In this study, Argo surface salinity, OSCAR current and other data are used to explore the influence of oceanic advection transport on the surface salinity in the Tropical Indian Ocean based on the advection term of the salinity budget equation. The adjustment mechanism of the spatial structure of surface salinity by oceanic advection is revealed by freshwater transport calculation along 6 key sections. The results show that the oceanic advection which transports the high-salinity water in the Equatorial Western Indian Ocean (EWIO) and the Arabian Sea (AS) to the Equatorial Eastern Indian Ocean (EEIO), the Bay of Bengal (BOB) and the Andaman Sea, and also transports the low-salinity water in the EEIO, the BOB and the Andaman Sea to the EWIO, the AS and the Equatorial Southern Indian Ocean, plays a role in adjusting the basic balance of salinity in the Indian Ocean. The analysis of freshwater transport along sections shows that the inconsistency between the center of high precipitation and low salinity in the western sea area of Sumatra, and the inconsistency between the center of high evaporation and high salinity in the western sea area of Australia, are both caused by oceanic advection. In summer, the high-salinity water in the EWIO and the AS transported by the southwest monsoon forced circulation into the BOB, is the main reason for the high surface salinity in the BOB.

Hollow blocks have good water blocking and siltation promotion functions, and have been widely used in ecological restoration projects in recent years. In this paper, combined with flume experiment and Flow-3D numerical simulation, the water blocking effect and sedimentation characteristics of open and semi-closed hollow blocks are analyzed. The results show that the permeability of the hollow block plays a leading role in the internal flow velocity and turbulence intensity, and the semi-open hollow block with small permeability has a better effect in slowing down and turbulence control. The suspended sediment concentration near the bottom of open and semi-closed hollow blocks increases by 56% and 75%, respectively. Both of them can promote the deposition of sediment in the block. The environment of low flow velocity, sediment micro-deposition and water and sediment connected inside and outside by hollow blocks is the habitat requirement of macrobenthos, the structure of low turbulent flow inside the semi-enclosed hollow block is more favorable for the habitat and reproduction of macrobenthos.

The research of tidal changes is vital to ocean engineering, the protection of flooding as well as the utilization of ocean resources in coastal areas. Previous studies are mainly based on long-term hourly tide gauges whose number and location are highly limited. Previous study indicated that the long-term trends of tidal amplitudes are abnormally large in the central deep basin of the South China Sea (SCS) based on 25-year satellite altimeter data, which is not realistic and the resultant of the interference of ocean mesoscale variability on tidal harmonic analysis. In this paper, we use 27-year T/P-Jason satellite altimeter data processed by X-TRACK software to study the long-term tidal trends in the SCS. The satellite altimeter data processed by X-TRACK obviously improves the accuracy and completeness of satellite data in the SCS. Meanwhile, the weighted least square method is used to eliminate the effect of tidal aliasing caused by long period sampling. We find that in most areas of the SCS, the amplitudes of four major tidal constituents have significant long-term trends. The significant positive and negative long-term trends of amplitudes and phases are mainly distributed in the coastal areas such as the western Luzon Strait, the Strait of Malacca and Taiwan Strait, where the water depth and shoreline change dramatically. The largest positive long-term trend of amplitudes can reach 2.75 mm/a and the largest negative long-term trend of amplitudes can reach −2.16 mm/a. The long-term trends of tidal amplitudes in the SCS should be related to river flow and human interference.

A support vector machine (SVM) sea ice classification method of Haiyang-1C (HY-1C) satellite coastal zone imager (CZI) images based on the optimal feature set is proposed in this paper. The spectral features and the texture features of CZI images are extracted, and then distance separability criterion is used for feature selection to obtain the optimal feature set. The sea ice classification experiment and analysis of the three CZI images of Liaodong Bay are carried out based on SVM classification method with the optimal feature set as the input of the classifier. The results show that the sea ice classification accuracy obtained by the proposed method is better than that of only using the spectral features or the texture features. The sea ice classification accuracy of December 19, 2020, January 10, 2021 and January 16, 2021 are 93.67%, 91.75% and 84.89%, respectively, all above 80%. The sea ice area of Liaodong Bay is estimated according to the sea ice classification map. It is found that the sea ice area of Liaodong Bay in the three images increased successively, and the maximum area is about 11 998.98 km².

The marine ecological disasters occurred frequently in recent years. A large number of floating algae gather in the sea surface and inshore water, which brings serious harm to the economic activities and ecological health of coastal cities. In this study, HY-1C, GF-1 and HJ-1A/1B satellite remote sensing images were used to extract information and divide the growth stages of Sargassum in the South Yellow Sea from April to June in 2016 to 2020, combined with the MODIS sea surface temperature data, photosynthetically active radiation data and sea surface wind data to explore the effects of environmental factors on the temporal and spatial distribution of Sargassum. The results show that: (1) In terms of time, the Sargassum mainly appeared from April to June every year. Sargassum had the largest range of influence in 2017 and smaller in other years. In terms of space, the Sargassum was first detected in the far sea northeast of the Changjiang River Estuary and disappeared in the sea near 35°−36°N. (2) In terms of growth rate, the growth phase of Sargassum could be divided into three stages: “development-outbreak-extinction”. (3) At different growth stages, sea surface temperature and photosynthetically active radiation had different degrees of influence on Sargassum. The larger area of Sargassum in 2017 was mainly influenced by higher sea surface temperature and photosynthetically active radiation. The southeast monsoon promoted the drift of Sargassum from the southeast to the northwest and north. This shows that the spatiotemporal characteristics of Sargassum are affected by a variety of environmental factors.

Chinese Ocean Color Temperature Scanner (COCTS) of Haiyang 1C/D (HY-1C/D) satellite is mainly used to detect ocean water color, water temperature and other elements. These elements can only be achieved by processing satellite data, and geometric positioning is the core of preprocessing, which directly affects quality of these elements. COCTS has the characteristics of 114° field of view and quaternary whisk broom point by point. A set of complete geometric positioning method has been developed based on COCTS characteristics. The satellite position and velocity corresponding to the sampling time are obtained by using the interpolation method in the satellite ephemeris extracted from 0 level data, and then the transformation matrix from orbital coordinate system (ORB) to earth-centered rotating coordinate system (ECR) will be achieved. Based on the quaternary whisk broom point by point, the ORB viewing vector of every sampling point in a sweep can be calculated by rotating center viewing vector around X and Y axis in corresponding angles. The relationship model of viewing vector and the earth intersection point can be established to carry out geolocation of remote sensing images obtained from band data. This article uses interpolation to replace the traditional complex method that requires 6 orbital elements to calculate the satellite position, and directly calculates ORB to ECR transformation matrix rather than the traditional two-step transformation method. After multiple sets of data calculation and qualitative and quantitative verification, the HY-1C/D COCTS geometric positioning results are consistent. As a result of the sampling pixel scale effect, the error increases gradually from Nadir to the edge of two sides and from the equator to two poles, all within the error of 2 pixels. This method meets certain positioning accuracy requirements and can be employed for geometric positioning of COCTS.

In this paper, MIKE3 is used to establish a three-dimensional hydrodynamic model of Zhoushan and Ningbo. Based on the tidal current verification with the measured data, the difference between the three-dimensional model and the two-dimensional model is compared. Also, the influence of the change of the tidal current field around the Zhoushan Green Petrochemical Phase III reclamation project before and after the implementation is mainly predicted and analyzed. The results show that: (1) Under the same initial conditions, the tidal level and tidal current validation results of two-dimensional model and three-dimensional model are good, and the two-dimensional results are closer to the measured values in some cases. (2) The three-dimensional vertical velocity distribution shows a decreasing trend with the increase of water depth. In general, the tidal current fitting is good, and the relative error of velocity below 0.6H water depth is between 10% and 15%. Considering that the model may not consider the influence of wind field and wave, the calculated surface velocity of local stations is slightly larger than the measured value; the vertical distribution of flow direction is nearly consistent. (3) Before and after the reclamation project, there was no obvious influence on the tidal current field around the project. Only in the northeast, southeast and northwest corner of Dayushan Island, affected by the “bend improvement” and the channel closure between small islands, there is a change in the local tidal current form. On the whole, the layout of reclamation projects conforming to the shoreline will have an effect on the local coastal tidal current, and almost no effect on the large scale tidal current field in the far sea.

Based on the latest measured high-resolution shallow profile and multibeam bathymetric data in the West Philippine Basin in 2018, the marine geological disasters in the central rift and surrounding areas of the West Philippine Basin is analyzed in this paper. In the study area, two types of disaster geological factors are identified: one is destructive geological factors, mainly including landslide, active fault, gully and magma diapir; the second is the restrictive geological factors, mainly seamounts, scarps and trenches. Based on the shallow seismic profile, the type, shape and internal structure characteristics of geological hazards bodies are described in detail. The distribution area and development characteristics are discussed. The main inducing factors and adverse effects of geological hazards are discussed. The identification of geological hazards, the delineation of distribution range and the analysis of causes in the study area can provide important geological basis for marine engineering construction, equipment design and maritime navigation, avoid adverse effects and make risk prediction in advance.

In order to understand the community structure dynamics of fish eggs and larvae in the estuarine waters, four surveys were conducted in the coastal waters of the Huanghe River Estuary in June of 2014, 2015, 2017, and 2018. According to the species composition and quantitative distribution of fish eggs and larvae, the resource distribution of fish eggs and larvae in this water area was comprehensively studied by using the methods of biodiversity index, R software clustering and Pearson correlation matrix analysis. The results showed that a total of 3 829 fish eggs and 234 larvae were collected during the four surveys by horizontal trawl with plankton net. The obtained fish eggs and larvae belonged to 7 orders, 14 families and 15 genera. The dominant species of eggs were Engraulis japonicus and Cynoglossus joyeri. The dominant species of larvae were Konosirus punctatus and Gobiidae sp. All biodiversity indexes were the highest in 2015 and the lowest in 2018. Used the R language to cluster the similarity of the species composition between fish eggs and larvae, and divided the 4 survey years into 3 groups, each grouping the main divergent species were E. japonicus. The results of Pearson correlation matrix showed that salinity was closely related to the biodiversity of fish eggs and larvae. The analysis showed that the annual variation characteristics of community distribution and diversity of fish eggs and larvae in the Huanghe River Estuary and adjacent waters reflected the response of fish to environmental variation.

Jinsha Bay is one of the most important tourist attractions in the Guangdong-Hong Kong-Macao Greater Bay Area and is favored by tourists from all over the world. The XBeach model is used to simulate the nearshore circulation of the Jinsha Bay, and the occurrence of rip current under different simulated wave conditions is studied. The results show that the rip current in the Jinsha Bay is largely affected by wave height and topography. Under the condition of annual mean significant wave height, there is no rip current along the Jinsha Bay. When the incident wave height exceeds a certain threshold, the risk of rip current increases. The intensity and offshore distance of the rip current are positively correlated with the incident wave height. When the wave direction is perpendicular to the coast, it is the best for the generation of rip current. The beach manager of the Jinsha Bay should improve the early warning of the wave condition in order to reduce the harm caused by the rip current. In addition, due to the characteristics of the long headland, the feeder current of the deflection rips generated by the Jinsha Bay comes from the alongshore currents of the headland and the beach. This can be verified by subsequent field observations. The work of this paper also provides some references for the domestic simulation research of rip current using XBeach model.