The Gascoyne continental shelf is located along the north-central coastline of Western Australia between latitudes 21° and 28°S. This study presents CTD and ADCP data together with concurrent wind and satellite imagery, to provide a description of the summer surface circulation pattern along the continental margin, and the hydrography present in the upper 1km of ocean, between latitudes 21° and 35°S. It also discusses the outcome of a numerical modelling study that examined the physical factors contributing to a bifurcation event persistently observed in satellite imagery at Point Cloates. The region comprises a complex system of four surface water types and current systems. The Leeuwin Current dominated the surface flow, transporting lower salinity, warmer water poleward along the shelf-break, and causing downwelling. Its signature ‘aged’ from a warm (24.7°C), lower salinity (34.6) water in the north to a cooler (21.9°C), more saline (35.2) water in the south, as a result of 2-4Sv geostrophic inflow of offshore waters. The structure and strength of the current altered with changing bottom topographies. The Ningaloo Current flowed along the northernmost inner coast of the Gascoyne shelf, carrying upwelled water and re-circulated Leeuwin Current water from the south. Bifurcation of the Ningaloo Current was seen south of the coastal promontory at Point Cloates. Numerical modelling demonstrated a combination of southerly winds and coastal and bottom topography off Point Cloates to be responsible for the recirculation, and indicated that the strength of southerly winds affect recirculation. Hypersaline Shark Bay outflow influenced shelf waters at the Bay’s mouth and to the south of the Bay. The Capes Current, a wind-driven current from south of the study region was identified as a cooler, more saline water mass flowing northward. Results of the hydrography study show five different water masses present in the upper-ocean. Their orientations were affected by the geopotential gradient driven Leeuwin Current/Undercurrent system at the continental margin. The Leeuwin Undercurrent was found at the shelf-slope, carrying (>252 μM/L) Subantarctic Mode Water at a depth of 400m

D.Litt. et Phil. / Please refer to full text to view abstract

Approved for public release, distribution is unlimited / High Frequency (HF) radar backscatter instruments are being developed and tested in the marine science and defense science communities for their abilities to sense surface parameters remotely in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical for characterizing and forecasting the battle space environment. In this study, the performance of a network of four CODAR (Coastal Ocean Dynamics Application Radar) SeaSonde HF radars, using the Multiple Signal Classification (MUSIC) algorithm for direction finding, is described for the period between July to September 2003. Comparisons are made in Monterey Bay with moored velocity observations, with four radar baseline pairs, and with velocity observations from sixteen drifter deployments. All systems measure ocean surface current and all vector currents are translated into radial current components in the direction of the various radar sites. Measurement depths are 1 m for the HF radar-derived currents, 12 to 20 m for the ADCP bin nearest to the surface at the M1 mooring site, and 8 m for the drifter-derived velocity estimates. Comparisons of HF radar-M1 mooring buoy, HF radar-HF radar (baseline), and HF radar-drifter data yield improvements of - 1.7 to 16.7 cm/s rms differences and -0.03 to 0.35 correlation coefficients when measured antenna patterns are used. The mooring comparisons and the radar-to-radar baseline comparisons indicate angular shifts of 10Ê» to 30Ê» for radial currents produced using ideal antenna patterns and 0Ê» to 15Ê» angular shifts for radial currents produced using measured patterns. The comparisons with drifter-derived radial currents indicate that these angular biases are not constant across all look directions, even though the local antenna pattern distortions were taken into account through the use of measured antenna patterns. In particular, data from the SCRZ and MLNG radar sites show varied pointing errors across the range of angles covered. / Lieutenant Commander, Republic of Korea Navy

Approved for public release; distribution in unlimited. / Moored current meters were used to describe currents over the continental slope off Monterey Bay, California, from March 1998 to March 2003. The water depth at this location was 1800 m and current observations included of 16-88 m, 210- 290 m, 305 m and 1200 m although measurements at 16-88 m were not continuous. Poleward currents dominated the flow between 24 and 305 m. At 305 m the mean flow was 3.9 cm/s toward 334ʻ. Surprisingly, at 1200 m the mean flow reversed and was 0.8 cm/s toward 169ʻ. The principal axis for the flow at 305 m (1200 m) was 349ʻ (350ʻ), the semi-major axis was 9.4 cm/s (5.8 cm/s) and the semi-minor axis 3.4 (2.0 cm/s). The direction of the principal axis and the mean flow at 1200 m was aligned with the bathymetry to the east of the mooring site. The seasonal cycle at 305 m was dominated by an acceleration of the poleward flow from a minimum near zero on April 15 to maximum, 25 cm/s on July 15. This flow resulted in an increase of temperature at 305 m of 1.2ʻC due to geostrophic adjustment and a corresponding 10 cm increase in sea level due to steric effects. The acceleration of alongshore flow was out of phase with the alongshore pressure gradient which was greatest in mid- April. At 1200 m, the temperature increase (0.2ʻC) only lasted from April 15 to June 1 after which equatorward flow increased and temperature decreased. Mesoscale variability dominated the velocity measurements with maximum variance at about 60- day periods. At 305 m, the eddy kinetic energy was greatest (smallest) in October (December), 40 cm2/s2 (4 cm2/s2) while at 1200 m the maximum (minimum) occurred in July (February), 5 cm2/s2 (0.5 cm2/s2). Poleward events were stronger at 305 m while equatorward events were stronger at 1200 m. The three first empirical orthogonal functions explained 90% of the temporal variability of the horizontal currents. The first, second, and third Z-scores represented flow along the principal axis, undercurrent vs. Davidson current, and upwelling modes, respectively. While the seasonal patterns for the first two modes agreed with seasonal variability described above, the seasonal variability of the upwelling mode (6% of the variance) indicated that the waters between 16 and 88 m flowed onshore during the spring and summer upwelling period. / Commander, Mexican Navy

Approved for public release, distribution is unlimited / During the fall of 2002 the physical oceanographic conditions off Central California were monitored by means of CTD casts and VMADCP current measurements during two cruises. The first cruise, included 38 stations and one time series station. The second cruise was sponsored by the Naval Oceanographic Office (NAVOCEANOCEANO) and occupied nine sections along the coast. A total of 86 stations and two time series stations were occupied during the second cruise. CTD calibration and data processing methods are described. The isosteres, current vectors, and salinity distribution from the cruises provide a clear picture of the circulation pattern during the fall 2002. A strong shoreward, anticyclonic meander of the California current was observed. Although the meander itself did not cross the dynamic trough that separated inshore and offshore currents, at the point where the meander was adjacent to the trough, a ridge formed which transported Subarctic waters into the coastal zone. These fresh waters were advected to the north and south along the coast, depending upon the direction of nearshore currents. The observed mesoscale circulation showed the manner in which waters which are upwelled at the coast in summer are replaced by oceanic waters in the fall and winter. Analysis of the geography of the deep sound channel (DSC) during this period showed that the mean pressure of the DSC was at 586 dbar while the mean sound speed minimum was 1480 m/s. The minimum sound speed varied 3 m/s while the pressure of the minimum varied by 330 dbars. The shape of the pycnocline controlled the pressure and depth of the DSC in the region. / Ensign, United States Naval Reserve

Approved for public release, distribution is unlimited / Rip current spacings are compared with wave energetics and directional spreading in the Southern Monterey Bay. Southern Monterey Bay affords a unique environment to study rip currents owing to their prevalence created by near-normally incident waves on a sandy shoreline. It is hypothesized that rip current spacing is a function of wave directional spreading and energy flux, based on the morphodynamic modeling by Reniers et al. 2003. A gradient of wave energy flux exists due to headlands and refraction over Monterey Canyon. Rip currents are shown to occur between cusps in the shoreline, allowing cusp spacing to be a surrogate for rip spacing. Rip current spacing was inferred from beach morphology surveys, LIDAR imagery, and Argus cameras, and found to be O(150m) at Sand City and O(300m) at Marina, separated by 6km . Measured waves during a two month period using wave-rider buoys, show a gradient of across-shore energy flux between Sand City, 2 28000( / ) F Jm x . , and Marina, 2 33000( / ) F Jm x . . The two sites have the same peak directional spreading of energy value, 14 peak ̤= o , and slightly different bulk values for Sand City, 18 bulk ̤= o , and Marina, 20 bulk ̤= o . Therefore, the variations in rip current spacing could not be attributed to directional spreading but appear related to variations in energy flux. / Ensign, United States Naval Reserve

Mangrove trees play a prominent role in coastal tropic and subtropical regions, providing habitat for many organisms and protecting shorelines against storm surges, high winds, erosion, and tsunamis. The motivation of this proposal is to understand the complex interaction of mangrove roots during tidal flow conditions using simplified physical models. In this dissertation, the mangrove roots were modeled with a circular array of cylinders with different porosities and spacing ratios. In addition, we modeled the flexibility of the roots by attaching rigid cylinders to hinge connectors. The models were tested in a water tunnel for a range of Reynolds number from 2200 to 11000. Additionally, we performed 2D flow visualization for different root models in a flowing soap film setup. We measured drag force and the instantanous streamwise velocity downstream of the models. Furthermore, we investigated the fluid dynamics downstream of the models using a 2-D time-resolved particle image velocimetry (PIV), and flow visualization. The result was analyzed to present time-averaged and time-resolved flow parameters including the velocity distribution, vorticity, streamline, Reynolds shear stress and turbulent kinetic energy. We found that the frequency of the vortex shedding increases as the diameter of the small cylinders decreases while the patch diameter is constant, therefore increasing the Strouhal number, St=fD/U By comparing the change of Strouhal numbers with a single solid cylinder, we introduced a new length scale, the “effective diameter”. In addition, the effective diameter of the patch decreases as the porosity increases. In addition, patch drag decreases linearly as the spacing ratio increases. For flexible cylinders, we found that a decrease in stiffness increases both patch drag and the wake deficit behind the patch in a similar fashion as increasing the blockage of the patch. The average drag coefficient decreased with increasing Reynolds number and with increasing porosity. We found that the Reynolds stress (−u′v′) peak is not only shifted in the vortex structure because of shear layer interference, but also the intensity was weakened by increasing the porosity, which causes a weakening of the buckling of vorticity layers leading to a decline in vortex strength as well as increase in wake elongation. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

This study is performed in tandem with numerous experiments performed by the U.S. Navy to characterize the ocean environment in the South Florida region. The research performed in this study includes signal processing steps for isolating ocean phenomena, such as internal waves, in the magnetic field. Raw magnetometer signals, one on shore and one underwater, are processed and removed of common distortions. They are then run through a series of filtering techniques, including frequency domain cancellation (FDC). The results of the filtered magnetic residual are compared to similarly processed Acoustic Doppler Current Profiler (ADCP) data to correlate whether a magnetic signature is caused by ocean phenomena. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Thesis. 1977. Sc.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography : leaves 209-217. / Sc.D.

Thesis. 1977. Ocean E.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ocean E.