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The Carbonate Compensation Depth (CCD) refers to the depth within the ocean where the production and dissolution rates of carbonates reach equilibrium, widely likened to the oceanic calcareous 'snowline'. The reconstruction of deep-time CCD has significant implications for understanding ocean circulation, seawater chemical conditions, sediment distribution, and the surface carbon cycle. This paper critically reviews the methods for CCD reconstruction, summarizes the driving mechanisms of the Cenozoic CCD evolution and its association with the carbon cycle, and offers insights into future directions for CCD research. CCD reconstruction has evolved over the past half century from early qualitative to quantitative methods. These methodological improvements have markedly improved the accuracy and resolution of CCD. Existing studies have indicated a general trend of the CCD deepening across major ocean basins since the Cenozoic, interspersed with a minor shallowing phase during the mid-Miocene. The variations in the CCD are primarily influenced by factors such as ocean productivity, weathering, and shelf-basin partitioning. During climate events such as the Paleocene-Eocene Thermal Maximum, the CCD exhibits pulselike fluctuations. Future research should focus on precision and quantification while integrating model simulations to further explore the correlations and response mechanisms between the CCD and the paleoclimate as well as the carbon cycle. [ABSTRACT FROM AUTHOR]

In this paper, the exact explicit traveling wave solutions to the simplified modified Camassa–Holm (SMCH) equation. The SMCH equation is a significant nonlinear evolution equation because it can be used to describe certain physical processes in oceanography and fluid dynamics. The SMCH equation has important applications in mathematics, physics, and engineering. Using the modified auxiliary equation method and the extended G ′ G 2 -expansion method, we achieve precise solutions with traveling wave behavior. The proposed methods are applied for the first time in this work to examine the considered mathematical model. The solutions are extracted in terms of trigonometric, hyperbolic, and rational functions. The obtained results not only confirm the previously reported solutions of SMCH equation but also offer some new results. To clearly illustrate the physical implications of the examined equation, we provide graphical representations using 3D, 2D and contour plots for certain values of the parameters. The illustrations help to clarify the diverse characteristics and behaviors, associated with the solutions, providing useful insights for researchers as well as practitioners across a variety of scientific and technical disciplines. [ABSTRACT FROM AUTHOR]

Quantitative data on cephalopods collected in ten multidisciplinary surveys (20–2000 m) between 2004 and 2012, together with original oceanographic and satellite data, were analyzed using multivariate techniques. Statistical analyses were based on presence–absence matrices by species and hydrological variable indices. The results show that cephalopods are distributed in two main zoogeographical groups separated by latitude: "Temperate water" and "Tropical water" clusters. They extended by temperate and tropical regions, separated by a geographical boundary, Cape Blanc, particularly strong in the case of coastal species between these groups. For the total fauna, we have identified a third particular cephalopods' cluster, the "Upwelling" cluster (22°–17°N), characterized by a higher diversity and dominance of oceanic cephalopods. This is proposed as a new zoogeographical region that would coincide with the area of greatest productivity, intensity and permanence throughout the year of the canary current upwelling, confined between the north of Cape Blanc and the south of Mauritania. The results confirm the strong relationship between the three zoogeographical regions (temperate, tropical, and upwelling) and certain water bodies that characterize the regional hydrology. This paper deepens into the zoogeography of the cephalopods from Northwest Africa (Central-Eastern Atlantic), providing a new, more detailed insight into the region and its boundaries in relation to the oceanography. [ABSTRACT FROM AUTHOR]

Sub-mesoscale and mesoscale (i.e., 1–10 km and 10–200 km, respectively) ocean processes are highly relevant for the understanding of global circulation, mixing of water masses and energy exchange between ocean layers. However, the processes happening at these scales are hard to be characterized using direct measurements of temperature and salinity. Direct measurements are obtained from vertical probes and/or autonomous vehicles, which, despite their high vertical resolution, are sparsely located in space and therefore unable to capture spatial details at these scales. Seismic oceanography (SO) data have been successfully used to imaging and characterize the ocean at these spatial scales. These data represent indirect measurements of the ocean temperature and salinity along kilometric transects with high horizontal resolution (i.e., a near-synaptic view of the system under investigation), but lower vertical resolution when compared with direct observations. Despite its complex oceanographic setting, the Madeira Abyssal Plain is still largely uncharacterized due to the lack of direct observations. We show for the first time a comprehensive processing, modelling and interpretation of three 2-D seismic oceanography sections from this region. The data show coherent seismic reflection in space, depth and time and shed light into this oceanographic setting with an unprecedent horizontal resolution. The SO modelling and interpretation are combined with existing direct measurements and a quantitative method to correlate thermohaline staircases interpreted from conductivity-temperature-depth casts and seismic reflections is proposed. The results show the relatively stable presence of thermohaline staircases in simultaneously time and space between 1200 and 2000 m of water depth and their spatial variability and contribute to the generalization of SO in physical oceanography. [ABSTRACT FROM AUTHOR]

An adequate description of the interaction between the atmosphere and ocean remains one of the most important problems of modern oceanology and climatology. The extremely wide variety of physical processes occurring in the coupled layers, large range of scales, and moving boundary all significantly complicate the creation of models that would allow calculating the physical characteristics in both media with the necessary accuracy. In this paper the temporal variability of dynamic parameters in the driving layer of the atmosphere and in the near-surface layer of the sea on small and submesoscales from one to several tens of hours is considered. The experimental data show a very high correlation between the friction wind velocity and turbulence intensity in the upper sea layer on all scales recorded. One important distinguishing feature of all measured physical quantities in both media is the presence of quasi-periodic oscillations with different periods. For a more accurate description of momentum and energy fluxes from the atmosphere, a nonstationary model of turbulent exchange in the near-surface layer of the sea is proposed. It takes into account quasi-periodicity in the intensity of dynamic interaction between the atmosphere and the sea at these scales. In the model we use the equations of momentum and turbulent energy balance, the system of equations is solved numerically, and the calculation results are compared with other models and with experimental data. It is shown that taking into account the nonstationarity of the wind strain improves the correspondence between the calculations and the experimental data. It is noted that, in the nonstationary case, the energy and momentum flux from the atmosphere and the turbulence intensity increases compared to the action of a constant average wind of the same duration. Therefore, the strong averaging often used in global models may markedly underestimate the intensity of the dynamic interaction between the atmosphere and ocean. [ABSTRACT FROM AUTHOR]

The article describes the design and operational principles of the MDS-II bottom multimodem station, located in the coastal zone (depth of location 25 m) of the northeastern Black Sea at the Gelendzhik test site of the Shirshov Institute of Oceanology, Russian Academy of Sciences. The station is connected to the coastal center by a bottom fiber optic cable, through which power is supplied to the station, and online transmission of measurement data takes place. The station is an underwater server to which one can connect a measuring device and get a real-time access to it, as well as remotely control on its operation. The design of an automatic stationary station for vertical sounding (SSVS) of the water column, which is also used at the Gelendzhik test site, is described as well. This station is moored close to the MDS-II multimodem station and is connected to one of its modems. The station consists of a bottom electric winch installed on the seabed and a floating module (probe) on a cable line wound around the winch drum. When the command "sounding" is given, the cable unwinds and the floating module, equipped with temperature and pressure sensors, floats and measures the water temperature profile from the bottom layer to the sea surface. Then the cable is wound on a drum, and the floating module returns to the bottom layer. A prototype of a new SSVS is being developed, which will allow sounding of the water layer with a thickness of up to 100 m. It will be equipped with a multiparameter probe that makes joint measurements of hydrophysical and biooptical parameters. [ABSTRACT FROM AUTHOR]

Shallow water waves are seen in oceanography, atmospheric science, and other fields. In this paper, we investigate an extended (3+1)-dimensional shallow water wave equation. We get the travelling-wave solutions via the polynomial-expansion method. Applying the Hirota method and symbolic computation, we derive some mixed-lump-kink and mixed-rogue-wave-kink solutions. Based on the mixed-lump-kink solutions, we graphically show the interaction between a lump and a kink soliton, and find two different cases: (1) the lump merges into the kink soliton; (2) the lump separates from the kink soliton. Based on the mixed-rogue-wave-kink solutions, we graphically analyze the interaction between the rogue wave and two-kink solitons, and find that the rogue wave emerges from the one kink soliton and merges into the other kink soliton. [ABSTRACT FROM AUTHOR]

Due to the scarcity of simultaneous observations on global-scale wind and wave spectra, there has been limited research on the characteristics of global wave-induced stress and wind stress with wave effects using observed wave spectra, particularly their seasonal variations. The China France Oceanography Satellite (CFOSAT) for the first time can simultaneously observe global sea surface wind and wave spectra, providing a solid data basis for investigating this difficult issue. In this study, the seasonal characteristics of global sea surface wave-induced stress and wind stress were analyzed by combining one-year simultaneous wind and wave observations from CFOSAT with a wave boundary layer model. Wave-induced stress was divided into wind-wave-induced stress and swell-induced stress based on different wave forms. The results showed that the wave-induced stress presented a significant inverse correlation with swell index. A higher swell index corresponded to a larger proportion of swell-induced stress, resulting in a decrease in wind stress, and vice versa, wind-wave-induced stress was dominant, resulting in an increase in wind stress. From spring to winter in the Northern Hemisphere (NH), wind-wave-induced stress predominated in the westerly belt of the Southern Hemisphere (SH), while swell-induced stress predominated near the equator. Further analysis revealed that the seasonal variation in wind-wave-induced stress in the SH was not significant, however, wind-wave-induced stress during the boreal summer was significantly lower than that in other seasons. The absolute value of swell-induced stress in the SH showed a trend of decrease and then increase from spring to winter. The percentage of increase or decrease in wind stress after considering the wave-induced stress showed a roughly symmetrical pattern between the NH and SH during the spring and autumn seasons, while the summer and winter seasons showed an asymmetrical feature. Wave-induced stress significantly modulated wind stress, resulting in zonal mean variations by up to ±30%. This finding further highlights the important modulation of surface waves on wind stress at the global scale. [ABSTRACT FROM AUTHOR]

The results of seismoacoustic studies carried out in the years 2020–2023 on the shelf of southeastern Crimea by employees of the Shirshov Institute of Oceanology, Russian Academy of Sciences, using an original complex of technical means, including seismoacoustic and acoustic profilers are discussed. The data obtained made it possible to clarify the position of the paleo valleys and to provide a seismostratigraphic reference of the reflecting horizons with the identification of the main seismic complexes in the Pleistocene–Holocene part of the section. Seismic facies analysis of the wave field made it possible to clarify the paleogeographic conditions for the formation of paleo valleys. [ABSTRACT FROM AUTHOR]

Visible spectral radiometric measurements from space, commonly referred to as ocean-colour measurements, provide a rich stream of information on ocean biota as well as on biological and ecosystem processes. The strength of the ocean-colour technology for observing marine life lies in its global reach, combined with its ability to sample the field at a variety of spatial and temporal scales that match the scales of the processes themselves. Another advantage lies in the growing length of the time series of ocean-colour-derived products, enabiling investigations into any long-term changes, if present. This paper presents an overview of the principles and applications of ocean-colour data. The concentration of chlorophyll-a, the major pigment present in phytoplankton–single-celled, free-floating plants that are present in the sunlit layers of the ocean–was the first, and remains the most common, biological variable derived from ocean-colour data. Over the years, the list of ocean-colour products have grown to encompass many measures of the marine ecosystem and its functions, including primary production, phenology and ecosystem structure. Applications that exploit the data are many and varied, and include ecosystem-based fisheries management, biogeochemical cycles in the ocean, ecosystem health and climate change. An integrated approach, incorporating other modes of ocean observations and models with satellite observations, is needed to investigate the mysteries of the marine ecosystem. [ABSTRACT FROM AUTHOR]

Sathyendranath et al. ([11]) present an overview of ocean color data principles and applications, and describe how ocean color technology's strength lies in its global coverage and capability to sample the ocean biota at various spatial and temporal scales, matching the scales of the processes acting. Observations made from space comprise a fundamental component of the global observing system, contributing to a better understanding of the Earth system as a whole and its evolution, including climate and global environmental changes, under both natural and anthropogenic forcing factors. Ecosystem-based fisheries management, ocean biogeochemical cycles, ecosystem health and climate change studies utilize these data. [Extracted from the article]

This paper reviews the recent progress in our estimation of ocean dynamic topography and the derived surface geostrophic currents, mainly based on multiple nadir radar altimeter missions. These altimetric observations provide the cornerstone of our ocean circulation observing system from space. The largest signal in sea surface topography is from the mean surface dominated by the marine geoid, and we will discuss recent progress in observing the mean ocean circulation from altimetry, once the geoid and other corrections have been estimated and removed. We then address the recent advances in our observations of the large-scale and mesoscale ocean circulation from space, and the particular challenges and opportunities for new observations in the polar regions. The active research in the ocean barotropic tides and internal tidal circulation is also presented. The paper also addresses how our networks of global multi-satellite and in situ observations are being combined and assimilated to characterize the four-dimensional ocean circulation, for climate research and ocean forecasting systems. For the future of ocean circulation from space, the need for continuity of our current observing system is crucial, and we discuss the exciting enhancement to come with global wide-swath altimetry, the extension into the coastal and high-latitude regions, and proposals for direct total surface current satellites in the 2030 period. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to numerically demonstrate and comparatively analyze the critically strong and ambiguous impact of the a priori uncertainty of a shallow sea waveguide model in its main physical parameters on the output performance of model-based methods for spatial processing of multimode signals received by a vertical antenna array. The scenario is specified when a relatively weak signal of a remote underwater source is received against the background of intensive interference excited by a subsurface source (like a ship, for example) and ambient sea noise excited by wind waves. The considered array processing methods include matched-signal processing, optimal processing of the signal on the background of interference and noise, and suboptimal processing based on matched-mode array filtering of one of the signal-carrying modes with adaptive selection of its number. Quantitative estimates are obtained from above for the environment uncertainties, or model errors, with respect to the sound velocity in the water column and geoacoustic parameters of the underlying bottom, at which the array gain loss does not exceed a given level. It is shown that such estimates are very different both for different environmental parameters and for processing methods, with the determining role played by the conditions of useful signal reception, namely, the modal composition and intensity levels of the interference and sea noise at the array input. The problem statement and results are considered to be useful to detail the requirements for operational oceanography tools designed to support the effective operation of sonar antenna systems in real sea environments. [ABSTRACT FROM AUTHOR]

This work involves theoretical and numerical analysis of the thermal quasi-geostrophic (TQG) model of submesoscale geophysical fluid dynamics (GFD). Physically, the TQG model involves thermal geostrophic balance, in which the Rossby number, the Froude number and the stratification parameter are all of the same asymptotic order. The main analytical contribution of this paper is to construct local-in-time unique strong solutions for the TQG model. For this, we show that solutions of its regularised version α -TQG converge to solutions of TQG as its smoothing parameter α → 0 and we obtain blow-up criteria for the α -TQG model. The main contribution of the computational analysis is to verify the rate of convergence of α -TQG solutions to TQG solutions as α → 0 , for example, simulations in appropriate GFD regimes. [ABSTRACT FROM AUTHOR]

The use of towed underwater unmanned vehicles equipped with photo, video, and sonar systems has proven its effectiveness in studying the seafloor surface in integrated research of the World Ocean. This class of devices solves a wide range of tasks, including biological studies of benthic fauna and surveys of underwater technogenic objects. The towed vehicle "Videomodule" was developed at the Shirshov Institute of Oceanology, Russian Academy of Sciences, and has been successfully employed for such surveys for several years. The paper discusses the technical features and application issues of working with the "Videomodule." [ABSTRACT FROM AUTHOR]

Reanalysis datasets have been widely used in oceanography and climate change studies. We evaluate the applicability of eight reanalysis datasets in the Yellow and Bohai seas (YBS), including ERA5, SODA3.4.2, GREPv2, C-GLORSv7, GLORYS2v4, ORAS5, CORAv1.0, and CORAv2.0, compared to the observation data from the oceanic stations and an observation-based dataset of global instantaneous 3D thermohaline fields (ARMOR3D). The results show that the sea surface temperature (SST) of ERA5, ORAS5, and GREPv2 agrees with the observations, while the temperature profiles of C-GLORSv7 and GREPv2 are in good agreement with the ARMOR3D observation. In terms of ocean salinity, the salinity profile of the CORA series is in better agreement than other reanalysis datasets. Overall, GREPv2 is more consistent with seawater temperature observations in the YBS than others, while the CORA series reproduces the salinity variation better. GREPv2, a multi-model ensemble product, delivers a better depiction of seawater temperature and salinity than that of the individual member dataset. Most reanalysis datasets can reproduce the interannual variation of SST in the YBS well with improved performance in the last decade. The spatial distribution differences occur mostly in offshore waters with a warmer but less salinity bias. [ABSTRACT FROM AUTHOR]

Benthodytes tetrapapillata sp. nov. was collected from a seamount located on the Caroline Ridge at a depth of 2 289 m, during the cruise of R/V Kexue in June 2019. We provided detailed descriptions of external and deposits morphology. The phylogenetic analyses based on cytochrome c oxidase I (COI) and a concatenated dataset of 16S and COI genes showed that the new species belonged to Benthodytes that is not monophyletic. Both details of morphological comparisons and molecular analyses confirmed that Benthodytes tetrapapillata sp. nov. is a new psychropotid species. A state of main morphological characters in valid species of Benthodytes is also provided in this study. [ABSTRACT FROM AUTHOR]

Accurate species identification is a key component of biodiversity research. DNA barcoding is an effective molecular method used for fish species identification. We aimed to study the DNA barcoding of fish in Zhoushan coastal waters, explore the differences and applicability of two gene fragments (12S rRNA and COI) of DNA barcoding in fish species identification, and established a comprehensive fish barcoding reference database. Two hundred and eighty-seven captured fish samples from Zhoushan coastal waters were identified using morphological characteristics and DNA barcoding. A total of 264 12S rRNA sequences (belonging to eight orders, 31 families, 55 genera, and 66 species) and 188 COI sequences (belonging to seven orders, 30 families, 48 genera, and 58 species) were obtained. The lengths of the 12S rRNA sequences ranged from 165 to 178 bp, and the guanine-cytosine (GC) content was 45.37%. The average 12S rRNA interspecific and intraspecific genetic distances (K2P) were 0.10% and 26.66%, respectively. The length of the COI sequence ranged 574–655 bp, and the content of GC was 45.97%. The average 12S rRNA interspecific and intraspecific genetic distances (K2P) were 0.16% and 27.45%, respectively. The minimum interspecific genetic distances of 12S rRNA and COI (1.23% and 1.86%) were both greater than their maximum intraspecific genetic distances (2.42% and 8.66%). Three molecular analyses (NJ tree, ABGD, and GMYC) were performed to accurately identify and delineate species. Clustering errors occurred when the 12S rRNA sequences were delimited using the NJ tree method, and the delimitation results of ABGD and GMYC are consistent with the final species identification results. Our results demonstrate that DNA barcoding based on 12S rRNA and COI can be used as an effective tool for fish species identification, and 12S rRNA has good application prospects in the environmental DNA (eDNA) metabarcoding of marine fish. [ABSTRACT FROM AUTHOR]

Ocean salinity is an important variable that affects the ocean stratification. We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo (Array for Real-time Geostrophic Oceanography data), EN4 (Ensemble 4 analysis), SODA (the Simple Ocean Data Assimilation reanalysis), IAP (Institute of Atmospheric Physics data), and ORAS4 (Ocean Reanalysis System 4) over 2005–2017. Results show that the spatial distribution of climatological mean of sea surface salinity (SSS) in all the products is consistent, and the low salinity region showed large deviation and strong dispersion. The Argo has the smallest RMSE and the highest correlation with the ensemble mean, while the IAP shows a high-salinity deviations relative to other datasets. All the products show high positive correlations between the sea surface density (SSD) and SSS with respect to the deviations of climatological mean from ensemble mean, suggesting that the SSD deviation may be mainly influenced by the SSS deviation. In the aspect of the ocean stratification, the mixed layer depth (MLD) climatological mean in the Argo shows the highest correlation with the ensemble mean, followed by EN4, IAP, ORAS4, and SODA. The Argo and EN4 show thicker barrier layer (BL) relative to the ensemble mean while the SODA displays the largest negative deviation in the tropical western Pacific. Furthermore, the EN4, ORAS4, and IAP underestimate the stability in the upper ocean at the depths of 20–140 m, while Argo overestimates ocean stability. The salinity fronts in the western-central equatorial Pacific from Argo, EN4, and ORAS4 are consistent, while those from SODA and IAP show large deviations with a westward position in amplitude of 0°–6° and 0°–10°, respectively. The SSS trend patterns from all the products are consistent in having ensemble mean with high spatial correlations of 0.95–0.97. [ABSTRACT FROM AUTHOR]

This is the first high-resolution seismic study showing how the Chicxulub impact shaped the eastern slope of the Campeche Bank in the south-eastern Gulf of Mexico. The induced shock wave fractured Cretaceous strata causing the collapse of the upper slope and shelf over a length of ca. 200 km. Failed material was either transported downslope or remained in parts on the accommodation space created by the collapsed. In the Cenozoic, the East Campeche Plastered Drift developed within the created accommodation space, controlled by the inflowing surface current from the Caribbean, which forms the Loop Current. The internal reflection configuration of the drift shows that the closure of the Suwannee Strait in the Late Oligocene and the closure of the CAS in the Mid to Late Miocene controlled the variability of the southern Loop Current in time. Since the Loop Current transports heat and moisture from the western Atlantic warm water pool into the North Atlantic and further to NW Europe by the Gulf Stream, the drift represents an archive for controlling factors that influenced climate of the northern hemisphere. This first high-resolution seismic reflection study from the eastern Campeche Bank expands the understanding of destructive processes that a meteorite impact induces into the earth system. Furthermore, these data document that the East Campeche Plastered Drift bears the potential to understand the link between the climate variability of the northern hemisphere and oceanic processes in the equatorial western Atlantic. [ABSTRACT FROM AUTHOR]

Results of numerical experiments on the assimilation of in situ temperature and salinity profiles observed in the region of Drake Passage (the South Atlantic) during the expedition of Shirshov Institute of Oceanology of Russian Academy of Sciences (RAS) in the autumn of 2011 into the INMOM model developed by Marchuk Institute of Numerical Mathematics of RAS are considered. The previously developed method of assimilation presented in several publications is used. As a result of some experiments, it has been shown that the structure of the anticyclonic circulation associated with the Brazil-Malvinas Confluence in the area of the Argentine Basin has been mostly affected by the expedition data assimilation. Assimilated fields of ocean temperature on the surface and at various horizons show better agreement with reanalysis data than corresponding fields without assimilation. It is also demonstrated that the influence of assimilation spreads much further beyond the local area of observations and leads to changing all calculated characteristics (not only observed ones). [ABSTRACT FROM AUTHOR]

The article presents brief results of expeditionary studies of the Southeastern Baltic Sea and eastern Gulf of Finland during cruise 53 of the R/V Akademik Boris Petrov (2023). The expedition was a continuation of longstanding oceanological research conducted by the Atlantic Branch of the Shirshov Institute of Oceanology, Russian Academy of Sciences. Integrated geological, geophysical, hydrological, hydrochemical, hydrobiological, and geoecological research was carried out. New data on the state and dynamic of natural systems of the Baltic Sea were obtained. [ABSTRACT FROM AUTHOR]

A new gravity sensor based on electromagnetic damping for the JMGrav marine gravimeter is presented. The new gravity sensor considered the advanced construction methods of the electromagnetic damping system of the gravimeter. The design features of the new system are discussed and the research survey data in the South China Sea are shown. Numerical simulations are applied to model the magnetic and mechanical characteristics of the system using finite element analysis and to evaluate the force distribution and the resulting damping effects. The performance characteristics of the system were tested on a motion simulator in laboratory, and the gravimeter was subjected to vertical accelerations of up to 100 Gal in 1–1 000 s. It was found that the amplitude reduction of vertical accelerations in 3–15 s is 30–45 dB, with a time lag of 2–5 s, while the effect on gravity in period greater than 600 s is less than 0.5 dB, with a time lag of less than 100 s. The accelerations cause discrepancies of approximately only 1 mGal between the static value and the mean dynamic value. The sea tests were conducted in September 2020. Gravity measurements were taken with a JMGrav marine gravimeter onboard the R/V Dongfanghong 3, and the effective survey line exceeded 2 000 km. Completely irregular accelerations with peaks up to 100 Gal yielded a reduction of approximately 40 dB in amplitude. The survey data were evaluated using ocean gravity field models and grid line tests. The results show that the accuracy of the gravity measurements is better than 2 mGal. [ABSTRACT FROM AUTHOR]

Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure gradient. When detected using acoustic data, the leaked gases frequently exhibit a flame-like structure. We numerically modelled the relationship between the seismic response characteristic and bubble volume fraction to establish the bubble volume fraction in the submarine seep plume. Results show that our models are able to invert and predict the bubble volume fraction from field seismic oceanography data, by which synthetic seismic sections in different dominant frequencies could be numerically simulated, seismic attribute sections (e.g., instantaneous amplitude, instantaneous frequency, and instantaneous phase) extracted, and the correlation between the seismic attributes and bubble volume fraction be quantitatively determined with functional equations. The instantaneous amplitude is positively correlated with bubble volume fraction, while the instantaneous frequency and bubble volume fraction are negatively correlated. In addition, information entropy is introduced as a proxy to quantify the relationship between the instantaneous phase and bubble volume fraction. As the bubble volume fraction increases, the information entropy of the instantaneous phase increases rapidly at the beginning, followed by a slight upward trend, and finally stabilizes. Therefore, under optimal noise conditions, the bubble volume fraction of submarine seep plumes can be inverted and predicted based on seismic response characteristics in terms of seismic attributes. [ABSTRACT FROM AUTHOR]

The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography, Ministry of Natural Resources (FIO, MNR). The system is mainly composed of a plasma spark source (source level: 216 dB, main frequency: 750 Hz, frequency bandwidth: 150–1 200 Hz) and a towed hydrophone streamer with 48 channels. Because the source and the towed hydrophone streamer are constantly moving according to the towing configuration, the accurate positioning of the towing hydrophone array and the moveout correction of deep-towed multichannel seismic data processing before imaging are challenging. Initially, according to the characteristics of the system and the towing streamer shape in deep water, travel-time positioning method was used to construct the hydrophone streamer shape, and the results were corrected by using the polynomial curve fitting method. Then, a new data-processing workflow for Kuiyang-ST2000 system data was introduced, mainly including float datum setting, residual static correction, phase-based moveout correction, which allows the imaging algorithms of conventional marine seismic data processing to extend to deep-towed seismic data. We successfully applied the Kuiyang-ST2000 system and methodology of data processing to a gas hydrate survey of the Qiongdongnan and Shenhu areas in the South China Sea, and the results show that the profile has very high vertical and lateral resolutions (0.5 m and 8 m, respectively), which can provide full and accurate details of gas hydrate-related and geohazard sedimentary and structural features in the South China Sea. [ABSTRACT FROM AUTHOR]

Based on the materials of 20 expeditions conducted by the Shirshov Institute of Oceanology (IO RAS) in various areas of the coastal zone of the Russian sector of the Black Sea from 1999 to 2021, empirical equations of the relationship between the relative transparency (Secchi depth, Zd) and mass concentrations of the total suspended particulate (SPM), suspended mineral (SMM), and suspended organic matter (SOM) fractions (Cspm, Csmm, and Csom, respectively) were obtained. The Zd values were recorded in the range from 0.1 to 21 m; SMM concentrations, from 0.11 to 104 mg/L; SOM, from 0.09 to 2.0 mg/L; and chlorophyll a (Ca), from 0.03 to 4.4 µm/L. The relative abundance of SOM in SPM ranged from 1.1 to 48.7%. The calculation error for these equations is estimated. The determination coefficients r2 = 0.85 (for logCspm and logCsmm) and 0.72 (for logCsom). The influence of the SOM concentration on the accuracy in calculating Ssmm and chlorophyll a concentration on the accuracy in calculating Csom was revealed. It is concluded the empirical formulas can be used with respect to the entire dataset to calculate the concentrations of these SPM fractions in the entire studied water area. It is proposed to consider the method for estimating the content of SPM fractions using the obtained empirical equations as a regional variant of passive sounding of the upper layer of the sea with a Secchi disk. [ABSTRACT FROM AUTHOR]

Satellite records show that the extent and thickness of sea ice in the Arctic Ocean have significantly decreased since the early 1970s. The prediction of sea ice is highly important, but accurate simulation of sea ice variations remains highly challenging. For improving model performance, sensitivity experiments were conducted using the coupled ocean and sea ice model (NEMO-LIM), and the simulation results were compared against satellite observations. Moreover, the contribution ratios of dynamic and thermodynamic processes to sea ice variations were analyzed. The results show that the performance of the model in reconstructing the spatial distribution of Arctic sea ice is highly sensitive to ice strength decay constant (Crhg). By reducing the Crhg constant, the sea ice compressive strength increases, leading to improved simulated sea ice states. The contribution of thermodynamic processes to sea ice melting was reduced due to less deformation and fracture of sea ice with increased compressive strength. Meanwhile, dynamic processes constrained more sea ice to the central Arctic Ocean and contributed to the increases in ice concentration, reducing the simulation bias in the central Arctic Ocean in summer. The root mean square error (RMSE) between modeled and the CryoSat-2/SMOS satellite observed ice thickness was reduced in the compressive strength-enhanced model solution. The ice thickness, especially of multiyear thick ice, was also reduced and matched with the satellite observation better in the freezing season. These provide an essential foundation on exploring the response of the marine ecosystem and biogeochemical cycling to sea ice changes. [ABSTRACT FROM AUTHOR]

Forecasting oceanographic parameters is an essential aspect in determining future climatology which is a rising interest in ocean-related fields. The existing traditional algorithms forecasts the problems related to Sea Surface Temperature (SST) but not the other ocean parameters. In this paper, Heuristic Neural Network (HNN) model is proposed to predict the future climate with better efficiency using Particle Swarm Optimization (PSO) at three different locations- Arctic Ocean, Bay of Bengal and Indian Ocean. The ocean forecasting parameters include the horizontal and vertical conditions with spatial and temporal distributions at 2000 m by the data obtained from Array for Real-Time Geostrophic Oceanography (ARGO) under the Ministry of earth sciences. The proposed HNN model uses the received information from the past to predict the future climate without consuming the energy of the sensor nodes by transceiving the beacons. The simulated HNN outcomes proves best among other neural networks with the average accuracy of 98% for each ocean which serves good for Climate prediction. [ABSTRACT FROM AUTHOR]

During polar nights of 2012 and 2017, bioluminescence (BL) potential surveys demonstrated high emissions at depths around and below 100 m at offshore stations to the north of a Svalbard fjord (Rijpfjorden). We demonstrated that the highest bioluminescent emissions for offshore stations are located at depths below depths of modelled/ambient light intensities corresponding to the reported irradiance thresholds for the behavioral light sensitivity of krill and copepods, and suggest that behavioral light sensitivity is one of the reasons for high values of BL potential observed below 100 m at offshore stations. In order to understand sources of bioluminescent taxa responsible for the observed high values of BL potential in offshore waters, we have investigated the origin and pathways of water masses circulating to the north, offshore of the fjord Rijpfjorden by using a hydrodynamic model. For both 2012 and 2017, the model water masses mostly originate from the west, where the Atlantic water is flowing northward, then along the shelf and shelf slope of northern Svalbard, and to the offshore of the fjord. This indicates that the advection of zooplankton by North Atlantic Water is one possible source of bioluminescent organisms offshore of northern Svalbard. In 2012, water masses also originated from the inflow through Hinlopen trench and strait, while, in 2017, the offshore water was advected and upwelled into the fjord on time scales less than 10 days, and after that there was a recirculation back from the fjord to offshore on time scales larger than 10 days. This recirculation from the fjord might be another source of bioluminescent organisms in the offshore waters. [ABSTRACT FROM AUTHOR]

The marine and coastal environment of West Africa provide several resources and potential benefits to its people much as it presents numerous challenges and dangers that need to be addressed for sustainable exploitation of such resources. The need for projection of ocean waves is paramount to providing information for several purposes, including safety at sea and design of marine and coastal structures. Ocean wave projections in the region is still however in its infant stages. Increasing levels of developments and reliance on the marine and coastal environment of West Africa presents an opportunity for the development of regional wave parameterization physics or schemes that will provide accurate and more reliable ocean wave and sea state products and information for decision making that contributes to blue growth and the general Blue Economy agenda of the region. This review provides a general information on the diverse nature of the West Africa marine and coastal environment with respect to its oceanography, climate and meteorology, as well as studies related to general ocean wave projections and related issues. This is aimed at raising awareness on the need to investigate the appropriate ocean wave parameterization schemes for accurate projection of wave properties in the West Africa Region. [ABSTRACT FROM AUTHOR]

A distribution analysis of scleractinian coral species in the Pacific Ocean using the data of the Shirshov Institute of Oceanology and literature data was carried out with regards to the global ocean conveyor belt. The idea was to evaluate if the Conveyor acts as a natural barrier for hydranth larva. Series of maps of scleractinian coral distribution in depths intervals of 1000–2000, 2000–3000, 3000–4000, and 4000–5000 m were created in order to study the characteristics of their distribution in the Pacific Ocean. The majority of stations (up to 300) with corals were registered in the depth range of 1000–2000 m. A few stations are located in deeper regions. The second highest number of stations (more than 60) are located in abyss depths deeper than 4000 m. However, only three species are present in this depth range. The geographical distribution of scleractinian corals shows longitudinal asymmetry. The majority of the stations are located in the western part of the Pacific. We are suggesting that this distribution is associated with the global ocean conveyor belt and with the evolution of the ocean. The paleogeographic evaluation of the possible time period when the species first appeared shows that relatively shallow water (1000–2000 m) corral associations are older than the abyssal scleractinian fauna. This supplements the hypotheses that we made in [4] of the evolution of F. marenzelleri and L. discus [4]. [ABSTRACT FROM AUTHOR]

The main goal of the work is to study the spatiotemporal structure of sea currents in the shelf–slope zone of the northeastern part of the Black Sea. The studies were carried out by numerical simulation methods using the combined hydrodynamic and spectral wave models incorporated in the DHI MIKE computational complex. The model has been verified based on the data of field observations performed by means of the hydrophysical test site of the Institute of Oceanology, Russian Academy of Sciences (Gelendzhik test site). As a result of calculations with a discreteness of half an hour, the fields of velocities and directions of currents for the period from January 2016 to December 2020 were obtained. Despite the fact that the total length of the massif is insufficient for climatic generalizations, analysis of the data obtained from the numerical experiment makes it possible to judge some general features of the seasonal dynamics of waters. As a result of the work that was carried out, the features of current velocity fluctuations in the frequency domain were revealed, and, based on the averaged current fields, the main seasonal features of water circulation in the shelf zone of the northeastern Black Sea coast were estimated. [ABSTRACT FROM AUTHOR]

This paper briefly introduces the conception and research history of the Great Oxidation Event (GOE) in the early Paleoproterozoic and summarizes the primary geological and geochemical records of this event. On the basis of these, we overview the significant progress in three fields of the GOE: the timing and process of its startup, its mechanisms, and its climatic-ecological effects. The records of mass-independent fractionation of sulfur isotopes suggest that the startup of the GOE might be multi-episodic, which is obviously inconsistent with the single-episodic opinion obtained from atmospheric model simulations. The fundamental mechanism of the GOE was the source of the atmospheric O2 exceeding the sink, but it remains uncertain whether it was due to the increase in the source or the decrease in the sink. The GOE substantially affected the climate, biological evolution, and biogeochemical cycles, but the specific processes remain elusive. In consideration of the current progress, we propose four aspects for future explorations, including the construction of geological and geochemical proxies for extremely low atmospheric oxygen content (pO2), how the GOE changed the evolutions of Earth's habitability and the processes in deep Earth, and constraining the mechanism of the GOE by coupling geological events with different time scales. [ABSTRACT FROM AUTHOR]

This paper is based on a comparison of the carbon parameters at the western and eastern borders of the tropical Atlantic using data collected from 55 cruises. Oceanic and coastal data, mainly total alkalinity (TA), total dissolved inorganic carbon (CT), sea surface salinity (SSS) and sea surface temperature (SST), were compiled from different sources. These data were subdivided into three subsets: oceanic data, coastal data and adjacent to the Brazilian (western) and African coastal areas (eastern) data. Significant differences between the TA data (2099.4 ± 286.4 µmol kg−1) at the western and eastern edges (2198 ± 141.9 µmol kg−1) were observed. Differences in the CT values between the western edge (1779.6 ± 236.4 µmol kg−1) and eastern edge (1892.2 ± 94.2 µmol kg−1) were also noted. This pattern was due to the different variabilities in the carbon parameters between the eastern and western border coastal areas and to the biogeochemistry that drives these parameters. In the western coastal area, the physical features of the continental carbon and oceanic waters mixing with the freshwater that flows from the Amazon and Orinoco Rivers to the South American coast are different than the physical features of the water that flows from the Congo, Volta and Niger Rivers in the eastern region. Applying the TA empirical relationship to TA with values of SSS < 35 in the western and eastern regions leads to a higher root mean square error (rmse) in the eastern and western regions. Therefore, most of the existing TA empirical relationships are most useful at the regional scale due to the difference in the water properties of each region. The relationships of TA and CT determined in the western and eastern regions do not reproduce in situ data well, especially at the adjacent edges. This difference is explained by the difference between the African and Brazilian coasts in terms of their carbon parameter characteristics and processes responsible for their variation. Based on the mixing model, it has been shown that the primary productivity in the eastern region is higher than that in the western region. This is one of the reasons why the carbon parameters are higher in the eastern region. For each region studied, an equation for TA is introduced in this study. [ABSTRACT FROM AUTHOR]

The study considers the formulation of the problem and performs a numerical experiment for a short-term forecast of hydrological parameters using the data of two thermohaline surveys on September 14 and 16, 2019, at the test site of the Southern Branch of the Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS) at Gelendzhik. Due to the small spatial scale of the survey area (about 15 × 15 km), a forecast as a solution to the Cauchy problem is impossible due to the large time gap between surveys. Therefore, the authors attempted to solve the forecast problem using the technique of a priori nonadiabatic sources, reflecting the temporal variability of the sought characteristics contained in the field data of the first survey. Essentially, this technique assumes a persistent trend of temporal variability of hydrological processes during the transition to the second survey. In this case, the problem of forecasting with nonadiabatic sources is divided into two stages using a quasi-hyperbolic system of equations. At the first stage, the problem of analysis with assimilation of the first survey data is considered, in the solution of which the required nonadiabatic sources are found. At the second stage, the forecast problem is solved by calculating nonadiabatic a priori sources. Comparison of the forecast results with the data of the second survey in this case yields satisfactory results. [ABSTRACT FROM AUTHOR]

The present study analyzes the impact of the Southern Ocean (SO) sea ice concentration on the north Indian Ocean (NIO) wave fields through swells using 6 years (2016–2021) of WAVEWATCH III (WWIII) simulations. We did two experimental runs of WWIII, one with sea ice concentration and winds as the forcing (W3with_ice) and the second run with only wind forcing (W3no_ice). Analysis shows the impact of the SO sea ice concentration on northward swell peaks in September–November, coinciding with the maximum sea ice extent in the Antarctic region of the Indian Ocean. W3no_ice simulations are biased more by ~ 60% and ~ 37% in significant wave height and period, respectively, against W3with_ice when compared with NIO mooring data. W3no_ice simulates low-frequency swells and travels fast towards NIO, with implications for operational oceanography. We have shown that the forecasts of the timing of high swell events along NIO coasts can be erroneous by ~ 12 h if the SO sea ice concentration is not included in the model. Further, W3no_ice could potentially produce false swell alerts along southeastern Australian coasts. In summary, our study highlights the importance of the SO sea ice concentration inclusion in the wave models to accurately simulate NIO waves. [ABSTRACT FROM AUTHOR]

The Late Miocene global cooling (LMGC; approximately 7.9–5.8 Ma) was associated with remarkable changes in monsoon dynamics, biogenic bloom in the global oceans, and the rise of modern ecosystems at the expense of old biota. However, the possible linkage between the environmental changes and ecosystem shifts during the LMGC is still debated. In this paper, we show the high-resolution changes in the fluxes of selected radiolarian species, suggesting a drastic reorganization in the paleoceanography and ecosystem in the Japan Sea during the LMGC. The endemic radiolarian Cycladophora nakasekoi dominated the Japan Sea until 7.4 Ma when the Japan Sea sediment changed from dark radiolarian-rich sediment to organic-poor diatom ooze. Changes in the fluxes of C. nakasekoi and Tricolocapsa papillosa, the latter related to changes in the Pacific central water (PCW), show 100, 200, and ~ 500 ka cycles with their high flux mostly within the darker sediment intervals during the low-eccentricity period until 7.4 Ma, suggesting that orbitally paced PCW inflow might have been the major nutrient source into the Japan Sea. At about 7.4 Ma, these species decreased at the expense of increased Larcopyle weddellium, a radiolarian related to the North Pacific intermediate water (NPIW), and Cycladophora sphaeris, a subarctic radiolarian species, implying a decrease in PCW inflow and an increase in the inflow of NPIW and subarctic shallow water. Such a change would have been related to the LMGC-induced weakening in the Pacific Meridional overturning circulation and the southward shift of the subarctic front due to intensified East Asian winter monsoon. Such a drastic reorganization in the hydrography in the Japan Sea probably caused changes in nutrient provenance from the PCW to the NPIW and resulted in faunal turnover, marked by the disappearance of the old regional and endemic faunal components, such as C. nakasekoi. [ABSTRACT FROM AUTHOR]

Seamounts affect the surrounding physical oceanography and form unique dynamic processes. The influences of these processes on biological and sedimentary distributions are quite different in seamount areas at different depths. The Y3 seamount is located in the Yap Arc of the tropical Western Pacific Ocean. The water depth of its summit is ∼280 m. Based on field data obtained in December 2014 and other open-access data, the physical oceanography around the Y3 seamount was preliminarily analyzed. The results show that the upper layer (0–150 m) was under the influence of the westward-flowing North Equatorial Current (NEC), while the eastward-flowing North Equatorial Undercurrent (NEUC) controlled the water between 200–800 m. The NEC was strong and steady, but the NEUC was disturbed by the Y3 seamount. The cold dome above the Y3 seamount was not caused by a Taylor cap or tidal rectification but probably by upwelling during the survey time. Tidal currents were squeezed against topography and greatly amplified in the Y3 seamount. The thicknesses of the surface turbulent layers were greatly influenced by the spring-neap tidal cycle. The turbulent diffusivities in the sea surface layer above the Y3 seamount were much larger than those in the open ocean. Calculations showed that the surface wind stress greatly affected the turbulent mixing in the surface layer of the Y3 seamount. The reciprocal action between the amplified tidal currents and topography was the most likely cause of the turbulent mixing near the bottom of the Y3 seamount. This study can provide a scientific basis for further study of biological and depositional characteristics at the Y3 seamount. [ABSTRACT FROM AUTHOR]

Phytoplankton and biotoxin monitoring programmes have been implemented in many countries to protect human health and to mitigate the impacts of harmful algal blooms (HABs) on the aquaculture industry. Several amphidomatacean species have been confirmed in Irish coastal waters, including the azaspiracid-producing species Azadinium spinosum and Amphidoma languida. Biogeographic distribution studies have been hampered by the fact that these small, armoured dinoflagellates share remarkably similar morphologies when observed by light microscopy. The recent releases of species-specific molecular detection assays have, in this context, been welcome developments. A survey of the south west and west coasts of Ireland was carried out in August 2017 to investigate the late summer distribution of toxic amphidomataceans and azaspiracid toxins. Azadinium spinosum and Am. languida were detected in 83% of samples in the southwest along the Crease Line and Bantry Bay transects between 20 and 70 m depth, with maximal cell concentrations of 7000 and 470,000 cells/L, respectively. Azaspiracid concentrations were well aligned with the distributions of Az. spinosum and Am. languida, up to 1.1 ng/L and 4.9 ng/L for combined AZA-1, -2, -33, and combined AZA-38, -39, respectively. Although a snapshot in time, this survey provides new insights in the late summer prominence of AZAs and AZA-producing species in the southwest of Ireland, where major shellfish aquaculture operations are located. Results showed a substantial overlap in the distribution of amphidomatacean species in the area and provide valuable baseline information in the context of ongoing monitoring efforts of toxigenic amphidomataceans in the region. [ABSTRACT FROM AUTHOR]

The quality control (QC) of ocean observational data, essential to establish a high-quality global ocean database, is one of the basic data pre-processing steps in oceanography research, marine monitoring, and forecasting. With the introduction of various advanced instruments in recent decades, oceanographic surveys have expanded from coastal regions to open oceans. However, as ocean in-situ observations are obtained using different instruments that offer heterogeneous data qualities, it is paramount that bad data could be accurately and efficiently identified via QC to provide a reliable global ocean database. In this review, we briefly summarize the latest progress of QC for oceanic in-situ observations, and mainly focus on temperature and salinity data. The similarities and differences between QC schemes developed by various ocean organizations are introduced. We also discuss the performances of the various QC schemes and identify the key challenges. Based on the discussions, several recommendations are proposed for future improvements in the QC for ocean observations. [ABSTRACT FROM AUTHOR]

The article presents data indicating the relationship of the bathymetric distribution of solitary endemic scleractinian corals inhabiting the Antarctic continental shelf and upper continental slope with the vertical density of the Antarctic Circumpolar Current. The study is based on materials collected by expeditions of the Shirshov Institute of Oceanology (IO RAS) and the literature data. The results show that endemic species that appeared in the Late Neogene and Pleistocene were unable to propagate across other oceans due to the existing horizontal and vertical density of the Arctic Circumpolar Current during that period. [ABSTRACT FROM AUTHOR]

The article presents information on the current experiment of research on wind wave parameters in the Black Sea coastal zone. Two wave-meter devices are the part of the measuring equipment of the Black Sea testing site Gelendzhik of the Shirshov Institute of Oceanology (IO RAS). The integral characteristics of wind waves accumulated and obtained in real time may be in demand by experts in operational and satellite oceanography. [ABSTRACT FROM AUTHOR]

The Kerguelen Plateau in the south-eastern Indian Ocean is one of the most isolated and understudied regions on earth. As part of the Kerguelen Plateau Drifts project, Marine Mammal Observer (MMO) data were collected during a seismic survey in the austral summer (January–February 2020). Relationships between observation effort, cetacean sightings, seismic operations, and oceanographic variables—including bathymetry (depth and slope), nutrient concentrations, and indices of primary productivity—were investigated using Generalized Additive Models (GAMs). In total, 354 h and 45 min of observation effort resulted in 191 cetaceans (178 adults and at least 13 juveniles) of nine species observed on 48 occasions, over 14 days along the transect line. Marine mammal sightings occurred in water depths of 624–4699 m, with a hotspot of sightings recorded along the northern flank of the Kerguelen Plateau, in proximity to shelf edges. There was one sighting of a mixed pod of Kerguelen Commerson's dolphins (Cephalorhynchus commersonii kerguelenensis) and dusky dolphins (Lagenorhynchus obscurus), which to the best of our knowledge, is the first confirmed sighting of dusky dolphins in the Kerguelen Islands. Of the nine cetacean species observed, no niche separation was apparent, and all species were observed throughout the survey area. Dissolved oxygen and chlorophyll-a were the most significant predictors of cetacean occurrence. Systematic MMO data combined with synoptic satellite-derived/empirical oceanographic metadata have great potential to facilitate understanding of behaviour, geographical range, and population-status monitoring of cetaceans. This is especially important for cetacean stock assessment and minimising potential acoustic disturbance in Antarctic ecosystems. [ABSTRACT FROM AUTHOR]

During polar nights in January 2012 and 2017, significantly higher bioluminescence (BL) potential emissions in the upper 50 m were observed in the fjord Rijpfjorden (Svalbard, Norway) in comparison to offshore stations (located on the shelf-break, shelf-slope areas and in the deeper water). The objective of this paper is to better understand why, during two polar nights (separated by 5 years), the values of BL potential in the northern Svalbard fjord are higher than at offshore stations, and what the role of advection is in observed elevated BL potential values in the top 50 m of the fjord. To address the above objective, we applied the same BL potential modeling approach and strategies during polar nights for both 2012 and 2017. For both years, advection of BL potential from offshore (including upwelling along the shelf, shelf-slope) produced an increase of BL potential in the fjord area, in spite of the introduction of mortality in bioluminescent organisms. Observations of BL potential indicated high emissions at depths below 100 m at offshore stations for both polar nights. Our modeling studies demonstrated that these high values of BL potential below 100 m are upwelled and advected to the top 50 m of the fjord. We demonstrated that upwelling and advection of these deep high BL potential values (and therefore, upwelling and advection of corresponding bioluminescent taxa) from offshore areas are dominant factors in observed BL potential dynamics in the top 50 m in the fjord. [ABSTRACT FROM AUTHOR]

The Andaman Sea has been a classic study region for internal solitary waves (ISWs) for several decades, and extraordinarily large ISWs are characteristic of the Andaman Sea in the Indian Ocean. This paper presents results on the estimation of the propagation velocity of ISWs in the Andaman Sea that were tracked using 195 image pairs acquired by MODIS National Aeronautics and Space Administration (NASA) Terra/Aqua satellites between January 2014 and December 2018. A total of 562 ISWs were identified during the period, and the results of the propagation velocity distribution of ISWs in the Andaman Sea are presented. The estimated propagation velocity of ISWs agrees well with the theoretical results derived from the Korteweg-de Vries (KdV) equation using monthly climatology stratification data and local bathymetry. The ISW propagation velocity decreases as they propagate from deep to shallow water; the maximum propagation velocity of 3.27 m/s was estimated on the western side of the Nicobar Islands and minimum speed of 0.54 m/s occurred in the shallow water region of the southeastern Andaman Sea. The results show that the ISW propagation characteristics differ in the northern, central, and southern regions of the Andaman Sea. In the northern Andaman Sea, the velocity of ISWs propagating westward was greater than that of ISWs propagating eastward at the same water depth. In the central Andaman Sea, the propagation velocity of the ISWs differed over a small area at a depth of 2 500 m, and the velocity of ISWs in the deep mixing layer in winter was higher than that in the shallow mixing layer in spring. Monthly variations in ISW propagation velocity were analyzed in the southern Andaman Sea, and the velocity of ISWs differed greatly in shallow water and was not significantly different in deep water. Water depth and monthly stratification play vital roles in controlling the phase speed of ISWs in the Andaman Sea. This study will provide a basis for the propagation and prediction of ISWs in the Andaman Sea. [ABSTRACT FROM AUTHOR]

Sea surface wind (SSW) observations from a newly developed "Black Pearl" wave glider, the Chinese-French Oceanography Satellite (CFOSAT), the HY-2A microwave scatterometer, and a recently released high-resolution atmospheric reanalysis (ERA5) are evaluated with respect to in-situ buoy observations (115.46°E, 19.85°N) from the South China Sea. Buoy observations from June to November 2019 are used to evaluate the wind estimates from the different platforms. The comparisons show that the HY-2A and CFOSAT scatterometer wind speeds have mean root mean square errors (RMSEs) of approximately 1.6 and 1.6 m/s, respectively, and the corresponding mean wind direction RMSEs are approximately 19° and 17°, which indicates that these satellite retrievals meet the requirements of design engineering missions. The wind speed and wind direction RMSEs of ERA5 are approximately 1.9 m/s and 33°, respectively. The correlation coefficients between the HY-2A, CFOSAT, and ERA5 wind speeds and the buoy observations are 0.86, 0.85, and 0.84, respectively, and the corresponding coefficients of the wind direction are 0.98, 0.98, and 0.93, respectively, at a 95% confidence level. However, the wind sensor in the wave glider provides relatively poor-quality observations compared with the buoy measurements and has higher wind speed and wind direction RMSEs of 2.9 m/s and 50.1°, respectively. Taylor diagrams are utilized to illustrate comprehensive wind comparisons between the multiplatform observations and buoy observations. The results help identify the basic biases in SSWs among different products and enhance confidence in the future use of SSW data for studies of upper ocean dynamics and climate analysis. Suggestions are also offered to help improve the design of next-generation wave gliders. [ABSTRACT FROM AUTHOR]

The determination of the ultra-low concentration of 226Ra in water samples (< 0.2 Bq/m3) is carried out by using the 226Ra concentration determination method widely used in oceanography. Various background sources in the determination process were tested and measures to reduce the background were explored. the sum of the residual blank background was reduced to less than 12 mBq after various measures were taken. The requirement of measuring the ultra-low concentration radium solution with concentration < 0.2 Bq/m3 was met. In this paper, the possibility of further reducing the background is suggested. [ABSTRACT FROM AUTHOR]

Physical oceanography plays an important role in the formation of submarine sediments, and the distribution of nutriments and biocenoses in seamounts. The M4 seamount is located in the Caroline Island Ridge of the western Pacific Ocean. The physical properties around M4 seamount are preliminarily analyzed based on the in-situ data obtained in summer 2017 in Caroline M4 seamount and open-sourced data. We found that the water in the upper 200 m is controlled by the westward North Equatorial Current (NEC), while the water between 300–1 000 m is dominated by the eastward North Equatorial Undercurrent (NEUC). The current direction fluctuates significantly below 300 m at upstream stations. At the same depth of the lee sides, the current direction changes with the distance from seamount. These are likely caused by the obstacle of M4 seamount. The calculation results show that there is an anticyclonic cap above M4 seamount caused by tidal rectification. Tidal currents in M4 seamount are squeezed by the topography and amplified, and the amplified tidal currents play a dominant role in M4 seamount. First, the circulation system generated by the interaction of the amplified tidal current and M4 seamount drives the upward/downward movement of the isotherms. Secondly, the thickness of the surface turbulent layer is changed with the tidal phase. Thirdly, high turbulent diffusivities are found in the bottom of M4 seamount, and these are most likely attributed to the turbulent mixing induced by the mutual effect between semidiurnal tidal currents and steep bathymetry. This article of physical oceanography provides scientific basis for further analysis of the distribution of biological community and deposition mechanism in M4 seamount. [ABSTRACT FROM AUTHOR]

Ferromanganese crusts (Fe-Mn crusts) grow very slow and can be treated as condensed stratigraphic sections recording paleo-oceanographic environmental information and local key geological events during the mineralization process. Geochronology, textures, mineralogy, and geochemistry of a Fe-Mn crust sample from the CM6 Seamount of the Caroline Ridge in the Western Pacific Ocean were analyzed by means of electron probe microanalysis and X-ray diffraction. The Fe-Mn crust shows three layers in textural characteristics from bottom to top. The lower, middle, and upper layers presence mottled, botryoidal, and columnar textures, respectively. Ferruginous vernadite, Fe hydroxide, amorphous silicate minerals, calcite, quartz, and feldspar are the main minerals of the Fe-Mn crust. Using cobalt chronometry method, the cumulative growth time of the Fe-Mn crust was determined to be 11 Ma or 25 Ma, of which 25 Ma is inconsistent with other lines of age constraint brought by dating of the substrate. The co-existence of abundant silicate minerals and bioclasts in the middle and lower layers of the Fe-Mn crust diluted the ferromanganese oxide deposits, thus affected the texture, minerals, and geochemical characteristics of the Fe-Mn crust. Variations in Mn, Co, Ni, and other elements content and the burial of opal-A recorded the expansion of oxygen minimum zone (OMZ) in the upper layer of the Fe-Mn crust. In addition, the high-reflectivity Fe-rich laminae might indicate the surrounding volcanic activity. The Fe-Mn crust sample was determined to be hydrogenic by electron probe micro-analyzer (EPMA). The findings help us understand the geochemical characteristics of the Fe-Mn crust in the Caroline Ridge Seamount in the Western Pacific and the variations of paleo-oceanographic environment clues borne by the Fe-Mn crusts. [ABSTRACT FROM AUTHOR]