Search Results (741)

This study analyzes surface air temperature (SAT) trends at 158 stations located on or above the Arctic Circle over the 2000–2024 period, aiming to assess whether recent temperature shifts could serve as indirect indicators of a slowing Atlantic Meridional Overturning Circulation (AMOC). Regression analysis reveals that only 40% of stations show statistically significant warming trends (p < 0.05), while 33% exhibit no significant trend. Applying the Pettitt and Buishand tests, we detect abrupt regime shifts at 38 stations, with breakpoints concentrated between 2009 and 2014. Notably, 36 of these stations display a weakening of the warming trend after the breakpoint: at 13 stations (including key Arctic archipelagos and the White Sea coast), an initial increase shifts to a decrease; at 17 stations, warming continues but at a slower rate; and at 6 stations (near the Bering Strait), a decrease intensifies. These spatial patterns suggest a potential fingerprint of AMOC slowdown, consistent with recent modeling studies that predict cooling in northwestern Europe and possible Little Ice Age-type environmental conditions. Our findings have implications for assessing future Arctic navigation, coastal infrastructure, and resource extraction under changing climate regimes. Full article

Numerous space missions are advancing our understanding of the origin and evolution of planetary bodies and the potential for the emergence of life throughout the Solar System and beyond. Investigations across the inner Solar System have revealed contrasting planetary environments: Venus offers insights into runaway greenhouse processes, while Mars remains a primary target for studying climate evolution, atmospheric loss, past water activity, and extinct life, with sample return missions planned in the next decade. Beyond the traditional habitable zone, attention has shifted to the icy moons of Jupiter and Saturn. Data from space missions have identified subsurface oceans and possibly active geology on moons such as Europa, Ganymede, Titan, and Enceladus, highlighting their astrobiological potential. Among others, Europa’s ocean, possibly interacting with a silicate mantle and sustained by tidal heating, Enceladus plumes and Titan’s complex organic chemistry make these worlds compelling targets. Current and upcoming missions will further explore these environments and refine our understanding of habitability. This work also emphasizes the importance of planetary protection to prevent biological contamination, particularly for sample return missions. Continued exploration, supported by international collaboration and technological innovation, will be essential to address engineering challenges and to expand our knowledge of potentially habitable environments across the Solar System. Full article

The global transition to a diversified renewable energy portfolio requires reliable assessment of predictable marine energy resources. This study develops a high-resolution, three-dimensional Regional Ocean Modeling System (ROMS) to quantitatively evaluate theoretical tidal current energy resources in the Bohai and Yellow Seas. The model, configured with fine-scale bathymetry and forced by harmonic tidal constituents, is validated against tide gauge and Acoustic Doppler Current Profiler (ADCP) observations. Multi-year simulations reveal pronounced spatial heterogeneity in tidal current energy distribution. Rather than treating resource assessment as a single power density mapping exercise, this study combines annual mean theoretical power density, peak theoretical power density, threshold-dependent effective flow duration, effective water depth, current directionality, and vertical velocity structure to characterize resource intensity, temporal persistence, and vertical deployability. The results identify distinct hydrodynamic resource regimes. High theoretical resource intensity is concentrated west of Laotieshan Cape and east of Chengshantou, where cumulative annual effective flow duration exceeds 5000 h and short-term instantaneous theoretical power density can reach approximately 10 kW/m² and 8 kW/m², respectively. These peak values indicate strong local tidal acceleration but should be interpreted together with annual mean power density and effective flow duration. In contrast, the northern Jiangsu coastal area exhibits lower peak intensity but relatively persistent moderate flow conditions. The results provide a hydrodynamic resource basis for preliminary site screening and for guiding subsequent turbine-performance, wake/array, environmental, grid accessibility, and techno-economic assessments. Full article

Achieving precise docking, reliable locking and damage-free emergency unlocking under complex ocean current conditions remains a key challenge for deep-water multi-way quick connectors (MQCs). This study proposes a novel MQC prototype characterised by a tiered tolerance guidance mechanism, an innovative L-shaped spatial helical cam locking system, and a real-time visual attitude indicator. Using Ansys 2023 R2 and its tools, the safe operating limits were determined through explicit non-linear finite element collision analysis. The results demonstrate that, under a controlled docking speed of 10 mm/s, the hierarchical guidance mechanism successfully accommodated extreme initial misalignments (25 mm lateral offset, 5° horizontal rotation and 15° axial rotation), whilst keeping the peak collision stress within the elastic limit. Furthermore, the L-shaped locking guide was analysed using a fifth-order polynomial motion law and a macro-micro elastoplastic Hertzian contact mechanics model, effectively eliminating rigid-flexible impact forces. Under extreme separation loads of 10,000 psi, the maximum equivalent plastic strain at the base of the locking shaft was strictly controlled at 0.00926. This is well below the failure threshold of 0.0865 specified by ASME, providing a substantial safety margin and completely preventing local yielding. Crucially, the emergency release strategy based on precision locating pins was validated through full-scale prototype testing. Destructive tests conducted under simulated severe jamming conditions demonstrated clean, damage-free disengagement under shear torques ranging from 2100 Nm to 2200 Nm. This threshold ensures that accidental triggering will absolutely not occur during routine operations (1400 Nm) and establishes a safe underwater robotic (ROV) operating speed of ≤4 r/min. This study provides a robust theoretical framework and empirical data for the future design of yield-resistant subsea connectors and safe emergency recovery. Full article

Located in the northern South China Sea (SCS), the Guangdong Sea areas exhibit a highly complex hydrodynamic structure driven by the combined effects of tides, monsoons, and offshore current systems, serving as a core region for China’s marine economy and offshore engineering. Although the Regional Ocean Modeling System (ROMS) is widely applied in current simulations, its accuracy is often constrained by the inadequate adaptability of its parameterization schemes to the regional environment. Furthermore, systematic parameter optimization tailored to this specific domain remains scarce. To address these limitations, this study conducts an observation-driven parameter optimization for surface current simulations in the western Guangdong Sea areas, aiming to enhance the reliability of hydrodynamic simulations and forecasting. A three-dimensional ROMS hydrodynamic model was employed to systematically design 18 physical parameterization experiments. The model’s performance was rigorously evaluated against 26 h continuous in situ current measurements from four observation stations, utilizing statistical metrics including the correlation coefficient (R), root mean square error (RMSE), Taylor diagrams, and the MMS standardized evaluation. The results indicate that the Mellor–Yamada vertical mixing scheme yields the optimal regional adaptability. For horizontal diffusion, the biharmonic scheme outperforms the Laplacian approach. Regarding bottom friction, the logarithmic formulation demonstrates superior accuracy compared to the quadratic and linear schemes, with the latter proven unsuitable for this region. A comprehensive evaluation identifies the ‘MY–Biharmonic–Logarithmic’ combination as the optimal parameterization configuration for the western Guangdong Sea areas. This study establishes an adaptable ROMS parameterization framework for the western Guangdong Sea areas and elucidates the influence mechanisms of key physical parameters on simulation outcomes. These findings not only provide high-precision hydrodynamic support for short-term pollutant dispersion forecasting, and disaster mitigation in this region but also offer valuable methodological references for numerical modeling in the broader SCS and analogous complex coastal environments. Full article

Interannual climate variability exerts a strong control on the thermohaline structure of eastern boundary upwelling systems, particularly in transition zones where distinct water masses converge. Seasonal and interannual variability in temperature and salinity were examined in the southern California Current System for the period 2000–2015 using hydrographic observations and satellite altimetry, analyzed by season and ENSO phase. During El Niño, the upper 100 m exhibits positive temperature and salinity anomalies of 1–2 °C and ~0.1–0.2 g kg⁻¹ associated with 50–80 m isopycnal deepening, reduced upwelling-induced ventilation, the expansion of subtropical waters onto the shelf, and enhanced poleward geostrophic transport. In contrast, La Niña conditions shoal isopycnals, enhances upper-layer stratification, and sustains equatorward flow throughout the year. Temperature and salinity anomalies extend below 100 m, suggesting a remote reorganization of the baroclinic structure at the shelf–ocean boundary. Salt fingering is inferred to be the dominant non-conventional mixing process in the region, with peak occurrence in autumn. These results highlight that ENSO confines thermohaline reorganization to the inner continental shelf (~150 km), modulates coastal–ocean density gradients, weakens equatorward geostrophic transport during El Niño, and alters coastal–ocean heat and salt exchanges within the southern CCS transition zone. Full article

With the rising trend of replacing synchronous generators with inverter-based resources, the grid inertia, frequency control, voltage stability, and fault ride-through are compromised. The current research focuses on the coordinated control of Voltage Source Converter-based HVDC (VSC HVDC) and Battery Energy Storage Systems (BESS) for improving the grid stability in the presence of intermittent sources. Two models are created in the MATLAB/Simulink 2025a environment: one for the grid-connected PV system with the addition of BESS in grid-forming mode (GFM) and grid-following mode (GFL), and the other for the multi-terminal HVDC system with the integration of wind energy from the ocean. The results show that the grid-forming converters perform better than grid-following converters in the event of disturbances, and the coordinated control structure aligns with the IEEE 2800-2022 for low-inertia grids. Full article

The shift from fossil fuels to renewable energy is a key component in achieving global sustainability and dealing with climate change. Natural resources, such as sunlight, air, water, and biomass, have tremendous potential to create clean energy; however, exploiting these resources in an efficient, stable, and large-scale integration manner is difficult due to their variable and distributed nature. Artificial intelligence (AI) approaches that mimic human learning and decision-making have recently become viable approaches to solving renewable energy problems. This study mainly examines the current landscape of AI applications across solar, wind, hydro, geothermal, ocean, hydrogen, bioenergy, and hybrid energy systems. AI enhances renewable energy forecasting, improves power system frequency analysis and stability assessments, and optimizes dispatch and distribution networks. Beyond technical optimization, AI also contributes to broader sustainability goals, including energy efficiency improvements, intelligent smart grid management, and enabling mechanisms such as carbon trading and circular economy practices to reduce exposure to climate extremes. Drawing on evidence from a range of renewable energy areas, this review highlights the importance of AI in bridging the link between technological innovation and sustainable energy management. This paper discusses potential future research avenues, such as building sophisticated AI designs, energy-efficient chips, and data communication networks. Ultimately, the synergy between AI and renewable energy systems represents not only a technological advancement but also a transformative pathway toward a resilient, low-carbon future. Full article

As the core pillar of international trade, the global shipping industry has seen its carbon and pollutant emissions become a key challenge in global environmental governance. Statistics indicate that ship carbon emissions account for 3% of the world’s total anthropogenic CO₂ emissions, while contributing 20% of global NO_x and 12% of SO₂ emissions, posing a serious threat to coastal ecosystems and public health. In response to the International Maritime Organization (IMO) “Net Zero Framework” and national green shipping policies, the transformation of ship power systems toward low-carbon and zero-carbon operation has become an inevitable trend. This paper systematically reviews the research progress and application status of green energy materials for ships, focusing on the working principles, technical characteristics, and engineering application cases of solar photovoltaic (PV) materials, wind energy utilization technologies, fuel cell materials, and alternative clean energy fuels (e.g., liquefied natural gas (LNG), methanol, and hydrogen energy). It also discusses the integration mode and optimization strategy of multi-energy hybrid power systems. The research findings show that solar photovoltaic technology has achieved large-scale application in coastal ships; hydrogen fuel cells are suitable for long-range ocean navigation scenarios due to their high energy density; LNG and methanol have become the current mainstream alternative fuels, relying on mature infrastructure; and hybrid energy systems can significantly improve power supply reliability and emission reduction efficiency through multi-energy complementarity. Finally, aiming at the existing bottlenecks (e.g., cost, energy storage, and safety) of various technologies, future development directions are proposed. This study provides a reference for the technological breakthrough and engineering practice of green energy power systems for ships and contributes to the realization of the “carbon neutrality” goal in the global shipping industry. Full article

Offshore oil and gas exploitation is one of the riskiest businesses to invest in and is dominated by various uncertainties: high deepwater pressure, low temperatures, remote operation, long-distance tiebacks and transportation, as well as environmental factors such as wind, waves and ocean currents. Serving as a profitability threshold, the minimum economic field size is defined as the economic recoverable reserve level that an oilfield must exceed to achieve economic returns. This paper develops an approach for determining the minimum economic field size of offshore oil and gas reservoirs. It categorizes the capital expenditure into four major components: drilling and completion costs, platform costs, pipeline costs, and subsea production system costs. The regression models of drilling costs and subsea production costs are developed respectively, with water depth and recoverable reserves as key influencing factors. The pipeline costs are estimated using the unit pipeline cost per mile and pipeline length. A profit model for the offshore field is established under the constraints of the contract, which allocates the oilfield’s production profits between the contractor and the government according to the contractual fiscal terms. Finally, taking the Lucius oilfield in the Gulf of Mexico as a case study, the paper simulates its investment, operating costs, and oilfield revenues. The minimum economic field size is calculated, accompanied by the derivation of the sensitivity boundaries for the primary parameters. Full article

With the constant increase in the usage of plastic bottles in food production, ocean pollution has become a significant problem. The ability to organize in large fields is one of the critical problems nowadays, and their detection for further removal is a challenge. In this study, we propose the idea of equipping some of the plastic bottles on the production lines with simple radio-emitting equipment capable of signaling the presence of plastic bottle fields in the ocean to nearby vessels. The proposed idea is based on ultra-low-power energy harvesting that utilizes inherent wave energy. To assess the performance of the proposed framework, we developed a performance evaluation framework that captures the main specifics of the proposed detection system, including the probability of detecting at least one waste field and all waste fields in a given region. To showcase the potential of the proposed idea in this study, we also demonstrate that ultra-low-power harvesting using ocean waves is feasible. Our numerical results illustrate that for typical environmental parameters, the time range for detecting all waste fields in the area scales from 4–6 h to a few days at most. Additionally, the probability of detecting the presence of waste in the area is 2–3 times higher, potentially allowing for extremely fast detection and timely removal. We emphasize that the proposed system can be used to complement the currently available systems, not to replace them completely. Full article

This study proposes an integrated task–path cooperative optimization method to address the suboptimal solutions caused by decoupled task allocation and path planning for grouped multi-USV formations. First, an integrated optimization model is established within a hierarchical dynamic closed-loop framework, incorporating a persistent ocean current disturbance of 0.12 m/s to ensure practical environmental realism. Furthermore, efficient solution algorithms are developed: an enhanced Hungarian algorithm for task allocation and a Sine Cosine Algorithm-optimized Artificial Potential Field (SCA-APF) method to resolve local minima. The simulation results demonstrate that the proposed method reduces the weighted total cost by 11.1% and improves task allocation efficiency by over 80.5% compared to improved genetic algorithms. In dynamic environments, the framework achieves an over 99% task completion rate. Crucially, the system maintains real-time responsiveness with per-step computation times below 0.1 s even for a swarm size of N = 32, proving its scalability and suitability for large-scale maritime coordination. Full article

High-resolution vertical profile observations of ocean environmental parameters are essential for investigating mesoscale ocean dynamic phenomena, such as internal waves, mesoscale eddies, and oceanic fronts. At present, vertical profile measurement in marine surveys mainly relies on shipborne winches to deploy and recover marine sensors, which entails high labor costs and considerable energy consumption. Unmanned observation platforms integrated with winch systems enable automatic sensor deployment and recovery, offering a viable approach to cutting observation costs. Nevertheless, inadequate energy supply remains a critical bottleneck restricting the large-scale popularization and application of such equipment. Accordingly, the development of high-efficiency winch systems tailored for unmanned autonomous observation platforms is of great engineering significance for facilitating long-term, continuous, and low-energy marine profile observation. This paper proposes a novel energy-saving winch with an embedded three-stage parallel nested energy storage structure for unmanned marine observation platforms. During operation, the coil spring energy storage system is charged during cable payout, and the stored elastic potential energy is released to assist motor driving in the cable retraction process. This auxiliary driving mode reduces motor power demand and improves the overall energy utilization efficiency of the platform. Experimental results demonstrate that, neglecting ocean current resistance, the proposed winch reduces energy consumption by 5% during cable payout and 21% during cable retraction. The overall energy consumption is decreased by 13% throughout a complete vertical profile measurement cycle. Under constrained and fixed energy supply conditions, this technology substantially enhances the sampling capability of unmanned marine platforms for ocean environmental monitoring. It further improves operational efficiency and extends continuous service time, providing key technical support for revealing ocean dynamic evolution and clarifying the formation and driving mechanisms of marine environmental phenomena. Full article

The circulation of the North Atlantic Ocean plays a vital role in the Earth’s climate system. Numerous studies, primarily through computer simulations, have examined the stability of the Atlantic Meridional Overturning Circulation (AMOC) in a warming climate. Some of these studies predict a potential collapse of the AMOC in the foreseeable future, which would require a significant influx of freshwater into the subpolar North Atlantic (NA) and Nordic Seas. Paleoreconstructions of NA circulation indicate a major shift in the position of the subpolar cold front, which either precedes or coincides with substantial changes in AMOC dynamics. These changes in the front position imply a significant alteration in circulation patterns, beginning with the noticeable restructuring of the subtropical and subpolar gyres. This would lead to modifications in the Gulf Stream system and the North Atlantic Current (NAC), affecting the thermohaline fields and the position and strength of these two current systems. Although some models predict a significant slowdown or even collapse of the AMOC, recent observational studies have offered a more cautious perspective. For instance, the Gulf Stream system exhibits high resilience to perturbations caused by ongoing sea surface warming. In this study, we analyzed the decadal variability of temperature and salinity from in situ observations, along with upper-ocean currents in the subpolar NA (SPNA). We found that the thermohaline pattern of the upper ocean layers in the SPNA and Nordic Seas has remained resilient for over 70 years. The deceleration of the AMOC is evident but relatively modest, with average velocities in the upper layers decreasing by less than 10–15% over 30 years. This deceleration was also inconsistent throughout the NAC region. Furthermore, the subpolar front migration over 70 years, as manifested in isotherm spatial variability, reached a maximum of 3° of latitude, with spatial variability of the yearly 10 °C isotherms being lower. Overall, the conclusion regarding the resilience of the NAC aligns well with that of the Gulf Stream, with no substantial changes in the position or intensity of the subpolar gyre. We conclude that while the AMOC is susceptible to some deceleration due to ongoing surface warming and/or high-latitude freshening, it may also be sufficiently resilient to withstand these changes. Although it cannot be entirely ruled out that the AMOC may reach its tipping point within this century, an analysis of data on decadal variability in the upper arm of the AMOC suggests that such a collapse is unlikely to occur. Full article

Submesoscale oceanic eddies play a crucial role in ocean dynamics and climate systems, while Synthetic Aperture Radar (SAR) offers distinct advantages for observing these fine-scale phenomena; the advancement of automated detection algorithms is currently hindered by the lack of publicly available, high-quality benchmark datasets. To address this gap, this paper constructs a universal benchmark dataset for submesoscale eddies and presents an improved anchor-free object detection framework based on Fully Convolutional One-Stage (FCOS). We propose two key innovations: (1) a Deep Fusion Feature Pyramid Network (DF-FPN) that integrates adaptive multi-scale feature fusion directly into the pyramid construction process through deep fusion Adaptive Spatial Feature Fusion (ASFF) modules, enabling bidirectional feature enhancement and global context-aware fusion and (2) a Pixel-level Statistical Description Learning (PSDL) module that enhances feature representation by learning statistical descriptors across multiple scales. The DF-FPN replaces traditional staged optimization with an intrinsic deep fusion paradigm, significantly improving feature quality. Extensive experiments on our constructed dataset demonstrate that our method achieves 66.6% mAP, 91.3% AP₅₀, and 80.5% AP₇₅. These results represent a substantial improvement over the FCOS baseline and outperform other state-of-the-art detectors, providing a robust and efficient solution for operational submesoscale eddy monitoring in SAR imagery. Enhanced detection capacity of this kind offers a critical observational foundation for advancing research on upper-ocean nutrient transport, carbon cycle dynamics, and the dispersion of marine pollutants, thereby supporting broader environmental monitoring and climate-related objectives. Full article