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ABSTRACT We review and describe the electromagnetic transmitters and receivers used to carry out magnetotelluric and controlled source soundings in the marine environment. Academic studies using marine electromagnetic methods started in the 1970s but during the last decade these methods have been used extensively by the offshore hydrocarbon exploration industry. The principal sensors (magnetometers and non-polarizing electrodes) are similar to those used on land but magnetotelluric field strengths are not only much smaller on the deep sea-floor but also fall off more rapidly with increasing frequency. As a result, magnetotelluric signals approach the noise floor of electric field and induction coil sensors (0.1 nV/m and 0.1 pT) at around 1 Hz in typical continental shelf environments. Fluxgate magnetometers have higher noise than induction coils at periods shorter than 500 s but can still be used to collect sea-floor magnetotelluric data down to 40-100 s. Controlled source transmitters using electric dipoles can be towed continuously through the seawater or on the sea-bed, achieving output currents of 1000 A or more, limited by the conductivity of seawater and the power that can be transmitted down the cables used to tow the devices behind a ship. The maximum source-receiver separation achieved in controlled source soundings depends on both the transmitter dipole moment and on the receiver noise floor and is typically around 10 km in continental shelf exploration environments. The position of both receivers and transmitters needs to be navigated using either long baseline or short baseline acoustic ranging, while sea-floor receivers need additional measurements of orientations from compasses and tiltmeters. All equipment has to be packaged to accommodate the high pressure (up to 40 MPa) and corrosive properties of seawater. Usually receiver instruments are self-contained, battery powered and have highly accurate clocks for timekeeping, even when towed on the sea-floor or in the water column behind a transmitter. [ABSTRACT FROM AUTHOR]

Optimal sizing and management of hybrid wind turbine-diesel-battery system for reverse osmosis seawater desalination in NEOM city is the objective of the paper. Therefore, the paper explored the different factors to optimize and introduce a technoeconomic evaluation and energy management of a stand-alone wind turbine (WT) system, diesel generator (DG), and battery storage (BS). The suggested WT/DG/BS system is implemented to feed seawater reverse osmosis (SWRO) unit in NEOM. The necessitated desalinated water per day is 100 m3. To determine the optimal size of WT/DG/BS corresponding to the minimum cost of energy (COE) and net present cost, two different ratings of the SWRO units (SWRO-100 and SWRO-150), three control dispatch strategies (load following, cycle charging, and combined dispatch), and five types of batteries are considered. HOMER software is performed to simulate and optimize the WT/DG/BS. The optimization results indicated that the best battery storage is the Trojan SAGM battery. In this case, the COE ranged between $0.337/kWh and $0.564/kWh. The lowest COE of $0.377/kWh is obtained when using a combined control strategy and SWRO-100 unit, whereas the worst COE of $0.564/kWh is obtained when using load following control strategy and SWRO-150 unit. The best option of the WT/DG/BS system to supply the SWRO unit is option number 26. This system includes one wind turbine of 90 kW, DG of 25 kW, 47 Trojan SAGM batteries, a 23.8 kW converter, a SWRO-100 unit, and a combined control strategy. The net present cost and the initial cost are $950,725 and $221,495, respectively. The annual operating cost and annual consumed fuel are $56,409 and 36,396 L, respectively. Compared with using only a 25 kW diesel generator, the COE reduced from $0.373/kWh (using only DG/BS) to $0.337/kWh (using the best option) by around 9.65%. Under this condition, the values for the internal rate of return, return on investment, and simple payback are 11%, 7.8%, and 8.3 years, respectively. [ABSTRACT FROM AUTHOR]

The use of cementitious materials in deep sea environments, focusing on the durability challenges of low‐temperature seawater and hydraulic pressure, are presented in this paper. The authors conducted laboratory and deep‐sea field experiments, thermodynamic calculation, and evaluated the performance of different types of binders in deep sea conditions. Durability of rebar in cementitious materials was investigated. In situ construction methods using cementitious materials was demonstrated on the deep‐sea field. Testing results revealed that deep sea conditions, especially low‐temperature seawater, can accelerate the disintegration of cement hydrates, and the use of pozzolanic admixture and calcium aluminate cement can improve its resistance. Our study provides valuable insights and applicability of cementitious materials to deep sea infrastructure construction. [ABSTRACT FROM AUTHOR]

Global freshwater shortage is forcing researchers to focus on seawater electrolysis for large‐scale green hydrogen production. Seawater purification by reverse osmosis (RO) for use in conventional water electrolyzers (WEs) is another approach, however, that requires large capital investments. Alternatively, seawater can be used directly in a novel type of anion exchange membrane WE (AEMWE) which is currently under development. The AEMWEs have the advantage of using non‐precious catalysts and are less sensitive to the presence of impurities. Success in this early‐stage technology relies on the development of efficient and durable electrocatalysts. This paper provides a comprehensive review of the status and future trends for developing catalysts operating directly with seawater. Catalysts are ranked based on their activity and durability at high current densities of 500 mAcm−2 and 1000 mAcm−2. Notable anode catalysts, S−NiFe2O4, and NiFe LDH, exhibit reduced OER overpotentials of 287 mV and 296 mV at 1000 mAcm−2. Top‐performing cathode HER catalysts include HW−NiMoN‐2 h (132 mV) and Pt−Co−Mo (117 mV) at 1000 mAcm−2. Bifunctional catalysts, such as CoxPv@NC can operate below an overall voltage of 2 V at 1000 mAcm−2. This comparative analysis provides researchers and professionals with critical insights for advancing direct seawater electrolysis. [ABSTRACT FROM AUTHOR]

Atmospheric moisture accelerates the triboelectric charge transport and dissipation in the triboelectric nanogenerator (TENG). However, the output of polyvinyl alcohol (PVA)‐based humidity‐resistant TENG is still limited under high humidity and suffers from the swelling problem in practical application. In this paper, a swelling‐ and humidity‐resistant high‐performance TENG using a polyacrylonitrile/polyvinyl alcohol‐calcium chloride (PAN/PVA‐CaCl2) composite film (PPCa‐TENG) is designed for seawater desalination. The PAN/PVA‐CaCl2 composite films exhibit superior water uptake speed, swelling resistance, and mechanical and tribological properties compared with other prepared membranes at high relative humidity (RH). The maximum short‐circuit current (Isc) and output voltage (Vo) of the PPCa‐TENG can reach 52.04 µA and 941 V at 75% RH, respectively, with increasing the power of PVA‐based TENG by about 17.39 times. The Kelvin probe force microscopy (KPFM) results suggest that the PAN/PVA‐CaCl2 composite film demonstrates a higher tribopositivity. Furthermore, the PPCa‐TENG is applied as an effective, economical power source for seawater desalination, with an energy consumption of only 0.19 kWh m−3. This number is remarkably lower than that of desalination powered by conventional direct‐current power supplies reported in previous work. This paper provides a feasible, effective method for the design of the TENG with high performance under high‐humidity conditions. [ABSTRACT FROM AUTHOR]

Electrochemical water treatment for recirculating aquaculture systems (RAS) is a promising approach for replacing the biological water treatment methods and establishing a new RAS generation with improved cost‐effectiveness, lower environmental footprint, and no start‐up periods. On top of ammonia oxidation directly into N2(g), electrochemical oxidation results in effective disinfection, and in the removal of organic matter, including specific organic constituents such as off‐flavour agents. The paper provides an overview of incentives for the implementation of electrochemical methods in RAS. It covers the electrochemical principles relevant to aquaculture applications, the effects of physical and chemical parameters, as well as design considerations. In addition, the research performed to date for integrating electrochemical methods in RAS operation is reviewed and the variety of designs and operational configurations described. The electrochemical water treatment is perceived beneficial over biological water treatment especially in cold saline‐seawater aquaculture (e.g., Atlantic salmon), where large nitrification reactors are required and the large water consumption for purging processes can be curtailed. It is also beneficial for the culturing of nitrate‐sensitive species (e.g., L. vannamei). The paper points out the gaps to be overcome for allowing commercial breakthroughs based on electrochemical water treatment, including the need for expanding the practice and improving engineering practices by operating pilot systems for growing fish at both small and large scales; adjusting of electrochemical cell designs for reducing both capital and operational costs; developing full‐proof malfunction‐free dechlorination strategies, and evaluating and optimizing the disinfection abilities for inactivating typical pathogens in aquaculture. [ABSTRACT FROM AUTHOR]

Estuary bays are vulnerable to salinization effects due to relative sea level rise and modification in upland hydrology owing to a variety of factors. Much research has evaluated the one‐sided effect of runoff discharge or sea level on the water exchange and saltwater intrusion for an estuary, while their combined effects have not been evaluated, especially for an estuary bay with narrow river mouth. Taking the Wanquan Estuary Bay (WEB), China, as study case, this paper has revealed the long‐term significant increasing trend of freshwater runoff in non‐flood season during years 1956–2017 using the Man‐Kendall trend analysis, robust principle component regression and Theil–Sen's estimator. A 3‐D hydrodynamic‐salinity‐tracer numerical model is built and calibrated based on the finite‐volume community ocean model, and the effects of runoff increase and sea level rise on the water exchange and saltwater intrusion are investigated. This paper shows the following: (1) The freshwater runoff during non‐flood season in WEB shows significant long‐term increasing trend, and the mean changing magnitude is 0.4546 m3/s/a. (2) The increased runoff accelerates the water exchange, and reduces the turn‐over time and saltwater intrusion in the WEB. The sea level rise reduces the water exchange and increase the saltwater intrusion. (3) For the estuary bay with narrow river mouth, the salinity distributions show more vertical stratification characteristics. The freshwater runoff has power relationships with the average turnover time and salinity, and the sea level has linear relationships. (4) The water exchange and salinity of an estuary bay is more vulnerable to the changed runoff than the sea level rise, while the impacts of sea level rise would increase for estuaries with wide river mouth. This paper provides support for the freshwater exploitation and utilization in estuary bay under the background of climate change and sea level rise. [ABSTRACT FROM AUTHOR]

In this paper, the fracture durability of composite–titanium adhesively bonded structures exposed to seawater environment was studied experimentally and numerically. The specimens were immersed in artificial seawater at 45°C for different exposure times. The results show that the tensile strength of the specimen aging for 130 days degraded by nearly 55.6%, and the degradation of the mechanical properties of adhesive was not only affected by the moisture but also showed a certain relationship with aging time. Under the condition of saturated moisture, the tensile strength of the specimen still decreased with the increase of aging time. The simulated moisture results of the aging fracture specimen indicate that the moisture of the boundary region of the adhesive layer was mainly absorbed from the adhesive itself, while the moisture of the central region was dependent on the moisture absorption of the composite adherend. Moreover, the moisture absorption of the pre‐crack tip adhesive resulted in different load responses and fracture modes of the aging fracture specimens. Consequently, the fracture toughness of the DCB and ENF specimens aging for 180 days degraded by nearly 66.4% and 33.0%, respectively. Highlights: Degradation of adhesive was also related to aging time apart from moisture.Boundary and central region severally absorb water from adhesive and CFRP.Moisture of the pre‐crack tip adhesive affected load responses and fracture modes.After 180 days, fracture toughness of modes I and II degraded by 66.4% and 33.0%. [ABSTRACT FROM AUTHOR]

The permeation of marine water can lead to severe degradation of the protective properties of polymer composite coatings. At present, experimental studies on the anticorrosive and mechanical properties of polymer composite coatings are relatively mature, but the impermeability and mechanical property changes of the coating during the permeation process are challenging tasks to be studied only by experiments. In this paper, molecular dynamics (MD) models of composite coatings consisting of pure epoxy resin (EP), graphene/epoxy resin (Gr/EP), and graphene oxide/epoxy resin (GO/EP) were constructed respectively. MD simulations were performed to reveal the impermeability and mechanical property changes of composite coatings from an atomic perspective. The results show that GO has strong interfacial interaction with EP and the best effect to enhance the impermeability and mechanical properties of epoxy coatings. NaCl solutions can damage the coating microstructure and occupy the Gr and GO surfaces, causing them to no longer have an enhancing effect. The study of GO/EP coatings with different permeation degrees shows that the mechanical properties of the coating decrease as the penetration degree increases. [ABSTRACT FROM AUTHOR]

Planktonic animals drifting or floating in the sea have small body sizes and weights from hundreds to thousands of milligrams, and are primarily the food for other zooplankton and macrofauna: fish, cephalopods, seabirds and marine mammals, and also the larval pool of many benthic invertebrates. This paper describes a unique dataset of zooplankton collected from 1984 to 2013 in the North Pacific (the Bering Sea, Sea of Okhotsk, Sea of Japan and adjacent Pacific Ocean waters), one of the most productive and economically important regions of the world's oceans using a Juday net made of kapron sieve No. 49 (0.168 mm mesh) with a 0.1 m2 opening. The information in this dataset has already been used to quantify the inventory of marine biological resources and assess the waters of the Russian Far Eastern seas and adjacent Pacific Ocean. In 2016, five tabular reference books were printed in Russian in limited numbers containing the species composition, occurrence (number and percentage of samples), abundance and biomass (in individuals per cubic meter, milligrams per cubic meter) of zooplankton in the surveyed area. The data are grouped by species, developmental stages, size fractions (animal length of 0.6-1.2 mm "fine/small," 1.2-3.2 mm "medium" and >3.2 mm "large"), standard regions (their total area is more than 6 million km2), vertical layers of water, light and dark time of the day, four seasons of the year and multiyear periods, in which there were considerable changes in the biota of the region caused by global climate and oceanographic factors. This information has recently been verified, corrected, translated into English, transformed from text to digital format, and supplemented by GIS with maps of the standard regions by which data were aggregated using morphometric parameters (volume of water in cubic kilometers in the region, in its epipelagic 0-200 m, and upper epipelagic 0-50 m water layers, occupied area in square kilometers, longitude and latitude of their centroids in decimal degrees) to increase their availability to the scientific community worldwide. The data enable the evaluation of the total plankton stock of the Russian Far Eastern seas in the North Pacific (in trillions of specimens and thousands of tons), recalculate the volumetric characteristics of density into areal characteristics (in billions of specimens per square kilometer or tons per square kilometer), and, using previously published tables on calorific value and chemical composition of zooplankton, obtain their energy characteristics. Such data are crucial for the proper management of marine resources, aquaculture development, nature conservation, and the assessment of the anthropogenic impact on nature. The presented metadata provide a detailed description of how this unique dataset was created, sources and volume of gathered information, its benefits and drawbacks, some results on the quantitative inventory of marine biological resources and assessment of waters in the North Pacific, and future prospects for the use of this type of dataset in applied and fundamental research. There are no copyright restrictions on the data; please cite this data paper when the data are used in publications. [ABSTRACT FROM AUTHOR]

Corrosion is an unavoidable problem for RC structures in harsh marine environment, which encourages the application of high-performance concrete (HPC) and corrosion-resistant reinforcements, such as stainless steel (SS), stainless-clad bimetallic steel (SB) and FRP. Especially, for the RC structures in remote islands or reefs, the use of local materials (coral, sea water, etc.) may bring cost benefits by avoiding the high expansive fee. In this paper, the cost effectiveness of five different material proposals is evaluated and compared based on the life-cycle-cost analysis (LCCA), incorporating not only initial cost but also long-term investment into account. The LCCA results of a 3-floor office building in the South China Sea shows that basically the SB + HPC proposal shows the highest cost benefits considering a 100-year period while the proposals using coral aggregate seawater concrete (CASC) are not that competitive. The sensitivity analysis is performed to address the influence of discount rate and construction-to-material cost ratio. [ABSTRACT FROM AUTHOR]

The South Scotia Ridge, in the Atlantic sector of the Southern Ocean, is a key region for water mass modification. It is the location of the Weddell‐Scotia Confluence, an area of reduced stratification which separates the Weddell Gyre to the south and the Antarctic Circumpolar Current to the north, and which receives input of shelf waters from the tip of the Antarctic Peninsula. To elucidate the transformations over the ridge, we focus on one of its largest seamounts, Discovery Bank, which has previously been observed as hosting a stratified Taylor column that retains water for months to years, during which time water masses are entrained from north and south of the Weddell Front and steadily mixed. Data from ship‐deployed sensors and autonomous platforms are analyzed to quantify and understand the diapycnal mixing, heat fluxes and water mass transformations over the bank. Ocean glider and free‐profiling drifting float data show that the mid‐depth temperature maximum of the Circumpolar Deep Water (CDW) is eroded between the northern and southern sides of the bank, while diapycnal diffusivity is enhanced by up to an order‐of‐magnitude over its steeply sloping portions. This is accompanied by heat fluxes from the CDW layer being increased by up to a factor of six, which may contribute to a reduction in mid‐depth stratification. Tidal model analysis shows that the southern side of the bank hosts strong barotropic to baroclinic energy conversion (>150 N m−2), emphasizing the role of internal tides in modulating water mass transformations in the Confluence. Plain Language Summary: The Weddell‐Scotia Confluence region, in the South Atlantic sector of the Southern Ocean, is a zone where ocean waters from the Antarctic Circumpolar Current to the north, the Weddell Sea to the south, and the Antarctic Peninsula to the west, come together and interact. In this paper, observations from a research ship, an autonomous underwater glider, and free‐drifting ocean floats are used to characterize the mixing between these different sources of water, and to understand what impact this mixing has on the downstream vertical structure of the water column. The results show that an anticlockwise circulation of waters occurs around a large underwater seamount in the region, causing the waters there to be trapped for months to years. In addition, interaction with the steeply sloping undersea topography generates particularly strong mixing between these different waters through the action of tides, which helps to sustain the characteristic low vertical density gradients present in the region. These processes have important implications for both the movement of mid‐depth waters south into the circulation of the Weddell Sea, and likely also for the supply of nutrients to the productive surface layer of the ocean. Key Points: New observations reveal enhanced mixing rates and mid‐depth heat fluxes over one of the largest seamounts of the South Scotia RidgeThis enhanced mixing may help to sustain the mid‐depth stratification minimum found in the Weddell Scotia ConfluenceResults from a tidal model show high rates of barotropic to baroclinic tidal energy conversion over steeply sloping parts of the bank [ABSTRACT FROM AUTHOR]

Marine ecosystem is increasingly deteriorating. In order to assess anthropogenic influence and instigate appropriate remedial actions, it is still of great significance to develop the technology of sensors applied for nutrient detection (e.g., nitrate, phosphate, and silicate) in seawater. This brief review shows an important direction for the development of nutrient detection sensors in seawater and also the limitations and challenges based on data from the ISI Web of Science database. Being different from previous review papers, in this short critical review paper (1) we unified the unit of limit of detection (LOD) for making the comparison within different researches possible; (2) only the literatures focusing on the technological development of sensors in seawater were used; and (3) not only the detection methods but also the detected analytes and publication years were discussed to supply more valuable information for the development of nutrient sensors applied in seawater. In total, 109 literatures were collected with regard to technological development. The quantity of literatures has increased most during 2011-2020. For analytes, literatures related to nitrate, phosphate, ammonium, and phosphate will continue to increase with more accurate data. For detection methods, spectrophotometry, colorimetry, fluorimetry, and electrochemistry are the most widely used sensors. LODs show thousands of orders. In general, there are lower LOD to nitrite and ammonium and fluorimetry method. Now, for analytes, nitrate 1.0983 > silicate 0.5495 > phosphate 0.4823 > ammonium 0.1324 > nitrite 0.0568 . For detection methods, microfluidics 1.7617 > electrochemistry 1.2607 > colorimetry 0.4462 > spectrophotometry 0.2941 > fluorimetry 0.0558 . This result indicated that the development level of detection methods is closer for nitrate, nitrite, phosphate, and silicate. For ammonium, spectrophotometry has significantly lower LOD than electrochemistry (p < 0.05), and fluorimetry also has significantly lower LOD than electrochemistry (p < 0.05). Our results imply that sensors with accurate LOD should be developed in the future. In addition, more detection methods should be considered by future sensors. [ABSTRACT FROM AUTHOR]

This paper presents an analytical study on the lateral kinematic response of offshore pipe piles subjected to vertically propagating S‐wave seismic excitation. Both the kinematic interaction of the pipe pile with the soil and seawater are considered. The lateral resistances of the outer and inner soil are obtained based on the confined viscoelastic dynamic continuum models, while the hydrodynamic pressures of the seawater are based on the inviscid incompressible fluid theory. The pile response is then obtained by utilizing the continuity condition at the soil‐pile and seawater‐pile interfaces along the pile shaft. The derived solution is employed to investigate the sensitivity of the seismic response of pipe piles to certain key problem parameters, such as length of pile segment embedded in seawater, the relative stiffness of the pile and soil and the pile radius ratio. We demonstrate that the partially embedded piles are much more flexible compared with fully embedded piles when subjected to S‐wave excitation, resulting more strong motion transferred to the superstructures and the existence of seawater will amplify the seismic responses of offshore pipe piles. [ABSTRACT FROM AUTHOR]

Globally, ocean‐based economic development (aka the 'the blue economy') is increasing and continued growth is projected. The social and environmental impacts of the growth of the blue economy are a matter of some concern for local people who may experience few benefits and substantial negative impacts. One way that these impacts of the blue economy occur is through subtle or overt forms of dispossession that result from the growth of technologies and infrastructures at sea or on the land (e.g., offshore oil rigs, ships, ports, processing facilities, etc.). We focus on desalination, an understudied aspect of the blue economy that is growing exponentially. Proponents herald desalination as a sustainable solution to increase fresh water sources, while solving socio‐environmental issues left behind by the overuse of natural freshwater. However, far from being a social and environmental panacea, new political and economic interests are fused to sustain this technology with impacts for both the environment and local social systems. In this paper, we review the literature and develop a framework to understand mechanisms of dispossession via the blue economy and apply it to desalination projects in the Antofagasta Region of Chile. Drawing from a review of environmental impact assessments and declarations of environmental impacts, the research analyses communities' concerns about the impacts of desalination. Our analysis revealed (1) lack of meaningful inclusion in decision‐making; (2) physical displacement of communities or from areas required for livelihoods; (3) concerns about environmental effects, and related social impacts; and (4) few social or economic benefits to local people. The research concludes that desalination is a sector of the blue economy that is opening a new sphere of dispossession in the oceans. [ABSTRACT FROM AUTHOR]

This paper sets out the science behind global environmental change, defined by the US Global Change Research Act as 'changes in the global environment (including alterations in climate, land productivity, oceans or other water resources, atmospheric chemistry, and ecological systems) that may alter the capacity of the Earth to sustain life'. We explain why there is still scepticism about the science in the business world and introduce eight gestalt shifts that are likely to change how executives think about environmental change and the threats and opportunities such changes present. The paper concludes with future research directions on business and global environmental change and outlines how the business case for investment in clean technology means that the transition to clean tech is inevitable. [ABSTRACT FROM AUTHOR]

RETRACTION: D. Qi, Y. Wu, L. Chen, W.‐J. Cai, Z. Ouyang, Y. Zhang, L. G. Anderson, R. A. Feely, Y. Zhuang, H. Lin, R. Lei, H. Bi. (2022). Rapid Acidification of the Arctic Chukchi Sea Waters Driven by Anthropogenic Forcing and Biological Carbon Recycling. Geophysical Research Letters, 49, e2021GL097246. https://doi.org/10.1029/2021GL097246. The above article, published online on 21 February 2022 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor‐in‐Chief, Harihar Rajaram; American Geophysical Union; and John Wiley & Sons LLC. The retraction has been agreed as it was discovered that the 2019 pCO2 data collected on the 10th Chinese National Arctic Research Expedition and analyzed along with other data in this paper was used without proper permission. AGU Publications and Wiley evaluated all information submitted by the authors and scientific agencies and carefully considered Committee on Publication Ethics (COPE) guidelines before making this decision. The authors have revised their statistical analyses by excluding the 2019 Chinese National Arctic Research Expedition data and have stated they intend to submit the revised manuscript to the journal. D. Qi acknowledges that the data ownership is disputed, and therefore accepts the retraction. L. Chen and W.‐J. Cai disagree with the retraction. Z. Ouyang, Y. Zhang, L. G. Anderson, R. A. Feely, Y. Zhuang, H. Lin, R. Lei, and H. Bi did not respond to our notice of retraction. [ABSTRACT FROM AUTHOR]

In this paper, the tribological behaviors of B4C–SiC composites self‐mated pairs in seawater and pure water were investigated, respectively. The results showed that the B4C–SiC composite with the content of 20%SiC has good mechanical properties. For the B4C–20%SiC self‐mated pair in seawater, the abrasive wear is greatly weakened, and the tribo‐chemical reactions between the composite surface and water molecules occurred. The tribo‐chemical polishing causes very smooth wear surfaces, and the sliding pairs enter to the status of liquid lubrication. An extremely low friction coefficient (0.038) and wear rate (both below the order of magnitude 10−5 mm3/N m) were obtained in this study. Due to the lower viscosity of pure water, the load carrying capacity of the liquid film reduces. So, in pure water, the sliding pair shows slightly higher friction coefficient and wear rate than that in seawater. [ABSTRACT FROM AUTHOR]

In order to promote the discovery of new shale gas exploration areas in Guangxi, based on the latest drilling data, through detailed observation and description of logging data and cores, this paper selects high-quality shale samples of the target layer for X-ray diffraction analysis and testing of clay minerals and whole rock, major and trace elements (including rare-earth elements), TOC, and other related analysis and testing. The study shows that the total amount of rare-earth elements in the first member of Lower Carboniferous Luzhai Formation in Rongshui area, Guangxi, is low; δ EU and δ CE show negative abnormality. The average value of w V / V + Ni , Th / U ratio, and Mo-TOC covariant model diagram of the first member of Luzhai Formation show that it was the condition of anoxic reduction at that time. At the same time, Ba-Sr diagram, Sr/Cu ratio, and total rare-earth elements reflect that the area was in an arid, hot, and marine salt water paleoenvironment during the sedimentary period. Most of the sample parent rocks of the first member of Luzhai Formation are in shale area, and some samples are close to felsic igneous rock area, which is of mixed origin. The tectonic background of the source area is mainly continental island arc and active continental margin, indicating that the sedimentary environment was unstable and highly active under the background of extensional rifting at that time. [ABSTRACT FROM AUTHOR]

Most mechanical structures are composed of several components of different shape, size and material. In order to guarantee the connections among such parts is often necessary to adopt different connection mechanisms. The joints represent the structure possible weak points, can be easily site of damage and rupture so their careful design plays a decisive role. In recent years, the use of polymeric composite materials has become widespread, both in the automotive, aerospace and nautical fields. They allow advantages not only in terms of durability in aggressive environments, such as sea water or chemical industry, but also in terms of effective strength‐weight ratio. In particular, the latter translates into fuel savings and a consequent reduction in costs and pollution. It is stated a weight reduction of just 1 kg, on a mid‐range routing aircraft, can save up to 3000 L of fuel per year. The scientific community is making great efforts to develop high‐performance and reliable connections. Among the types of composite joint, the one of interest for this study is called hybrid, as it combines two connection mechanisms: bolting and bonding. Numerous studies and experimental researches, conducted on both the two separate variants and their hybrid version, the comparison of the analyses shows the hybrid one offers better results in terms of strength and fatigue life. In this paper, virtual models are built to simulate traction tests; the results are compared to experimental ones in order to validate the numerical model. In particular, the study focuses on the pretensioning influence on the joint structural behavior. [ABSTRACT FROM AUTHOR]

Internal waves (IW) are crucial contributors to the transport of sediment, heat, and nutrients in coastal areas. While IW have been extensively studied using point measurements, their spatial variability is less well understood. In this paper we present a unique set of high‐resolution infrared imagery collected from a helicopter, hovering over very energetic shoaling and breaking IW. We compute surface velocities by tracking the evolution of thermal structures at the ocean surface and find horizontal velocity gradients with magnitudes that are more than 100 times the Coriolis frequency. Under the assumption of no vertical shear we determine vertical velocities from the obtained horizontal divergence estimates and identify areas of the wave undergoing breaking. The spatial variability of the internal wave occurs on scales from a few to a few hundred meters. These results highlight the need to collect spatio‐temporal observations of the evolution of IW in coastal areas. Plain Language Summary: Oceanic internal waves (IW) form between heavier and lighter ocean water in the ocean interior, covering a wide range of temporal and spatial scales. They are amongst some of the key processes in the ocean—they facilitate transport of heat, sediment, and nutrients which have important implications for plankton and other ocean lifeforms, and serve as a pathway of energy from large to small scale flows. Yet, they are often measured using a point based approach (e.g., a buoy), which is unable to provide a full picture of the spatial variability of these waves and hence might not capture crucial behavior. Here, a unique set of high resolution airborne measurements is presented, covering several kilometers of a shoaling (and breaking) internal wave packet. Velocities at the sea surface are determined from infrared video imagery, using the temperature of the water as a tracer. By applying simple models to the velocity data (no change of horizontal velocity with depth), we show that variations in the vertical transport and in breaking characteristics are significant on many different spatial scales. This work is a step forward in understanding and quantifying the spatial variability of IW and processes associated with their breaking induced flow. Key Points: We present novel high‐resolution airborne observations of the kinematics of shoaling and breaking internal wavesWe find that the active breaking regions of the internal wave drive strong convergence/divergenceThe spatial variability of the internal wave is shown to occur over a broad range of scales, from a few to a few hundred meters [ABSTRACT FROM AUTHOR]

An experimental campaign was carried out on full‐scale naturally corroded prestressed concrete (PC) beams without transverse reinforcement to investigate the corrosion effects on failure modes, shear capacity, and ductility. The analyzed PC beams, structural members of a thermal power plant, were subjected for 10 years to refrigerating wetting cycles with marine water. In this paper, the experimental results of four‐point bending tests, carried out at the Institute "Eduardo Torroja" in Madrid, are described. Before tests, a visual inspection was conducted to detect the damages induced by corrosion. During the tests, displacements and strains were measured by using linear variable displacement transducer (LVDT) and digital image correlation (DIC). After the tests, strands were removed from beams and cut in pieces, which were weighed to measure the mass loss. Last, it was proved that the residual life of PC beams, exposed to chloride attack, is strongly affected by corrosion, whose effects reduce the shear capacity in terms of both resistance and ductility. [ABSTRACT FROM AUTHOR]

Coastal dry tropical forests (CDTFs) are important yet vulnerable ecosystems. In this paper, we highlight the special conservation issues facing CDTFs by focusing on one variant of the type, those that occupy limestone substrate in the northeastern Caribbean. Our analysis draws largely from the coastal terrestrial broadleaf forests of the northern Bahamas, the Florida Keys, and southwestern Puerto Rico. Based on the surveys of storm surge recorded during major hurricanes during the last 50 years, we define CDTFs as coastal terrestrial broadleaf forests on ground surfaces elevated up to 5 m above sea level and occurring within 5 km of the coast. These forests are not only threatened by land‐use change from urbanization but also climate‐driven sea level rise (SLR) and hurricanes, which have degraded them and reduced their extent. CDTFs are distinguished from other dry tropical forests by the occasional influence of marine water incursion during periodic storms, requiring species common to these forests to have some level of salt tolerance despite experiencing well‐drained, fresh water conditions during most of their life span. With precipitation being the sole freshwater source for most CDTFs, SLR and the resulting salinization in the rooting zone subjects these forests to increasingly stressful conditions. Hence, even a modest rise in sea level can push numerous imperiled and endangered species and coastal terrestrial broadleaf communities to the edge of their tolerance, causing a decline in extent or their complete disappearance. Outside of protected areas, rapid urbanization has fragmented these forests and reduced their extent, which in turn have modified the interaction between rising seas and forest function. This work emphasizes the need for refined risk assessments to be completed and for conservation measures to be enforced so that resources can be directed appropriately to prevent further loss of CDTFs. Abstract in Spanish is available with online material. [ABSTRACT FROM AUTHOR]

As the quintessential representation of MXenes, Ti3C2Tx has attracted widespread scientific interest and has demonstrated unparalleled potential in various applications. However, Ti3C2Tx has always been subject to its ambient instability, which deteriorates the intrinsic properties and limits the practical applications. The mechanism responsible for oxidative degradation of Ti3C2Tx has remained elusive, and the subsequent improvement of the preparation for ambient‐stable Ti3C2Tx is still a challenge. In this paper, the ambient instability of Ti3C2Tx is found to be attributed to the presence of many oxidation active sites on the surface, the formation of which is highly correlated with the enrichment of etching by‐products (AlFx or Al(OF)x). Based on the above findings a slow‐speed etching method is designed, using tetramethylammonium hydroxide as a separate etching‐agent, to avoid adsorption of fluorine‐containing by‐products during etching. The prepared high‐quality Ti3C2Tx flakes exhibit excellent ambient stability even after 4 months of dispersion in water, unlike conventional aqueous Ti3C2Tx dispersions that can only be kept for a few days. The intrinsic stability allows Ti3C2Tx to avoid its decomposition in seawater desalination, and it exhibits superior desalination ability with a maximum reduction of 62.2% in Na+ permeability and a maximum increase of 300% in water flux. [ABSTRACT FROM AUTHOR]

The recovery of crude oil and volatile organic compounds (VOCs) spilt in the environment is an intractable problem for environmental scientists. In this paper, a new lipophilic polyelectrolyte gel as an absorbent for various volatile chemical compounds is demonstrated. It is prepared by radical copolymerization of an acrylate monomer with an ionic group, tetraalkylammonium tetraarylborate, octadecyl acrylate, and a crosslinker, dipropylene glycol diacrylate, in the presence of a radial initiator. Investigation of the swelling behavior for the mixtures of water or aqueous salts reveals that the gel shows similar swelling behavior to those for pure organic solvents. On the other hand, the swelling degree in THF‐water mixture is lower than that of pure THF, because THF and water are miscible to each other, and the presence of a small amount of water in THF reduces the compatibility of the gel and THF. The salting‐out effect can separate the THF‐water mixture to form a biphasic system and recover the high swelling ability of the gel. The swelling behavior in the mixture of water‐organic solvents systems provides a new insight for designing VOC and oil absorbents in various environmental conditions, especially in hydrosphere such as seas and lakes. [ABSTRACT FROM AUTHOR]

The discharge characteristics of seawater batteries can be used to prolong the working hours of autonomous underwater observation vehicles. However, the output voltage level of the seawater battery is low, so it cannot directly be used to power supply underwater observation vehicles. In this paper, a boost converter is proposed based on the seawater batteries to power supply autonomous underwater observation vehicles. The proposed converter greatly increases the voltage level of the seawater battery and directly supplies the underwater observation vehicles. Compared with the traditional boost converter, the voltage gain of the proposed converter is more than ten times higher than it under the same duty ratio condition. Its structure is asymmetric interleaved parallel, which can enable power devices to obtain lower voltage stress and ensure that the input current ripple is low. The operating principle and homeostasis property of the proposed converter are analyzed in detail. Finally, a prototype is built. Through simulation and experiment, the correctness of the theoretical design is verified and experimental results are analyzed. [ABSTRACT FROM AUTHOR]

During aerobic oxidation of methane (CH4) in seawater, a process which mitigates atmospheric emissions, the 12C‐isotopologue reacts with a slightly greater rate constant than the 13C‐isotopologue, leaving the residual CH4 isotopically fractionated. Prior studies have attempted to exploit this systematic isotopic fractionation from methane oxidation to quantify the extent that a CH4 pool has been oxidized in seawater. However, cultivation‐based studies have suggested that isotopic fractionation fundamentally changes as a microbial population blooms in response to an influx of reactive substrates. Using a systematic mesocosm incubation study with recently collected seawater, here we investigate the fundamental isotopic kinetics of aerobic CH4 oxidation during a microbial bloom. As detailed in a companion paper, seawater samples were collected from seep fields in Hudson Canyon, U.S. Atlantic Margin, and atop Woolsey Mound (also known as Sleeping Dragon) which is part of lease block MC118 in the northern Gulf of Mexico, and used in these investigations. The results from both Hudson Canyon and MC118 show that in these natural environments isotopic fraction for CH4 oxidation follows a first‐order kinetic process. The results also show that the isotopic fractionation factor remains constant during this methanotrophic bloom once rapid CH4 oxidation begins and that the magnitude of the fractionation factor appears correlated with the first‐order reaction rate constant. These findings greatly simplify the use of natural stable isotope changes in CH4 to assess the extent that CH4 is oxidized in seawater following seafloor release. Plain Language Summary: The aerobic oxidation of methane in seawater is a process that prevents methane produced in the oceanic environment from being emitted to the atmosphere. During this process, isotopic forms of methane are oxidized at slightly different rates leading to changes in the natural methane isotope ratios with the extent of oxidation. While these changes in isotope ratios would seem to be a proxy for the extent of methane oxidation, laboratory‐based studies involving pure cultures have shown that these isotope ratio changes vary as a microbial population blooms in response to an increase in substrates. This study systematically measured the stable isotope changes that are associated with aerobic methane oxidation in recently collected seawater collected from regions of active seafloor methane release along the U.S. Atlantic margin and the Gulf of Mexico. Results show that these isotope changes are systematic during methane oxidation, greatly simplifying the use of isotope changes to determine the extent of methane oxidation. Key Points: Systematic seawater incubations were conducted to determine stable isotopic changes associated with aerobic methane oxidationIsotopic fractionation caused by aerobic methane oxidation was shown to follow first‐order isotopic kineticsDespite displaying a microbial bloom associated with rapid oxidation events, the isotopic fractionation factor remained constant [ABSTRACT FROM AUTHOR]

This paper investigates the link between the Labrador Sea Water (LSW) formation rate and the strength of the Atlantic Meridional Overturning Circulation within the Labrador Sea. LSW is formed in the Labrador Sea through deep wintertime ocean convection and is then carried out of the basin by, among other currents, the Deep Western Boundary Current (DWBC) that flows southward along the east coast of Canada. We used an eddy‐permitting simulation (at 1/12°, horizontal resolution) with an Arctic and Northern Hemisphere Atlantic configuration of the Nucleus for European Modeling of the Ocean (NEMO) model that covers the period from 2002 to 2017. In this study, the formation rate of LSW is estimated using an instantaneous kinematic subduction approach by analyzing the vertical transport of a water mass through the base of the mixed layer. We computed the local Meridional Overturning Circulation (MOC) index and the transport of LSW within the DWBC at the Atlantic Repeat hydrographic section 7 West (AR7W). Results show that an increase in the formation rate of LSW entails an increase in the LSW transport in the DWBC within 1 year. This is followed by an enhancement of the overturning in the Labrador Sea. Plain Language Summary: The Atlantic Meridional Overturning Circulation (AMOC) is of paramount importance for the climate. The AMOC contributes to the redistribution of heat, salt, and anthropogenic carbon in the world's oceans. The upper limb of the AMOC transports warm, surface water northward. The lower limb of the AMOC is associated with dense, cold, and deep water formation and is carried by a vigorous Deep Western Boundary Current (DWBC). The Labrador Sea Water (LSW) is one of the water masses formed by deep convection in the subpolar gyre and then carried out of the basin by, among other currents, the DWBC that flows southward along the east coast of Canada. In this paper, we use a simulation to investigate how the change in the formation rate of the LSW could impact the strength of the local AMOC in the Labrador Sea. We found that an increase in the formation rate of LSW entails an increase in the LSW transport in the DWBC within 1 year. This is followed by an enhancement of the overturning in the Labrador Sea. Key Points: Strong convection events in the Labrador Sea entail a high formation rate of Labrador Sea WaterPart of the Labrador Sea Water is exported out of its formation region through the Deep Western Boundary Current within 1 yearStrong, deep convection events are related to a higher local MOC index in the Labrador Sea along the AR7W section [ABSTRACT FROM AUTHOR]

This paper reports leach and/or intake of SO42−, Cl−, Ca2+, Na+, and K+ from and/or into cement mortar cubes made from a novel cementious material in naturally encountered environmental simulated media. The paper also reports changes in pH of the media over time of exposure to the cement mortar cubes. The compressive strength changes of the test cement in simulated media are also reported. The novel cement, labelled PCDC, made from intermixing ordinary Portland cement (OPC) with waste materials which included rice husks, waste bricks, acetylene lime sludge, and spent bleaching earth was previously tested and found to meet the Kenyan Standard requirements for Portland pozzolana cement (PPC). 100 mm mortar cubes were prepared, and their compressive strengths were determined after exposure to the sea water. The media included sea water, distilled water, and solutions of sulphates and chlorides separately for a period of six months. The tests were carried alongside commercial PPC and OPC. The results showed that the PCDC exhibited comparable selected ions intake and/or leach to PPC in sea water, sulphate solutions, and distilled water. In chloride solutions, the cement exhibited the highest leach in the selected ions except K+ and Na+ ions. The results further showed that PCDC exhibited lower pH in all the media compared to OPC and PPC. The tests showed that the novel cement can be used for general construction work in the tested media in a similar manner to PPC. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of coral sand powder (CSP) and corrosion inhibitors (SBT®‐ZX(V), SBT®‐RMA(II)) on reinforcement corrosion in coral aggregate seawater concrete (CASC) in a marine environment. A reasonable time‐variation model for reinforcement corrosion in CASC is proposed and verified. Based on the time‐variation model and chloride diffusion model, the cracking time and service life of CASC are predicted. The results show that the replacement of cementitious materials by 5% CSP can improve the corrosion resistance of steel bar in CASC. Both SBT®‐ZX(V) and SBT®‐RMA(II) can reduce the corrosion rate of steel bar in CASC, and this effect of SBT®‐RMA(II) is more effective than that of SBT®‐ZX(V). Among all CASC, CASC containing 5% CSP and SBT®‐RMA(II) possesses the best corrosion resistance. The results also reveal that the corrosion current density of steel bar in CASC increases firstly and then decreases over time. The ascending segment of the fitting curves for reinforcement corrosion in CASC conforms to the logarithmic‐type time‐variation model, and the descending segment of the fitting curves for reinforcement corrosion in CASC conforms to the exponential‐type time‐variation model. The cracking time and service life of CASC containing 5% CSP and SBT®‐RMA(II) will reach more than 10 years when the thickness of protective layer is 30 mm. [ABSTRACT FROM AUTHOR]

Using the depth (z) and density (ϱ) frameworks, we analyze local contributions to AMOC variability in a 900‐year simulation with the AWI climate model. Both frameworks reveal a consistent interdecadal variability; however, the correlation between their maxima deteriorates on year‐to‐year scales. We demonstrate the utility of analyzing the spatial patterns of sinking and diapycnal transformations through depth levels and isopycnals. The success of this analysis relies on the spatial binning of these maps which is especially crucial for the maps of vertical velocities which appear to be too noisy in the main regions of upwelling and downwelling because of stepwise bottom topography. Furthermore, we show that the AMOC responds to fast (annual or faster) fluctuations in atmospheric forcing associated with the NAO. This response is more obvious in the ϱ than in the z framework. In contrast, the link between AMOC and deep water production south of Greenland is found for slower fluctuations and is consistent between the frameworks. Plain Language Summary: The variability and trends in Atlantic meridional overturning circulation (AMOC) are some of the most important characteristics of an ocean model simulation that are relevant for climate. Usually, the AMOC is computed as a meridional transport (from bottom to top) of zonally integrated flow along constant depth levels (z‐AMOC). However, water in the ocean generally flows along the density surfaces. In low latitudes, they are nearly flat and the general picture given by z‐AMOC is highly relevant. In high latitudes, where the most important processes of dense water formation and sinking take place, density surfaces are sloping, and the z‐AMOC gives a distorted image of the real circulation. This is why recent studies underlined the importance of computing the AMOC as a function of density in addition to AMOC as the function of vertical coordinate. In this paper, we analyze the fundamental differences with respect to AMOC variability in both frameworks in a 900‐year run with the AWI climate model. We demonstrate that the latitudinal position of overturning maxima, amplitude, and variability show substantial differences between the frameworks. We suggest that the ϱ‐AMOC and watermass transformation framework should be used routinely in standard analyses, including forthcoming intercomparison projects. Key Points: Patterns of sinking and diapycnal transformation across depth levels and isopycnals, respectively, can be used to study AMOC variabilityThe AMOC subpolar maximum is largely driven by internal transformationsThe density framework illustrates the interplay between surface buoyancy flux and interior‐mixing [ABSTRACT FROM AUTHOR]

The seahorse relies on the undulatory motion of the dorsal fin to generate thrust, which makes it possess quite high maneuverability and efficiency, and due to its low volume of the dorsal fin, it is conducive to the study of miniaturization of the driving mechanism. This paper carried out a study on the undulatory motion mechanism of the seahorse's dorsal fin and proposed a dynamic model of the interaction between the seahorse's dorsal fin and seawater based on the hydrodynamic properties of seawater and the theory of fluid-structure coupling. A simulation model was established using the Fluent software, and the 3D fluid dynamic mesh was used to study the undulatory motion mechanism of the seahorse's dorsal fin. The effect of the swing frequency, amplitude, and wavelength of the seahorse's dorsal fin on its propulsion performance was studied. On this basis, an optimized design method was used to design a bionic seahorse's dorsal fin undulatory motion mechanism. The paper has important guiding significance for the research and miniaturization of new underwater vehicles. [ABSTRACT FROM AUTHOR]

This paper focuses on the durability of basalt fiber reinforced polymer (BFRP) laminas exposed to solutions of normal concrete (NC) and seawater sea sand concrete (SWSSC) by acceleration of temperature. Modification of BFRP laminas using different contents of silica nanoparticles and multiwall carbon nanotubes (MWCNTs) was conducted, and the effect of modification on the durability of the lamina was evaluated. The degradation and modification mechanism of BFRP laminas was investigated by scanning electron microscopy (SEM). The results showed that the BFRP laminas exhibited obvious strength degradation after exposure to the NC and SWSSC solutions, while the Young's modulus of the laminas remained nearly unchanged. The tensile strength of BFRP laminas in SWSSC solution declined faster than in NC solution due to the combined effect of alkali ions and saline ions in the SWSSC solution accelerated the corrosion of FRP. Additionally, the durability of MWCNT‐modified specimens has been significantly improved. The SEM images revealed that MWCNTs in the resin matrix improve the interface bonding performance between the fiber and the resin. Furthermore, the diffusion path of OH−, Cl−, and H2O molecules is elongated and hindered by MWCNTs. The silica nanoparticle‐modified BFRP laminas obtained improved corrosion resistance performance only at a content of 1 wt%. Additionally, the long‐term residual tensile strength of modified BFRP laminas under NC and SWSSC environments was predicted. [ABSTRACT FROM AUTHOR]

Degradation of composites properties with water absorption is a severe threat to its application in marine structures and humid environments. Real life composite structures often work under mixed mode loading. In this paper, Glass fiber composite has been investigated for the influence of sea water aging on the fracture toughness under mixed mode loading. Glass fiber/epoxy specimens were immersed for 21 and 35 days in sea water. Controlled mixed mode loading was applied using mixed mode bending fixture. Dry and moisture‐saturated specimens were tested for fracture toughness over the room temperature by varying lever length of MMB apparatus. Under mixed mode loading the strain‐energy release rate decreased with increase in moisture content. The approximate decrease in fracture toughness was observed 31% and 48.55%, respectively, for 21 and 35 days specimens as compared with dry specimen. Scanning electron microscope analysis revealed interfacial debonding to be leading failure mechanism, representing a strong effect of sea water degradation on fracture toughness results. [ABSTRACT FROM AUTHOR]

This paper presents the electrochemical performance and microstructural evolution of friction stir welded joint of dissimilar AA1050 and AZ91D in seawater, for potential applications in the transportation industry. The corrosion behavior of the dissimilar weld was compared to the corrosion behavior of the parent materials, and similar welds of each alloy. The experiments were successfully conducted with an H13 hot‐working tool steel in butt‐joint configuration. The results revealed the presence of intercalated microstructure in the dissimilar weld and homogenous microstructures in the similar welds. The corrosion resistance properties of the parent materials and similar welds were higher than that of the dissimilar weld sample. The dissimilar weld has a current density of 3.83×10−5 A/cm2 and corrosion rate of 9.99×10−4 mm/year; and is most susceptible to corrosion, due to the galvanic coupling between the dissimilar alloys and intermetallic compounds. The similar weld of AA1050 has a current density of 1.99×10−7 A/cm2 and corrosion rate of 1.44×10−3 mm/year, while the similar weld of AZ91D has a current density of 8.58×10−6 A/cm2 and corrosion rate of 1.13×10−1 mm/year. [ABSTRACT FROM AUTHOR]

Environmental prediction is one of the crucial means for social sustainable development. Based on the continuous sampling of atmospheric precipitation in Guanling County, Guizhou Province, China, from March 2016 to February 2017, and combining the reanalyzed data of the National Centre for Environmental Prediction/National Centre for Atmospheric Research with the Hybrid Single-Particle Lagrangian Integrated Trajectory model, this paper analyzed the variations of δ2H and δ18O in precipitation at the synoptic scale in the Guanling region. The results showed that the variations of δ2H, δ18O, and d-excess values in precipitation exhibited remarkable seasonal variability. The stable isotopic values in precipitation in the winter half-year were higher than those in the summer half-year. The meteoric water line of the winter half-year was close to the annual meteoric water line. The results showed that there was more than one fundamental source of moisture. It was affected by the winter monsoon period, which is longer than the summer monsoon period, so the local evaporation of water vapor participating in the water circulation had a greater impact. With the increase of precipitation, the intercept and slope of the meteoric water line gradually decreased, which indicated that the secondary evaporation was weak under the effect of stable isotope subcloud cluster. The correlations of precipitation δ18O with temperature T and precipitation P vary with time scales. As the time scale decreased, the correlation between δ18O and the temperature and precipitation improved. When P ≤ 5 mm and 10°C < T ≤ 30°C, the most sensitive changes in stable isotopes were observed. In the study area, the backward trajectory model showed that the moisture in the winter half of the year was mainly from the transportation of the westerlies wind, replenishment, and local reevaporation of near-source ocean water, while the water in the summer half of the year mainly came from the transportation of water from the ocean at low latitudes. [ABSTRACT FROM AUTHOR]

A better understanding of the relationships between oceanic environments and fishing conditions could make the utilization of fish more efficient, profitable, and sustainable. The current lack of high‐precision subsurface seawater information has long been a constraint on fishery research. Using near‐real‐time Argo observations, this paper presents a new approach called gradient‐dependent optimal interpolation. This approach provides daily subsurface oceanic environmental information according to fishery dates and locations. An experiment was conducted in the western and central Pacific Ocean using yellowfin tuna (YFT) catch data in August 2017. The results of seawater temperature and salinity represented differences of less than ±0.5°C and ±0.05, respectively, according to verification of error analysis and truth‐finding comparisons. After applying the constructed temperature and salinity profiles, we described the relationship between subsurface information and yellowfin tuna catch distribution. Statistical analysis revealed that yellowfin tuna were more adapted to warmer and saltier seawater. At the near‐surface (<5 m), the most suitable temperature was 28–29°C, although yellowfin tuna can endure a temperature range from 11 to 12°C at a depth of 300 m. The corresponding upper boundary of the thermocline was approximately 75 m, with a mean strength of 0.074°C/m, and the most suitable salinity for yellowfin tuna was 34.5–36.0 at depths shallower than 300 m. These results indicated that the constructed subsurface information was very close to the true values and they had high spatial and temporal accuracy. [ABSTRACT FROM AUTHOR]

Two kinds of cathodic shielding phenomena of the sacrificial anode cathodic protection systems, which are caused by a metal barrier, were investigated by numerical simulations and experiments in this paper. The results show that if the cathode current is completely shielded by the barrier, one side of the barrier would act as the anode leading to the occurrence of serious corrosion, while the protected components and the other side of the barrier would act as cathode being protected. However, if the cathode current is only partially shielded, both the metal components and the barrier would act as cathodes. Furthermore, this non-full shielding effect of the barrier would be weakening by decreasing the mass transfer resistance between the sacrificial anode and the cathodically protected component. [ABSTRACT FROM AUTHOR]

Seawater sea sand concrete (SWSSC) is a promising alternative to ordinary concrete in terms of saving valuable natural resources of freshwater and river sand. Basalt fiber reinforced polymer (BFRP) rebars can be a good solution to corrosion of steel rebars in SWSSC. This paper presents an experimental study on the bond behavior between SWSSC and BFRP rebars through pullout testing. Concrete mixed with freshwater and river sand was also prepared for comparison with SWSSC. BFRP rebars with two different surface configurations were selected, that is, ribbed surface and sand-coated surface. Fly ash as a replacement of cement was also investigated in terms of its effect on bond behavior. Failure modes, bond-slip relationships, and bond strengths were reported and discussed in terms of the previously mentioned parameters. It was found that ribbed surface of BFRP rebar could achieve better mechanical interlocking with surrounding concrete. SWSSC could have comparative bond strength with BFRP rebar compared with ordinary concrete. However, using fly ash to replace cement is not recommended because it would significantly reduce concrete strength leading to much lower bond at the interface between SWSSC and BFRP rebar. [ABSTRACT FROM AUTHOR]

In recent years, many researchers have been focusing on improving the discharge properties of AZ31 magnesium alloy for battery applications. In this paper, the equal‐channel angular pressing (ECAP) is used as a preferred way of refining the microstructure to enhance the discharge characteristics of AZ31 alloy as the anode for seawater batteries. The electrochemical discharge behaviors of ECAP‐processed AZ31 alloy are investigated along extrusion surfaces, normal cross‐sections, and transverse cross‐sections and compared with as‐cast and homogenized samples. On the basis of the findings, the anode efficiency is improved effectively through the ECAP method, with approximate isotropy in the discharge behaviors of refined AZ31 alloy. The enhanced discharge performance can be attributed to the refined grains, uniform grain sizes, and dispersed β‐Mg17Al12 after ECAP processing. [ABSTRACT FROM AUTHOR]

Tidal asymmetry plays a key role in the behavior of estuaries. Positive and negative asymmetries are associated with flood‐ and ebb‐dominated estuaries, respectively. Asymmetry arises from both the interaction among the main tidal constituents and the harmonics generated when tide propagates in shallow waters. Most previous research focuses on the deformation of the tide within estuaries; however, ocean tide may show asymmetry at the estuary entrance, which implies that the boundary condition is already deformed. This fact has important implications for tide propagation, estuarine transport processes, and flow exchanges between estuaries and open oceans. In this study, the global astronomical tide is classified according to its asymmetry and periodicity. The objective is to provide a guiding framework of representative astronomical tide types (ATtypes) on a worldwide scale to be used as a reference for further research on the transport of substances in estuaries. The applied methodology is based on the use of the TPXO9‐atlas global barotropic tidal solution and detailed statistical analysis. Probability density functions of the tidal elevation time derivative and the tidal form factor were extracted from TPXO9‐atlas with a spatial resolution ranging from 1/6° to 1/30°. The K‐means algorithm was applied to these parameters, and 25 representative ATtypes were identified. The classification was validated with 757 worldwide tide gauge records. The results show that 11.3% of coastal areas show negative asymmetries, 11.3% positive asymmetries, while symmetric tides dominate 77.4% of coastal areas. In these areas, estuaries can show asymmetries exclusively dependent on overtides and compound tides generated during inland propagation without being externally conditioned. Plain Language Summary: The asymmetry of the tide influences the transport of substances (such as sediments and marine litter) within estuaries. Most research focuses on the deformation of the tide as it propagates through estuaries; however, the tide may show asymmetry at the entrances of estuaries, implying that the boundary condition is already deformed. This fact has important implications for tide propagation, estuarine transport processes and flow exchanges between estuaries and the open ocean. In this paper, the asymmetry of astronomical tide is characterized on a worldwide scale in the outer vicinities of estuaries to obtain a guiding framework of representative tide types. This framework can be used as a reference for further research on estuarine processes anywhere in the world. Key Points: The TPXO9‐atlas solution and K‐means algorithm are used to describe the asymmetries of the ocean tide worldwideSymmetric tides dominate a major percentage of the oceans, and asymmetric tides are found in very specific areas of the world [ABSTRACT FROM AUTHOR]

The Reversal Indian Ocean Waters (RIOWs), carried by flows in a direction opposite to the Indonesian Throughflow (ITF), is investigated in the Lagrangian framework using the simulative results of a high‐resolution western Pacific and northern Indian Oceans Model (PIOM). The results suggest that the RIOWs have two sources: They are the Australian Northwest Shelf Inflow linking with the Leeuwin UnderCurrent (LUC) along with the previously identified South Java Coastal Undercurrent (SJCU). After entering the Indonesian seas, the RIOWs mix with other water masses and tend to make waters in the Indonesian seas cooler, saltier, and denser. Ultimately, about half of the RIOWs return to the Indian Ocean by joining the ITF, and the other half enter the Pacific Ocean and contribute to the North Equatorial CounterCurrent (NECC) and the North Intermediate CounterCurrent (NICC). Plain Language Summary: The Indonesian Throughflow (ITF) is often viewed as a unidirectional strong flow from the Pacific to the Indian Ocean. Little attention has been given to the reversal flow that permits Indian Ocean waters into the Indonesian seas since it was first documented (Sprintall et al. 2009, https://doi.org/10.1029/2008JC005257). In this work, we apply the Lagrangian trajectory code TRACMASS to a western Pacific and northern Indian Ocean Model (PIOM) to investigate this neglected issue and diagnose the reversal flow on its sources, sinks, and contributions to the Indonesian seas. This paper proposes for the first time a very interesting viewpoint that a small amount of Indian Ocean waters may get into the Pacific Ocean through the Indonesian Archipelago and it ultimately feeds into two important currents of the Pacific Ocean, namely, the North Equatorial CounterCurrent (NECC) and the North Intermediate CounterCurrent (NICC). All these not only provide us a new perspective of water exchanges between the Pacific and Indian oceans but also promote our understanding of the unique water properties of the Indonesian seas. Key Points: The reversal flow in the Ombai and Timor straits, opposite in direction to the Indonesian Throughflow, is simulated and analyzedThe reversal flow carries waters from the Indian Ocean through the Indonesian seas to the Pacific OceanThe Reversal Indian Ocean Waters make the Indonesian seas cooler, saltier, and denser [ABSTRACT FROM AUTHOR]

A review of the long‐term changes and variations in benthic communities and the current status of the marine invasive species (MIS) in shallow waters of the Yellow Sea (Chinese sector) and the Sea of Japan (Russian and partly Korean sectors) is presented. This paper reflects on the progress and lessons learned, recommending actions for the future about the conservation of biodiversity.In the Bohai Sea, the benthic ecosystem has been degenerating due to anthropogenic activities such as overfishing and pollution since the 1950s. The dominant position of K‐strategy species is gradually being lost and replaced by R‐strategy species. In the Yellow Sea, the macrobenthic community is different from other areas due to the Yellow Sea Cold Water Mass. Many economic species have been destroyed, and the biotic structure has changed significantly due to overfishing and climate change.In the Russian sector of the Sea of Japan, the macrobenthic communities in the shallow‐water soft bottom have generally been in a stable condition for the last decades, except for some heavily polluted or disturbed areas due to dredging operations. The abundance of select large invertebrate species has changed considerably due to commercial fishing and poaching. Variations in macro‑ and meiobenthic communities under aquaculture conditions have occurred on a local scale during the last five decades.MIS show obvious differences between China and Russia in the following aspects: introduction pathways of MIS, composition and number of non‐native species, threats and impacts of MIS to native communities and ecosystems, and economic and public health impacts.Long‐term monitoring programmes should be developed to reveal future biotic changes and to separate the effects of cyclic variations of benthic communities from the impacts of pollution and eutrophication. Standardization of sampling procedures is required to compare changes/alternations in benthos across various regions worldwide. [ABSTRACT FROM AUTHOR]

Titanium alloy is an excellent corrosion resistance material due to its greater affinity with oxygen when exposed to an aggressive medium such as sea water. The protection against attack is due to the oxidizing fume formed into its surface. This paper reports the effect of laser power on the corrosive behavior of laser metal deposited Ti6Al4V alloy with 5 weight percent (wt. %) copper in freshly prepared artificial sea water. The open circuit potential, potentiodynamic polarization curves, and the scanning electron microscope (SEM) morphologies of the entire Ti6Al4V+5 Cu alloy samples had been investigated and reported. From the results obtained, it can be deduced that the laser power is inversely proportional to the corrosion rate. Sample PL3 deposited with a laser power of 1600 W exhibited the best corrosion rate of 0.0123 mm/year when exposed to sea water under aerated condition. The morphologies of the entire laser deposited samples of the scanning electron microscope (SEM) unveiled typical passivity due to the strong inter‐atomic bonds between the α/β phases formed with the copper inclusion within the lattices of the titanium alloy. [ABSTRACT FROM AUTHOR]

Aquaculture, which is an important part of food supply, is usually carried out in cage nets made of textile materials. Fouling organisms settle on the cage nets over time, close the mesh openings, and cause unwanted weight gain. In order to prevent fouling, aquaculture nets are generally treated with antifouling paints. In this paper, warp knitted cage nets made from various raw materials were treated with three different antifouling paints. Econea was used as a biocide to prepare an eco‐friendly antifouling paint formulation, and two copper‐based commercial antifouling paints were supplied for comparison. Antifouling paint‐treated and untreated net samples were immersed in a marine ecosystem next to an aquaculture zone for 6 months. Settlement of fouling organisms on nets was observed by taking underwater photographs at periodic intervals. Following the field study, changes in the structure of the nets and antifouling performance of the paints were evaluated considering the results of underwater photographs, biomass growth, variation in mass and strength tests. Colour fastness of the antifouling paints to sea water was also measured to learn about biocide release and surface hydrophobicity. The results show that copper‐free eco‐friendly antifouling paint is just as effective against the fouling mechanism for all types of nets as copper‐based commercial antifouling paints. The novel eco‐friendly formulation has promising results, which provides an alternative for producers when considering the selection of raw materials. [ABSTRACT FROM AUTHOR]

Methyl ethyl ketone (MEK) is a relatively abundant but understudied oxygenated volatile organic compound that can serve as a source of both HOx and PAN when photooxidized. We use aircraft observations of MEK from the remote marine troposphere to show that the ocean serves as a source of MEK to the atmosphere during both meteorological winter and summer. There is pronounced seasonality in the MEK profiles in the extratropical troposphere, with higher MEK mixing ratios observed in summer than in winter. MEK in clean air over the remote oceans correlates with both acetone and acetaldehyde, whose primary sources in the ocean water are the photooxidation of organic material. We show that even a small (>1 nM) concentration of MEK in surface waters is sufficient to allow the ocean to be a net source of MEK to the atmosphere over ocean basins across multiple seasons. Plain language summary: Methyl ethyl ketone (MEK) is an abundant but understudied gas in Earth' atmosphere, which is emitted into the atmosphere from both human and natural sources. When MEK is broken apart by ultraviolet sunlight, the products released by those reactions play important roles in the formation and destruction of air pollution. In this paper, we show that the oceans are a source of MEK to the atmosphere. The oceanic emissions we document correlate strongly with some other gases that are known to be produced in the ocean but not those most closely associated with the growth of microscopic oceanic phytoplankton. Finding this new source helps us better understand the importance of MEK to the atmosphere and provides guidance for future oceanic and atmospheric research. Key Points: We use aircraft observations of MEK from the remote marine troposphere to suggest that the ocean is a source of MEK to the atmosphereEvidence exists for this source in both winter and summer in the tropical Pacific, south Atlantic and Pacific, and in the Southern OceanMEK in clean air over the remote oceans does not correlate with DMS, but it does correlate with acetone and acetaldehyde [ABSTRACT FROM AUTHOR]

This paper deals with the heat transfer monitoring occurring within an inaccessible membrane distillation system. The membrane separates heated sea water and filtered cooled drinkable water. By adjusting the temperature of the incoming heated sea water and knowing its temperature distribution, engineers can keep its temperature within its best operating parameters and avoid hot spots to form. This would help prolong its life cycle and minimize the cost of the distillation process. In particular, we show that an external observation is enough to reconstruct the temperature of the membrane, which is considered as an unknown source term in a parabolic system. [ABSTRACT FROM AUTHOR]

In this paper we present an expert system that monitors seawater quality and pollution in northern Greece through a sensor network called Andromeda. The expert system monitors sensor data collected by local monitoring stations and reasons about the current level of water suitability for various aquatic uses, such as swimming and piscicultures. The aim of the expert system is to help the authorities in the decision-making process in the battle against pollution of the aquatic environment, which is vital for public health and the economy of northern Greece. The expert system determines, using fuzzy logic, when certain environmental parameters exceed certain pollution limits, which are specified either by the authorities or by environmental scientists, and flags up appropriate alerts. [ABSTRACT FROM AUTHOR]

In the Arctic Ocean (AO), net community production (NCP $NCP$) has displayed spatially heterogeneous responses to sea ice reduction and associated environmental changes. Using a random forest machine learning model trained with >42,000 in situ measurements and concurrent, collocated environmental predictors, we reconstructed 19 years of 8‐day, 6‐km NCP $NCP$ maps. During 2015–2021, the integrated NCP $NCP$ between late‐May and early‐September (NCPint ${}_{\mathit{int}}NCP$) over the western AO was 10.95±3.30TgC $10.95\pm 3.30\,\text{Tg}\,\mathrm{C}$ per year, with interannual variations positively tracking open water area. While the relationship between NCPint ${}_{\mathit{int}}NCP$ and open water area was quasi‐linear at high latitudes, strong nonlinearity was detected on the inflow shelf. The nonlinearity highlights that the NCPint ${}_{\mathit{int}}NCP$ increase resulted from area gain could be compounded by sea‐ice loss induced ecosystem adjustments. Additional retrospective analysis for 2003–2014 suggests a potential long‐term increase of export production and efficiency in the western AO with sea ice loss. Plain Language Summary: Net community production (NCP $NCP$) refers to the portion of phytoplankton production that remains unused by consumers and can be exported to the deeper part of the ocean. In the western Arctic Ocean (AO), NCP $NCP$ patterns are uneven due to complex interactions between the physical environment and the ecosystem. In this study, we developed a machine learning model of NCP $NCP$ in the western AO. The model used publicly available underway measurements and the associated environmental variables to create long‐term, high‐resolution maps of NCP $NCP$. For the period of 2015–2021, we found that the integrated NCP $NCP$ between late‐May and early‐September (NCPint ${}_{\mathit{int}}NCP$) was 10.95±3.30TgC $10.95\pm 3.30\,\text{Tg}\,\mathrm{C}$ per year in the western AO. NCPint ${}_{\mathit{int}}NCP$ varied from year to year and was higher when the open water area was larger. Notably, on the inflow shelf, NCPint ${}_{\mathit{int}}NCP$ increased at a faster rate than a linear relationship would suggest, due to both area expansion and ecosystem adjustments induced by sea ice loss. Our findings indicate that with long‐term sea ice loss, the western AO is likely to export more phytoplankton production to deeper ocean waters. Key Points: A multiyear, gap‐free net community production (NCP $NCP$) product was constructed using a machine learning model for the western Arctic OceanSeasonally and regionally integrated NCP $NCP$ responded to sea ice loss quasi‐linearly at high latitudes but nonlinearly on the inflow shelfCompared with the 2010s, carbon export production has increased in recent years, accompanying sea ice loss in the western Arctic Ocean [ABSTRACT FROM AUTHOR]

Myctophids are one of the most diverse and abundant fish families in the mesopelagic zone, making them a key component in the marine pelagic community. In the North Atlantic, Benthosema glaciale (glacier lantern fish) is considered the most abundant myctophid north of 35° N, yet some regions within its extensive range lack information on its basic biological parameters. We investigated the growth and described the distribution of B. glaciale in Icelandic waters, including the southern continental shelf, Iceland Basin, and Irminger Sea. Length distribution, growth, relative body condition, age, and otolith‐fish size relationships were analyzed from samples collected opportunistically with pelagic trawls during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) in July 2020. In total, 1374 individuals were caught, and only a subset of 225 were measured fresh at sea and 89 were frozen and dissected on land. Total lengths of fresh fish ranged from 38 to 85 mm, while dissected individuals ranged from 40 to 74 mm and were 2 to 6 years old. Located over the Reykjanes Ridge in the Iceland Basin region, individuals had a significantly higher mean standard length and mean age, and a lower mean body condition. We reported length–weight relationships for both fresh and frozen samples, indicating evidence that preserving of the specimens through freezing affected relationships. The von Bertalanffy growth curve was calculated along with significant otolith‐fish size relationships where r2 values ranged between 0.87 and 0.92. Our research highlights the importance of cross‐regional studies and provides baseline biology for B. glaciale in Icelandic waters, specifically in the southern continental slope and Reykjanes Ridge. [ABSTRACT FROM AUTHOR]