Based on a tripod measurement in the Laizhou Bay from October 21 to November 6, 2018, the unit-width bottom sediment transport rate and the effects of strong winds on bottom sediment transport are analyzed using the ensemble empirical mode decomposition, the Hilbert-Huang transform and the wavelet analysis method. The resuluts show thta the unit-width sediment transport rate can be divided into four intrinsic mode functions with increased periods including the high-frequency, tidal-period, low-frequency and long-period. The high-frequency and tidal-period components have the highest variance contribution rate and energy, indicating their greatest impact on sediment transport. The marginal spectrum shows a significant period of 13.3 h in the east-west direction, and a period larger than 11 h in the north-south direction. The net bottom sediment fluxes in the east-west and north-south directions are 305.77 kg/m and 597.25 kg/m, respectively; and the high-frequency and low-frequency component contribute least while the residual-current component contributes most. Winds work on the time-frequency distribution of the unit-width sediment transport rate mainly through the turbulence and waves during the wind decrease periods, which enhances the low-frequency domain significantly, and further induces the high-frequency fluctuations with periods about 1 h. The cross-wavelet analysis shows the winds and the unit-width sediment transport rate have a strong coherence on the low-frequency band; and the latter lags behind the former by 1/4 to 1/2 period. In addition, the wind-waves enhance the asymmetric sediment transport between flood and ebb tidal phase, which increases the net sediment flux of tidal period.

To investigate the characteristics of the flow field around non-submerged structures under solitary waves, a numerical model of the interaction between solitary waves and marine structures is established based on the meshless SPH method. By calculating and analyzing the characteristics of the wave surface, velocity, vorticity, and structure force under different amplitude solitary waves, the influence of relative wave height on the flow field around the non-submerged structure was explored. The results show that the flow field characteristics are closely related to the relative wave height. With a little relative wave height, the wave surface, velocity, vorticity, and structure force are smooth while the flow field fluctuate around the structure due to that the wave crest climbs to the top of the structure and collide with the water in the tank after passing the structure when the relative wave height is large than 0.2. The fluctuation amplitude of wave surface, velocity, vorticity and structure force increased with the increase of relative wave height, resulting in a more complex flow field. Meanwhile, the horizontal and vertical negative force of the structure are larger, the distribution of vorticity around the structure gradually develops to the depth and downstream direction.

Rip current is a kind of high speed offshore current which occurs frequently in coastal. Based on Castelle’s rip current classification model, Google Earth images of 14 beaches in Guangdong Province were interpreted and classified, and the application of rip current classification model in remote sensing images was discussed. The results show that in high risk months, the composition of rip currents is relatively simple, the mixed rips are few, and the bathymetrically-controlled rip currents play a dominant role, and the number of rip currents remains at a high level. In the middle risk months, the proportion of hydrodynamically-controlled rip currents and mixed rips increases, while the proportion of bathymetrically-controlled rip currents still has a certain proportion. There is little or no rip currents in low-risk months. The structure of rip current is closely related to the state of beach. For the beach in the bay, the length of the bay affects the number of rip currents, and the concave degree of the bay affects the composition ratio of different types of rip currents. Considering the limitations of experimental conditions, this law needs to be further studied and verified in combination with the actual terrain and landform. The classification results obtained according to the interpretation criteria presented in this paper are in good agreement with the risk evaluation model proposed by previous authors, which further demonstrates the effectiveness of the interpretation criteria and provides some reference value for the future research and classification of rip currents.

Hydrographic data collected from March to April 2014 by CTD-SRDL mounted on northern elephant seal were analyzed to study the distribution and decline of the temperature inversion over the eastern continental slope in Gulf of Alaska. The results show that temperature inversion occurred significantly in this region. Temperature difference was between 0.2°C and 1.6°C and thickness of temperature inversion was between 20 m and 280 m, respectively. The temperature difference increased northward along the continental slope, while the thickness thickened from 50°N to 58°N, but the average thickness at north of 58°N was relative thinner. The temperature inversion was decay during March 25 to April 22, 2014. The subsurface maximum temperature continued to fall, the temperature difference tended to be weaker, and the thickness presented a thinning tendency. Numerical results of a one-dimensional model reveal that, the temperature at the upper mixed layer increased by heating on the sea surface, but the temperature at the bottom of the mixed layer remained low, therefore the minimum temperature of temperature inversion change was not notable. With a strong temperature gradient in the subsurface, the subsurface maximum temperature dropped pronouncedly due to the turbulent diffusion, which is the main reason for temperature inversion decline. Turbulent diffusion modified temperature and salinity in subsurface water to be uniform, thus it is important to study this process for the formation and evolution of temperature inversion.

Tidal-current-asymmetry (TCA) influences sediment transport and geomorphologic changes. It is of paramount importance to understand the current asymmetry in this area in context of a long-term scale with consideration of development and protection of the coastal resources. The radial sand ridges (RSR) in the South Yellow Sea is patterned with strong tidal forcing and complex hydrodynamic environment. This paper simulated tidal current field in the RSR based on the Delft3D model and used combined harmonic analysis and skewness theory to analyze the spatial distribution of the TCA under varied shoreline conditions. The results show that peak-current-asymmetry (PCA) in the RSR is mostly flood-dominant and slack-water-asymmetry (SWA) also shows positive, meaning the flooding duration is shorter than the ebbing duration. Both the positively-dominant PCA and negatively-dominant SWA are mainly affected by the nonlinear interactions between the semidiurnal diurnal tides (M₂, S₂) and shallow water tides (M₄, MS₄). As the shoreline gradually moves towards sea during 1984 to 2014, although the nature of $ {\gamma }_{\mathrm{P}\mathrm{C}\mathrm{A}} $ remains, the magnitude of which increases by up to 25%. Meanwhile,$ {\gamma }_{\mathrm{S}\mathrm{W}\mathrm{A}} $ decreases by up to 20%, which intensifies its shorter-flooding-duration pattern in the core area of the RSR.

Magnetic mineral diagenesis is an important early diagenetic process after the burial of sediments and its proper identification is the precondition of interpretations for the mineral magnetic properties in the sediments. This study carried out analyses of sedimentary facies, room temperature magnetic and thermomagnetic properties in a Holocene Core MZ collected in the Shunde Plain of the Zhujiang River Delta to identify the vertical changes in the assemblage of magnetic minerals, so as to explore the early diagenetic stages and possible linkage to the sedimentary facies. The results show that the Holocene sedimentary sequence of Core MZ includes tidal channel, embayment, and deltaic successions from bottom upward. The magnetic properties at room temperature lack correlation with sedimentary facies and demonstrate features of strong early diagenesis. In addition, the magnetic properties of the late Holocene sediments were strongly influenced by the human activities. The early diagenesis mainly includes the dissolution of magnetic minerals and the formation of authigenic pyrite. Greigite was also identified in the upper section of the delta-front succession and the bottom of embayment succession. The concentration of greigite increases with depth in the embayment succession. According to the magnetic mineral assemblages, we infer different formation mechanism of greigite in the two successions. We suggest that the greigite in the delta-front facies was formed in the sulfate reduction stage of early diagenesis, whilst it was formed in the anaerobic oxidation stage of methane in the embayment facies. These phenomena indicate that sedimentary environment has impacts on the early diagenetic stage of magnetic minerals by controlling the availability of organic matter and sulfate.

In this paper, surface characteristics of mesoscale eddies in the Japan Sea (JES), including size, polarity, life cycle, amplitude, and trajectory, are analyzed by using eddy datasets and sea level anomaly altimeter data from 1993 to 2019. Over the 27-year period, a total of 1429 eddies were detected with nearly equal number of cyclonic and anticyclonic eddies (CEs and AEs, respectively). Strong seasonal variability was observed for both polarities of eddy. The eddies were most generated in autumn, followed by winter and the least in the spring. Mesoscale eddies are prone to generate in the Ulleung Basin and Yamato Basin, which distributed in a southwest-northeast zonal belt. Among them, ACs are dominant in the southern JES, while CEs in the northern JES near the Tsugaru Strait. The western and southern movements of the mesoscale eddies were driven by the East Korean Warm Current and Tsushima Warm Current. In the northern JES, the mesoscale eddies were more related to the Liman cold current and subpolar front current. Further studies shown that dynamical instability is an important reason for the generation of eddies in autumn and winter. However, semi-enclosed basins, local flow fields, and complex air-sea interactions may all have a certain impact on the generation and dissipation of the mesoscale eddies.

Data assimilation can estimate the uncertain parameters in the numerical model while adjusting the state variables with observations to improve the simulation results through enhancing the numerical model. Based on the ensemble adjustment Kalman filter (EAKF) and the external mode of the Princeton ocean model with generalized coordinate system (POMgcs), a bathymetry estimate is performed in the M₂ constituent simulation of the Bohai Sea and part of the Yellow Sea. The results of the ideal data assimilation experiment or identical twin experiment show that the EAKF method can retrieve the “truth” bathymetry. In the practical data assimilation experiment of the NAO.99Jb and tide gauge data, by comparing with the 34 tide gauges, the model simulated amplitude and phase lag errors of M₂ constituent are reduced by 40.27% and 49.19%, respectively, by use of the posterior estimate of the bathymetry.

In order to better understand the sedimentary rate changes in the Caroline area which is located in the north of West Pacific Warm Pool, a comprehensive dating method was carried out by using radiocarbon testing(¹⁴C), oxygen isotope and paleomagnetism on a gravity core from the Caroline area of the western Pacific Ocean. ¹⁴C data provide the age of the upper section since 44.3 ka BP for this core. Subsequently, the age framework since MIS4 (about 80 ka) which corresponds to the depth of 125 cm was established by using oxygen isotope and relative paleointensity (RPI) data, while the upper part also considered the ¹⁴C data. Further analysis revealed that there was an obvious sedimentary discontinuity at the depth of 126 cm to 127 cm in this core, although it has been beyond the range of ¹⁴C dating, but the paleomagnetic results show that the core formed in Brunhes period, and the relationship between RPI and oxygen isotope data under the hiatus provide a robust evidence that the age is from 180 ka to 130 ka in the bottom. At the end the deposition rate of the core was obtained, which is 1 cm/ka to 2 cm/ka, and it is consistent before and after the deposition hiatus. At the same time, the disparity of the deposition rate for each dating method indicated that there was a large deviation of ¹⁴C data in one layer maybe due to the high rate of foraminiferal shell breaking.

The Jiaomen outlet is the main flood and sediment discharge of the Zhujiang River. It is connected with Humen outlet through a lateral branch, namely the Fuzhou Channel. The flow and sediment division ratio of the bifurcated Jiaomen outlet are important for flood control and navigation safety of the Guangdong-Hong Kong-Macao Greater Bay Area. Focusing on the flow division ratio of the Fuzhou Channel, this study designed a series of scaled physical experiments to explore the relationship between flow division ratio of the Fuzhou Channel and the flow of Jiaomen outlet and adjacent Humen outlet. The dimension of the physical model is based on morphological characteristics in the vicinity of the Jiaomen outlet nowadays. Results of the experiment are in good agreement with the filed measurements under two different flow conditions, demonstrating a reliable model performance. Subsequently, series of experiments have been carried out by varying upstream discharges of Humen and Jiaomen. Experimental results indicate that the division ratio of the Fuzhou Channel depicts a positive relationship with the flow velocity ratio between Humen and Jiaomen. Thus, the flow division ratio of the Fuzhou Channel depends on both Humen and Jiaomen. The experimental results further suggest that, under present geomorphic situation, if the upstream velocity ratio between Humen and Jiaomen decreases to 0.35, the Fuzhou Channel would shift from the main branch to secondary. The research results can provide a reference for the artificial regulation of Jiaomen outlet and its flood and navigation safety.