Abstract: Since 2007, the Yellow Sea has experienced the world's largest green tides, with Ulva prolifera as the dominant species. Those blooms severely impacted the local tourism and aquaculture, resulting in significant economic losses, as well as negative social and ecological consequences. Unlike other global green tides, those in the Yellow Sea are characterized by long-distance drifting and an astonishing scale. These destructive events display significant temporal and spatial variability, which is largely driven by dynamic environmental conditions and human activities. In this review, we summarize recent advancements in understanding the spatiotemporal patterns of long-distance transport, the interannual variability in bloom size, and the underlying mechanisms driving these fluctuations. Additionally, we highlight important knowledge gaps that need further investigation to support the development of effective management strategies for mitigating the impacts of green tides in the Yellow Sea.

Abstract: Tidal storm surges can result in significant damage and inundation if sea defences are insufficiently robust. Calculation of flood risk enables coastal planners to site sea defences and coastal developments appropriately. Since the original work by Gumbel on extreme value statistics, several modifications and new methods have been proposed for the analysis of tidal inundation, with the Skew Surge Joint Probability Method (SSJPM) recently gaining popularity. However, SSJPM is complex, often requiring manual intervention, and is difficult to automate. Guided by the search for a method specifically applicable to tides that is amenable to automation, this paper proposes several modifications to Gumbel's original approach, including reducing the time unit for ranked maxima. This novel technique, here called TMAX, uses a time unit of one tidal-day, rather than the usual annual maxima (AMAX), to carry out an extreme-level analysis of recent tidal data at 35 United Kingdom coastal locations. The TMAX method gives a significantly better internal fit and reduced variance than the AMAX method and compared to a recent study using the SSJPM method at identical coastal locations, shows broad agreement, yet offers a considerably simpler implementation, amenable to automation. This new approach better informs strategies for coastal management and resilience.

Abstract: Artificial ocean alkalinization (AOA) is one of the most promising marine carbon dioxide removal technologies. We applied the results from the 6th Coupled Model Intercomparison Project (CMIP6) to characterize the temporal and spatial variabilities of future marine carbon chemistry under the implementation of AOA. Our study shown the carbon system varied widely under the implement of AOA, but some efficiencies may be covered up by the forcing of high carbon emission scenario. Basing on the CMIP6 protocol, which added 0.14 Pmol alkalinity into the ocean ever year, AOA promoted the increase of DIC, delayed the rise of pCO2, and restrained the aggravation of pH and Ω, actually. The temperate oceans in both hemispheres were the most significant impacted basins, whereas the Southern Ocean were the less affected region. In the present century, the oceanic carbon sink would intensify rapidly until the year around 2080, and then weaken slowly. Implementation of AOA merely changed the relative strength of oceanic sink rather than its variation pattern. In deep ocean, what’ more, the effectiveness of AOA did exist, but was quite little for the mitigation of ocean acidification.

Abstract: Extreme wind waves occurring during storms are a major natural hazard for the maritime economy on the one hand and a driver of various natural processes, e. g. the erosion of coastlines, on the other. Assessing the extreme values of wind wave heights and their long-term trends is crucial for coastal and offshore engineering and climate change studies. This study is dedicated to the values and long-term trends of extreme wave heights in the Black Sea. A 73-years long reanalysis is applied for the study. In order to additionally validate the reanalysis, data on wave heights form the Saral/AltiKa satellite altimeter is used. 19 locations along the coastline of the Black Sea are selected for the analysis of wind wave data. Maximal significant wave heights exceed 8.5 m along the southwestern coast of the Crimean Peninsula. Besides, 99.9th, 99th and 95th percentiles of significant wave heights are assessed. The long-term linear trends of these values are in general not statistically significant except of one location in case of maximal significant wave heights and two locations in case of 95th percentile of significant wave heights.

Abstract: Mesoscale eddies play a critical role in ocean circulation and biogeochemical processes, yet predicting their dynamic characteristics remains challenging due to nonlinear interactions and background errors in traditional methods. This study proposes a physics based Long Short-Term Memory (LSTM) network to predict key eddy features, amplitude, radius, and maximum circularly averaged speed (MCAs), by integrating multi-source observational data and hydrodynamic principles. Utilizing 28 years (1993-2020) of daily eddy trajectories from the global META3.1exp atlas and high-resolution reanalysis data (JCOPE2M) in the Northwest Pacific (15°-35°N, 115°-135°E), we systematically evaluate the effects of temporal sequence length and physical variables on prediction performance. The model demonstrates superior accuracy compared to conventional LSTM approaches, with mean absolute errors (MAE) for 1-7 day predictions increasing from 0.72 cm to 1.37 cm (amplitude), 8.85 km to 18.02 km (radius), and 0.80 cm/s to 2.46 cm/s (MCA). Key innovations include: 1) Dynamic reconstruction of spatiotemporal label-feature relationships to mitigate error accumulation, 2) Incorporation of sea surface temperature (SST) and height (SSH), which improve prediction accuracy by 5.33-5.92% and 3.65-5.47%, respectively, outperforming eddy kinetic energy inputs. Seasonal analysis reveals lower model accuracy in summer versus winter, particularly for amplitude (MAE: 1.29 cm vs 1.03 cm) and radius (15.3 km vs 13.2 km). Interannual error patterns correlate with El Niño events, highlighting climate-ocean coupling effects. This work advances eddy prediction through physics-guided machine learning, providing a framework for operational ocean forecasting. Future extensions could incorporate three-dimensional eddy structures and additional environmental drivers to enhance predictive capability.

Abstract: The air-sea transfer of gases is important within climate physics, biogeochemistry and the control of pollutants. A two-layer model of transfer directly across the sea surface underpins most discourse, but an expanding literature also features transfer mediated by “suspended fragments”, either bubbles in the upper ocean or drops and aerosol in the lower atmosphere. Here, we describe a categorization of process that elucidates departures from two-layer theory and is a starting point for quantification. Six distinct phenomena are identified that cause a transfer of gas across an interface such as the sea surface. A total of eight categories are identified. Each category has a distinct scaling with respect to the properties of the gas and this is key to the relative importance of different categories and processes. Transfer through sea spray can be an exchange process, but the evaporation of sea spray is more effective and is an ejection process. The reactivity of carbon dioxide in aqueous solution enhances the effect of spray. Exceptional levels of sea spray generation and evaporation are required to be significant for most gases, but moderate levels are sufficient for carbon dioxide and the most soluble pollutants.

Abstract:

Short-term sea surface temperature (SST) forecasts are crucial for operational oceanology. This study introduced a specialized Transformer model (U-Transformer) to forecast global short-term SST variability and to compare with those from Convolutional Long Short-Term Memory (ConvLSTM) and Residual Neural Network (ResNet) models. The U-Transformer model achieved SST root mean square errors (RMSEs) of 0.2–0.54 °C for lead times of 1–10 days during 2020–2022, with anomaly correlation coefficients (ACCs) from 0.97 to 0.79. In regions characterized by active mesoscale eddies, RMSEs from the U-Transformer model exceeded the global averages by at least 40%, with increases exceeding 100% for the Gulf Stream region. Additionally, ACC values in active mesoscale eddy regions declined more sharply with forecast lead time compared to the global averages, decreasing from approximately 0.96 to 0.73. Specifically, in the Gulf Stream region, the ACC value dropped to 0.89 at a 3-day lead time, while the value can maintain 0.92 globally. Compared with the ConvLSTM and ResNet models, the U-Transformer model consistently delivered smaller RMSEs and larger ACCs, especially in regions with active mesoscale eddies. These findings imply the importance of advanced approaches to enhance SST forecast accuracy in regions with active mesoscale eddies.

Abstract: The continuous monitoring of radioactivity in a cabled subsea network in the North Sea Observatory was performed to test the performance of a medium resolution underwater spectrometer as well as to identify and to assess potential anthropogenic and/or natural hazards. The effectiveness of continuous monitoring is tested together with the operability of underwater sensor and optimized quantification methods to iden-tify the type of the radioactivity as well as the activity concentration of radionuclides in the seawater. In the frame of RADCONNECT project, the medium resolution underwater radioactivity system named GeoMAREA was integrated in an existing cabled ocean observatory placed in Helgoland Island (COSYNA network). The system operated in an online mode controlled by the operational Centre (AWI) as well as remotely from the end-user (HCMR). The system provided gamma-ray spectra and activity concentrations of key radionuclides that were enriched in seawater during the monitoring period. As con-cerns the quantification method of natural radioactivity, the average activity concentration (in terms of the total monitoring period) of 214Bi, 208Tl, 228Ac and 40K, was found 108 ± 30, 57 ± 14, 40 ± 5 and 9800 ± 500 Bqm-3, respectively. As concerns the quantification of 137Cs, the average activity concentration in terms of the total monitoring period (although it is uncertain) was found 6 ± 4 Bqm-3. The data analysis proved that the system had a stable operation in terms of voltage stability so that all acquired spectra could be summed up efficiently in time to produce statistically high gamma-ray spectra for further analy-sis.

Abstract:

Bottom trawling is not selective fishing method, resulting in the capture of many bycatch species. This study aimed to examine the distribution of bycatch species in the hake-directed bottom fishery and to determine their potential for bycatch management and mitigation. Observer data from a hake-directed bottom trawl fishery in Namibia from 1997 to 2014 was analysed. About 23 bycatch species, weighing 9,031,480 tonnes, were recorded. Trachurus capensis, Trachipterus trachypterus, Helicolenus dactylopterus, Lophius vomerinus, and Genypterus capensis were the dominant species, comprising 63.09% of the total catch by weight. Analysis of Similarities (ANOSIM) (R = 0.88, P< 0.05) revealed significant differences in catch composition based on sampling site. The Similarity Percentage (SIMPER) showed that three bycatch species contributed the most to the dissimilarity in groups for spatial distribution. Widespread distribution of bycatch species, with high densities in the central and southern regions, suggests that hake-directed bottom trawling could have negative effects on these species. Species with a higher proportion of their population removed as bycatch, are considered the most vulnerable and may be nearly exterminated. To avoid the risk of species extinction, the fishery must be managed through spatial exclusion and fishing seasons.

Abstract:

Whale signals originating in the vicinity of a triplet of underwater hydrophones, 2 km distant from each other, and recorded at the three hydrophones, offer the opportunity to verify simple models of propagation applied in the immediate neighborhood of the triplet, by comparing arrival times and amplitudes between the three hydrophones. Examples of recordings of individual fin whales based on the characteristics of their vocalizations around 20 Hz, passing by hydrophone triplets are presented. Conclusions are drawn about waveform coherency and amplitudes of the signals recorded at the three hydrophones in the [10-50] Hz frequency band. A grid-search method of tracking the calls is presented based on time differences of arrivals between three hydrophones obtained with a combination of power detector time picking and cross-correlation. The spherical amplitude decay law of one over the distance is verified using amplitude ratios between two of the hydrophones, when the cetacean is in the immediate vicinity of the triplet, in a circle of radius 1.5 km sharing its center with the triplet. In turn, the measurement of the amplitude ratios between two hydrophones allows for an estimate of the depth of vocalization when the animal is within 250 m of horizontal distance of one of the hydrophones. Analysis of hundreds of calls leads to the possibility that more accurate coordinates and depth of the hydrophones are needed to unambiguously verify the laws of propagation, or that more elaborate non-isotropic models of propagation are needed.

Abstract: Sea surface currents (SSC) play a pivotal role in material transport, energy exchange, and ecosystem dynamics in coastal marine environments. While traditional methods to obtain wide-range SSC, such as satellite altimetry, often struggle with limited performance in coastal regions due to waveform contamination, deriving SSC from sequential ocean color data using the Maximum Cross Correlation (MCC) has emerged as a promising approach. In this study, an enhanced MCC method called the Tide-Restricted Maximum Cross Correlation (TRMCC) is proposed and implemented on hourly ocean color data obtained from the Geostationary Ocean Color Imager II (GOCI-II) to derive SSC in coastal seas and turbid estuaries. Cross-comparison over three years with buoy data, high-frequency radar, and numerical model products shows that the TRMCC is capable of obtaining high-resolution SSC with good accuracy in coastal and estuarine areas. Both large-scale ocean circulation patterns in seas and fine-scale surface current structures in estuaries can be effectively captured. The deriving accuracy, especially in coastal and estuarine areas, can be significantly improved by integrating tidal current data into the MCC workflow, and the influence of invalid data can be minimized by using a flexible reference window size and the Normalized Cross-Correlation in the Fourier Domain technique. Seasonal SSC structure in Bohai Sea and diurnal SSC variation in the Yangtze River Estuary were depicted via satellite method for the first time. Our study highlights the vast potential of the TRMCC to be able to improve understanding of current dynamics in complex coastal regions.

Abstract: Storm surge barriers are crucial for the flood protection of the Netherlands and other Deltas. In order to guarantee a high safety level, a high closure reliability is required. In the Netherlands, the reliability of flood defenses is typically assessed based on extreme water level and wave height statistics. Yet, in case of operated flood defenses, such as storm surge barriers, the temporal clustering of successive events may be just as important. This study investigates the evolution and associated flood risk of clusters of successive storm surge peaks at the Maeslant Storm Surge Barrier in the Netherlands. Two mechanisms are considered that may lead to a series of storm surge peaks. Multi-peaked storm surges, as a consequence of tidal movement on top of the surge, are studied by means of simplified storm patterns that are widely used within the Netherlands. Clusters of surges resulting from different, but related storms are investigated by means of time series analysis of a long sea-level record close to the Maeslant Barrier. We conclude that the tendency of storms to cluster and especially the occurrence of multi-peaked storms may substantially increase the flood risk in the area behind the Maeslant Storm Surge Barrier and we envision that the influence is likely to increase with sea-level rise. The numbers are however highly uncertain due to the strong sensitivity to assumptions, model choices and applied data set. More insight in the statistics of the time evolution of extreme sea water levels is needed to better understand and ultimately to reduce these uncertainties.

Abstract: CTD profilers are used as reference instruments to qualify temperature and salinity data. Their metrological specifications can be controlled in calibration bath and calibration coefficients can be applied to correct the linearity of sensors and the trueness of measured data with a given uncertainty. However, in ocean areas with thermal gradients, the uncertainty of the measured data is questionable due to the thermal inertia of sensors and the movements of the CTD, in relation with the roll or pitch of the boat. In order to evaluate these measurement uncertainties and in order to be able to use the upcast profiles, a double C-T sensors SBE 9 profiler was fixed under a carousel water sampler, the second C-T couple being at the top of the carousel frame. This configuration allows the evaluation of temperature measurement deviations of recorded profiles. In order to quantify the different sources of instrumental uncertainties, the temperature signal has been modelled accounting for the movements induced by the boat. The result allows to quantify what can be called the representativeness of CTD’s temperature measurements. This notion is very useful in data assimilation process. A table quantifying the various sources of uncertainty has been created from profiles obtained during four offshore campaigns. In the future, it could be used to find the representativeness of similar profiles obtained with a single pair of sensors.

Abstract: The results of oceanographic observations conducted on board the R/V “Dalnie Zelentsy” along the Kola Section during 2017–2023 are presented. The main focus is on the assessment of frontal zone characteristics in the northern part of the Polar Front during autumn, winter, and spring periods. To estimate sea ice anomalies, data from the World Data Center for Sea Ice (AARI WDC Sea-Ice) were used. A comparison was made between observational data from the northern section near the Marginal Ice Zone and temperature and salinity characteristics from global oceanographic databases. The comparison involved products such as MERCATOR PSY4QV3R1, CMEMS GLORYS12v1, and TOPAZ5. High-gradient zones in temperature and salinity fields were identified along all sections at varying distances from the ice edge. It was confirmed that the western Barents Sea had experienced a steady trend of sea ice cover declining over the past three decades. The northernmost frontal zone of the Polar Front in the Barents Sea, along the Kola Section axis, detected at distances of 48 to 290 km from the ice edge. Temperature gradients ranged from 0.10 to 0.20 °C/km, salinity gradients varied from 0.012 to 0.025 psu/km, and the width of the frontal zone did not exceed 55 km. The best correlation with the measurement results was observed in for the MERCATOR PSY4QV3R1 product.

Abstract: Sea level rise (SLR) poses significant risks to coastal regions worldwide, with over one billion people living in low-lying areas already experiencing its effects. Mozambique, with a population of 32.97 million and an extensive coastline, is particularly vulnerable to extreme events. This study examines the past and future dynamics of sea level rise along the Mozambican coast, focusing on the cities of Maputo, Inhambane, Beira, and Pemba. Using a combination of historical sea level data (2010-2020) and future projections (2021-2050) derived from global climate models (CMIP6) and oceanographic databases, the study analyzes regional variations in sea level behavior through time series and spatial distribution using Matlab for image visualization. The results highlight that Pemba and Maputo are the most vulnerable areas to rising sea levels. Therefore, integrated adaptation strategies are recommended, prioritizing nature-based solutions within disaster risk management frameworks to protect Mozambique's coastal communities and ecosystems, ensuring greater resilience to the ongoing and projected impacts of sea level rise.

Abstract: This paper describes recent variations that have emerged in spatial patterns of retroflections in the monthly Gulf Stream (GS) path. They have become less frequent and also shifted further to the east; we find this in both reanalysis and free-running model data of the ocean. A suite of eddy-rich North Atlantic ocean ensemble simulations, forced with varying combinations of realistic and climatological boundary conditions, is used to diagnose the relative importance of atmospheric and oceanic drivers of these changes. It is implied that the majority of the shifts and changes in the number of retroflections throughout the five decades (1963-2012) are products of realistic atmospheric forcing and oceanic boundary conditions but only the latter is found to be statistically significant.

Abstract: We show that analyzing archived and future multibeam backscatter and bathymetry data, in tandem with regional environmental parameters, can help identify polymetallic nodule fields in the world’s oceans. Extensive archived multibeam transit data through remote areas of the world’s oceans are available for data mining. New multibeam data will be made available through the Seabed 2030 Project. Uniformity of along and across track backscatter, backscatter intensity, angular response, water depth, nearby ground-truth data, and local slope, sedimentation rate, and seafloor age provide thresholds for discriminating areas permissive for nodule presence. A case study of this methodology is presented using archived multibeam data from a remote section of the South Pacific along the Foundation Seamounts between the Selkirk paleomicroplate and East Pacific Rise that were collected in 1997 during the Hotline cruise. The 12 kHz Simrad EM12 DUAL multibeam and the forementioned data strongly suggest a previously unknown nodule occurrence exists. Methods include comparing analyses using three different backscatter products to further determine if scanned backscatter products, rather than primary digital multibeam files can be used for analysis, and comparing results from using digitized 8-bit images, or 8-bit and decibel-value surfaces derived from the MB-SystemTM software. We show this expeditious analysis of broad areas of multibeam data could characterize benthic habitat types efficiently in remote deep ocean areas prior to more time consuming and expensive video and sample acquisition surveys. Additionally, utilizing software other than specialty sonar processing programs during this research explores how multibeam data products could be interrogated by a broader range of scientists and data users. Future mapping, video, and sampling cruises in this area would test our prediction and investigate how far it might extend to the north and south.

Abstract: Coastal flooding is already one of the most dangerous and costly natural hazards that humanity faces globally and yet it will become even more frequent and challenging to manage because of climate change and other factors. In densely populated estuarine settings, a storm surge barrier is often an attractive and economical solution for flood protection. There are currently many storm surge barriers in operation around the world protecting tens of millions of people and trillions of pounds of property and infrastructure. However, with accelerating rates of sea-level rise being observed, along with changes in storminess, tides and river discharge, surge barriers are closing increasingly often, and closures are now occurring in months when they typically have not occurred in the past. Increased use of surge barriers in the future has critical implications for barrier management, maintenance and operation. In this paper we develop, validate and apply a novel statistical approach to assess how the number of storm surge barrier closures will likely increase in the future and change in frequency throughout the year, that can be used for different climate change scenarios and accounting for forecast errors in water levels. As representative case study examples, we focus on the Eastern Scheldt storm surge Barrier in the Netherlands and the Thames Barrier in the UK. We validate the method, demonstrating it accurately predicts past closure statistics for the Eastern Scheldt and the Thames Barriers over the 38 and 42 years they have been operational, respectively. Then we apply the method to estimate the potential future numbers of barrier closures considering a range of different projections of sea-level rise, along with changes in storm surges, tides and river discharge. We show that there is very likely to be a rapid acceleration in the number of barrier closures in the future, dominated by sea-level rise, with strong influence of the 18.6-year lunar nodal cycle, at both case study barriers. Finally, we illustrate how the tool can be used to help guide future barrier management, maintenance, operation and upgrade/replacement planning and inform adaptative flood management approaches. The tool we have developed could easily be extended to other storm surge barriers around the world.

Abstract: In submerged landscapes, distinguishing anthropogenic features versus natural ones, is often challenging. We have developed a set of criteria to validate the identification of submerged anthropogenic remains that include, examining the geological context, sea-level considerations, associated archaeological finds (including coastal survey), and documenting the broader archaeological context. Furthermore, our experience demonstrates that, while progress has been made in applying remote-sensing technologies to detect anthropogenic features on the seabed, there is no substitute for direct, visual assessment by an underwater archaeologist for verification of their anthropogenic status. We have applied these criteria to examine two published case studies detailing suspected anthropogenic stone features on the seabed in the Sicilian Channel. Our examination has led us to conclude that both localities are not anthropogenic features. The Pantelleria Vecchia Bank features represent natural outcrops on a submerged paleo-landscape that were shaped by depositional and erosional processes, during transgression and regression periods. The suspected Lampedusa cultic site, comprises natural features that are located on a submerged neo-landscape formed due to erosion and retreat of the coastal cliff since the Mid -Holocene, when sea level reached its present level.

Abstract: The article considers the role of transcrustal magma- and fluid-conducting faults in the formation of mineral deposits, shows the importance of a deep source of heat and hydrothermal solutions in the genesis and history of the formation of these deposits. As a result of the impact on the lithosphere of mantle jets rising along transcrustal faults, intense block-and-clump deformations and tectonic movements are generated; rift systems and volcanic-plutonic belts spatially combined with them are formed; intrusive bodies are introduced. At ore deposits, these processes cause epithermal ore formation as a consequence of the impact of mantle jets rising along transcrustal faults on the lithosphere. At hydrocarbon fields, they play an extremely important role in conduction and convective heat and mass transfer to the area of hydrocarbon generation, determine the relationship between the processes of lithogenesis and tectogenesis, and activate the generation of hydrocarbons from oil and gas mother formations. Detection of transcrustal magma- and fluid-supporting faults was carried out by MMZ and MTZ in combination with other geological and geophysical data. Practical examples are given for mineral deposits under which subvertical transcrustal columns of increased permeability traced to considerable depths have been found. The nature of these unique structures is related to faults of pre-Paleozoic time of emplacement, which determined the fragmentation of the subcrystalline structure of the Earth and later developed inherited in the conditions of development of volumetric fluid dynamics. The residual forms of functioning of fluid-conducting thermohydrocolumns are granitoid batholiths and other magmatic bodies. Experimental modelling of deep processes allowed to reveal the quantum character of interactions of crystal structures of minerals with "inert" gases under elevated T-P conditions. The role of helium, nitrogen and hydrogen in changing the physical properties of rocks in connection with their intrastructural diffusion has been clarified. As a result of low-energy impact, stress fields are formed in the solid rock skeleton, the structure and texture of rocks are rearranged, and general porosity develops. With increasing pressure, energy interactions intensify, deformations, phase transitions and chemical bonds occur in an unstable geological environment, which increases with increasing gas saturation, pressure, and temperature. The process of heat and mass transfer along transcrustal magma- and fluid-supplying faults to the Earth's surface occurs in stages with energy release, which can manifest itself in the form of explosions on the day surface, in coal and ore mines, in earthquakes and volcanic eruptions.