate internal information- sharing medium. Intranet technology is the same robust, proven, industry standard technology that is used on the Internet. The technical aspects of implementing the technology are simple. The organization and management aspects are significant and are key to its successful implementation. This internal use of Internet technology is easy, inexpensive, and has produced savings and benefits for corporate organizations. This thesis reviews corporate and government intranets and examines the feasibility of implementing this technology and benefiting from it, in a military organization. Specific applicability of Intranet technology was examined at Fleet Numerical Oceanographic and Meteorology Center, while maintaining the vision of its applicability to other military organizations. Fleet Numerical Oceanographic and Meteorology Center has the requisite technical and organizational infrastructure necessary to successfully implement Intranet technology. The management and technical skill sets necessary to successfully implement this technology at any military command operating a computer network should be available, or easily trained. Fleet Numerical Oceanographic and Meteorology Center and the U.S. Military should establish the organizational plans and infrastructure to implement and exploit this empowering information sharing medium.

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Addison, Victor G. "The physical oceanography of the northern Baffin Bay-Nares Strait region." Thesis, Monterey, California. Naval Postgraduate School, 1987. http://hdl.handle.net/10945/22417.

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Approved for public release; distribution is unlimited
A dense network of conductivity-temperature-depth measurements was conducted from Baffin Bay northward to 82 deg 09 min N at the entrance to the Lincoln Sea, in the most comprehensive physical oceanographic survey ever performed in the northern Baffin Bay-Nares Strait region. These data indicate Nares Strait Atlantic Intermediate Water and Arctic Basin Polar Water to be derived from Arctic Basin waters via the Canadian Archipelago, whereas the West Greenland Current (WGC) is the source of the comparatively dilute West Greenland Current Atlantic Intermediate Water and West Greenland Current Polar Water fractions. Baffin Bay Surface Water is found seasonally throughout northern Baffin Bay. Recurvature of component branches of the WGC, which attains a maximum baroclinic transport of 0.7 Sv, occurs primarily in Melville Bay (0.2 Sv), south of the Carey Islands (0.1 Sv) and ultimately in Smith Sound (0.2 Sv). The Baffin Current originates as an ice-edge jet in Smith Sound and is augmented by net outflow from Smith, Jones and Lancaster Sounds at rates of 0.3 Sv, 0.3 Sv and 1.1 Sv, respectively. Circulation in Smith, Jones and Lancaster Sounds can be described in terms of the Geostrophic Estuarine Circulation Model. The North Water is caused by the combined influences of near-surface layer enthalpy and mechanical ice removal. KeywordsL Sea water temperature; Oceanographic data; Straits; Sounds(Waterways); Ocean currents

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MacTavish, Flora Pamela. "The application of adaptive mesh techniques to convective processes in oceanography." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11616.

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Idealised numerical simulations of two oceanographic processes, salt finger formation and the restratification phase of open ocean deep convection, are considered. These processes are modelled using the Imperial College Ocean Model (Fluidity-ICOM). This is a finite element code with the novel capability to perform mesh adaptivity. The mesh is triangular/tetrahedral and can be unstructured. If mesh adaptivity is used, all the fields are periodically interpolated onto a new mesh that has been optimised from the previous mesh. The new mesh is designed to represent one or more of the solution fields as accurately as possible by putting more nodes in regions where the Hessians of the fields being adapted to are higher. The first process to be presented is the formation of salt fingers in double diffusive convection. A secondary instability is observed to form. Due to the unstructured mesh, the fingers start off slightly different lengths from each other and this difference is observed to grow with time. A new set of simulations are run in which the secondary instability is initialised from a perturbation in the initial condition. These results are used to compare between fixed and adaptive mesh results. Evidence is obtained to show that adaptive mesh is able to produce the same results as the fixed mesh with fewer computational nodes because the resolution is used in the regions where is it most needed. The second process is the restratification after open ocean deep convection. In order to run ocean scale simulations the model must be able to accurately represent geostrophic and hydrostatic balance on a high aspect ratio domain. In order to do this with an unstructured mesh it is shown that it is necessary to constrain the nodes to be aligned in the vertical. This type of mesh is known as a 2+1 mesh and it can be adapted in both the vertical and the horizontal in order to resolve the solution fields more accurately. The model is able to reproduce previous results for a simple restratification test case using mesh adaptivity. The representation of balance is investigated using different types of mesh and different finite element shape functions. A more complex restratification test case in which baroclinic eddies form is then examined. The results obtained are compared to other models with different numerical schemes. Fixed and adaptive results are compared. These results demonstrate that Fluidity-ICOM is able to represent balance and model relatively complex processes on ocean scale, high aspect ratio domains whilst using mesh adaptivity.

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Reddy, Tasha Elise. "Oceanography of the Ross Sea : ocean circulation, sea ice, and phytoplankton /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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41

Coppini, Giovanni <1974&gt. "Development of operational oceanography applications: environmental indicators and decision support systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2996/1/Coppini_Giovanni_tesi.pdf.

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42

Coppini, Giovanni <1974&gt. "Development of operational oceanography applications: environmental indicators and decision support systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2996/.

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43

Abrahamsen, Einar Povl. "Oceanographic conditions beneath Fimbul Ice Shelf, Antarctica." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/338914/.

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Antarctic ice shelves play a key role in the global climate system, acting as important sites for the cooling of shelf waters, thereby facilitating deep and bottom water formation. Many of the processes that take place under large ice shelves can be observed more conveniently beneath smaller ice shelves such as Fimbul Ice Shelf, an ice shelf in the eastern Weddell Sea. Fimbul Ice Shelf and nearby ice shelves might also play a significant regional role: although no bottom water is produced in this area, it is thought that Fimbul Ice Shelf and nearby ice shelves precondition the shelf waters that ultimately are converted to Weddell Sea Deep Water (WSDW) in the southern Weddell Sea. Using the first data ever to be collected beneath an ice shelf from an autonomous underwater vehicle (AUV), as well as data from the vicinity of the ice shelf using traditional oceanographic methods, this thesis discusses the circulation and processes occurring beneath the ice shelf. This has been supplemented by using a coupled ice shelf/ocean model, POLAIR, to simulate the circulation, melting, and tides under Fimbul Ice Shelf and in the surrounding area. Data from the ice shelf cavity show relatively large variability in temperatures, but all within approx. 0.25 °C of the freezing point. Melt rates are found to be lower than some previous model studies, but in better agreement with observations and glaciological models. The base of the ice shelf was found to be rough in places, corresponding to `flow traces' visible in satellite imagery. This could have implications for mixing beneath the ice shelf, at least in these limited areas. The Autosub AUV was found to be a useful platform for measuring hydrography and ice shelf cavity geometry with spatial coverage and resolution not available from surface measurements.

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Monteiro, Pedro Manuel Scheel. "The oceanography, the biogeochemistry and the fluxes of carbon dioxide in the Benguela Upwelling System." Doctoral thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/18950.

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The aim of this study was to quantitatively investigate the mechanisms which drive carbon fluxes in an eastern boundary coastal upwelling system of which the Benguela is one of four comparable examples in the world. Three hypotheses describe the way the key aspects of the problem: ■ The Benguela upwelling system is, by virtue of its high primary production and sediment organic carbon accumulation rates, an important CO₂ sink. ■ The carbon export flux and the magnitude of the CO₂ sink in the Benguela System can be predicted from the C:N stoichiometry provided by the Redfield Ratio. ■ The inorganic carbon pump through coccolithophore production plays a minimal role in driving changes to the magnitude of both the carbon export flux and the air-sea CO₂ flux in the Benguela System. Carbon and nitrogen bulk water concentrations together with relevant physical parameters were measured along three transects which spanned the Benguela System defining the physical and biogeochemical characteristics of waters at the key stages of the upwelling cycle.

45

Pearson, Ann 1971. "Biogeochemical applications of compound-specific radiocarbon analysis." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/44599.

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Thesis (Ph.D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000.
Includes bibliographical references.
Compound-specific carbon isotopic (613C and A14C) data are reported for lipid biomarkers isolated from Santa Monica Basin (SMB) and Santa Barbara Basin (SBB) surface sediments. These organic compounds represent phytoplanktonic, zooplanktonic, bacterial, archaeal, terrestrial, and fossil carbon sources. The lipids include long-chain n-alkanes, fatty acids (as FAMEs), n-alcohols, C30 mid-chain ketols and diols, sterols, hopanols, and ether-linked C40-biphytanes of Archaea. The data show that the carbon source for most of the biomarkers is marine euphotic zone primary production or subsequent heterotrophic consumption of this biomass. Two lipid classes represent exceptions to this finding. A14C values for the n-alkanes are consistent with mixed fossil and contemporary terrestrial plant sources. The archaeal isoprenoid data reflect chemoautotrophic growth below the euphotic zone. The biomarker class most clearly representing marine phytoplanktonic production is the sterols. It is suggested, therefore, that the sterols could serve as paleoceanographic tracers for surface-water DIC. The isotopic data are used to construct two algebraic models. The first calculates the contributions of fossil and modern vascular plant carbon to SMB n-alkanes. This model indicates that the A14C of the modern component is +235%o (post-bomb) or 0%o (pre-bomb). The second model uses these values to determine the origin of sedimentary TOC. The results are comparable to estimates based on other approaches and suggest that -60% of SMB TOC is of marine origin, modern terrestrial and fossil sources contribute -10% each, and the remaining -20% is of unknown origin.
by Ann Pearson.
Ph.D.

46

Bhushan, Vikas. "Modeling convection in the Greenland Sea." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/58537.

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Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.
Includes bibliographical references (leaves 155-161).
A detailed examination of the development of a deep convection event observed in the Greenland Sea in 1988-89 is carried out through a combination of modeling, scale estimates, and data analysis. We develop a prognostic one-dimensional mixed layer model which is coupled to a thermodynamic ice model. Our model contains a representation of the lowest order boundary layer dynamics and adjustable coupling strengths between the mixed layer, ice, and atmosphere. We find that the model evolution is not very sensitive to the strength of the coupling between the ice and the mixed layer sufficiently far away from the limits of zero and infinite coupling; we interpret this result in physical terms. Further, we derive an analytical expression which provides a scale estimate of the rate of salinification of the mixed layer during the ice-covered preconditioning period as a function of the rate of ice advection. We also derive an estimate for the rate of the mixed layer deepening which includes ice effects. Based on these scale estimates and model simulations, we confirm that brine rejection and advection of ice out of the convection area were essential ingredients during the preconditioning process. We also demonstrate that an observed rise in the air temperature starting in late December 1988 followed by a period of moderately cold ~ -10*C temperatures was key to the development of the observed convection event. Finally, we show that haline driven deep convection underneath an ice cover is possible, but unlikely to occur in the Greenland Sea. On the basis of these results, we develop a coherent picture of the evolution of the convection process which is more detailed than that presented in any previous work. We also comment on the likelihood that deep convection occurred in the Greenland Sea in the past two decades from an examination of historical data, and relate these findings to what is known about the inter-annual variability of convective activity in the Greenland Sea
by Vikas Bhushan.
S.M.

47

Cherian, Deepak Abraham. "When an eddy encounters shelf-slope topography." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107086.

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Abstract:

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 129-135).
Eddies in the ocean move westwards. Those shed by western boundary currents must then interact with continental shelf-slope topography at the western boundary. The presence of other eddies and mean flows complicates this simple picture, yet satellite images show that mesoscale eddies translating near the shelfbreak routinely affect the continental shelves of the Mid-Atlantic Bight, the Gulf of Mexico etc. The consequent cross-shelfbreak transports are currently of unknown importance to shelf budgets of heat, salt and volume. Thus motivated, this thesis uses idealized continuously stratified numerical experiments to explore eddy-slope interactions under four questions: 1. Can the continental slope prevent an eddy from reaching the shelfbreak? 2. What is the structure of the eddy-driven offshore flow? 3. How is the continental shelf affected by an eddy at the shelfbreak? 4. Given surface observations, can one estimate the volume of water transported across the shelfbreak? The experiments show that the efficiency of Rossby wave radiation from the eddy controls whether it can cross isobaths: by radiating energy the eddy becomes shallow enough to move into shallower water. For wide continental slopes, relative to an eddy diameter, a slope can prevent an anticyclone from reaching the shelfbreak by shutting down such radiation. For narrow continental slopes, the interaction repeatedly produces dipoles, whose cyclonic halves contain shelf-slope water stacked over eddy water. The formation of such cyclones is explained. Then, the structure of shelf flows forced by the eddy are studied: their vertical structures are rationalized and scalings derived for their cross-isobath scales; for example, the extent to which the eddy influences the shelf. A recipe for estimating cross-isobath transports based on eddy surface properties is put forward. Finally, the findings are tested against observations in the Middle Atlantic Bight off the northeastern United States.
by Deepak Abraham Cherian.
Ph. D.

48

Ong, Ahchuan. "Diagnostic initialization generated extremely strong thermohaline sources and sinks in the South China Sea." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FOng.pdf.

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49

MacKinnon, Douglas J. "A communication link software model for Fleet Numerical Meteorology and Oceanography Center." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA384723.

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Abstract:

Thesis (M.S. in Information Technology Management) Naval Postgraduate School, Dec. 2000.
Thesis advisor(s): Osmundson, John S. "December 2000." Includes bibliographical references (p. 29). Also available in print.

50

Navarro-Perez, Eleuteria. "Physical oceanography of the Canary current : short term, seasonal and interannual variability." Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318561.

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Dissertations / Theses on the topic 'Oceanography'

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