The distributions of estuarine colored dissolved organic matter (CDOM) are the combined results of physical-biogeochemical processes. Remote sensing is needed to monitor highly dynamically estuarine CDOM. Using in situ data from four seasonal cruises, an algorithm is developed to estimate CDOM absorption coefficient at 400 nm (a_CDOM(400)) in the Zhujiang (Pearl River) Estuary (ZJE). The algorithm uses band ratios of R_rs(667)/R_rs(443) and R_rs(748)/R_rs(412). By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite (MODIS/Aqua) data from 2002 to 2014, seasonal climatology a_CDOM(400) in the ZJE is calculated. CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography. Along the section vertical to a water depth gradient, the seasonal a_CDOM(400) exponentially decreased (y=ae^bx, b<0), but with great differences among seasons. Riverine fresh water is the primary source of CDOM in the ZJE. Fulvic acid fraction decreases with increasing salinity. Using developed algorithms, conservative CDOM mixing equation, and river discharge, effective riverine end-member concentration and flux of dissolved organic carbon (DOC) in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data. Both effective riverine end-member DOC concentration and flux are positively related to the river discharge, significantly in summer with R² of 0.698 for concentration and 0.965 7 for flux.

High-resolution approaches such as multiple signal classification and estimation of signal parameters via rotational invariance techniques (ESPRIT) are currently employed widely in multibeam echo-sounder (MBES) systems for sea floor bathymetry, where a uniform line array is also required. However, due to the requirements in terms of the system coverage/resolution and installation space constraints, an MBES system usually employs a receiving array with a special shape, which means that high-resolution algorithms cannot be applied directly. In addition, the short-term stationary echo signals make it difficult to estimate the covariance matrix required by the high-resolution approaches, which further increases the complexity when applying the high-resolution algorithms in the MBES systems. The ESPRIT with multiple-angle subarray beamforming is employed to reduce the requirements in terms of the signal-to-noise ratio, number of snapshots, and computational effort. The simulations show that the new processing method can provide better fine-structure resolution. Then a high-resolution bottom detection (HRBD) algorithm is developed by combining the new processing method with virtual array transformation. The application of the HRBD algorithm to a U-shaped array is also discuss. The computer simulations and experimental data processing results verify the effectiveness of the proposed algorithm.

Based on satellite altimeter and reanalysis data, this paper studies the relationships between the intensity of the Kuroshio current in the East China Sea (ECS) and the East Asian winter monsoon (EAWM). The mechanisms of their possible interaction are also discussed. Results indicate that adjacent transects show consistent variations, and on an interannual timescale, when the EAWM is anomalously strong (weak), the downstream Kuroshio in the ECS is suppressed (enhanced) in the following year from February to April. This phenomenon can be attributed to both the dynamic effect (i.e., Ekman transport) and the thermal effect of the EAWM. When the EAWM strengthens (weakens), the midstream and downstream Kuroshio in the ECS are also suppressed (intensified) during the following year from October to December. The mechanisms vary for these effects. The EAWM exerts its influence on the Kuroshio's intensity in the following year through the tropospheric biennial oscillation (TBO), and oceanic forcing is dominant during this time. The air-sea interaction is modulated by the relative strength of the EAWM and the Kuroshio in the ECS. The non-equivalence of spatial scales between the monsoon and the Kuroshio determines that their interactions are aided by processes with a smaller spatial scale, i.e., local wind stress and heating at the sea surface.

High-frequency surface wave radar (HFSWR) and automatic identification system (AIS) are the two most important sensors used for vessel tracking. The HFSWR can be applied to tracking all vessels in a detection area, while the AIS is usually used to verify the information of cooperative vessels. Because of interference from sea clutter, employing single-frequency HFSWR for vessel tracking may obscure vessels located in the blind zones of Bragg peaks. Analyzing changes in the detection frequencies constitutes an effective method for addressing this deficiency. A solution consisting of vessel fusion tracking is proposed using dual-frequency HFSWR data calibrated by the AIS. Since different systematic biases exist between HFSWR frequency measurements and AIS measurements, AIS information is used to estimate and correct the HFSWR systematic biases at each frequency. First, AIS point measurements for cooperative vessels are associated with the HFSWR measurements using a JVC assignment algorithm. From the association results of the cooperative vessels, the systematic biases in the dual-frequency HFSWR data are estimated and corrected. Then, based on the corrected dual-frequency HFSWR data, the vessels are tracked using a dual-frequency fusion joint probabilistic data association (JPDA)-unscented Kalman filter (UKF) algorithm. Experimental results using real-life detection data show that the proposed method is efficient at tracking vessels in real time and can improve the tracking capability and accuracy compared with tracking processes involving single-frequency data.

Contaminants that are floating on the surface of the ocean are subjected to the action of random waves. In the literature, it has been asserted by researchers that the random wave action will lead to a dispersion mechanism through the induced Stokes drift, and that this dispersion mechanism may have the same order of significance comparable with the others means due to tidal currents and wind. It is investigated whether or not surface floating substances will disperse in the random wave environment due to the induced Stokes drift. An analytical derivation is first performed to obtain the drift velocity under the random waves. From the analysis, it is shown that the drift velocity is a time-independent value that does not possess any fluctuation given a specific wave energy spectrum. Thus, the random wave drift by itself should not have a dispersive effect on the surface floating substances. Experiments were then conducted with small floating objects subjected to P-M spectral waves in a laboratory wave flume, and the experimental results reinforced the conclusion drawn.

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor environments. Anaerobic oxidation of methane (AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment, including pyrite and gypsum. Abundant aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor (cmbsf) in the entire core sediment of HS328 from the northern South China Sea. Most pyrites are tubes consisting of framboidal cores and outer crusts. Gypsum aggregates occur as rosettes and spheroids consisting of plates. Some of them grow over pyrite, indicating that gypsum precipitation postdates pyrite formation. The sulfur isotopic values (δ³⁴S) of pyrite vary greatly (from –46.6‰ to –12.3‰ V-CDT) and increase with depth. Thus, the pyrite in the shallow sediments resulted from organoclastic sulfate reduction (OSR) and is influenced by AOM with depth. The relative high abundance and δ³⁴S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone (SMTZ). The sulfur isotopic composition of gypsum (from –25‰ to –20.7‰) is much lower than that of the seawater sulfate, indicating the existence of a ³⁴S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in OSR. Pyrite oxidation is controlled by ambient electron acceptors such as MnO₂, iron (Ⅲ) and oxygen driven by the SMTZ location shift to great depths. The δ³⁴S values of gypsum at greater depth are lower than those of the associated pyrite, revealing downward diffusion of ³⁴S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater sulfate. These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral, which will be favor to the formation of gypsum. Overall, the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities, and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.

A three-dimensional numerical model is established to simulate the turbulent oscillatory boundary layer over a fixed and rough bed composed by randomly arrayed solid spheres based on the lattice Boltzmann method and the large eddy simulation model. The equivalent roughness height, the location of the theoretical bed and the time variation of the friction velocity are investigated using the log-fit method. The time series of turbulent intensity and Reynolds stress are also investigated. The equivalent roughness height of cases with Reynolds numbers of 1×10⁴–6×10⁴ is approximately 2.81 d (grain size). The time variation of the friction velocity in an oscillatory cycle exhibits sinusoidal-like behavior. The friction factor depends on the relative roughness in the rough turbulent regime, and the pattern of solid particles arrayed as the rough bed in the numerical simulations has no obvious effect on the friction factor.

Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements (REE) and yttrium (REY), with a growing interest in exploitation as an alternative to land-based REY resources. On the basis of comprehensive geochemical approach, the abundance and distribution of REY in the ferromanganese nodules from the South China Sea are analyzed. The results indicate that the REY contents in ferromanganese deposits show a clear geographic regularity. Total REY contents range from 69.1×10^–6 to 2 919.4×10^–6, with an average value of 1 459.5×10^–6. Especially, the enrichment rate of Ce content is high, accounting for almost 60% of the total REY. This REE enrichment is controlled mainly by the sorption of ferromanganese oxides and clay minerals in the nodules and crusts. Moreover, the total REY are higher in ferromanganese deposits of hydrogenous origin than of diagenetic origin. Finally, Light REE (LREE) and heavy REE (HREE) oxides of the ferromanganese deposits in the study area can be classified into four grades: non-enriched type, weakly enriched type, enriched type, and extremely enriched type. According to the classification criteria of rare earth resources, the Xisha and Zhongsha platform-central deep basin areas show a great potential for these rare earth metals.

Multi-beam, sub-bottom and multichannel seismic data acquired from the western Nigerian continental margin are analysed and interpreted to examine the architectural characteristics of the lower parts of the submarine canyons on the margin. The presence of four canyons: Avon, Mahin, Benin, and Escravos, are confirmed from the multi-beam data map and identified as cutting across the shelf and slope areas, with morphological features ranging from axial channels, moderate to high sinuosity indices, scarps, terraces and nickpoints which are interpreted as resulting from erosional and depositional activities within and around the canyons. The Avon Canyon, in particular, is characterised by various branches and sub-branches with complex morphologies. The canyons are mostly U-shaped in these lower parts with occasional V-shapes down their courses. Their typical orientation is NE–SW. Sedimentary processes are proposed as being a major controlling factor in these canyons. Sediments appear to have been discharged directly into the canyons by rivers during the late Quaternary low sea level which allows river mouths to extend as far as the shelf edge. The current sediment supply is still primarily sourced from these rivers in the case of the Benin and Escravos Canyons, but indirectly in the case of the Avon and Mahin Canyons where the rivers discharge sediments into the lagoons and the lagoons bring the sediments on to the continental shelf before they are dispersed into the canyon heads. Ancient canyons that have long been buried underneath the Avon Canyon are identified in the multichannel seismic profile across the head of the Avon Canyon, while a number of normal faults around the walls of the Avon and Mahin Canyons are observed in the selected sub-bottom profiles. The occurrence of these faults, especially in the irregular portions of the canyon walls, suggests that they also have some effect on the canyon architecture. The formation of the canyons is attributed to the exposure of the upper marginal area to incisions from erosion during the sea level lowstand of the glacial period. The incisions are widened and lengthened by contouric currents, turbidity currents and slope failures resulting in the canyons.

Owing to the complexity of the physical mechanisms of rouge waves, the theoretical study of the rogue-wave-structure interaction problems still makes little progress. However, for regular-shaped structures, it is possible to give a theoretical analysis, if a relatively simple model of the rogue waves is used. The wave load, induced by a focusing wave which is known as an intuitive basic model of the rouge waves, upon a semi-submerged cylinder is studied analytically. The focusing wave is approximate by the Gauss envelope wave, an ideal model which contains most features of the rogue wave. The diffraction velocity potential is derived through the separation of flow field, and the formulas of the horizontal force and bending moment are proposed. The derived formulas are simplified appropriately, and validated through comparison against numerical results. In addition, the influence of parameters, such as the focusing degree, the submerging depth and the wave focusing position, is thoroughly investigated.