Physical Sciences and Mathematics Commons^™

In The Margins: Reconsidering The Range And Contribution Of Diazotrophs In Nearshore Environments, Corday R. Selden

OES Theses and Dissertations

Dinitrogen (N₂) fixation enables primary production and, consequently, carbon dioxide drawdown in nitrogen (N) limited marine systems, exerting a powerful influence over the coupled carbon and N cycles. Our understanding of the environmental factors regulating its distribution and magnitude are largely based on the range and sensitivity of one genus, Trichodesmium. However, recent work suggests that the niche preferences of distinct diazotrophic (N₂ fixing) clades differ due to their metabolic and ecological diversity, hampering efforts to close the N budget and model N₂ fixation accurately. Here, I explore the range of N₂ fixation …

Model-Based Analyses Of Nitrogen On The Mid-Atlantic Bight Continental Shelf, Tian Tian

OES Theses and Dissertations

The biogeochemistry of continental shelf systems is an important, but poorly quantified, component of the global cycling of nitrogen and carbon. In this study, simulations obtained from a one-dimensional (ID) biogeochemical model developed for the Middle Atlantic Bight (MAB) portion of the U.S. eastern continental shelf were analyzed to investigate nitrogen cycling processes. The 1D model included lower trophic level interactions and was forced by advective fields obtained from a corresponding three-dimensional biogeochemical model. Taylor and target diagram analyses, which compared in situ measurements of sea surface temperature (SST) and salinity, and chlorophyll and particulate organic carbon (POC) derived from …

The Effect Of Submarine Canyon Width And Stratification On Coastal Circulation And Across Shelf Exchange, Kyung-Hoon Hyun

OES Theses and Dissertations

A 3-D ocean circulation model is used to investigate the effect of the width of a submarine canyon and stratification on adjacent coastal circulation and across shelf exchange. Upwelling winds for 20 d drive circulation over six canyons of varying widths (8–60 km), two escarpments to represent infinitely wide canyons, and a generic shelf-slope without a canyon. Also six stratifications whose first internal Rossby radii (a) range over 2–18 km were applied to two canyons (20 and 40 km) to see the effect of stratification. All simulations adjust to the canyon after 5 days spinup and reach an …

Inner Shelf Circulation In Coastal Virginia: A Data Assimilation Approach, Hector Hito Sepulveda

OES Theses and Dissertations

The primary objective of this dissertation is to describe the tidal and subtidal flow patterns over the inner shelf of the Delmarva Peninsula, located in the Mid-Atlantic Bight of the United States (36.6–38.0 N), north of the Chesapeake Bay. The objective is pursued with a combination of direct measurements and numerical assimilative techniques. The dynamic balance of the study area is little known, and the distribution of tidal properties has not been described for this area since very rough descriptions in the 1950's. Hydrographic and current velocity profiles from four regional cruises in the inner shelf were used to study …

Dynamical Sedimentary Models Of Shallow Marine Environments, Yong Zhang

OES Theses and Dissertations

This treatise represents a contribution of quantitative, dynamical sedimentary modeling to the analytical understanding of sedimentary processes in shallow marine environments. The dynamical sedimentary models in this treatise numerically simulate the sedimentary processes from an event time scale, based on the fundamental physics of sediment dynamics in coastal and shelf depositional environments, to a longer, facies time scale. The simulated geologic processes serve to the illustrate shoreface equilibrium profile, shelf storm bed generation, and the shelf sedimentary facies system.

This treatise presents a nearshore profile evolution model for the abandoned Huanghe Delta, a two-dimensional storm deposition model, and a sedimentary …

Modeling Plankton Community Structure Under Environmental Forcing On The Southeastern United States Continental Shelf, Andrew Glenn Edward Haskell

OES Theses and Dissertations

A system of coupled ordinary differential equations was developed to investigate the time-dependent behavior of phytoplankton, copepod, and doliolid populations associated with upwelling features on the outer southeastern U.S. continental shelf. Model equations describe the interactions of nitrate, ammonium, two phytoplankton size fractions, five copepod developmental stages, doliolids, and a detrital pool. Model dynamics are based primarily upon data obtained from field and laboratory experiments made for southeastern U.S. continental shelf plankton populations. Numerous simulations were performed to investigate the effects of environmental variability on the temporal distribution of the structure of resident plankton populations. Variations on a reference simulation, …

The Response Of An Idealized Continental Shelf To Atmospheric Forcing, Paul Francis Moersdorf

OES Theses and Dissertations

The response of continental shelf water to cooling and wind stress is investigated using a two-dimensional numerical model. The topography of the east coast continental shelf was idealized by connecting a shallow (50 m) rectangular nearshore basin to a deeper (100 m) rectangular offshore basin. Numerous cases were examined using a wide range of values for both the air•sea temperature difference and the Wind speed, although the direction of the wind was always perpendicular to the coast.

The model predicts large excursions of shelf water offshore, and the subsequent surfacing of lower waters. Upwelling velocities of close to five meters …

Grain Size Reconnaissance Of The Virginia-North Carolina Inner Shelf Analysis By Settling Technique, Robert Bailey Sanford Jr.

OES Theses and Dissertations

The 2-fold purpose of this study is to calibrate a Rapid Sediment Analyzer and to use it to aid in the determination of the genesis of sediment on the inner continental shelf between Cape Henry and Cape Hatteras. Rapid Sediment Analyzer calibration was conducted by comparison of sieving and settling results of similar sands.

The study area was divided into sediment provinces by both a qualitative procedure (grain size and topography) and a quantitatively procedure (factor-vector analysis). Qualitative provinces are beach and surf, upper shore face, lower shore face, sea floor, and terminal shoals. The berm fines from each terminal …