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To assess the potential impact of plumes generated by deep-sea mining on the midwater ocean, this study systematically analyzed the flow field characteristics of the intermediate currents at the 1 000 m and 2 000 m in deep-sea mining areas of the Pacific Ocean (Western Pacific: Block C, Block M, Block CW, Block WJ; Eastern Pacific: Block A5, Block KW, Block EK, Block A12678, Block A3, Block A4) and predicted the zonal movement trend of midwater plumes. The analysis was based on the global Argo float trajectory and mid-depth current dataset from the China Argo Real-Time Data Center covering the period from August 1997 to October 2024, combined with data from 3 moored observation stations. The results show that: (1)The currents at the 1 000 m layer in the Pacific mining areas are mainly controlled by zonal currents, with the velocity of eastward jets being greater than that of westward jets. The velocity and direction of currents in the mining areas are sensitive to changes in latitude. (2)The eastward jets that affect the 1 000 m flow field in the Western Pacific mining area have the center located at 14°N (weak) and 18°N (strong). Under their influence, in the southern part of the Block M, the midwater plumes move eastward. In other areas, the midwater plumes move slowly westward.(3) The eastward jets that affect the 1 000 m layer of the Eastern Pacific mining areas have the centers located at 7°N and 9°N. They are stronger in summer and autumn, and weaker in winter and spring. (4)The flow field directional characteristics in the 2 000 m area of Block M, Block A5, Block KW and Block EK are the same as those in the 1 000 m layer, indicating that the depth affected by jets can reach 2 000 m.

This study was conducted to explore the contribution of silicon dissolution from beach sediments to the dissolved silicon budget in the coastal waters. From March to September in 2017, six field surveying cruises were conducted in the Muping offshore area (Yantai, China), the southern North Yellow Sea. By investigating monthly distributions and the averaged values of dissolved inorganic nutrients, monthly accumulation of dissolved silicate anomaly (ΔSi, as defined with the difference between dissolved inorganic nitrogen and silicate concentrations)of 1.5 μmol·L^-1 was observed in this offshore area with weak circulation from May to August. Further combining laboratory incubation experiments, theoretical calculation and field data analyses, It was found that the permeable particles in beaches could be dissolved, leaching active silicate to seawater, and increasing the offshore silicate concentration by 0.7~2.0 μmol·L^-1 every month, roughly consistent with the monthly accumulation rate of field ΔSi. Extrapolating the beach silicate-leaching flux to the length of the coastline rounding the Yellow Sea, the previously reported imbalance in silicate budget in this coastal sea could roughly be bridged. This study indicated again that the dissolving of permeable particles might contribute significantly to coastal silicate budget.

The sediment source-to-sink system serves as a critical link connecting active carbon pools (e.g., atmosphere, biosphere, hydrosphere) with the stable lithospheric carbon pool, playing a core buffering role in the global carbon cycle. As the core area of marine sedimentary carbon sinks, delta-shelf regions account for over 80% of the global marine sedimentary organic carbon flux while occupying less than 8% of the global ocean area. The processes and mechanisms of carbon burial in these regions are crucial for global carbon balance. This paper systematically reviews the source composition and sedimentary flux characteristics of terrestrial organic carbon in delta-shelf sedimentary systems, focuses on elaborating organic carbon source-to-sink tracing technologies, remineralization processes and their dominant mechanisms, analyzes the impacts of human activities on sedimentary carbon sinks, and discusses marine negative emission and carbon sequestration enhancement schemes based on sediment management. Studies show that the heterogeneity of terrestrial organic carbon, physicochemical conditions of the sedimentary environment, and human disturbance collectively regulate the migration, transformation, and burial efficiency of organic carbon. Currently, the potential of sedimentary carbon sinks has not been fully exploited; thus, it is urgent to promote the integration of sedimentary carbon sinks into the global climate governance system through methodological innovation, mechanism deepening, and technological development, so as to provide scientific support and feasible paths for achieving the temperature control goals of the Paris Agreement.

During satellite operation, sensor malfunctions can lead to irregular strip-like missing areas in imagery, which compromises the integrity of observed information. To address this issue in geostationary satellite remote sensing imagery, a reconstruction model based on convolutional neural networks (CNN)is proposed. The model’s performance is evaluated under different combinations of temporal input data to identify the optimal configuration of consecutive temporal auxiliary data. In the auxiliary data combination, (taking the generation time of the image to be restored as the current time t), when the model takes the previous four phases (t-4, t-3, t-2, t-1)and the previous and subsequent three phases (t-3, t-2, t-1, t+1, t+2, t+3)as inputs respectively, the restoration effect is excellent and can be used for data restoration and reconstruction in real-time and delayed scenarios respectively. Compared with models that use only a single time point as auxiliary data, the proposed model utilizing multi-temporal inputs demonstrates better reconstruction results and higher accuracy. The model is also applicable to the restoration of missing information in other geostationary satellite images.

Using the measured data of extreme waves causing by 6 typhoons and 2 cold waves (caused by typhoon is called typhoon wave, caused by cold wave is called cold wave)during a one-year wave observation process in the Cangnan sea area of Zhejiang Province, the distribution and variation characteristics of wave parameters for each extreme wave as well as the typical characteristics of typhoon waves during Typhoon “Lekima” and “Mitag” were analyzed. The results show that the typhoon waves in the study sea area were significantly affected by the typhoon track and intensity, the stronger the typhoon intensity and the closer its proximity to the study area, the more significant and intense the process of typhoon waves, the higher the wave height and spectral peak density of typhoon waves. Both summer and autumn could be affected by extreme typhoons and lead to extreme typhoon waves. Extreme waves caused by cold wave occured both in winter and spring, of which intensity were directly affected by the intensity of cold waves, overall, extreme waves caused by cold wave were not as severe as typhoon waves. The duration of the impact of typhoon waves was two to three days, and the duration of the impact of extreme waves caused by cold wave was about 1 day; the maximum wave height and spectral peak density during extreme waves exhibited a synchronous development process of initially increasing and then decreasing. During the impact of Typhoon “Lekima”, the maximum wave height in the studied sea area was 10.80 m, with a maximum spectral peak density of 55.10 m²/Hz, the development and change process of wave spectrum was bimodal spectrum-unimodal spectrum-bimodal spectrum, and the development and change process of wave types was mixed waves dominated by swell-wind wave-mixed waves dominated by wind wave. During the impact of Typhoon “Mitag”, the maximum wave height in the studied sea area was 8.89 m, with a maximum spectral peak density of 36.37 m²/Hz, the wave spectrum was mainly composed of unimodal spectrum, with occasional bimodal spectrum. The wave type was mainly swell, with occasional mixed waves dominated by swell.

Oyster reefs are one of the important coastal habitats. Over the past century, oyster reefs have been severely degraded worldwide. However, with the gradual recognition of the irreplaceable ecosystem service functions of oyster reefs, the significance of oyster reef conservation and restoration has become prominent in the global efforts to restore and protect degraded coastal ecosystems. This study systematically collects and collates the distribution information of natural oyster reefs and artificially restored oyster reefs in China, summarizes the main work and achievements in the field of oyster reef conservation and restoration in China since the beginning of this century. Combined with the author’s practical experience in the Wenzhou coastal zone protection and restoration project (oyster reef), the technical process of restoration is described in detail, with emphasis on the design and structure of the inclined support composite oyster reef and the artificial seedling attachment technology used in the restoration project. Corresponding suggestions are put forward, which can provide references for future oyster reef conservation and restoration work.

In 1988, the tropical Pacific experienced a strong La Niña event, during which significant equatorial Pacific easterly wind surges were observed. Analysis based on reanalysis data indicates that the intensity of the 1988 surges reached the highest level during 1982-2020. Linear regression results show that the equatorial Pacific SST gradient contributed 70.59% to the surge intensity index in 1988. Further examination of wind field characteristics after removing the influence of the SST gradient reveals that, apart from the enhanced spatial extent of the surge event in late February, both the frequency and magnitude of surges decreased significantly from mid-March onward. To gain deeper insight into the specific causes of the easterly wind surges, a typical case analysis was then conducted to investigate the triggering mechanism of a representative event. Composite analysis confirms that the strong easterly wind surge at the end of March 1988 was closely linked to the convectively active phase of a Madden-Julian Oscillation (MJO) event over the Maritime Continent, which contributed approximately 42.96% to the surge’s formation.

Deep-water sedimentary processes are key drivers that shape seafloor topography and actively participate in marine material cycles, thereby playing a crucial role in the formation of depositional systems and material cycling along continental margins and within deep-sea basins. The transport and transformation of carbon elements and carbon-containing substances are essential for sustaining organic life and maintaining climate stability. As an important end-member reservoir in this cycle, deep-sea sediments act as efficient sinks for atmospheric greenhouse gases, exerting significant regulatory effects on climate evolution over geological timescales. This study aims to elucidate the coupling mechanisms between distinctive deep-water sedimentary processes and organic carbon burial, providing a theoretical basis for establishing the “Shelf edge-slope-deep sea basin organic matter continuous transport system” and the “Deep-water organic carbon burial pyramid model”. By comprehensively analyzing representative deep-water organic carbon burial systems in global ocean basins, this research demonstrates that turbidity currents and bottom currents are the main dynamic mechanisms enabling the continuous transport of deep-water organic matter. The (micro)biological carbon pump, turbidity current carbon pump, bottom current carbon pump, and deep stratigraphic carbon pump together form the core framework for deep-water sedimentary carbon burial. Furthermore, the factors influencing deep-water organic carbon burial outcomes exhibit hierarchical characteristics. However, current research on deep-water organic carbon burial is still in its early stages, with limited case studies and mechanistic understanding, underscoring the urgent need to strengthen research on carbon burial processes in deep-water environments.

The global ionospheric model based on the global navigation satellite systems (GNSS)reference stations is currently the most widely used global ionospheric product. The analysis and evaluation of the reliability and accuracy of the global ionospheric model during magnetic storms is a necessary prerequisite for the rational use of the model. In this study, the data of the reference stations near the South China Sea were used to verify the reliability of the ionospheric vertial total electron content (VTEC)calculated from shipboard GNSS data, and the accuracy of the global ionospheric model in the South China Sea during magnetic storms was preliminarily analyzed and evaluated using the shipboard GNSS observation data and reference stations data. The results show that the ionospheric VTEC calculated from the shipboard data and the reference stations data have the same trend of change. During the magnetic storm, the error between the global ionospheric model value in the South China Sea region of China and the shipboard observation data and the reference stations (HKSL, PIMO)data increases, and the daily average RMSE values are 41.21, 27.40 and 30.86 TECU, respectively, which indicates that the disturbance of the ionosphere by the magnetic storm activity has led to a significant decrease in the accuracy of the global ionospheric model.

Black carbon (BC), a refractory organic carbon, is produced during the incomplete combustion of biomass and fossil fuels. Globally, an estimated 3%-10% of the annual BC production ultimately buried in marine sediments. As a critical component of the inert carbon pool, its spatiotemporal distribution and source-to-sink processes are essential for understanding global carbon cycling and climate evolution. Based on published BC data from nearly 1 000 marine sediment samples worldwide, this study reveals that BC contents vary widely, from 0.02 to 9.72 mg/g, with averaging 1.06 mg/g and accounting for an average of 15.1% of total sedimentary organic carbon. Spatial patterns are controlled by sediment grain size, organic carbon content, and depositional environments while temporal variations reflect the combined influence of climate change and human activities. Current knowledge of marine sedimentary BC sources predominantly assumes terrestrial dominance, with riverine transport, atmospheric deposition, and coastal erosion as primary input pathways. However, emerging evidence indicates that BC sinking fluxes in mid- to deep-ocean layers substantially exceed known terrestrial supply. This raises the possibility of potential unidentified sources. In addition, BC degradation and recycling processes within the marine systems remain poorly understood. Future research must prioritize source-to-sink dynamics in key areas (e.g., deep-sea environment) by integrating geochemical and organic molecular isotopic techniques to resolve BC cycling mechanisms and address current budget imbalances.

Tidal flats are influenced by tides, experiencing periodic inundation and exposure, thus the inundation frequency reflects the elevation of tidal flats. This study utilizes time-series SAR satellite remote sensing data to conduct research on the remote sensing inversion method of tidal flat topography based on tidal level complementary cumulative distribution function. The key lies in proposing a new method for inundation frequency correction based on the weighting scale of remote sensing observation counts. And, based on the mathematical definition of inundation frequency, the functional relationship between inundation frequency and tidal flat elevation was explored, leading to the construction of a tidal flat topography inversion model based on the tidal level complementary cumulative distribution function. Then, the validation of the method was conducted in the Yueqing Bay. Based on the time-series Sentinel-1 satellite SAR remote sensing data, the tidal flat topographies for the periods 2019-2020 and 2021-2022 were successfully inverted. The accuracy assessment was conducted based on the corresponding period’s ICESat-2 satellite laser altimetry data. The root mean square errors (RMSE)of the tidal flat topographies for the periods 2019-2020 and 2021-2022 were 0.41 m and 0.51 m, respectively. Additionally, the RMSE of topography for the period of 2019-2020 using in-situ data was 0.48 m. The accuracy assessment suggest that the proposed method in this study can achieve high-precision tidal flat topography without field-measured topographic data. It is expected to be applicable to the monitoring of tidal flat topography in more regions.

Total nitrogen (TN)is an important indicator for measuring water eutrophication, and understanding its spatiotemporal variation is crucial for marine ecological protection. This study selected the Pearl River Estuary-Jiangmen sea area as the research area and utilized TN measurement data from 2021 to 2023, as well as the MODIS data from 2003 to 2023 and the Sentinel-3 remote sensing images from 2017 to 2023. By selecting high-correlation band combinations and constructing random forest regression models to invert TN mass concentration, the spatiotemporal variation characteristics of TN mass concentration in the region from 2003 to 2023 were analyzed. The results indicated that the inversion model achieved good fitting accuracy (R²=0.797-0.931). From 2003 to 2023, the TN mass concentration in the Pearl River Estuary-Jiangmen sea area showed an overall decreasing trend, with relatively high mass concentrations from 2003 to 2015, followed by a significant decline after 2016. TN showed obvious dry/wet seasonal variations, and the variations within the year in the estuary and shallow water areas were also significant. This study revealed the trend and distribution characteristics of TN in the study area through remote sensing inversion, which can provide a basis and reference for the formulation of pollution control measures in the coastal waters.

The interaction between deep-ocean geostrophic current and seamounts can generate near-inertial internal waves (NIWs). While the intensity of these waves relates to the seamount height, its dependence on seamount width remains elusive. This study employs a two-dimensional, non-hydrostatic numerical model based on MITgcm to investigate the interaction of geostrophic current with deep-sea seamounts and examine how differing seamount widths influence the generation and dissipation of NIWs. Our results demonstrate that topographic forcing triggers robust nonlinear wave-wave interactions along the summit edges on the downstream flank of the seamount. This process generates energetic near-inertial internal waves that radiate away and develop, facilitating energy transfer from the geostrophic mean flow to the NIWs. For a fixed seamount height, narrower seamounts induce stronger near-inertial waves, characterized by more rapid wave development and decay. Moreover, the downstream flank exhibits significantly enhanced vertical shears within the near-inertial internal waves, driving greater turbulent dissipation compared to the upstream flank. Therefore, our findings highlight that, in addition to seamount height, seamount width is also a critical factor governing the generation and subsequent evolution of near-inertial internal waves.

Island ecosystems are characterized by resource specificity and ecosystem vulnerability, thus, the scientific assessment of the impact of land use change on the carbon sequestration and other ecosystem service functions of island ecosystems is of great significance to the sustainability management of islands. The Dongtou Islands in Zhejiang Province represents a typical island ecosystem that has undergone developmental utilization such as land reclamation and conservation-restoration initiatives like the Blue Bay Project. It serves as an ideal case study for establishing assessment methods of how land use changes affecting the carbon sequestration service function of island coastal ecosystems and others, and for exploring the effectiveness of management measures. In this study, a land classification model based on XGBoost algorithm was used to obtain land use classification data of the Dongtou Islands in 12 phases (3 years as a phase)from 1988 to 2023 (with accuracy of 91.52%). On this basis, the changes in carbon sequestration amounts of major ecosystems, including woodland, salt marshes, and tidal flats, in the Dongtou Islands were calculated. A coupling coordination degree model of “economic development-land use-carbon sequestration function” was constructed by combining the socio-economic statistical data, and the degree of coupling coordination between the economy and ecosystem of the Dongtou Islands for more than 30 years was explored. The study found that from 1988 to 2023, the total land area of the Dongtou Islands increased by 34.97% due to natural silt deposition and sea reclamation efforts. The cumulative total of ecosystem carbon sequestration amount and net carbon sequestration amount for the main ecosystems amounted to 49.45×10⁴ t and 46.13×10⁴ t, respectively, basically showing an oscillating upward trend. Carbon sequestration mainly resulted from woodland and coastal wetlands (including tidal flats and salt marshes), with cumulative carbon sequestration amount of 25.44×10⁴ t and 24.01×10⁴ t, respectively. The “economic development-land use-carbon sequestration function” coupling coordination degrees of the Dongtou Islands were in a coordinated state from 2006 to 2023. Overall, the coupling coordination degree is greatly affected by the land use changes. Ecological restoration projects can enhance the comprehensive evaluation index of the land use and carbon sequestration function system, and then improve the coupling coordination degree. This study can provide a scientific theories and data foundation for the socio-economic development and ecological environmental protection planning of the Dongtou Islands.

As a pivotal intertidal blue-carbon ecosystem, the seagrass-mangrove continuum is a focal point of contemporary blue-carbon research. In contrast to individual ecosystems, the continuum facilitates lateral carbon transport and redistribution between systems via tidal forcing—a process that profoundly influences regional and even global assessments of blue carbon budgets. However, the internal carbon cycling within the continuum and the multi-interface, multi-process coupling mechanisms of carbon sequestration remain a black box, representing one of the hot topics in blue carbon research. Here we systematically synthesize current understanding of carbon cycling in the seagrass-mangrove continuum, mapping key processes—from plant photosynthetic carbon sequestration, sediment carbon accumulation to aquatic carbon transformation, and gas exchange—within a novel, dual perspective of “vertical sequestration vs. lateral transport”. Special emphasis is placed on tide-driven lateral carbon fluxes (e.g., litter fall, DOC, POC, DIC), highlighting their central role in the continuum’s carbon dynamics. Given the complexity of intertidal habitats, future research on the coupled carbon cycling mechanisms within the seagrass-mangrove continuum remains a critical and underexplored field. In particular, key processes such as plant carbon fixation mechanisms, sediment carbon accumulation, and elemental exchange urgently require further investigation.

Under the dual pressures of global change and human activities, the impact of extreme storm events on estuarine sedimentary processes and carbon sink capacity has become increasingly prominent. However, traditional single-core methods face challenges in quantitatively characterizing the erosion-deposition processes and net carbon burial effects induced by storm events. In this study, we conducted repetitive coring at a fixed station near the Dayushan Island in the Hangzhou Bay, China in 2021 (before Typhoon Chanthu) and 2022. Through analysis of sedimentary structures, grain size and radionuclides, we identified an intense erosion-deposition event triggered by Typhoon Chanthu. Combined with elemental composition and organic geochemical indicators, we further quantitatively assessed its net impact on carbon burial. The results demonstrate that despite the efficient organic carbon preservation within the storm layer, the related intense erosion resulted in a net organic carbon deficit of 1 950±523 g·m^-2. This finding highlights a preservation bias of the storm layers in sedimentary records, leading to a systematic overestimation of the storm contribution to estuarine carbon burial in studies relying on single cores. The “repetitive coring-radionuclides tracing” methodology developed in this study provides a new paradigm for accurately assessing estuarine sedimentary processes and carbon cycling under non-steady-state conditions.

The response coefficient method is one of the widely used methods for controlling the total amount of pollutants from land-based sources in harbors and gulfs. However, the current popular ocean models do not have a tracer module that simultaneously calculates the response coefficient field of multiple release points without interfering with each other. Aiming at the characteristics of the response coefficient method, this study improves the tracer module (DYE)of the three-dimensional hydrodynamic ocean numerical model FVCOM (Finite-Volume Community Ocean Model)by adding independent modules with the same functions as the original DYE module to DYE modules in parallel, so that FVCOM can simultaneously calculate the response coefficient fields of multiple release points without interfering with each other. The improved DYE algorithm was tested with one case of ideal rectangle grid and one case of ideal Xiangshan Bay grid. The results show that the advection-diffusion process of multiple point source tracers simulated by the improved algorithm does not interfere with each other, and the simulation results are the same as those of the traditional algorithm; at the same time, the computation process of the improved algorithm takes less time, and the computation efficiency of the ideal rectangle case is increased by up to 85% and that of the Xiangshan Bay case is increased by up to 78% compared to the traditional algorithm; and the improved algorithm has a higher utilization rate of the CPU process under the condition of parallel computation than those of the traditional algorithm. The use of the improved DYE to calculate the response coefficient field can shorten the total time for marine environmental capacity assessment.

Ocean waves are a fundamental component of marine dynamics, exerting significant impacts on maritime navigation and offshore operations. The wave spectrum provides an effective representation of the statistical distribution of wave energy across the frequency domain. In this study, observational data from 70 NDBC buoy stations were used to retrieve significant wave heights based on both the JONSWAP spectrum and the third-order Stokes nonlinear spectrum. Results show that, compared with the JONSWAP-based retrievals, the nonlinear spectrum achieves average improvements degree exceeding 10% in both absolute and relative errors, with maximum improvements degree of 28.54% and 22.29%, respectively, demonstrating the nonlinear spectrum’s clear advantages. Further analysis indicates that the performance degrees of the nonlinear spectrum are closely related to significant wave height, wind speed, the angle between wind and wave directions, and water depth. Specifically, the improvement degree increases with larger wave heights and stronger winds; smaller directional angle between wind and waves yields greater benefits, though wind speed exerts a much stronger influence than directional angle. In water depths shallower than 500 m, the inversion accuracies of both wave spectras are higher than those in depths deeper than 500 m. However, within the depth range of 500-5 500 m, the improvement degree in the nonlinear spectrum exceeds that in the shallow-water region, showing a linear increasing trend.

The new seawall ecological armour block is a type of face protection structure with both excellent wave dissipation performance and ecological function. In order to systematically evaluate its wave dissipation performance, this study carried out a two-dimensional wave flume physical modeling test using Zhoujiayuanshan Island in Zhoushan as the engineering background. The test systematically investigated the effects of wave period, wave height, relative water depth, wave steepness, breaking parameter, and block geometry (outer diameter and height), as well as model materials on the reflection coefficients under the action of regular waves. The results show that: firstly, the feasibility of using polypropylene random copolymer (PP-R) instead of foamed concrete in the physical modeling test is verified through the comparison experiments of nine working conditions, and the average difference in their reflection coefficient is only 1.17%. Secondly, for its wave dissipation performance, the reflection coefficient increases with increasing wave period, relative water depth and breaking parameter, and decreases with increasing wave height and wave steepness. Among all the tested conditions, the two types of blocks with outer diameter 7.5 cm-height 10 cm and outer diameter 10 cm-height 6.5 cm have the best wave dissipation performance, with average reflection coefficients of 0.395 and 0.382, respectively. Finally, the reflection coefficient formula for the six types of blocks is fitted based on the experimental data in this study. The formula has a root mean square error (RMSE) of 0.106 9, which is of high accuracy and our study can provide a certain reference for related engineering design.

River deltas are critical global sinks for organic carbon (OC). To elucidate their evolutionary patterns under natural and anthropogenic influences, this study systematically reconstructs the OC burial history of the Changjiang Delta since the mid-to-late Holocene (8 ka BP), based on chronological, sedimentological, and organic geochemical data from 50 boreholes. The results revealed that the sediment accumulation rate was the core driver controlling the OC burial flux, with the two showing a strong positive correlation (r²=0.87). However, a significant decoupling existed between the OC burial flux and the total OC content, with the latter remaining stable within a low range of 0.41%-0.52% throughout the study period. This was primarily constrained by the dual effects of clastic dilution and particle size sorting. The provenance of OC showed a distinct phased evolution: from 8 to 2 ka BP, source variations were mainly driven by natural factors, with sea-level rise (8-5 ka BP) and the weakening of the East Asian Summer Monsoon (5-4 ka BP) successively leading to a decrease in the terrestrial OC fraction. Since 2 ka BP, human activities had become the dominant factor, profoundly reshaping the delta’s geochemical signals by altering sediment provenance zones within the catchment. This study unveils the complete process of the Changjiang Delta’s carbon sink function transitioning from a dynamic equilibrium under a natural background to being intensely disturbed in the Anthropocene, providing crucial scientific insights for understanding and predicting the vulnerability of deltaic carbon reservoirs in the context of global change.