Search Results (211)

Extreme surface winds and wave heights of tropical cyclones (TCs)—pose serious threats to coastal community, infrastructure and environments. In recent decades, progress in numerical wave modeling has significantly enhanced the ability to reconstruct and predict wave behavior. This review offers an in-depth overview of TC-related wave modeling utilizing different computational schemes, with a special attention to WAVEWATCH III (WW3) and Simulating Waves Nearshore (SWAN). Due to the complex air–sea interactions during TCs, it is challenging to obtain accurate wind input data and optimize the parameterizations. Substantial spatial and temporal variations in water levels and current patterns occurs when coastal circulation is modulated by varying underwater topography. To explore their influence on waves, this study employs a coupled SWAN and Finite-Volume Community Ocean Model (FVCOM) modeling approach. Additionally, the interplay between wave and sea surface temperature (SST) is investigated by incorporating four key wave-induced forcing through breaking and non-breaking waves, radiation stress, and Stokes drift from WW3 into the Stony Brook Parallel Ocean Model (sbPOM). 20 TC events were analyzed to evaluate the performance of the selected parameterizations of external forcings in WW3 and SWAN. Among different nonlinear wave interaction schemes, Generalized Multiple Discrete Interaction Approximation (GMD) Discrete Interaction Approximation (DIA) and the computationally expensive Wave-Ray Tracing (WRT) A refined drag coefficient (C_d) equation, applied within an upgraded ST6 configuration, reduce significant wave height (SWH) prediction errors and the root mean square error (RMSE) for both SWAN and WW3 wave models. Surface currents and sea level variations notably altered the wave energy and wave height distributions, especially in the area with strong TC-induced oceanic current. Finally, coupling four wave-induced forcings into sbPOM enhanced SST simulation by refining heat flux estimates and promoting vertical mixing. Validation against Argo data showed that the updated sbPOM model achieved an RMSE as low as 1.39 m, with correlation coefficients nearing 0.9881. Full article

Plastic debris is a pervasive and persistent threat to marine ecosystems. Microplastics (plastics < 5 mm) are increasing in a variety of marine habitats, including open water systems, shorelines, and benthic sediments. It remains unclear how microplastics distribute and accumulate in marine systems and the extent to which this pollutant is accessible to marine taxa. We examined subtidal benthic sediments and beach sediments in critical nearshore habitats for forage fish species—Pacific sand lance (Ammodytes personatus), Pacific herring (Clupea pallasi), and surf smelt (Hypomesus pretiosus)—to quantify microplastic concentrations in the spawning and deep-water habitats of these fish and better understand how microplastics accumulate and distribute in nearshore systems. In the San Juan Islands, we examined an offshore subtidal bedform in a high-flow channel and beach sites of protected and exposed shorelines. We also examined 12 beach sites proximate to urban areas in Puget Sound. Microplastics were found in all samples and at all sample sites. Microfibers were the most abundant, and flakes were present proximate to major shipyards and marinas. Microplastics were significantly elevated in Puget Sound compared to the San Juan Archipelago. Protected beaches had elevated concentrations relative to exposed beaches and subtidal sediments. Microplastics were in higher concentrations in sand and fine-grain sediments, poorly sorted sediments, and artificial sediments. Microplastics were also elevated at sites confirmed as spawning habitats for forage fish. The model results indicate that both current speed and proximate urban populations influence nearshore microplastic concentrations. Our research provides new insights into how microplastics are distributed, deposited, and retained in marine sediments and shorelines, as well as insight into potential exposure in benthic, demersal, and shoreline habitats. Further analyses are required to examine the relative influence of urban populations and shipping lanes and the effects of physical processes such as wave exposure, tidal currents, and shoreline geometry. Full article

Suspended particulate matter (SPM) plays a pivotal role in marine source-to-sink sedimentary systems. Internal solitary waves (ISWs), a prevalent hydrodynamic phenomenon, significantly influence vertical mixing, cross-shelf material transport, and sediment resuspension. Acting as energetic nonlinear waves, ISWs can disrupt the settling trajectories of suspended particles, enhance lateral transport above the pycnocline, and generate nepheloid layers nearshore. Meanwhile, intense turbulent mixing induced by ISWs accumulates large quantities of SPM at both the leading surface and trailing bottom of the waves, thereby altering the structure and dynamics of the intermediate nepheloid layers. This review synthesizes recent advances in the in situ observational techniques for SPM under the influence of ISWs and highlights the key mechanisms governing their interactions. Particular attention is given to representative field cases in the SCS, where topographic complexity and strong stratification amplify ISWs–sediment coupling. Finally, current limitations in observational and modeling approaches are discussed, with suggestions for future interdisciplinary research directions that better integrate hydrodynamic and sediment transport processes. Full article

Coastal climate processes that affect landscape hydrology and beach dynamics are studied using local and remote data sets near Cape Vidal (28.12° S, 32.55° E). The sporadic intra-seasonal pulsing of coastal runoff, vegetation, and winds is analyzed to understand sediment inputs and transport by near-shore wind-waves and currents. River-borne sediments, eroded coral substrates, and reworked beach sand are mobilized by frequent storms. Surf-zone currents ~0.4 m/s instill the northward transport of ~6 10⁵ kg/yr/m. An analysis of the mean annual cycle over the period of 1997–2024 indicates a crest of rainfall over the Umfolozi catchment during summer (Oct–Mar), whereas coastal suspended sediment, based on satellite red-band reflectivity, rises in winter (Apr–Sep) due to a deeper mixed layer and larger northward wave heights. Sediment input to the beaches near Cape Vidal exhibit a 3–6-year cycle of southeasterly waves and rainy weather associated with cool La Nina tropical sea temperatures. Beachfront sand dunes are wind-swept and release sediment at ~10³ m³/yr/m, which builds tall back-dunes and helps replenish the shoreline, especially during anticyclonic dry spells. A wind event in Nov 2018 is analyzed to quantify aeolian transport, and a flood in Jan–Feb 2025 is studied for river plumes that meet with stormy seas. Management efforts to limit development and recreational access have contributed to a sustainable coastal environment despite rising tides and inland temperatures. Full article

Typhoons can significantly alter ocean hydrodynamic processes through their powerful external forces, greatly affecting marine biogeochemistry and ocean productivity. However, the specific impacts of typhoons with different tracks on coastal dynamics, including frontal activities and phytoplankton lateral transport, are not well understood. This study captured two distinct types of typhoons, namely Merbok (2017) and Nuri (2020), which landed from the right and left sides of the Pearl River Estuary (PRE), respectively, utilizing satellite remote sensing data to study their impacts on frontal dynamics and marine productivity. We found that after both typhoons, the southwest monsoon amplified geostrophic currents significantly (increased ~14% after Nuri (2020) and 48% after Merbok (2020)). These stronger currents transported warmer offshore seawater from the South China Sea to the PRE and intensified the frontal activities in nearshore PRE (increased ~47% after Nuri (2020) and ~2.5 times after Merbok (2020)). The ocean fronts limited the transport of high-chlorophyll and eutrophic water from the PRE to the offshore waters due to the barrier effect of the front. This resulted in a sharp drop in chlorophyll concentrations in the offshore-adjacent waters of PER after Typhoon Nuri (2020) (~37%). By contrast, despite the intensified geostrophic current induced by the summer monsoon following Typhoon Merbok (2020), its stronger offshore force, driven by the intense offshore wind stress (characteristic of the left-side typhoon), caused the nearshore front to move offshore. The displacement of fronts lifted the restriction of the front barrier and led more high-chlorophyll (increased ~4 times) and eutrophic water to be transported offshore, thereby stimulating offshore algal blooms. Our findings elucidate the mechanisms by which different track typhoons influence chlorophyll distribution through changes in frontal dynamics, offering new perspectives on the coastal ecological impacts of typhoons and further studies for typhoon impact modeling or longshore management. Full article

High-precision wave data serve as a foundation for investigating the wave characteristics of the East China Sea (ECS) and wave energy development. Based on the simulating waves nearshore (SWAN) model, this study uses the ERA5 (ECMWF Reanalysis v5) reanalysis wind field data and ETOPO1 bathymetric data to perform high-precision simulations at a resolution of 0.05° × 0.05° for the waves in the area of 25–35° N and 120–130° E in the ECS from 2009 to 2023. The simulation results indicate that the application of the whitecapping dissipation parameter Komen and the bottom friction parameter Collins yields an average RMSE of 0.374 m and 0.369 m when compared to satellite-measured data, demonstrating its superior suitability for wave simulation in shallow waters such as the ESC over the other whitecapping dissipation parameter, Westhuysen, and the other two bottom friction parameters, Jonswap and Madsen, in the SWAN model. The monthly average significant wave height (SWH) ranges from 0 to 3 m, exhibiting a trend that it is more important in autumn and winter than in spring and summer and gradually increases from the northwest to the southeast. Due to the influence of the Kuroshio current, topography, and events such as typhoons, areas with significant wave heights are found in the northwest of the Ryukyu Islands and north of the Taiwan Strait. The wave energy flux density in most areas of the ECS is >2 kW/m, particularly in the north of the Ryukyu Islands, where the annual average value remains above 8 kW/m. Because of the influence of climate events such as El Niño and extreme heatwaves, the wave energy flux density decreased significantly in some years (a 21% decrease in 2015). The coefficient of variation of wave energy in the East China Sea exhibits pronounced regional heterogeneity, which can be categorized into four distinct patterns: high mean wave energy with high variation coefficient, high mean wave energy with low variation coefficient, low mean wave energy with high variation coefficient, and low mean wave energy with low variation coefficient. This classification fundamentally reflects the intrinsic differences in dynamic environments across various maritime regions. These high-precision numerical simulation results provide methodological and theoretical support for exploring the spatiotemporal variation laws of waves in the ECS region, the development and utilization of wave resources, and marine engineering construction. Full article

Coral-reef fishes in the South China Sea play a crucial role in sustaining ecosystem stability and delivering essential ecological functions. However, widespread coral degradation has led to habitat loss, intensifying environmental stress on reef-associated fish communities. To better understand their current status and guide conservation efforts, this study conducted a comprehensive, trait-based assessment of coral-reef fish diversity across 19 reef sites in the South China Sea, spanning nearshore (Sanya, Hainan) and offshore (Xisha and Nansha Islands) systems. Significant spatial differences were observed in species composition, functional trait structure, and responses to environmental disturbance. Offshore reefs, particularly in the Nansha Islands, exhibited the highest species richness, trophic complexity, and functional diversity, while nearshore reefs showed simplified community structure dominated by small, sedentary species with high microhabitat dependence. Coral cover was only weakly correlated with fish diversity and failed to reflect functional trait complexity, highlighting the limitation of relying on structural indicators alone. Using community-weighted trait metrics, PCA, and indicator species analysis, this study established a tri-principle framework for identifying priority conservation species based on ecological function, rarity, and vulnerability. Key functional species—including Chlorurus sordidus, Siganus fuscescens, and Cephalopholis urodeta—were identified, along with representative conservation sites such as Meiji Reef, Lingyang Reef, and Luhuitou. These findings underscore the need to integrate species-level and functional diversity into coral reef monitoring and management. The proposed framework provides a science-based foundation for prioritizing species and habitats, enhancing the resilience of reef ecosystems under the dual threats of climate change and anthropogenic pressure. Full article

The primary contribution of this study lies in analyzing the dynamic drivers during two anomalous sea level rise events in the Bohai Sea through coupled numeric modeling using the Weather Research and Forecasting (WRF) model and the Finite-Volume Community Ocean Model (FVCOM) integrated with the Simulating Waves Nearshore (SWAN) module (hereafter referred to as FVCOM-SWAVE). WRF-derived wind speeds (0.05° grid resolution) were validated against Haiyang-2 (HY-2) scatterometer observations, yielding a root mean square error (RMSE) of 1.88 m/s and a correlation coefficient (Cor) of 0.85. Similarly, comparisons of significant wave height (SWH) simulated by FVCOM-SWAVE (0.05° triangular mesh) with HY-2 altimeter data showed an RMSE of 0.67 m and a Cor of 0.84. Four FVCOM sensitivity experiments were conducted to assess drivers of sea level rise, validated against tide gauge observations. The results identified tides as the primary driver of sea level rise, with wind stress and elevation forcing (e.g., storm surge) amplifying variability, while currents exhibited negligible influence. During the two events, i.e., 20–21 October and 25–26 August 2024, elevation forcing contributed to localized sea level rises of 0.6 m in the northern and southern Bohai Sea and 1.1 m in the southern Bohai Sea. A 1 m surge in the northern region correlated with intense Yellow Sea winds (20 m/s) and waves (5 m SWH), which drove water masses into the Bohai Sea. Stokes transport (wave-driven circulation) significantly amplified water levels during the 21 October and 26 August peak, underscoring critical wave–tide interactions. This study highlights the necessity of incorporating tides, wind, elevation forcing, and wave effects into coastal hydrodynamic models to improve predictions of extreme sea level rise events. In contrast, the role of imposed boundary current can be marginalized in such scenarios. Full article

The ecological restoration of oyster reef ecosystems enhances their ecological functions and strengthens carbon sequestration capacity in coastal zones. Identifying suitable restoration sites is a crucial prerequisite for initiating oyster reef restoration projects. This study developed an oyster reef restoration suitability index model for the Tianjin coast of Bohai Bay by integrating the Analytic Hierarchy Process (AHP) with the Geographic Information System (GIS). It was then applied to assess the region’s suitability for oyster reef restoration. The suitability analysis identified favorable environmental conditions for oyster reef restoration in most of the Tianjin coastal area, with high suitability for factors like dissolved oxygen, pH, and seabed slope. However, excessive water depth in the eastern bay mouth and strong currents in the southwestern region made these areas unsuitable. The northern and western coastal regions were deemed optimal restoration sites, while proximity to shipping lanes and industrial activities limited feasibility in some nearshore zones. The model outputs exhibited strong spatial concordance with existing oyster reef distributions, validating its predictive accuracy. This framework offers a robust foundation for oyster reef restoration planning, with an adaptable index system that allows for regional extrapolation. By leveraging this model, decision-makers can systematically evaluate site-specific restoration suitability, optimize resource allocation, and guide strategic conservation planning. Full article

Offshore wind power is one of the primary forms of utilizing marine green energy in China. Currently, near-shore wind power predominantly employs monopile foundations, with designs typically being overly conservative, resulting in high construction costs. Precise characterization of the interaction mechanisms between marine piles and surrounding soils is crucial for foundation design optimization. Traditional p-y curve methods, with simplified fitting functions, inadequately capture the complex pile–soil behaviors, limiting predictive accuracy and model uncertainty quantification. To address these challenges, this research collected 1852 empirical datasets of offshore wind monopile foundation pile–soil interactions, developing p-y curve and horizontal displacement prediction models using artificial neural network (ANN) expressions and comprehensive uncertainty statistical analysis. The constructed ANN model demonstrates a simple structure with satisfactory predictive performance, achieving average error margins below 6% and low to moderate prediction accuracy dispersion (26%~45%). In contrast, traditional p-y curve models show 30%~50% average biases with substantial accuracy dispersion near 80%, while conventional finite element methods exhibit approximately 40% error and dispersion. By strictly characterizing the probability cumulative function of the neural network model factors, a foundation is provided for reliability-based design. Through comprehensive case verification, it is demonstrated that the ANN-based model has significant advantages in terms of computational accuracy and efficiency in the design of offshore wind power foundations. Full article

Typhoons generate extreme waves that pose significant threats to offshore wind power platforms in deep-sea areas, a challenge not fully addressed in current design standards. This study investigates wind–wave coupling processes during typhoon events to provide guidance for typhoon selection in deep-sea wind power platform design. Using Pearson Type III frequency analysis of typhoon data from 1949 to 2019, the 50-year return period typhoon intensity was determined for the study area. The validated SWAN model was employed to simulate typhoon-induced waves, revealing that wave height contours align parallel to the coastline and increase sharply from nearshore to deep-sea areas. The maximum significant wave height reaches 7.78 m when a 50-year return period typhoon passes the engineering site. These findings offer critical insights for offshore wind farm design in typhoon-prone regions, providing a robust basis for wave load assessment, structural fatigue analysis, and safety optimization. Full article

A flapping hydrofoil device is an innovative device for enhancing the hydrodynamics of small rivers. While increasing the flow velocity of the river, it inevitably causes different degrees of scouring on the bank slope. This study aims to find an optimal combination of flapping hydrofoil parameters to maximize the pushing-water performance while minimizing the impact on bank slope scour, which is of great significance for the device’s application and environmental protection. Based on the finite volume method and overlapping dynamic grid technology, this paper selects the maximum bank slope scouring section as the research plane for numerical simulation. In order to expand the scope of application, the relative chord length c* (the ratio of chord length to river channel width) is introduced as a research parameter, and the influence of different relative chord lengths c* and frequencies f on the pushing-water performance of the device and the degree of bank slope scouring is systematically analyzed. The research results show that the near-shore current mean scouring force increases significantly with the increase in f and c*. The pushing-water efficiency will increase with c*, and will gradually increase with the increase in f and then tend to be stable. When c* = 1/2 and f = 2.5 Hz, the pushing-water efficiency reaches 51.04%, but at this time, the impact on bank slope scour is the most serious. When c* is reduced to 1/8, the bank slopes are not scoured even at the maximum frequency f = 2.5 Hz, and the pushing-water efficiency is 24.59% at this time. As c* decreases, the threshold frequency at which scour does not occur on the riverbank increases gradually. In addition, when c* is constant, decreasing f will significantly reduce the scouring force, but will have little effect on pushing-water efficiency. In order to achieve the purpose of this study, the parameters of flapping hydrofoil are recommended to be larger relative chord length and smaller motion frequency combinations. Full article

Storm surge is one of the most significant marine hazards in coastal regions of Fujian, China. Previous studies show that surface waves can exacerbate storm surge by providing additional momentum and mass flux. In fact, surface wave effects on currents can be divided into conservative and non-conservative parts. However, it is unclear whether or not both kinds of wave effects are important to storm surge. In this study, we utilize an ocean circulation model coupled with surface wave forcing to investigate wave effects on the storm surge caused by Typhoon Doksuri (2305). The results indicate that both Stokes drift and wave breaking significantly contribute to the storm surge in the region located in the northeast quadrant of the typhoon’s trajectory. Wave breaking enhances the onshore current during the passage of the typhoon. This effect, combined with the onshore Stokes drift, leads to a rapid accumulation of nearshore water, thereby exacerbating storm surge. This study compares the contribution of conservative and non-conservative wave effects to the storm surge induced by Doksuri and underscores the necessity for numerical models to incorporate wave breaking and Stokes drift in order to accurately simulate and forecast storm surge. Full article

Humpback whales (Megaptera novaeangliae) migrate annually along the east coast of Australia, utilizing various habitats, including open embayments such as the Gold Coast bay (GCB) in southeast Queensland, for resting and social behaviors. While their migration is well-documented, the influence of oceanographic factors such as the East Australian Current (EAC)—a warm ocean current near the GCB—on humpback whale counts nearshore is not well understood. This study aims to assess the regional distribution of humpback whales in the GCB over consecutive years and investigate how dynamic environmental factors, such as the proximity of the EAC’s inner edge to shore and sea surface temperature (SST), affect the distribution and migration patterns of humpback whales. We employed citizen science data to obtain humpback whale sightings and applied generalized additive models (GAM) to evaluate the effects of environmental variables on humpback whale counts. Results suggested that shifts in EAC proximity and SST significantly influence humpback whale presence in the GCB, indicating that oceanographic features may guide migratory pathways and aggregation patterns. These findings improve our understanding of how climatic factors affect coastal humpback whale distributions, providing insights relevant to management and abundance estimates. Full article

In the presented work, design conditions for breakwaters were derived from offshore climate reanalysis data (ERA5), which were downscaled to the nearshore by two numerical approaches, i.e., SwanOne and Delft3D, for different average and extreme wave and weather conditions. Model validation was performed using in situ measurements. The advantages and disadvantages of both numerical approaches were investigated. Both models showed sufficient accuracy according to measurements in the field, where SwanOne offers a simple and fast calculation method, while Delft3D provides a more complete representation, not only of waves but also current dynamics. However, it requires a much broader amount of input parameters and more complex boundary conditions. Then, SwanOne was applicable to calculate nearshore wave characteristics based on the input parameters extracted from the statistical analysis of long-term ERA5 data. Based on this process, design wave heights and periods at the nearshore were determined for 10- to 100-year return periods. For breakwater design on the west coast of the Mekong Delta, maximum wave heights in a range of 1.1 m to 1.3 m at a distance of 100 m to 300 m could be determined for a return period of 20 years, corresponding to water depths of 2.33 m and 2.88 m, respectively. Full article