Cyclonic oceanic vortices (eddies) ranging from ~10 to 150km in diameter that travel along the Florida Keys are investigated. This study employs hydrodynamic parameters from simulations in a high-resolution (~900m horizontally), three-dimensional (26 vertical levels) HYbrid Coordinates Ocean Model regional application to study coastal to offshore interactions along the Florida Keys. These parameters are compared qualitatively to observations from Chlorophyll-a Satellite (SEAWiFs) and HF Radar (WERA). Further, eddy characteristics along the Florida Keys are determined using the Okubo-Weiss parameter combined with Sea-Surface Height fields for the period 2004- 2008. Additionally, their temporal scales are assessed using spectral time-series analysis via Welch?s Fast Fourier Transform and Wavelet Transforms. Some processes that influence eddy evolution along the Florida Keys are presented in the form of case studies. And finally, the relative contribution of mesoscale and submesoscale eddies to the upwelling along the Florida Keys is assessed, supporting the argument that these features contribute to produce water exchanges between the offshore flow and the coastal areas.

River plumes often develop in complex environments, where variable coastal and bottom topography, ambient currents, winds and tides may play important roles in shaping the plume evolution. When all these factors are present, the plume dynamics may become intricate and unclear. The objective of this study is to understand the processes controlling the dynamics of a large river plume that is affected by strong boundary currents, variable winds and complex topography. The Mississippi River (MR) plume is the study case of this dissertation work, and focus is given to the interactions between the plume and the offshore circulation of the Gulf of Mexico (GoM). A series of numerical experiments was designed to investigate the impact of different factors on the development of a large scale river plume in scenarios with variable degrees of complexity. First, a box-like model with an idealized estuary was designed to address the general development of a mid-latitude river plume and assess the variability of the plume with changes in the outflow conditions at the river mouth. The structure and development of the plume in the flat-bottom, receiving basin was highly dependent on the degree of freshwater mixing at the source. Larger freshwater mixing enhanced the estuarine gravitational circulation and modified the dynamical balance at the estuary mouth. Those changes effectively modified the shape of the bulge and length/transport scales of the coastal current. Sloping-bottom conditions further modified the development of the plume. Secondly, a Northern GoM model was designed and numerical experiments were conducted to investigate the specific dynamics of the MR plume, in the presence of both shelf and basin-wide circulation. In particular, buoyancy-driven (due to the MR and all other major Northern GoM rivers) and wind-driven currents were studied on the shelf, while the extension of the Loop Current and associated frontal eddies were considered as major factors in the shelf to offshore interactions; wind-driven, shelfbreak eddies were also considered. Process-oriented experiments demonstrate that westerly and southerly winds promoted the development of a surface Ekman layer that enhances the offshore advection of plume waters. The steep topography in the vicinity of the MR Delta was a favorable condition for that process. When the MR plume was subject to a full-blown scenario (realistically-forced experiment nested within a large-scale model), complex interactions between wind-driven and eddy-driven dynamics determined the fate of the plume waters. Offshore removal is a frequent plume pathway, and the offshore transport can be as large as the wind-driven shelf transport. The offshore pathways depend on the position of the eddies near the shelf edge, their life span and the formation of eddy pairs that generate coherent cross-shelf flows. Strong eddy-plume interactions were observed when the Loop Current (LC) system impinged against the shelfbreak, causing the formation of coherent, narrow low-salinity bands that extended toward the Gulf interior. The offshore transport of MR water is a year-round process, but the interactions between the MR plume and the LC system have large inter-annual variability. Plume to LC interactions are determined by episodic northward intrusions of the LC system in the NGoM. The interactions are dictated by the proximity of the LC system to the MR Delta and by wind effects. On average, plume to LC interactions correspond to ~ 12 % of the year-round, total freshwater transport near the MR Delta, but this percentage can go up to 30 % in individual years. At the time of the plume to LC interactions, an average value of LC freshwater entrainment was estimated to be ~ 4,150 m3 s-1. The findings presented here are a major contribution toward the understanding of the cross-marginal and basin-wide transport of MR waters by a large-scale current system, and the connectivity to remote regions, such as the South Florida region and the Florida Keys.

Ocean models are increasingly able to synthesize a large temporal domain with fine spatial resolution. With this increase in functionality and availability, ocean models are in high demand by researchers, establishing a critical need for validating a model’s ability to represent interior ocean dynamics. Satellite measurements are typically used for validation, however these measurements are limited to the upper layers of the ocean and therefore satellite measurements of sea surface height and sea surface temperature are the most validated output parameters of three-dimensional ocean models. Unfortunately there is a paucity of model validation studies for the interior ocean. This study fills a knowledge gap by contrasting model data from the Hybrid Coordinate Ocean Model (HYCOM) for the interior ocean in the Tongue of the Ocean (TOTO), Bahamas and the Gulf of Mexico (GoM) against observational (i.e., in situ) data collected in both locations. Conductivity temperature and depth (CTD) data in the GoM were collected during five research cruises by the DEEPEND Consortium between May of 2015 and May 2017. These data were collected as part of the investigation into the impact of oil spills on faunal communities in deep water of the GoM. CTD and expendable CTD (XCTD) data in the TOTO were collected by the Naval Undersea Warfare Center (NUWC) detachment Atlantic Undersea Test and Evaluation Center (AUTEC) in support of U.S. Navy acoustic testing between 1997 and 2017 to characterize the sound velocity profile of the water column. The global 1/12° HYCOM configuration (GLBu0.08) was found to be a better fit in the upper 400 and 250 meters of the TOTO for temperature and salinity, respectively, than the GoM 1/25° HYCOM configuration (GOMI0.04 1/25°) fit the GoM in situ data for the same depths. The GoM 1/25° HYCOM configuration (GOMI0.04 1/25°) provided a better fit in the GoM for depths of 500 and 300 meters and deeper for temperature and salinity, respectively, than the global 1/12° HYCOM configuration (GLBu0.08) fit the TOTO in situ data at the same depths. A comprehensive comparison of the vertical profile between the model and observational data for each of the regions of interest provides insight into using HYCOM forecast data for future applications.

Le dimensionnement préliminaire d’un propulseur hybride passe par une phase d’essais à échelle réduite afin de caractériser entre autre la loi de régression du couple oxydant/combustible envisagé pour remplir les besoins de la mission en terme de performances, durée de fonctionnement, etc. Afin de limiter le recours à ces campagnes expérimentales onéreuses et génératrices de délais pour les industriels, il est nécessaire de développer des outils numériques fiables permettant de prévoir rapidement, sous différentes conditions de fonctionnement et géométries de chambre de combustion, la loi de régression d’un couple oxydant/combustible. L’objectif de cette thèse est de proposer une modélisation monodimensionnelle du mécanisme de régression des combustibles liquéfiables. Cette classe de combustibles offre des vitesses de régression trois à cinq fois plus élevées que celles rencontrées avec les combustibles généralement utilisés en propulsion hybride (PBHT par exemple). Ce modèle se base alors sur le transport de la phase gazeuse et du film liquide se développant sur le combustible solide, la vitesse de régression dépendant des transferts de masse et d’énergie entre ces trois phases. Afin de valider cette approche et l’architecture du code Hydres conçu pour la résolution de ce modèle et la prévision des performances propulsives d’un moteur hybride, des campagnes expérimentales ont été réalisées sur les bancs d’essais Hycarre et Hycom. Ces essais ont également permis de développer une technique de mesure permettant l’obtention de la vitesse de régression instantanée du combustible, conduisant à la restitution de la loi de régression instantanée du couple oxydant/combustible. / The preliminary design of a hybrid rocket engine requires lab-scale tests to characterize the regression law of the oxidizer/fuel pair intended to fulfil the mission needs in terms of performances, etc. To limit these costly and potentialy delaying experimental campaigns, it is necessary to develop reliable numerical tools to quickly predict the regression law of the oxidiser/fuel pair under different operating conditions and with different combustion chamber geometries. The objective of the thesis is to develop a one-dimensional model of the regression mechanism of liquefying fuels. These particular fuels offer regression rates three to five times higher than those found with classic polymers used in hybrid propulsion (eg. HTPB). The model is based on the transportof the gaseous flow and the liquid film which is developing along the solid fuel grain. The regression rate depends on mass and energy transfers between these three phases. To validate this approach and the Hydres numerical tool, specifically designed to solve this model and forecast the performances of a hybrid engine, experimental tests were performed with the Hycarre and Hycom facilities. These tests also allowed for the development of a technique to measure the instantaneous regression rate of the solid fuel, providing directly the instantaneous regression law of the oxidizer/fuel pair.

The Florida Keys National Marine Sanctuary (FKNMS) encompasses North America's only living coral barrier reef and the third longest barrier reef in the world, making it a unique national treasure of international notoriety (FKNMS, 2005). Recent evidence of environmental decline within the sanctuary has created a sense of urgency to understand and protect the valuable resources within. This thesis contributed to the understanding of habitat connectivity to aid managers and decision makers in the creation of additional Marine Protected Areas (MPAs) in the FKNMS to help prevent further environmental decline. This research specifically focused on modeling larval transport and larval connectivity among Acropora palmata (Lamarck, 1816) populations, coral habitats and MPAs in the upper and middle FKNMS. The transport of larvae in relation to ocean currents is a very limited area of research, and the analytic modeling results may serve as powerful guides to decisions about the relative importance of individual coral habitats and MPAs in the study area.Larval transport was modeled with ArcGIS and TauDEM using SoFLA-HYCOM simulated ocean currents during the A. palmata spawning season. This model allowed for the assessment of coral habitat and A. palmata population larval connectivity. The dependence of three distant A. palmata test populations on other upstream coral habitats and A. palmata populations significantly differed (Kruskal-Wallis test, P less than 0.0001). The clonally diverse Sand Island Reef A. palmata population's larval connectivity was significantly higher compared to other distant monoclonal populations (Mann-Whitney test, P less than 0.0001). Compared to the clonal structure of each test population determined by Baums, Miller, and Hellberg (2006), results indicated simulated larval connectivity may be a determinant of A. palmata population clonal diversity.By modeling MPA and coral habitat connectivity, this study also identified unprotected and distant coral habitat areas with the greatest downstream influence on MPAs; these may serve as potential coral larvae sources. It is recommended that establishing these areas as no-take MPAs would improve overall coral habitat and MPA network connectivity.