Deeper Water Depths Research Articles

A more complete and detailed glacial history of the northwestern Chukchi margin—Implications for the existence and evolution of the East Siberian-Chukchi ice sheet

It is speculated that an united East Siberian-Chukchi Ice Sheet (ESCIS) existed on the East Siberian-Chukchi margin during the Pleistocene era. However, details regarding the frequency of its occurrence and the intensity of each glaciation remain unclear. Critical information lies in the northern part of the East Siberian-Chukchi margin because this region preserves relatively complete glacial landforms and deposits, especially in areas of deep-water depths. In this paper, new full-coverage multibeam data from the outer shelf–ocean basin on the western side of the Chukchi Rise of the northwestern Chukchi margin are presented, and more complete submarine glacial landforms in this area are identified. In addition, we provide a more detailed interpretation of the entire glacial strata using a compilation of new sub-bottom profiler data. Interpreted glacial landforms and buried glaciogenic debris flows (GDFs) indicate that the western side of the Chukchi Rise was affected by the Chukchi Ice Sheet. Overall, the glacial landforms can be divided into two categories, i.e. those in an ice stream setting on the Southwestern Margin and an inter-ice stream setting on the Northwestern Margin. However, in the current inter-ice stream area, large old gullies and GDFs persist, indicating dynamic changes between the ice stream and inter-ice stream zones. Since the onset of glaciation began around ∼0.8 Ma, the study area has experienced a total of nine glaciations, including three intense glaciations, five intermediate glaciations, and 1 mild glaciation. Through a comparison with the GDFs on the eastern slope of the Arliss Plateau which locates further west of the Chukchi Rise, we infer the existence of at least four unified ESCISs during the Quaternary.

Effect of photons and electrons on the over-response of optical fiber X-ray sensors

Optical fiber X-ray sensors are prone to over-response compared to ionization chambers (ICs) when used to measure the percentage depth dose (PDD) curves and off axis ratio (OAR) curves. Investigating this phenomenon is crucial for the successful adoption of these sensors in clinical radiotherapy. Compared with ion chambers and other water equivalent dosimeters, the fiber X-ray sensors using high Zeff scintillators (Gd2O2S:Tb) have generally higher mass attenuation coefficients. In this case, the response of scintillators to photons needs to be considered. In this article, a Monte-Carlo (MC) software package BEAMnrc was used to simulate the distribution of photon and electron fluxes in a clinical based water phantom, besides the energy deposition of air and Gd2O2S:Tb in varying energy was also simulated. The distribution of the photon and electron fluxes in the horizontal (radial) direction at a fixed 10 cm water depth was studied, as well as the fluxes in the vertical (depth) direction. An embedded-structure fiber X-ray sensor was used for the experimental measurements. The simulation results indicate that, in the horizontal direction, there are many photons remain outside the radiation field. In the vertical direction, as the size of the radiation field increases, the maximum point of the photon flux shifts towards a deeper water depth. These behavior of photon flux is consistent with the fiber X-ray sensors measurement. However, the maximum point of the electron flux remains unchanged in the vertical direction. In the horizontal direction, the electron flux decreases rapidly, and this scenario is similar to the case when using the ion chamber. Results of analyzing the spectra inside and outside the radiation field show that there is a large number of photons with energy below 0.2 MeV outside the radiation field, and the proportion of these low-energy photons is greater than 60 %. The findings indicate that the fiber X-ray sensors' over-response can be primarily attributed to the lower energy scattered photons.

Effect of wave-dependent mechanisms on storm surge and current simulation during three extreme weather systems

Abstract The wave effect is crucial to coastal ocean dynamics, but the roles of the associated wave-dependent mechanisms, such as the wave-enhanced surface stress, wave-enhanced bottom stress, and three-dimensional wave force, are not yet fully understood. In addition, the parameterizations of each mechanism vary and need to be assessed. In this study, a coupled wave-current model based on the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) model system was established to identify the effect of the wave-dependent mechanism on storm surges and currents during three typical extreme weather systems, i.e., cold wave, extratropical cyclone, and typhoon systems, in a semi-enclosed sea. The effects of the three coupled mechanisms on the surface or bottom stress, in terms of both the magnitude and direction, were investigated and quantified separately based on numerical sensitive analysis. A total of seven parameterizations is used to evaluate these mechanisms, resulting in significant variations in the storm surge and current vectors. The similarities and differences of the wave-induced surge and wave-induced current among the various mechanisms were summarized. The change in the surface stress and bottom stress and the excessive momentum flux due to waves were found to mainly occur in shallow nearshore regions. Optimal choice of the combination of parameterization schemes was obtained through comparison with measured data. The wave-induced current in the open waters with a deep-water depth and complex terrain could generate cyclonic or anticyclonic current vorticities, the number and intensity of which always increased with the enhanced strength and rotation of the wind field increased.

Spatio-temporal variations of lacustrine groundwater discharge and related nutrient fluxes in a typical lake in front of hillocks

Lacustrine groundwater discharge (LGD) as a hidden hydrologic process has been widely found to affect water and nutrient balance in various lakes, but a comprehensive research on both spatial and temporal variations of LGD and associated nutrient fluxes was poorly conducted. Herein, this study elucidated their spatio-temporal variations and underlying factors of a typical lake in front of hillocks with spatially variable topography and hydrogeology, and intense seasonal groundwater-lake exchange, within central Yangtze River basin. The 222Rn mass balance model was used in conjunction with hydrochemistry, water isotope, and nutrient data. The results showed that the overall LGD rate and related N/P fluxes were clearly higher in the wet season than in the dry season, for which the stronger evaporation relative to precipitation, more groundwater recharge from agricultural irrigation or aquacultural pond infiltration, and more N/P input from anthropogenic or aquacultural activities could be responsible. In the wet season, the area with more recharge from irrigating water or fish pond water infiltration and associated extensive agricultural or aquacultural activities, had the significantly highest LGD rate and related N/P fluxes. In the dry season, the area with the deepest water depth and largest topographic slope, exhibited the significantly highest LGD rate and slightly higher LGD-related N/P fluxes due to relatively low groundwater N/P concentrations. This study enriched the understanding on LGD and related nutrient fluxes in the perspective of both spatial and temporal variations, taking a new type of lakes (i.e., lakes in the transitional zone of hills and plains in temperate climate) as a typical case.

Shifting Depth Distributions of Deep‐Sea Corals in the Southwest Pacific: Implications for Deglacial Dynamics of the Southern Ocean

AbstractWe compare depth and temporal distributions of sub‐fossil assemblages of two cold‐water scleractinian corals on seamounts in the Southwest Pacific to help define the temporal variations of water mass properties in the Southern Ocean (SO) during deglaciation. Peaks in the deep‐water abundance of the two species complement one another, with Desmophyllum dianthus peaking around the Antarctic Cold Reversal (ACR), and Solenosmilia variabilis briefly during the late Heinrich Stadial 1 (HS1) and during the Younger Dryas (YD). Environmental tolerances of the two species and the geochemistry of S. variabilis carbonate skeletons suggest that their secular distributions reflect complementary effects of temperature (higher at Antarctic Intermediate Water/Upper Circumpolar Deep Water depths during the YD and late HS1) and surface productivity (lower during the YD and HS1). Higher temperatures at depth we interpret as evidence of increased Zonal West Wind (ZWW)‐driven Ekman pumping during the late HS1 and YD, whereas coeval low surface production reflects poleward expansion of sub‐tropical water masses as a result of correlated poleward shifts of the ZWW belt and the Intertropical Convergence Zone. More broadly, a continuous deep coral population in the southwest Pacific that spans two species and three deglacial periods (HS1, ACR and the YD) and an early Holocene shift in coral distribution from deeper to shallower habitats appear to reflect large‐scale changes during deglaciation in SO temperature profiles and productivity.

Mechanical characterization procedure of HMPE fiber for offshore mooring in deep waters

For several offshore installations, especially those for exploration of offshore resources, such as Floating Production Storage and Offloading (FPSO), the stability of subsea pipelines and exploration risers are closely related to the mooring system. High performance polymeric fibers have been used in recent decades for offshore mooring, more recently polyester has been challenged by advancement in ultra-deep waters due to its considerable elongation. A candidate fiber for lower elongation mooring systems is high modulus polyethylene (HMPE). The work describes mechanical characterization procedures in high modulus polyethylene fibers envisioning the possibility of offshore mooring systems made entirely with HMPE, which allow deeper water depths, as well as stability to the pipelines. As a result, the fiber is suitable for mechanical strength and linear tenacity. It still shows good performance in abrasion resistance, and loss of inelastic portions in cyclic loads. However, the behavior in creep, due to its slightly high strain rates, restricts its use, but recent fibers known as "Low creep" can be studied, allowing complete mooring systems made with HMPE.

Environmental radioactivity, radiological hazards, and trace elements assessment of nearshore sediment in the Bay of Bengal

The current study focuses on the environmental radioactivity and multi-risk assessment of nearshore sediment as a source of marine pollution along the Bay of Bengal. The study examines the distribution of primordial radionuclide concentrations using a thallium-activated sodium iodide (NaI(Tl)) detector-based gamma-ray spectrometer and Potentially Toxic Elements (PTE) through atomic adsorption analysis. The data also were used to characterize ecological threats, radiological risks, and the geospatial distribution of toxic compounds in nearshore sediment as a proxy for marine pollution. The active concentration of primordial radionuclides such as uranium-238 (238U), thorium-232 (232Th), and potassium-40 (40K) was found in the range from ≤ 3 to 68 (11.4), ≤ 9.5 to 142.7 (41.2), and 85.2 to 603.4 (362) Bq/kg, and the results show that the average radioactive concentration of the average radionuclides was less than suggested by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) ranges. Potentially toxic elements iron (Fe), chromium (Cr), nickel (Ni), lead (Pb), and zinc (Zn) were higher in deeper water depths. The current study reveals that mud distribution primarily controls such elements. A decreasing order has been seen as follows by the ecological risk index of individual elements: copper (Cu) > lead (Pb) > nickel (Ni) > chromium (Cr) > zinc (Zn). The significant Pb, Cu, and Zn concentrations indicated high pollution at most stations, possibly resulting from regional and terrestrial sources such as industrial activity, urban drainage, manufacturing, and farming. The migration of contaminated soil from the industrial and transportation sectors may be the source of the increased levels of hazardous elements and naturally occurring radionuclides in the sediment transported into the coastal ecosystems of Bay of Bengal.

Comparison of ocean deoxygenation between CMIP models and an observational dataset in the North Pacific from 1958 to 2005

This study investigated the relationship between the observed and simulated dissolved oxygen (O2) inventory changes in the North Pacific by analyzing an observational dataset and the outputs of Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5/6) between 1958 and 2005. A total of 204 ensembles from 20 models were analyzed. Many of the models in the North Pacific subarctic region have higher climatological O2 concentrations than observed at deeper water depths. Therefore, the negative trend of O2 inventories tends to be larger, and in fact, several model ensemble members have a larger negative trend in O2 inventories than observed. The variability among model ensemble members is more influenced by the uncertainty due to internal variability than by the uncertainty resulting from model dependency. An inter-model empirical orthogonal function (EOF) analysis revealed that the different simulated magnitudes of the negative O2 trend is closely associated with the first EOF mode, and ensemble members with strong negative trends are characterized by large oxygen reduction in the subarctic North Pacific, especially around the boundaries between the North Pacific Ocean and the Sea of Okhotsk as well as the Bering Seas. The modeled strong O2 decrease in the subarctic North Pacific is consistent with the spatial pattern of the observed O2 trend. Further analysis of climate models indicated that the O2 decrease in the subarctic region was primarily caused by physical factors. This conclusion is supported by the significantly high correlation is present between the potential temperature and O2 inventory trend in the subarctic region, whereas an insignificant correlation coefficient is present between dissolved organic carbon and the O2 inventory trend. However, the observations have a larger ratio of O2 inventory trend to temperature trend than any of the ensembles, and thus the relationship between O2 and temperature change in the subarctic North Pacific seen in the CMIP5/6 simulations is not exact.

A study on the prediction model of water column sound absorption coefficients considering the characteristics of the East Sea of South Korea

East Sea of Korea has the deepest water depth among Korean seas, and the water column changes are distinct in space and time, resulting in a wide range of water column sound absorption coefficients. In this study, we calculate and analysis the spatiotemporal variation of water column sound absorption coefficient in the East Sea of Korea, which has unique oceanographic characteristics. Using extensive CTD data from the Korea Oceanographic Data Centre (KODC) from 1991 to 2021, we calculate the sound absorption coefficient using the widely applied Francois–Garrison model and reveal the unique absorption characteristics of the East Sea. The derived coefficients are then used to calibrate and improve past multibeam echosounder system (MBES) data, which suffered from incomplete water column information and arbitrary mean values. To facilitate the calculation and development of sound absorption coefficient, a MATLAB-based graphical user interface (GUI) was developed. The results of this study contribute to the calculation and inference of sound absorption coefficients along spatial and temporal dimensions of the water column in the East Sea and to the extraction of more accurate seafloor information from MBES data. This study developed the way for future research focusing on algorithmic advances and new methodologies for the calculation of sound absorption coefficients in the West and South Seas of Korea.

The impact of yaw motion on the wake interaction of adjacent floating tidal stream turbines under free surface condition

Several works put emphasis on the maturation of floating tidal stream turbine systems, deemed viable for sites at deep water depths. The objective of this research is to determine, through a CFD model, the yaw effect on the wake and functioning of a floating twin-turbine system under wave-induced motion. The simulation certainty is corroborated against experiments on a 1:7 piled twin-turbine system (Froude similarity). Collectively, the variation and deficiency of the power and thrust coefficients are amplified with the yaw frequency and amplitude. Whereas the individual wakes collide, depending on the yaw feature and turbine cross-current spacing, resembling a smoke-plume-type pattern. The larger cross-current spacing shortens the wakes and reduces near-wake deficit at mid-row due to the greater energy exchange from the ambient flow. Regardless of the yaw feature, the transversal wake deficits turn from double (majority symmetrical) at near wake into triple distributions thenceforth, before flattening at far wake. Importantly, the wake unsteadiness and recovery rate are more obvious with period, as opposed to amplitude effect. As yaw operation is imminent, contributed by flow skewness and platform yaw motion, it will be constructive to implement natural frequency analysis to prevent vortex-induced vibrations and mechanical weariness in the floating system.

Numerical Assessment of the Resistance of a Solar Catamaran in Shallow Water

In this paper, a numerical assessment of the effect of shallow water on the total resistance of the solar catamaran SolarCat is carried out using computational fluid dynamics within the software package STAR–CCM+. The unsteady viscous fluid flow was modelled based on the Reynolds-averaged Navier–Stokes (RANS) equations with the application of the k−ω SST (k−ω Shear Stress Transport) turbulence model. The RANS equations were discretized by the finite volume method, and the position of the free surface is determined by the volume of fluid method. In shallow water conditions, a mesh morphing algorithm is applied. Numerical simulations were carried out for the deep water and limited depths corresponding to h/T=7.6, h/T=4, and h/T=2 at two speeds. The verification study was carried out and the total numerical uncertainty was calculated for the total resistance and sinkage of the catamaran. A detailed analysis of the flow around the catamaran was carried out.

History and performance of the Everglades STA-3/4 periphyton-based stormwater treatment area (PSTA)

The Everglades Stormwater Treatment Areas (STAs) retain phosphorus (P) from stormwater runoff before it enters the Everglades Protection Area. These large treatment wetlands are extremely efficient in reducing total P (TP) concentrations. However, in some cases, the STAs may require additional measures to reach and/or maintain mandated discharge TP concentrations. One such option, a Periphyton-based Stormwater Treatment Area (PSTA) Cell, was constructed in 2005 on 40 ha at the outflow region of one flow-way in STA-3/4. This PSTA Cell was built to determine operational and engineering requirements associated with the implementation of this technology on a large scale. The PSTA Cell has supported an oligotrophic, periphyton-rich treatment wetland over its operational period of record. This system has consistently produced annual flow-weighted mean (FWM) outflow TP concentrations at or near the mandated outflow TP levels. The PSTA Cell maintained optimal treatment performance when subjected to hydraulic conditions observed in other full-scale STA cells (i.e., deeper water depths, pulsed flows, and major storm events). The PSTA Cell's treatment performance appeared to be better (FWM outflow concentrations ∼9 μg L−1) during continuous flows for 21 days compared to intermittent flow periods. Daily PSTA Cell outflows often were ≤ 13 μg L−1 when inflow TP concentrations were ≤ 22 μg L−1. The PSTA Cell also removed additional P from very low inflow concentrations (< 15 μg L−1). Seepage into the PSTA Cell occurred when its stage was lower than stages in adjacent water bodies, but seepage was greatly reduced when stages in the PSTA Cell were increased and the difference in stage between the PSTA Cell and adjacent bodies was reduced. TP concentrations in seepage water were usually higher than the PSTA Cell's inflow or surface water TP concentrations, therefore, the PSTA Cell performance did not benefit from seepage inflows. Over the 13 water years of operation, accretion of new soil (TP < 300 mg kg−1) did not result in nutrient gradients within the PSTA Cell that might affect P performance. Overall, the PSTA Cell study achieved its goal of providing operational and engineering insights for the implementation of this technology on a larger scale, and the PSTA Cell consistently attained ultra-low-P concentrations (mean ± standard deviation) of 10 ± 3 μg L−1 over its operational period of record.

Development of novel natural gas hydrate inhibitor and the synergistic inhibition mechanism with NaCl: Experiments and molecular dynamics simulation

Drilling fluid systems with exceptional performance serve as a foundation for commercial hydrate extraction. However, most hydrate reservoirs are located at relatively deep water depths and have shallow burial depths. As a result, there are high demands on the density of a hydrate drilling fluid system. Thus, the traditional hydrate drilling fluid system no longer meet the drilling needs in deep water shallow hydrate reservoirs. In this paper, a copolymer SYZ-2 was synthesized based on N-Vinyl-ε-caprolactam and N, N-dimethyl acrylamide. The effects of SYZ-2 and its NaCl system on methane hydrate were first tested by a constant rate cooling method, and the inhibition mechanisms of the system on hydrate nucleation and formation were investigated by molecular simulations. Meanwhile, the formulation and properties of a low-density hydrate drilling fluid system (1.06 g/cm3) based on SYZ-2 were also described in detail. The experimental results show that the hydrate formation temperature with the influence of SYZ-2 decreases from 10.6 °C to 2.7 °C, which can even be significantly reduced to −3.1 °C in the presence of 7 % NaCl. The molecular dynamic simulation results show that SYZ-2 inhibits the nucleation of hydrates by decreasing the solubility of methane molecules, primarily by promoting the agglomeration of methane molecules. Additionally, SYZ-2 can also adsorb to the surface of hydrates and prevent the hydrate cage structure from capturing methane molecules. In contrast, NaCl inhibits hydrates formation by restricting the movement of water molecules. These results provide valuable insights into a better understanding of the gas hydrate inhibition mechanisms, the rational development of high-performance hydrate inhibitors for drilling fluids, as well as the construction of drilling fluid systems.

Steady-state Analytical Reservoir Pressure and Temperature Solutions during Hydrogen Refueling to Environment-friendly Ships from Offshore Underground Storage

As hydrogen (H2) conserves intermittent electricity from renewable energies, H2-fueled ships are overlooked for carbon emission reduction. H2-fueled ships require offshore refueling for long-distance shipping routes. At offshore refueling stations, H2 is expected to be generated by renewable energies, stored in depleted offshore reservoirs, and then extracted for refueling. Temperature and pressure variations near the wellbore during H2 extraction impact the severity of hydrogen-induced corrosion. Therefore, it is necessary to conduct hydrothermal analysis for offshore platforms’ front-end engineering design and operation strategy. This paper proposes an analytical reservoir pressure and temperature solution for steady-state offshore H2 extraction from depleted reservoirs for refueling. We derive the radial analytical solution for a two-phase flow (water-H2) and validate them with a numerical model. We apply the derived solution to sensitivity analysis with respect to water depth, reservoir depth, H2 saturation, permeability, reservoir thickness, and total extraction rate. Due to the negative water thermal gradient, deep water depth leads to pressurization and cooling near the wellbore. Critical H2 saturation is derived as a criterion of transition between Joule-Thomson heating and cooling. The higher flow mobility of H2 ensures less depressurization during extraction than water. Higher H2 saturation over the critical saturation causes less cooling due to the decreasing pressure gradient.

Time-series-based habitat model development for surface water management on endangered aquatic plant Isoetes taiwanensis conservation in mountain wetlands

Wetland scientists and ecological engineers are encouraged to comprehend hydrological driving forces for enhancing environmental conservation, ecological restoration, and integrated management. The spatiotemporal distribution and dynamics of aquatic plants are critical for improving their functional niche in mountain wetlands. This study evaluates the hydrological variation of a mountain wetland to determine the adverse and advantageous situations of an endemic and endangered aquatic plant by establishing a time-variant habitat index model considering the inundation frequency and duration of a specific water level. The model was developed and verified by integrating with a field survey of biotic and abiotic data to build the corresponding habitat suitability indices through conducting polynomial regression analysis. The results indicate its capability to effectively quantify the intricate relationship between water level and plant coverage in different places and seasons. The habitat quality can be derived as the combined functions of total scattered and maximum continuous periods of dominant and nondominant water depths. Although the coverage area fluctuated in different seasons, the model reveals significant capabilities to bridge the gaps for reaching the extreme hydrological conditions which might cause the extinction of the endangered aquatic plant Isoetes taiwanensis. The plant is found to be more competitive in the region, implemented by excavation and consolidation, with deeper water depth and higher water conservation. We suggest adaptative water level management at the planning and design phases and rehabilitating these essential habitat patterns to enrich the survival of I. taiwanensis in the dry season. Strengthening the water retention capacity of the bottom soil to reduce water leakage and groundwater seepage velocity may also help achieve integrated management for surface water conservation in the wetland.

Perturbation analysis of nonlinear partial reflected wave on a sloping bottom

In this paper, we use the perturbation method to develop a new mathematical derivation to describe nonlinear partial standing wave over uniformly sloping bottoms. In the Lagrangian coordinate system, the particle trajectories are obtained as a function of the nonlinear order parameter ɛ and the bottom slope α to the second order of the perturbation. The setups and mean return flow for an arbitrary bottom in the Lagrangian framework are also found as part of the solutions. The direct influences of reflection coefficient, wave steepness and bottom slope on the surface profiles of partially reflected waves are also derived. This nonlinear analytical solution is verified by reduction to the classical Stokes solution of progressive waves in both the deep water and constant depth limit. This solution allows to describe the successive deformation of partial reflected wave profiles and water particle trajectories prior to wave breaking to be described. The dynamic properties including mass transport, and Lagrangian mean level and radiation stress for nonlinear partially reflected waves on various sloping bottoms are investigated.

On wave–current interaction in deep and finite water depths

Interaction of linear and nonlinear, long-crested waves with currents in deep and finite water depths is studied by use of the computational fluid dynamics approach. Various wave conditions are considered by systematically changing the wave height and the wavelength. Several current profiles are studied as polynomial functions of water depth following the profiles and magnitudes of the available ocean current data. Both following and opposing currents are considered, and in total, 26 wave–current configurations are investigated. The two-dimensional study is carried out computationally by solving the Navier–Stokes equations for a laminar flow. The governing equations are solved by use of the finite volume approach in an open-source computational fluid dynamics package, namely OpenFOAM. Modifications are made to an existing wave-making toolbox, waves2Foam, to generate combined nonlinear waves and currents in deep and finite waters. Results of the numerical wave–current tank are compared with the existing laboratory measurements and overall very good agreement is observed. Discussion is provided on the effect of these currents on the change of the wave field, including quantitative change of the surface elevation, wave profile, pressure distribution, and fluid particle velocity of waves. Overall, it is observed that opposing current has a remarkable impact on the wave field, and the particle velocity and wave height are affected the most from the presence of the current.

Comparative study of the mating process for a spar-type floating wind turbine using two alternative installation vessels

The offshore wind industry faces many challenges as the water depth of offshore sites increases. For installation of the spar floating offshore wind turbines (OWTs), cost-effective installation methods are needed to facilitate installations at moderate or deep-water depths. In this paper, a novel installation concept initially designed for installing pre-assembled wind turbines is further studied. Two alternative installation vessels (i.e., a catamaran and a small water-plane area twin hull vessel (SWATH)) equipped with a dynamic positioning (DP) system are considered for installing 10-MW OWTs. Hydrodynamic responses of the installation systems are obtained by the fully coupled nonlinear time domain method. Based on the numerical analysis in SIMO-Riflex, a comparative study of the two vessel concepts is conducted to study selected response variables of two mating points. Compared with the catamaran installation vessel, the SWATH substantially reduces dynamic motions during the critical mating phase. The findings of this paper provide references for industrial stakeholders selecting alternative installation vessels and serve as a basis for further optimizing the concept.

New insights on the Late Quaternary evolution of Abrolhos reefs, Eastern Brazilian Shelf

The Abrolhos shelf, in the eastern Brazilian margin, encompasses the largest reef province in the South Atlantic, characterised by low coral diversity and a high level of endemism. Knowledge gaps about how the Abrolhos coastal reefs evolved, during the post LGM and MIS 6/MIS 5, favoured a paradigm that is revisited in the light of new data. Here, new data from two new, long boreholes (20 and 50 m-long) are presented in order to investigate and provide new insights into the evolution of two shallow reefs on the Abrolhos Shelf during the late Pleistocene and Holocene epochs. Results show that Holocene and Pleistocene reefs grew on highly turbid waters with a significant terrigenous sediment input. Corals and CCA assemblages were identified as main framework builders of Abrolhos inner-shelf reefs since the Pleistocene. No clear shallowing upward sequence of reef builders was observed, which differs from other reef sequences all over the world. In terms of Holocene reef growth, Pedra Grande and Coroa Vermelha reefs turned on roughly coevally at different depths and with different coral assemblages. Pedra Grande reef started growing circa 6.8 kyr BP in a water depth approximately 10 m deeper than Coroa Vermelha, which started growing around 6.4 kyr BP, but Coroa Vermelha turned off at around 4 kyr BP, while Pedra Grande kept growing until around 1.2 kyr BP. This novel reef stratigraphy data provided a new insight on the evolution of the Abrolhos coastal reefs, showing that different environmental and topographic controls could have acted spatially in different ways. Coroa Vermelha reef seems to have started its growth as a result of a topographic high control. Pedra Grande reef seems to be connected to a broader submerged reef setting and started to grow in deeper water depths. The presence of three reef arcs in Abrolhos is proposed, including a submerged reef arc.

Pipeline Wall Thickness Assessment of Various Material Grades and Water Depths Using American and Norwegian Standards

Two standards that are widely used by many countries in designing offshore gas transmission pipelines are American Standard – ASME B31.8, Gas Transmission and Distribution Piping Systems and Norwegian Standard – DNVGL-ST-F101, Submarine Pipeline System. A thorough understanding of these standards is vital in determining optimal pipeline design to ensure pipeline integrity for safe and sustainable operations, as well as striving for economic efficiency. This study aims to evaluate the wall thickness required for pipeline designs using American and Norwegian pipeline standards under different steel grades and water depth conditions. Pipeline costs are then compared for both standards at each water depth condition for commercial evaluation. Through this, the optimal pipeline standard for wall thickness design can be determined. Mathcad software was used for data analysis in accordance with the standards mentioned and all design requirements including pressure containment, collapse, and propagation buckling. Ultimately, the American Standards was able to provide a total cost that was 2.5% lower than the Norwegian Standard for a pipeline project with a combination of shallow, medium, and deepwater depths along its route. However, a combination of Norwegian Standards for medium and deepwater depths and American Standard for shallow water depth can further reduce total costs to 2% compared to only using the American Standard. This study highlights the importance of considering several design standards for a pipeline project instead of strictly adhering to a single standard for better technical and commercial benefit.