Physical Sciences and Mathematics Commons^™

Nitrogen Cycling In The Lower Chesapeake Bay And Mid- And South Atlantic Bight, Yifan Zhu

OES Theses and Dissertations

Nitrogen (N) is central to marine primary production; its availability often limits the capacity and rates of primary productivity in most of the world’s oceans. Contrastingly, estuaries frequently receive anthropogenic N loading, oftentimes resulting in eutrophication, harmful algal blooms (HABs), and substantially degraded water quality. Nutrient variability in both estuaries and oceanic regimes results from meteorological forcing and physical processes, including wind-induced, tidal, and mesoscale mixing and upwelling. In this dissertation, a comprehensive investigation of N variability and cycling and its links to physical-biogeochemical processes was conducted using time-series monitoring approaches, flux estimations, satellite imaging, biogeochemical measurements, and molecular analyses. …

Codar's Surface Flow At The Mouth Of The Chesapeake Bay: Relation To Bay's And Atlantic's Forcing, Shelby Kathryn Henderson

OES Theses and Dissertations

Surface currents in the lower Chesapeake Bay (CB) observed with land-based high-frequency radar antennas, or Coastal Ocean Dynamics Application Radar (CODAR), produce hourly 2D maps of current velocities used for search and rescue, pollution tracking, and fishing operations. This study analyzes the correlations between a 9-year record of surface currents measured by CODAR to coastal sea level, local wind forcing, river discharge into CB, and water transport through the Florida Straits, representing the Gulf Stream’s control on sea level along the U.S. mid-Atlantic coast. The goal of this study is to find ways to use CODAR data to detect and …

Flow Kinematics And Dynamics Of The Gulf Stream From Composite Imagery, Caitlin Patrice Mullen

OES Theses and Dissertations

A unique set of contemporaneous satellite-tracked drifters and five-day composite satellite images of the North Atlantic is studied in order to infer the near-surface flow kinematics and dynamics of the Gulf Stream. Using fractal and spectral analyses, two kinematic models, and a potential vorticity model, detailed comparisons are made between these data sets.

Fractal and spectral analyses show that the data set is not fractal, there is no geographic variability, and there is not a strong fractal scaling link between the drifter trajectories and composite temperature fronts as had been postulated by several investigators. These results indicate considerably more work …

Instability Waves In The Gulf Stream Front And Its Thermocline Layer, Sang-Ki Lee

OES Theses and Dissertations

Linear instability calculations were carried out on a three layer Gulf Stream front model in an attempt to elucidate the interaction of the thermocline layer with surface slopewater shoreward of the front. The basic state is geostrophic balance and constant potential vorticity in the two active layers, but the perturbations are ageostrophic. The flow is found to be unstable to long wave perturbations, the wavelength of the most unstable wave to be of order 10 radii of deformation. The instability is mainly baroclinic, 75-85% of the energy supply to the growing perturbation coming from basic flow potential energy. Calculated wavelengths …

Diapycnal Mixing And Mass Transfer In Western Boundary Currents, Jose Luis Pelegri Llopart

OES Theses and Dissertations

The distribution of nutrient flux in five sections across the Gulf Stream (from the Florida Straits of 35°W) is characterized by an intense core, centered at the depth of the 26.8 σ_t isopycnal surface. This 'Nutrient Stream' transports nutrients of O(10³ kmol s^-1} of nitrate and proportional amounts of other nutrients. Water mass and nutrient balances of nine isopycnal layers reveal significant diapycnal mixing between upper-thermocline and surface waters in the sector of the Stream between the Florida Straits and the Mid-Atlantic Bight. A two-box model of the nutrient-depleted surface layers (σ_t < 26.8) and the nutrient-rich thermocline layers (26.8< σ_t < 27.5) shows upward one-way transfer and two-way exchange, both at a a rate at about 1.m²s …

Nonlinear Solutions To A Two-Layer Quasi-Geostrophic Model Of The Gulf Stream, Eiichi Oka

OES Theses and Dissertations

The Gulf Stream shows a large meander off Cape Hatteras. This is driven by an energy conversion process known as baroclinic instability and observations suggest that nonlinearity is an important part in this process. In order to understand the fundamental role of nonlinearity in baroclinic instability, an inviscid 2-layer quasi-geostrophic model is studied.

The linear solution is obtained by methods of normal mode and Fourier-Laplace transforms. It is found that the set corresponding to the continuous spectrum is null and the set corresponding to the discrete spectrum is complete.

The nonlinear solution is expanded in terms of the complete set …