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The Antarctic Slope Front and the associated Antarctic Slope Current dynamically regulate the exchanges of heat across the continental shelf break around Antarctica. Where the front is weak, relatively warm deep waters reach the ice shelf cavities, contributing to basal melting and ultimately affecting sea level rise. Here, we present new 2017–2021 records from two moorings deployed on the upper continental slope (530 and 738 m depth) just upstream of the Filchner Trough in the southeastern Weddell Sea. The structure and seasonal variability of the frontal system in this region, central to the inflow of warm water toward the large Filchner‐Ronne Ice Shelf, is previously undescribed. We use the records to describe the mean state and the seasonal variability of the regional hydrography and the southern part of the Antarctic Slope Current. We find that (a) the current is, contrary to previous assumptions, bottom‐enhanced, (b) the isotherms slope upwards toward the shelf break, and more so for warmer isotherms, and (c) the monthly mean thermocline depth is shallowest in February‐March and deepest in May‐June while (d) the current is strongest in April‐June. On monthly timescales, we show that (e) positive temperature anomalies of the de‐seasoned records are associated with weaker‐than‐average currents. We propose that the upward‐sloping isotherms are linked to the local topography and conservation of potential vorticity. Our results contribute to the understanding of how warm ocean waters propagate southward and potentially affect basal melt rates at the Filchner‐Ronne Ice Shelf. Plain Language Summary: Melting at the base of the Filchner‐Ronne Ice Shelf in the southeastern Weddell Sea is predicted to increase dramatically. The melt occurs within the ice shelf cavity filled with seawater, and the heat needed to melt the ice comes from warm water from the deep ocean. The warm water is carried toward the cavities over the relatively shallow continental shelves by ocean currents. The Antarctic Slope Current, a current that flows along the continental slope between cold and warm water masses, limits the amount of warm water that enters the continental shelf. Here, we use new four year‐long mooring records from the upper part of the continental slope north of the Filchner‐Ronne Ice Shelf and just east of the Filchner Trough to describe how the current changes with the season and how its vertical structure evolves throughout the year. We find that the warm water is lifted up toward the shelf break and suggest that this is linked to the presence of the Filchner Trough. An improved understanding of the dynamics of the Antarctic Slope Current in the region will allow us to better evaluate the potential for dramatic changes to the system in the future. Key Points: Four years of observations show that the Antarctic Slope Current north of the Filchner Trough is bottom‐enhanced and strongest during winterThe bottom enhancement is linked to isotherms that slope upward toward the shelf break, facilitating on‐shelf transport of warm waterOn monthly to seasonal time scales, positive temperature anomalies above the slope are associated with weaker‐than‐normal currents and vice versa [ABSTRACT FROM AUTHOR]

Chromophoric dissolved organic matter (CDOM) is a ubiquitous component in marine environments, and substantial changes in its sources and distribution, related to the carbon cycle in the Arctic Ocean, are expected due to Arctic warming. In this study, we present unique CDOM data in the Eurasian Arctic Ocean derived from the year‐round MOSAiC expedition. We used CDOM absorbance spectra and fluorescence excitation‐emission matrices in combination with parallel factor analysis to characterize differences in DOM sources and composition. Our results suggested that terrestrial DOM was less sensitive to seasonal changes but controlled by regionality in hydrography. Elevated dissolved organic carbon (DOC) levels in polar surface water were primarily derived from terrigenous sources as identified by CDOM absorption and fluorescence characteristics. In the Amundsen Basin and western Fram Strait surface waters, to which terrestrial DOM is primarily transported by the Transpolar Drift, we found, on average, a 188% larger meteoric water fraction and a 40% higher DOC concentration compared to the Atlantic water that dominated western Nansen Basin and Yermak Plateau. In the Amundsen Basin, the DOC concentration in summer of surface water was only 13% higher compared to winter season. Additionally, autochthonous DOM and chlorophyll‐a concentrations were relatively low in surface water and exhibited significant differences compared to those observed in summer, while there were significant differences between autochthonous DOM and chlorophyll‐a. We also observed that sea ice melt contributed to autochthonous DOM in summer, while storms in winter affected the vertical distribution of terrestrial and autochthonous DOM in the subsurface. Plain Language Summary: In the Arctic Ocean, dissolved organic matter (DOM) is important because it represents a large carbon reservoir that cycles through the environment and supports the growth of marine life in the Arctic. DOM originates from various sources and its composition changes depending on factors like location and time of year, largely influenced by ocean currents. Microbes in the water break down DOM, but this process is hindered during the winter months and in areas with limited sunlight. Due to the very limited and challenging accessibility of the Central Arctic Ocean, there is a lack of DOM data, especially during winter in the Eurasian Arctic Ocean. Scientists conducted a comprehensive year‐round study during the MOSAiC expedition and discovered that much of the DOM in the Arctic comes from land in Siberia. Additionally, seasonal changes were observed to alter the composition of locally produced chromophoric DOM (CDOM) in surface waters of the Amundsen Basin. In contrast, terrestrial CDOM is less responsive to seasonal shifts but more influenced by regional variations in hydrography. This highlights the substantial role of regional hydrographic differences in shaping the characteristics of DOM in surface water across the Eurasian Arctic Ocean. Key Points: Elevated dissolved organic carbon levels in polar surface water are primarily derived from terrigenous sources in the Eurasian basinContrasting dissolved organic matter characteristics in Amundsen and Nansen basins caused by Transpolar Drift watersAutochthonous dissolved organic matter in polar surface water is low in winter and significantly different from that in summer [ABSTRACT FROM AUTHOR]

Anthropogenic radionuclides 129I and 236U are used to investigate pathways of the Atlantic Water flow in the Canada Basin, estimate transport timescales, and investigate mixing dynamics within the Atlantic Water layer and the overlying Pacific Water. Transit Time Distribution (TTD) model mean ages indicate water takes 25–35 years to reach the Canada Basin from the entrance of the Arctic, with limited lateral and vertical mixing along the core of the Arctic Ocean Boundary Current. Mode ages obtained from the model yield shorter transport times of 20–32 years. These age estimates agree with previous studies using these radionuclides and ventilation tracers in this region, indicating a steady‐state flow of Atlantic Water for the last 15 years. The distribution of the isotopes in the Atlantic layer indicates two pathways Atlantic Water may take into the basin, supported by the distribution of ages in the TTD model. End‐member mixing models indicate that the Pacific Winter water acquires a 20%–40% Atlantic Water signal of the radionuclides, upwelled over short periods, most likely along the shelf and Barrow Canyon region. Plain Language Summary: Man‐made nuclear products are used to trace the path of Atlantic water from the Atlantic Ocean to the Canada Basin in the Arctic, determine its transit time, and how it interacts with itself and Pacific Water that enters through the Bering Strait. The model suggests water takes 25–35 years to flow from the entrance of the Arctic to the Canada Basin, while a second estimate of age suggests slightly shorter transit times. The results of this study show that Atlantic Water flow has not changed significantly in the last 15 years. The distribution of the isotopes and ages also indicates two possible pathways water may take to the basin. An additional finding is that Pacific Winter Water carries a tracer concentration of 20%–40% of Atlantic Water, probably from Atlantic Water upwelling along the shelf, and in the Barrow Canyon region. Key Points: 129I and 236U trace Atlantic sourced water in the Canada BasinUpwelling of tracer labeled Atlantic Water into the Pacific Winter Water distinguishes the layer from Pacific Summer WaterTransit time distributions yield ages of 25–35 years for the core Atlantic Water [ABSTRACT FROM AUTHOR]

The Atlantic Niño is an important source of the year‐to‐year variability of the tropical Atlantic, consisting in an irregular oscillation of the Sea Surface Temperature (SST) in the eastern tropical Atlantic. The physical mechanism underlying this oscillation is topic of debate. Some theories, known as dynamical, suggest that the Atlantic Niño is driven by internal wave dynamics. Other theories, termed thermodynamic, propose that the eastern tropical Atlantic SST variability is caused by thermodynamic processes associated with heat fluxes at the ocean surface and/or heat transport by oceanic currents. Here, we examine the SST variability from 1940 to 2022 and find that it can be described in terms of two spatial modes: one in the central and the other in eastern tropical Atlantic. However, focusing on the period from 1993 to 2022, these patterns behave differently. In 1993–2009 they concur in determining the eastern tropical Atlantic SST variability, while in 2010–2022 they act in opposite direction. Therefore, we use Sea Surface Height data and heat fluxes advected by oceanic currents to explore the relative contribution of wave dynamics and heat advection to the eastern tropical Atlantic SST fluctuation. We show that, between 1993 and 2010, the eastern tropical Atlantic SST variability is mainly determined by heat advected from the south by horizontal currents, while between 2010 and 2022 it can be explained in terms of wave dynamics. This finding suggests that the two spatial patterns determining the eastern tropical Atlantic SST variability, are two distinct physical phenomena forced by different physical mechanisms. Plain Language Summary: The Atlantic Niño/Niña is a significant pattern of interannual tropical climate variability. It is characterized by irregular oscillations of the temperature in the eastern tropical Atlantic, alternating between warm (Atlantic Niño) and cold (Atlantic Niña) phases. The physical mechanisms underlying these oscillations are still a matter of debate. Some theories, known as thermodynamic, attribute them to heat fluxes at the ocean surface and/or heat transport by oceanic currents. Other theories, referred to as dynamical, suggest that the temperature oscillations are driven by equatorial internal waves, which modify the vertical structure of the Ocean and affect the heat content of the water column. Recent research has also revealed that oscillations of the eastern Atlantic temperature are associated with two distinct spatial patterns: one in the central tropical Atlantic and the other in the eastern. We show that both wave dynamics and heat advection by oceanic currents play a role in determining changes in the temperature of the eastern tropical Atlantic. However, they act selectively, leading us to hypothesize that the two spatial modes of the eastern Atlantic temperature variability are two distinct physical phenomena driven by the alternate superposition of heat fluxes caused by oceanic currents and wave dynamics. Key Points: The variability of the sea surface temperature in the eastern tropical Atlantic can be described by two independent spatial modesThe eastern tropical Atlantic sea surfacetemperature variability is determined by Kelvin wave dynamics and heat advected by ocean currentsThe action on the sea surface temperature variability of wave dynamics and heatadvection caused by ocean currents is selective [ABSTRACT FROM AUTHOR]

This study investigates the temporal variations in methane concentration and flare activity in the Hola trough (offshore Norway) during May 2018 and June 2022. Between these time periods, methane seep activity exhibits 3.5 times increase, as evidenced by hydroacoustic measurements. As the seep area in the Hola trough is constantly within the hydrate stability zone, the observed increase cannot be attributed to migration of its shallow boundary due to temperature increase. However, a combination of low tide conditions resulting in a lower sediment pore pressure and a bottom water temperature increase resulting in a lower methane solubility is likely to explain the increase in the number of seeps observed in June 2022. The hypothesis of tide influence is supported by data collected from a piezometer deployed and recovered during the cruise showing that the tidal effect was observed 3 m below the seafloor. Despite the numerous methane seeps detected, methane concentration and gas flow rates near the seafloor were low (<19 nM and <70 mL min−1, respectively) compared to other areas with methane seep activity. This is likely due to strong currents rapidly dispersing methane in the water column. Sub‐seafloor investigations identified pathways for gas migration in methane seep areas, influenced by topography. This study provides valuable insights into the temporal dynamics of methane concentrations, flare activity, and gas distribution in the Hola trough, contributing to our understanding of offshore methane dynamics in the region. Plain Language Summary: The Hola Trough, offshore Norway's Lofoten‐Vesterålen (LoVe) area, has been of interest for many years due to its rich marine life and potential oil and gas resources. There, coral mounds thrive around methane seepage. The LoVe observatory network monitors this unique environment. Using this observatory platform, associated data set and research expeditions at sea, the project EMAN7 (Environmental impact of Methane seepage and sub‐seabed characterization at LoVe‐Node 7) aims to understand the environmental impact of methane seepage as well as its spatio‐temporal variability. The comparison of methane seep activity during two summers with different environmental conditions revealed 3.5 times more seeps when a combination of warmer bottom water and low tide changes the sediment pore properties. A sensor recording subseafloor pore pressure and bottom temperature supports these findings. Sub‐seafloor investigations identified routes for gas migration in methane seep areas, influenced by topography. Key Points: A combination of warmer bottom water and low tide increases methane seeps 3.5 times by altering sediment gas solubility and pore pressureIntermittent seeps and strong oceanic currents explain the limited microbial mats and the low methane concentration in the water columnWe found sub‐seafloor pathways for gas migration in methane seep areas, influenced by topography [ABSTRACT FROM AUTHOR]

The freshwater transport (Mov) by the Atlantic Meridional Overturning Circulation (AMOC) across 34.5°S is computed using observations from 49 eXpendable BathyThermograph (XBT) transects between 2002 and 2019. The Mov at 34.5°S serves as a possible indicator of the AMOC stability, with a negative (southward) freshwater transport indicating a possible bistable AMOC regime and positive (northward) transport indicating a monostable regime. A negative Mov mean of −0.15 ± 0.09 Sv is estimated from the repeated XBT transects, suggesting a bistable AMOC regime. Results are complemented with two data sets derived from Argo float observations, numerical ocean models, and coupled climate models. More than half of the coupled models examined, 20 out of 32, present positive Mov mean values. To investigate the causes of the differing signs of the Mov across the models, we examine the salinity vertical structure in models with positive and negative Mov, indicating fresher upper and saltier deep waters in models with positive Mov. The South Atlantic meridional fluxes show linear relationships, with a negative slope (positively correlated in magnitude) between Mov/MOC and Mov/MHT, and a positive slope (positively correlated) between MHT/MOC. Seasonally, the South Atlantic meridional fluxes from most of the data sets considered here, show a more negative Mov and a more positive MOC and MHT in austral fall and winter from April to August across 34.5°S. Plain Language Summary: It is well known that the meridional (north‐south) overturning circulation, a large system of ocean currents driven by winds, buoyancy (density) differences, mixing, and eddies, has a significant impact on the world's climate system. Based on observations and numerical model data, this study presents a multi‐data set analysis of the freshwater transported by this circulation system across the nominal latitude of 34.5°S in the South Atlantic. The observed southward meridional freshwater transport (out of the South Atlantic) derived from all the observational data sets considered indicates a bistable regime of the meridional overturning circulation. Some coupled models that suggest a mono‐stable (one stable state) regime have fresher upper and saltier deep waters than the models that indicate a bistable regime (two stable states). We confirm that there is a linear relationship between mass transport by the meridional overturning circulation with the meridional freshwater and heat transports. Finally, we determine the seasonal variability of these meridional fluxes, with a more negative meridional freshwater transport, as well as a more positive overturning circulation volume and heat transports from April to August in the South Atlantic Ocean across 34.5°S. Key Points: Observational‐based estimates of negative freshwater transports by the AMOC (Mov) at 34.5°S, suggest a bistable AMOC regimeMany coupled models demonstrate positive Mov values, attributed to biased salinity vertical profile patternsThe Mov is positively correlated in magnitude with mass and heat transport by the meridional overturning circulation [ABSTRACT FROM AUTHOR]

The Malvinas Current (MC) in the Southwestern Atlantic is characterized as a system of multiple Lagrangian jets. This is done by applying geodesic theory of Lagrangian Coherent Structures (LCSs) on altimetry‐derived velocity. The number and spatial disposition of jet‐cores organizing the MC are found to vary in time influenced by topographic waves propagating along the current. The Lagrangian analysis reveals that permanent jet‐cores tend to approach one another upstream, yet do not merge into a single jet as the Eulerian analysis of the data suggests. Independent support for the existence of multiple jets is provided by trajectories of surface drifters from a deployment of unparalleled dimensions for the region and ocean color images. The drifters develop the characteristic boomerang‐shaped patterns into which passive tracers straddling jet‐cores deform and exhibit Lagrangian metrics that are largely consistent with those derived from altimetry data. Ocean color imagery reveals similar "chevrons" and suggest upwelling along the jets, which is consistent with a new solution of arrested topographic wave dynamics. This observation and the finding that the MC jet system is influenced by propagating waves suggests that the MC variability may have major implications in the modulation of primary productivity on synoptic timescales. Drifters flowing into the open ocean, exhibit organizing patterns that are largely shaped by mesoscale circulation and essentially differ from those observed along the MC. Evidence of this observation is provided on the basis of LCS analysis and the calculation of a quasi‐objective Lagrangian metric derived directly from drifter trajectories. Plain Language Summary: The ocean circulation exhibits complex motions ranging across a large span of spatio‐temporal scales. Despite this complexity, distinguished material curves known as Lagrangian Coherent Structures (LCSs) may underlie the system dynamics and provide the backbones of flow organization. These structures may represent the centerpieces of passive tracer filaments, they may delineate the axes of Lagrangian jets, or they may provide boundaries to material eddies. In this work, we apply LCS methods to extract the organizing structure of the ocean currents in the Southwestern Atlantic, where the Malvinas Current (MC) flows. Surface Lagrangian dynamics, as resolved by satellite altimetry data, are interpreted together with trajectories of surface drifting buoys from a deployment of unprecedented dimensions for the region and ocean color imagery. The main finding of this multidata approach is that the MC is structured as a time‐varying system of multiple Lagrangian jets. These structures are found to be modulated by trapped topographic waves characteristic of synoptic timescales. A minimal model of the MC associates upwelling to these jets, which suggests potential implications for primary productivity in the region. Key Points: Original evidence derived from a dedicated drifter experiment characterizes the Malvinas Current as a system of multiple Lagrangian jetsThe longitudinal position of the jets are modulated by trapped topographic waves propagating along the currentOcean color suggests upwelling along the jets, consistent with arrested topographic wave dynamics [ABSTRACT FROM AUTHOR]

Submesoscale processes significantly influence the air‐sea interaction, heat budget and the distribution of physical and biogeochemical tracers in the upper‐ocean. We study the spatiotemporal characteristics and generation mechanisms of submesoscale vertical heat transport (SVHT) at the Kuroshio Extension using a submesoscale‐permitting simulation. Compared with the commonly used Boxcar and Hanning filters, the clean‐cut feature of the Butterworth filter in the wavenumber domain makes it a proper filter to diagnose SVHT. SVHT is systematically upward, peaking in winter. Through causality analysis, we find that, among the basic factors (mixed layer depth, strain rate, surface wind stress, and horizontal buoyancy gradient) from the conventional submesoscale generation mechanism scalings, mixed layer depth plays the leading role in modulating the intraseasonal variation of SVHT. Using the budget of submesoscale temperature variance and causality analysis, we find that advection also plays an important role in regulating SVHT. This work suggests that the choice of appropriate spatial filter is important for SVHT diagnosis and including advection may help improve submesoscale parameterization schemes. Plain Language Summary: Ocean currents with horizontal spatial scales of O(0.1–10) km and temporal scales of hours‐days are defined as submesoscale processes. Submesoscale processes are characterized by large vertical velocity, driving significant vertical heat transport. In this study, we investigate the spatiotemporal features of submesoscale vertical heat transport (SVHT) and the corresponding mechanisms in the Kuroshio Extension region using a high‐resolution numerical simulation. We find that the diagnostics of SVHT is sensitive to the extraction method of submesoscale processes based on spatial scales. SVHT is systematically upward with pronounced seasonal variability, reaching its peak in winter. The intraseasonal variation of SVHT is controlled by multiple factors simultaneously, among which the mixed layer depth plays the most important role. Advection also has influence on SVHT variability. This study offers a better understanding of the dynamic mechanisms driving SVHT, while also highlights the importance of proper filter selection in SVHT diagnostics. Key Points: The estimation of submesoscale vertical heat transport is sensitive to the choice of spatial filterAmong the conventional factors, mixed layer depth is the top regulator of the submesoscale vertical heat transport intraseasonal variationThe advection process can also modulate the intraseasonal variability of submesoscale vertical heat transport [ABSTRACT FROM AUTHOR]

Few observational platforms are able to sustain direct measurements of all the key variables needed in the bulk calculation of air‐sea carbon dioxide (CO2) exchange, a capability newly established for some Uncrewed Surface Vehicles (USVs). Western boundary currents are particularly challenging observational regions due to strong variability and dangerous sea states but are also known hot spots for CO2 uptake, making air‐sea exchange quantification in this region both difficult and important. Here, we present new observations collected by Saildrone USVs in the Gulf Stream during the winters of 2019 and 2022. We compared Saildrone data across co‐located vehicles and against the Pioneer Array moorings to validate the data quality. We explored how CO2 flux estimates differ when all variables needed to calculate fluxes from the bulk formulas are simultaneously measured on the same platform, relative to the situation where in situ observations must be combined with publicly‐available data products. We systematically replaced variables in the bulk formula with those often used for local and regional flux estimates. The analysis revealed that when using the ERA‐5 reanalysis wind speed in place of in situ observations, the ocean uptake of CO2 is underestimated by 8%; this underestimate grows to 9% if the NOAA Marine Boundary Layer atmospheric CO2 product and ERA‐5 significant wave height are also used in place of in situ observations. Overall our findings point to the importance of collecting contemporaneous observations of wind speed and ocean pCO2 to reduce biases in estimates of regional CO2 flux, especially during high wind events. Plain Language Summary: The North Atlantic Ocean absorbs a large amount of carbon dioxide (CO2) from the atmosphere. The ocean CO2 uptake mainly occurs during the winter months in a region where a swift ocean current, called the Gulf Stream, carries warm waters from the tropics to northern latitudes. Understanding how much CO2 this ocean region absorbs is important for constraining global scale assessments of the sources and sinks of CO2. In this paper, we reflect on the methods that are typically used to calculate the exchange of CO2 between the ocean and atmosphere. Using new data collected by uncrewed surface vehicles, that resemble small sailboats, in the North Atlantic Ocean in the vicinity of the Gulf Stream, we find that the estimate of the exchange of CO2 is larger when directly measured wind speeds are used in the calculation in comparison to wind speeds from a widely used data product. This result signifies the importance of co‐located sensors on the same observing platform. Key Points: Compared to Saildrone wind speeds, the ERA‐5 reanalysis appears to underestimate the highest wind speed events (>10 m s−1)Co‐located ocean pCO2 and wind speed observations results in larger uptake of CO2 in this region by 9%Using a sea‐state dependent gas transfer velocity leads to a 28% greater ocean uptake of CO2 compared to using a wind‐only equation [ABSTRACT FROM AUTHOR]

Typhoons are strong natural events that significantly influence the marine environment. In 2018, Typhoon Mangkhut traveled over a moored station with a depth ~1900 m on continental slope in the northern South China Sea, the near-inertial oceanic responses are studied based on the Regional Ocean Modeling System (ROMS) model simulation combined with observation data. Near-inertial currents after Mangkhut can be divided into three layers: near-circular polarized in upper ocean, across-slope polarized in deep ocean and along-slope polarized near the bottom, thickness of the three layers depend on the slope steepness. According to across-slope and along-slope intensified currents, the near-bottom vertical velocities and near-inertial energy were intensified at the moored station. The across-slope forth/back near-inertial flows brought cold/warm and salty/fresh water from deeper/shallower depth, increased vertical excursions of near-bottom temperature/salinity isolines and near-inertial available potential energy. The near-inertial barotropic across-slope currents were much greater than along-slope currents, with net cooling and salinity increase of the whole water column at the moored station. The core responses to Mangkhut were within 100 km around the station. The near-inertial kinetic energy generated both at sea surface and bottom slope, then propagated vertically into ocean interior and horizontally into the South China Sea basin as well as some topography-trapped waves propagated along the slope. This work enriches the understanding of air–sea interactions in coastal regions and the effect of ocean topography, especially after a typhoon.

The article in the Limnology & Oceanography Bulletin commemorates the life and work of William (Bill) M. Hamner, a pioneering ethologist known for his innovative studies of avian and aquatic organisms, particularly gelatinous zooplankton in the world's oceans. Bill's unconventional approach to marine science led him to explore pelagic animals in novel ways, moving beyond traditional research methods. Throughout his career, he made significant contributions to marine biology, inspiring others to study open-ocean plankton using SCUBA diving techniques. Bill's diverse scientific interests and collaborative spirit left a lasting impact on the field, earning him recognition and accolades for his groundbreaking work. [Extracted from the article]

Despite the significant socioeconomic implications in the link between atmospheric waviness and extreme weather events, future atmospheric waviness trends remain elusive due to uncertainties arising from diverse definitions and insufficient dynamical formalism in existing metrics. This study employs a local wave activity (LWA) metric, whose prognostic equation links wave activity changes to forcing mechanisms, to assess wintertime Northern Hemisphere waviness in ERA5 and HighResMIP data sets. The models generally exhibit high fidelity in reproducing observed waviness, while biases stem primarily from biases in the LWA source, low‐level meridional heat flux, which tend to improve with higher resolutions. Future projections exhibit reduction in LWA, primarily due to suppressed LWA generation, which is mitigated by higher‐resolution models. We found that both biases and reduction of the LWA source are closely associated with sensible heat fluxes from the ocean to the atmosphere, highlighting the potential impacts of resolving ocean currents. Plain Language Summary: This study investigates atmospheric waviness in the Northern Hemisphere during winter, using a measure called local wave activity, which enables identifying causes behind waviness changes. Applying this metric to various climate models with different resolutions and a reanalysis data set, we found that historical simulations by the models generally well capture the observed climatological waviness. Biases are found over Europe and mid‐latitudes in Eurasia and the Pacific, which generally improve with higher‐resolution models. In the future simulation, reduction in waviness over much of the Northern Hemisphere, especially in the Atlantic and Pacific sectors, due to a decreased waviness source is found. Higher‐resolution models mitigate this reduction over North Atlantic. Our findings emphasize the connection between waviness and heat given from the ocean to the atmosphere, highlighting the importance of higher ocean resolution for accurate future waviness projections. This study underscores the significant role of the ocean in shaping atmospheric waviness and its implications for climate predictions. Key Points: Biases in Northern Hemisphere wintertime climatological waviness in historical runs are mostly ameliorated with high‐resolution modelsFuture Northern Hemisphere winter waviness will undergo a general reduction, which is mitigated by high‐resolution models over North AtlanticSensible heat fluxes play a crucial role in both historical biases and future reductions in waviness, highlighting the key role of the ocean [ABSTRACT FROM AUTHOR]

Dimethyl sulfur compounds including dimethylsulfoniopropionate (DMSP), dimethyl sulfide (DMS), and dimethyl sulfoxide (DMSO), play a crucial part in global sulfur cycling. The eastern Indian Ocean (EIO), characterized by its remarkable diversity of biomes and climate dynamics, is integral to global climate regulation. However, the regulation mechanism of DMS (P, O) in the EIO remains to be elucidated in detail. This paper presented a field survey aimed at investigating the spatial distribution of DMS (P, O) and their relationships with environmental and biological factors in the EIO. The surface concentrations of DMS, DMSPt, and DMSOt varied from 0.07 to 7.37 nmol/L, 0.14 to 9.17 nmol/L, and 0.15 to 3.32 nmol/L, respectively, and their distributions are attributed to high Chl-a concentration near Sri Lanka and the influence of ocean currents (Wyrtki jets, Bay of Bengal runoff). Higher concentrations of DMS (P) and DMSOt were predominantly observed in water columns shallower than 75m and deeper than 75m deep, respectively. The monthly DMS fluxes in the study area peaked in August. Temperature and Dissolved Silica Index (DSI) were the key environmental determinants for DMS distribution, while nitrate (NO3-) was the primary factor for both DMSPt and DMSOt. In terms of biological factors, Prochlorococcus and Synechococcus were significant contributors to DMS (P, O) dynamics. Synechococcus was the dominant influence on the DMS source and DMSPt sink, whereas Prochlorococcus primarily consumed DMSOt. Furthermore, the structural equation modeling (SEM) revealed the relationship between DMS, DMSPt, DMSOt, and the key environmental/biological factors, as well as among them, and together they formed a co-regulatory network in the EIO. This contributes significantly to the advancement of global ecosystem models for DMS (P, O). [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a heterogeneously distributed toxicant affecting wildlife and human health. Yet, the spatial distribution of Hg remains poorly documented, especially in food webs, even though this knowledge is essential to assess large-scale risk of toxicity for the biota and human populations. Here, we used seabirds to assess, at an unprecedented population and geographic magnitude and high resolution, the spatial distribution of Hg in North Atlantic marine food webs. To this end, we combined tracking data of 837 seabirds from seven different species and 27 breeding colonies located across the North Atlantic and Atlantic Arctic together with Hg analyses in feathers representing individual seabird contamination based on their winter distribution. Our results highlight an east-west gradient in Hg concentrations with hot spots around southern Greenland and the east coast of Canada and a cold spot in the Barents and Kara Seas. We hypothesize that those gradients are influenced by eastern (Norwegian Atlantic Current and West Spitsbergen Current) and western (East Greenland Current) oceanic currents and melting of the Greenland Ice Sheet. By tracking spatial Hg contamination in marine ecosystems and through the identification of areas at risk of Hg toxicity, this study provides essential knowledge for international decisions about where the regulation of pollutants should be prioritized. [ABSTRACT FROM AUTHOR]

Topographic Rossby waves (TRWs) dominate the low-frequency variability of deep ocean currents and play a crucial role in energy exchange and material mixing. On the continental slope of the southwestern South China Sea, a deep-water mooring was deployed to observe TRWs for a period of ~ 40 days. The TRWs, with a wavelength of 109 km, account for 41.3% of the subinertial variations. A ray-tracing model was applied to investigate the propagation and energy source. The results showed that the TRWs propagated from the northeast of the mooring location and were most likely caused by the mesoscale eddy disturbances off the Vietnam coast. This study provides a new perspective on examining the impact of mesoscale eddies off Vietnam on abyssal currents. [ABSTRACT FROM AUTHOR]

The ice streams flowing into the Amundsen Sea, West Antarctica, are losing mass due to changes in oceanic basal melting of their floating ice shelves. Rapid ice‐shelf melting is sustained by the delivery of warm Circumpolar Deep Water to the ice‐shelf cavities, which is first supplied to the continental shelf by an undercurrent that flows eastward along the shelf break. Temporal variability of this undercurrent controls ice‐shelf basal melt variability. Recent work shows that on decadal timescales the undercurrent variability opposes surface wind variability. Using a regional model, we show that undercurrent variability is induced by sea‐ice freshwater fluxes, particularly those north of the shelf break, which affect the cross‐shelf break density gradient. This sea‐ice variability is linked to tropical Pacific variability impacting atmospheric conditions over the Amundsen Sea. Ice‐shelf melting also feeds back onto the undercurrent by affecting the on‐shelf density, thereby influencing shelf‐break density gradient anomalies. Plain Language Summary: The glaciers that flow toward the Amundsen Sea, West Antarctica, are losing ice faster than most others about the continent. Once these glaciers reach the coast, they extend out onto the ocean surface, forming ice shelves. The rapid loss of ice is caused by changes in melting by relatively warm ocean waters beneath the floating ice shelves. In the Amundsen Sea, a deep ocean current is responsible for delivering warm water from the deep ocean to the ice shelves. We present model results that show that this deep current varies on decadal timescales as a consequence of systematic sea‐ice melt and formation patterns. A faster current drives more rapid ice shelf melting which, via a feedback process, further accelerates the current. Climate variability originating in the tropical Pacific Ocean is responsible for the variability in the sea‐ice, and is therefore also responsible for the effects on melting of the ice shelves. Key Points: In the Amundsen Sea decadal variability of an undercurrent flowing along the shelf break drives decadal variability in ice‐shelf basal meltSea‐ice freshwater fluxes and positive feedbacks from ice‐shelf basal melt drive the undercurrent variabilityTropical Pacific teleconnections induce atmospheric anomalies over the Amundsen Sea which drive the sea‐ice freshwater flux variability [ABSTRACT FROM AUTHOR]

Accurate prediction of ocean surface currents is important for marine safety, ship routing, tracking of pollutants and in coupled forecasting. Presently, velocity observations are not routinely assimilated in global ocean forecasting systems, largely due to the sparsity of the observation network. Several satellite missions are now being proposed with the capability to measure Total Surface Current Velocities (TSCV). If successful, these would substantially increase the coverage of ocean current observations and could improve accuracy of ocean current forecasts through data assimilation. In this paper, Observing System Simulation Experiments (OSSEs) are used to assess the impact of assimilating TSCV in the Met Office's global ocean forecasting system. Synthetic observations are generated from a high-resolution model run for all standard observation types (sea surface temperature, profiles of temperature and salinity, sea level anomaly and sea ice concentration) as well as TSCV observations from a Sea surface KInematics Multiscale monitoring (SKIM) like satellite. The assimilation of SKIM like TSCV observations is tested over an 11 month period. Preliminary experiments assimilating idealised single TSCV observations demonstrate that ageostrophic velocity corrections are not well retained in the model. We propose a method for improving ageostrophic currents through TSCV assimilation by initialising Near Inertial Oscillations with a rotated incremental analysis update (IAU) scheme. The OSSEs show that TSCV assimilation has the potential to significantly improve the prediction of velocities, particularly in the Western Boundary Currents, Antarctic Circumpolar Current and in the near surface equatorial currents. For global surface velocity the analysis root-mean-squareerrors (RMSEs) are reduced by 23% and there is a 4-day gain in forecast RMSE. There are some degradations to the subsurface in the tropics, generally in regions with complex vertical salinity structures. However, outside of the tropics, improvements are seen to velocities throughout the water column. Globally there are also improvements to temperature and sea surface height when TSCV are assimilated. The TSCV assimilation largely corrects the geostrophic ocean currents, but results using the rotated IAU method show that the energy at inertial frequencies can be improved with this method. Overall, the experiments demonstrate significant potential benefit of assimilating TSCV observations in a global ocean forecasting system. [ABSTRACT FROM AUTHOR]

Aim: Plants distributed between southern Taiwan and the north of the Philippines are spread among numerous small islands in an area crossed by the powerful Kuroshio current. Oceanic currents can be effective seed-dispersal agents for coastal plant species. Moreover, the Luzon Strait is an area prone to tropical cyclones. The aim of this study is to look at the dispersal capability of an endangered coastal plant species, the Mearns fig (Ficus pedunculosa var. mearnsii), using both experimental and population genetics methods. Location: Southern Taiwan, the Philippines, and the islands between Luzon and Taiwan Island. Methods: This study combined two types of analysis, i.e., buoyancy experiments on syconia and double digest restriction-associated DNA sequencing (ddRAD), to analyze the population genetics of the Mearns fig. Results: We first discovered that mature Mearns fig syconia could float in seawater. They have a mean float duration of 10 days to a maximum of 21 days. Germination rates varied significantly between Mearns fig seeds that had undergone different durations of flotation treatment. Population genetic analysis shows a high degree of inbreeding among various Mearns fig populations. Moreover, no isolation by distance was found between the populations and individuals. Main conclusions: From our analysis of the genetic structure of the Mearns fig populations, we can clearly highlight the effect of the Kuroshio oceanic current on the seed dispersal of this fig tree. Comprehensive analysis has shown that Mearns fig seeds are still viable before the mature syconium sinks into the seawater, and so they could use the Kuroshio Current to float to the current population locations in Taiwan. [ABSTRACT FROM AUTHOR]

The purpose of this study is to design a Swarm Control algorithm for the effective mission performance of multiple unmanned surface vehicles (USVs) used for marine research purposes at sea. For this purpose, external force information was utilized for the control of multiple USV swarms using a lead–follow-formation technique. At this time, to efficiently control multiple USVs, the LSTM algorithm was used to learn ocean currents. Then, the predicted ocean currents were used to control USVs, and a study was conducted on behavioral-based control to manage USV formation. In this study, a control system model for several USVs, each equipped with two rear thrusters and a front lateral thruster, was designed. The LSTM algorithm was trained using historical ocean current data to predict the velocity of subsequent ocean currents. These predictions were subsequently utilized as system disturbances to adjust the controller's thrust. To measure ocean currents at sea as each USV moves, velocity, azimuth, and position data (latitude, longitude) from the GPS units mounted on the USVs were utilized to determine the speed and direction of the hull's movement. Furthermore, the flow rate was measured using a flow rate sensor on a small USV. The movement and position of the USV were regulated using an Artificial Neural Network-PID (ANN-PID) controller. Subsequently, this study involved a comparative analysis between the results obtained from the designed USV model and those simulated, encompassing the behavioral control rules of the USV swarm and the path traced by the actual USV swarm at sea. The effectiveness of the USV mathematical model and behavior control rules were verified. Through a comparison of the movement paths of the swarm USV with and without the disturbance learning algorithm and the ANN-PID control algorithm applied to the designed simulator, we analyzed the position error and maintenance performance of the swarm formation. Subsequently, we compared the application results. [ABSTRACT FROM AUTHOR]

Deep-sea mining inevitably produces plumes, which will pose a serious threat to the marine environment with the continuous movement and diffusion of plumes along with ocean currents. The terminal settling velocity (wt) of irregular particles is one of the crucial factors for determining the plumes' diffusion range. It is generally calculated by drag coefficient (CD), while most existing CD models only consider single shape characteristic parameter or have a smaller range of Reynolds number (Re). In this study, a new shape factor (γ) of irregular particles is proposed by considering the thickness (one-dimension), the projected area (two-dimension), and the surface area (three-dimension) of irregular particles as well as their coupling effect to establish a modified CD model for calculating the wt. A modified Gaussian plume model is proposed to predict the horizontal diffusion distance of the plume particles by considering the settling velocity and diffusion effect of irregular particles. Research results show that the wt increases nearly linearly, with a gradually decreased slope and slightly then greatly with the increasing of γ, dp (diameter) and ρp (density), respectively. The modified CD model is verified to be more valid with a wider application range (Re < 3×105) than five existing CD models by the test results. The larger the ρp or dp, the larger the wt and thus the smaller the Sh. This study could provide a theoretical basis for calculating the plume diffusion range to further study the impact of deep-sea mining on the ocean environment. [ABSTRACT FROM AUTHOR]

Ocean currents play a role in both facilitating and impeding connectivity of marine organisms' populations, serving as key drivers and potential barriers. The emergence of Taiwan around five million years ago (Mya) impacted the Kuroshio Current which later shaped the distribution of marine organisms. In this study, we examined how the Kuroshio Current influenced the distribution and population divergence of the marine red alga Dichotomaria elegans (Galaxauraceae, Nemaliales). Through phylogenetic analysis, species delimitation, and morphological comparison of Taiwanese species, we determined its phylogenetic position relative to other species within the D. marginata complex of the genus Dichotomaria. We uncovered the hidden cryptic diversity within the D. marginata complex in Taiwan and proposed the new combinations D. elegans and D. latifolia based on Galaxaura elegans and G. latifolia. Genetic analysis based on three loci (mitochondrial cox2-3 and cox1, and plastid rbcL) from 32 locations across the Philippines, Taiwan, and Japan revealed three allopatric lineages within D. elegans. The first lineage is restricted to the northern Philippines and southern Taiwan, while the second has a broader latitudinal range along the Kuroshio Current. The third lineage is found in southeast Luzon, Philippines, close to the bifurcation of the North Equatorial Current, near the start of the Kuroshio Current. The divergence of the first two lineages during the mid-Pliocene (~3.7 Mya) coincided with the emergence of Taiwan, with the current dynamics accentuating their separation. The Kuroshio Current exhibited a dual impact on the biogeography of D. elegans: promoting the dispersal of the second lineage towards higher latitudes and preventing the first lineage from moving northward. Principal component analysis showed that habitat conditions and morphologies differed between the two D. elegans lineages. This study provides insights into the cryptic diversity of Dichotomaria in Taiwan, as well as the genetic divergence, biogeographical patterns, and ecological associations of D. elegans, highlighting the interplay of island formation and currents shaping the diversification of seaweeds in the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

Knowledge of near-bottom ocean current velocities and especially their extreme values is necessary to understand geomorphology of the seafloor and composition of benthic biological communities and quantify mechanical energy dissipation by bottom drag. Direct measurements of near-bottom currents in deep ocean remain scarce because of logistical challenges. Here, we report the results of flow velocity and pressure fluctuation measurements at three sites with depths of 2573–4443 m in the area where the Gulf Stream interacts with the New England Seamounts. Repeated episodes of unexpectedly strong near-bottom currents were observed, with the current speed at 4443 m of more than 0.40 m/s. At 2573 m, current speeds exceeded 0.20 m/s approximately 5% of the time throughout the entire eight-week measurement period. The maximum flow speeds of over 1.10 m/s recorded at this site significantly surpass the fastest previously reported directly measured current speeds at comparable or larger depths. A strong correlation is found between the noise intensity in the infrasonic band and the measured current speed. The noise intensity and the characteristic frequency increase with the increasing current speed. Machine-learning tools are employed to infer current speeds from flow-noise measurements at the site not equipped with a current meter. [ABSTRACT FROM AUTHOR]

Southeastern Australia's marine waters are notably warming, surpassing global averages. This region has emerged as a strategic location for researching planktic microfossils, particularly dinoflagellate cysts, in modern and Late Quaternary sediments, offering crucial insights into the biophysical properties of mid-latitude waters. This study examined cyst distribution in marine sediment cores near Maria Island, Tasmania, southeastern Australia, up to 9000 years before present (kyrs BP). Dominant cysts included Protoceratium reticulatum, Protoperidinium spp. (P. avellana, P. conicum, P. oblongum, P. subinerme, P. shanghaiense), and Spiniferites spp. (S. bulloideus, S. hyperacanthus, S. membranaceus, S. mirabilis, S. pachydermus, and S. ramosus). Inshore, Spiniferites spp. constituted a higher proportion (up to 61%), while offshore was dominated by P. reticulatum (up to 80%). Impagidinium spp. and Nematosphaeropsis labyrinthus were exclusively found offshore and displayed increased abundance from ∼6 kyrs BP, suggesting a shift from a shallow to a deep-water habitat. Alexandrium tamarense species complex cysts were present over 140 years inshore and approaching 9 kyrs BP offshore, indicating a longstanding endemic presence. Gymnodinium catenatum cysts were detected exclusively inshore from ∼50 years ago, indicating a relatively recent bloom phenomenon. The East Australian Current's limited southward reach is suggested by the absence of the warm-water cyst-producing taxon Lingulodinium polyedra. Similarly, the non-detection of the cold-water species Spiniferites antarctica and Impagidinium pallidum reflects Subtropical Front boundaries against subantarctic incursions from the south. In contrast to coccolithophores in the same core, no noticeable shift from cold to warm-water dinoflagellate cyst species was observed. This documentation of dinoflagellate cysts aids in predicting environmental impacts on local communities and beyond. [ABSTRACT FROM AUTHOR]

Knowledge of functional dispersal barriers in the marine environment can be used to inform a wide variety of management actions, such as marine spatial planning, restoration efforts, fisheries regulations, and invasive species management. Locations and causes of dispersal barriers can be studied through various methods, including movement tracking, biophysical modeling, demographic models, and genetics. Combining methods illustrating potential dispersal, such as biophysical modeling, with realized dispersal through, e.g., genetic connectivity estimates, provides particularly useful information for teasing apart potential causes of observed barriers. In this study, we focus on blue mussels (Mytilus edulis) in the Skagerrak—a marginal sea connected to the North Sea in Northern Europe—and combine biophysical models of larval dispersal with genomic data to infer locations and causes of dispersal barriers in the area. Results from both methods agree; patterns of ocean currents are a major structuring factor in the area. We find a complex pattern of source‐sink dynamics with several dispersal barriers and show that some areas can be isolated despite an overall high dispersal capability. Finally, we translate our finding into management advice that can be used to sustainably manage this ecologically and economically important species in the future. [ABSTRACT FROM AUTHOR]

We propose a method to reconstruct sea surface height anomalies (SSHA) from vector surface currents and winds. This analysis is motivated by the proposed satellite ODYSEA, which is a Doppler scatterometer that measures coincident surface vector winds and currents. If it is feasible to estimate SSHA from these measurements, then ODYSEA could provide collocated fields of SSHA, currents, and winds over a projected wide swath of ∼1700 km. The reconstruction also yields estimates of the low-frequency surface geostrophic, Ekman, irrotational, and nondivergent current components and a framework for separation of balanced and unbalanced motions. The reconstruction is based on a steady-state surface momentum budget including the Ekman drift, Coriolis acceleration, and horizontal advection. The horizontal SSHA gradient is obtained as a residual of these terms, and the unknown SSHA is solved for using a Helmholtz–Hodge decomposition given an imposed SSHA boundary condition. We develop the reconstruction using surface currents, winds, and SSHA off the U.S. West Coast from a 43-day coupled ROMS–WRF simulation. We also consider how simulated ODYSEA measurement and sampling errors and boundary condition uncertainties impact reconstruction accuracy. We find that temporal smoothing of the currents for periods of 150 h is necessary to mitigate large reconstruction errors associated with unbalanced near-inertial motions. For the most realistic case of projected ODYSEA measurement noise and temporal sampling, the reconstructed SSHA fields have an RMS error of 2.1 cm and a model skill (squared correlation) of 0.958 with 150-h resolution. We conclude that an accurate SSHA reconstruction is feasible using information measured by ODYSEA and external SSHA boundary conditions. [ABSTRACT FROM AUTHOR]

The fish anchor is an economically viable offshore foundation engineering technology that has been proposed in recent years. By fish anchor, we mean a fish-shaped dynamically installed anchor that can penetrate into the seabed through water by its own weight. However, the existing research studies seldom consider the hydrodynamic characteristics of its free fall installation, resulting in uncertainties regarding its underwater installation characteristics. Therefore, based on OpenFOAM, this study first investigated the directional stability of fish anchors during its underwater falling process through the static model analysis method and dynamic model analysis method. The findings indicated that the directional stability of fish anchors was insufficient, rendering them suitable only for release and installation at low heights (i.e., less than 4.2 times the anchor length) without marine environmental loads. Furthermore, the anchor inclination angle during installation is significant, thereby impacting its penetration depth and pull-out capacity in the seabed. To solve this problem, the concept of an innovative booster-assisted fish anchor is proposed, which can significantly enhance the directional stability of conventional fish anchors. Results show that the maximum installation height of the new booster-assisted fish anchor is increased by 2.4 times compared to the original design, thereby enhancing both the penetration speed and uplift capacity. Based on the findings, recommended installation and construction conditions are provided. Finally, a predictive formula for the installation height and verticality of the new booster-assisted fish anchor under current action is presented to offer guidance for engineering applications. [ABSTRACT FROM AUTHOR]

The Central Bengkulu Regency possesses a coastline measuring 21.8 km, situated in direct proximity to the Indian Ocean. The heightened wave and ocean current dynamics possess the capacity to induce detrimental effects in the form of coastal abrasion along the coastline. This study conducted an examination of the rate of shoreline changes resulting from coastal abrasion in Central Bengkulu Regency, Bengkulu, Indonesia. Horizontal-to-vertical spectral ratio (HVSR) analysis, multichannel analysis of surface waves (MASW), and Landsat-8 remote sensing were all used in the current investigation. The project gets started with conducting field investigations and measurements of geophysical techniques, including the collection of Landsat-8 satellite imagery spanning the period from 1990 to 2020. Additionally, an examination was conducted on the rate at which the shoreline undergoes changes in velocity. In order to determine the increase in change that occurs along coastlines over a period of several decades, a study was carried out during which Landsat-8 satellite images were analyzed. This study investigates the application of the HVSR technique for assessing the seismic vulnerability of the ground and, additionally, the MASW technique for measuring the shear wave velocity of the coastline's soil. Both of these methodologies are compared and contrasted with one another in this research. The findings indicated that the mean pace of coastline change in Central Bengkulu Regency was 1.5 m/yr, with the maximum velocity recorded at 4.1 m/yr. This high velocity of shoreline change is correlated with the Vs30 value of MASW measurement and Kg of HVSR measurement, where the subsurface soil structure along the coast of Central Bengkulu Regency from Vs30 measurement shows that it is dominated by stiff soil structure that is susceptible to erosion. Outcomes from the study can inform decision-making processes about safeguards and preventative measures to prevent further coastal degradation. [ABSTRACT FROM AUTHOR]

Nguyen, T.H.T., 2024. A review of marine debris research in Vietnam. Journal of Coastal Research, 40(3), 588–597. Charlotte (North Carolina), ISSN 0749-0208. Being considered one of the biggest contributors of marine debris in the world, Vietnam issued a National Action Plan in 2019 that committed to reducing plastic waste in the sea and ocean by 75% by 2030. This present study reviewed the current state of knowledge on marine debris research and management in Vietnam and aimed to support an overall picture of data in order to help deal with the marine pollution problem. According to the records gathered, the research on marine pollution over time in Vietnam has increased, from 8 manuscripts in 2019 to 22 manuscripts in 2022. Study results also showed that there are prepossessions in current research on debris properties, such as predilection for plastic type or fiber and fragment shapes, leaning toward certain environmental compartments (like beaches and floating systems), and favor toward the study area. There is a geographical trend of research being conducted in four main regions in Vietnam (the Red River Delta, Da Nang, Nha Trang, and the Mekong River Delta). The gaps and limits of current marine debris research in Vietnam are also discussed, and avenues for future research are proposed, which are intended to be helpful for both academic and management efforts. [ABSTRACT FROM AUTHOR]

Premise: Quaternary climatic fluctuations and long‐distance seed dispersal across the sea are critical factors affecting the distribution of coastal plants, but the spatiotemporal nature of population expansion and distribution change of East Asian coastal plants during this period are rarely examined. To explore this process, we investigated the genome‐wide phylogenetic patterns of Euphorbia jolkinii Boiss. (Euphorbiaceae), which grows widely on littoral areas of Japan, Korea, and Taiwan. Methods: We used plastome sequences and genome‐wide single nucleotide polymorphisms in samples across the species range to reveal phylogeographic patterns and spatiotemporal distributional changes. We conducted ecological niche modeling for the present and the last glacial maximum (LGM). Results: Genetic differentiation was observed between the northern and southern populations of E. jolkinii, separated by the major biogeographic boundary, the Tokara Gap. These two groups of populations differentiated during the glacial period and subsequently intermingled in the intermorainic areas of the central Ryukyu Islands after the LGM. Ecological niche models suggested that the potential range of E. jolkinii was restricted to southern Kyushu; however, it was widespread in the southern Ryukyu Islands and Taiwan during the LGM. Conclusions: This study provides evidence of genetic differentiation among coastal plant populations separated by the prominent biogeographical boundary. Although coastal plants are typically expected to maintain population connectivity through sea‐drifted seed dispersal, our findings suggest that genetic differences may arise because of a combination of limited gene flow and changes in climate during the glacial period. [ABSTRACT FROM AUTHOR]

Underwater Wireless Sensors Networks (UWSNs) are deployed in remotely monitored environment such as water level monitoring, ocean current identification, oil detection, habitat monitoring and numerous military applications. Providing scalable and efficient routing is very challenging in UWSNs due to the harsh underwater environment. The biggest difficulties are the nodes inherent movement due to water current, long delay in data transmission, low bandwidth of the acoustic signal, high error rate and energy scarcity in battery powered nodes. Many routing protocols have been proposed to solve the aforementioned problems. There are three broad categories of routing protocols namely depth based, energy based and vector-based routing. Vector Based Forwarding protocols perform routing through virtual pipeline by defining their radius which give proper direction to packets communication. We proposed a routing protocol termed as Path-Oriented Energy Scaled Expanded Vector Based Forwarding (PESEVBF). PESEVBF takes into account all parameters; holding time, the source nodes packets routing path and void holes creation on the second hop; PESEVBF not only considers the packet upward advancement but also focus on density of the forwarded nodes in terms of number of potential forwarding and suppressed nodes for path selection. Node selection in resultant holding time is based on minimum Path Factor (PF) value. Moreover, the suppressed node will be selected for packet forwarding to avoid the void holes occurrences on the second hop. Performance of PESEVBF is compared with other routing protocols using matrices such as energy consumption, packet delivery ratio, packets dropping ratio and duplicate packets creation indicating considerable performance improvement. [ABSTRACT FROM AUTHOR]

The blue economy approach to ocean governance promises environmentally sustainable, economically viable, and socially equitable ocean-based economic growth. However, the blue economy has been inconsistently defined, interpreted, and applied, often leading to incompatibilities between the blue economy approach and existing ocean policies. We explore the blue economy in the Republic of Panama, where recent government commitments include designing and implementing a blue economy approach to ocean sector development. We use qualitative text analysis and a policy coherence assessment to examine the consistency of objectives across existing ocean policies in Panama and their compatibility with broader blue economy goals. Our results indicate that Panama's existing ocean policies address some blue economy goals but also reveal how policy coherence assessments and precise deliberation can inform a more contextually sensitive blue economy approach that aligns with existing ocean policies while also adding value to ocean governance and better integrating blue economy objectives. Findings suggest that Panama's existing ocean policies could better address social, environmental, and resource use objectives, without disregarding the need to reinforce economic and governance goals; elevating social objectives, especially social equity, can truly differentiate Panama's blue economy fromits current ocean governance approach. Finally, while we acknowledge that greater policy coherence can potentially increase the likelihood of attaining policy objectives, our findings show that coherence alone does not ensure their realization in practice. Our study contributes to blue economy scholarship by providing the first Latin America-based case study using policy coherence to assess compatibilities between existing ocean policies and a blue economy. Other countries seeking to transition to a blue economy could use our findings to inform the design of their approach and its integration with their existing ocean policy frameworks. [ABSTRACT FROM AUTHOR]

Baffin Bay is the travel destination of most icebergs calving from west Greenland. They commonly follow the bay's cyclonic circulation and might end up far south along the coast of Newfoundland and Labrador, where many shipping routes converge. Given the hazard that icebergs pose to marine transportation, understanding their distribution is fundamental. One of the forces driving iceberg drift arises from the presence of sea ice. Observations in the Southern Ocean indicate that icebergs get locked in thick and concentrated sea ice. We present observations that support the occurrence of this sea ice locking mechanism (SIL) in Baffin Bay as well. Most iceberg models, however, represent the sea ice force over an iceberg as a simple drag force. Here, we implement a new parameterization in the iceberg module of the Nucleus for European Modeling of the Ocean (NEMO‐ICB) to represent SIL. We show that, by using this new parameterization, icebergs are more likely to travel outside of the Baffin Island Current during winter, which is supported by satellite observations. There is a slight improvement in the representation of iceberg severity along the coast of Newfoundland and Labrador and a slight shift of iceberg melt toward this region and Lancaster Sound/Hudson Strait. Although the impacts of icebergs on sea ice are still not represented, and targeted observations are needed for model calibration regarding sea ice concentration thresholds from which icebergs get locked, we are confident that this model improvement takes iceberg modeling one step forward toward reality. Plain Language Summary: After they break off Greenland's glaciers, icebergs drift in the ocean in somewhat predictable patterns across Baffin Bay. What makes them predictable is that we know the main natural forces that cause icebergs to move: the winds, the ocean currents, and the sea ice cover. Because it is impossible to monitor all the icebergs coming from Greenland, we use computer models to understand their typical trajectories. In these models, each one of the forces responsible for iceberg drift can be represented mathematically, usually in a very simplistic way. The sea ice force, for example, is proportional to how much friction there is between the iceberg and sea ice. However, observations in nature show that the iceberg‐sea ice interaction is more complicated than that: if the sea ice cover is thick and compact, it is able to trap icebergs, and both will move as one solid block. In this study, we improve a model's representation of the sea ice force by including this trapping mechanism. Results show that iceberg trajectory can be slightly different during winter due to sea ice trapping and that this mechanism potentially improves our ability to predict when icebergs reach the transatlantic shipping routes east of Canada. Key Points: A new sea ice‐iceberg locking parameterization was implemented in Nucleus for European Modeling of the Ocean and tested in a 1/4° resolution regional configurationIcebergs locked in sea ice in Baffin Bay are more likely to travel outside of the Baffin Island Current than "unlocked" onesThe existence of a sea ice locking mechanism in Baffin Bay is supported by observations of co‐varying iceberg and sea ice speeds [ABSTRACT FROM AUTHOR]

Variability in ocean currents, temperature and salinity drive dynamic sea level (DSL) variability on the Northwest European Shelf (NWES). It is dominated by mass variations, with steric signals relatively small. A mechanistic explanation of how ocean dynamics relates to the mass component of NWES sea level variability is required. We use regional ocean model experiments to isolate sources of variability and then investigate the effect on monthly to‐interannual DSL variability together with the simulated momentum budgets along the shelfbreak. Regional (local) wind and non‐regional (remote) forcing are important on the NWES. For the local wind forcing, the net mass flux onto the shelf, which drives a shelf‐mean mode of DSL variability, results from a combination of surface Ekman, bottom Ekman and geostrophic flows and explains 73% of the variance in transport across the shelf‐edge. The geostrophic flow is closely related to wind stress with a flow about half that of surface Ekman transport but in the opposite direction. For the remotely forced mass‐flux across the shelf‐edge, the geostrophic component explains 62% of the variance and bottom friction plays an important indirect role. The remotely forced variability, while relatively spatially uniform, is more important for explaining DSL variance over the western NWES. This mode of variability is sensitive to signals propagating northward via a thin strip of the southern boundary near the Portuguese coast, consistent with coastal trapped wave signals. It also appears to drive steric height in the Bay of Biscay, which is related to DSL on the shelf. Plain Language Summary: Changes in sea level on the North West European Shelf (NWES) that result from changes in ocean currents, temperature and salinity have many sources. The shelf‐mean sea level changes as the volume of water on the shelf changes. Variations in the amount of water flowing onto the NWES is, consequently, a link between ocean currents and coastal sea level. We run experiments in a regional ocean model that isolate sources of variability. We then investigate the effect on both sea level and the processes that determine ocean currents. Winds redistribute water onto the shelf through Ekman transport. We find that winds also drive water across the shelf‐edge indirectly, and find the volume of water transported across the shelf‐edge in this way is approximately half that due to wind driven Ekman transport, but in the opposite direction. Non‐regional forcing, associated with non‐local winds, modifies the pressure gradient along the shelfbreak and results in changes in the amount of water on the NWES. This remote forcing is associated with density variations in the adjacent ocean. Both the coastal and oceanic sea levels are sensitive to oceanic changes occurring at lower latitudes and which travel northward along the shelfedge. Key Points: Ekman transport is insufficient as a mechanistic description of the wind's effect on coastal sea levelOn monthly to‐interannual timescales regional (local) winds and non‐regional (remote) forcing set‐up a geostrophic flow onto the shelfThe subsequent mass loading onto the shelf sets up a North Atlantic eastern boundary mode of sea level variability [ABSTRACT FROM AUTHOR]

Release of iron (Fe) from continental shelves is a major source of this limiting nutrient for phytoplankton in the open ocean, including productive Eastern Boundary Upwelling Systems. The mechanisms governing the transport and fate of Fe along continental margins remain poorly understood, reflecting interaction of physical and biogeochemical processes that are crudely represented by global ocean biogeochemical models. Here, we use a submesoscale‐permitting physical‐biogeochemical model to investigate processes governing the delivery of shelf‐derived Fe to the open ocean along the northern U.S. West Coast. We find that a significant fraction (∼20%) of the Fe released by sediments on the shelf is transported offshore, fertilizing the broader Northeast Pacific Ocean. This transport is governed by two main pathways that reflect interaction between the wind‐driven ocean circulation and Fe release by low‐oxygen sediments: the first in the surface boundary layer during upwelling events; the second in the bottom boundary layer, associated with pervasive interactions of the poleward California Undercurrent with bottom topography. In the water column interior, transient and standing eddies strengthen offshore transport, counteracting the onshore pull of the mean upwelling circulation. Several hot‐spots of intense Fe delivery to the open ocean are maintained by standing meanders in the mean current and enhanced by transient eddies and seasonal oxygen depletion. Our results highlight the importance of fine‐scale dynamics for the transport of Fe and shelf‐derived elements from continental margins to the open ocean, and the need to improve representation of these processes in biogeochemical models used for climate studies. Plain Language Summary: Iron is an essential nutrient that supports the life of marine organisms. In the ocean, large quantities of iron are released by sediments found along the continents. However, this iron is not very soluble, and it tends to precipitate back to the sediments close to where it is released. In fact, we still struggle to understand how enough of this iron makes its way to the open ocean, where it fertilizes phytoplankton and sustains fisheries. In this study, we use a sophisticated computer simulation of the ocean currents and chemistry of the northern U.S. West Coast to study the transport of iron released along the continent to the open ocean. This computer simulation is able to reproduce the currents observed along the coast with high realism, including small swirls, eddies, and meanders that constantly mix coastal waters with open ocean waters. We found that about one‐fifth of all the iron released by sediments along the coast is transported offshore, where it can sustain the life of marine organisms. This transport from the coast to the open ocean mostly takes place near the surface, reflecting upwelling caused by winds in the summer, and near the bottom, reflecting transport caused by the friction of the poleward California Undercurrent with the seafloor. We also found that episodic swirls, eddies, and meanders reinforce this delivery of iron to the open ocean, in particular along several "hot‐spots" of intense transport along the coast. Our results suggest that global computer simulations used to study how marine ecosystems respond to climate change should improve how they represent small‐scale currents and their effects on the cycle of iron, in particular along the ocean's coastlines. Key Points: Shelf‐to‐basin transport is a major source of iron to the North East Pacific OceanHalf of this transport occurs year‐round by downslope Ekman flow in the bottom boundary layer, sustained by the poleward California UndercurrentRegional hot‐spots of iron transport are sustained by meanders in the poleward undercurrent and local bottom oxygen depletion [ABSTRACT FROM AUTHOR]

Biweekly sea surface temperature (SST) variability significantly contributes to over 50% of the intraseasonal variability in the eastern equatorial Pacific (EEP) and Atlantic (EEA). Our study investigates this biweekly variability, employing a blend of in–situ and reanalysis data sets. The research identifies biweekly signals in SST, meridional wind, and ocean currents, notably in September–November in EEP and June–August in EEA. Biweekly southerly (northerly) winds drive instantaneous northward (southward) ocean currents in EEP, but with a 1–2‐day phase delay in EEA. Consequently, these currents lead to SST anomalies with a 3–4‐day lag in both EEP and EEA due to the presence of the cold tongue. The study reveals the origin of biweekly wind fluctuations in the western Pacific for EEP and the subpolar Pacific for EEA, connected by atmospheric Rossby waves validated through a linearized non‐divergent barotropic model. This research affirms the influence of subtropical and subpolar atmospheric forcing on equatorial SST. Plain Language Summary: Our research focuses on understanding the regular changes in sea surface temperature (SST) occurring every 2 weeks, which significantly contribute to the seasonal variations in the eastern equatorial Pacific (EEP) and Atlantic (EEA). By analyzing a mix of direct and reconstructed data, we uncover the distinct patterns of these biweekly changes in SST, winds, and ocean currents. Our investigation shows that the movements of the ocean currents are closely linked to the shifts in wind direction, affecting the temperature of the ocean waters. Notably, we observe a delay in the relationship between wind and SST in both EEP and EEA. Through our analysis, we establish that the origins of these biweekly wind patterns can be traced to specific regions in the Pacific. Moreover, we identify the role of atmospheric Rossby waves in connecting these wind patterns to their source regions, which helps us understand how changes in atmospheric conditions in different parts of the ocean can impact the equatorial SST. Key Points: Over 50% of intraseasonal SST variability in the eastern equatorial Pacific and Atlantic is attributed to biweekly fluctuationsThe atmospheric winds play a crucial role in driving the biweekly SST variabilityBiweekly winds in the eastern equatorial Pacific and Atlantic stem from the subtropical and subpolar regions, respectively [ABSTRACT FROM AUTHOR]

The article highlights a daring expedition to Antarctica's Canisteo Peninsula, where a team led by Peter Neff, a polar glaciologist, drills ice cores crucial for understanding the precarious state of the Pine Island and Thwaites glaciers. Topics include the urgent need for data on Antarctic coastal climate, the challenges of drilling in remote and stormy locations, and the significance of ice cores in unraveling past and future climate trends in the region.

The climate fluctuations during the Late Pleistocene significantly influenced the phylogeographic structure and historical dynamics of marine fishes in the marginal seas of the western Pacific Ocean. The puffer fish, Lagocephalus spadiceus, holds substantial nutritional and economic value in the South China Sea. To investigate the demographic history and population structure of the L. spadiceus, the mitochondrial DNA COI and Cyt b gene datasets from 300 individuals across eight populations in the South China Sea were sequenced. Our findings revealed high haplotype diversity (0.874 ± 0.013) and low nucleotide diversity (0.00075 ± 0.00058). The phylogenetic tree and haplotype networks revealed no significant genetic differentiation along the northern coast of South China Sea. Neutrality tests, mismatch distribution analyses, and Bayesian skyline plots suggested that L. spadiceus underwent population expansion during the Late Pleistocene. Both ocean currents and climate change significantly influenced the geographical distribution and genetic population structure of L. spadiceus. [ABSTRACT FROM AUTHOR]

Bottlenose dolphin (Tursiops) populations, also described as the Burrunan dolphins, consist of a resident population of approximately 150 individuals in Port Phillip Bay (PPB), Victoria. Previous reports indicate distribution across a small southern region of PPB; however, little is known about their full distribution patterns across the entire PPB region. Here, we investigate the spatiotemporal distribution of the Burrunan dolphins across four zones representative of PPB benthic habitats and bathymetry to gain a better understanding of the potential drivers of the population's habitat use. Port Phillip Bay, Victoria, Australia. One hundred and twenty‐nine boat‐based surveys were undertaken between March 2015 and August 2021, encompassing 181 sightings. Generalised linear models (GLMs) were used to investigate annual, seasonal and zonal variation. We found no variation in sighting frequencies between years. Austral summer and winter had a significantly higher sighting frequency than autumn. We found that Burrunan dolphins utilise the entire bay, further extending the species range, and show a significantly higher number of sightings in the southern zone than in any other zones. Overlaying dolphin sightings with known oceanographic characteristics within PPB, we found bathymetry and benthic habitats were potential drivers for the Burrunan dolphins distribution and habitat use within the bay, with the dolphins significantly favouring the 5–10 and 10–15 m contour depths. These results show a more widespread distribution across the bay than previously documented. We recommend expansion of the current marine protected areas in the north and south of the bay. This study has increased our understanding of the vital habitat for the Burrunan dolphin populations. By providing evidence‐based conservation recommendations, we hope to improve and contribute to future research, conservation management plans and effective marine protected areas across PPB for the resident Burrunan dolphin population. [ABSTRACT FROM AUTHOR]

The stranding of Sargassum seaweed on the Caribbean archipelago beaches constitutes real socio-economic, ecological and health problems. Météo-France currently operates a model of Sargassum drift forecast (called MOTHY) forced by ocean currents from the global analysis and forecasting system GLO12 at 1/12 ° (∼9 km over the Caribbean) operated by Mercator Ocean International (MOi). In order to improve the Météo-France drift forecast, MOi has developed a regional high-resolution ocean forecasting system CAR36 at 1/36 ° (∼3 km) centred in the Caribbean archipelago region. In addition to a finer spatial resolution, this system was designed to resolve higher-frequency signals such as the tidal forcing and to use hourly atmospheric forcing including the inverse barometer effect. Here the added value of the CAR36 system relative to GLO12 is evaluated with particular focus on the reproduction of meso- and sub-mesoscale structures representing key features of the Caribbean region dynamics and therefore Sargassum transport. The realism of the local dynamics was examined with standard statistical validation diagnostics using satellite data (sea surface height, sea surface temperature, Sargassum detection) and drifting buoys, together with more process-oriented diagnostics such as eddy detection and tracking across the domain. GLO12 and CAR36 hindcast simulations were compared over the year 2019. CAR36 showed marginally better scores using OceanPredict diagnostics (https://oceanpredict.org/ , last access: 10 April 2024). The dynamics of a westward-propagating North Brazil Current (NBC) eddy from its entry into the domain to its dissipation were found to be more realistic in CAR36, especially at the end of its lifetime when it collides with the Caribbean archipelago. The transfer of kinetic energy from the eddy dissipating westward into the Caribbean Sea was diagnosed as more pronounced for CAR36, corresponding to filamentary structures crossing the Caribbean archipelago and resulting in part from the friction of the NBC eddy along the islands to the east. Using detection from satellites, aggregation of Sargassum around eddies or along filaments suggests that CAR36 should improve the algae drift forecasts. [ABSTRACT FROM AUTHOR]

A taxonomic revision of the Tribe Aequipectini from the upper Burdigalian, Lower Miocene Pirabas Formation in Brazil) resulted in an identification of Leptopecten daideleus comb. nov., Perapecten tetristriatus and description of Iemanjavola monlafertei gen. et sp. nov. The genus Perapecten is re-validated, P. tetristriatus being the first fossil representative of the genus, extending it back to the Early Miocene of the western Atlantic Ocean and Middle Miocene-Pliocene Perapecten scabrellus from the Mediterranean Sea/Central Paratethys is included into Perapecten. We also reported the oldest record of Leptopecten, which along with Perapecten, seem to have originated in the Early Miocene tropical region of the western Atlantic Ocean. Leptopecten dispersed during the Middle or Late Miocene to the eastern Pacific through the Central American Seaway, while Perapecten spread across the North Atlantic into Europe via the Circumtropical Current and the Gulf Stream/North Atlantic Drift. [ABSTRACT FROM AUTHOR]

Historical and recent arrivals of crocodilians to the Gulf of Guinean Oceanic Island of São Tomé have intrigued naturalists for several centuries. Here we present the revision of the historical records, and present data regarding the recent arrival of a single specimen in 2021. After being killed by the local authorities, the specimen was preserved and studied both through morphological and molecular methods. Our findings suggest that the specimen was a sub-adult Nile crocodile, Crocodylus niloticus Laurenti, 1768, which most likely drifted from the Congo or Ogooué river mouths in West Africa by the oceanic current acting on the Gulf of Guinea. The story of this individual highlights the dispersion paths that have contributed by the past biological colonization of São Tomé Island. [ABSTRACT FROM AUTHOR]

Species classified in the genus Ulva are important foundational marine primary producers distributed worldwide. These species are particularly abundant and diverse through the northwest Pacific (NWP) where they experience marked latitudinal gradients of environmental heterogeneity. It is unclear, however, to what extent such dynamic conditions can modulate phenotypic and genetic patterns in these organisms, potentially reflecting the influence of historical and contemporary biotic and abiotic factors. Here, we assessed inter- and intra-specific genetic patterns of Ulva species through the NWP using plastid rbcL and tufA gene sequences. Although we initially targeted Ulva australis based on morphological identification, we recovered eight Ulva genetic entities masked by morphological similarities. Except for the Ulva linza–procera–prolifera and U. lactuca–reticulata complexes, six of these genetic entities were recovered as individual species (i.e., U. australis, U. ohnoi, U. californica, U. compressa, U. lacinulata, and U. arasakii), and showed biogeographic patterns likely explained by clines in sea surface temperature and ocean current dispersal. At intra-specific level, all the genetic entities showed low genetic variation and divergence based on rbcL (0–0.3 %) and tuf A (0–0.9 %) data. Our results provide insights regarding intra- and inter-specific genetic patterns characterizing morphologically similar Ulva species through the NWP. However, further studies are needed to understand the mechanisms underpinning such patterns and the associated ecological and evolutionary implications. [ABSTRACT FROM AUTHOR]

In this paper we present a new exact solution that represents a Pollard-like, three-dimensional, nonlinear internal wave propagating on a non-uniform zonal current in a nonhydrostatic ocean model. The solution is presented in Lagrangian coordinates, and in the process we derive a dispersion relation for the internal wave which is subjected to a perturbative analysis which reveals the existence of two distinct modes of wave motion. [ABSTRACT FROM AUTHOR]