Les bouches de Bonifacio (Corse du Sud) sont connues pour leur hydrodynamisme violent et la présence d'écosystème marin riche et complexe, géré par une réserve internationale. Pour avoir une bonne connaissance des eaux où vit cette biomasse, des mesures in-situ (courantologiques et hydrologiques) ont été faites lors de 7 missions océanographiques (CYRCE). Grâce à des enregistrements de courant, par deux ADCP (profileurs de courants), l'un mouillé et l'autre embarqué sur le N/o Tethys II (INSU-CNRS), les conditions de courant régissant le milieu sont décrites, globalement et par l'étude de différents cas en relation avec les deux vents dominants (NE et SO). Le traitement statistique des données et leur intégration par un maillage numérique de la zone a permis une première approche des phénomènes majeurs du système des courants. Les données de température, salinité, oxygène dissous, turbidité et fluorescence ont montré les structures caractéristiques et leur variabilité dans l'espace et le temps. Enfin le modèle de simulation 3D Symphonie (laboratoire POC-CNRS-Toulouse) a été adapté aux bouches de Bonifacio sur près d'une année. Ce modèle, a d'abord élargi notre vision de la courantologie sur les parties non couvertes par les mesures in-situ, et permis de comparer les données réelles et simulées. De plus, des outils d'application du modèle, ont permis des simulations de la dispersion de larves à partir des cantonnements de réserve et de dilution de matière, par lâchers de traceurs virtuels et d'en suivre l'évolution sur plusieurs jours, sous différentes configurations.

This paper details a method to compute absolute water velocity profiles from glider-based acoustic Doppler current profiler (ADCP) measurements based on the "shear method" developed for lowered ADCPs. The instrument is a 614-kHz Teledyne RDI ADCP integrated into the body of a Teledyne Webb Research Slocum Glider. Shear is calculated from velocity measurements and averaged over depth intervals to create a dive-averaged shear profile. Absolute velocities are computed by vertically integrating shear profiles yielding relative velocity profiles and then referencing them to dive-average velocity measurements calculated from glider dead-reckoning and GPS. Bottom-track referenced velocities also provide absolute velocities when bottom-tracking is available, and can be applied to relative velocities, producing absolute velocity profiles through linear fitting. Data quality control is based on ADCP percent good measurements. Compass heading bias corrections are applied to the raw ADCP measurements before averaging shear profiles. Comparison between simultaneous, full-water column velocities referenced to dive-average currents and those referenced to bottom-track profiles, resulted in RMS error values of 0.05 m s⁻¹ for both north and east components. During open ocean deployments, the glider ADCP recorded velocities concurrent and proximate to vessel ADCP measurements in waters of similar thermal characteristics. The combined comparison analysis resulted in RMS error values ranging 0.08-0.31 m s⁻¹ and 0.06-0.21 m s⁻¹ for north and east components, respectively. / Graduation date: 2013

In order to better understand the flow dynamics of the Kaoping Submarine Canyon (KSC), this study conducted a series of field experiments to monitor the current, temperature, salinity and tide near the KSC by using shipboard ADCP, CTD and moorings of RCM-8 and workhorse ADCP. Three cruises of Sb-ADCP and CTD have been carried out in September and December of 1999 and May 2000, each lasting two days, while mooring experiment was conducted in June and July, 2000. Least-square fit was applied to the time series Sb-ADCP data of each grid to derive the amplitude and phase of M2 tidal current and the residual flow in the KSC. Our results revealed that a string baroclinic flow field was present in the KSC. Tidal ellipse of the bottom current is dominated by M2 component, with higher M2 percentage in deeper layers. The major axis of the tidal ellipse is parallel to the direction of the canyon axis. In floods, the bottom layer flows down-canyon and the surface layer flows southeastward along the coastline. In ebbs, the situation is reversed. Variations of the temperature and salinity in the bottom layer also exhibit periodic oscillation of the M2 frequency. Daily temperature fluctuation in summer can reach 8 oC, indicating the existence of internal tide in the KSC. The surface residual current flows toward the south east in September and May, with a maximum speed of approximately 30 and 50 cm/s, respectively; the result is probably due to the bifurcation of the summer monsoon flows by the southwestern coastline of Taiwan. In December the surface residual current is northwestward, the maximum speed can reach 80 cm/s. Such a northward mean flow is probably originated from branching of the Kuroshio through Bashi Channel in the winter monsoon season. To summarize, mechanisms for the upwelling event in the KSC consist of surface flow direction, tidal range, and the stratification. The upwelling event occurs more often in the KSC between May and September with the surface mean current flows southeastward or left-bounded. In December when the surface mean current flows northwestward or right-bounded, the upwelling event is rare. An eddy structure of 7 ~ 9 km length scale was observed north of Liu-Chiu Yu, a result possibly produced by Karman vortex street for strong geophysical flows behind an island.

Abstract Kaohsiung Harbor is one of the most important international sea ports in the world. Due to the long-standing lack of in-situ current data, the complex variations of the flow field in this basin still remain unclear. As a consequence, the related environmental problems such as oil spills, water quality management and ship maneuvering safety , have long been a great concern in this harbor. The present study is conducted to better understand the flow field in the Kaohsiung Harbor. A series of synoptic flow observations of the Kaohsiung Harbor were conducted by using towed-ADCP or EM current meters. From these observations it can be shown that the flow field of the Kaohsiung Harbor is¡GWater entering the harbor through the second entrance and exiting the harbor through the first entrance during ebbs. During floods the flows are reversed. A 3-D numerical model (from POM) is developed for the Kaohsiung Harbor. The flows are more complicated by the M2 tide driven than by the mixed tide driven. From the results by the M2 tide driven show the ocean current is variable, especially the south ocean current. Therefore, the flows are more complicated owing to the mixed tidal characteristics and shoreline geometry. The maximum current speeds amount to 30 - 40 cm/s in the narrow first entrance and 10 - 20 cm/s in the second entrance. It is clearly demonstrated from the model results that drainage from the Chien-Chen River affects greatly the salinity and circulation patterns of the Kaohsiung Harbor, causing the salinity of the first entrance to be lower than that of the second entrance, and the surface layers flowing outward toward the ocean while the lower layers displaying tidal oscillations. From the modeling results, the influence of the wind on the harbor flows is insignificant and the tide is main force in the harbor. Under the simultaneous forcing of river and wind, flood and ebb tidal streams leaving the two entrances are found to diverge in a flow stagnation area inside the harbor near Pier 45 and 61, respectively. Based on the modeling results, it can be concluded that the main factors affecting the flow patterns of the Kaohsiung Harbor are (1) mixed tidal nature, (2) shoreline geometry and (3) river runoff

In order to better understand the flow dynamics of the Kaoping Submarine Canyon (KSC), this study conducted a series of field experiments to monitor the current, temperature, salinity and tide near the KSC by using shipboard ADCP, CTD and moorings of RCM-8 and workhorse ADCP. Three cruises of Sb-ADCP and CTD have been carried out in September and December of 1999 and May 2000, each lasting two days, while mooring experiment was conducted in June and July, 2000. Least-square fit was applied to the time series Sb-ADCP data of each grid to derive the amplitude and phase of M2 tidal current and the residual flow in the KSC. Our results revealed that a string baroclinic flow field was present in the KSC. Tidal ellipse of the bottom current is dominated by M2 component, with higher M2 percentage in deeper layers. The major axis of the tidal ellipse is parallel to the direction of the canyon axis. In floods, the bottom layer flows down-canyon and the surface layer flows southeastward along the coastline. In ebbs, the situation is reversed. Variations of the temperature and salinity in the bottom layer also exhibit periodic oscillation of the M2 frequency. Daily temperature fluctuation in summer can reach 8 oC, indicating the existence of internal tide in the KSC. The surface residual current flows toward the south east in September and May, with a maximum speed of approximately 30 and 50 cm/s, respectively; the result is probably due to the bifurcation of the summer monsoon flows by the southwestern coastline of Taiwan. In December the surface residual current is northwestward, the maximum speed can reach 80 cm/s. Such a northward mean flow is probably originated from branching of the Kuroshio through Bashi Channel in the winter monsoon season. To summarize, mechanisms for the upwelling event in the KSC consist of surface flow direction, tidal range, and the stratification. The upwelling event occurs more often in the KSC between May and September with the surface mean current flows southeastward or left-bounded. In December when the surface mean current flows northwestward or right-bounded, the upwelling event is rare. An eddy structure of 7 ~ 9 km length scale was observed north of Liu-Chiu Yu, a result possibly produced by Karman vortex street for strong geophysical flows behind an island.

The internal tide in GPSC¡]Gaoping submarine canyon¡^is the main factor controlling the movement of watermasses. In order to improve our understanding on the compact of suspended sediment exchange in and out GPSC, the data used in this study are collected from four cruises of field observations using research vessel OR3. Instruments deployed include ADCPs¡BEK500¡BCTD and vertical string of temperature loggers. The collected data are analyzed through a variety of time series analysis technique, such as harmonic analysis¡BFFT and EOF. The results show that¡]1¡^the echo intensity recorded by ADCP through calibration could reduce the decay of echo with the distance. The results seem useful to apply in watermass behavior studies.¡]2¡^ Echo intensity with calibration were comparable with signal recorded by EK500 which could be validated to each other. These observations were related to sediment resuspension influenced by internal tide. ¡]3¡^There were two layers of large turbidity, at the depth of canyon edge and near the bottom of canyon, both were fluctuated with two interval tidal frequency.¡]4¡^Another band of echo intensity fluctuations, not directly correlate to sediment resuspension, was likely due to vertical migration, of zooplankton or biology effects.

Tidally-influenced sandwaves are common coastal features present in various settings, including shipping channels. The main shipping channel in Tampa Bay under the Bob Graham Sunshine Skyway Bridge (a.k.a. the Skyway Bridge) contains such sandwave bedforms. Between the years 2000 and 2017, these bedforms have been surveyed with multibeam echosounders (MBES) on 21 occasions with ranging coverage and quality of returns. Surveys between 2000 and 2009 used a 300 kHz Kongsberg EM3000; surveys between 2015 and 2017 used a 400 kHz Reson Seabat 7125. For comparable surveys, bathymetry, backscatter, slope, curvature, planform curvature, and profile curvature maps were created and analyzed. Spectral analyses were completed on the same cross-section for usable surveys, providing a period and amplitude for the bedforms. Sediment samples were taken in September 2015 using a Shipek grab. The sediment samples were analyzed for grain size and carbonate content. A bottom-mounted ADCP recorded velocity data semi-continuously over the same time period. These data were analyzed in an effort to investigate the forcing mechanisms that influence the bedform morphology. Mean grain sizes in the shipping channel under the Skyway Bridge range from 0.01 φ (0.99 mm, coarse sand) to 1.55 φ (0.34 mm, medium sand). Calcium carbonate content ranges from 25% to 87%. The sediment sample site most representative of the sandwave bedforms has a mean grain size of 0.01 φ and a calcium carbonate content of 87%. The calculated mean current velocity required to initiate transport of the D50 and D84 grain size percentile of the representative sediment sample site is 0.70 m/s and 1.05 m/s, respectively. Analysis of the ADCP-recorded velocity data shows that the calculated D50 critical velocity is frequently reached by peak flood and peak ebb currents except during neap tides, while the D84 critical velocity is reached only intermittently, mostly during spring tides. Analysis of MBES backscatter shows similar spatial patterns in two larger MBES surveys in 2004 and 2015. Bathymetric analysis of the sandwaves shows consistent characteristics through time. Wave crest analysis reveals that bedforms migrate in both the ebb and flood directions. Spectral analysis shows primary wave spatial frequencies range from 0.13 m-1 to 0.22 m-1, and primary wave periods range from 4.5 m to 6.0 m. The predominant wavelength of sandwaves within the study area is about 5 m, with an average wave height of 0.47 m. The maximum wave height along the axial cross-section analyzed is 0.8 m, observed in April 2017. The sediments comprising the sandwave bedforms are likely winnowed by tidal currents resulting in larger grain size and carbonate content than other areas of the shipping channel and surrounding bay. Consistent patterns in MBES backscatter over time indicate that the sediment distribution pattern in the study area have not significantly changed. The size and shape of the bedforms in the shipping channel beneath the Skyway Bridge are have been in a quasi-dynamic equilibrium over the past 13 years. The bedforms are shown to migrate in both the ebb and flood directions despite an average faster ebb current velocity than a flood current velocity. More frequent and consistent MBES surveys as well as more continuous ADCP data availability would allow for better understanding of sediment transport via bedform migration in tidally-influenced environments.

Made available in DSpace on 2014-06-12T22:57:05Z (GMT). No. of bitstreams: 2 arquivo1319_1.pdf: 9508440 bytes, checksum: 2d130e75c074b1bdb7ad5408b98dabd3 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2007 / O sistema de modelos SisBaHiA foi utilizado para analisar a circulação hidrodinâmica e o potencial de transporte de partículas da região costeira dos municípios de Recife e Jaboatão dos Guararapes durante o verão austral. Na primeira parte do trabalho, os resultados do modelo hidrodinâmico foram comparados com os dados experimentais obtidos em campo com o perfilador de correntes Acoustic Doppler Current Profiler (ADCP). Para isso foram traçados, perpendicularmente à linha de costa, 13 perfis de correntes, eqüidistantes a 1 km e limitados por isóbatas de 15 m com o uso da carta náutica n° 930. Os vetores resultantes de velocidade da corrente marítima foram calculados a partir das componentes vetoriais horizontais de corrente (U e V) para cada estágio de maré (baixa-mar e preamar) e escala de profundidade (superfície, meio e fundo da coluna d água) de cada perfil. A análise comparativa mostra que o modelo representou melhor a situação real na superfície da coluna d água nas áreas sul e central do domínio modelado durante a baixa-mar e a preamar, respectivamente. Estes resultados se devem à batimetria mais detalhada nestas áreas e à profundidade da coluna d água para os respectivos estágios de maré. Posteriormente, foram analisados os resultados numéricos. Tais resultados evidenciaram que as correntes foram mais intensas nos estágios de maré mais energéticos (vazante e enchente) e na parte sul da área de estudo, devido à forte influência da foz do rio Jaboatão. As intensidades mais baixas ocorreram durante os estágios de maré preamar e baixa-mar, como também próximo à costa, sobre os bancos de recifes submersos (regiões com pouca profundidade), e nas áreas de transição de sentido de corrente. As direções das correntes superficiais durante a enchente foram preponderantemente para SO. Os demais estágios de maré (preamar, vazante e baixa-mar) apresentaram correntes para NO em quase toda a área de estudo, apresentando próximo à área estuarina vetores de corrente para O (preamar e vazante) e SO (baixamar). No meio e no fundo da coluna d água, as direções das correntes durante a preamar e enchente foram para NO, SO e NE ao norte, sul e extremo leste da área de estudo respectivamente. Já durante a baixa-mar e a vazante, as direções preponderantes das correntes foram NE (em quase toda a área de estudo) e SO (na área estuarina). Na segunda parte do trabalho, duas simulações de transporte Lagrangeano foram realizadas em Barra de Jangadas (aporte continental e litorâneo) para retratar o transporte de sedimentos na área de estudo. A pluma de sedimentos permaneceu no domínio modelado durante dois dias, sendo conduzida principalmente pelo movimento oscilatório da maré

Producing electricity from marine renewable resources is a research area that develops continuously. The field of tidal energy is on the edge to progress from the prototype stage to the commercial stage. However, tidal resource characterization, and the effect of tidal turbines on the flow, is still an ongoing research area in which this thesis aims to contribute. In this thesis, measurements of flow velocities have been performed at three kinds of sites. Firstly, a tidal site has been investigated for its resource potential in a fjord in Norway. Measurements have been performed with an acoustic Doppler current profiler to map the spatial and temporal characteristics of the flow. Results show that currents are in the order of 2 m/s in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus has potential for in-stream energy conversion. Secondly, a river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydro power plant, making the site suitable for experiments on the performance of the vertical axis turbine in a natural environment. The turbine was run in steady discharge flows and measurements were performed to characterize the extent of the wake. Lastly, at an ocean current site, the effect that transiting ferries may have on submerged devices was investigated. Measurements were conducted with two sonar systems to obtain an underwater view of the wake caused by a propeller and a water jet thruster respectively. Furthermore, the variability of the intermittent renewable sources wind, solar, wave and tidal energy was investigated for the Nordic countries. All of the sources have distinctly different variability features, which is advantageous when combining power generated from them and introducing it on the electricity grid. Tidal variability is mainly due to four aspects: the tidal regime, the tidal cycle, local bathymetry causing turbulence, asymmetries etc. and weather effects. Models of power output from the four sources was set up and combined in different energy mixes for a “highly renewable” and a “fully renewable” scenario. By separating the resulting power time series into different frequency bands (long-, mid-, mid/short-, and short-term components) it was possible to minimize the variability on different time scales. It was concluded that a wise combination of intermittent renewable sources may lower the variability on short and long time scales, but increase the variability on mid and mid/short time scales. The tidal power variability in Norway was then investigated separately. The predictability of tidal currents has great advantages when planning electricity availability from tidal farms. However, the continuously varying tide from maximum power output to minimum output several times per day increases the demand for backup power or storage. The phase shift between tidal sites introduces a smoothing effect on hourly basis but the tidal cycle, with spring and neap tide simultaneously in large areas, will inevitably affect the power availability.

In the Spring of 2012, hydraulic data was collected to calibrate three types of discharge models: stage-discharge, single-regression and multi-regression index velocity models. Unsteady flow conditions were observed at the site (â H/â t = 0.75 cm/min), but the data did not indicate hysteresis nor variable backwater effects on the stage-discharge relation. Furthermore, when corrected with a datum offset (α) value of -0.455, the stage-discharge relation r2 was equal to 0.98. While the multiple regression index velocity models also showed high correlation (r2 = 0.98) values, high noise levels of the parameter index velocity (Vi) complicated their use for the determination of discharge. Because of its reliability, low variance and accessibility to students, the stage-discharge model [Q = 5.459(H-0.455)^2.487] was selected as the model to determine discharge in real-time for LEWAS. Caution should be used, however, when applying the equation to stages above 1.0m. The selected discharge model was applied to ADCP stage (H) data collected during three runoff events in July 2012. Other LEWAS models showed similar discharge values (coefficient of variation = 0.14) while the on-site weir also produced similar discharge values. Precipitation estimates for July 19 and 24 rain events over the Webb Branch watershed were derived from IDW interpolated rain data and rainfall-runoff analyses from this data yielded an average ratio of 0.23, low for the urbanized watershed. However, since the three LEWAS models were very similar, and the on-site weir showed a lower value to LEWAS, it was concluded that any error in the ratio would be attributed to the precipitation estimate, and not the discharge models developed in this study. / Master of Science