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Change characters of coastline and tidal flat in the islands with different principle functions in the Zhoushan Archipelago from 1986 to 2017
CAO Wenting, ZHANG Huaguo, LI Rui
Journal of Marine Sciences    2021, 39 (4): 123-131.   DOI: 10.3969/j.issn.1001-909X.2021.04.012
Abstract628)      PDF (2709KB)(3403)      
 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.

Reconstruction of sea surface temperature from DINEOF-based FY polar-orbiting meteorological satellite
SONG Wanjiao, ZHANG Peng, SUN Ling, TANG Shihao, ZHOU Fangcheng,
Journal of Marine Sciences    2022, 40 (2): 10-18.   DOI: 10.3969-j.issn.1001-909X.2022.02.002
Abstract719)      PDF (3384KB)(2306)      
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.
Explorations of marine gas hydrate deposits and the signatures of hydrocarbon venting using in situ techniques
LIU Liping, CHU Fengyou, GUO Lei, LI Xiaohu
Journal of Marine Sciences    2023, 41 (1): 26-44.   DOI: 10.3969-j.issn.1001-909X.2023.01.003
Abstract413)   HTML1736)    PDF (4566KB)(1247)      

Marine gas hydrate deposits are significant temporal reservoirs for hydrocarbons migrating from deep sources. This is crucial to our understanding of ocean carbon cycling. The cold seep, a geological process regarding gas leakage from deep or shallow sources, is usually linked with gas hydrate decomposition. In this thesis, we reviewed the latest applications of in situ monitoring and detecting methods regarding the leakage plumes, migration pathways, and seafloor geomorphologies associated with gas hydrate and cold seep systems, primarily including vessel-and land-based gas plume measurements, surface ocean-lower atmosphere hydrocarbon emission detections, seafloor visualization techniques, and in situ observation networks. The integrated applications of these in situ observation methods provide a nuanced view of the temporal and spatial variability of hydrate and cold seep systems, facilitate understanding of the fate of hydrocarbons, and expand our knowledge of cold-seep biota in a watery desert.

A review of the carbon cycle in river-estuary-coastal ocean continuum
CHEN Jianfang, ZHAI Weidong, WANG Bin, LI Dewang, XIONG Tianqi, JIN Haiyan, LI Hongliang, LIU Qinyu, MIAO Yanyi,
Journal of Marine Sciences    2021, 39 (4): 11-21.   DOI: 10.3969/j.issn.1001-909X.2021.04.002
Abstract1428)      PDF (2040KB)(1022)      
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.


Distribution, movement and generation mechanism of the mesoscale eddy around the Kuroshio in the East China Sea
LI Zhichao, GUO Junru, SONG Jun, BAI Zhipeng, FU Yanzhao, CAI Yu, WANG Xifeng
Journal of Marine Sciences    2022, 40 (4): 1-10.   DOI: 10.3969j.issn.1001-909X.2022.04.001
Abstract628)      PDF (3317KB)(733)      
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.
Assessment of carbon sink potential and driving factors of island forests on national nature reserve
WU Liangxu, ZOU Huimin, CHEN Wei, XU Minghai, CAI Houcai, CHEN Shuyi, LI Xianglan
Journal of Marine Sciences    2023, 41 (1): 96-109.   DOI: 10.3969-j.issn.1001-909X.2023.01.008
Abstract375)   HTML17)    PDF (4905KB)(687)      

The monitoring of carbon flux dynamics and assessment of carbon sink functions of island forest ecosystems are rarely reported due to their special geographical location and few data sources. In this study, the forest ecosystem of the Nanji Island was used as the research object, the carbon sink potential of island forests and their driving factors were assessed. Based on eddy correlation techniques, the temporal variation characteristics and driving factors of net ecosystem productivity (NEP), gross primary productivity (GPP), and ecosystem respiration (Reco) from 2020 to 2021 were explored. Results showed that the forest ecosystem of Nanji Island was carbon sink. Net CO2 uptake in 2020 and 2021 were 516 g C·m-2·a-1 and 598 g C·m-2·a-1, Reco were 1 037 g C·m-2·a-1 and 1 646 g C·m-2·a-1, and GPP were 1 552 g C·m-2·a-1 and 2 244 g C·m-2·a-1, respectively. Total solar radiation (Rg), photosynthetically active radiation (PAR), net radiation (Rn) and sensible heat (H) were significantly and positively correlated with NEP and GPP (p≤0.001); air temperature (Tair) and soil temperature (Tsoil) were significantly and positively correlated with Reco(p≤0.001). The photosynthesis time of Nanji Island forest was longer than the carbon sink time on the daily scale. When Tair reached 10.05-27.76 ℃ and PAR reached 110.47-429.44 μmol·m-2·s-1, the photosynthesis intensity of island forest was higher than that of ecosystem respiration, which showed CO2 absorption. The monitoring and assessment of carbon fluxes in the forest ecosystems of Nanji Island will provide an important theoretical support for the establishment of a dynamic monitoring and assessment management system for blue carbon in China.

Progress of marine sand resource exploration around Hainan Island and suggestions for selection of exploration areas
TONG Changliang, SONG Jiawei, DENG Kaizhang, HAN Xiaohui, WANG Aijun, WANG Yaping
Journal of Marine Sciences    2022, 40 (3): 33-48.   DOI: 10.3969-j.issn.1001-909X.2022.03.004
Abstract403)      PDF (4123KB)(667)      
Marine sands are important submarine mineral resources. The marine sand resources of Hainan Island are widely distributed in coastal zones and continental shelf areas, with large scale, good quality and rich in heavy minerals. The basic distribution characteristics of marine sand resources around Hainan Island are described, and the progress and main achievements of marine sand exploration around Hainan Island are reviewed with emphasis on heavy mineral sand and aggregate sand. Through the exploration, 15 abnormal areas of heavy mineral placer have been delineated in the sea area around Hainan Island, and one large zirconiumtitanium placer deposit has been proved. However, due to the low level of investigation and research, the resource potential of heavy mineral placer is not clear. The scale of sediment survey around Hainan Island has basically reached 1∶250 000, which provides a solid foundation for the exploration of aggregate sand resources. In recent years, billions of cubic meters of aggregate sand resources have been discovered in the east entrance of Qiongzhou Strait and tidal sand ridge area of the western Hainan, and the resource potential is predicted to reach tens of billions of cubic meters. According to the comprehensive analysis, 8 potential exploration areas of marine sand resources can be delineated around Hainan Island. Except the east mouth of Qiongzhou Strait and the tidal sand ridge area of the western Hainan, the northeast continental shelf of Hainan, the southwest continental shelf of Hainan and Beibu Gulf area are all favorable enrichment areas of marine sand resources, and may contain heavy mineral resources potential. According to the specific sedimentary environment, the exploration objectives and tasks of each prospective area are discussed respectively. Combined with the current work progress and existing problems, the suggestions for the future marine sand exploration are put forward.

Spatio-temporal evolution and driving factors analysis of the coastline in Nan’ao Island from 1976 to 2021
NING Zihao, JIANG Changbo, LONG Yuannan, WU Zhiyuan, MA Yuan
Journal of Marine Sciences    2023, 41 (2): 71-82.   DOI: 10.3969/j.issn.1001-909X.2023.02.006
Abstract226)   HTML17)    PDF (3287KB)(559)      

Coastline is one of the important geographical elements to describe the boundary between land and sea. Under the dual influence of natural factors and socio-economic factors, coastline dynamic evolution of different intensities continues to occur. Based on Landsat series satellite remote sensing images, the spatial and temporal evolution of the coastline of Nan’ao Island from 1976 to 2021 was analyzed by RS and GIS technology combined with field investigation, and the driving factors were analyzed by grey correlation analysis. The results show that : (1)In the past 45 years, the coastline of Nan’ao Island has changed significantly. The coastline length has increased by 11.06 km, and the fractal dimension have generally increased.(2)During the study period, the type of coastline changed from natural coastline dominated by bedrock to artificial coastline, the comprehensive index of coastline utilization show an increasing trend, and the main structure of coastline development and utilization show a form of single to multiple.(3)The evolution of the coastline of Nan’ao Island has obvious regional differences. That of Houzhai Town is greatly affected by human factors, and its evolution is more significant. The coastlines of Yun’ao and Shen’ao Towns are mainly affected by natural factors, and their evolutions are relatively slow.(4)Typhoon(natural disasters) and population are the main driving factors of the coastline evolution of Nan’ao Island.

Qiongzhou Strait as a self-adapted low-passing filter?
LI Yan
Journal of Marine Sciences    2022, 40 (3): 9-16.   DOI: 10.3969-j.issn.1001-909X.2022.03.002
Abstract395)      PDF (1618KB)(689)      
Since a diagram depicting "The Great Ocean Conveyor" was first appeared as a logo by Wally Broecker in 1987, how the warmed upper ocean circulation ran through the Indonesian Seas with their complex coastline geometry and narrow passages, known as the Indonesian through-flow, becomes one of the difficult settings in boundary conditions of climate change model. With strong nonlinear effect, a shallow narrow passage forms vertical mixed hotspots on the one hand, and on other hand, it becomes a self-adapted low-pass filter if the tidal resonance units are introduced. Qiongzhou Strait, a sufficient sediment supply and shallow narrow passage for the northern shelf of the South China Sea, is reported with strong tidal current and westward through-flow. And its tidal channel and tidal deltas are maintained by the tidal resonance units introduced themself. Strong disturbances such as typhoon and cold wave can cause storm jet flow through the strait, triggering different high nutrition, algal bloom and hypoxia events over the adjacent Beibu Gulf. Qiongzhou Strait seems to be a noteworthy case of studying how the self-adapted low-pass filter introduced and whether human activities can affect the through-flow on the shallow narrow passages.

Climatic and environmental changes over the last 1 000 years as recorded by the sediments in Beibu Gulf
LIN Junchuan, KONG Deming, CHEN Fajin, HUANG Chao,
Journal of Marine Sciences    2022, 40 (3): 49-61.   DOI: 10.3969-j.issn.1001-909X.2022.03.005
Abstract290)      PDF (3250KB)(635)      
Climate reconstructions for the last millennium are essential for understanding climate change and will provide an important basis for predicting future climate change. However, there are spatial differences in monsoonal precipitation, and the hydrothermal configurations of two important characteristic periods of the past millennium, the Medieval Warm Period and the Little Ice Age, are highly controversial, especially in southern China. Therefore, the Core BBG-02 taken from the northeastern Beibu Gulf were analyzed for chronology, grain size, major elements and trace elements to understand the physical source of the Core BBG-02 and the climate and environmental changes in its source area. The analysis of chondrite-normalized distribution patterns of rare earth element and geochemical indicators reveal that the Red River may be the main source of the Core BBG-02, and the changes in geochemical indicators of the core reflect changes in the intensity of Indian Summer Monsoon. The results indicate that the climate was warm and humid during the Medieval Warm Period and cold and arid during the Little Ice Age, which is consistent with the results of previous studies on the variation of Indian Summer Monsoon and precipitation. The variation of solar radiation intensity is the essential reason of the variation of Indian Summer Monsoon, which is also influenced by ENSO activity and Indian Ocean Dipole.

Interactions between vegetation and sediment carbon pools within coastal blue carbon ecosystems: A review and perspective
CHEN Yining, CHEN Luzhen
Journal of Marine Sciences    2023, 41 (1): 3-13.   DOI: 10.3969-j.issn.1001-909X.2023.01.001
Abstract781)   HTML301)    PDF (1348KB)(614)      

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.

Variations of the Beaufort Gyre and depositional responses in the Arctic Ocean since the 350 ka
YE Li-ming, GE Qian, YANG Kehong, XU Dong
Journal of Marine Sciences    2012, 30 (4): 20-28.  
Abstract128)      PDF (2682KB)(436)      
The Beaufort Gyre was usually suggested as a main factor to control the residence time and moving direction of sea ice in the Arctic Ocean. Based on records of sediment color cycle, Mn content and foraminiferal abundance, we built up the orbital timescale for the core B85-D from the Alpha Ridge, and discussed variations of ice-rafted debris (IRD> 154 μm) in content, composition and provenance since the Late Quaternary. The results suggest that the most distinct variations occurred during the last glacial (MIS2 ~4) as remarked by the near zero contents of calcium and dolomite, indicating that the carbonate debris from Banks Is., Victoria Is. and District of Mackenzie did not deposit at the Alpha Ridge. The carbonate debris, transported by sea ice, was most likely heading to the Eurasian Basin along the off shore of the North America during the last glacial, when the Beaufort Gyre vanished. In contrast, the carbonate debris was mostly trapped in the Amerasian Basin during the last interglacial (MIS5), when the Beaufort Gyre became strong so as to deposit relatively high content of calcium and dolomite, which was up to 16. 4%. By comparison, is it indicated that the state of the Beaufort Gyre during the MIS6 was closely analogous to that during the MIS2~4,but its state during the glaials MIS8 and MIS10 similar to its state during the interglacial MIS5. Therefore,variations in the Beaufort Gyre are not strictly characterized by the glacial-interglacial cycles, which we speculate, to be modulated by the sea ice concentrationas well as the wind pressure.
Spatio-temporal evolution analysis of the coastline inthe Pearl River Delta from 1973 to 2018
XIA Hantao, LONG Yuannan, LIU Cheng, LIU Xiaojian
Journal of Marine Sciences    2020, 38 (2): 26-37.   DOI: 10.3969/j.issn.1001-909X.2020.02.004
Abstract2135)      PDF (3086KB)(1011)      
The Landsat TM/OLI remote sensing images from 1973 to 2018 were obtained as the data source by using the remote sensing and GIS technology. Based on the geographical background information, the spatial and temporal evolutions of the coastline in the Pearl River Delta region over 45 years were analyzed. The results show that the Pearl River Delta changed significantly, a large number of muddy coast changed into urban industrial coast and port coast. The artificialization index of Pearl River Delta coastline was rising, the types of coastline were developed in a diversified direction, the total length and fractal dimension of shoreline were increasing continuously, the main factors of increase shoreline length and fractal dimension were port construction, coastal industrial zone and reclamation.The evolution of the coastline had obvious regional characteristics, and the regions with large changes were mainly concentrated in Shenzhen Mirs Bay, Guangzhou Nansha and Zhuhai Doumen. From the perspective of the main structure of shoreline, each region presented different type changing tendency, substituted the natural shoreline, the industrial and port shorelines became the main type in each region. The intensity of development and utilization was increasing in various regions, among which the intensity of development in Shenzhen was growing the fastest. Social activities and location policies were the main driving factors for the evolution of shoreline.
The seasonal blooming characteristics of phytoplankton and POC export flux in the waters around South Georgia Island: Based on BGC-Argo and satellite remote sensing observations
ZHAO Yueran, FAN Gaojing, WU Jiaqi, SUN Weiping, PAN Jianming, HAN Zhengbing
Journal of Marine Sciences    2023, 41 (4): 1-11.   DOI: 10.3969/j.issn.1001-909X.2023.04.001
Abstract218)   HTML40)    PDF (2882KB)(373)      

The waters surrounding South Georgia Island are one of the highest primary productivity regions in the Southern Ocean with enormous carbon sequestration potential. However, the strength of the biological pump efficiency in this area is still uncertain due to the lack of continuous upper ocean observation data.In this study, the hydrological and biogeochemical parameters obtained from the Biogeochemical Argo (BGC-Argo) floats deployed in the South Georgia Island vicinity during the period of 2017-2020 were utilized to investigate the impacts of physical processes on biogeochemical processes and to estimate the carbon export flux in the Antarctic summer. Results indicated that both upstream (northeast of the Antarctic Peninsula) and downstream (Georgia Basin) regions of South Georgia Island exhibited strong seasonal characteristics in Chl-a, with the latter area having a 4-month sustained period of phytoplankton bloom, suggesting a stable and continuous supply of iron. Using the temporal variability of the seasonal particulate organic carbon (POC) export, the summer POC export fluxes of the upstream and downstream regions were estimated to be 7.12±3.90 mmol·m-2·d-1 and 45.29±5.40 mmol·m-2·d-1, respectively, indicating that the difference might be due to enhanced downward export of organic carbon after the deepening of the mixed layer. The study found that the region maintained a high biological pump efficiency, contrary to the previous conclusion that the Georgia Basin had “high productivity low export efficiency”, which might have been caused by the limited “real-time” representation of the entire seasonal characteristics during ship-based surveys. BGC-Argo provides high spatiotemporal resolution of multi-parameter observation data, and this study demonstrates that it can more accurately quantify and evaluate marine biogeochemical processes and carbon sequestration potential.

Driving force of marine sedimentary source to sink: A case study from Beibu Gulf
Journal of Marine Sciences    2022, 40 (3): 17-32.   DOI: 10.3969-j.issn.1001-909X.2022.03.003
Abstract487)      PDF (3784KB)(587)      
Morphology, distribution and evolution process of submarine canyons in the Asian Continental Margin
WANG Yanbing, HAN Xibin, HU Zhilong, ZHAO Ning, YANG Fanlin, GE Qian, XU Dong, GAO Jinyao
Journal of Marine Sciences    2020, 38 (4): 48-57.   DOI: 10.3969/j.issn.1001-909X.2020.04.005
Abstract365)      PDF (4246KB)(581)      
Based on the SRTM15_Plus depth data, the submarine canyons in the Asian Continental Margin were identified by using the method of combining topographic surface flow analysis with contour geometry analysis. And the morphology, distribution characteristics and evolution process of the canyons in the study area were analyzed. A total of 531 submarine canyons are identified and divided into linear, meandering and dendritic according to the plane shape. The numbers of each type of canyon are 239, 75 and 217 respectively. Linear canyons are mainly distributed in the Bering Sea Basin, the Kuril Basin and the South China Sea. Meandering canyons are mainly distributed in the subduction zone east of the Bay of Bengal. Dendritic canyons are mainly distributed in the junction of the Japan Trench, the Izu Bonin Trench and the Nankai Trough, the South China Sea and the Sumatra subduction zone. According to the distribution of the canyons and the tectonic background in the study area, the morphological evolution process of “Linear-Meandering” was discussed. According to the morphological information of the main valley of dendritic canyons, it is inferred that there are “Linear-Dendritic” and “Meandering-Dendritic” morphological evolution processes.
Study on tide and tidal current near the Changjiang (Yangtze River) Estuary based on observational data
ZENG Dingyong, XUAN Jiliang, HUANG Daji, et al
Journal of Marine Sciences    2022, 40 (1): 12-20.   DOI: 10.3969/j.issn.1001-909X.2022.01.002
Abstract1699)      PDF (2926KB)(972)      
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.

Carbon cycling in costal ocean and CO 2 negative emissions
YU Lei, LI Sanzhong, SUO Yanhui, WANG Xiujuan
Journal of Marine Sciences    2023, 41 (1): 14-25.   DOI: 10.3969-j.issn.1001-909X.2023.01.002
Abstract534)   HTML40)    PDF (2925KB)(516)      

Costal ocean receives a bunch of carbon materials and nutrients from terrestrial sources, relates a lot of carbon-involving interactions. Meanwhile, it is normal that sedimentary reservoir-cap systems with good trap conditions beneath coastal ocean, these entrapments have potentials to storage CO2. This review focuses on the coastal ocean as the research object, and introduces the carbon cycle processes in coastal ocean, their factors which could influence CO2 fluxes in the carbon cycle processes, and the potential carbon storage mechanisms of the coastal marine sedimentary basins. From the perspective of “carbon peaking and carbon neutrality”, the significance of coastal oceans for “Ocean Negative Carbon Emission (ONCE)”, its potential promotion paths, carbon storage potentials in sedimentary basins and the problems faced by coastal oceans are discussed. Overall, the costal ocean is one of the important blue carbon sink areas. In the coastal marine seawater system, improving the reaction efficiency of microbial carbon pump and carbonate carbon pump have positive significance for CO2 negative emissions; The suitable reservoir-cap systems for CO2 storage beneath coastal ocean can not only provide extra spaces, but also guarantee the safety for CO2 storage. In the future, the main research directions should be to inhibit the conversion process of carbon materials to CO2 in coastal oceans and ensure the safety of CO2 storage in sedimentary reservoirs, these could provide theoretical basis and technical guarantee for CO2 negative emissions.

Wave characteristics and their influencing factors on Nanhui tidal flats in the Changjiang Estuary
CUI Minghui, TU Junbiao, MENG Lingpeng, GUO Xingjie, SU Ni, FAN Daidu
Journal of Marine Sciences    2023, 41 (2): 28-44.   DOI: 10.3969/j.issn.1001-909X.2023.02.003
Abstract213)   HTML15)    PDF (6284KB)(408)      

Wave is an important factor to shape the dynamic geomorphology of the open tidal flat, but researches on tidal-flat wave characteristics are still limited. Taking Nanhui tidal flats in the Changjiang Estuary as an example, the wave characteristic parameters and wave spectrum parameters were obtained by inverting flow-velocity and water-pressure data from the Acoustic Doppler Velocimeters (ADVs) at some fixed platforms, and their changes over tidal cycles and associated influence mechanisms were discussed. The results show that both normal wave direction and prominent wave direction at three stations of Nanhui tidal flats are mainly southeast during the observation period, with long-period swells dominating. The effective wave height of the three stations is positively correlated with the water depth, but the fitting coefficients of each station are different over flood and ebb periods. Wave orbital velocities are obviously modulated by the shallow water effect and the flow directions, and their maximum values usually occur at the early flooding stage, while minimum values can be observed to occur during the current transition periods. The wave energy spectrum during ebb tides is featured by the bimodal pattern because of high influence by tidal levels and coastal topography, and the peak energy is continuously attenuated and gradually dispersed with the concurrent shift of peak frequencies.

Seasonal variation of water masses and current field in the northeastern Beibu Gulf based on observations in 2018-2019
Journal of Marine Sciences    2022, 40 (3): 73-85.   DOI: 10.3969-j.issn.1001-909X.2022.03.007
Abstract414)      PDF (6105KB)(670)      
 Hydrological observations were carried out in the northeastern of Beibu Gulf in July and October 2018, February 2019 to reveal its seasonal variations. Sectional measurements of temperature, salinity and current velocity were deployed to the north of 18°N and east of 108°E. The results show that there is obvious seasonal disparities on the character of water masses in this region: the sea water temperature in summer decreases from northern shallow water to southern deep region and the onshore brackish water dominates the area shallower than 30 m, and a occlusive cold water mass appears in deep layer to the west of Hainan Island; while in winter the water temperature increases from north to south, the brackish water shrinks to the northern coast shallower than 10 m, the area is occupied mainly by the mixed water, and a warm tongue appears in upper layer on the west of Hainan Island. The circulation in the research region is mainly counterclockwise in all three seasons, though the strength of current varies in different seasons, and is significantly influenced by wind. The water exchange between the northeastern gulf and outer ocean is not active, since the observed salinity is entirely less than 34. The water mass is generally shear instable, and static instability appears in winter. This suggests that the diapycnal mixing in this region might be strong.