Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : p. 194-197. / Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 199-205). / In a stratified rotating fluid, frictionally driven circulations couple with the buoyancy field over sloping topography. Analytical and numerical methods are used to quantify the impact of this coupling on the vertical circulation, spindown of geostrophic flows, and the formation of a shelfbreak jet. Over a stratified. slope, linear spindown of a geostrophic along-isobath flow induces cross-isobath Ekman flows. Ekman advection of buoyancy weakens the vertical circulation and slows spindown. Upslope (downslope) Ekman flows tend to inject (remove) potential vorticity into (from) the ocean. Momentum advection and nonlinear buoyancy advection are examined in setting asymmetries in the vertical circulation and the vertical relative vorticity field. During nonlinear homogeneous spindown over a flat bottom, momentum advection weakens Ekman pumping and strengthens Ekman suction, while cyclonic vorticity decays faster than anticyclonic vorticity. During nonlinear stratified spindown over a slope, nonlinear advection of buoyancy enhances the asymmetry in Ekman pumping and suction, whereas anticyclonic vorticity can decay faster than cyclonic vorticity outside of the boundary layers. During the adjustment of a spatially uniform geostrophic current over a shelfbreak, coupling between the Ekman flow and the buoyancy field generates Ekman pumping near the shelfbreak, which leads to the formation of a jet. Scalings are presented for the upwelling strength, the length scale over which it occurs, and the timescale for jet formation. The results are applied to the Middle Atlantic Bight shelfbreak. / by Jessica A. Benthuysen. / Ph.D.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 233-237). / Internal hydraulic jumps in flows with upstream shear are investigated numerically and theoretically. The role of upstream shear has not previously been thoroughly investigated, although it is important in many oceanographic flows such as exchange flows and stratified flow over topography. Several two-layer shock joining theories, characterized by their distribution of dissipation in the jump, are considered and extended to include upstream shear, entrainment, and topography. Theoretical results are also compared to 2D and some 3D numerical simulations of the full Navier-Stokes equations, which allow continuous velocity and density distributions. The solution space of idealized jumps with small upstream shear is identified using two-layer theories, which shows that upstream shear allows larger jumps to form and allows jumps for a larger range of parameters. Numerical simulations reveal several jump structures that can occur in these flows, including an undular bore, a fully turbulent jump, and a smooth front turbulent jump. At low shear, the 2D mixing efficiency is constant across simulations. As shear increases, the basic two-layer theories no longer provide solutions. Numerical simulations show that entrainment becomes significant as the shear increases, and adding entrainment and shape parameters to describe the continuous velocity profiles is required to accurately describe the simulations using two-layered theory. The entrainment depends on the upstream shear and can be predicted with a modified theory. However, use of the theory is limited due to its sensitivity to the value of the shape parameters. The 2D mixing efficiency also decreases significantly as shear increases. Finally, more realistic 2D and some 3D simulations including topography bridge the gap between the highly idealized simulations and the very realistic work of others. Simulations with topography show additional jump types, including a higher mode jump with a wedge of homogeneous, stagnant fluid similar to a structure seen in Knight Inlet. In all cases, numerical simulations are used to identify trends in the mixing and jumps structures that can occur in internal hydraulic jumps. / by Kelly Anne Ogden. / Ph. D.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 163-174). / The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents. First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component. The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC. The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system. / by Isabela Astiz Le Bras. / Ph. D.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 175-180). / This thesis explores the buoyancy-driven circulation in the Red Sea, using a combination of observations, as well as numerical modeling and analytical method. The first part of the thesis investigates the formation mechanism and spreading of Red Sea Overflow Water (RSOW) in the Red Sea. The preconditions required for open-ocean convection, which is suggested to be the formation mechanism of RSOW, are examined. The RSOW is identified and tracked as a layer with minimum potential vorticity and maximum chlorofluorocarbon-12. The pathway of the RSOW is also explored using numerical simulation. If diffusivity is not considered, the production rate of the RSOW is estimated to be 0.63 Sv using Walin's method. By comparing this 0.63 Sv to the actual RSOW transport at the Strait of Bab el Mandeb, it is implied that the vertical diffusivity is about 3.4 x10-5 m 2 s-1. The second part of the thesis studies buoyancy-forced circulation in an idealized Red Sea. Buoyancy-loss driven circulation in marginal seas is usually dominated by cyclonic boundary currents on f-plane, as suggested by previous observations and numerical modeling. This thesis suggests that by including [beta]-effect and buoyancy loss that increases linearly with latitude, the resultant mean Red Sea circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In mid-basin, the northward surface flow crosses from the western boundary to the eastern boundary. The observational support is also reviewed. The mechanism that controls the crossover of boundary currents is further explored using an ad hoc analytical model based on PV dynamics. This ad hoc analytical model successfully predicts the crossover latitude of boundary currents. It suggests that the competition between advection of planetary vorticity and buoyancy-loss related term determines the crossover latitude. The third part of the thesis investigates three mechanisms that might account for eddy generation in the Red Sea, by conducting a series of numerical experiments. The three mechanisms are: i) baroclinic instability; ii) meridional structure of surface buoyancy losses; iii) cross-basin wind fields. / by Ping Zhai. / Ph. D.

No description available.

No description available.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 206-211. / by Alexander N. Shor. / Ph.D.

A dispersão de coliformes termotolerantes, provenientes dos emissários sub- marinos de descarte de esgoto doméstico do Araçá, Itaquanduba e Cigarras no canal de São Sebastião, foi simulada através da modelagem numérica em 9 cenários hidrodinâmicos. O objetivo foi determinar se e quais as áreas que são impactadas pelos emissários. O acoplamento entre o modelo de plumas UM3 (Visual Plumes) e o modelo numérico sECOM foi realizado. Os emissários submarinos foram a única fonte de efluentes contabilizada, empregando-se um decaimento bacteriano. Os resultados do acoplamento foram qualitativamente comparados com dados de enterococos e coliformes termotolerantes da CETESB e da SABESP. As concentrações de coliformes simuladas não excederam o limite da resolução CONAMA 274 (2000), com exceção de junho de 2013 e 2016, indicando que os padrões hidrodinâmicos do canal são suficientes para dispersar o material proveniente dos emissários. As adjacências do emissário do Araçá apresentaram as maiores persistências de coliformes ao longo do tempo. No entanto, as concentrações simuladas não ultrapassaram 1000 NMP/100mL em mais de 0.1% do tempo. No inverno, a persistência e os valores das concentrações de coliformes foram superiores em relação ao verão. O modelo acoplado simulou de forma satisfatória a variabilidade e a dispersão de coliformes termotolerantes na região. / The dispersion of thermotolerant coliforms by the Araçá, Itaquanduba and Cigarras submarine sewage disposals, in the São Sebastião channel, has been studied by 9 hydrodynamic numerical model scenarios. The main goal was to determine if and what areas are impacted by the sewage disposal. The UM3 (Visual Plumes) and the numerical model sECOM were coupled. The only sources of pollution introduced were the submarine discharges, using bacteria decay. The coupled model results were qualitatively compared with Enterococos and thermotolerant coliforms data available by sanitary agencies of the São Paulo state (CETESB and SABESP). The modeled coliform concentration did not exceed the limit stated by CONAMA Resolution 274 (2000), with an exception in June 2013 and 2016. It indicates that the hydrodynamic patterns of the channel are sufficient to disperse the material coming from the submarine disposals. Adjacent areas of Araçá submarine sewage disposal presented the highest persistence of coliform concentrations. However, the simulated concentrations did not exceed 1000 NMP/100mL in more than 0.1 % of the time. In winter, the persistence and values of coliform concentrations were higher in relation to summer. The coupled model simulated satisfactorily the variability and dispersion of coliforms in the region.

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.