Search Results (175)

The eastern North Pacific Ocean coastline (from the Salish Sea to the western Aleutian Islands) is highly glaciated with relic sediment deposits scattered throughout a highly contoured and variable bathymetry. Oceanographic conditions feature strong currents and tidal exchange. Sand wave fields are prominent features within these glaciated shorelines and provide critical habitat to sand lance (Ammodytes spp.). Despite an awareness of the importance of these benthic habitats, attributes related to their structure and characteristics remain undocumented. We explored the micro-bathymetric morphology of a subtidal sand wave field known to be a consistent habitat for sand lance. We calculated geomorphic attributes of the bedform habitat, analyzed sediment composition, and measured oceanographic properties of the associated water column. This feature has a streamlined teardrop form, tapered in the direction of the predominant tidal current. Consistent flow paths along the long axis contribute to well-defined and maintained bedform morphology and margin. Distinct patterns in amplitude and period of sand waves were documented. Strong tidal exchange has resulted in well-sorted medium-to-coarse-grained sediments with coarser sediments, including gravel and cobble, within wave troughs. Extensive mixing related to tidal currents results in a highly oxygenated water column, even to depths of 80 m. Our analysis provides unique insights into the physical characteristics that define high-quality habitat for these fish. Further work is needed to identify, enumerate, and map the presence and relative quality of these benthic habitats and to characterize the oceanographic properties that maintain these benthic habitats over time. Full article

High-resolution mooring observations captured diverse upper-ocean responses during typhoon passage, showing strong agreement with satellite-derived sea surface temperature and salinity. Analysis indicates that significant wind-induced mixing drove pronounced near-surface cooling and salinity increases at the mooring site. This mixing enhancement was predominantly governed by rapid intensification of near-inertial shear in the surface layer, revealed by mooring observations. Unlike shear instability, near-inertial horizontal kinetic energy displays a unique vertical distribution, decreasing with depth before rising again. Interestingly, the subsurface peak in diurnal tidal energy coincides vertically with the minimum in near-inertial energy. While both barotropic tidal forcing and stratification changes negligibly influence diurnal tidal energy emergence, significant energy transfer occurs from near-inertial internal waves to the diurnal tide. This finding highlights a critical tide–wave interaction process and demonstrates energy cascading within the oceanic internal wave spectrum. Full article

Recent studies have shown benefits of using tidal stream and wave energy in the electricity generation mix to improve supply–demand balancing on annual/subannual timeframes. This paper investigates this further by considering the variability of solar photovoltaic, onshore and offshore wind, wave, and tidal stream over multiple years. It also considers their ability to match with electricity demand when combined. Variability of demand and generation can have a significant impact on results. Over the sample of five years considered (2015–2019), demand varied by around 3%, and the availability of each renewable technology differed by up to 9%. This highlights the importance of considering multiple years of input data when assessing power system impacts, instead of relying on an ‘average’ year. It is also key that weather related correlations between renewable resources and with demand can be maintained in the data. Results from an economic dispatch model of Great Britain’s power system in 2030 are even more sensitive to the input data year, with costs and carbon emissions varying by up to 21% and 45%, respectively. Using wave or tidal stream as part of the future energy mix was seen to have a positive impact in all cases considered; 1 GW of wave and tidal (0.57% of total capacity) reduces annual dispatch cost by 0.2–1.3% and annual carbon emissions by 2.3–3.5%. These results lead to recommended best practises for modelling high renewable power systems, and will be of interest to modellers and policy makers. Full article

The early Paleozoic Huaiyuan Movement created a major unconformity in the Ordos Basin, significantly influencing sedimentation and early diagenesis in both the overlying and underlying strata near the unconformity. However, the origins of the associated dolomite and silica near this unconformity remain poorly understood. This study aims to reveal how this tectonic event controlled the Early–Middle Ordovician sedimentary environments and early diagenetic processes. The petrological and geochemical results indicate a progressive transition from a dolomitic tidal flat to an intra-platform depression, culminating in a mixed tidal flat during the Early-to-Middle Ordovician, driven by the Huaiyuan Movement. Furthermore, this movement, accompanied by intense weathering and erosion, increased the supply of marine dissolved silica (DSi) and terrestrial nutrients. Consequently, extensive tidal-edge biogenic silica accumulated, which later precipitated as siliceous-cemented dolomite during a shallow-burial stage. We propose a conceptual model of the sedimentary–early diagenetic processes in response to the Huaiyuan Movement, providing novel insights into the regional paleoenvironmental evolution across the Early–Middle Ordovician transition in the Ordos Basin. Full article

This study aimed to accurately simulate the main tidal characteristics in a regional domain featuring four open boundaries, with a primary focus on baroclinic tides. Such understanding is crucial for improving the representation of oceanic energy transfer and mixing processes in numerical models. To this end, the astronomical potential, load tide effects, and a wavelet-based analysis method were implemented in the three-dimensional ROMS model. The inclusion of the astronomical tidal and load tide aimed to enhance the accuracy of tidal simulations, while the wavelet method was employed to analyze the generation and propagation of internal tides from their source regions and to characterize their main features. Twin simulations with and without astronomical potential forcing were conducted to evaluate its influence on tidal elevations and currents. Model performance was assessed through comparison with tide gauge observations. Incorporating the potential forcing improves simulation accuracy, as the model fields successfully reproduced the main features of the barotropic tide and showed good agreement with observed amplitude and phase data. A complex principal component analysis was then applied to a matrix of normalized wavelet coefficients derived from the enhanced model outputs, enabling the characterization of horizontal modal propagation and vertical mode decomposition of both $M_2$ and nonlinear $M_4$ internal tides. Full article

This paper presents a robust optimization-based approach for voyage and power generation scheduling to enhance the economic efficiency and reliability of electric propulsion ships powered by polymer electrolyte membrane fuel cells (PEMFCs) and battery energy storage systems (BESSs). The scheduling method is formulated considering generation cost curves of PEMFCs with mixed-integer linear programming (MILP) and is extended to a robust optimization framework that accounts for marine environmental uncertainties. The robust optimization approach, implemented via the column-and-constraint generation (C&CG) method, ensures stable operation under various uncertainty scenarios, such as wave speed and direction influenced by wind and tidal currents. To validate the proposed method, a simulation was conducted under realistic operational conditions, followed by a case study comparing the MILP and robust optimization approaches in terms of economic efficiency and reliability. Additionally, the optimization model incorporated degradation costs associated with PEMFCs and BESSs to account for long-term operational efficiency. The case study assessed the performance of both methods under load variation scenarios across different marine environmental uncertainties. Full article

The transition zone between a shallow-water delta and tidal flat is characterized by a high degree of mixed siliciclastic–carbonate sedimentation. There are frequent lateral and vertical variations in sandstone, dolostone, limestone, and mixed siliciclastic–carbonate rock (MSR); however, their influence on reservoir quality remains uncertain. Member B of the Asmari Formation (Asmari B) in Iraq’s C Oilfield was deposited in a remnant ocean basin formed by the closure of the Neo-Tethys Ocean. During the Oligocene–Miocene, frequent exposure of the Arabian Shield provided intermittent sediment sources to the study area. Under shallow water and relatively arid conditions, widespread mixed sedimentation of siliciclastic sand and dolomitic components occurred. Taking Asmari B as a case study, this research employs core and thin-section observations, trace element analyses, and quantitative mineralogical interpretations of logging data to investigate the characteristics of mixed sedimentation and to evaluate its impact on reservoir quality. Four key aspects were identified: (1) Four main types of mixed lithofacies developed in Member B of the Asmari Formation, namely sandstone-bearing dolomite, dolomitic sandstone, dolostone-bearing sand, and sandy dolostone. These lithofacies were deposited in the transition zone between distributary channels and intertidal zone with different water depths. As the terrigenous input decreased, the water depth for sand-bearing facies increased. In particular, sandy dolostone was predominantly formed in subtidal settings under the influence of storm events. (2) MSRs are categorized based on the proportion of the minor component into high and low mixing degrees. Based on mineral compositions interpreted from well logging data, the mixing degree of MSRs was characterized by the thickness ratio, using the thickness of high- and low-mixing-degree MSRs relative to the total thickness of the formation. The MSRs mainly developed in the B1, B2, B3-1, B3-2, and B4 sublayers, where moderate provenance supply facilitated the high mixing of terrigenous clastic and carbonate components. (3) The pore and throat patterns of MSR reservoirs change with the mixing degree index. When the dolomite content in sandstone exceeds 25%, the pore–throat structure changes significantly. A small amount of sand in dolostone has little effect on the pore and throat. Sandy dolostone exhibits the poorest reservoir quality. (4) Mixed sandstone reservoirs are distributed on both sides of the distributary channels and mouth bar. The dolostone-bearing sand reservoirs are distributed in the transition zone between the sandy flat and dolomite flat. Sandy dolostone is mainly thin and isolated due to the influence of storm events. This study provides guidance for understanding the development patterns of MSR reservoirs under similar geological settings, facilitating the next step of oil and gas exploration in these special reservoirs. Full article

This study combines field and laboratory analyses from seven shallow wells (ZK1 to ZK7) positioned perpendicular to the coastline to investigate groundwater discharge and dynamics in the coastal unconfined aquifer of the intertidal zone at Yazhou Bay, Sanya, Hainan Province. The research highlights spatial variations in N₂O concentration, temperature, electrical conductivity (EC), pH, and the distribution of CFCs and CCl₄ in shallow groundwater, utilizing samples from wells ZK1 to ZK7 and seawater collected near ZK1. Key findings indicate that groundwater temperature decreases toward the ocean, while EC exhibits a stepwise increase from land to sea, with a sharp transition near ZK3 marking the freshwater–saltwater mixing zone. pH values are lowest in ZK3 and ZK4, gradually rising both inland and seaward. N₂O concentrations in the shallow wells (ZK1–ZK7) are divided into two distinct groups: higher concentrations (9.69–57.77 nmol/kg) in ZK5–ZK7 and lower concentrations (6.63–23.03 nmol/kg) in ZK1–ZK4. Wells ZK3 and ZK4 show minimal variation in CFC-11 and CFC-113 concentrations, suggesting they represent a transition zone that likely delineates groundwater flow paths. In contrast, significant concentration differences in wells ZK5–ZK7 (north) and ZK1–ZK2 (south) reflect the influence of aquifer structure variability, recharge sources, and local hydrogeochemical conditions. CFC-12 concentrations exhibit a clear freshwater–saltwater mixing gradient between ZK3 and ZK1, with higher concentrations in freshwater-dominated areas (ZK3–ZK7) and lower concentrations near seawater (ZK1). CCl₄ concentrations at ZK7 and ZK3 differ markedly from other wells, indicating unique hydrogeochemical conditions or localized anthropogenic influences. A model for the formation of upper saline plumes (USP) under tidal forcing at the low tidal line was established previously. Here, we establish a new model that accounts for the absence of USP driven by hydrological processes influenced by artificial sandy beach topography, and a fresh groundwater wedge is identified, which can serve as a significant fast-flow pathway for terrestrial water and nutrients to the ocean. Full article

The offshore transport of coastal water masses in the East China Sea is vital for maintaining ecological stability. Understanding its spatial-temporal pathways helps clarify material transport and ecological responses. This study used total suspended sediment (TSS) data from the Korean Geostationary Ocean Color Imager to analyze TSS distribution and anomalies, combined with satellite-derived surface residual currents. Results show significant seasonal variations: coastal water masses expand to the 50 m isobath in winter and contract to the 20 m isobath in summer. Offshore transport pathways vary spatially, extending to the shelf edge north of 28° N but restricted by the Taiwan Warm Current south of 28° N. A persistent transport pathway near 28° N shifts from northeastward to eastward. Other pathways include one south of Hangzhou Bay (spring and autumn) linked to tidal mixing and another north of the Yangtze River estuary (summer) following the Yangtze River Diluted Water. These findings provide crucial observational insights for modeling material cycling in the East China Sea shelf. Full article

High-resolution (2 km), high-frequency (hourly) SST data of the Advanced Himawari Imager (AHI) flown onboard the Japanese Himawari-8 geostationary satellite were used to derive the monthly climatology of temperature fronts in the South China Sea. The SST data from 2015 to 2022 were processed with the Belkin–O’Reilly algorithm to generate maps of SST gradient magnitude GM. The GM maps were log-transformed to enhance contrasts in digital maps and reveal additional features (fronts). The combination of high-resolution, cloud-free, four-day-composite SST imagery from AHI, the advanced front-preserving gradient algorithm BOA, and digital contrast enhancement with the log-transformation of SST gradients allowed us to identify numerous mesoscale/submesoscale fronts (including a few fronts that have never been reported) and document their month-to-month variability and spatial patterns. The spatiotemporal variability of SST fronts was analyzed in detail in five regions: (1) In the Taiwan Strait, six fronts were identified: the China Coastal Front, Taiwan Bank Front, Changyun Ridge Front, East Penghu Channel Front, and Eastern/Western Penghu Islands fronts; (2) the Guangdong Shelf is dominated by the China Coastal Front in winter, with the eastern and western Guangdong fronts separated by the Pearl River outflow in summer; (3) Hainan Island is surrounded by upwelling fronts of various nature (wind-driven coastal and topographic) and tidal mixing fronts; in the western Beibu Gulf, the Red River Outflow Front extends southward as the Vietnam Coastal Front, while the northern Beibu Gulf features a tidal mixing front off the Guangxi coast; (4) Off SE Vietnam, the 11°N coastal upwelling gives rise to a summertime front, while the Mekong Outflow and associated front extend seasonally toward Cape Camau, close to the Gulf of Thailand Entrance Front; (5) In the Luzon Strait, the Kuroshio Front manifests as a chain of three fronts across the Babuyan Islands, while west of Luzon Island a broad offshore frontal zone persists in winter. The summertime eastward jet (SEJ) off SE Vietnam is documented from five-day mean SST data. The SEJ emerges in June–September off the 11°N coastal upwelling center and extends up to 114°E. The zonally oriented SEJ is observed to be located between two large gyres, each about 300 km in diameter. Full article

This study provides a comprehensive examination of colliding density currents with a range of density differences from 1% to 4%, using controlled laboratory experiments with saltwater and freshwater. The research reveals that when density currents collide, they generate internal bore, with the denser fluid flowing consistently beneath the lighter fluid. A significant finding is the temporary stalling and oscillatory motion of the current fronts during collisions, which is linked to a partial dissipation of kinetic energy and the subsequent formation of internal waves. Numerical simulations showed close agreement with experimental observations, reproducing the location of the tidal fronts well and verifying the accuracy of the hydrodynamic model used. Moreover, the study demonstrates that collisions between fluids with different densities notably enhance diffusion and mixing efficiency. This has important implications for environmental science, particularly in understanding and predicting density-driven fluid dynamics in aquatic systems such as estuaries and coastal zones. The enhanced mixing efficiency observed could be crucial for applications in environmental and pollution control, offering insights into material transport and pollutant dispersion. Full article

Power generation is affected and structural instability may occur when biofouling attaches to the rotor of tidal stream turbines (TSTs). Image signals are used to identify biofouling for biofouling recognition, thus achieving on-demand maintenance, optimizing power generation efficiency, and minimizing maintenance costs. However, image signals are sensitive to background interferences, and underwater targets blend with the water background, making it difficult to extract target features. Changes in water turbidity can affect the effectiveness of image signal biofouling recognition, which can lead to reduced recognition accuracy. In order to solve these problems, a multi-view and multi-type feature fusion (MVTFF) method is proposed to recognize rotor biofouling on TSTs for applications in TST operation and maintenance. (1) Key boundary and semantic information are captured to solve the problem of background feature interference by comparing and fusing the extracted multi-view features. (2) The local geometric description and dependency are obtained by integrating contour features into multi-view features to address the issue of the target mixing with water. The mIoU, mPA, Precision, and Recall of the experimental results show that the method achieves superior recognition performance on TST datasets with different turbidity levels. Full article

The water quality in port domains is highly dependent on the capacity for renewal and mixing with external water. This study uses Lagrangian modelling to investigate renewal time in Barcelona, Tarragona, and Gijón harbours (Spain), which represent semi-enclosed micro-tidal and meso-tidal environments. For this purpose, different particle-tracking simulations have been carried out in each of the ports to study the trends of circulation and water renewal trends both on the surface layer and at the bottom. The results indicate that in microtidal Mediterranean ports, the renewal time is longer at the bottom (32 days in Barcelona and 61 days in Tarragona). Conversely, in the mesotidal port of Gijón, located on the Cantabrian coast, the opposite pattern is observed, with higher renewal times at the surface (14 days). While the results from Lagrangian modelling exhibit magnitudes comparable to in situ measurements from previous studies, it remains essential to evaluate the specific characteristics of each method and compare these findings with other similar works. Full article

As the world transitions towards a low-carbon economy, understanding the employment implications of renewable energy growth is crucial, particularly in emerging economies like the BRICS nations, where energy demand and employment pressures are rapidly evolving. The justification for this study lies in the critical need to understand the employment effects of renewable energy growth in emerging economies, particularly in the BRICS nations, which account for a significant share of global energy demand and are poised to drive the next wave of renewable energy adoption. As these countries navigate the challenges of energy transition, employment creation, and sustainable development, this research aims to provide timely and actionable insights for policymakers, industry stakeholders, and researchers seeking to optimize the employment benefits of renewable energy growth in these regions. The purpose of this study is to investigate the impact of disaggregated renewable energy (solar, hydro, wind, nuclear, and other renewables including bioenergy) on employment dynamics in BRICS nations, so as to provide empirical evidence on the employment effects of renewable energy growth in these regions. The key findings from the study are summarized as follows: Hydro contributes positively to employment creation in BRICS nations, with FMOLS (0.78%), DOLS (2.06%), and PCSE (0.61%) results showing significant positive effects. Solar contributes positively to employment creation in BRICS nations, with FMOLS (1.99%) and DOLS (9.60%) results showing significant positive effects, although country-specific results are mixed. Economic growth contributes positively to employment creation in BRICS nations, with FMOLS (32.93%), DOLS (36.86%), and PCSE (27.68%) results showing significant positive effects. Wind contributes negatively to employment creation in BRICS nations at the aggregate level (FMOLS, −0.66%), but has positive effects in some countries (Brazil, China, Russia, and South Africa). Nuclear contributes negatively to employment creation in BRICS nations at the aggregate level (FMOLS, −0.47%; PCSE, −1.04%), but has positive effects in some countries (Russia, India, China, and South Africa). Other Renewables contribute negatively to employment creation in BRICS nations, with FMOLS (−2.57%) and PCSE (−4.77%) results showing significant negative effects. Policymakers in BRICS nations should prioritize investments in hydropower, solar power, and wind power to leverage their job creation potential and promote sustainable economic growth. Additionally, governments should implement policies to support the development of other renewable energy sources, such as bioenergy, geothermal, and tidal power, to increase their job creation potential. Furthermore, policymakers should promote economic growth through green investments and sustainable development initiatives to maximize employment creation in the renewable energy sector. Full article

The growing need for sustainable energy solutions has propelled the development of Hybrid Renewable Energy Systems (HRESs), which integrate diverse renewable sources like solar, wind, biomass, geothermal, hydropower and tidal. This review paper focuses on balancing economic, environmental, social and technical criteria to enhance system performance and resilience. Using comprehensive methodologies, the review examines state-of-the-art algorithms such as Multi-Objective Particle Swarm Optimization (MOPSO) and Non-Dominated Sorting Genetic Algorithm II (NSGA-II), alongside Crow Search Algorithm (CSA), Grey Wolf Optimizer (GWO), Levy Flight-Salp Swarm Algorithm (LF-SSA), Mixed-Integer Linear Programming (MILP) and tools like HOMER Pro 3.12–3.16 and MATLAB 9.1–9.13, which have been instrumental in optimizing HRESs. Key findings highlight the growing role of advanced, multi-energy storage technologies in stabilizing HRESs and addressing the intermittency of renewable sources. Moreover, the integration of metaheuristic algorithms with machine learning has enabled dynamic adaptability and predictive optimization, paving the way for real-time energy management. HRES configurations for cost-effectiveness, environmental sustainability, and operational reliability while also emphasizing the transformative potential of emerging technologies such as quantum computing are underscored. This review provides critical insights into the evolving landscape of HRES optimization, offering actionable recommendations for future research and practical applications in achieving global energy sustainability goals. Full article