Tesis sobre el tema "Coastal observations"

Coastal cliff erosion is a widespread problem that threatens property and infrastructure along many of the world’s coastlines. The management of this risk calls for robust quantification of cliff erosion rates, which are often difficult to obtain along rocky coasts. Quantification of sea-cliff rates of retreat on annual to decadal time scales has typically been limited to rapidly eroding soft rock coastlines. Rates of erosion used for shoreline management in the UK are generally based on analysis of historic maps and aerial photographs which, in rocky coast environments, does not wholly capture the detail and timing at which the processes operate and the failures occur across the cliff face. The first stage of this study uses airborne LiDAR (Light Detection and Ranging) data at nine sites around a rocky coastline (Cornwall, UK) to gain a quantitative understanding of cliff erosion where average recession rates are relatively low (c. 0.1 m yr-1). It was found that three-dimensional volumetric changes on the cliff face and linear rates of retreat can be reliably calculated from consecutive digital elevation models (DEMs) several years apart. Rates of erosion ranged between 0.03–0.3 m yr-1. The spatial variability in recession rates was considered in terms of the relationship with the varying boundary conditions (rock mass characteristics, cliff geometries, beach morphology) and forcing parameters (wave climate and wave exposure). Recession rates were statistically correlated with significant wave height (Hs), rock mass characteristics (GSI) and the ratio between the two (GSI/Hs). Although the rates derived using airborne LiDAR are comparable to the longer term rates of retreat, the detail of erosion to the cliff-face provides additional insight into the processes occurring in slowly eroding environments, which are vital for understanding the failure of harder rock coastlines. In addition to this, the importance of the wave climate and rainfall needs further attention on a more localised scale. Monthly cliff face volume changes, at two particularly vulnerable sites (Porthleven and Godrevy, Cornwall, UK), were detected using a Terrestrial Laser Scanner (TLS). Using these volumes alongside information on beach profile, beach- cliff junction elevation changes and nearshore hydrodynamics have allowed an insight into how the cliffs respond to seasonal fluctuations in wave climate and beach morphology. Monthly variability in beach morphology between the two sites over a one-year survey period i  indicated the influence that beach slope and the elevation of the beach-cliff junction have on the frequency of inundation and the power of wave-cliff impacts. Failure mechanisms between the two sites ranged from rotational sliding of superficial material to quarrying and block removal over the entire cliff elevation, according to the extent of wave-cliff interaction. This particular survey period highlighted the sensitivity of cliff erosion to the variability in wave climate and beach morphology at two different locations in the south-west of the UK, where the vast majority (over 85% of the annual value) of cliff face erosion occurs during the winter when extreme storm waves prevail. Coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January-March 2014, during the largest Atlantic storms in at least 60 years with deep water significant wave heights of 6 – 8 m, cliff-top ground motions of a rocky cliff in the south-west of the UK (Porthleven, Cornwall) showed vertical ground displacements in excess of 50–100 μm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys, over a 2-week period encompassing the extreme storms, gave a cliff face volume loss 2 orders of magnitude larger than the long-term erosion rate. Cliff-top ground motions and erosion volumes were compared at two different locations, one a reflective beach with steeply shelving bathymetry (Porthleven, Cornwall) and the other an intermediate, low tide bar-rip beach with a wide coastal slope (Godrevy, Cornwall). Under similar wave conditions (6–8 m Hs and 15–20 s. Tp) the vertical ground motions were an order of magnitude greater at the cliffs fronted by steeply shelving bathymetry, where the breaking waves plunge right at the shoreline, with little prior dissipation, leading to large energetic runup impacting the cliff. These storm results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts as well as the wave dissipation that occurs as a function of the nearshore bathymetry. Having recorded microseismic cliff-top motion on this scale for the first time and determined an effective method of monitoring the energetic wave impacts, this study emphasises how investigations of cliff behaviour during storms is not only obtainable, but paramount to understanding coastal evolution under extreme conditions.

Coastal zones receive massive terrestrial inputs of nutrients and organic matter, and play an important role in biogeochemical cycles. The interactions of river inputs, ocean currents, atmospheric exchanges, anthropogenic influences, and biologically active ecosystems make CO2 system studies in coastal waters highly challenging. This work focuses on improving our understanding of the CO2 system in coastal waters through (1) development of a new methodology for measurements of CO2 system parameters in the field; (2) observations of large spatial and temporal CO2 system variations in coastal waters; and (3) characterization of the influence of organics on CO2 system behavior in coastal waters. A novel portable light-emitting-diode (LED) photometer was developed to provide low-cost seawater pH measurements in the field. With meta cresol purple (mCP) as the indicator, the photometer produces pHT measurements within ± 0.01 units of state-of-the-art spectrophotometric measurements (7.6 ≤ pH ≤ 8.2, 30 ≤ S ≤ 36.2, and 15 oC ≤ t ≤ 30 oC). With a simple “do-it-yourself” (DIY) construction design, a hundredfold reduction in cost relative to benchtop spectrophotometric systems, and routine calibration-free operation in the field, the DIY photometer is an ideal replacement for pH test strips or consumer-level potentiometric probes. Applications of special interest include education, citizen science, coastal zone monitoring, and aquaculture and aquarium management. Subannual variability of total alkalinity (TA) distributions in the northeastern Gulf of Mexico (GOM) was examined through the use of TA data from ship-based water sampling, historical records of riverine TA, and contemporaneous model output of surface currents and salinity. Variability of TA observed in the upper 150 m of the GOM water column was primarily controlled by subannual variations in the extent of mixing between seawater and river water. A transition in TA distribution patterns between the river-dominated northern margin (near the Mississippi–Atchafalaya River System) and the ocean current-dominated eastern margin (West Florida Shelf) was observed. A riverine alkalinity input index was developed to highlight riverine TA contributions. Contributions of organic alkalinity (Org-Alk) to TA were investigated in coastal waters from three different environments (estuary, urban, mangrove) and offshore sites in the Gulf of Mexico. The difference in alkalinity (∆TA) between TA measured by direct titration (TAmeas) and calculated (TAcal) from observations of DIC and pH was used as an estimate of Org-Alk. Average values of ∆TA were 0.1 ± 5.0 µmol kg-1 at coastal sample sites outside the Mississippi-Atchafalaya River Estuary (n = 17), 1.9 ± 5.2 µmol kg-1 in offshore waters (n = 14) in the northern Gulf of Mexico, 33.6 ± 18.0 µmol kg-1 in the Suwannee River Estuary (n = 17), and 16.0 ± 25.4 µmol kg-1 in sites that included Tampa Bay, the Caloosahatchee River, and the Ten Thousand Islands area (n = 55). In addition to Org-Alk assessments based on measurements of ∆TA, a novel two-step spectophotometric titration method was developed for the characterization of Org-Alk. Direct titrations showed substantial Org-Alk in coastal samples (n = 5), and the Org-Alk values obtained from the two-step titrations showed good agreement with results from ∆TA calculations. The spectrophotometric titration data were used in model fits to evaluate the dissociation constants (pKi) of the natural organic acids. The pKi of the organic acids were within the previously reported range for riverine fulvic acids.

High-resolution tower observations of turbulent transport processes in the coastal atmospheric surface layer show that the exchange coefficients for momentum, enthalpy, and moisture behave differently for different environmental and atmospheric conditions. The drag coefficient is closely tied to wind speed and turbulent intensity. The exchange coefficient for enthalpy shows a dependence on stability. Analysis of the turbulent kinetic energy budget yields a new parameterization framework that well explains the observed variation of the drag coefficient, particularly at low wind speeds.

In this study, four and a half months of ceilometer data from Östergarnsholm are used to analyze cloud related to processes in the boundary layer. Measurements are divided into two categories, which are defined by wind direction: a continental and a marine sector. The results show that there are significant differences in the height of the lowest cloud bases detected for the two sectors, where cloud base heights are lower for the marine wind sector during unstable and neutral conditions. The ceilometer’s ability to detect several cloud base heights simultaneously is utilized to test whether a double layer structure (DLS) can be detected. The results of this particular analysis are inconclusive as to whether a DLS has been observed or not. Detected cloud base heights differ greatly from heights suggested by the lifting condensation level (LCL). A new empirical formula for lowest cloud base height is then derived using the measurements. The Ceilometer’s estimations of sky cover are assessed to be of reasonable quality. This is suggested by computed high correlation with incoming shortwave radiation at noon for three months.  However, histograms of cloud cover measurements suggest that the ceilometer tends to probably either overestimate or underestimate cloud cover.  Large differences in cloud cover were observed for the two wind sectors during unstable conditions. For the months of July and August, a diurnal cycle in cloud cover for the continental wind sector was observed which suggest the presence of Stratocumulus. Measurements performed during upwelling conditions closely resemble those of the marine wind sector performed during stable conditions.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2009.
Thesis Advisor(s): Herbers, Thomas H. C. ; Janssen, Tim T. "June 2009." Description based on title screen as viewed on July 14, 2009. Author(s) subject terms: ocean waves, continental shelf, mud, littoral, SWAN. Includes bibliographical references (p. 69-71). Also available in print.

Les ondes internes (OI) se propagent dans des milieux stratifiés où elles déforment le gradient de densité et génèrent des courants horizontaux et verticaux. Dans l’océan côtier, différentes formes d’OI peuvent être observées en fonction du profil vertical de densité et des courants avec lesquels les ondes interagissent. Sur les plateaux continentaux les OI génèrent du mélange et du transport qui dépend des caractéristiques des ondes. Dans certaines régions du monde, les OI génèrent du transport comparable au mouvement d’upwelling. Le Golfe de Gascogne est un haut lieu de génération de marées internes et d'ondes internes non linéaires (ONLI). Dans le GdG les OI ont été uniquement caractérisées au large et leurs capacités de transport est inconnue. La première partie de la thèse présente la marée et des ONLI observée pendant 1 mois sur le plateau Aquitain du GdG dans ~60 et 150m de fond. La marée interne et les ONLI de mode 1 ont générés des courants plus de trois fois supérieurs aux courants de marée barotrope. Sous deux pycnoclines, nous avons observé la coexistence et l'interaction d'ONLI de polarités opposées. Dans une seconde partie, nous quantifions le transport côte large sur le plateau Aquitain (62 m de fond) et le plateau Armoricain (48 m de fond) en utilisant les isothermes comme coordonnées verticales d'intégration. Sur le plateau Armoricain, le transport total est dominé par le pompage par les ondes internes. Sur le plateau Aquitain, le transport par les ondes internes domine proche du fond
The Bay of Biscay (BoB) is a hot spot for the generation of internal tides and nonlinear internal waves (NLIW). Previous studies have focused mainly on the seaward propagation of internal waves, and less on the shoreward propagation. The shelf region can be affected by internal tides and NLIW transport. The shelf is a complex hydrodynamical region and processes of different scales modify the background stratification and currents. Therefore, internal waves transform as they propagate across the shelf. Internal wave transformation on the shelf and the induced transport remain poorly described worldwide, especially on the BoB shelves. In this thesis, we describe the internal tide and NLIW from mooring observations on the BoB shelf and the induced cross-shelf transport. First, we describe the internal tide and NLIW on the Aquitaine shelf using 22 days of measurements (at 62 and 153 m depth). The results highlight the unexpected importance of the internal tide and NLIW during summer-time stratified conditions. NLIW of depression and elevation, with amplitude reaching up to 1/4th of the water depth and propagating shoreward with different speeds were observed. We observed conditions in which depression and elevation waves coexisted within the same internal tide phase, and could potentially interact. The second part of the work is dedicated to crossshelf net transport, associated with internal waves, or internal waves pumping (IWP) on both the Aquitaine and the Armorican shelf. On the Armorican shelf, IWP was the main driver of total transport near the boundaries and counterbalanced the subtidal dynamics in the middle of the water column. On the Aquitaine shelf, the total cross-shelf transport was a combination of subtidal transport and IWP

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Includes bibliographical references (leaves 163-172).
A freshwater plume often forms when a river or an estuary discharges water onto the continental shelf. Freshwater plumes are ubiquitous features of the coastal ocean and usually leave a striking signature in the coastal hydrography. The present study combines both hydrographic data and idealized numerical simulations to examine how ambient currents and winds influence the transport and mixing of plume waters. The first portion of the thesis considers the alongshore transport of freshwater using idealized numerical simulations. In the absence of any ambient current, the downstream coastal current only carries a fraction of the discharged fresh water; the remaining fraction recirculates in a continually growing "bulge" of fresh water in the vicinity of the river mouth. The fraction of fresh water transported in the coastal current is dependent on the source conditions at the river mouth. The presence of an ambient current augments the transport in the plume so that its freshwater transport matches the freshwater source. For any ambient current in the same direction as the geostrophic coastal current, the plume will evolve to a steady-state width. A key result is that an external forcing agent is required in order for the entire freshwater volume discharged by a river to be transported as a coastal current. The next section of the thesis addresses the wind-induced advection of a river plume, using hydrographic data collected in the western Gulf of Maine. The observations suggest that the plume's cross-shore structure varies markedly as a function of fluctuations in alongshore wind forcing. Consistent with Ekman dynamics, upwelling favorable winds spread the plume offshore, at times widening it to over 50 km in offshore extent, while downwelling favorable winds narrow the plume width to a few Rossby radii. Near-surface current meters show significant correlations between cross-shore currents and alongshore wind stress, consistent with Ekman theory. Estimates of the terms in the alongshore momentum equation calculated from moored current meter arrays also indicate an approximate Ekman balance within the plume. A significant correlation between alongshore currents and alongshore wind stress suggests that interfacial drag may be important. The final section of the thesis is an investigation of the advection and mixing of a surface-trapped river plume in the presence of an upwelling favorable wind stress, using a three-dimensional model in a simple, rectangular domain. Model simulations demonstrate that the plume thins and is advected offshore by the cross shore Ekman transport. The thinned plume is susceptible to significant mixing due to the vertically sheared horizontal currents. The first order plume response is explained by Ekman dynamics and a Richardson number mixing criterion.
by Derek Allen Fong.
Ph.D.

L'objectif de cette thèse est de comprendre les processus de couplage entre la turbulence et la matière particulaire (sédiments en suspension et phytoplancton). La première partie de la thèse porte sur des mesures in situ effectuées sous différentes situations météorologiques. Nous avons considéré le coefficient d'atténuation, indicateur de la concentration totale de particules in situ, et le spectre de tailles des particules in situ (particle size distribution - PSD). Cette étude a montré que la dynamique de la PSD est contrôlée par plusieurs paramètres océanographiques, tels que les courants de marée, les vagues et la turbulence. Nous avons également étudié les caractéristiques multifractales de ces PSD pour diverses classes de taille (limon, sable fin, sable grossier, particules macro). Pour cela, nous avons utilisé la décomposition modale empirique avec avec l'analyse spectrale de Hilbert. La deuxième partie de la thèse porte sur l'analyse multi-échelle d'images couleur de l'océan et SST (sea surface temperature). L'hétérogénéité spatiale des scalaires océaniques sous l'influence de la turbulence est considérée à multi-échelles. Cette méthode fonctionne également avec des images ayant des données manquantes. Cette méthodologie a été appliquée à des images réelles de Chl-a, SST, Rrs-443 et Rrs-555 en utilisant les fonctions de structure 2D. Il est possible de caractériser, pour toutes les échelles spatiales, les hétérogénéités et intermittences des champs scalaires étudiés, à l'aide de quelques paramètres (deux paramètres dans le cadre de l'approximation log-normale). Les valeurs de ces paramètres, pour sept endroits différents du globe, sont examinés et comparés
The objective of this thesis is to understand the coupling processes between turbulence and particulate matter (suspended sediment and phytoplankton). The first part of the thesis is on in situ measurements performed under different meteorological situations. We selected the attenuation coefficient as a proxy for the total concentration of particles and in situ measurement of particle size distribution (PSD) spectrum. This study showed that the dynamics of the PSD is controlled by many oceanographic parameters such as tidal currents, waves and turbulence. We also studied the multifractal characteristics of these PSD for various size classes (silt, fine, coarse and macro particles). For that, we used Empirical Mode of Decomposition along with the Hilbert Spectral Analysis. The second part of the thesis focuses on the multi-scale analysis of satellite ocean colour and SST images. The spatial heterogeneity of oceanic scalars (phytoplankton and sea surface temperature) under the turbulence influence is considered at different scales. This method also works with images having missing data. Finally, this methodology using 2D structure functions, was applied to real images of Chl-a, SST, Rrs-443 and Rrs-555. It is possible to characterize, for all spatial scales and all intensities, the heterogeneities and intermittencies of the studied scalar fields, using a few parameters (2 parameters in the framework of the lognormal approximation). The values of these parameters, for 7 different locations, are discussed and compared

Snow plays a crucial role in the Earth's hydrological cycle and energy budget, making its monitoring necessary. In this context, ground-based radars and in situ instruments are essential thanks to their spatial coverage, resolution, and temporal sampling. Deep understanding and reliable measurements of snow properties are crucial over Antarctica to assess potential future changes of the surface mass balance (SMB) and define the contribution of the Antarctic ice sheet on sea-level rise. However, despite its key role, Antarctic precipitation is poorly investigated due to the continent's inaccessibility and extreme environment. In this framework, this Thesis aims to contribute to filling this gap by in-depth characterization of Antarctic precipitation at the Mario Zucchelli station from different points of view: microphysical features, quantitative precipitation estimation (QPE), vertical structure of precipitation, and scavenging properties. For this purpose, a K-band vertically pointing radar collocated with a laser disdrometer and an optical particle counter (OPC) were used. The radar probed the lowest atmospheric layers with high vertical resolution, allowing the first trusted measurement at only 105 m height. Disdrometer and OPC provided information on the particle size distribution and aerosol concentrations. An innovative snow classification methodology was designed by comparing the radar reflectivity (Ze) and disdrometer-derived reflectivity by means of DDA simulations. Results of classification were exploited in QPE through appropriate Ze-snow rate relationships. The accuracy of the resulting QPE was benchmarked against a collocated weighing gauge. Vertical radar profiles were also investigated to highlight hydrometeors' sublimation and growth processes. Finally, OPC and disdrometer data allowed providing the first-ever estimates of scavenging properties of Antarctic snowfall. Results presented in this Thesis give rise to advances in knowledge of the characteristics of snowfall in Antarctica, contributing to a better assessment of the SMB of the Antarctic ice sheet, the major player in the global sea-level rise.

Dans la partie ouest du golfe du Lion, Millot (1979, 1982) avait postulé l'existence de tourbillons anticycloniques de mésoéchelle. Comme déjà bien étudié dans l'océan ouvert, ce type de structure pourrait aussi jouer, en zone côtière, un rôle important sur la circulation et sur la biogéochimie, ainsi que dans les échanges de matière et d'énergie entre les zones côtières et hauturières. Les objectifs de cette thèse sont de caractériser les tourbillons anticycloniques à l'ouest du Golfe du Lion et de comprendre leur processus de génération, en utilisant à la fois la modélisation numérique et les données in situ. Le modèle numérique SYMPHONIE est utilisé pour reproduire de manière réaliste la circulation du golfe du Lion afin de nous aider à comprendre la dynamique de ces structures. Une étude de sensibilité sur la résolution spatiale du modèle et sur la diffusion horizontale a été effectuée pour obtenir la configuration optimisée du modèle. L'application de la technique d'analyse en ondelettes sur les résultats du modèle a permis d'identifier les tourbillons et d'estimer leurs caractéristiques (durée de vie, taille,...). Les résultats de la modélisation numérique ont été utilisés pour établir la stratégie des campagnes en mer LATEX et pour nous aider à mieux comprendre les données des mesures in situ. L'analyse des données collectées pendant la campagne Latex08 (1-6 septembre 2008) a confirmé l'existence de tourbillons sur la partie ouest du plateau continental du golfe du Lion et a montré que les caractéristiques des tourbillons observés in situ sont bien comparables avec celles issues des résultats du modèle. Combiné avec les résultats numériques, les mesures in situ ont permis d'améliorer notre connaissance des tourbillons. Grâce à une simulation pluri-annuelle (2001-2008) avec la configuration optimisée choisie, nous avons pu étudier la reproductibilité et la variabilité des tourbillons, et appréhender leur processus de génération. Les résultats de simulation ont montré que, pour chaque année de 2001 à 2008, des tourbillons anticycloniques se produisent régulièrement, de mai à octobre, à l'ouest du Golfe du Lion avec une durée de vie allant de quelques jours jusqu'à plus que deux mois en maximum. Il a été montré que pour qu'un tourbillon de « longue durée de vie » (plus de 15 jours) se développe, deux conditions sont nécessaires: un vent du nord-ouest fort et persistant et une forte stratification de la masse d'eau. L'analyse des effets combinés de ces deux facteurs en fonction de leurs différents degrés d'intensité ont permis d'expliquer la variabilité annuelle et interannuelle des tourbillons générés au cours des 8 ans de simulation numérique
In the western part of the Gulf of Lion, Millot (1979, 1982) had postulated the presence of mesoscale anticyclonic eddies. As already well studied in the open ocean, such structures could also play, in the coastal zone, an important role on the circulation and biogeochemistry, as well as on the coastal-offshore exchanges of energy and mass. The objectives of this PhD thesis is to characterize the anticyclonic eddies present in the western part of the Gulf of Lion and to understand their generation processes, using in a combined way numerical modelling and in situ measurements. The numerical model SYMPHONIE is used to simulate realistically the circulation of the Gulf of Lion, in order to help us understand the dynamics of such structures. A sensitivity analysis has been carried out, varying the model spatial resolution and the horizontal viscosity, to choose the best model configuration. A wavelet technique is applied on model outputs to identify eddies and estimate their characteristics (duration, size...). The numerical results have been used to set up the sampling strategy of the LATEX cruises and help us interpret in situ data. The analysis of the measurements collected during Latex08 (September 1-6 , 2008) confirmed the presence of an anticyclonic eddy in the western part of the Gulf of Lion and showed that its features agree with the ones of the simulated eddy. These in situ data, combined with the modeling results, allow us to better understand the eddies' dynamics. Thanks to a long period simulation (2001-2008) with the appropriate model configuration, we studied the repetitiveness and variability of the eddies, as well as their generation processes. Modeling results showed that during the 8 years of simulation, coastal anticyclonic eddies are present regularly, from May to October, in the western part of the Gulf of Lion with a life duration varying from several days to more than two months. The eddies with a life duration longer than 15 days need two conditions to be generated: a persistent and strong northwest wind and a strong stratification. Annual and interannual differences between the eddies present in the 8 years of simulation can be explained by varying the intensity of each of the two conditions

Elevated water levels and large waves during storms cause beach erosion, overwash, and coastal flooding, particularly along barrier island coastlines. While predictions of storm tracks have greatly improved over the last decade, predictions of maximum water levels and variations in the extent of damage along a coastline need improvement. In particular, physics based models still cannot explain why some regions along a relatively straight coastline may experience significant erosion and overwash during a storm, while nearby locations remain seemingly unchanged. Correct predictions of both the timing of erosion and variations in the magnitude of erosion along the coast will be useful to both emergency managers and homeowners preparing for an approaching storm. Unfortunately, research on the impact of a storm to the beach has mainly been derived from "pre" and "post" storm surveys of beach topography and nearshore bathymetry during calm conditions. This has created a lack of data during storms from which to ground-truth model predictions and test hypotheses that explain variations in erosion along a coastline. We have developed Coastal Lidar and Radar Imaging System (CLARIS), a mobile system that combines a terrestrial scanning laser and an X-band marine radar system using precise motion and location information. CLARIS can operate during storms, measuring beach topography, nearshore bathymetry (from radar-derived wave speed measurements), surf-zone wave parameters, and maximum water levels remotely. In this dissertation, we present details on the development, design, and testing of CLARIS and then use CLARIS to observe a 10 km section of coastline in Kitty Hawk and Kill Devil Hills on the Outer Banks of North Carolina every 12 hours during a Nor'Easter (peak wave height in 8 m of water depth = 3.4 m). High decadal rates of shoreline change as well as heightened erosion during storms have previously been documented to occur within the field site. In addition, complex bathymetric features that traverse the surf-zone into the nearshore are present along the southern six kilometers of the field site. In addition to the CLARIS observations, we model wave propagation over the complex nearshore bathymetry for the same storm event. Data reveal that the complex nearshore bathymetry is mirrored by kilometer scale undulations in the shoreline, and that both morphologies persist during storms, contrary to common observations of shoreline and surf-zone linearization by large storm waves. We hypothesize that wave refraction over the complex nearshore bathymetry forces flow patterns which may enhance or stabilize the shoreline and surf-zone morphology during storms. In addition, our semi-daily surveys of the beach indicate that spatial and temporal patterns of erosion are strongly correlated to the steepness of the waves. Along more than half the study site, fifty percent or more of the erosion that occurred during the first 12 hours of the storm was recovered within 24 hours of the peak of the storm as waves remained large (>2.5 m), but transitioned to long period swell. In addition, spatial variations in the amount of beach volume change during the building portion of the storm were strongly correlated with observed wave dissipation within the inner surf zone, as opposed to predicted inundation elevations or alongshore variations in wave height.

Ne couvrant que 8% de l’océan mondial mais offrant 85% des ressources marines exploitées, les systèmes côtiers sont d’importantes plaques tournantes d’échanges de matières et d’énergie, jouant un rôle capital dans les cycles biogéochimiques. De plus, ces milieux sont marqués par une forte hétérogénéité spatio-temporelle des facteurs environnementaux, contribuant ainsi à leur complexité. Au cours des dernières décennies, les changements globaux s'exerçant sur ces systèmes sont devenus si intenses, que la mise en place de réseaux d'observation à long-terme est devenue cruciale afin d'extraire les grandes tendances et de prédire les changements potentiels. La question de l'identification de la réponse spécifique de ces zones d'interfaces littorales reste cependant posée. En France, le suivi des paramètres physiques et chimiques des eaux côtières est assuré depuis 1997 par le programme SOMLIT (Service d’Observation en Milieu LIToral). L'objectif de cette thèse est de donc caractériser l'évolution physico-chimique, à l'échelle décennale, des systèmes côtiers français et d'estimer les parts respectives de la variabilité naturelle et de l'influence anthropique. Dans un premier temps, l'analyse de ces séries chronologiques montre que les systèmes côtiers français présentent une variabilité temporelle importante, liée en partie aux fluctuations hydro-climatiques à méso-échelle, mais également à des échelles plus régionales. Dans un deuxième temps, le développement d'une nouvelle procédure multivariée non paramétrique, aboutissant à la construction d'états de référence relatifs et à la détection rapide des changements, permet de quantifier le phénomène de fertilisation en nutriments. Il est montré que la fertilisation peut être fortement influencée par le forçage climatique. Dans un troisième temps, après soustraction de la part de variabilité climatique naturelle, des indicateurs de fertilisation anthropique sont proposés, permettant la quantification de l'impact des activités humaines sur les systèmes côtiers français. Ce travail propose une nouvelle approche qui permet de détecter dès que les données deviennent accessibles les perturbations potentielles dans tous types de systèmes, avec plus particulièrement pour objectif de répondre aux attentes, scientifiques et sociétales, d'une gestion adaptée des milieux côtiers
Covering only 8% of the World Ocean but with 85% of exploited marine resources, coastal systems are important areas for the exchange of materials and energy, playing a crucial role in biogeochemical cycles. Moreover, these environments are marked by strong spatial and temporal heterogeneity of environmental factors, contributing to their complexity. In recent decades, global change exerted on these systems has become so intense that the implementation of long-term monitoring programmes has become essential to extract major trends and predict potential changes. However, the identification of the specific response of these coastal systems remains posed. In France, monitoring of physical and chemical parameters of coastal waters is provided since 1997 by the programme SOMLIT (Service d'Observation en Milieu LITtoral). The aim of this PhD Thesis is therefore to characterize year-to-year variability in physic-chemical properties of the surface layer, at a decadal scale, of the French coastal systems, and to evaluate the respective influence of natural and anthropogenic variability. Firstly, the analysis of these time series shows that the French coastal systems exhibit significant temporal variability, due to hydro-climatic fluctuations at meso and regional scales. Secondly, the development of a new nonparametric multivariate procedure, resulting in the constitution of relative reference states for the rapid detection of changes, allows quantifying the fertilization in nutrient concentrations. Moreover, it is shown that fertilization can be strongly influenced by climate forcing. Thirdly, after the removal of natural climate variability, indicators of human fertilisation are proposed, allowing the quantification of the impact of human activities on French coastal systems. This study proposes a new approach to detect as soon as data become available, potential alterations in all types of systems, with the aim of meeting the scientific and societal assumptions and allowing the adaptive management of coastal environments

Dans le contexte de la montée des eaux associée au réchauffement climatique et d’une pression anthropique dans les zones côtières toujours plus forte, une bonne compréhension et modélisation du niveau d’eau total à la côte sont primordiales pour anticiper au mieux le risque côtier et déployer à temps des solutions efficaces. En particulier, l’action des vagues appelée jet de rive joue un rôle important le long des côtes exposées aux houles océaniques. Dans cette étude, nous avons étudié la dynamique du jet de rive dans une plage de poche urbanisée à forts enjeux car soumise aux aléas submersion. Cette étude s’appuie sur de la modélisation numérique à phase-résolue ainsi que des observations. Dans un premier temps, le modèle numérique est validé sur un jeu de données issu d’une expérience en canal à houle. Ensuite, le modèle est appliqué au cas réel de la Grande Plage de Biarritz, et est comparé à des mesures de pression pour les vagues et à des mesures vidéo-métriques pour le jet de rive. Ces applications démontrent les performances du modèle pour estimer le jet de rive, y compris dans un cas réel complexe comme celui de la Grande Plage. Ensuite, les résultats du modèle validé et les observations sont utilisés pour analyser les processus physiques observés à la Grande Plage. Il a tout d’abord été montré que la marée a un impact significatif sur le jet de rive. Á marée basse des conditions dissipatives sont observées où le jet de rive est dominé par les ondes infragravitaires en raison de la faible pente dans la zone de déferlement (2%). Á marée haute, la forte pente présente dans la fin de la zone subtidale et la zone supratidale génère des conditions plutôt réflectives avec une domination des ondes courtes du jet de rive. Cette variation du niveau d’eau a aussi poureffet de moduler la dissipation d’énergie associée aux ondes longues. Pour de faibles niveaux d’eau une dissipation de l’énergie de la bande infragravitaire croissante avec la fréquence est observée, suggérant une dissipation des ondes longues par déferlement. Á l’inverse, à marée haute la forte pente a pour effet de ne plus totalement dissiper l’énergie et un régime nodal estmis en place dû à la réflexion des ondes à la côte. Dans des conditions énergétiques, les vagues ont tendance à déferler en partie sur la pente douce qu’importe le niveau d’eau, réduisant la modulation tidale. Ces résultats montrent la complexité du comportement du jet de rive dans des configurations tridimensionnelles et le potentiel des modèles à phase-résolue pour capturer ces processus
Due to the ever growing anthropogenic pressure at the coast and the perspectives of sea levelrise, coastal hazards such as overtoping are more threatening than ever. In this context, accurateestimations of the wave contributions to the total water level (TWL) at the shoreline, namelythe run-up, are crucial for coastal engineers and those involved in coastal zone managementand engineering design. In this work, we propose to investigate wave run-up in an urban-ized embayed beach based on observations and phase-resolving numerical modeling. First, thephase-resolving model based on the Boussinesq equations BOSZ is validated against laboratoryLiDAR measurements to provide an extensive validation and sensitivity analysis. Then, themodel is applied to the real configuration of the Grande Plage of Biarritz, a complex urbanizedembayed beach. A data-set from a 3-day field campaign carried out in 2018 including pressuremeasurements and video-derived run-up data is utilized for the model validation. These ap-plications demonstrate that the model reproduces wave transformations and subsequent swashmotions reasonably well. The validated model results and observations are then used to investi-gate the swash motions, under varying conditions of waves and tide. Results show that the tidallevel played a key-role in the swash dynamics. At low tide, the conditions were dissipative andthe swash was dominated by the infragravity motions. At high tide reflective conditions wereobserved with a domination of the short-wave frequencies. These changes are explained by thedouble-slope profile where a low sloping area is found in the intertidal zone and a steep slope onthe foreshore. The tidal modulation also influenced the dissipation of infragravity waves, whichwere found to dissipate energy substantially at low tide through breaking, while at mid andhigh tide standing wave patterns, characteristic of shoreline reflection, were observed. Underenergetic conditions the influence of the tide was minimized as the large waves tended to breakon the low sloping portion, regardless of the tide. These results highlight the complexity of theswash behavior in 3D conf

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Coastal bathymetry was measured using wave motion as observed by a commercial satellite imaging system. The linear finite depth dispersion relation for surface gravity waves was used to determine nearshore ocean depth from successive images acquired by the WorldView-2 satellite of the coastal area near Camp Pendleton, California. Principal component transforms were performed on co-registered images and principal component four was found to very effectively highlight wave crests in the surf zone. Change detection images, which included principal component four from successive images, contained both spatial and temporal information. From these change detection images, wave celerity could be determined and depth inversion could be performed. For waves farther from shore, principal component four no longer highlighted wave crests. Waves could be resolved within a single RGB composite image with equalization enhancement. The wavelength of a wave above a known depth was measured and the wave period method was used to determine depth for other waves in the propagation direction of this wave. Our depth calculations compared favorably to our reference bathymetry. The spatial resolution for this method of determining depth is higher and perhaps more accurate than our reference bathymetry, particularly in the surf zone.

This dissertation presents the detailed results of investigations into the coastal geomorphological effects and sedimentation processes associated with a recent large tsunami event which took place on the 12th December 1992 in Flores, Indonesia, and the stratigraphical and sedimentological study of a widespread sand layer preserved in coastal sedimentary sequences along the eastern coast of Scotland representing a low-frequency, high-energy marine event, which took place at circa 7,000 radiocarbon years B.P. With modern alalogues, established in this dissertation, of both tsunami and storm surge sedimentary characteristics and sedimentation processes as the key, together with high-resolution sedimentological evidence obtained from the circa 7,000 radiocarbon years B. P. event, competing hypotheses of the likely causes of the marine flooding by either a tsunami or storm surge event are tested. It is concluded that the circa 7,000 B. P. marine flooding event was a tsunami, believed to have been generated by one of the world's largest submarine landslides in the Norwegian Sea - the Second Storegga Slide. The particle size composition of tsunami sediments is found to vary from well sorted to poorly sorted and is controlled by both the characteristics of the source sedement (local coastal sediments) and sedimentation processes associated with tsunami inundation. Tsunami sediments deposited on land are believed to form continuous and discontinuous sedimentary sheets ascending up to levels distinctively higher than contemporary sea levels and to contain a general landward-fining trend and multiple sets of grading (fining-upward) sequences, reflecting spatial changes in particle size composition. A conceptual model of coastal tsunami sedimentation is established including processes of seaward and landward sediment movements, episodic rapid deposition, sediment accumulation and erosion.

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Subaqueous beach profiles are obtained for littoral regions near Camp Pendleton, CA, using observations of wave motion. Imagery was acquired from WorldView2 Satellite on 24 March 2010. Two sequential images taken 10 seconds apart are used for the analyses herein. Water depths were calculated using linear dispersion relationship for surface gravity waves. Depth profiles were established from shoreline out to 1 kilometer offshore and depths of up to 15 meters. Comparisons with USGS DEM values show agreement within five percent in the surf zone (shoreline to wave breaking) and one percent outside the surf zone (offshore of wave breaking).

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During the warm season (April-September), the California coast is under the influence of persistent northwesterly flow. Periodically, this flow is replaced by a narrow band of southerly winds along the coast. The transition to southerly flow is often accompanied by a rise in sea-level pressure, lower temperatures, coastal stratus, and fog. The mesoscale disturbance responsible for this southerly transition has become known as a coastally trapped wind reversal (CTWR). While it is clear that these mesoscale disturbances are forced by the interaction of the coastal topography with the synoptic-scale flow, the exact mechanisms for their development and their governing dynamics remain the subject of much debate. The present study examines three cases from 1996 that appear to have the characteristics of a CTWR. Each case is analyzed to determine the associated synoptic-scale forcing and the respective mesoscale structure. The observed synoptic-scale forcing is compared to the results of a climafological study conducted by Mass and Bond (1996). Results from a modeling study by Skamarock et al. (1998) are used to create a conceptual model for comparison with the observed development and mesoscale% structure of each event. Results of this study show that only two of the cases can be classified as a CTWR. The study also shows that variability exists in the synoptic-scale forcing associated with the initiation of a CTWR. Two mechanisms for the development of the offshore mesoscale low, and ultimately the CTWR, have been identified. The variability of the mesoscale structure in each CTWR is also documented

Les deltas fluviaux sont des écosystèmes riches et vulnérables. Les apports de sédiments fluviaux assurent leur développement face à la subsidence et l’érosion induite par les agents marins. Les deltas sont principalement exposés à des crues et des submersions marines. Pourtant, ils restent des lieux stratégiques de peuplement, de production économique et d’enjeux géopolitiques, les rendant d’autant plus vulnérables et exposés aux risques. Cette thèse a pour objectif de cerner le fonctionnement passé et actuel de ces systèmes à partir de l’analyse de soixante deltas et d’une approche holistique systémique, à l’aide de données spatiales, environnementales et sociétales. Après l’étude de l’évolution côtière récente montrant une tendance à la diminution de la progradation de nombreux deltas, une classification conceptuelle et qualitative de la morphologie des deltas axée sur les influences fluviomarines a été conduite. La mise à jour de cette classification et la proposition de nouvelles approches, en termes de morphologie, de dynamique et de vulnérabilité, ont nécessité une revue des acquis antérieurs, une quantification de l’influence du fleuve, de la houle et de la marée, et une approche quantitative qui a mis en évidence la complexité des interactions. Le travail débouche sur une nouvelle classification quantitative et objective. La thèse compare aussi les réponses deltaïques à des perturbations exceptionnelles, montrant les limites de la résilience deltaïque. Elle renseigne sur l'impact anthropique sur ces espaces fragiles fortement dépendants de l’apport sédimentaire. Cet équilibre est d’autant plus fragilisé aujourd’hui par les impacts du changement climatique
River deltas are rich and fragile ecosystems. Deltas depend on fluvial sediment supply to balance natural subsidence and erosion caused by waves and currents. Deltas are mainly affected by river flooding, marine submersion. However, deltas are strategic sites of human settlement, economic hotspots, and geopolitical issues. This attraction increases the pressure, rendering these deltas more and more exposed to risks and vulnerable.The main objective of this thesis is to analyze the past and present functional dynamics of delta shorelines based on 60 of the world’s deltas and a holistic and systemic approach with spatial, environmental, and societal data. After the study of recent coastal evolution showing a tendency to decreasing progradation of many deltas, a conceptual and qualitative classification of deltaic morphology based on fluviomarine influences was conducted. Updating of this classification and the proposal of new approaches, in terms of morphology, dynamics, and vulnerability, have necessitated revisiting these older schemes, and the adoption of a methodological and interpretative approach aimed at quantification of the weight of each of these three parameters showing the complexity of the interactions. The thesis proposes a new quantitative and objective classificatory framework, including the human dimension. Finally, the thesis highlights the responses of deltaic shorelines to exceptional perturbations, and highlights the limits of resilience. The thesis advises over the impact of humans on these fragile coastal environments, the equilibrium of which strongly depends on sediment supply. This fragility is further exacerbated by the impacts of climate change

The primary mass input of the Antarctic ice sheet is represented by snow precipitation. Despite of their crucial role, the estimates of precipitation over Antarctica are sparse and characterized by large uncertainties. Recently, the Italian Mario Zucchelli station (MZS) at Terra Nova Bay was equipped with instruments for monitoring precipitation. This thesis is part of the APP-PNRA project (Antarctic precipitation properties from ground-based instruments), whose object is to set up an observatory to characterize precipitation at MZS. The present study was focused on the evaluation of the response of solid hydrometeors to the electromagnetic radiation and on the microphysical characterization of precipitation. The former was investigated using a pre-computed discrete dipole approximation (DDA) database for complex-shape snowflakes and a T-Matrix code for soft-spheroids. The backscattering cross sections, calculated at the K-band by the two methods, were compared. In case of aggregate particles the methods show a poor agreement, comparable values were found when pristine crystals were considered. The latter was examined through in-situ observations by a Parsivel disdrometer and Micro Rain Radar. By exploiting the Parsivel data collected during the summer seasons 2016-17 and 2017-18, the particle size distributions (PSD) of hydrometeors were derived, showing a high number of particles with very small diameter. Numerical simulations, driven by DDA and T-Matrix, were also performed by using the PSDs, to obtain the simulated radar reflectivity. The comparative analysis of simulated and actual reflectivity allowed inferring microphysical characterization of precipitation. Based on this methodology, 16 out of 22 snow days were categorized: 6 as having aggregate-like features and 10 as pristine crystal-like. These results will be of practical interest, giving an important contribution toward a more accurate quantification of snow accumulation in Antarctica.

Time series and spectral analyses are applied to meteorological data (wind velocity, air temperature, barometric pressure) and sea level measurements from a total of 13 monitoring stations along the Turkish Coast. Analyses of four-year time series identify main time scales of transport and motion while establishing seasonal characteristics, i.e. distinguishing, for instance, between winter storms and summer sea-breeze system. Marine flow data acquired by acoustic doppler current profilers (ADCP) is also analyzed to better understand the response of the Turkish Strait System dynamics to short-term climatic variability. The cumulative results obtained from these analyses determine temporal and spatial scales of coastal atmospheric and marine fluxes as affected by the regional climate system

Infragravity waves are low frequency (0.005-0.04 Hz) waves that can dominate the spectrum of water motions and sediment transport processes within the inner surf zone. Despite the established importance of infragravity waves in shaping our coasts and numerous studies dating back to the 1950s, several aspects of infragravity wave analysis, generation and dissipation remain poorly understood. As much of the recent infragravity research has focussed on fetch-limited coasts, less is known about the climatology of these waves on energetic coastlines subject to both swell and fetch-limited waves. It has been postulated that bed friction only plays a significant role in the dissipation of infragravity waves where the bed is exceptionally rough, but the precise impact of bed roughness is not fully understood, particularly on extremely rough rock platforms. Finally, although there have been many methodologies proposed for the decomposition of reflective wave fields (an essential tool for studying infragravity wave dynamics), very little attention has been given to evaluating their accuracy, particularly the impact of uncorrelated noise. This study aims, primarily through the collection of an extensive field dataset and the establishment of accurate analysis tools, to provide new insight into the propagation, dissipation and reflection of infragravity waves on energetic coastlines of varied roughness, subject to both swell and fetch-limited waves. To ensure the accurate decomposition of infragravity wave signals into their incident and reflected components, a sensitivity analysis into the effect of uncorrelated noise on an array separation method is performed. Results show that signal noise, often prevalent in field data, introduces a significant bias to estimates of incident and reflected wave spectra, and corresponding reflection coefficients. This bias can exceed 100% for signal-to-noise ratios of < 1. Utilising the systematic change in coherence with noise, a correction function is developed which is effective at reducing bias by up to 90%. When applied to field data, results imply that infragravity reflection coefficients can be overestimated by > 50% if signal noise is unaccounted for. Consequently, noise reduction should form an integral part of future infragravity wave studies. New research from a dissipative, fetch-unlimited sandy beach (Perranporth, Cornwall, UK) and a macrotidal, rocky shore platform (Freshwater West, Pembrokeshire, UK) uniquely demonstrates that the level of infragravity wave energy close to shore is linearly dependent on the offshore short wave energy flux H_o^2 T_p (r^2 = 0.93and 0.79, respectively). Infragravity waves approach the coast as bound waves lagging slightly (~4 s) behind the wave group envelope and are released in the surf zone where their heights can exceed 1 m. Considerable infragravity dissipation is observed in the surf zone and is a function of both frequency and H_o^2 T_p. Complex Empirical Orthogonal Function (EOF) analysis reveals (quasi-)standing waves at low infragravity frequencies < 0.017 Hz. Conversely, at higher frequencies (>0.017 Hz), infragravity waves demonstrated progressively more dissipation (up to 90%) and progressive wave characteristics, with increasing frequency. Much of the observed dissipation occurs very close to shore (h < 0.8 m) and the dependence of the reflection coefficient on a normalised bed slope parameter implies a mild sloping bed regime at these high infragravity frequencies, suggesting that the observed dissipation is dominated by wave breaking processes. This is supported by the results of bispectral analysis which show predominantly infragravity-infragravity interactions in shallow water and the development of infragravity harmonics indicative of steepening and eventual breaking of the infragravity waves. This study presents the first simultaneous field observations of infragravity waves on a macrotidal, rocky shore platform and adjacent sandy beach. Infragravity wave dissipation is observed on both the platform and beach and occurs at statistically similar rates, demonstrating that frictional dissipation due to bed roughness is not the dominant dissipation mechanism, even in this extreme case. Sea-swell waves are also unaffected by the extreme roughness of the platform, with relative wave heights on the beach and platform (γ = 0.38 and 0.43, respectively) scaling well with their respective gradients and are in very close agreement with formulations derived from sandy beaches. Overall, bed roughness is shown to have no significant impact on infragravity or sea-swell wave transformation, with offshore forcing and bed slope being the main controlling factors, particularly under moderate to high energy offshore forcing.

Les deltas fluviaux sont des écosystèmes riches et vulnérables. Les apports de sédiments fluviaux assurent leur développement face à la subsidence et l’érosion induite par les agents marins. Les deltas sont principalement exposés à des crues et des submersions marines. Pourtant, ils restent des lieux stratégiques de peuplement, de production économique et d’enjeux géopolitiques, les rendant d’autant plus vulnérables et exposés aux risques. Cette thèse a pour objectif de cerner le fonctionnement passé et actuel de ces systèmes à partir de l’analyse de soixante deltas et d’une approche holistique systémique, à l’aide de données spatiales, environnementales et sociétales. Après l’étude de l’évolution côtière récente montrant une tendance à la diminution de la progradation de nombreux deltas, une classification conceptuelle et qualitative de la morphologie des deltas axée sur les influences fluviomarines a été conduite. La mise à jour de cette classification et la proposition de nouvelles approches, en termes de morphologie, de dynamique et de vulnérabilité, ont nécessité une revue des acquis antérieurs, une quantification de l’influence du fleuve, de la houle et de la marée, et une approche quantitative qui a mis en évidence la complexité des interactions. Le travail débouche sur une nouvelle classification quantitative et objective. La thèse compare aussi les réponses deltaïques à des perturbations exceptionnelles, montrant les limites de la résilience deltaïque. Elle renseigne sur l'impact anthropique sur ces espaces fragiles fortement dépendants de l’apport sédimentaire. Cet équilibre est d’autant plus fragilisé aujourd’hui par les impacts du changement climatique
River deltas are rich and fragile ecosystems. Deltas depend on fluvial sediment supply to balance natural subsidence and erosion caused by waves and currents. Deltas are mainly affected by river flooding, marine submersion. However, deltas are strategic sites of human settlement, economic hotspots, and geopolitical issues. This attraction increases the pressure, rendering these deltas more and more exposed to risks and vulnerable.The main objective of this thesis is to analyze the past and present functional dynamics of delta shorelines based on 60 of the world’s deltas and a holistic and systemic approach with spatial, environmental, and societal data. After the study of recent coastal evolution showing a tendency to decreasing progradation of many deltas, a conceptual and qualitative classification of deltaic morphology based on fluviomarine influences was conducted. Updating of this classification and the proposal of new approaches, in terms of morphology, dynamics, and vulnerability, have necessitated revisiting these older schemes, and the adoption of a methodological and interpretative approach aimed at quantification of the weight of each of these three parameters showing the complexity of the interactions. The thesis proposes a new quantitative and objective classificatory framework, including the human dimension. Finally, the thesis highlights the responses of deltaic shorelines to exceptional perturbations, and highlights the limits of resilience. The thesis advises over the impact of humans on these fragile coastal environments, the equilibrium of which strongly depends on sediment supply. This fragility is further exacerbated by the impacts of climate change

Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, September 1994.
Thesis advisor(s): Paul A. Hirschberg, Russell L. Elsberry. "September 1994." Bibliography: p. 56-57. Also available online.

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Meteorological features that force mesoscale weather systems that develop in the central U.S. often form far upstream over the data-sparse Pacific Ocean. It is hypothesized that the temporal and spatial resolution of the current rawinsonde network along the west coast may not he sufficient to detect and measure flow features moving inland. During the STORMFEST experiment in February-March 1992, a Picket Fence' of seven rawinsonde stations were interspersed among the seven regular rawinsonde sites from Port Hardy, British Columbia to San Diego, CA. All sites obtained observations every 3 hours rather than the normal 12 hours. The objective was to examine the feasibility of utilizing extra observations in time and space to improve upstream boundary conditions for forecasts of mesoscale weather events in the central U.S. Fluxes of mass, heat, momentum, moisture, kinetic energy, and potential energy across the west coast resolved with various spatial and temporal combinations of Picket Fence data were compared with the 12-h regular site sondes as the standard. In the best case in which a wave system creased the middle of the Picket Fence, significantly different fluxes were calculated with the full spatial and 3 h Picket Fence observations. For other systems that crossed near the ends of the axis, only small changes were detected by the additional observations

L'acquisition de paramètres marins à partir des données spatiales de la couleur de l'eau nécessite l'élimination de la contribution de l'atmosphère au signal mesuré par le capteur. En effet, la majorité du rayonnement solaire mesuré par les instruments optiques dans les longueurs d'ondes qui intéressent la couleur de l'eau provient de la diffusion par les molécules de l'air et les aérosols atmosphériques. L'élimination de la contribution de l'atmosphère est appelée correction atmosphérique (CA). Pour les eaux claires, les méthodes de CA supposent une réflectance marine nulle dans le proche infra-rouge (PIR). Ceci permet d'estimer la réflectane de l'atmosphère et de l'extrapoler vers les bandes du visible, et donc de déterminer le signal marin qui contient les informations sur les propriétés optiques des eaux marines. Cette hypothèse n'est cependant pas vérifiée pour les eaux turbides, qui représentent la quasi totalité des eaux côtières. Par conséquent, de nombreux algorithmes de CA ont été développés pour les eaux côtières incluant des hypothèses alternatives. L'objectif de ce travail de thèse est de valider et d'améliorer ces méthodes de CA pour les images MODIS Aqua. Pour cela, diverses approches de CA développées pour les eaux cotières ont été comparées et validées : (1) l'algorithme standard de la NASA, (2) le "NIR Similary spectrum algorithm" qui inclut des hypothèes d'homogénéité spatiale des réflectances marines et atmosphériques, (3) l'algorithme qui utilise les bandes dans l'infrarouge moyen pour la CA dans les eaux très turbides, et (4) un algorithme utilisant un réseau de neurones artificiels. L'exercice de validation à partir de données in situ, et en fonction des types d'eaux, a permis d'identifier différentes pistes d'amélioration pour l'estimation du signal marin. L'un d'entre elles comprend l'utilisation de relations spectrales pour forcer les modèles de réflectances marines utilisés par les algorithmes CA pour estimer le signal marin dans le PIR. Des modifications ont été apportées aux modèles de réflectances marines de l'algorithme standard de la NASA et du "NIR Similarity spectrum algorithm". Chacun des modèles a été forcé avec des relations spectrales préalablement validées grâce à des données globales. Une étude de sensibilité et une validation de ces algorithmes modifiés à partir de données MODIS-Aqua dans la Manhe Orientale/Mer du Nord et la Guyane Française ont démontré que les modifications suggérées amélioraient les estimations du signal marin dans les eaux côtières optiquement complexes
To acquire marine parameters from remote sensing ocean color data, the sensor-measured signal needs to be corrected for the atmospheric contribution. Indeed, the solar radiation reflected by air molecules and atmospheric aerosols is significant in the sensor bands of interest for ocean color applications. The removal of the atmospheric contribution is called the atmospheric correction (AC). In open ocean waters, the AC relies on the assumption that the water is totally absorbent in the near infrared (NIR) part of the spectral region, allowing to retrieve the atmospheric contribution and to extrapolate it to the visible spectral range, and thus to determine the marine signal that contains the information on the optical properties of seawaters. However, this assumption is not valid in highly productive and turbid coastal waters. Hence, AC approaches for coastal waters need to rely on alternative assumptions. This Ph. D. thesis has as main objective to validate and improve these AC methods developed for contrasted coastal waters, with a focus on MODIS Aqua images. First, a validation and comparison of existing AC methods, relying on diverse assumptions and methods, is performed. Therefore, four commonly used AC methods are selected, (1) the standard NIR AC approach of NASA, (2) the NIR similarity spectrum AC approach including assumptions of spatial homogeneity in the water and aerosol reflectance, (3) the switching algorithm using the short wave infrared bands for AC in highly turbid waters, (4) an Artificial Neural Network algorithm. With the help of a validation exercise based on in situ data and as a function of the water type, several areas of improvement are delineated, including the use of spectral relationships to constrain NIR-modelling schemes. Modified NIR-modelling schemes are suggested for the standard NASA and NIR similarity spectrum AC methods. Both are forced with globally valid spectral relationships. Sensitivity studies and validation exercises, using MODIS-Aqua images in the Eastern English Channel/North Sea and French Guiana waters, are conducted showing that the suggested modified NIR-modelling schemes improve the estimations of the marine signal in contrasted coastal waters

Since the beginning of the industrial revolution, a large amount of greenhouse gases such as carbon dioxide (CO2) have been emitted into the atmosphere due to human activities. One of the main consequences of these emissions is a rapid increase in atmospheric CO2 concentration and a profound modification of the Earth's climate system. The ocean plays an important role in the Earth radiative balance since it acts as an important CO2 sink for the atmosphere. By currently absorbing about 25 % of the CO2 emitted by humans it considerably slows down climate change. Understanding the present-day spatial and temporal dynamics of the air-sea CO2 exchange and the different processes that govern this exchange is of critical importance to anticipate the evolution of the oceanic CO2 sink in the future.This thesis was realized in this context and focused on an improved quantification of the exchange of CO2 through the air-sea interface (FCO2) of the global ocean, embracing open ocean waters and coastal regions. The main objective was to fill knowledge gaps in our understanding of the processes that govern the spatial and temporal distribution of FCO2. This objective was mainly achieved through observational approaches and addressed three main aspects: a quantification of the different sources of FCO2 uncertainties at the global scale, an analysis of spatial distribution of the oceanic CO2 exchange with a strong focus on the coastal ocean and a first assessment of the coastal seasonal FCO2 dynamics and its underlying drivers. The latter relied on a data-model fusion approach allowing to decompose the FCO2 seasonality into its main physical and biogeochemical drivers. The quantification of the oceanic FCO2 from observations consists in calculating an air-sea partial pressure CO2 gradient (ΔpCO2) between the atmosphere and the sea surface. Global monthly continuous partial pressure of CO2 (pCO2) products can for example be derived from observational pCO2 databases and statistical interpolation methods. This ΔpCO2 is then multiplied by a gas exchange transfer rate coefficient (k), which depends on wind speed. However, the parametrization of k is still entailed with poorly quantified uncertainties. From a literature review of all k parameterizations available in the literature over the past 25 years, I first quantified the FCO2 uncertainties associated with k globally and regionally for the open ocean. I also quantified the uncertainties associated with the choice of a wind product over another. Our results show that the range of global FCO2, calculated with these k relationships, diverge by 12 % when using CCMP, ERA or NCEP1. Regional discrepancies in FCO2 are more pronounced than global. These global and regional differences significantly increase when using NCEP2 or other k formulations. To minimize uncertainties associated with the choice of wind product, it is possible to recalculate the parametrization of k globally for a given wind product and its spatio-temporal resolution, in order to match the last evaluation of the global k value. In a second step, we improved the quantification and analysis of the dominant patterns and drivers of the FCO2 spatial distribution for the coastal ocean worldwide. This analysis was performed globally (at 0.25° spatial resolution), using a regional segmentation of the coastal ocean, and latitudinally. I found that coastal regions at high latitudes act as a CO2 sink while tropical regions and along the equator tend to act as an atmospheric CO2 source. Globally integrated, I quantified that the coastal seas act currently as a CO2 sink with a value of -0.20 ± 0.02 Pg C yr-1. For the first time, I also compared the spatial patterns of coastal FCO2 to that of the adjacent open ocean, globally. With the exception of some regions such as those dominated by riverine inputs, I demonstrated that they present similar latitudinal distribution of their FCO2 density per unit of surface area, suggesting analogous responses to increasing atmospheric CO2. I also reevaluated the global ocean CO2 budget and estimated a global anthropogenic CO2 uptake ranging between -2.6 ± 0.4 Pg C yr-1 and -2.9 ± 0.5 Pg C yr-1 for the 1998-2015 period. In a third step, I contributed to the first continuous observational pCO2 data product merging the coastal and open ocean in a consistent manner. This study showed that difference between open ocean and coastal ocean estimates along the overlap area increases with latitude but remains close to 0 µatm globally. Stronger discrepancies, however, exist on the regional level resulting in differences that exceed 10 % of the climatological mean pCO2, particularly in regions constrained by fewer observations, paired with biogeochemical complexity, such as the Peruvian upwelling system and ice covered regions.In a fourth step, a temporal analysis of the FCO2 seasonality was performed for the coastal ocean based on an observational approach. I analyzed and quantified the FCO2 seasonal dynamics globally and for different latitudinal bands. Globally, coastal regions act as a CO2 sink with a more intense uptake occurring in summer (-21 Tg C month-1) because of the disproportionate influence of high latitude shelves in the Northern Hemisphere. I also estimated the contribution of different drivers (sea-ice coverage, wind speed, and ΔpCO2 change) to the FCO2 seasonal amplitude. This data-driven approach allowed me to conclude that the ΔpCO2 is the main driver of the FCO2 variability at the seasonal timescale. I then used a global oceanic biogeochemical model to decompose the seasonal coastal pCO2 variability further into its driving physical and biological processes. From a first qualitative assessment, I concluded that the thermal effect associated to sea surface temperature changes is the main effect governing the coastal seasonal pCO2 variability except at high latitudes where the non-thermal effect associated to changes in biology, circulation, fresh water and the air-sea CO2 exchange itself dominate. I also found that, overall, the thermal effect alone should lead to larger seasonal fluctuations, but its influence is partly offset by the non-thermal effect. Throughout this thesis, I also evaluated the extent to which the continuous observational pCO2 products derived from an artificial neuronal network approach and from the global ocean biogeochemical model MOM6-COBALT could reproduce the raw pCO2 fields extracted from global databases. Overall, I showed that at the regional scale, the two products are in relatively good agreement compared to observations. I also identified regions where discrepancies are the largest and where future observational data are needed in the future, as well as regions where agreement is the most satisfactory and, thus, most suitable for further process-based analyses.
Depuis le début de la révolution industrielle, une grande quantité de gaz à effet de serre tels que le dioxyde de carbone (CO2) a été émise dans l'atmosphère en raison des activités humaines. L'une des principales conséquences de ces émissions est une augmentation rapide de la concentration en CO2 atmosphérique et une modification profonde du système climatique de la Terre. L'océan joue un rôle important dans l'équilibre radiatif de la Terre car il agit comme un important puits de CO2 pour l'atmosphère. En absorbant actuellement environ 25 % du CO2 émis par l'homme, il ralentit considérablement le changement climatique. Comprendre la dynamique spatiale et temporelle actuelle de l'échange de CO2 air-mer et les différents processus qui régissent cet échange est d'une importance cruciale pour anticiper l'évolution du puits océanique de CO2 à l'avenir.Cette thèse a été réalisée dans ce contexte et s'est concentrée sur une meilleure quantification de l'échange de CO2 à travers l'interface air-mer (FCO2) de l'océan global, considérant à la fois l’océan ouvert et les régions côtières. L'objectif principal était de combler les lacunes dans notre compréhension des processus qui régissent la distribution spatiale et temporelle du FCO2. Cet objectif a été principalement atteint grâce à des approches observationnelles et a abordé trois aspects principaux: une quantification des différentes sources d'incertitudes du FCO2 à l'échelle globale, une analyse de la distribution spatiale de l'échange de CO2 océanique avec un fort accent sur l'océan côtier et une première évaluation de la dynamique saisonnière du FCO2 côtier et de ses moteurs sous-jacents. Ce dernier s'est appuyé sur une approche de fusion de modèles et d’approches observationnelles permettant de décomposer la saisonnalité du FCO2 en ses principaux moteurs physiques et biogéochimiques.La quantification du FCO2 océanique à partir d’observations consiste à calculer un gradient de pression partielle air-mer de CO2 (ΔpCO2) entre l'atmosphère et la surface de la mer. Des produits globaux continus mensuels de la pression partielle de CO2 (pCO2) peuvent par exemple être dérivés à partir de bases de données observationnelles de pCO2 et de méthodes d'interpolation statistique. ΔpCO2 est ensuite multiplié par un coefficient de vitesse de transfert d'échange gazeux (k), qui dépend de la vitesse du vent. Cependant, la paramétrisation de k est sujette à de larges incertitudes et mal quantifiées. À partir d'une synthèse de la littérature de toutes les paramétrisations de k disponibles dans la littérature au cours des 25 dernières années, j'ai d'abord quantifié les incertitudes sur FCO2 associées à k à l'échelle globale et régionale pour l'océan ouvert. J'ai également quantifié les incertitudes associées au choix d'un produit éolien par rapport à un autre. Nos résultats montrent que la gamme du FCO2 global, calculée avec ces différentes paramétrisations de k, diverge de 12 % lors de l'utilisation de CCMP, ERA ou NCEP1. En raison des différences dans les pattern de vent régionaux, les différences régionales sur le FCO2 sont plus prononcés que globalement. Ces différences globales et régionales augmentent de manière significative lors de l'utilisation de NCEP2 ou d'autres formulations de k. Afin de réduire les incertitudes associées au choix du produit de vent, il est possible de recalculer la paramétrisation de k pour un produit de vent donné et à une résolution spatio temporelle.Dans un deuxième temps, nous avons amélioré la quantification et l'analyse des principaux pattern et des différents processus sur la distribution spatiale du FCO2 pour l’ensemble des régions côtières. Cette analyse a été réalisée à l'échelle globale (à une résolution spatiale de 0.25°), en utilisant une segmentation régionale de l'océan côtier, et latitudinalement. J'ai trouvé que les régions côtières aux hautes latitudes agissent comme un puits de CO2 tandis que les régions côtières tropicales et le long de l'équateur ont tendance à agir comme une source de CO2 atmosphérique. Globalement, j'ai quantifié que les régions côtières agissent actuellement en tant que puits de CO2 avec une valeur de -0.20 ± 0.02 Pg C an-1. Pour la première fois, j'ai également comparé la distribution spatiale du FCO2 côtier à celle de l'océan ouvert adjacent, à l'échelle globale. À l'exception de certaines régions telles que celles dominées par les apports fluviaux, j'ai démontré que les régions côtières et l’océan ouvert adjacent présentaient une distribution latitudinale similaire sur leur densité de FCO2 par unité de surface, suggérant des réponses analogues à l'augmentation du CO2 atmosphérique. J'ai également réévalué le budget mondial de CO2 de l'océan et estimé une absorption mondiale de CO2 anthropique comprise entre -2.6 ± 0.4 Pg C an-1 et -2.9 ± 0.5 Pg C an-1 pour la période 1998-2015. Dans un troisième temps, j'ai contribué à la création du premier produit continu de pCO2 observationnelles fusionnant le domaine côtier et l'océan ouvert de manière cohérente. Cette étude a montré que la différence entre les estimations provenant du produit de pCO2 de l’océan ouvert à celles dérivant du produit de pCO2 de l’océan côtier le long de leur zone de chevauchement augmente avec la latitude mais reste proche de 0 µatm globallement. Des divergences plus fortes existent cependant au niveau régional, entraînant des différences qui dépassent 10 % sur la moyenne climatologique de pCO2, en particulier dans les régions contraintes par moins d'observations, associées à une complexité biogéochimique, comme le système d'upwelling péruvien et les régions couvertes de glace.Dans une quatrième étape, une analyse temporelle de la saisonnalité du FCO2 a été réalisée pour l'océan côtier sur la base d'une approche observationnelle. J'ai analysé et quantifié la dynamique saisonnière du FCO2 à l'échelle globale et pour différentes bandes latitudinales. À l'échelle globale, les régions côtières agissent comme un puits de CO2 avec une absorption plus intense se produisant en été (-21 Tg C mois-1) en raison de l'influence disproportionnée des régions côtières des hautes latitudes dans l'hémisphère Nord. J'ai également estimé la contribution de différents processus (couverture de glace de mer, vitesse du vent et changement de ΔpCO2) à l'amplitude saisonnière du FCO2. Cette approche basée sur les données observationnelles m'a permis de conclure que ΔpCO2 est le principal moteur de la variabilité du FCO2 à l'échelle saisonnière. J'ai ensuite utilisé un modèle biogéochimique océanique global pour décomposer davantage la variabilité saisonnière du pCO2 côtier en ses processus physiques et biologiques. À partir d'une première évaluation qualitative, j'ai conclu que l'effet thermique associé aux changements de température de la surface de la mer est le principal effet régissant la variabilité côtière saisonnière du pCO2 sauf aux hautes latitudes où l'effet non thermique associé aux changements de biologie, de circulation, d'eau douce et de l’échange de CO2 air-mer domine. J'ai également constaté que, globalement, l'effet thermique à lui seul devrait entraîner des fluctuations saisonnières plus importantes, mais son influence est en partie compensée par l'effet non thermique.Tout au long de cette thèse, j'ai également évalué dans quelle mesure les produits continus de pCO2 observationnelles dérivés d'une approche de réseau de neurones artificiels et du modèle biogéochimique océanique global MOM6-COBALT pourraient reproduire les champs de pCO2 bruts extraits des bases de données globale. Dans l'ensemble, j'ai montré qu'à l'échelle régionale, les deux produits sont relativement en bon accord par rapport aux observations. J'ai également identifié les régions où les différences sont les plus importantes et où de futures données observationnelles sont nécessaires à l'avenir, ainsi que les régions où les deux produits présentent un accord le plus satisfaisant et, par conséquent, le plus approprié pour de futures analyses de compréhension des différents processus.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

La côte de Guyane française se caractérise par la migration vers le nord-ouest de larges bancs de vase le long des côtes et par une concentration élevée de matières en suspension (MES) résultant de la forte influence des apports du fleuve Amazone. Les bancs de vase régissent la morphologie côtière régionale. Une meilleure compréhension de l’extension et de la dynamique des bancs est cruciale pour une gestion des écosystèmes et activités côtières à l'échelle de la région. Plusieurs études ont été effectuées sur la zone côtière de la Guyane française, fournissant des informations descriptives sur la morphologie et la vitesse de migration des bancs de vase. Cependant, la plupart des études ont porté sur la description des zones intertidales, alors que peu d’entre elles se sont concentrées sur la zone subtidale, qui pourtant, représente la partie la plus étendue des bancs de vase. L’objectif principal de cette thèse est d’adopter trois approches différentes telles que la télédétection haute résolution de la couleur de l’eau et les modèles numériques développés sur la base de mesures in-situ locales afin de mieux comprendre la morphologie de la partie subtidale et l’influence des forçages externes sur sa dynamique. Les précédentes approches sont complémentaires et forment un système de rétroaction interconnecté qui a permis la construction d’un modèle hydro-sédimentaire adapté à l’échelle de la région.L'exploitation optimale des informations fournies par les capteurs récents à haute résolution spatiale tels que Landsat 8-OLI est fortement conditionnée par la qualité du signal de réflectance marine. Ceci implique un développement méthodologique spécifique. L’un des problèmes majeurs en Guyane réside dans la capacité à corriger les données de réflectance marine de la contamination par la réflexion spéculaire du soleil. Ainsi, une méthode automatisée basée sur SWIR a été mise au point à l’aide d’une archive OLI de 4 ans réunie dans les eaux très turbides de la Guyane française. Des résultats satisfaisants basés sur les mesures in-situ de Rrs dans des zones affectées par le reflet du soleil mettent en évidence les performances pertinentes de la méthodologie proposée. La correction des reflets solaires a permis la récupération du signal de réflectance marine et l’estimation de la concentration des MES de surface estimée via le capteur OLI. Une méthode de détection de l'empreinte des bancs de vase a été développée via une approche basée sur les valeurs récurrentes de MES. Des bons résultats sont obtenus lors qu’on les compare à ceux obtenus via une localisation de la limite de l’amortissement de la houle sur les vases fluides subtidales associées aux bancs. Les taux de migration des bancs de vase en Guyane française ont été calculés en utilisant cette délimitation de la partie subtidale des bancs et ont montré des valeurs légèrement supérieures (2,31 km/an) à celles suggérées par des études antérieures
The coast of French Guiana is characterized by the northwestward migration of large mud banks alongshore and by high concentration of suspended particulate matter (SPM) resulting from the strong influence of the Amazon River outflow. Mud banks govern the regional coastal morphology. A better understanding of its extension and dynamics is crucial for the coastal ecosystems management and activities at a regional scale. Several studies have been performed over French Guiana coastal area providing descriptive information about mud-bank morphology and migration speed. However, most studies have centred on the description of intertidal areas, whereas only few have focused on the subtidal zone, the biggest part of mud banks. The overarching aim of this thesis it to adapt two different approaches, such as high resolution remote sensing data and numerical models developed based on in-situ local measurements, to gather better insights into the subtidal part morphology and the influence of external forcings on its dynamics. The latter approaches are complementary and formed an interlinked feedback system that allowed the construction of a hydro-sedimentary model regionally adapted.Optimal exploitation of the information provided by recent high spatial resolution sensors such as Landsat 8-OLI is strongly conditioned by the quality of the water reflectance signal retrieval. This implies specific methodological development. One main issue in French Guiana stands in the ability to correct marine reflectance data for sun glint contamination. Thus, an automated SWIR based method has been developed using a 4-year OLI archive gathered over the very turbid waters of French Guiana. Satisfying results based on in-situ Rrs measurements in sun glint affected areas emphasize the relevant performance of the proposed methodology. Sun glint correction allowed the recovery of the marine reflectance signal and the estimation of surface OLI SPM concentration. A method to estimate the location of mud banks footprint has been developed based on SPM recurring values. A good performance was observed when the results were compared to those obtained by locating the limit of wave damping over the fluid mud of the subtidal part of mud banks. Mud-bank migration rates in French Guiana were calculated according to the delimitation of the subtidal part, and showed slightly higher values (2.31 km/year) than suggested by earlier studies. After obtaining remote sensing data and in-situ measurements, a 2D locally adapted hydro-sedimentary model was constructed based on the information provided by the latter approaches. The model takes into account the combined action of tide, currents, river discharge, wind and waves. Besides, the model also considered hydro-sedimentary processes related to cohesive sediments. Its development has followed three different steps: i) development of the hydrodynamic model; ii) development of the hydro-sedimentary model without considering wave-mud interaction; iii) and incorporation of waves to the hydro-sedimentary model, and has been validated via in-situ measurements and remote sensing data. The influence of the external forcings has been analysed for the dry and the rainy season. Despite the assumptions of the model, it reproduces qualitatively SPM trends and patterns on the subtidal part of the mud bank and the orders of magnitude are comparable to those provided by field and remote sensing data. This PhD provides evidences of the interest of these approaches and the combination of them to obtain better results in such complicated study area. The results obtained may help to further advance the state of knowledge on mud-bank processes and its migration

Les deltas et les régions côtières constituent les sources les plus importantes d'eau douce et de matière en suspension vers le plateau continental puis le large, la compréhension de leur dynamique et de leur variabilité est donc cruciale. Cette thèse vise à mieux comprendre la variabilité spatio-temporelle de la dynamique estuarienne et océanique sous l'influence de forçages naturels et l'influence de cette variabilité sur le transport et devenir des sédiments le long du continuum estuaire - océan côtier du Fleuve Rouge au Golfe du Tonkin. Des observations in-situ collectées dans l'estuaire ont d'abord mis en évidence l'influence de la variabilité saisonnière et de la variabilité due à la marée sur le débit et sur le devenir des matières en suspension, en particulier le rôle du pompage tidal dans l'envasement de l'estuaire. Deuxièmement, un modèle hydrodynamique 3D réaliste, basé sur une configuration haute-résolution et un paramétrage optimisés et validés à partir de plusieurs jeux d'observations in-situ et de données satellitaires, a été utilisé pour l'étude de la circulation à l'échelle du Golfe du Tonkin. Cette configuration a préalablement été optimisée à l'aide de tests de sensibilité des solutions de marée à la bathymétrie et à la paramétrisation du frottement de fond. Les facteurs de la variabilité de cette circulation aux échelles journalière, saisonnière à interannuelle ont été identifiés. La variabilité du transport d'Ekman due à l'inversion saisonnière des vents de mousson a été identifiée comme le principal moteur de la circulation saisonnière, cette dernière pouvant être inversée (intensifiée) en été (hiver) par le passage de typhons. ENSO, l'Oscillation Arctique ou encore une forte activité cyclonique ont été identifiés comme les facteurs de la variabilité interannuelle. Des tests préliminaires avec un module de transport sédimentaire couplé au modèle hydrodynamique ont révélé l'importance, pour la représentation réaliste du transport de matière en suspension, de la composition du sédiment de fond et du paramétrage des coefficients d'érosion
Deltas and coastal regions deliver the largest inputs of freshwater and sediments to the shelf and open ocean, understanding water and sediment dynamics and variability in those regions is therefore crucial. The spatio-temporal variability of estuarine and ocean dynamics under the influence of natural forcings and their impact on sediment transport and fate was assessed along the Red River estuary - coastal ocean - Gulf of Tonkin continuum. First, in-situ estuarine observations evidenced the seasonal and tidal variabilities of flow and suspended matter, and showed in particular the role of tidal pumping in the estuary siltation. Second, a 3D realistic hydrodynamic model was set up and calibrated with various observations and satellite data. Beforehand, a high-resolution model configuration was implemented and optimized with sensitivity tests of the Gulf of Tonkin's tidal components to bathymetry and various bottom friction parameterizations. Third, the resulting optimized configuration was used to study the large scale Gulf of Tonkin circulation at daily, seasonal and interannual scales, and to identify the drivers of their variabilities. Ekman transport variability due to monsoon winds reversal drives the seasonal circulation, which can be reversed in summer by episodic typhoon events and intensified in winter. ENSO, strong typhoon activity and Arctic Oscillation have been identified as drivers of the interannual circulation variability. Lastly, preliminary tests with a sediment transport module coupled with the hydrodynamics model revealed the importance of the seabed composition and of the parameterization of the erosion coefficients

Saltmarshes provide a diverse range of ecosystem services and are protected under a number of international designations. Nevertheless they are generally declining in extent in the United Kingdom and North West Europe. The drivers of this decline are complex and poorly understood. When considering mitigation and management for future ecosystem service provision it will be important to understand why, where, and to what extent decline is likely to occur. Few studies have attempted to forecast saltmarsh morphodynamics at a system level over decadal time scales. There is no synthesis of existing knowledge available for specific site predictions nor is there a formalised framework for individual site assessment and management. This project evaluates the extent to which machine learning model approaches (boosted regression trees, neural networks and Bayesian networks) can facilitate synthesis of information and prediction of decadal-scale morphological tendencies of saltmarshes. Importantly, data-driven predictions are independent of the assumptions underlying physically-based models, and therefore offer an additional opportunity to crossvalidate between two paradigms. Marsh margins and interiors are both considered but are treated separately since they are regarded as being sensitive to different process suites. The study therefore identifies factors likely to control morphological trajectories and develops geospatial methodologies to derive proxy measures relating to controls or processes. These metrics are developed at a high spatial density in the order of tens of metres allowing for the resolution of fine-scale behavioural differences. Conventional statistical approaches, as have been previously adopted, are applied to the dataset to assess consistency with previous findings, with some agreement being found. The data are subsequently used to train and compare three types of machine learning model. Boosted regression trees outperform the other two methods in this context. The resulting models are able to explain more than 95% of the variance in marginal changes and 91% for internal dynamics. Models are selected based on validation performance and are then queried with realistic future scenarios which represent altered input conditions that may arise as a consequence of future environmental change. Responses to these scenarios are evaluated, suggesting system sensitivity to all scenarios tested and offering a high degree of spatial detail in responses. While mechanistic interpretation of some responses is challenging, process-based justifications are offered for many of the observed behaviours, providing confidence that the results are realistic. The work demonstrates a potentially powerful alternative (and complement) to current morphodynamic models that can be applied over large areas with relative ease, compared to numerical implementations. Powerful analyses with broad scope are now available to the field of coastal geomorphology through the combination of spatial data streams and machine learning. Such methods are shown to be of great potential value in support of applied management and monitoring interventions.

The North Florence Dunal Aquifer is the only feasible source for drinking water for the coastal city of Florence, Oregon and Florence's Urban Growth Boundary. High infiltration rates and a shallow groundwater table leave the aquifer highly susceptible to contamination from septic tank effluent, storm runoff, chemical fertilizers and recreational ATV use throughout the dunes. Public interest in the quality and quantity of the aquifer water has been sparked since the City of Florence received a grant from the Environmental Protection Agency for a watershed protection and restoration project. Delineation of the shallow groundwater surface and its relationship to the surface water bodies within the dunes is crucial in protecting this drinking water source from contamination. This thesis project created a GIS representation of the shallow groundwater elevation and associated prediction error map. Surface water bodies were confirmed as window lakes into the dunal aquifer and no signs of perched aquifer conditions were observed between Holocene and Pleistocene dunes. Ground Penetrating Radar, well data provided by the city of Florence and LiDAR were the primary sources for data collection.

Nearly one-third of the world&rsquo
s tortoises live in South Africa, but little is known about their habitat requirements and feeding ecology. Chersina angulata, the angulate tortoise, is endemic to 
southern Africa, with a wide distribution along the western and southern coasts. Because this tortoise occupies a number of different habitat types, it has always been considered a generalist 
herbivore, although little is known about its 
diet and other needs. This study evaluates the habitat characteristics and feeding ecology of C. angulata at two study sites in the southwestern 
 
 
Cape, the West Coast National Park (WCNP) and Dassen Island (DI). The WCNP is a large conserved area in the Fynbos biome, along the southwestern coast of South Africa, whereas DI is a 
small offshore island with low floral and faunal diversity, just south of the WCNP. The efficacy of three methods used to study the feeding ecology of herbivores, focal observations, macroscopic faecal analysis and histological analysis of scats, was evaluated. Plant cover, species diversity, and the variety of growth forms were substantially larger at the WCNP than on DI. 
In the WCNP, shrubs and grasses were the dominant growth forms but the vegetation also included herbs, succulents, restios, sedges and parasitic plants. A few perennial species such as 
the grass Ehrharta villosa, shrubs such as Helichrysum niveum, Nylandtia spinosa and Rhus spp., and succulents such as Carpobrotus edulis and Ruschia spp., provided most of the plant 
cover. DI had a depauperate flora, consisting of succulents and herbs, and ephemeral plants contributed more than perennials did to plant cover throughout the year. The succulents Mesembryanthemum crystallinum and Tetragonia fruticosa provided most of the cover on DI. Angulate tortoises are herbivores and 72 diet plants in 32 plant families were identified to the 
species or genus level. Several diet species, however, could not be identified. In 
addition to angiosperms, the tortoises&rsquo
diet included mosses, mushrooms, insects,snails and animal faeces. 
The most important growth forms in the diet were herbs and grasses. The diet of the WCNP tortoises was more diverse than the diet of DI tortoises, but the number of principal food items in 
the diet did not differ between the two sites. Over an annual cycle, WCNP tortoises had four principal food plants while DI tortoises had five principal food plants. At both sites, principal food 
 
plants changed with the season and few plants remained principal food items in more than one season. Cynodon dactylon was a principal food item in three of the four seasons in the WCNP, whereas Trachyandra divaricata was a principal food plant each season on DI. Most principal food plants were grass or herb species but the sedge Ficinia nigrescens, and a succulent that 
could be identified only to the family level (Aizoaceae), featured strongly in the spring diets of DI and WCNP tortoises, respectively. 
The three study methods did not provide the same type or quality of information about the feeding ecology of angulate tortoises. The small size and wary nature of angulate tortoises compromised focal studies because it was often not possible to see 
what the tortoises ate. This method, however, provided the interesting observation that rabbit 
faecal pellets contributed nearly 30% to summer and autumn diets on DI when food was scarce. 
Rabbit faeces may not only provide a source of nutrients but may also supplement the microflora, required to digest cellulose, in the tortoises&rsquo
guts. Macroscopic evaluation of the tortoises&rsquo
 
scats appeared to be an ineffective method to identify diet plants, and the bulk of the scat mass could not be identified. This indicates 
that angulate tortoises either selected food low in fibrous 
content or that the digestive system of the tortoises dealt efficiently with tough plant material. The macroscopic method was the only method that highlighted the large contribution of 
fruits / seeds to the diet of angulate tortoises. Since the tortoises digested many seeds only partially, or not at all, C. angulata is potentially an important agent of seed dispersal in the southwestern Cape. The macroscopic study showed that on DI, sand made up 28% of the scat mass in spring, whereas sand never made a substantial contribution to the scat composition of WCNP tortoises. Lithophagy may be an important strategy in a depauperate habitat, such as DI, because the abrasive action of sand may help with the digestion of tough plants, or the sand may 
provide the tortoises with important minerals that are deficient in their food plants.The histological analysis of scats provided the most comprehensive diet list for C. angulata. Selection indices 
based on data from the histological analysis indicated that angulate tortoises were highly selective in their food choice. Most of the principal food items were selected out of proportion to their 
availability and the tortoises avoided the most abundant plants in their habitats. Several factors, such as palatability, accessibility and profitability, may have influenced their food choice. The proportional similarity indices for WCNP and DI tortoises, respectively, were 0.31 and 0.16, confirming that C. angulata is a food specialist and not a food generalist as was previously thought. This factor should be considered in the management of this species and in future conservation planning of its habitat. 
 

A radar altimetry satellite measures the height of sea surface globally. However, tide gauges, measuring Sea Level Height (SLH), are set up on the Earth surface. Hence, SLHs are involved in vertical motion of the Earth crust. In this study, vertical motions of Earth crust have been separated from sea level variations. After clustering of SSH observations with K-means approach, two outlier detection methods Pope and Interquartile (IQR) Tests are implemented in data. Afterwards, each altimetry measurement is relocated to the center point of own cluster by means of geoid height derived from Earth Gravitational Model 2008 (EGM08). Before application of Principal Component Analysis (PCA) to see behavior of SSH inbetween clusters, Lomb Scargle algorithm is run to realize power spectrum of every clustered observations distinctly. Besides, tide gauge measurements are used for extracting 68 constituents with T_Tide program from hourly tide gauge observations. Then, predicted signal is produced by means of classical tidal harmonic analysis. To get monthly and daily mean values of hourly data, MSDOS Processing and Quality Controlling Software (SLPR2) has been run and the results are compared with Permanent Service for Mean Sea Level (PSMSL) monthly mean sea level values. Afterwards, the trends from altimetry, tide gauge and GPS are investigated to reveal vertical land motion. This study shows that sea level is rising every year more or less 7 mm at the Mediterranean coast of Turkey. Although Iskenderun tide gauge subsides 50 mm every year, the other stations do not show huge amount of vertical motion.

The migration of Southern Hemisphere humpback whales Megaptera novaeangliae between their feeding and breeding areas is considered a highly predictable and seasonal event. The west coast of Africa is host to Breeding Stock (BS) B, which has been divided into sub-stocks B1 and B2 based on different catch histories observed between Gabon in the north, and other stations to the south – a notion supported by recent regional genetic analysis, some samples of which were collected during this project. It has thus been assumed that the west coast of South Africa (WSA) functions as a migratory corridor for BS B2 whales. While catch data from Saldanha Bay in 1911-12 supported the existence of two migration peaks, a pilot study in the spring of 1993 (the first dedicated study in over 80 years) suggested a more atypical pattern, with some whales apparently abandoning or suspending their migration, possibly to feed. This has been complicated further by the detection of direct transits of 10 individual humpbacks through microsatellite matches between Gabon and WSA, and has raised questions about the exact function and relationship of WSA to BS B humpback whales. This thesis presents the results from a study based at Saldanha Bay that included shore-based observations of whale groups during two field seasons (July – December 2001, May 2002 - February 2003), and photographic and genetic data collected during boat intercepts from 1983 to 2008. The observed relative abundance of humpback whales again did not support a classical migration pattern, with the highest sighting rates from mid-spring through summer. Movement patterns of humpback groups tracked by theodolite showed mid-spring to be a turning point in their behaviour, after which they swam significantly slower, showed an increase in ‘non-directional’ movement, and were found farther from shore. Data on group composition and sex showed a significantly female-biased sex ratio during mid-spring, unlike most low-latitude areas where males predominate. The individual identification of humpback whales by means of photographs of ventral tail flukes, left and right dorsal fins, and through microsatellites, yielded numerous resightings at intervals of a year or more, indicating a high level of fidelity to the region and temporary residency by some individuals. Population estimates were calculated using open and closed capture-recapture models and suggest that about 500 animals are present in the area during the spring/summer season. Direct observation of humpback whales feeding on crustacean prey, short-term association patterns, and the resighting of individuals participating in feeding aggregations in multiple years confirmed this area to be a feeding ground for humpback whales during spring and summer months. Concurrent shore-based observations on southern right whales Eubalaena australis showed that this species was present virtually throughout the study period, also utilising feeding opportunities during summer. The potential benefit of this mid-latitude feeding area for humpback females is illustrated by a record of a cow that produced calves in three consecutive years, each of which survived to at least six months of age - the first observation of post-partum ovulation for this species in the Southern Hemisphere. The return of three known calves to the same area is strongly suggestive of maternally derived site fidelity.
Thesis (PhD)--University of Pretoria, 2012.
Zoology and Entomology
PhD
Unrestricted

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)
The basic biology and ecology of Etrumeus wongratanai was investigated from samples of fish collected by jigging off Scottburgh, Kwazulu-Natal throughout 2014 and 2015. A total of 516 otoliths, 401 gonads, 140 stomachs and 163 samples of white muscle tissue was examined, and length and weight data of 3 637 fish caught between 2013 and 2016 was also analysed. Counts of annuli deposited on sagittal otoliths indicate that sampled E. wongratanai ranged from 0 to 3 y. (year/s) of age. Length-at-age for males (females) was estimated at 15.5 cm (16.2 cm) for 1 y. olds, 17.7 cm (17.4 cm) for 2 y. olds and 19.6 cm (18.8 cm) for 3 y. olds. The length at 50% maturity was estimated to be 15.6 cm for males, and 16.1 cm for females. Etrumeus wongratanai showed high gonadosomatic index values from June to December indicating that the breeding season lasts for 6 and 8 months for males and females, respectively, and that spawning takes place from the onset of winter to early summer. Condition factor was lowest in May through to August and increased from September. The low condition factor values from May through to August could be due to the physiological strain before and during the spawning season. Fish larvae were the most important food item in samples collected in summer, whereas eucalanids were the most important prey item in autumn and winter. Overall, large copepods were the dominant prey items in terms of frequency and importance. Stable isotope data suggests that there are gradual changes in the trophic level and diet of E. wongratanai as it increases with size, and whilst δ¹⁵N values differed between seasons δ¹³C did not. The results obtained here are compared with other species of Etrumeus, regionally and globally.
National Research Foundation (NRF) and ACEP Phulisa

The vast distribution and long duration of the Late Mesozoic magmatism in the eastern part of South China presents a unique case in the world. This offers a natural laboratory to study the process of magma genesis, the magma emplacement mode, the relationship between magmatism and tectonics, the geodynamic role on the magma emplacement and lithospheric evolution. Since 50's, particularly 90's of the last century, geoscientists have made important efforts in geological cartography and carried out numerous studies with remarkable scientific achievements, building a solid background to understand the tectonic evolution of the South China Block (SCB). However, certain fundamental questions mentioned above remain unsolved and/or are in hot debate. In order to make progress in these scientific issues, we have carried out in a multi-disciplinary study in the Late Mesozoic Qingyang-Jiuhua massif, Hengshan massif and Fujian coastal zone according to their distance with respect to the paleo subduction zone of the Paleo-Pacific plate, the ages of granitic massifs and related tectonics, including field observation on the structure geology, micro-observation on thin section, U-Pb dating on monazite, AMS, paleomagnetism, gravity modeling and P condition concern the granite emplacement. In the view of deformation in these granitic massifs and their country rocks, mode and influence of regional tectonics on the emplacement, though each studied zone reveals its distinguished characteristics, they show some intrinsic and common relationships between them. With our new results and integrating previous data, in this thesis, we discuss the tectonic context of emplacement of these Late Mesozoic magmatic massifs and the geodynamic evolution of the SCB., We propose a 3-step geodynamic model: (1) during 145-130 Ma period, the Paleo-Pacific plate subducted northwestwardly, the West Philippines micro-continent, approaching to SCB, important subduction-related arc volcanism was produced in the coastal areas of Southeast China coast (Zhejiang-Fujian-Guangdong), forming a back-arc extension tectonic system in SCB; (2) during 130-110 Ma period, due to the collision between the West Philippines microcontinent and SCB, the compressional tectonic structures were developed in the Changle-Na'ao coastal zone, producing ductile deformation zones. However, the inland of the eastern part of SCB was under a NW-SE extensional tectonic regime; (3) during 105-90 Ma period, a new subduction zone was developed in the SE flank of the West Philippines micro-continent, the subducting slab reached the Changle-Nan'ao tectonic belt, with the possible break-off of slab, the asthenospheric ascent was responsible for the important emplacement of plutonic massifs and dykes. The tectonics of the eastern part of SCB was characterized by a general extensional system in this period. This tectonic pattern has been significantly disturbed by the Oligocene-Eocene opening of the South China sea,and the Miocene shortening of the SCB margin in Taiwan. Of course, this model should be improved by more geological, geophysical and geochemical investigations.

碩士
國立臺灣海洋大學
應用地球科學研究所
98
In the north Taiwan, the pocket–like Guo-sheng Bay is located between Jin-shan and Ye-liu caps with its opening towards northeast. Inside the bay at Wan-li country, the nuclear energy plant No.2 was built by Taipower Company and its 200-meter-long water outlet blocked the originally continuous coastline. The purpose of this study is to study whether the nearby sandy coast will be affected by the artificial construction. This study purchased the aviation digital photos from Aerial Survey Office, Forestry Bureau from 1979 to 2007. After ortho-rectification of the digital photo data, the sequential coastlines were extracted with the Geographical Information System. Afterwards, the extracted six years’ coastlines were overlaid one another to study the artificial effects. Meanwhile, by integrating the wave incidence direction, we found there is a obvious northwest longshore current in the north of study area and a slight southeast longshore current in the south of study area. Based on the results of the study, I found that the shore area changes with different seasons. For Example, the beach surface is wide and steep in winter time and narrow and smooth in summer time without typhoon influence. By the grain-size and mineral composition analyses of sediments, the sediments of this area are mainly derived from the source area through the Yuan-ten River. To sum up the results of the study, the coastline has slightly and repeatedly shifted back and forth during the last three decades. Therefore, the coastline is in a stable status and not affected by the water outlet of nuclear power plant no.2. The seasonal change of the shoreline is affected mainly by the monsoon and the occasional typhoon event.

碩士
國立成功大學
地球科學系專班
95
There are several factors causing land subsidence, including the uneven distribution of water pumping. The rapid development of aquaculture industry in the coastal areas of Taiwan has also resulted in ground subsidence due to over pumping of ground-water. Precise leveling is a traditional technique of height difference measurement. The way of precise leveling is taking by each station forwards step by step, the adjustment result of leveling network is then corrected by reducing the systematic error of observations. The major themes of this research are analyzing the 2003-2006 leveling observations in the western coastal area. Results indicate 1-6 cm subsidence every year, and land subsidence has become a serious problem in the Yun-Lin and Chia-yi areas. Some areas in Yun-Lin and Chia-yi will below the sea level after 30-40 year.

The ocean circulation along the Eastern Great Australian Bight (EGAB) is investigated using models and observations, with a focus on Australia’s strongest upwelling region — the Bonney Coast (BC). A detailed analysis of the shelf circulation in this region has never been fully undertaken. The modelling studies examine how variations in shelf topography and Coastal Trapped Waves (CTWs) influence upwelling. The observations describe one of the most extreme upwelling seasons on record (Austral summer, 2016) with unprecedented coverage. The context for the intense observing program is provided by a detailed analysis of large-scale and local factors, quantifying their impacts. The model used is a regional configuration that includes idealised forcing and initial conditions, and realistic topography and coastal geometry. A key finding from the modelling studies is the demonstration of the influence of alongshore variations in shelf topography - submerged headlands and valleys - on the upwelling circulation. This was the first demonstration of this phenomenon in the BC region. Upwelling is shown to be qualitatively consistent with vorticity dynamics. We show that alongshore baroclinic pressure gradients force a geostrophic onshore flow on the equatorward side of the submerged headlands. A second study also highlights the role of CTWs that act to shut-down the interior upwelling, with the strongest influence nearer the CTW source. The circulation driven by a periodic CTW is also studied as a proxy for wind-driven motions in the western Bight. The results show the mean characteristics of the flow and its adjustment to variable shelf-width and topography, with equatorward (poleward) alongshore velocities of the CTW driving intensified bottom upwelling (downwelling). As the remote forcing frequencies reduce (longer time-scales), local topography rectification and resonance with local winds clearly enhance upwelling in the main EGAB upwelling regions. The observational coverage of the EGAB during Austral summer 2016 was unprecedented, with observations from gliders, moorings, coastal radar, tide gauges, and satellite measurements. The analysis exploited climate indices and reanalysis products to understand the broad scale context of the regional observations. Several factors made the EGAB pre-conditioned to extreme upwelling in 2016. Through the coastal wave guide, the 2015/16 El-Niño uplifted the isotherms over the slope, the South Australian Current was weaker than normal, and the Southern Annular Mode acted to enhance the upwelling favourable winds. Together, these factors meant that the shelf waters responded quickly and efficiently to strong wind-driven events in early 2016. The anomalies associated with this extreme upwelling season included surface temperatures exceeding 2C below average, winds in excess of 0.1Pa, and high Chlorophyll-A. Glider observations show that the upwelled waters were highly skewed (cold and fresh), with origins deeper than 350m (with Flinders Current origin), and with alongshore variations consistent with those implied by the modelling studies. The analysis of climate indices showed significant lagged relationships between large-scale conditions and properties of the shelf circulation in the EGAB. We speculate that these lagged relationships could be used as a predictive tool, to identify when the EGAB is more prone to upwelling. Arguably, the results presented in this thesis represent the most comprehensive description of the shelf circulation in the EGAB. We show, for the first time, the importance of alongshore variations in topography, the impacts of CTWs, and the role of remote forcing on the shelf circulation. This research addresses some important knowledge-gaps of the oceanography of this region, and are particularly important for the management of fisheries and prediction of the EGAB upwelling system as a whole.

Mountain goats (Oreamnos americanus) in coastal British Columbia and Alaska use lower elevation forests during winter relative to other seasons. Although conventional radiotelemetry is one potential method for studying coastal goats, signal reflection, reliance on clear weather for relocations, and potential harassment of goats during critical winter or kidding periods, all present shortcomings. Global Positioning System (GPS) wildlife collars offer a potential solution to these problems, yet introduce other problems. Some of the most challenging environments for acquisition of GPS fixes, namely incised, heavily forested valleys, are typical within coastal goat habitat. Even in less demanding environments, observation bias exists. Although habitat researchers are aware of this bias, the problem may be underestimated within particular environments. I collared 4 mountain goats within the Stafford River Valley on the mainland coast of B. C. to test GPS wildlife collar performance in challenging terrain and to examine the consequences of GPS observation bias for habitat-selection studies. I also tested the repeated fix success of similar collars placed at sites that differed in forest canopy and topographical relief. After leaving these stationary collars to attempt fix locations over a 24-h period, I determined the percentages of fixes in 2D, 3D and unsuccessful fix classes. I combined digital elevation models with a Geographic Information System (GIS) script to quantify available windows of satellite "sky" that were accessible from each test location. This "window" index, combined with surveyed and digitised habitat variables, allowed me to parameterise multiple regression equations that successfully predict the likelihood of receiving a GPS fix of various fix classes at a given location. From these ground truthing equations and spatially-explicit GIS projections of fix likelihood, I determined the likelihood of obtaining a GPS fix within any portion of the Stafford River study area. I was therefore able to match each individual goat's locations directly to a GPS fix probability. A significant correlation between mean predicted fix likelihood and observed seasonal fix success of collared animals was observed. I then applied a simple and conservative correction factor to each fix location before conducting a habitat selection analysis. Analyses of corrected and uncorrected data show that the consequence of failing to correct 3D data for observation bias can be severe. My analyses of uncorrected data indicate significant selectivity for habitats that differ from those which mountain goats are actually selecting.

碩士
國立臺灣海洋大學
海洋環境資訊學系
94
Tanshui River mouth is important for coastal defense purpose in north of Taiwan. The sea condition over there is of high concern to the ROC Coast Guard. The in situ observation in real time at sea is not quite straightforward, encouraging the application of coastal radar remote sens-ing for currents and waves. However, its results ought to be examined by various surveys at sea, providing an opportunity to study the interaction of current field and hydrographic field. The coastal remote sensing is done by the Wavex radar system. The surface currents are tracked by GPS drifters, while the subsurface currents below 2.5 m depth are scanned by the Acoustic Doppler Current Profiler (ADP). The time series of hydro-graphic variation are derived by CTD casts. A temperature and pressure recorder (TD) is used to get tide and waves information. The results show that, due to the coastal southwest flood current, the surface currents at the river mouth rotate counterclockwise and reduce speeds gradually to enter the river channel with a cyclonic moving track. On June 13 of 2006, the temperature of river water was lower than that of sea water outside the river mouth, constructing the vertical hydrographic structure with surface water of low temperature and low salinity. The temperature difference between surface and bottom waters reaches 3℃ and 10 ppt for salinity. At high tide, such stratification disappears with a similar temperature and salinity all over the water column. In ebb tide, sea water entered during flood tide and river water discharge together to strengthen the westward flow up to a speed of 4 knots. The hydrographic stratification appears again. Af-fected by the coastal northeast ebb current, the strengthening outflow of the river rotates counterclockwise continuously, but with an anti-cyclonic moving track instead. The 2.5 m subsurface current scanned crossing the river mouth indicate that the northern half of the mouth is the main drain-age of the river and the current is about the same as of the surface. The results of coastal radar measurement are not quite comparable, requiring further investigation.

Larissa developed an algorithm to enable water-quality assessment within the Great Barrier Reef (GBR) using weather satellite observations collected every 10 minutes. This unprecedented temporal resolution records the dynamic nature of water quality fluctuations for the entire GBR, with applications for improved monitoring and management.