Low-frequency ambient noise characteristics and budget in the South China Sea basin

A hydrophone was moored at mid depth in the South China Sea basin from November 2005 to October 2006. Operated with a 1‐min‐on and 14‐min‐off duty cycle and sampled at 1.6 kHz, the measured time series captures the spectral characteristics and variability of the ambient noise in the 0–800‐Hz band over an annual cycle. In this paper, we provide a description on the daily, monthly, and seasonal variabilities and variances in the measured noise spectrum and band levels. In order to gain insights into the predictability of the ambient noise field in this marginal sea, the interpretation of the data is facilitated with historical shipping density data and nowcast wind fields from the Navy Operational Global Atmospheric Prediction System (NOGAPS). Attention is made to the evolution of the ambient noise spectra during major storm events. Intermittent noises are also examined. The potential sources for these intermittent noises are discussed. [Research sponsored by the Office of Naval Research.]

: Matsoukas et al. [2007] present a monthly analysis of heat fluxes in relation to heat budget in the Red and Black Seas to provide further insight for air-sea exchange processes in the small ocean basins. Components of net surface heat flux are illustrated during 1984-1995. In computing latent and sensible heat fluxes, Matsoukas et al. [2007] apply traditional bulk formulations. A heat balance method that is based on the available energy for evaporation flux is also presented to compare latent heat fluxes with those from the bulk formulations. All near-surface atmospheric variables, including wind speed at 10 m, used in the heat balance method are obtained from reanalysis of a numerical weather product (NWP). Initial input data for radiation flux calculations are at resolutions of 1.0-degrees and 2-degrees, depending on the availability. Monthly means of heat budget components are computed on the basis of monthly means of atmospheric variables during 1984-2000.

Particle size shapes prokaryotic communities and vertical connectivity in the water columns of the slope and central basin of the South China Sea

The South China Sea (SCS) is one of the largest marginal seas in the world, and the air-sea CO 2 flux in the SCS may contribute significantly to the global air-sea CO 2 flux. In the past decade, many researches on the aquatic p CO 2 and air-sea CO 2 flux mainly in the north SCS were carried out based on the underway measurement of the p CO 2 , and the results revealed that the SCS is a source of the CO 2 as a whole in the annual scale. However, the air-sea CO 2 flux is high spatial variability in the SCS, for example, the north shelf of the SCS is a CO 2 sink while the basin is a source. To monitor the spatial and temporal variations of the air-sea CO 2 flux in the SCS, few satellite remote sensing algorithms have been developed to estimate the aquatic p CO 2 in the north SCS. However, these algorithms are all the empirical models which depend on the training dataset from the in situ measurement. In this study, we apply the semi-analytical algorithm MeSAA to retrieve the aquatic p CO 2 in the SCS basin. The MeSAA algorithm was proposed by the Bai et al. (2016) and was evidenced to be widely applicable to the different marginal seas including the East China Sea and Bering Sea. Based on the underway measured aquatic p CO 2 and water temperature, we found that the variation of the p CO 2 in the SCS basin is mainly controlled by the temperature. In addition, the increase of the atmosphere p CO 2 can also contribute the systematical increase of the aquatic p CO 2 . Therefore, we established a semi-analytical algorithm for the aquatic p CO 2 retrieval in the SCS basin, which considers the thermodynamic effect and air-sea CO 2 fluxes. The results showed that the thermodynamic effect in the SCS basin was consistent with the theoretical result with the aquatic p CO 2 increasing 4.23% for the 1°C rising of the water temperature. Moreover, the satellite-retrieved aquatic p CO 2 match well with the in situ p CO 2 . Based on the established algorithm, the monthly time-series of the aquatic p CO 2 in the SCS basins from 2003 to 2016 were generated from the MODIS datasets from both the Aqua and Terra satellite, and the long-term trends of the aquatic p CO 2 in the different parts of the SCS basin were analyzed.

Louis O. Quam, highly respected geologist/geographer, academician, and government science administrator, died on 25 July 2001 at age 95. He was best known in the United States and Canada, but widely recognized in several other countries for his many contributions to the advancement of the field of geography, for his influence on expenditure of significant government resources to fund geographic and other research, and for his broad administrative support of research in both the Arctic and the Antarctic. ... He attended public schools in Boulder, Colorado, graduating from high school in 1925, and later attended the University of Colorado there, earning Bachelor of Arts (1931) and Master of Science (1932) degrees in geology. Numerous recognitions acclaimed his achievements in earth sciences and science administration .... he decided to complete his formal education at Clark University in Worcester, Massachusetts. There, holding the Libby Fellowship, he completed requirements for his doctorate in Physical Geography (1938). Next, he returned to the University of Colorado as Assistant Professor of Geography (1938-42). At this point, his promising career was interrupted by a period of service in the United States Navy (1943-46). Honorably discharged from the Navy with the rank of Lieutenant Commander, Quam quickly returned to university life as Associate Professor of Geography at the University of Virginia at Charlottesville (1947-50). ... Several events in the immediate post-war years would dominate Louis' career. These included the founding of the Office of Naval Research (ONR) (1946) and the establishment of its Arctic Research Laboratory (later renamed Naval Arctic Research Laboratory (NARL) at Barrow, Alaska (1947) and then, the most dominating of all, the founding of the U.S. National Science Foundation (NSF) (1950). ... Quam accepted appointment to the ONR as Head, Geography Branch, Earth Sciences Division in 1950 .... In the ONR, Quam was drawn into membership of many committees and panels of other organizations that were related in diverse ways to his fields of responsibility. ... Shortly after his arrival at ONR, the Environmental Sciences Branch, Biological Sciences Division, elected to give up support of its Arctic research program, including NARL in Alaska. ONR management had to determine quickly whether to let the program lapse or to find another administrative entity within the organization willing to take it over. ... The Chief of Naval Research agreed to transfer the program, along with the pertinent budget, and Louis took over (1951). For four years, he was the sole manager of the Arctic Program .... These functions were, of course, additional to his other duties as Head of the Branch. ... Dr. Quam would have been pleased to know that some specific instances of his distinguished accomplishments are recorded here, not to be forgotten. ... In the opinion of the author, Quam's greatest single policy decision on behalf of Arctic research was his action to operate NARL as a Navy-funded laboratory, and also to recognize it as a national asset that should be made available for the use of others besides the ONR contractors or subcontractors (e.g., AINA [Arctic Institute of North America] under the terms of the ONR contract) for whom it existed. ... By 1967, Quam had enjoyed major successes in the field of Arctic research. At age 61, he was capable of further challenges, and a notable challenge was at hand: the NSF offered him the prestigious position of Chief Scientist of its Office of Antarctic Programs. ... Louis accepted the offer and served two years in the Chief Scientist position (1967-69). At this point, the office was renamed in recognition of its total responsibilities, becoming the Office of Polar Programs. Louis was designated Acting Head of the office, a position he held for two years (1969-71); he then served as Chief Scientist for two more years, until his retirement in 1972. ... He was a good and decent man, whether at home or in the office, and he will be affectionately remembered and missed by all who knew him.

The response of marginal (peripheral) seas to ocean acidification on short and long time scales is not well established. Through modeling, we examine the future acidification of two adjacent marginal seas, the South China Sea (SCS) and the Japan/East Sea (J/ES). Our results illustrate the importance of unique features in determining their acidification. The J/ES basin will become completely undersaturated with regard to calcite rapidly in the next few decades, while the SCS basin will experience relatively slower acidification. During its acidification, the J/ES will continually act as a sink for atmospheric CO2, whereas the SCS will temporarily switch from a source to a sink during the peak pCO2 interval, only to return slowly to being a source again. Marginal sea acidification will be determined by multiple factors, including their connections with the open ocean and their unique physical and biogeochemical dynamics, in addition to the level of atmospheric CO2.

The coupled ocean and acoustic variability in the Northeastern South China Sea basin was monitored using moored oceanographic and acoustic sensors during the 2005‐2006 Windy Island Soliton Experiment (WISE). The temperature and current records captured prominent ocean variability at multiple scales, induced by mesoscale eddies, internal tides, and large amplitude internal waves. The latter two were transbasin, propagating from near the Luzon Strait, through the deep basin, onto the northeastern shelf. The concurrent acoustic measurements were attained from the transmission of a 400 Hz, phase‐modulated signal along a 166 km path every 15 min. The receptions were processed to give the arrival structure of a pulse and its temporal change over a nine‐month period. The observed temporal variability in the statistics of the acoustic travel time and intensity were analyzed using time‐series techniques and models with emphasis to elucidate the connection and sensitivity to the observed ocean variability. Results from the analysis are discussed, as they pertain to the ocean processes and those parameters that can potentially be inferred from these types of acoustic transmissions. [The research is sponsored by the Office of Naval Research.]

In support of The Observing-system Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC) and the Office of Naval Research (ONR) Tropical Cyclone Structure-08 (TCS-08) experiments, a variety of real-time products were produced at the Naval Research Laboratory during the field campaign that took place from August through early October 2008. In support of the targeted observing objective, large-scale targeting guidance was produced twice daily using singular vectors (SVs) from the Navy Operational Global Atmospheric Prediction System (NOGAPS). For mesoscale models, TC forecasts were produced using a new version of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) developed specifically for tropical cyclone prediction (COAMPS-TC). In addition to the COAMPSTC forecasts, mesoscale targeted observing products were produced using the COAMPS forecast and adjoint system twice daily, centered on storms of interest.

As part of The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC) and the Office of Naval Research’s (ONR’s) Tropical Cyclone Structure-08 (TCS-08) experiments, a variety of real-time products were produced at the Naval Research Laboratory during the field campaign that took place from August through early October 2008. In support of the targeted observing objective, large-scale targeting guidance was produced twice daily using singular vectors (SVs) from the Navy Operational Global Atmospheric Prediction System (NOGAPS). These SVs were optimized for fixed regions centered over Guam, Taiwan, Japan, and two regions over the North Pacific east of Japan. During high-interest periods, flow-dependent SVs were also produced. In addition, global ensemble forecasts were produced and were useful for examining the potential downstream impacts of extratropical transitions. For mesoscale models, TC forecasts were produced using a new version of the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) developed specifically for tropical cyclone prediction (COAMPS-TC). In addition to the COAMPS-TC forecasts, mesoscale targeted observing products were produced using the COAMPS forecast and adjoint system twice daily, centered on storms of interest, at a 40-km horizontal resolution. These products were produced with 24-, 36-, and 48-h lead times. The nonhydrostatic adjoint system used during T-PARC/TCS-08 contains an exact adjoint to the explicit microphysics. An adaptive response function region was used to target favorable areas for tropical cyclone formation and development. Results indicate that forecasts of tropical cyclones in the western Pacific are very sensitive to the initial state.

The US Navy's interest in superconductivity began shortly after World War II when programs at the Naval Research Laboratory (NRL) and the Office of Naval Research (ONR) began exploring the science of superconducting materials. Throughout the 1950's and 1960's these programs discovered new superconducting materials and added much to the basic understanding of the phenomenon. Technology development programs began in the late 1960's with major efforts at ONR, NRL, and the Navy's Warfare Centers. Development of superconducting quantum interference devices (SQUIDs) used to detect underwater mines and submarines began at the Warfare Center in Panama City, FL in 1969. At the same time scientists and engineers at the Warfare Center in Annapolis, MD began their own technology efforts to develop quiet, high power density ship propulsion motors. ONR and NRL expanded their programs to include superconducting electronics as well as efforts to develop technologically useful materials (films and wires) for the Navy's technology programs. The Navy's superconductivity efforts accelerated rapidly after the discovery of high temperature superconducting (HTS) materials. A major effort led by NRL developed and launched HTS electronic devices and subsystems into space. The Navy Warfare Center in San Diego and ONR/NRL began programs developing low loss filters for electronic communications as well as the development of fast, low power superconducting digital devices. Navy scientists led industrial programs for development of full scale HTS ship propulsion motors and HTS filters for communication systems. As the 21st century began, the Navy started to develop superconducting systems for fleet implementation. The first ship to use a superconducting system was the USS Higgins that used superconducting cables in a degaussing system (2008).

       Bathymetry of marginal sea basins is commonly deeper than the half-space cooling prediction for large oceans, but what controls this pattern is poorly understood. Here, based on abundant seismic sections with increasingly available databases, we perform an enhanced approach that specifically corrects for post-spreading cooling to reassess thermal subsidence across the Southwest Subbasin (SWSB) and the broader South China Sea (SCS) basin. We attribute the current excessive subsidence of the SCS basin primarily as a response to the post-spreading cooling process, which has global applicability to other marginal sea basins and accounts for at least 86% of the observed depth anomaly. Additionally, the mode of magma supply during seafloor spreading plays a crucial role in shaping reconstructed shallower bathymetry of the SCS basin relative to predictions from the half-space cooling model. A stronger magma supply deriving from the regional subduction system can explain the relatively shallow depth developed during the opening of the SCS compared to large oceans. In contrast, a westward decayed magma supply, driven by localized rift propagation induced by the inherited pre-Cenozoic heterogeneous lithospheric structure of South China, attributes to subsidence discrepancies among sub-basins and within the SWSB.        The sediment-corrected depth of most marginal seas is, on average, more than 500 m deeper than that of large oceans, with maximum anomalies ranging from -0.95 to -2.70 km (in 0.5° bins). The sediment-corrected depths exhibit statistically poor correlations with the spreading rate, indicating that the thermal evolution of marginal seas is not primarily controlled by the spreading rate, unlike large oceans. Neither can this anomaly be fully explained by dynamic topography driven by large-scale mantle convection or by localized variations in the degrees and patterns of subduction systems, although the latter may be an important factor influencing the bathymetry of still-active marginal seas. We interpret at least 44.5% of these anomalies as a result of long-term post-spreading thermal subsidence in inactive marginal seas, with magmatic processes influencing bathymetry during oceanic plate formation. We propose that the post-spreading secular cooling, together with the variable mode of magma supply and potential dynamic subsidence processes driven by subducting slabs, play pivotal roles in the formation of the topographic anomalies within the oceanic basins of marginal seas.

Deep water ambient sound level increases have been documented in the eastern North Pacific Ocean over the past 60 years. It remains unclear whether this increasing trend is observed in other regions of the world. In this work, data from the Comprehensive Nuclear Test Ban Treaty Organization International Monitoring System (CTBTO IMS) were used to examine the rate and direction of low frequency sound level change over the past decade in the Indian, South Atlantic, and Equatorial Pacific Oceans. The sources contributing to the overall sound level patterns differed between the regions. The dominant source observed in the South Atlantic was sound from seismic air gun surveys, while shipping and biologic sources contributed more to the acoustic environment at the Equatorial Pacific location. Unlike the increasing trend observed in the NE Pacific, sound levels over the past 5–6 years in the Equatorial Pacific were decreasing. Decreases were also observed for specific sound level parameters and frequency bands in the South Atlantic Ocean. Based on these observations, it does not appear that low frequency sound levels are increasing in all regions of the worlds' oceans. [Work supported by the Office of Naval Research.]

The adjustment of sea surface height (SSH) around the coasts of the Japan/East Sea (JES) and the South China Sea (SCS) basins subjected to extratropical Pacific Oceanic low frequency variability is studied using a Kelvin-planetary wave model and a high resolution numerical model. It is found that the modulation of SSH around the coast of Japan is mainly determined by slow adjustment of planetary waves, which radiate from the west coast of Honshu and Hokkaido due to the coastal Kelvin wave. In contrast, the SSH modulation around the cost of the South China Sea basin is mainly determined by the coastal Kelvin wave, which transfers the anomalous SSH into the SCS via the Luzon Strait and out via the Mindoro Strait. The planetary waves radiating from the west coast of Palawan establish a nearly uniform SSH anomaly in the southern part of the SCS, bounded by an eastward jet at the latitude of the Mindoro Strait. Along the western boundary, SSH anomaly decreases almost linearly toward the south, in accordance with the changing local deformation radius. In these two marginal seas, the mean subtropical Pacific gyre circulation enhances SSH modulation induced by extratropical Pacific low frequency variability. Overall, the SSH adjustment in the JES and the SCS predicted by the analytical model agrees well with the numerical model simulation. Application of this model to interaction between these marginal seas and the open ocean is discussed.

Sources and accumulation of plutonium in a large Western Pacific marginal sea: The South China Sea

Elevated anthropogenic CO2 invasion and stimulated carbonate dissolution in the South China Sea Basin