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There is strong tide in the Changjiang (Yangtze River) Estuary and its adjacent area. Except for the coast area, there is a lack of longterm tide level and tidal current data in the offshore area. Long time series of water level observation data was used in this study, and the results reveal that the tidal type in the Changjiang Estuary is a regular semidiurnal tide, with a significant shallow water division in the nearshore area; the M2 division is the most significant semidiurnal tide, and the amplitude tends to increase from the open sea in the east to the shallow water or island group at the mouth of Hangzhou Bay in the west. The M2 tidal current is the most significant semidiurnal tidal current, and the rotating tide is the most significant semidiurnal tide. The two stations to the south of the Changjiang mouth are rotating counterclockwise, while the stations to the east of the mouth are rotating clockwise. The vertical structure of the tide has significant spatial differences, the ellipticity of the M2 tidal current is mostly negative, the ellipticity of the M2 tidal current, the direction and the arrival time of maximum velocity all vary significantly with depth.

The river-estuary-coastal ocean continuum (referred to as the continuum hereinafter) is a transition zone connecting lands and oceans. The carbon budgets in the continuum are dynamic and uncertain components in global carbon budgets. This complex landocean interactive ecosystem can absorb atmospheric CO2 through photosynthesis and dissolution of CO2. Also, the carbon fixed by photosynthesis or chemical weathering in land and watershed can be transported horizontally to the shelf waters and open oceans. In this paper, the progress of carbon cycles in the continuum is reviewed by taking the famous Chesapeake Bay and Changjiang Estuary-East China Sea continuum as typical examples. It is concluded that systematic observation characterized with land-sea coordination, sea-space integration, point-line combination, should be combined with physicalecological numerical simulation to reveal the multiple time-space scale processes. The strategy is generally operable, and the historical retrospective of results is also achievable. Thus, it can be used to clarify the evolution of carbon exchange along the river-estuary-coastal ocean continuum and their influences on carbon budgets under the combined pressures of climate change and anthropogenic activities.

Abstract: The impact of the flood event on the distribution and source of particulate organic carbon(POC) in Changjiang (Yangtze River) Estuary and adjacent waters was analyzed based on the data of temperature, salinity, total suspended matter(TSM), POC and δ13CPOC ,which were collected during the July 2020 flood. The results show that POC is negatively correlated with salinity (r2=0.41, p＜0.01), and positively correlated with TSM (r2 =0.92, p＜0.01). The mixing of salt and fresh water is an important factor affecting the distribution of POC. The distribution of δ13CPOC values in the surface water indicates that the phytoplankton production is another important factor affecting the distribution of POC in the northeastern part of the study area. Flood events reduce the concentration of terrigenous POC due to the dilution of high runoff, meanwhile, light δ13CPOC values in the southeastern part of the study area indicate that flood events could expand the influence range of terrigenous POC in the East China Sea.

Orbital data are important parameters involved in the satellite data processing and HY1C satellite products with high quality are inseparable from the accurate calculation of the orbit. In this study, data were extracted from the TLE (TwoLine Orbital Element) and used to accurately simulate satellite orbit based on STK (Satellite Tool Kit) software. The ephemeris was outputted to compare the accuracy of two satellite orbit algorithms of HY1C and evaluate the influence of perturbation factors on orbit calculation. Method one uses an algorithm which does not consider perturbation factors and extrapolates the ephemeris parameters of the observation time based on the orbit elements of the reference time, and then calculates the satellite orbit data. Method two adopts the SGP4 model which considers perturbation to calculate the orbit data. The results show that perturbation has a significant impact on the orbit calculation. The algorithm error without considering the perturbation increases significantly with the passage of time, and the position errors are less than 10 km with the speed errors less than 10 m/s in half an hour. While SGP4 model algorithm runs fast with high calculation accuracy and good stability, the position and speed errors within 24 hours are less than 68 m and 0.051 m/s respectively. Therefore, SGP4 model algorithm can be used for the highprecision orbit calculation of the loworbit satellite HY1C.

As an ecological buffer zone, the salt marsh plants growing in the coastal zone play an important role in reducing the current velocity, weakening wave energy and preventing coastal erosion, it is of great significance to investigate the mechanism of wave attenuation by salt marsh plants in estuaries and coastal zones. Based on the open source CFD software package of OpenFOAM software, a 3D numerical model considering the effect of vegetation on flow and wave was established in this study. Firstly, the model was applied to investigate the propagation processes of dambreak wave over the triangle obstacle and the solitary wave climbing on the sloping beach, the results show that the OpenFOAM model can accurately capture the propagation of dambreak waves and free water movement of solitary waves. Then this model was also used to simulate the formation, development and attenuation of solitary waves in a vegetated wave flume, where the wave height of solitary waves decreases obviously through the vegetation zone, the vegetation can effectively attenuate wave energy on a coastal beach. Lastly, the propagation process of sine waves on the vegetated beach was numerically studied, the obtained numerical results show that the attenuation of wave height is directly proportional to the incident wave height, plant density, the drag force coefficient of plant and the steepness of the coast.

The combination of human activities and natural factors has formed the eutrophication of the Changjiang (Yangtze River) Estuary and its adjacent waters, leading to increased hypoxic condition in the bottom water in summer, which has become an important signal of the deterioration of ecosystem health. This paper combs the important understandings gained from the recent studies of hypoxia in this area, analyzes multiscale temporal changes of dissolved oxygen, e.g., focusing on the tidalscale, eventscale, and interannual scale, and factors relevant to stratification and material transport. The relevant mechanisms analyzed includes processes such as the diluted water extension, Taiwan Warm Current, fronts, wind field and tides that affect oxygen consumption or transport process. It is also revealed that the main hypoxia phenomena were separated in the Changjiang Estuary and the coastal waters of Zhejiang Province. The similarities and differences in the formation and evolution of the two hypoxic zones were presented. At present, a solid foundation has been laid for the understanding of the hypoxia occurrence, however due to its multiscale temporal variations, field experiments and quantitative studies should be strengthened from a multidisciplinary perspective, and the longterm evolution trend of hypoxia in this area should also be clarified based on longterm time series monitoring.

Based on the sea surface wind data at 10 m during 1979 to 2018 from European Center for MediumRange Weather Forecasts (ECMWF), the Growing Hierarchical Self-Organizing Map (GHSOM) method were used to analyze the seasonal variation and interannual anomaly variation characteristics of near-surface wind field over the South China Sea (SCS). Four feature patterns are extracted in the first-layer GHSOM from original wind field data, which highly summarize the seasonal variation characteristics, and the second-layer results reveal the monthly variation characteristics. Four anomaly feature patterns also are extracted in the first-layer GHSOM network and they are anticyclonic wind anomaly, cyclonic wind anomaly, southwest wind anomaly and northeast wind anomaly patterns, respectively. Anticyclonic and cyclonic wind anomaly patterns are closely related to ENSO events with time lags by three months and five months comparing with Niño3.4 index. Anticyclonic and cyclonic wind anomalies also show asymmetry, that is, the amplitude of anticyclonic wind anomaly is obviously larger than that of cyclonic wind anomaly. The occurrence frequency of the northeast wind anomaly pattern is greater than that of the southwest wind anomaly pattern. The more SOM patterns in the second layer expose particulars of anomaly wind.

Sea surface temperature (SST) is the critical factor for depicting the marine thermal distribution. Daily global SST data sets support the typhoon elaborated monitoring and other marine disasters forecast. SST products retrieved by the visible infrared radiometers and mediumresolution imagers have high spatial resolution, while the SST products retrieved by infrared remote sensing are affected by clouds, fog and haze, and therefore a large areas under the clouds are lack of value. SST products retrieved by the microwave radiometer have low spatial resolution, while the microwave could penetrate the cloud layer to achieve all-weather sea surface observation. The data interpolation empirical orthogonal function method (DINEOF) was used to reconstructed the global SST products, and FY-3 (Fengyun 3) SST data sets were applied in this study, which included the SST data sets from the FY-3B/FY-3C Visible and Infra-Red Radiometer, FY-3D Medium Resolution Spectral Imager and FY-3D Micro-Wave Radiation Imager. Accuracy of the reconstructed data sets was verified using OISST measurements to demonstrate the validity and reliability of the DINEOF method. The results show that DINEOF reconstructed sea surface temperature (DSST) data are validated reliable. Root mean square error of the original data is ranging from 0.59 ℃ to 0.70 ℃, while the reconstructed data is relatively stable, ranging from 0.10 ℃ to 0.34 ℃. Correlation coefficient obvious raises from 0.33-0.48 to 0.78-0.98. Multi-sensors reconstructed SST products is continuous and credible in spatial distribution and monitor the variation of warm pool from spring to winter. Addition of FY-3D microwave SST products has significantly improved the spatial continuous distribution and temporal resolution of reconstructed SST.

A large scale mud deposit associated with the Changjiang (Yangtze River) has been formed over the inner shelf waters of the East China Sea. It serves as both source and sink for finegrained sediment and organic matter. Three scientific problems in regional sediment dynamics have been identified, i.e., the processproduct relationships of the mud deposit, the role played by the mud in ecosystem dynamics, and the potential of future magnitude of the carbon reservoir contained in the sedimentary system. The research topics include the future evolution of the Changjiang mud deposit, the generation of sediment gravity flows, organic matter content in the deposit in relation to water column primary production and hypoxia, wave energy attenuation over the mud bed, the decay of particulate organic matter in response to resuspension, and the carbon reservoir pattern in relation to the evolution of the mud deposit. Such research requires an enhanced ability to collect longterm, continuous, highresolution data associated with the benthic boundary layer, the water column and some new sources (e.g., data derived from in situ imagery analysis). The bottom boundary layer data are useful to the studies on sediment gravity flow, wave energy dissipation over the mud area, and the turbulenceinfluenced sediment initiation conditions. The water column data will help to establish the delay curves of organic matter, which is critical to deal with the organic matter burial rate, the formation of shallow gas, and the carbon reservoir issues. Furthermore, there is a demand to collect innovative types of data, to obtain additional information on material source and mud deposit evolution, which awaits technological breakthroughs from the observation systems.

 In summer, large areas of low dissolved oxygen or hypoxia are prone to occur in the bottom waters of Changjiang (Yangtze River) Estuary. The zooplankton community (＞160 μm) in hypoxic area (DO＜2 mg/L), low dissolved oxygen area (2 mg/L＜DO＜3 mg/L) and normal area (DO＞3 mg/L) of the Changjiang Estuary in summer of 2016 and 2017 were compared. The results showed that the abundance and biomass of zooplankton in hypoxic area were significantly higher than those in the low dissolved oxygen area and normal area in 2016. The abundance of small mediumsized copepods and gelatinous zooplankton in hypoxic area and the low dissolved oxygen area were all higher than those in the normal area. It was dominated by filterfeeding of the class Thaliacea and Appendiculata in the summer of 2016 when the degree of hypxia was more serious, but in the summer of 2017, it was dominated by carnivorous Chaetognaths of the class Sagitta.

Mangroves, coastal salt marshes and seagrass beds, as the typical coastal blue carbon ecosystems, have been widely recognized for their remarkable capacity in carbon storage. Vegetation carbon pool and sediment (or soil) carbon pool were considered to be the major carbon pools within the coastal blue ecosystems and their variations determined the overall carbon sequestration of the ecosystems. From a perspective of carbon pool interactions, this study summarized the previous research work based on literature review, including the interactions within various vegetation carbon pools and within various sediment carbon pools, as well as the interactions between vegetation and sediment carbon pools. Interspecific competition, allochthonous carbon input and biogeomorphology were found to be the key to understand the carbon pool interactions. Finally, a perspective on the current state-of-the-art of blue carbon pool study is offered, with challenges and suggestions for future directions.

The Pacific Ocean is the main region occurring the interannual and interdecadal variabilities of sea surface temperature. Comparing to the sea surface temperature, the variabilities of ocean heat content in the Pacific Ocean were less studied. Therefore, this paper studied the variabilities of ocean heat content (at depth of 0300 m) in the Pacific Ocean during the period from 1980 to 2020. The Ensemble Empirical Mode Decomposition method (EEMD) was applied to the Institute of Atmospheric Physics (IAP) heat content data to extract the signals at different time scales, and then the Empirical Orthogonal Function (EOF) was applied to analyze the temporal and spatial characteristics of the ocean heat content at different time scales. The results showed that besides the interannual variation, there were also evident interdecadal variations and longterm warming trends of heat content at depth of 0~300 m in the tropical northwest Pacific. In the eastern Pacific and the highlatitude western Pacific, the interdecadal variability of heat content was not prominent. In the tropical northwest Pacific, the heat content was higher during 19801988 and 19992013 than those during 19891998 and 20142020. Our analysis showed that the interdecadal variability was mostly occurred at 5°N—20°N, 120°E—180°E, and at depth of 50200 m in the tropical northwestern Pacific. The interdecadal variation of ocean heat content in the tropical northwestern Pacific played an important role in the interdecadal variation of global sea surface temperature.

The foot of the continental slope is an important topographical feature of the continental margin. Its the basis for coastal states to extend its continental shelf rights and to delimit the outer limit of the continental shelf beyond 200 nautical miles. Its also an important technical parameter that the Commission on the Limits of the Continental Shelf pays special attention to when considering the submissions of coastal states. The formulation of the continental shelf regime in Article 76 of the United Nations Convention on the Law of the Sea originates from the typical passive continental margin. However, due to the diversity and complexity of the global continental margin, especially the transformation and influence of late tectonic activities and sedimentation on the continental margin, the seabed topography is extremely complex and changeable, which makes it very difficult to identify the foot of the continental slope. In addition, in order to obtain the largest extent of the outer continental shelf, each coastal state has interpreted the relevant provisions of the foot of the continental slope in their own favor, making the foot of the continental slope a hot and controversial issue in the delimitation of the outer continental shelf. Based on the provisions of the United Nations Convention on the Law of the Sea and the "Scientific and Technical Guidelines of the Commission on the Limits of the Continental Shelf" on the foot of the continental slope, combined with the geological characteristics of different types of continental margins and the delimitation practice of various coastal states, the determination of the base of the continental slope, the selection of the point of greatest change and the application of the evidence to the contrary are discussed.

The Changjiang (Yangtze River) Estuary has been subject to the double pressure of human activities and natural changes for a long time. As a result, the change of environmental factors may lead to a great alteration of phytoplankton community composition in this area. To explore the composition and variation of phytoplankton community in the Changjiang Estuary and compared with historical data, phytoplankton samples were collected vertically using net trawl method during “LORCE” cruise in August of 2017. Among all the samples collected, 7 phyla, 86 genera, and 205 species were identified, their total abundance was 1.47×105 cells/L. The results showed that diatoms and dinoflagellates accounted for 95.8% and 1.2% of the total phytoplankton abundance, respectively. Warmwater species, including Pseudonitzschia delicatissima (56.35×103 cells/L), Trichodesmium thiebautii (3.30×103 cells/L), Pseudosolenia calcaravis (3.05×103 cells/L), Chaetoceros lorenzianus (2.64×103 cells/L), Proboscia alata (1.89×103 cells/L) and Coscinodiscus gigas (1.71×103 cells/L), were dominant in the phytoplankton community. Their total abundance was 68.94×103 cells/L, which accounted for 47.00% of the total abundance of netcollected phytoplankton. High abundances of these warmwater species were observed near the front formed by the convergence of the Changjiang Diluted Water and Taiwan Warm Current. Spearman’s rank correlation showed that C. lorenzianus and P. calcaravis were negatively correlated with phosphorus, C. gigas were positively correlated with the concentrations of dissolved inorganic nitrogen, and P. calcaravis was positively correlated with salinity, C. lorenzianus and C. gigas were negatively correlated with salinity. Compared with the summer dominant phytoplankton species during the past 30 years, it was found that warmwater species of phytoplankton in the Changjiang Estuary increased significantly and their distribution area expanded northward. It was speculated that this phenomenon was highly associated with sea temperature elevation and the enhancement of warm current.

 The temporal and spatial change characters of coastline and tidal flat in the islands with different principle functions in the Zhoushan Archipelago were analyzed, using a coastal remote sensing monitoring dataset with 30 m spatial resolutions at annual interval from 1986 to 2017. The results suggested that the coastlines in Zhoushan Archipelago advanced toward the sea, with many water areas(152 km2) and tidal flats(18 km2) reclaimed into lands and the government policies were the main driven factors. The change characters were various among the islands with different principle functions. In particular, the land reclamation was significant in the islands with the principle functions of comprehensive development, coastal industry, coastal tourism, and harbor and logistics, accounting for 96% of the archipelagos new lands. The land reclamation was slight in the islands with marine science and education and scientific fishery functions, accounting for 4% of the archipelagos total new lands. Meanwhile, the coast was stable and well protected in the islands with ecological conversation and clean energy functions. The results could provide scientific basis for coastal zones ecological protection and restoration projects, as well as the marine principle functional zoning.

The acquisition of seawater carbonate system parameters is essential to understand the carbon cycle in coastal ocean, the pattern of CO2 sources and sinks and assess the potential of carbon sinks. Based on the data obtained by 4 seasonal cruises conducted off Changjiang (Yangtze River) Estuary and adjacent East China Sea in March, July, November and December in 2011, we discuss the seasonal and spatial distributions of dissolved inorganic carbon (DIC) and total alkalinity (TA) and their influencing factors. The results showed that the averaged DIC and TA concentrations in inner shelf were increased from summer to autumn, then winter to spring; In cross-section distribution, DIC and TA in summer and autumn showed stratification pattern due to the influence of Changjiang Diluted Water, while in spring and winter, DIC and TA were vertically uniform due to mixing. In inner East China Sea shelf, transect DIC showed a significant negative correlation with temperature and dissolved oxygen, while TA was less regulated by temperature and dissolved oxygen changes, but positively correlated with salinity. DIC was significantly positively correlated with apparent oxygen consumption (AOU), while pH was significantly negatively correlated with AOU. The slope of pH/AOU in the outer East China Sea shelf was -0.002 7 pH/(μmol·kg-1), which was much higher compared with that of -0.001 8 pH/(μmol·kg-1) in the inner shelf. The inner East China Sea shelf seawater (water depth is less than 200 meters) was affected by seasonal ventilation and had stronger carbonate system buffer capacity, which alleviated the seasonal acidification in the subsurface water induced by organic matter decomposition.

In order to explore the distribution, formation mechanism and motion law of eddy around Kuroshio in East China Sea, firstly, the eddy distribution around the Kuroshio in the East China Sea during the past 27 years was analyzed by using the mesoscale eddy data set of the AVISO(Archiving, Validation and Interpretation of Satellite Oceanographic Data). The results show that there are 650 eddies generated in the meander of the Kuroshio, and 271 eddies in the middle part of the Kuroshio. The diameters of the most these eddies were between 100 to 150 km, and the amplitudes were between 2 to 6 cm. Secondly, the motion path and eddy motion process of the Kuroshio in the East China Sea are also analyzed. The results show these the cyclonic eddies are easy to be generated in the inner side of the Kuroshio cyclonic bend, with a long path. For example, at the cyclone bend of the Kuroshio axis in the northeast of Taiwan, the average length of the path was 87.6 km. Otherwise, when these anticyclonic eddies are generated, these eddies usually are wandered. In the middle part of the Kuroshio, the eddy showed the polar symmetric distribution characteristics of these cyclonic eddies in the west side of the Kuroshio main axis and these anticyclonic eddies in the east side of the Kuroshio main axis. Both types of eddies moved northeastward along the Kuroshio main axis. Finally, combined with reanalysis data sets of ocean current and sea surface height, the eddy motion law and generation mechanism were discussed. It is concluded that these eddies generation at the curve of the Kuroshio are related to the separation of the boundary layer of the Kuroshio fluid. The Kuroshio countercurrent from the south of Yanmei Island to the west of Okinawa Island played a key role in the polar symmetric distribution of these eddies in the middle part of the Kuroshio. These eddies usually experience three stages of growth, maturation and decay in the process of movement.

Based on the measured hydrological and water quality data of Xincun lagoon in December 2020, the characteristics of tide in Xincun lagoon were studied, and the effects of tidal elevation changes on nutrients in Xincun lagoon were discussed. The results show that the tide of Xincun lagoon is irregular diurnal. The tidal current at the inlet of the lagoon is a reciprocating current, lasting 15 h for flood tide and 10 h for ebb tide. The concentration of dissolved inorganic nitrogen (DIN), phosphate (PO3-4) and silicate (SiO2-3) vary from 0.91 to 20.87 μmol/L, 0.11 to 5.92 μmol/L and 2.36 to 134.75 μmol/L respectively. The concentrations of DIN, PO3-4 and SiO2-3 at the observation sites in the lagoons changed with the flood and ebb of the tidal process. The flow velocity at the inlet of the lagoon has an important influence on the change of tidal elevation at the observation sites, and the tidal flux basically determines the change of tidal elevation at the observation sites. There is a significant negative correlation between the nutrient concentration at the inlet of the lagoon and at the mariculture area and the tidal elevation, and the tidal current velocity has an important effect on the nutrient concentration at the inlet of the lagoon and the mariculture area. The results will provide scientific basis for pollution control and ecological restoration of Xincun lagoon.

As a key parameter in hydrodynamic and sediment transport models, bottom shear stress is very important to study the initiation and erosion rates of bottom sediment. At present, there are six theoretical methods for calculating bottom shear stress based on field measured flow velocity data: LPmean method, LPmax method, TKE method, TKEW method, RS method and ID method, all of which have their specific applicable conditions. It is very important to select an appropriate method to calculate the bottom shear stress in the shallow water area of estuarine and coastal areas where the actions of current and wave are complex. In this study, one observation site at Dafeng Doulong Port, Jiangsu Province (median particle size: 68.56 μm) and two observation sites at Eastern Chongming Shoal, Shanghai (median particle size: 12.89 μm and 45.02 μm) were taken as examples. Field data were collected using Acoustic Doppler Velocimetry and wave measurement instrument (RBRwave), and the bottom shear stress was calculated by six theoretical methods. The results show that: (1) The LPmean method is affected by the average velocity, the distance from the probe to bed and the strength of waves, which underestimates the bottom shear stress and is not suitable for shallow water environment in intertidal flat; (2) LPmax method and TKE method can overestimate shear stress in shallow water environment of intertidal flat where flow velocity varies greatly and wave action is obvious; (3) TKEW method was modified on the basis of TKE method, which is more suitable for solving the bottom shear stress under strong wave action; (4) The results of RS method are affected by waves, and the results of ID method are more reliable than those of RS method when large waves exist, but ID method will overestimate the bottom shear stress when water depth is insufficient.