Ocean modeling is usually constrained by the lack of observed velocity data for the initial condition. The diagnostic initialization is widely used to generate velocity data as initial condition for ocean modeling. It integrates the model from known temperature (Tc), salinity (Sc) and zero velocity fields and holds (Tc, Sc) unchanged. After a period of the diagnostic run, the velocity field (Vc) is established, and (Tc, Sc, Vc) fields are treated as the initial conditions for the numerical modeling. During the diagnostic initialization period, the heat and salt 'source/sink' terms are generated at each time step. In this Thesis, the Princeton Ocean Model implemented to the South China Sea demonstrated extremely strong thermohaline sources and sinks generated by the diagnostic initialization. Such extremely strong and spatially non - uniform initial heating/cooling (salting/freshening) rates in the ocean model ma y cause drastic change in thermohaline and velocity fields initially (after the diagnostic run). There is a need to overcome such problems or find alternative methods as diagnostic initialization is extensively used. / Republic of Singapore Navy author.

Thesis (M.S. in Applied Mathematics)--Naval Postgraduate School, March 2009. / Thesis Advisor(s): Chiu, Ching-Sang ; Scandrett, Clyde. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Computational Acoustics, South China Sea, Ray Theory, Modeling. Includes bibliographical references (p. 35-36). Also available in print.

Thesis (M.A. in Security Studies)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Gaye Christoffersen, Lyman Miller. Includes bibliographical references (p. 87-94). Also available online.

Two biomarkers, n-alkanes and alkenones, have been studied for the distribution of their relative concentrations spatially and temporally in sediments in the Pearl River Estuary. 59 modern sediments have been collected across the Pearl River Estuary and offshore Hong Kong, covering a wide range of environmental and sedimentary conditions. The relative abundances between long-chain (C27 to C33) terrestrial-derived n-alkanes, and short-chain (C18 to C22) n-alkanes which are ascribed to marine algal and bacterial production, have been analyzed as “terrestrial-to-marine n-alkane ratios”. Results show that this ratio follows a general gradient of increasing towards uplands. More detailed interpretation has revealed that this ratio is highly dependent on the proximity of the sampling site to the supply of terrestrial matters, i.e., to river mouths and lands. This finding provides fundamentals on the development of terrestrial-to-marine n-alkane ratio as a potential new proxy for terrestrial sediment flux. The newly developed potential environmental and climate proxy, the relative abundances of n-alkane compounds, is applied on analysis of a sediment core drilled in coastal marine environment offshore Hong Kong, HKUV11, which can be dated back to c. 11,000 yr BP. Alkenone unsaturation ratios are also analyzed to reconstruct post-Younger Dryas change in sea surface temperature (SST). Records show a rapid warming of the ocean surface at the start of the Holocene epoch from c. 11,000 yr BP to c. 9000 yr BP, during when the SST researched its optimum, followed by a long period of more stabilized temperatures with the presence of some short-term cold events. The terrestrial-to-marine n-alkane ratio matches well not only with the alkenone SST data in this study, but also with the bulk organic carbon geochemical data and grain size analysis of HKUV11. This suggest that the n-alkane ratio is a reliable proxy for terrestrial sediment supply in this coastal and estuarine environment, as supported by both the field studies of its natural distribution across the environmental gradient, and the successful application on an actual sediment core. The Holocene climate variability of coastal south China recovered by the HKUV11 sediment record has been compared with δ18O records from a Dongge Cave stalagmite, a Greenland ice core and the Northern Hemisphere summer insolation variability. Results show that late-Glacial to Holocene climate in coastal South China generally agrees with the trend in the distal high-latitude North Atlantic, suggesting a strong external driving force of global climate change by the NH summer insolation variability. A detailed comparison between the HKUV11 SST record and Dongge Cave Asian monsoon record reveals that the temperature in coastal south China is sensitively correlated to the strength of Asian monsoon. These results have important implications to how monsoonal winds and temperature are coupled together, and can provide insights to how they may interact under future climate change in this densely-populated region. / published_or_final_version / Earth Sciences / Master / Master of Philosophy

Thesis (M.A. in Security Studies)--Naval Postgraduate School, December 2003. / AD-A420 221. Thesis advisor(s): Gaye Christoffersen, Lyman Miller. Includes bibliographical references (p. 87-94). Also available online.

The Asian Seas International Acoustics Experiment (ASIAEX) conducted in April and May of 2001 helped researchers take a major step in understanding the circulation of the northern South China Sea. This region crosses one of the primary sea lanes of communication between Chinese submarine bases and the Pacific theater, therefore making it an extremely valuable source of knowledge for the United States Navy. This thesis provides a qualitative and quantitative analysis of the mesoscale variability in the South China Sea during spring 2001 using observational data from the ASIAEX experiment. An array of moorings (S1-S8) equipped with ADCPs, pressure gauges, temperature and salinity sensors, and current meters, was placed between the southern tip of Taiwan and Dongsha Island (Pratis Reef). Data results show that significant mesoscale features existed in the South China Sea. Mean currents over the continentalshelf were found to be primarily wind driven while flows over the continental slope were forced by the mesoscale features. The South China Sea Warm Current was observed twice over the slope during ASIAEX. A cyclonic meander of the northern gyre propagated onshoreand southwest near S7. Tropical Cyclone Cimaron set up apressure driven flow towards the southwest along the continental shelf, suggesting that a storm this size can influence the circulation in the entire South China Sea. Model results from the Northern South China Sea Nowcast/Forecast System were compared to the observational data. The model gave a good description of the big picture in the South China Sea but was unable to resolve the smaller-scale events. The model was too constrained by topography and had a distinct offset of the alongshore component most likely imposed on by open boundary forcing.

Abstract This study focuses on analyzing depth distributions of d18O and changes in mixed layer thickness in the South China Sea (SCS). The oxygen isotopic compositions of the samples collected were determined using the Epstein-Mayeda (1953). The overall precision of the d18OSMOW measurements is +0.1‰. Our data suggest that depth changes of average d18OSMOW of seawater in the SCS as follows: the average d18OSMOW values for the surface (0-100m) is 0.02‰; subsurface (100-400m) is 0.2‰; intermediate (400-1500m) is ¡V0.03‰ and deep waters (>1500m) is ¡V0.06‰. The effect of monsoon on the mixed layer in the SCS water is evident as the increases in the mixed layer is always coincident with the northeast monsoon in winter. Furthermore, the d18OSMOW values are correlated linearly with the mixed layer thickness. In other words, the lower d18OSMOW values of seawater are, the less the thickness of mixed layer is.

abstract / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 171-191) / Microfiche. / x, 191 leaves, bound ill., maps 29 cm

Thesis (M.A. in National Security Affairs)--Naval Postgraduate School, December 2002. / AD-A411 064. Includes bibliographical references (p. 71-75). Also available online.