Ocean Offshore Research Articles

A Method for Constructing an Empirical Model of Short-Term Offshore Ocean Tide Loading Displacement Based on PPP

A Method for Constructing an Empirical Model of Short-Term Offshore Ocean Tide Loading Displacement Based on PPP

Restorative function of offshore longline mussel farms with ecological benefits for commercial crustacean species

Offshore ocean aquaculture is expanding globally to meet the growing demand for sustainable food production. At the United Kingdom's largest longline mussel farm, we assessed the potential for the farm to improve the habitat suitability for commercially important crustaceans. Modelled distribution patterns (GAM & GLM) predicted the low complexity seabed beneath the mussel farm was 34–94 % less suitable for European lobster (Homarus gammarus) and brown crab (Cancer pagurus) than nearby rocky reefs. The mussel farm operations, however, contributed large amounts of living mussels and shell material to the seabed. Acoustic telemetry revealed that H.gammarus remained within the farm for between 2 and 283 days using both the farm anchors and areas of seabed dominated by fallen mussels for refuge. In contrast, C. pagurus movements showed no affinity to either the farm infrastructure or benthic habitat under the farm. Stable isotope analysis indicated a high dietary niche overlap in C. pagurus and H. gammarus (67.8 and 84.6 %) between the mussel farm (mixed muddy sediment) and nearby rocky reef. Our mixed-methods suggest that the mussel farm augments structural complexity on the seabed providing refuge and similar feeding opportunities for lobster and crab as their typical habitat on rocky reefs. Longline mussel farms can deliver profound biodiversity-positive effects through biogenic augmentation of degraded habitat for commercial species and potential for co-benefits to local fisheries.

Influence of wave spreading on offshore wind turbine design: IEA 15-MW scenario

Offshore ocean waves are directionally spread, whereby the propagation of energy travels in different directions. Despite this multi-directionality, the use of 3-dimensional wave models for loading on fixed offshore wind turbines has been limited. This is partially due to the common assumption that uni-directional sea-states are conservative within a design philosophy. This may not always be true given that in operating conditions the amount of aerodynamic damping in the side-side direction is much lower than the fore-aft direction. This paper aims to address this issue by providing the influence of wave spreading on various offshore wind turbine design scenarios: fatigue, ultimate and service limit state design. This study demonstrates that wave spreading indeed results in more fatigue damage for operating load cases. Despite this, the overall fatigue and ultimate limit state utilisation is still reduced when a wave spreading is adopted.

3-D Changes of Tropospheric O3 in Central and Eastern China Induced by Tropical Cyclones over the Northwest Pacific: Recent-Year Characterization with Multi-Source Observations

In this study, the multi-year data of meteorology and O3 from remote sensing and ground observations are applied to characterize the 3-D changes of O3 in the troposphere over central and eastern China (CEC) induced by the tropical cyclones (TCs) in the tropical and subtropical ocean regions over Northwest Pacific. The CEC-regional average of near-surface O3 levels is significantly elevated with 6.0 ppb in the large coverage by the TCs in the subtropical ocean, while the TCs in the tropical ocean alter near-surface O3 weakly, indicating the latitudinal-located TCs in the subtropical offshore ocean could largely influence the O3 variations over CEC. The sub-seasonal change with the positive and negative anomalies of near-surface O3 is induced by the tropical TCs from June to July and from August to October. The peripheral circulation of TCs in the subtropical offshore ocean persistently enhances the O3 concentrations over CEC during the season of East Asian summer monsoons. The positive O3 anomalies maintain from the entire troposphere to the lower stratosphere over CEC in the peripheries of subtropical TCs, while the tropical TCs cause the positive O3 anomalies merely in the lower troposphere. The O3 transport and accumulation, photochemical production and stratospheric intrusion are climatologically confirmed as the major meteorological mechanisms of TCs affecting the O3 variations. This study reveals that the downward transport of stratospheric O3 of TCs in the subtropical ocean exerts a large impact on the atmospheric environment over CEC, while the regional O3 transport and photochemical productions dominate the lower troposphere over CEC with less impact of stratospheric intrusion from the TCs in the tropical ocean region. These results present the climatology of tropospheric O3 anomalies in China induced by the TCs over the Northwest Pacific with enhancing our comprehension of the meteorological impact on O3 variations over the East Asian monsoon region.

Aquaculture’s offshore frontier: learning from the Canadian courts on ocean grabbing, ocean privatization, and property as process

Many coastal nations have endorsed the Blue Economy as both an economic and environmental opportunity, despite numerous questions as to how industrial expansion into deep ocean waters might be regulated for sustainability. Aquaculture is one industry actively promoting a move offshore, with numerous offshore leases in development. Drawing on the history of aquaculture in the nearshore, and relying on a processual approach to property, we explore questions around the regulation of privatized ocean spaces: What can court cases involving aquaculture in the nearshore tell us about the role of law in promoting sustainable offshore ocean spaces? And what in turn does this suggest about extractive capitalism, the privatization of ocean spaces, and the law? We examine 46 Canadian court cases which cover a 30-year time frame and multiple Canadian jurisdictions. We argue that there are lessons here regarding the questionable ability of law to effectively regulate existing or future aquaculture operations once privatization emerges. The lessons from these Canadian court cases, taken together with a burgeoning literature on legal geography, more-than-human methodologies, and critical environmental law, suggest the varied legal dimensions of deep-sea aquaculture frontier imaginaries and highlight the real limits to regulating the extraction of resources in this perceived open space (terra nullius). We highlight crucial barriers to sustainability through what we are calling jurisdictional opaqueness in regulatory issues. The results include poor regulation and overlapping or contested jurisdictions, which relates in turn to inadequate consultation, frequent environmental problems (toxic chemicals, anoxia, salmon escapes, marine debris), and scientific disputes.

Global ocean spatial suitability for macroalgae offshore cultivation and sinking

Macroalgae offshore cultivation and sinking is considered a potentially practical approach for ocean-based carbon dioxide removal. However, several considerations need to be resolved to assess the effectiveness and sustainability of this approach. Currently, several studies focus on the area required for climate-relevant carbon sequestration through macroalgae cultivation and sinking without considering realistic, global spatial limitations. This study uses a spatially-explicit suitability assessment model for optimised open-ocean afforestation and sinking site designation. By applying specific maritime, ecological and industrial constraints, two maps are produced: a) suitable areas for macroalgae offshore cultivation and sinking, and b) suitable areas for macroalgae sinking only (for sequestration purposes). These data provide a more realistic approach to quantifying the ocean surface (including the corresponding depths) required for macroalgae offshore cultivation and sinking within a spatially sustainable framework. The resulting maps estimate the respective suitability areas within the EEZs of the world countries. A total area suitable for macroalgae offshore cultivation and sinking is calculated at 10.8M km2, whereas sinking-only areas account for 32.8M km2 of the offshore ocean. The implications of spatial suitability patterns at global and national levels are discussed. We suggest that the concept of ‘grow nearshore, sink offshore’ should be explored as an alternative to offshore cultivation.

Hydroelastic response of Froude scaled stiffened steel panels exposed to design-critical wave slamming

Stiffened steel panels of offshore ocean structures may experience violent wave impacts which needs to be accounted for in design. The slamming pressures are often measured in scaled wave tank tests and imposed on finite element models to obtain local structural responses. These responses are sometimes high, which has raised the question if hydroelastic effects are properly accounted for. One way to address the uncertainty of hydroelasticity, is to carry out hydroelastic model tests and compare measurements statistically with FEA calculations. This paper presents the hydroelastic model tests required for this type of comparison. Approximate elastic panels representing Froude scaled stiffened steel panels were 3D printed, validated, and then installed in a vertical column in a wave tank. The elastic panels were exposed to design critical wave slamming during irregular wave conditions relevant for the North Atlantic. Two different elastic panels were tested, one strong and one weak panel. The hydroelastic response of the elastic panels are reported in detail and shows that the panel responds with a limited set of frequencies. In most cases the strain time series of the stiffeners and girders obtain its maximum value during the first half period of vibration. Furthermore, the vibration of the panels generally show strong decay after the time of maximum strain. The extreme strains fit reasonably well with the Gumbel distribution. Furthermore, the variability of the extreme strains, measured as the coefficient of variation (COV), is comparable to the variability of slamming pressures from literature, for the strong elastic panel, but is found to be reduced significantly for the weak elastic panel.

Millions of Caper Whites <i>Belenois aurota</i> 100 km offshore of West Africa

At least 4.3 million Caper Whites Belenois aurota were observed at sea in the Atlantic Ocean offshore of Senegal and The Gambia between 14 and 18 October 2003. They were moving to the southwest, carried by the northeasterly wind.

Negative surface charge-mediated Fe Quantum dots with N-doped graphene/Ti3C2Tx MXene as chlorine-resistance electrocatalysts for high performance seawater-based Al-air batteries

Compared to conventional alkaline Aluminum-air (Al - air) batteries, seawater-based Al-air batteries are promising large-scale energy storage devices and are highly compatible with offshore ocean locations or large-scale maritime applications. However, the complexity of the seawater components, in particular, chlorine anions (Cl−) blocks the metal surface and hinders the oxygen reduction reaction (ORR) at the cathode. Herein, we employed plasma engineering to anchor Fe Quantum dots (QDs) on a negative charge-mediated surface composed of nitrogen-doped graphene (NG) and Ti3C2Tx MXene. The negative fluorine and hydroxyl groups on MXene and NG induced strong negative-charged surface with a build-in electric field to repel Cl−, effectively protected the Fe QDs active sites from the seawater electrolyte. As a result, the cathode electrocatalysts demonstrated high ORR catalytic activity in seawater electrolytes and achieved a high-power density output of 53.6 mW/cm2 and rate performance of 0.8 V at 50 mA/cm2 in Al-air seawater batteries.

Thermal and Dynamical Characteristics of Landfalling Severe Typhoons in South China against Different Monsoon Backgrounds

The characteristics of landfalling severe typhoons (LSTYs)—i.e., typhoons with landfall intensities of 2 min with a mean maximum sustained wind ≥41.5 m s−1—in South China (SC) were here examined. Thirteen LSTYs have been recorded in SC since 1949, and most of them underwent a rapid intensification before landfall. The LSTYs were classified into three categories based on the intensity of the western North Pacific summer monsoon, i.e., as weak, moderate, and strong monsoons. The characteristics of the three types of LSTYs are markedly different. Two LSTYs (7317 and 1523) were developed against a weak monsoon (WM) background and did not have abundant monsoon water vapor drawn into the typhoon cores. Therefore, these two LSTYs exhibited smaller horizontal outer sizes and weaker “warm–wet” cores than those in moderate and strong monsoons. However, a warm offshore ocean supplied a sufficient amount of energy, favoring these two LSTYs’ rapid intensification before landfall. There have been five LSTYs (9113, 0518, 0816, 1320, and 1826) that formed under strong monsoon (SM) conditions but obtained a poor energy supply from the coastal ocean. Embedded in the SM, the vigorous warm–wet monsoon flow was drawn into the typhoons and persisted for several days until landfall. Then, the five LSTYs developed strongly at the greatest horizontal scale and were maintained as severe typhoons for almost 48 h before landfall. The beneficial warm–wet atmospheric circulation stimulated the strongest warm (wet) core at the upper (lower) level of the LSTYs, and a secondary, low-level warm core occurred as well. In moderate monsoon (MM) cases (8106, 9617, 1311, 1410, 1418, and 1714), the strength of the monsoon flow, the “warm–wet” core of the typhoon, and the ocean energy supply were ranked just between those of the LSTYs in WMs and SMs. The development of the LSTYs in the MM cases resulted from a combination of the effects of monsoon and ocean energy supply. In addition, the powerful upper-level divergence ascribed to the strong South Asia High may have played an auxiliary role in MM cases. From the perspective of the sea surface temperature (SST) response to the LSTYs, because of a relatively fast translation speed and the warmer subsurface ocean, the SST cooling was weakest for WM cases. However, the strongest SST cooling was found in SM cases and it was partially due to their slowest translation speed.

CEER: Cooperative Energy-Efficient Routing Mechanism for Underwater Wireless Sensor Networks Using Clusters

Underwater acoustic sensor networks (UWASNs) aim to find varied offshore ocean monitoring and exploration applications. In most of these applications, the network is composed of several sensor nodes deployed at different depths in the water. Sensor nodes located at depth on the seafloor cannot invariably communicate with nodes close to the surface level; these nodes need multi-hop communication facilitated by a suitable routing scheme. In this research work, a Cluster-based Cooperative Energy Efficient Routing (CEER) mechanism for UWSNs is proposed to overcome the shortcomings of the Co-UWSN and LEACH mechanisms. The optimal role of clustering and cooperation provides load balancing and improves the network profoundly. The simulation results using MATLAB show better performance of CEER routing protocol in terms of various parameters as compared to Co-UWSN routing protocol, i.e., the average end-to-end delay of CEER was 17.39, Co-UWSN was 55.819 and LEACH was 70.08. In addition, the average total energy consumption of CEER was 9.273, Co-UWSN was 12.198, and LEACH was 45.33. The packet delivery ratio of CEER was 53.955, CO-UWSN was 42.047, and LEACH was 30.31. The stability period CEER was 130.9, CO-UWSN was 129.3, and LEACH was 119.1. The obtained results maximized the lifetime and improved the overall performance of the CEER routing protocol.

Study on the Track and Degree of Pb Content Transportation

Heavy Pb pollution has been noted in many developed countries. This study examined Pb pollution in Jiaozhou Bay for human security. We used the survey data on the Jiaozhou Bay waters of May, September and October 1994, the results examines Pb content and its horizontal distribution in the surface water bodies, which showed that the in the waters of Jiaozhou Bay Pb content expresses the range of 0.12-2.48 μg/L, agreeing with the seawater standards of Class I and II. Moreover, it has been noted that by the view of Pb content, Pb content in May, September and October polluted the Jiaozhou Bay water bodies softly. In May, September and October, the Pb content in the waters of Jiaozhou Bay ranged from 0.12 to 1μg/L, 0.84 to 1.34 μg/L, and 0.92 to 2.48 μg/L. These results show that Pb content in May did not pollute the Jiaozhou Bay water bodies. While Pb content during September and October slightly polluted. Three sources transported mainly Pb content into Jiaozhou bay. These sources are rivers, land surface runoff and offshore ocean currents. The rivers transported the Pb content 0.47-2.48 μg/L, the land surface runoff 2μg/L and the offshore ocean currents 1.34 μg/L. It demonstrates that Pb slightly polluted rivers, land surface runoff and offshore ocean currents in the transportation of Pb. From May to October, rivers transported Pb content which varied significantly. In September, land surface runoff transported Pb content during the rainy season. In addition, the offshore currents also transported Pb content to the waters of Jiaozhou Bay. Human activities discharged Pb content to land and transported it to the ocean, relying on the land surface runoff and rivers. Thus, two channels were transporting Pb content on land to the ocean, increasing Pb content. Through ocean currents, Pb content was transported from the high-content water area to the low-content water area. Therefore, the Pb content transported by rivers and land surface runoff could raise concerns from humans.

Influence of Human Activity on Hg Transportation

Hg pollutes the environment, living organisms, and humans; hence, studying Hg content is essential for human health security. Using the dataset in May, September, and October, the Hg content, horizontal distribution, sources and transportation paths in the waters of Jiaozhou Bay were easily determined. These results indicate that the Hg content changing range in the waters in May, September and October was 0.015-0.150 μg/L, corresponding to the national seawater quality standards of Class I and Class II. The Hg content in the water body mainly arises from two sources, the transportation of rivers and offshore ocean currents. It from rivers' offshore ocean currents was 0.019-0.150 μg/L and 0.020 μg/L, respectively. Among them, the transportation of rivers includes the transportation of Haibo River, Licun River and Loushan River. So, a model block diagram has been built to unveil Hg contents and its different paths during the transportation to Jiaozhou Bay. Thus, it becomes easy to quantitively determine the migration process of Hg content through human activities to the ocean and rivers. Hg's different paths and contents reveal four rules for entering Jiaozhou Bay. In May, the offshore ocean currents and Haibo River did not affect by Hg pollution. In September, the Laoshan River was not polluted by it. In October, the Licun River was not, while the Haibo River exhibited light Hg pollution. When the Hg content transported by rivers was relatively low, it by offshore ocean currents became visible. From May to October, three rivers were transporting Hg content. Hg mildly polluted only one river in October, depicting that human activity is a key concern for environmental protection. It discharged by humans to land was relatively low, meanwhile only once was river transportation slightly polluted by it.

Sequential scavenging and measurement of seawater radiocesium concentrations and plutonium isotopic ratios offshore Fukushima

The scientific interest in radiocesium and plutonium found in the oceans and seas has increased enormously in the past years as a consequence of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident and is expected to be ongoing due to many unresolved questions. Hence, continuous development of new and verification of old analytical methods should be at the top of the list of the community, working on the topic. In this study, we processed and analyzed several seawater samples, collected in different time frames (2011–2015) from the North Pacific Ocean offshore Fukushima, to determine their radiocesium activities, 134Cs/137Cs activity ratios and 240Pu/239Pu isotopic ratios using the sequential scavenging method, gamma spectrometry and accelerator mass spectrometry (AMS). The observed radiocesium levels in seawater (0.07–0.042 Bq L−1) clearly indicated that the investigated region remained impacted by releases from the damaged power plant even after four years after the accident. Regarding plutonium, its successful separation from large volume seawater samples was confirmed by detection of 240Pu by AMS. However, several problems emerged during the analyzes, which we tried to address with the use of additional methods (e.g., measurements of uranium by ICPMS). The efficiencies of the applied methods and other issues are also discussed.

Canada’s Internet-Connected Ocean

Over fifteen years ago, Ocean Networks Canada (ONC) began with the world’s first large-scale, interactive, real-time portal into the ocean, bringing continuous, real-time data to the surface for applications in scientific research, societal benefits, and supporting Canada’s ocean industry. This marked the dawn of the Internet-connected ocean, enabling a more fulsome understanding of the ocean through ocean intelligence. These open data have improved our ability to monitor and understand our changing ocean offshore all three coasts of Canada, thanks to diversity of sensor systems to monitor earthquakes and tsunamis, deep sea biodiversity, whales, hydrothermal vents, neutrinos, ocean noise, ocean acidification, forensics experiments, and the impact of climate change, including sea ice thinning in the Arctic. This pioneering approach began in the late 1990s, when scientists began developing a new way of doing ocean science that was no longer limited by weather and ship-time. They imagined a permanent presence in the ocean of sensors to allow a continuous flow of ocean data via the Internet. This big science began to take shape early this century, when a partnership between United States and Canadian institutions was established. ONC evolved out of this international collaboration with seed funding from the Canada Foundation for Innovation, while in the United States, the Ocean Observatories Initiative (OOI) was funded. ONC works closely with OOI on that span the countries’ west coast border. Recently similar observing initiatives in Europe have begun, led by EMSO, which now has a close collaboration with ONC as an Associate Member.

Oxidative stress and motion sickness in one crew during competitive offshore sailing

Competitive Offshore Ocean Sailing is a highly demanding activity in which subjects are exposed to psychophysical stressors for a long time. To better define the physiological adaptations, we investigated the stress response of subjects exposed to 3-days long ocean navigation with disruption of circadian rhythms. 6 male subjects were involved in the study and provided urine and saliva samples before setting sail, during a single day of inshore sailing, during 3-days long ocean navigation, and at the arrival, to measure oxidative stress, cortisol, nitric oxide metabolites (NOx) and metabolic response. Motion Sickness questionnaires were also administered during the navigation. The crew suffered a mean weight loss of 1.58 kg. After the long navigation, a significant increase in ROS production and decrease in total antioxidant capacity and uric acid levels were observed. Lipid peroxidation, NO metabolites, ketones, creatinine, and neopterin levels were also increased. Furthermore, a significant increase in cortisol levels was measured. Finally, we found a correlation between motion sickness questionnaires with the increase of NOx, and no correlation with cortisol levels. Physical and psychological stress response derived from offshore sailing resulted in increased oxidative stress, nitric oxide metabolites, and cortisol levels, unbalanced redox status, transient renal function impairment, and ketosis. A direct correlation between motion sickness symptoms evaluated through questionnaires and NOx levels was also found.

Fault-Tolerant Control of an Offshore Ocean Thermal Energy Conversion System with Output Constraints

A fault-tolerant control method is investigated for an offshore ocean thermal energy conversion (OTEC) system with constraints in this work. In the system modelling, the distributed parameter system is used to build the OTEC system, which is expressed by a set of partial differential equations (PDEs) and ordinary differential equations (ODEs). Moreover, a boundary fault-tolerant control scheme is proposed to solve actuator failures. Meanwhile, according to the control scheme, system vibration suppressing and system stability can be realized. Two proposed coupled controllers are designed to solve actuator faults while considering the output nonlinearity of the OTEC system. In addition, the stability of the OTEC system based on barrier Lyapunov function is proven by simulation results, which verifies the effectiveness of the proposed coupled fault-tolerant-boundary control method. Finally, the proposed method can effectively improve the performance and safety of ocean thermal energy conversion in the OTEC system.

Effects of Wave–Current Interaction on the Eastern China Coastal Waters during Super Typhoon Lekima (2019)

AbstractLekima was a devastating super typhoon hitting China in 2019. Here, we use a high-resolution wave–current coupling model to investigate the impacts of wave–current interaction during Lekima on wave height, storm surge, ocean currents, and momentum balance. The model results were in good agreement with observations. It was found that, in the open waters, the strong currents generated by the typhoon winds reduced the typhoon-induced maximum significant wave heights (MSWHs) by 6%–15%. The baroclinicity of seawater also slightly reduced the MSWHs by approximately 3%. In the coastal waters, the MSWHs were increased by 6%–15% when feedbacks from water levels were considered. The typhoon-induced highest storm surge occurred in the coastal waters right of the typhoon’s landing position. The nonconservative wave forces contributed by approximately 0.1–0.4 m to the most severe storm surge (3 m), with this effect being most prominent in coastal waters. The baroclinicity of seawater generally increased the storm surge but had little influence on very shallow waters. Tides tend to exacerbate storm surge in most nearshore waters, except in a small bay. Waves generally increased the velocity of offshore ocean currents via the wave-breaking-induced acceleration. A cross-shore momentum balance analysis shows that when the typhoon was near the shore, the dominant terms in the momentum equation were the horizontal pressure gradient force and the surface wind stress, and the contribution of wave breaking had similar pattern to that of the wind stress but a lower magnitude. Our findings have significant implications for the numerical modeling of typhoons and the prediction of their impacts in the coastal environment.

Cross‐Shore Flow and Implications for Carbon Export in the California Current Ecosystem: A Lagrangian Analysis

AbstractEastern Boundary Current Upwelling Systems are regions of elevated primary production and carbon export and thus play a central role in the global carbon cycle. In these regions, nutrient upwelling occurs in a narrow region close to the coast, but primary production and carbon export are typically observed across a broader region. The fact that productive waters reach the open ocean has important consequences for the biological carbon pump, because such transport connects nutrient sources close to the coast to the deep carbon sinks of the offshore ocean. However, many aspects of this offshore transport are still not known. Here we address seasonal and interannual variability of upwelling‐related cross‐shore flows in the California current ecosystem (CCE) by employing Lagrangian diagnostics of horizontal transport inferred from satellite data. We define an advective age as the time a water parcel flowed offshore of the 500 m isobath. We find that the offshore extension of high Chl‐a waters covaries with the age of a coastal water parcel, and is consistent with mesoscale circulation. Interannual variability in the offshore extent of older waters is primarily driven by mesoscale variability and covaries with large scale forcing by both ENSO and the NPGO. The measured ratio of in‐situ new production: carbon export also covaries with water age, and tends to be ≫ 1 in younger and more balanced in older waters. Our results may help to parameterize the role of the finescale on the export of carbon in upwelling regions for climate resolving models.

Realized profits on the Stationary Offshore Ocean Economy: an analysis

This paper analyzes the recent financial performance of the publicly traded companies that employ stationary structures on the open ocean using a comprehensive Thomson Reuters Eikon search. These companies are found in the offshore aquaculture, wind and drilling sectors together with their respective equipment providers, and together comprise the Stationary Offshore Ocean Economy. The findings indicate that offshore aquaculture, though still in its infancy, is emerging noticeably and showing promise. In our study, the performance of offshore wind providers was generally very favorable while the performance of offshore wind equipment manufacturers tended to be weak, although this was sometimes mixed. The performance of offshore drilling services also varied, having been heavily influenced by the 2014 oil price declines. As economic development continues offshore, it is expected that a broad array of new economic opportunities and systems may emerge. These opportunities and systems could lead to greater flourishing and upward mobility in the global population. Future research should focus on identifying industries that may emerge from moving offshore to the extreme, that is, to the point of being outside the exclusive economic zones of any country.