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The Bohai Sea is the only inland sea in China and serves as an important carrier for the Bohai Sea Economic Zone. However, it is also one of the areas with serious marine environmental pollution. This paper selects the policy text concerning Marine environmental pollution control issued by the central and local governments from 1996 to 2022 as the research object. Based on the three policy instruments of government environmental regulation, market incentive mechanisms and public participation, and using a content analysis method to encode and quantify the text content, it was found that the Bohai Sea marine environmental governance suffers from issues such as a singular concept of the use of policy instruments, imbalance in the proportion of their use, and insufficient supervision in the event of their use. Consequently, it is recommended to adopt diversified policy concepts, optimize the structure of policy instruments, and strengthen in-process supervision in the governance of the Bohai Sea marine environment. [ABSTRACT FROM AUTHOR]

Based on the geological and geophysical data of Mesozoic oil-gas exploration in the sea area of Bohai Bay Basin and the discovered high-yield volcanic oil and gas wells since 2019, this paper methodically summarizes the formation conditions of large- and medium-sized Cretaceous volcanic oil and gas reservoirs in the Bohai Sea. Research shows that the Mesozoic large intermediate-felsic lava and intermediate-felsic composite volcanic edifices in the Bohai Sea are the material basis for the formation of large-scale volcanic reservoirs. The upper subfacies of effusive facies and cryptoexplosive breccia subfacies of volcanic conduit facies of volcanic vent-proximal facies belts are favorable for large-scale volcanic reservoir formation. Two types of efficient reservoirs, characterized by high porosity and medium to low permeability, as well as medium porosity and medium to low permeability, are the core of the formation of large- and medium-sized volcanic reservoirs. The reservoir with high porosity and medium to low permeability is formed by intermediate-felsic vesicular lava or the cryptoexplosive breccia superimposed by intensive dissolution. The reservoir with medium porosity and medium to low permeability is formed by intense tectonism superimposed by fluid dissolution. Weathering and tectonic transformation are main formation mechanisms for large and medium-sized volcanic reservoirs in the study area. The low-source "source-reservoir draping type" is the optimum source-reservoir configuration relationship for large- and medium-sized volcanic reservoirs. There exists favorable volcanic facies, efficient reservoirs and source-reservoir draping configuration relationship on the periphery of Bozhong Sag, and the large intermediate-felsic lava and intermediate-felsic composite volcanic edifices close to strike-slip faults and their branch faults are the main directions of future exploration. [ABSTRACT FROM AUTHOR]

The X oilfield is the first sandstone reservoir under the influence of igneous rock, which is discovered and put into development in Bohai Sea. Compared with the conventional sandstone reservoir, the oilfield is affected by magmatic activity, the reservoir heterogeneity is serious and the micro pore structure is complex, which results in the poor correlation between mobility calculated by traditional methods and specific oil production index. In order to predict oil well productivity and guide oilfield well location deployment, the quantitative transformation of sandstone reservoir affected by igneous rock is studied in this paper. According to the distribution mode of igneous rock in the reservoir, a permeability model of quantitative characterization for sandstone reservoir permeability is established, in which the influences of heat conduction, reservoir skeleton deformation and stress sensitivity are considered, and then the igneous rock influence on the ground temperature field of surrounding rock is simulated by ANSYS software. According to the relationship between porosity and permeability, the quantitative transformation effect of igneous rock thermal effect on sandstone reservoir is quantitatively characterized. The reservoir temperature field variation law, different baking types and igneous rock thickness influence on the transformation degree of sandstone reservoir are analyzed. Finally, the X oilfield is taken as an example to verify the research method, and the second batch of wells location deployment is successfully guided. The results show that the thermal effect of igneous rock reduces the permeability of reservoir, and the temperature of reservoir increases first and then decreases with time, the rising speed is faster than the falling speed, with the increase in distance from igneous rock, the maximum temperature of reservoir shows a downward trend, in the case of baking on both sides, the heat of igneous rock is greater, which makes the temperature of surrounding reservoir rise more, and the transformation effect on reservoir is more obvious. The influence range of igneous rock thickness on permeability is basically the same, but with the increase in thickness, igneous rock has a greater influence on surrounding rock. The research example of the X oilfield shows that the existence of igneous rock reduces the reservoir physical properties of development wells by 1.2–5.9 times. The correlation between igneous rock physical properties and specific oil production index corrected by this method can reach 0.9478. By avoiding igneous rock, the comparative production of the second batch of development wells is 1.5 times that of the first batch of development wells. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a radionuclide dispersion model for the nuclear power plants in the Bohai, Yellow, and East China seas (BYECS) characterized by high turbidity and multi-scale circulations, focusing on the comparison of dispersion processes of 137Cs depending upon, in particular, the suspended sediment concentration and erosion/sedimentation processes. The simulations were carried out using a multi-fraction sediment transport model embedded in the semi-implicit Eulerian–Lagrangian finite-element coupled wave-circulation model linked with the model of radionuclide transport, which describes the key radionuclide transfer processes in the system of water–multi-fraction sediments. In contrast to the Eulerian models used for hydrodynamics and sediment transport processes, the Lagrangian technique was applied to simulate the transport of radionuclides. The simulation results for total suspended concentration agreed with in situ measurements and the Geostationary Ocean Color Imager data. The results of the simulation of hypothetical releases of 137Cs from four nuclear power plants (NPPs) placed in BYECS essentially differ from the real release of activity in the Pacific Ocean shelf due to the Fukushima Daiichi accident, which took place at the same time and released activity that was similar. The total amount of bottom contamination of 137Cs in releases from the Sanmen, Hanbit, and Hongyanhe NPPs was about 40% of dissolved component, and the total amount of suspended component was about 20% of dissolved component, in contrast with the Fukushima Daiichi accident, where the particulate component was only 2%. The results demonstrate the importance of erosion processes in the budget of 137Cs in shallow areas around the Sanmen and Hanbit NPPs, where strong wind and tidal currents took place. [ABSTRACT FROM AUTHOR]

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The Bohai Sea, known for being the lowest latitude seasonally frozen sea area in the world, experienced severe ice conditions with a 30-year recurrence period during the winter of 2009-2010. Water-sediment flux is a crucial parameter for water quality management in marine environment. Using a highly accurate three-dimensional hydrodynamic and sediment transport numerical model, the significant wave height (Hs), current velocity, suspended sediment concentration (SSC) and water-sediment flux in the Bohai Sea during ice-covered and ice-free conditions are compared. Our findings indicate that the current velocity and sediment resuspension decrease under the ice coverage, but increase at the edge of the ice. The net outflow tidal flux (TF) in winter under ice-free conditions accounts for 24.5% of the whole year. The net outflow TF increases by 32.7% during ice-covered conditions, primarily due to the pressure difference between high air pressure superimposing heavy sea ice in the northwest Bohai Sea and the low air pressure in Bohai Strait, resulting in increased ebb velocity and decreased flood velocity. The net outflow suspended sediment flux (SSF) during ice-free conditions in the winter is 2.32×109 kg, while SSF increases by 1.24 times during ice-covered conditions, leading to worse water quality in the outer sea. The decrease of TF in the southern part of the Bohai Strait and the reduction of suspended sediment concentration by nearly 15 mg/l lead to the significant decrease in SSF. This study has significance guiding value for understanding the source-sink sedimentation system and water quality research in East China Sea. [ABSTRACT FROM AUTHOR]

As a new type of pollutants in the marine environment, microplastics have attracted increasing attention from scientific researchers and environmental protection workers in China and abroad. However, for the microplastic pollution in sea areas in China, there are a very limited number of studies on its current status and few reviews of research on the microplastics. This paper reviews the surveys and researches of microplastics in the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea, and main estuaries in China carried out in recent years and proposes an outlook for future work, aiming to provide research suggestions and solutions for ecological protection against microplastic pollution in sea areas in China. Previous studies have shown that microplastics are widely distributed in water bodies and sediments in sea areas and major estuaries in China. The Pearl River Estuary, in the South China Sea suffers the most serious microplastic pollution, followed by the Bohai Sea. In contrast, the microplastic pollution in the Yellow Sea and the East China Sea is comparatively slight. Microplastics in sea areas in China are mainly fibrous and are concentrated in offshore areas with developed industry and a dense population (especially around estuaries and bays). In addition, they are widely affected by human activities, such as shipping, aquaculture, industry, and sewage discharge. Here the authors suggest unifying measurement units and research methods and developing related standard systems to carry out researches related to microplastics. Furthermore, this paper also suggests further deepening researches on both the source-sink process of microplastics and nanoscale microplastics while enhancing the development and implementation of related policies, aiming to promote researches and control of microplastics in sea areas in China.© 2022 China Geology Editorial Office.

Based on the geological and geophysical data of Mesozoic oil-gas exploration in the sea area of Bohai Bay Basin and the discovered high-yield volcanic oil and gas wells since 2019, this paper methodically summarizes the formation conditions of large- and medium-sized Cretaceous volcanic oil and gas reservoirs in the Bohai Sea. Research shows that the Mesozoic large intermediate-felsic lava and intermediate-felsic composite volcanic edifices in the Bohai Sea are the material basis for the formation of large-scale volcanic reservoirs. The upper subfacies of effusive facies and cryptoexplosive breccia subfacies of volcanic conduit facies of volcanic vent-proximal facies belts are favorable for large-scale volcanic reservoir formation. Two types of efficient reservoirs, characterized by high porosity and medium to low permeability, as well as medium porosity and medium to low permeability, are the core of the formation of large- and medium-sized volcanic reservoirs. The reservoir with high porosity and medium to low permeability is formed by intermediate-felsic vesicular lava or the cryptoexplosive breccia superimposed by intensive dissolution. The reservoir with medium porosity and medium to low permeability is formed by intense tectonism superimposed by fluid dissolution. Weathering and tectonic transformation are main formation mechanisms for large and medium-sized volcanic reservoirs in the study area. The low-source “source-reservoir draping type” is the optimum source-reservoir configuration relationship for large- and medium-sized volcanic reservoirs. There exists favorable volcanic facies, efficient reservoirs and source-reservoir draping configuration relationship on the periphery of Bozhong Sag, and the large intermediate-felsic lava and intermediate-felsic composite volcanic edifices close to strike-slip faults and their branch faults are the main directions of future exploration.

Introduction: Bivalve aquaculture is an important pillar of China's fisheries, with over 1 million tonnes of scallop shells produced annually. However, most of these shells are directly discarded into the sea, leading to continuous pollution of the marine and coastal environments, especially the coast of Yantai in the Bohai Sea where a large number of discarded scallop shell have accumulated. Methods: To trace the fate of scallop shells in the ocean, this study established a model for the transport of scallop shells, coupling a two-dimensional tidal current model using the adjoint method with a Lagrangian particle model. By simulating nested tidal models, the distribution of tidal residual current in the Yantai coastal region was obtained. Then, a Lagrangian particle model was used to track the transport pathways of pollutants in the sea. Results: Driven by the residual current calculated from the tidal model with the actual situation, possible pollutant release areas were inferred. The results of Lagrangian particle tracking experiments indicate that pollutants were released from the upstream accumulation area, specifically the area near Penglai Hulushan, confirming previous speculation. Discussion: The scallop shells transport model can accurately simulate the spatiotemporal profile of scallop shells, which is helpful for managing scallop shell resources and improving the level of shell reuse. [ABSTRACT FROM AUTHOR]

The Bohai Sea and its surrounding areas are rich in oil and natural gas and play an important role in industry, agriculture and the economy. However, the Bohai Sea suffers severely from sea ice in the winter. While previous research has predominantly focused on methods for retrieving sea ice parameters in the Bohai Sea, analyses of their long-term statistical patterns have been limited. The Geostationary Ocean Color Imager (GOCI) is the first geostationary satellite for ocean color remote sensing, offering high spatial and temporal resolution, which greatly facilitates the extraction of Bohai Sea ice parameters. Utilizing GOCI data, we systematically extracted relevant sea ice parameters for the Bohai Sea region from 2011 to 2021. These parameters include sea ice concentration, sea ice thickness, and sea ice drift. We conducted a comprehensive statistical analysis of the long-term sea ice changes in the Bohai Sea and found that the development process of winter sea ice area is different from the sea ice thickness, and the direction of sea ice drift is basically unchanged. Then we developed statistical models linking sea ice parameters with ocean dynamic factors such as temperature, wind, and drift currents. Among them, the correlation coefficient between the predicted value and the measured value of the sea ice area model is the highest, reaching 0.8382. Furthermore, we examined the previously unexplored relationship between daily sea ice area, sea ice thickness, and accumulated temperature with their respective starting temperatures and accumulation periods. This study provides critical data to support Bohai Sea ice monitoring and marine environmental research. The results of this study contribute to a better understanding of sea ice change trends in the Bohai Sea and inform the development of disaster prevention and mitigation measures. [ABSTRACT FROM AUTHOR]

The impacts of Stokes drift and sea-state-dependent Langmuir turbulence (LT) on the three-dimensional ocean response to a tropical cyclone in the Bohai Sea are studied through two-way coupled wave-current simulations. The Stokes drift is calculated from the simulated wave spectrum of the wave model, Simulating Waves Nearshore (SWAN), and then input to the Princeton Ocean Model with the generalized coordinate system (POMgcs) to represent the Langmuir effect. The Langmuir circulation is included in the vertical mixing of the ocean model by adding the Stokes drift to the shear of the vertical mean current and by including LT enhancements to the Mellor-Yamada 2.5 turbulent closure submodel. Simulations are assessed through the case study of Typhoon Masta in 2005 with a set of diagnostic experiments that incorporated different terms of Stokes production (SP) respectively. It is shown that with the consideration of SP, a deeper mixed layer, an enhanced vertical mixing coefficient KMS, and a more accurate representation of the vertical temperature distribution could be derived. Moreover, the effect of LT in elevating the turbulence mixing is stronger than that of Coriolis Stokes force (CSF) and Craik-Leibovich vortex force (CLVF). LT has a greater influence on the vertical mixing during typhoon than that in normal weather. [ABSTRACT FROM AUTHOR]

Studies have investigated heavy metal (HM) contamination in the Bohai Sea, but primarily in seawater and associated sediments, or in single rivers. For the first time, 31 major rivers discharging into the Bohai Sea were analyzed, along with 27 uniformly distributed coastal seawater samples and selected invertebrates. The elements measured were As, Cd, Cr, Cu, Ni, Pb, V, and Zn. We calculated the 'geo-accumulation index', the 'metal enrichment factor', and the 'contamination factor', coupled with the 'pollution load index', and our findings suggested low-grade HM pollution, although two conspicuous associations of elements were found to stand out in particular: One is a combination of As, Cu, Cr, and V in seawater samples that may indicate pollution from intensive ship traffic. The other shows a significant pattern of Cr, Pb, and Zn in water samples from rivers discharging between Yantai and Weihai on the Shandong Peninsula at the south edge of the Bohai Sea. This is primarily a farming area, with a moderate share of industrial enterprises. Investigations including fertilizers and pesticides point to agricultural practices and textile printing/chrome tanneries as the causes of contamination. Overall, a significant decline was found in the HM load in the rivers, apart from those discharging into the Yellow Sea section. [ABSTRACT FROM AUTHOR]

Sea-ice mapping using Synthetic Aperture Radar (SAR) in the melt season poses challenges, primarily due to meltwater complicating the distinguishability of sea-ice types. In response to this issue, this study introduces a novel method for classifying sea ice during the Bohai Sea's melting period. The method categorizes sea ice into five types: open water (OW), gray ice (Gi), melting gray ice (GiW), gray–white Ice (Gw), and melting gray–white Ice (GwW). To achieve this classification, 51 polarimetric features are extracted from L-, S-, and C-band PolSAR data using various polarization decomposition methods. This study assesses the separability of these features among different combinations of sea-ice type by calculating the Euclidean distance (ED). The Support Vector Machine (SVM) classifier, when employed with single-frequency polarimetric feature sets, achieves the highest accuracy for OW and Gi in the C-band, GiW in the S-band, and Gw and GwW in the L-band. Remarkably, the C-band features exhibit the overall highest accuracy when compared to the L-band and S-band. Furthermore, employing a multi-dimensional polarimetric feature set significantly improves classification accuracy to 94.55%, representing a substantial enhancement of 9% to 22% compared to single-frequency classification. Benefiting from the performance advantages of Random Forest (RF) classifiers in handling large datasets, RF classifiers achieve the highest classification accuracy of 95.84%. The optimal multi-dimensional feature composition includes the following: L-band: SE, SEI, α ¯ , Span; S-band: SEI, SE, Span, PV-Freeman, λ1, λ2; C-band: SE, SEI, Span, λ3, PV-Freeman. The results of this study provide a reliable new method for future sea-ice monitoring during the melting season. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) plays a pivotal role in sustaining marine ecosystems. The Bohai Sea in China is a semi-enclosed sea, and oxygen-deficit events occur from time to time due to human activities. At present, there is a notable absence of any convenient and precise method for obtaining three-dimensional spatial data on DO, and the exploration of the physical mechanisms influencing oxygen deficit remains incomplete. This investigation uses the linear radial basis function (RBF-Linear) fitting method to conduct three-dimensional spatial interpolation for DO, which demonstrates minimal inaccuracy. Then, the RBF-Linear fitting method is utilized to collect a comprehensive three-dimensional spatial dataset encompassing temperature, salinity, and DO in the Bohai Sea in August from 2016 to 2018. The results indicate discernible interannual variations in the extent, area, and distribution of oxygen deficiency during summer in the Bohai Sea. Mechanism analysis reveals that intense precipitation episodes and an increase in wind stress curl exacerbate oxygen depletion. Additionally, the degree, location, and area of the two oxygen-deficit cores (off the Yellow River Estuary and off the Qinhuangdao) in the Bohai Sea are influenced by several factors, including current velocity, direction, local circulation position, and net horizontal transport rate. Furthermore, the study suggests that oxygen deficiency in the Bohai Sea region is currently in its early stages, with a limited degree of injury and a restricted range of influence. The use of a three-dimensional spatial interpolation method to create a complete DO field in three-dimensional space simplifies the research challenges associated with marine oxygen deficit. Moreover, this study holds particular significance for guiding the development of marine fisheries. [ABSTRACT FROM AUTHOR]

Dalledonne, G. L., and Mayerle, R., 2016. Modelling of storm impacts on the Shandong peninsula coast. This paper presents results of the investigation of the effect of storms on the morphodynamics of the Yantai coastal areas in the Shandong Peninsula, China. A two-dimensional depth integrated morphodynamic model for prediction of the morphological changes during extreme events was developed and applied. The model covers the entire Bohai Sea with increasing grid resolution towards the coastal areas near Yantai. Calibration and validation using tidal constituents and measured water levels and current velocities showed that the model is capable of predicting the hydrodynamics in good agreement with observations. Emphasis was given to the proper description of the spatial distribution of the seabed sediments and bed stratigraphy. The 20 most severe storms observed in the region from 2000 to 2013 were identified and reconstructed. Storm surges with increases in mean sea level of up to 1.7 m and significant wave heights up to 4.1 m were considered. The results showed that during the storms the levels of energy are mainly due to waves and tidal currents are only relevant at the capes and some channels and straits along the Shandong Peninsula. The resulting morphological changes indicated that although there is an overall loss of seabed material, particularly during the peak of the storms, the beaches near Yantai recover quite quickly just a few days after the extreme events. [ABSTRACT FROM AUTHOR]

In this paper, as a case study in the Bohai Sea, a split-window model is established for retrieving total suspended sediment matter (TSM) from MODIS data. The split-window model is initialized using the MODIS-derived water-leaving reflectance and field-measured TSM concentration. Based on the results of the analyses, it is shown that the split-window model may be used for estimating TSM concentration in the Bohai Sea without requiring accurate atmospheric correction for the MODIS dataset, regardless of the fact that the model output would be influenced by the inherent noise at the MODIS near-infrared wavelengths in cases with low TSM concentration. Finally, the split-window model is used to produce TSM images from MODIS data obtained on September 22, 2005. As expected, the TSM concentration decreases from the coastal zone in all directions, with the sharpest decline in the direction of the Central Bohai Sea. These distribution characteristics of the TSM concentrations are caused primarily by wind waves, Stoke drifts, tidal currents, river discharge, and other factors. [ABSTRACT FROM PUBLISHER]

This paper presents an incremental variational method to assimilate the observed tidal harmonic constants using a frequency domain linearized shallow water equation. A cost function was constructed with tidal boundary conditions and tidal forcing as its control (independent) variables. To minimize the cost function, optimal boundary conditions and tidal forcing were derived using a conventional dual 4-Dimensional Variational (4D-Var) Physical-space Statistical Analysis System. The tangent linear and adjoint model were solved by using a finite element method. By adapting the incremental form, the variational method streamlines the workflow to provide the incremental correction to the boundary conditions and tidal forcing of a hydrodynamic forward model. The method was tested for semi-diurnal M2 tides in a regional sea with a complex tidal system. The results demonstrate a 65–72% reduction of tidal harmonic constant vector error by assimilating the observed M2 tidal harmonic constants. In addition to improving the tides of a hydrodynamic model by optimizing boundary conditions and tidal forcing, the method computes a spatially varying uncertainty of individual tidal constituents in the model. The method provides a versatile tool for mapping the spatially continuous tides and currents in coastal and estuarine waters by assimilating the harmonic constants of individual tidal constituents of observed tides and currents. [ABSTRACT FROM AUTHOR]

The Bohai Sea is a semi-enclosed shallow shelf sea that has undergone a unique sediment source-to-sink process in the past. Despite this, our knowledge about the sediment budget, existence of depocenters and the factors controlling depocenter formation during the Holocene remains limited. This paper aims to address these gaps by estimating the Holocene marine deposit thickness and sediment budget in the Bohai Sea using high-resolution subbottom profiles. The results reveal that the mean thickness of Holocene marine deposits is approximately 7.8 m and a maximum thickness of 28 m was found in Jinzhou Bay. The Highstand System Tracts (HST) have a mean thickness of approximately 5.4 m and a maximum thickness of 25 m observed in the Jinzhou Bay. On the other hand, the Transgressive System Tracts (TST) have a mean thickness of approximately 2.5 m and a maximum thickness of 7 m in the north of the Laizhou Bay. The total accumulation in the Bohai Sea is estimated to be ∼713.97 × 109 tons, consisting of 489.28 × 109 tons from the HST and 224.69 × 109 tons from the TST. Three deposit centers were identified and estimated to be approximately 299 × 109 tons, accounting for approximately 42 % of the total Bohai Sea sediments. The development of Holocene marine deposit centers was mainly influenced by the Tanlu Fault zone and water circulations. Based on preliminary estimates, it is suggested that roughly half of the sediments dispersed from the estuaries are preserved on the Bohai Sea shelf since the maximum flooding (∼7000 cal yr BP). This research provides valuable insights for the post-glacial sedimentary and geomorphic evolution of the Bohai Sea. • Holocene marine accumulation in the Bohai Sea is estimated to be ∼713.97 × 109 tons. • Accumulation in HST is of ∼489.28 × 109 tons and that in TST is of ∼224.69 × 109 tons. • Three depocenters were identified and account for ∼42 % of the total accumulation. • Roughly half of the sediments were preserved on the shelf over the past 7000 years. [ABSTRACT FROM AUTHOR]

The safety of winter activities in the Bohai Sea requires more detailed information on ice characteristics and a more refined ice zone division. In the present study, 1/12°-resolution sea ice characteristic data were obtained based on the NEMO-LIM2 ice–ocean coupling model that assimilated MODIS satellite sea ice observations from the years of 2005 to 2022 to acquire new sea ice hindcasting data. On this basis, the ice period, ice thickness, ice concentration, ice temperature, ice salinity, and design ice thickness for different return periods in the 1/4°-resolution refined zoning were analyzed, which were then compared with the sea ice characteristics in the previous 21-ice-zone standard. The distribution of ice temperature and ice salinity was closely related to the distribution of ice thickness. The results of ice period, ice thickness, and ice concentration, as well as design ice thickness for different return periods, and the comparison with the previous 21-ice-zone standards, showed that the ice condition on the west coast of the Bohai Sea has significantly reduced. [ABSTRACT FROM AUTHOR]

Data-driven predictions of marine environmental variables are typically focused on single variables. However, in real marine environments, there are correlations among different oceanic variables. Additionally, sea–air interactions play a significant role in influencing the evolution of the marine environment. Both internal dynamics and external drivers contribute to these changes. In this study, a data-driven model is proposed using sea surface height anomaly (SSHA), sea surface temperature (SST), and sea surface wind (SSW) in the Bohai Sea. This model combines multivariate empirical orthogonal functions (MEOFs) with long and short-term memory (LSTM). MEOF analysis is used on the multivariate dataset of SSHA and SST, considering the correlation among sea surface variables. SSW is introduced as a predictor to enhance the predictability of the multivariate sea surface model. In the case of the Bohai Sea, the comparative tests of the model without wind field effect, the fully coupled model, and the proposed prediction model were carried out. MEOF analysis is employed in comparative experiments for oceanic variables, atmospheric variables, and combined atmospheric and oceanic variables. The results demonstrate that using wind field as a predictor can improve the forecast accuracy of SSHA and SST in the Bohai Sea. The root mean square errors (RMSE) for SSHA and SST in a 7-day forecast are 0.016 m and 0.3200 °C, respectively. [ABSTRACT FROM AUTHOR]

In the application of ocean color remote sensing, remote sensing reflectance spectral (Rrs(λ)) is the most important and basic parameter for the development of bio-optical algorithms. Atmospheric correction of ocean color data is a key factor in obtaining accurate water Rrs(λ) data. Based on the QA (quality assurance) score spectral quality evaluation system, the quality of Rrs(λ) spectral of GOCI (Geostationary Ocean Color Imager) obtained from four atmospheric-correction algorithms in the Bohai Sea were evaluated and analyzed in this paper. The four atmospheric-correction algorithms are the NASA (National Aeronautics and Space Administration) standard near-infrared atmospheric-correction algorithm (denoted as Seadas—Default), MUMM (Management Unit of the North Sea Mathematical Models, denoted as Seadas—MUMM), and the standard atmospheric-correction algorithms of KOSC GOCI GDPS2.0 (denoted as GDPS2.0) and GDPS1.3 (denoted as GDPS1.3). It is shown that over 90% of the Rrs(λ) data are in good quality with a score ≥4/6 for the GDPS1.3 algorithm. The probability of Rrs(λ) with a QA score of 1 is significantly higher for the GDPS1.3 algorithm (57.36%), compared with Seadas—Default (37.91%), Seadas—MUMM (35.96%), and GDPS2.0 (33.05%). The field and MODIS measurements of Rrs(λ) were compared with simultaneous GOCI Rrs(λ), and they demonstrate that the QA score system is useful in evaluating the spectral shape of Rrs(λ). The comparison results indicate that higher QA scores have higher accuracy of the Rrs band ratio. The QA score system is helpful to develop and evaluate bio-optical algorithms based on the band ratio. The hourly variation of QA score from UTC 00:16 to 07:16 was investigated as well, and it demonstrates that the data quality of GOCI Rrs(λ) can vary in an hour scale. The GOCI data with high quality should be selected with caution when studying the hourly variation of biogeochemical properties in the Bohai Sea from GOCI measurements. [ABSTRACT FROM AUTHOR]

In shallow waters, tidal friction at seabed is proportional to the square of tidal current velocity, and can induce shallow water tides. M 2 , S 2 and N 2 are the most important semi-diurnal constituents in the Bohai and Yellow Seas, and their interaction through the frictional nonlinearity can induce shallow water tides, with 2MS 2 and 2MN 2 being the most representative constituents. In this paper, we analyze the observed hourly records at 27 tidal stations along the coast of the Bohai and Yellow Seas and obtain harmonic constants of μ 2 and L 2 constituents, which can be separated into astronomical parts μ 2 ′ and L 2 ′ , and frictional nonlinearity-induced parts, 2MS 2 and 2MN 2 , respectively. A numerical model is also performed to simulate the constituents 2MS 2 and 2MN 2. It shows a fairly good agreement between the model and observations in the harmonic constants of constituents 2MS 2 and 2MN 2. The cotidal charts of 2MS 2 and 2MN 2 are presented. It is found that the frictional nonlinearity-induced shallow water tides can significantly reduce the main fortnightly and monthly modulations. • Harmonic constants of μ 2 and L 2 constituents are obtained from 27 tide gauges. • The nonlinear interplay between M 2 , S 2 and N 2 tides can induce 2MS 2 and 2MN 2 tides. • Nonlinearity-induced shallow water tides reduce main fortnightly and monthly modulations. [ABSTRACT FROM AUTHOR]

Suspended particulate matter is a crucial component in estuaries and coastal oceans, and a key parameter for evaluating their water quality. The Bohai Sea, a huge marginal sea covering an expanse of 77,000 km² and constantly fed by numerous sediment-laden rivers, has maintained a high level of total suspended particulate matter (TSM). Despite the widespread development and application of TSM retrieval algorithms using commonly available satellite data like Landsat, Sentinel, and MODIS, developing TSM retrieval algorithms for China's Gaofen (GF) series (GF-6 and GF-1) in the Bohai Sea is still a great challenge, mainly due to the limited applicability of empirical algorithms. In this study, 259 in situ measured-TSM samples were collected for algorithm development. The remote sensing reflectance (Rrs) curve demonstrates prominent peaks between 550 and 580 nm. Through conversion to remote sensing reflectance, it was found that single-band data had a weak correlation with TSM, reaching a maximum correlation of 0.44. However, by combining bands of band ratio calculations, the correlation was enhanced. Particularly, the blue and green band equivalent Rrs ratio had a correlation coefficient of 0.81 with TSM, and the proposed TSM inversion exponential algorithm developed based on this factor obtained an R-squared (R²) value of 0.76 and a mean relative error (MRE) of 32.24%. Analysis results indicated that: (1) there are spatial variations in the TSM within the Bohai Sea, Laizhou Bay, and the Yellow River estuary, with higher levels near the coast and lower levels in open waters. The Yellow River estuary experiences seasonal fluctuations higher TSM during spring and winter, and lower variations during summer and autumn, and (2) the dynamics of TSM are affected by Yellow River runoff, with increased runoff leads to higher TSM levels and expanded turbid zones. This study proposes a new algorithm to quantify TSM evolutions and distributions in the Bohai Sea and adjacent regions using China's Gaofen imageries. [ABSTRACT FROM AUTHOR]

Abstract The X oilfield is the first sandstone reservoir under the influence of igneous rock, which is discovered and put into development in Bohai Sea. Compared with the conventional sandstone reservoir, the oilfield is affected by magmatic activity, the reservoir heterogeneity is serious and the micro pore structure is complex, which results in the poor correlation between mobility calculated by traditional methods and specific oil production index. In order to predict oil well productivity and guide oilfield well location deployment, the quantitative transformation of sandstone reservoir affected by igneous rock is studied in this paper. According to the distribution mode of igneous rock in the reservoir, a permeability model of quantitative characterization for sandstone reservoir permeability is established, in which the influences of heat conduction, reservoir skeleton deformation and stress sensitivity are considered, and then the igneous rock influence on the ground temperature field of surrounding rock is simulated by ANSYS software. According to the relationship between porosity and permeability, the quantitative transformation effect of igneous rock thermal effect on sandstone reservoir is quantitatively characterized. The reservoir temperature field variation law, different baking types and igneous rock thickness influence on the transformation degree of sandstone reservoir are analyzed. Finally, the X oilfield is taken as an example to verify the research method, and the second batch of wells location deployment is successfully guided. The results show that the thermal effect of igneous rock reduces the permeability of reservoir, and the temperature of reservoir increases first and then decreases with time, the rising speed is faster than the falling speed, with the increase in distance from igneous rock, the maximum temperature of reservoir shows a downward trend, in the case of baking on both sides, the heat of igneous rock is greater, which makes the temperature of surrounding reservoir rise more, and the transformation effect on reservoir is more obvious. The influence range of igneous rock thickness on permeability is basically the same, but with the increase in thickness, igneous rock has a greater influence on surrounding rock. The research example of the X oilfield shows that the existence of igneous rock reduces the reservoir physical properties of development wells by 1.2–5.9 times. The correlation between igneous rock physical properties and specific oil production index corrected by this method can reach 0.9478. By avoiding igneous rock, the comparative production of the second batch of development wells is 1.5 times that of the first batch of development wells.

Spatiotemporal information is crucial for cetacean research and conservation, particularly for wide-ranging and migratory species. Sperm whales (Physeter macrocephalus) are distributed worldwide in deep oceans; however, little is known about the species in the western margin of the Pacific Ocean. Here, we examined the available information related to the occurrence, distribution, and potential habitats of sperm whales in the waters off China. Historical whaling information (18th-20th century) indicates that sperm whales have been captured in the East China Sea (ECS) and South China Sea (SCS). Furthermore, sporadic strandings have been recorded since the 1910s, and more frequently from 1990 onwards. Since 1990, accidental sightings have been documented in the eastern ECS, northeastern and southern SCS, and their adjacent waters. More recently (2019-2022), field encounters have been reported in dedicated ship-based investigations in the Xisha and Nansha waters, providing robust evidence of the regular existence and potential residency of sperm whales in the northwestern and central areas of the SCS. Female nursery groups suggest that the Xisha waters might be an important nursing ground for sperm whales. Satellite tracking data from four adults showed that sperm whales in the SCS might display both fine-scale and long-distance movements. Taken together, it appears that sperm whales are currently active in the waters off China, and that deep waters (depth >200 m) in the ECS and SCS may provide the species with critical habitats. This review provides crucial baseline information on sperm whales in the waters off China, which may help to facilitate future research efforts and conservation initiatives for the species at national and cross-regional scales. More field investigations and other monitoring approaches including acoustic monitoring, biologging, photo-identification, and genetics are required to reveal the distribution, movement, and habitat use patterns of sperm whales in these waters. [ABSTRACT FROM AUTHOR]

The ecosystem-based management of nearshore waters requires synthesis of spatial data on the distribution of ecological conditions and intensity of anthropogenic perturbations, and the overlay of their effects on the ecosystem health. An assessment framework for ecosystem health incorporating 4 components namely vigor, organization, resilience and maintenance was proposed in this paper, based on which an analytical approach was developed to quantify the integrated effects of island mass and anthropogenic pressures on the waters of nearshore archipelago. The southern waters of Miaodao Archipelago, which are located in the intersection of the Bohai Sea and the Yellow Sea, China, were taken as a typical example to acquire the spatial heterogeneity of the ecosystem health and its sensitivity to multiple anthropogenic pressures. Results indicated that there was a relatively significant performance of the spatial heterogeneity for the ecosystem health. It presented that the interisland waters were poorer health than the external waters, and the waters adjacent to the continent functioned less well than those in a relatively open area. This phenomenon was primarily determined by the performance of vigor as well as resilience of ecosystem. For the 4 components of ecosystem health, there were an obvious spatial heterogeneity of vigor as well as the resilience, a seasonal succession of organization, and a spatiotemporal uniformity of maintenance. Moreover, the ecosystem health was more sensitive to the stressors of inland activities and coastline exploitation especially in the waters of Miaodao Bay and Changdao Port. The analytical process and resulting maps provide flexible tools for regional efforts to implement ecosystem-based management in the waters of archipelago and further nearshore waters so as to promote their sustainable development. [ABSTRACT FROM AUTHOR]

The rational assessment of regional energy distribution provides a scientific basis for the selection and siting of power generation units. This study, which focused on the Bohai Sea, set 31 research coordinate points in the Bohai sea for assessing the potential/trends of wave energy flux (WEF). We applied a point-to-point time series prediction method which modelled the different geographical coordinate points separately. Subsequently, we evaluated the performance of three traditional machine learning methods and three automated machine learning methods. To estimate WEF, the best model was applied to each research coordinate points, respectively. Then, the WEF was calculated and predicted based on the data of MWP, SWH, and water depth. The results indicate that, for all coordinates in the Bohai Sea, the H2O-AutoML algorithm is superior to the other five algorithms. Gradient boosting machine (GBM), extreme gradient boosting (XGBoost), and stacked ensemble models yielded the best performance out of the H2O algorithms. The significant wave height (SWH), the mean wave period (MWP), and the WEF in the Bohai Sea tended to be concentrated in the center of the sea and dispersed in the nearshore areas. In the year 2000, 2010, 2020, and 2030, the maximum annual average WEF at each research coordinate in the Bohai Sea is around 1.5 kW/m, with a higher flux in autumn and winter. In summary, the results provide ocean parameter characterization for the design and deployment of wave energy harvesting devices. Moreover, the automated machine learning introduced herein has potential for use in more applications in ocean engineering. [ABSTRACT FROM AUTHOR]

This paper established the system of assessment in dex for regionalization of geological hazards in Bohai Sea with four aspects of hydrodynamic condition, engineering geological environment, disaster geological conditions and human engineering activities based on analytic hierarchy process, eight evaluation factors selected and the distribution characteristics of each geological hazard evaluation factor which were discussed in detail. The integrated geological disaster evaluation and regionalization were carried out combined with qualitative analysis and quantitative calculation. The risk level of submarine geological hazards in Bohai Sea are divided into four types: high, medium-high, medium-low and low.The study results can provide scientific basis for engineering construction and hazard prevention in Bohai Sea area.

Green tides have increasingly become a nuisance worldwide in recent years, and especially in China. Since 2015, green tides have started recurring in Jinmeng Bay, Qinhuangdao, western Bohai Sea of China, and have severely deteriorated the tourism environment there. In order to investigate the migration process of the green tides in Jinmeng Bay, a hydrodynamic model and a particle-tracking model were applied based on the latest green tide event in August 2021. The hydrodynamic model was applied with triple-level 2DH meshes with different refinements and scales, which provided the hydrodynamics to drive the green macroalgae into the particle-tracking model. From the model results, the semi-enclosed waters surrounded by multiple artificial structures are a low-energy hydrodynamic environment, which is not helpful for water exchange and thus the dispersal of nutrients. The green macroalgae are distributed substantially within the semi-enclosed waters, and few are transported out with low biomass. The effects of wind and artificial structures both increase the coverage of the green macroalgae trajectories; the effect of wind plays a more important role. A sensitivity analysis of the effect of wind showed that 6 m/s wind in ENE led to the maximum coverage of the green macroalgae trajectories in the cases of different magnitudes and directions of winds. This study can provide references for the pre-warning and mitigation of green tides in Jinmeng Bay and other similar places. [ABSTRACT FROM AUTHOR]

Source rocks and geological conditions favorable for forming low-maturity oil and gas are noted in the Bohai Sea. However, systematic research has not been performed on these oil and gas formations and resource potentials. Thus, to understand the low-maturity oil and gas formation mechanisms in the Bohai Sea and to assess their resource potentials and exploration prospects, the characteristics and low-maturity hydrocarbon generation potential of source rocks in the southern sag of the Liaoxi Depression were examined via experimental analyses, such as chromatography-mass spectrometry of saturated and aromatic hydrocarbons. Meanwhile, typical reserves were systematically analyzed in vertical and horizontal directions and compared to reservoirs in adjacent sags on the same planes. The formation mechanisms of low-maturity oil and gas were investigated in-depth, and the contributions of these oil and gas in the southern sag of the Liaoxi Depression were determined. The following conclusions were drawn: (1) The Shahejie Formation in the southern sag of the Liaoxi Depression was formed in saline environments so that the resulting source rocks can generate large amounts of liquid hydrocarbons rich at low maturity. These source rocks are characterized by their potential to yield low-maturity oils at early stages. (2) The deep LD4 and LD5 oil reserves in the steep slopes of the southern sag of the Liaoxi Depression are of low maturity. The low-maturity oils were produced from the saline source rocks in the Shahejie Formation. With the help of faults connecting the source rocks and the traps, oil and gas generated at lowmaturity stages migrated into the traps along the steep slopes to form low-maturity oil and gas reserves. [ABSTRACT FROM AUTHOR]

A novel coronavirus (SARS-CoV-2) has caused more than 150 million confirmed infections worldwide, while it is not clear whether it affects the coastal waters. This paper proposed a biophysical model based on 16 scenarios with different virus half-life parameters to assess potential viral contamination from 25 municipal sewage outfalls into the Bohai Sea. Viral concentration maps showing spatial and temporal changes are provided based on a biophysical model under multiple scenarios. Results demonstrate that adjacent sea areas can become exposed to SARS-CoV-2 via water-borne transport from outfalls, with a higher risk in winter, because SARS-CoV-2 can be highly stable at low temperature. As coastal waters are the ultimate sink for wastewater and the epidemic will last for long time, this work is of great importance to raise awareness, identify vulnerable areas for marine mammals, and avoid the risk of exposure of tourists at bathing beach. • A model is presented to estimate the risk of SARS-CoV-2 in coastal waters. • Exposure level varies significantly in different seasons. • Marine mammals may be infected for highly stability of virus at low temperatures. [ABSTRACT FROM AUTHOR]

A novel coronavirus (SARS-CoV-2) has caused more than 150 million confirmed infections worldwide, while it is not clear whether it affects the coastal waters. This paper proposed a biophysical model based on 16 scenarios with different virus half-life parameters to assess potential viral contamination from 25 municipal sewage outfalls into the Bohai Sea. Viral concentration maps showing spatial and temporal changes are provided based on a biophysical model under multiple scenarios. Results demonstrate that adjacent sea areas can become exposed to SARS-CoV-2 via water-borne transport from outfalls, with a higher risk in winter, because SARS-CoV-2 can be highly stable at low temperature. As coastal waters are the ultimate sink for wastewater and the epidemic will last for long time, this work is of great importance to raise awareness, identify vulnerable areas for marine mammals, and avoid the risk of exposure of tourists at bathing beach.

Artificial reefs are considered to have the function of repairing and improving the coastal habitat and increasing the fishery production, which are mainly achieved by changing the regional hydrodynamic conditions. The characteristics of flow turbulence structure are an important part of the regional hydrodynamic characteristics. Different methods are used to evaluate the performance of artificial reefs according to their shape and the purpose for which the reef was built. For this study, the M-shaped unit reefs, which are to be put into the area of Liaodong Bay, were selected as the research object and have never been fully investigated before. Experimental tests were conducted to assess the effect of these M-shaped artificial reefs on the vertical and longitudinal turbulent intensity under different hydraulic conditions and geometries, and datasets were collected by using the Particle Image Velocimetry technique implemented within the experimental facility. The distribution and variation characteristics of the turbulence intensity were analyzed, and the main results obtained can confirm that in the artificial reef area, there was an extremely clear turbulent boundary. Furthermore, the area of influence of the longitudinal turbulence was identified to be larger than that of the vertical turbulence, and the position where the maximum turbulence intensity appeared was close to where the maximum velocity was measured. Finally, results demonstrate that low turbulence conditions are typically located in front of the unit reef, the general turbulence area is located within the upwelling zone, and the more intense turbulence area is located between the two M-shaped monocases. These results are extremely important, because they provide the local authorities with specific knowledge about what could be the effect of these M-shaped reefs within the area where they will be implemented, and therefore, specific actions can be taken in consideration with the geometrical setup suggested as an optimal solution within this study. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of a radionuclide dispersion model for the nuclear power plants in the Bohai, Yellow, and East China seas (BYECS) characterized by high turbidity and multi-scale circulations, focusing on the comparison of dispersion processes of 137Cs depending upon, in particular, the suspended sediment concentration and erosion/sedimentation processes. The simulations were carried out using a multi-fraction sediment transport model embedded in the semi-implicit Eulerian–Lagrangian finite-element coupled wave-circulation model linked with the model of radionuclide transport, which describes the key radionuclide transfer processes in the system of water–multi-fraction sediments. In contrast to the Eulerian models used for hydrodynamics and sediment transport processes, the Lagrangian technique was applied to simulate the transport of radionuclides. The simulation results for total suspended concentration agreed with in situ measurements and the Geostationary Ocean Color Imager data. The results of the simulation of hypothetical releases of 137Cs from four nuclear power plants (NPPs) placed in BYECS essentially differ from the real release of activity in the Pacific Ocean shelf due to the Fukushima Daiichi accident, which took place at the same time and released activity that was similar. The total amount of bottom contamination of 137Cs in releases from the Sanmen, Hanbit, and Hongyanhe NPPs was about 40% of dissolved component, and the total amount of suspended component was about 20% of dissolved component, in contrast with the Fukushima Daiichi accident, where the particulate component was only 2%. The results demonstrate the importance of erosion processes in the budget of 137Cs in shallow areas around the Sanmen and Hanbit NPPs, where strong wind and tidal currents took place.

In the application of ocean color remote sensing, remote sensing reflectance spectral (Rrs(λ)) is the most important and basic parameter for the development of bio-optical algorithms. Atmospheric correction of ocean color data is a key factor in obtaining accurate water Rrs(λ) data. Based on the QA (quality assurance) score spectral quality evaluation system, the quality of Rrs(λ) spectral of GOCI (Geostationary Ocean Color Imager) obtained from four atmospheric-correction algorithms in the Bohai Sea were evaluated and analyzed in this paper. The four atmospheric-correction algorithms are the NASA (National Aeronautics and Space Administration) standard near-infrared atmospheric-correction algorithm (denoted as Seadas—Default), MUMM (Management Unit of the North Sea Mathematical Models, denoted as Seadas—MUMM), and the standard atmospheric-correction algorithms of KOSC GOCI GDPS2.0 (denoted as GDPS2.0) and GDPS1.3 (denoted as GDPS1.3). It is shown that over 90% of the Rrs(λ) data are in good quality with a score ≥4/6 for the GDPS1.3 algorithm. The probability of Rrs(λ) with a QA score of 1 is significantly higher for the GDPS1.3 algorithm (57.36%), compared with Seadas—Default (37.91%), Seadas—MUMM (35.96%), and GDPS2.0 (33.05%). The field and MODIS measurements of Rrs(λ) were compared with simultaneous GOCI Rrs(λ), and they demonstrate that the QA score system is useful in evaluating the spectral shape of Rrs(λ). The comparison results indicate that higher QA scores have higher accuracy of the Rrs band ratio. The QA score system is helpful to develop and evaluate bio-optical algorithms based on the band ratio. The hourly variation of QA score from UTC 00:16 to 07:16 was investigated as well, and it demonstrates that the data quality of GOCI Rrs(λ) can vary in an hour scale. The GOCI data with high quality should be selected with caution when studying the hourly variation of biogeochemical properties in the Bohai Sea from GOCI measurements.

Per- and polyfluoroalkyl substances (PFASs) contamination in the Bohai Sea and its surrounding rivers has attracted considerable attention in recent years. However, few studies have been conducted regarding the distribution of PFASs in multiple environmental media and their distributions between the suspended particles and dissolved phases. In this study, surface water, surface sediment, and air samples were collected at the Bohai Sea to investigate the concentration and distribution of 39 targeted PFASs. Moreover, river water samples from 35 river estuaries were collected to estimate PFAS discharge fluxes to the Bohai Sea. The results showed that total ionic compound (Σ i -PFASs) concentrations ranged from 19.3 to 967 ng/L (mean 125 ± 152 ng/L) in the water and 0.70–4.13 ng/g dw (1.78 ± 0.76 ng/g) in surface sediment of the Bohai Sea, respectively. In the estuaries, Σ i -PFAS concentrations were ranged from 10.5 to 13500 ng/L (882 ± 2410 ng/L). In the air, ΣPFAS (Σi-PFASs + Σn-PFASs) concentrations ranged from 199 to 678 pg/m3 (462 ± 166 pg/m3). Perfluorooctanoic acid (PFOA) was the predominant compound in the seawater, sediment, and river water; in the air, 8:2 fluorotelomer alcohol was predominant. Xiaoqing River discharged the largest Σi-PFAS flux to the Bohai Sea, which was estimated as 12,100 kg/y. Some alternatives, i.e., 6:2 fluorotelomer sulfonate acid (6:2 FTSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and chlorinated 6:2 polyfluorinated ether sulfonic acid (Cl-6:2 PFESA), showed higher levels than or comparable concentrations to those of the C8 legacy PFASs in some sampling sites. The particle-derived distribution coefficient in seawater was higher than that in the river water. Using high resolution mass spectrometry, 29 nontarget emerging PFASs were found in 3 river water and 3 seawater samples. Further studies should be conducted to clarify the sources and ecotoxicological effects of these emerging PFASs in the Bohai Sea area. Image 1 • Thirty-nine PFASs were quantified in water, sediment and air from the Bohai Sea and its rivers. • The K d between dissolved and particle phases in seawater were higher than those in river water. • Discharge of total i -PFASs from 34 rivers was estimated to be 20.6 t/y. • Twenty-nine novel PFASs were screening in sea and river water by HRMS. This paper revealed the levels and composition of legacy and emerging PFASs in multiple environmental media of the Bohai Sea. [ABSTRACT FROM AUTHOR]

This paper presents an incremental variational method to assimilate the observed tidal harmonic constants using a frequency domain linearized shallow water equation. A cost function was constructed with tidal boundary conditions and tidal forcing as its control (independent) variables. To minimize the cost function, optimal boundary conditions and tidal forcing were derived using a conventional dual 4-Dimensional Variational (4D-Var) Physical-space Statistical Analysis System. The tangent linear and adjoint model were solved by using a finite element method. By adapting the incremental form, the variational method streamlines the workflow to provide the incremental correction to the boundary conditions and tidal forcing of a hydrodynamic forward model. The method was tested for semi-diurnal M2 tides in a regional sea with a complex tidal system. The results demonstrate a 65−72% reduction of tidal harmonic constant vector error by assimilating the observed M2 tidal harmonic constants. In addition to improving the tides of a hydrodynamic model by optimizing boundary conditions and tidal forcing, the method computes a spatially varying uncertainty of individual tidal constituents in the model. The method provides a versatile tool for mapping the spatially continuous tides and currents in coastal and estuarine waters by assimilating the harmonic constants of individual tidal constituents of observed tides and currents.

The velocity structure of the crust beneath Liaoning province and the Bohai sea in China was imaged using ambient seismic noise recorded by 73 regional broadband stations. All available three-component time series from the 12-month span between January and December 2013 were cross-correlated to yield empirical Green's functions for Rayleigh and Love waves. Phasevelocity dispersion curves for the Rayleigh waves and the Love waves were measured by applying the frequencytime analysis method. Dispersion measurements of the Rayleigh wave and the Love wave were then utilized to construct 2D phase-velocity maps for the Rayleigh wave at 8-35 s periods and the Love wave at 9-32 s periods, respectively. Both Rayleigh and Love phase-velocity maps show significant lateral variations that are correlated well with known geological features and tectonics units in the study region. Next, phase dispersion curves of the Rayleigh wave and the Love wave extracted from each cell of the 2D Rayleigh wave and Love wave phase-velocity maps, respectively, were inverted simultaneously to determine the 3D shear wave velocity structures. The horizontal shear wave velocity images clearly and intuitively exhibit that the earthquake swarms in the Haicheng region and the Tangshan region are mainly clustered in the transition zone between the low- and high-velocity zones in the upper crust, coinciding with fault zones, and their distribution is very closely associated with these faults. The vertical shear wave velocity image reveals that the lower crust downward to the uppermost mantle is featured by distinctly high velocities, with even a high-velocity thinner layer existing at the bottom of the lower crust near Moho in central and northern the Bohai sea along the Tanlu fault, and these phenomena could be caused by the intrusion of mantle material, indicating the Tanlu fault could be just as the uprising channel of deep materials. [ABSTRACT FROM AUTHOR]

Particle size distribution (PSD) is an important parameter that is relevant to many aspects of marine ecosystems, such as phytoplankton functional types, optical absorption and scattering from particulates, sediment fluxes, and carbon export. However, only a handful of studies have documented the PSD variability in different regions. Here, we investigate the PSD properties and variability in two shallow and semi-enclosed seas (the Bohai Sea (BS) and Yellow Sea (YS)), using in situ laser diffraction measurements (LISST-100X Type C) and other measurements at 79 stations in November 2013. The results show large variability in particle concentrations (in both volume and number concentrations), with volume concentrations varying by 57-fold. The median particle diameter (Dv50) from each of the water samples also covers a large range (22.4-307.0 μm) and has an irregular statistical distribution, indicating complexity in the PSD. The PSD slopes (2.7-4.5), estimated from a power-law model, cover nearly the entire range reported previously for natural waters. Small mineral particles (with large PSD slopes) are characteristic of near-shore waters prone to sediment resuspension by winds and tides, while large biological particles (with small PSD slopes) dominate the total suspended particulates for waters away from the coast. For the BS and YS, this study provides the first report on the properties and spatial variability of the PSD, which may influence the optical properties of the ocean surface and remote sensing algorithms that are based on estimations of particle concentrations and sizes. [ABSTRACT FROM AUTHOR]

Using the synchronous data such as weather radar, oceanic WRF model etc., a severe convective weather process has been analyzed on August 31, 2015 in Bohai Sea area, China. The results show that the shear line moved eastward and enhanced at the 925hPa and 850hPa in Bohai Bay from 08:00 to 20:00, the index K was 35 °C, index SI was -1.81 °C, the CAPE was 166 J/kg and the vertical wind shear was 16m·s−1 in the stratification curve at 08:00 A.M, because of this background, the severe convective weather occurred in Tianjin. The shear line moved northward at the 925hPa of the lower lay from 20:00 P.M on August 31 to 08:00 A.M on September 1, the convective instability energy increased, several severe convective storm cell of meso-γscale and meso-βscale near the shear line have been induced in the central area of Bohai Sea, the new round of the was caused by a series of effecting of radar echo. Severe weather process CAPE was released by the strong vertical movement and water vapor convergence of the boundary layer, the cut-in of weaker dry and cold of Δθse (850-500 hPa) corresponded with the happening and impact area of the convection system in north of Liaodong bay. And this paper established the early warning model about the severe convective weather for the sightseeing boat in Bohai Sea.

Witkowski, A.; Li, C. L.; Zg[lstrok]obicka, I.; Yu, S. X.; Ashworth, M.; Dąbek, P.; Qin, S.; Tang, C.; Krzywda, M.; Ruppel, M.; Theriot, E. C.; Jansen, R. K.; Car, A.; Płociński, T.; Wang, Y. C.; Sabir, J. S. M.; Daniszewska-Kowalczyk, G.; Kierzek, A., and Hajrah, N. H., 2016. Multigene assessment of biodiversity of diatom (Bacillariophyceae) assemblages from the littoral zone of the Bohai and Yellow Seas in Yantai region of Northeast China with some remarks on ubiquitous taxa. Diatoms are important contributors to the benthic microeukaryote flora. This manuscript lays the foundation for future metagenomic and environmental sequencing projects off coastal China by curating diatom DNA sequences from the Yantai region of the Bohai and Yellow Seas (Northeast China). These studies are based on cultures established from samples collected in different seasons from marine littoral and supralittoral zones in 2013 and 2014. Thirty-six diatom strains were cultured successfully and identification of these clones was determined by light and scanning electron microscopy(LM and SEM) and DNA sequencing of the nuclear-encoded small subunit ribosomal RNA (SSU)and chloroplast-encoded rbcL and psbC genes. The strains primarily represent raphid pennate genera, such as Amphora, Amphora ( Oxyamphora), Caloneis, Diploneis, Halamphora, Navicula, Nitzschia, Parlibellus, Pleurosigma, Surirella and Tryblionella. When the DNA markers from these strains were analysed in a multi-gene phylogeny, we found that some clones-particularly within the genera Amphora, Navicula and Nitzschia-show greater than expected genetic diversity despite their very similar morphology and morphometrics. We also compared the molecular and morphological identities of several seemingly ubiquitous marine littoral taxa in the genera Amphora and Nitzschia from the Indian Ocean and Atlantic Ocean, the Red Sea and Adriatic Sea to their Yellow Sea counterparts. [ABSTRACT FROM AUTHOR]

Tang, C.; Li, Y. F.; Liu, X.; Zhao, Y., and Zhang, H., 2016. Risk of surface sediment erosion in the Bohai Sea, North Yellow Sea and its indication to tidal sand ridge occurrence. Bottom geomorphological evolution and sediment distribution are under strong control of tidal forcing along China's coast. To quantify and assess the temporal-spatial change of bottom environment, a risk-based probabilistic concept of erosion is applied and maps of erosion risk are constructed. Sediment data categorized into 5 classes, together with hydrodynamic data in a temporal resolution of one hour and a model time of one month, are used to calculate the potential of erosion of surface sediments in the Bohai Sea, North Yellow Sea. Comparison with results of the tidal ellipse and bottom shear stress from model output shows that the highest risk of erosion is located in the Yalujiang Estuary, West Korea Bay, north of the Bohai Bay and in the surroundings of the Laotieshan channel of Bohai Strait, which may explain the occurrence of tidal sand ridges in the modeling domain. [ABSTRACT FROM AUTHOR]

Wang, A. M.; Wang, H. J.; Bi, N. S., and Wu, X., 2016. Sediment transport and dispersal pattern from the Bohai Sea to the Yellow Sea. Suspended sediment flux, dispersal patterns and its possible mechanisms in the Bohai Sea were investigated based on the observational data in May and November, 2012, data retrieved from MODIS imageries and the ocean current data from HYCOM. The sediment dispersal pattern and the annual net sediment flux presented evident seasonal variability. During wintertime, the prevailing strong northerly winds and the related high wave heights resuspended the sediment along the coast of the Huanghe Delta that was transported into the Laizhou Bay along its western coast and exported to the Bohai Strait through the eastern Laizhou Bay as enhanced by the coastal current. The wintertime contributed approximately 4.84 Mt of suspended sediment flux to the Yellow Sea, as higher than the flux in summertime by one order. In summertime, the less energetic environment together with the stratified water column was unfavorable to the sediment export to the Yellow Sea. As a result, the sediment delivered by the Huanghe to the sea in summertime mostly accumulated within the subaqueous delta, which acted as a primary source of sediment export to the Yellow Sea in wintertime. [ABSTRACT FROM AUTHOR]

The research uses the ADI (Alternating Direction Implicit) method to disperse and solve the two-dimensional shallow water circulation equations, based on upwind scheme; the red tide biodynamic equations are dispersed, then a two-dimensional ecological mathematical model of red tide is built by combining hydrodynamics with biodynamics. The two-dimensional ecological mathematical model of red tide is applied in Bohai Sea to simulate the actual Phaeocystis red tide instance which occurred on 6th-16th June, 2004. The calculated area of red tide from the mathematical model is compared with that from remote sensing photos of EOS/MODIS secondary planet. The results show that the model simulate the process of the increase and decrease of red tide well, which provides a scientific basis for a red tide forecast of Bohai Sea. [ABSTRACT FROM AUTHOR]

The Laotieshan Channel is one of the major channels in the north of the Bohai Strait, China. A tidal depositional system shaped by strong currents has developed in the eastern Bohai Sea, consisting of the Laotieshan Channel, the Liaodong Shoal and the Bozhong Shoal. Based on the grain-size characteristics, distribution of heavy minerals and numerical simulation results, the sediment distributions of different geomorphic units were analysed, and the trend of sediment transport is discussed. The results show that coarse-grained sediment is mainly distributed in the Laotieshan Channel, and the typical sediment type is muddy sandy gravel, whereas fine-grained sediment mainly covers the Liaodong Shoal and the Bozhong Shoal. Moreover, the sediments in sand ridges have a finer grain size than those in troughs. The sediment of the Bozhong Shoal mainly consists of muddy sand. The sediments of ridges, in contrast, are sand and silty sand; those of troughs are sandy silt and silty sand. The distribution of typical heavy minerals is similar to that of total heavy minerals and areas with relatively high content occur in the sand ridge area and the sand sheet area. The Laotieshan Channel is eroded and the sediment is transported to the Liaodong Shoal and the Bozhong Shoal. The sediment continues to be transported northwest in the Bozhong Shoal, while in the Liaodong Shoal it is transported approximately along the long axes of sand ridges. The sediment transport trends in the tidal depositional system are adapted to the hydrodynamic environment, and the tidal geomorphological system of the Liaodong Shoal will remain stable at the century scale. [ABSTRACT FROM AUTHOR]

Ocean colour data are crucial for monitoring and assessing marine ecosystems. In this study, the Data Interpolating Empirical Orthogonal Functions (DINEOF) approach was applied to the Ocean Colour Climate Change Initiative (OC-CCI), chlorophyll-a (Chl-a) and Secchi disk depth (Zsd) to completely reconstruct the missing pixels in the Bohai Sea during 1997–2019. The results of cross-validation demonstrate that the DINEOF reconstructed data have a good agreement with the satellite-measured data. Based on monthly cloud-free satellite data reconstructions, the Zsd series showed high negative correlation with log10 (Chl-a). The Zsd as a function of log10 (Chl-a) can be well fitted by the cubic polynomial in the offshore waters. The Chl-a in the entire Bohai Sea showed a significant decreasing trend (−0.013 mg/m3/year), while the Zsd exhibited a significant increasing trend (0.0065 m/year), and both had regional-seasonal variations. In addition, the ensemble empirical mode decomposition (EEMD) results reveal highly nonlinear trends of Chl-a and Zsd. The linear and nonlinear trends of Chl-a and Zsd suggest the deterioration of water quality in the Bohai Sea was not continued over the past two decades. This study presents the first simultaneous investigation of Chl-a and Zsd using the 23 years of cloud-free reconstructions in the Bohai Sea. [ABSTRACT FROM AUTHOR]

Oil spills have immediate adverse effects on marine ecological functions. Accurate assessment of the damage caused by the oil spill is of great significance for the protection of marine ecosystems. In this study the observation data of Chaetoceros and shellfish before and after the Penglai 19-3 oil spill in the Bohai Sea were analyzed by the least-squares fitting method and radial basis function (RBF) interpolation. Besides, an oil transport model is provided which considers both the hydrodynamic mechanism and monitoring data to accurately simulate the spatial and temporal distribution of total petroleum hydrocarbons (TPH) in the Bohai Sea. It was found that the abundance of Chaetoceros and shellfish exposed to the oil spill decreased rapidly. The biomass loss of Chaetoceros and shellfish are 7.25 × 10 14 ~ 7.28 × 10 14   ind and 2.30 × 10 12 ~ 2.51 × 10 12   ind in the area with TPH over 50 mg/m3 during the observation period, respectively. This study highlights the evaluation of ecological resource loss caused by the oil spill, which is useful for the protection and restoration of the biological resources following the oil spill. [ABSTRACT FROM AUTHOR]