Search

High‐resolution digital elevation models (HRDEMs), derived from LiDAR, are widely used for mapping hydrographic details in flat terrains. However, artificial flow barriers, particularly from roads, elevate terrain and prematurely end flowlines. Drainage barrier processing (DBP), such as HRDEM excavation, is employed to address this issue. However, there is a gap in quantitatively assessing the impact of DBP on HRDEM‐derived flowlines, especially at finer scales. This study fills that gap by quantitatively assessing how DBP improves flowline quality at finer scales. We evaluated HRDEM‐derived flowlines that were generated using different flow direction algorithms, developing a framework to measure the effects of flow barrier removal. The results show that the primary factor influencing flowline quality is the presence of flow accumulation artifacts. Quality issues also stem from differences between natural and artificial flow paths, unrealistic flowlines in flat areas, complex canal networks, and ephemeral drainage ways. Notably, the improvement achieved by DBP is demonstrated to be more than 6%, showcasing its efficacy in reducing the impact of flow barriers on hydrologic connectivity. [ABSTRACT FROM AUTHOR]

Developing simple and accurate hydrologic models for wet-weather sanitary sewer flow has long been enigmatic for the engineering community. Hydrologic models suitable for surface water hydrology often perform poorly when simulating sanitary sewer hydrology when they do not account for antecedent moisture conditions and seasonality. The result is underpredicting peak flow and volume in wet conditions and overpredicting the same in dry conditions. The Antecedent Moisture Model is an empirically-calibrated method which models a rainfall capture fraction that varies by antecedent moisture and season, and transforms the captured rainfall into a flow hydrograph. The Antecedent Moisture Model has been particularly successful in modeling sanitary sewer infiltration, for which other methods perform poorly. This paper suggests a reparameterization of the original model which provides virtually identical results while improving interpretability and ease of use. The reparametrized model is designed to be time step independent and more physically relatable, intuitive, and scaleable than the original parameterization while remaining functionally equivalent to the original parameterization. The paper also presents two computational examples which demonstrate the application of the Antecedent Moisture Model formulas and math. [ABSTRACT FROM AUTHOR]

The definition of an ecological niche makes it possible to anticipate the responses of a species to changing environmental conditions. Broad tolerance limits and a paucity of readily observable niches in the pelagic zone make it difficult to anticipate responses of the plankton community related to anthropogenic or environmental changes. Plankton distributions are closely linked to climate change and shape the seascape for higher trophic levels, so monitoring plankton distributions and defining ecological niches will help to understand and predict ecosystem responses. Here we apply a machine learning autoencoder and a density‐based clustering algorithm to high‐frequency datasets sampled with a ROTV Triaxus in the North Sea. The results indicate that in this highly dynamic environment, local hydrography prevents niche‐based separation of plankton species at the sub‐mesoscale, despite the availability of different habitats. Plankton patches were associated with naturally occurring frontal systems and anthropogenically induced upwelling‐downwelling dipoles in the vicinity of offshore wind farms (OWFs). [ABSTRACT FROM AUTHOR]

Cartographic sounding selection is a constraint-based bathymetric generalization process for identifying navigationally relevant soundings for nautical chart display. Electronic Navigational Charts (ENCs) are the premier maritime navigation medium and are produced according to international standards and distributed around the world. Cartographic generalization for ENCs is a major bottleneck in the chart creation and update process, where high volumes of data collected from constantly changing seafloor topographies require tedious examination. Moreover, these data are provided by multiple sources from various collection platforms at different levels of quality, further complicating the generalization process. Therefore, in this work, a comprehensive sounding selection algorithm is presented that focuses on safe navigation, leveraging both the Digital Surface Model (DSM) of multi-source bathymetry and the cartographic portrayal of the ENC. A taxonomy and hierarchy of soundings found on ENCs are defined and methods to identify these soundings are employed. Furthermore, the significant impact of depth contour generalization on sounding selection distribution is explored. Incorporating additional ENC bathymetric features (rocks, wrecks, and obstructions) affecting sounding distribution, calculating metrics from current chart products, and introducing procedures to correct cartographic constraint violations ensures a shoal-bias and mariner-readable output. This results in a selection that is near navigationally ready and complementary to the specific waterways of the area, contributing to the complete automation of the ENC creation and update process for safer maritime navigation. [ABSTRACT FROM AUTHOR]

Copyright of Secuencia: Revista de Historia y Ciencias Sociales is the property of Instituto de Investigaciones - Dr. Jose M. Luis Mora and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cartographic sounding selection is a constraint-based bathymetric generalization process for identifying navigationally relevant soundings for nautical chart display. Electronic Navigational Charts (ENCs) are the premier maritime navigation medium and are produced according to international standards and distributed around the world. Cartographic generalization for ENCs is a major bottleneck in the chart creation and update process, where high volumes of data collected from constantly changing seafloor topographies require tedious examination. Moreover, these data are provided by multiple sources from various collection platforms at different levels of quality, further complicating the generalization process. Therefore, in this work, a comprehensive sounding selection algorithm is presented that focuses on safe navigation, leveraging both the Digital Surface Model (DSM) of multi-source bathymetry and the cartographic portrayal of the ENC. A taxonomy and hierarchy of soundings found on ENCs are defined and methods to identify these soundings are employed. Furthermore, the significant impact of depth contour generalization on sounding selection distribution is explored. Incorporating additional ENC bathymetric features (rocks, wrecks, and obstructions) affecting sounding distribution, calculating metrics from current chart products, and introducing procedures to correct cartographic constraint violations ensures a shoal-bias and mariner-readable output. This results in a selection that is near navigationally ready and complementary to the specific waterways of the area, contributing to the complete automation of the ENC creation and update process for safer maritime navigation.

Ocean stratification on Arctic shelves critically influences nutrient availability, essential for primary production. However, discerning the changes in stratification and their drivers is challenging. Through the use of a highresolution ocean-sea-ice model, this study investigates the variability in stratification within the northeastern Chukchi Sea over the period from 1987 to 2016. Our analysis, validated against available observations, reveals that summers with weak stratification are marked by a warmer water column that features a saltier upper layer and a fresher lower layer, thereby diminishing the vertical density gradient. In contrast, summers with strong stratification are characterized by a cooler column with a fresher upper layer and a saltier lower layer, resulting in an increased density gradient. This variability is primarily driven by the timing of sea-ice retreat and the consequent variations in meltwater flux, with early retreat leading to less meltwater and saltier surface conditions. This factor significantly outweighs the influence of changes in circulation and associated lateral freshwater transport driven by the Bering Strait inflow. We also find that the synchronization of sea-ice retreat and Bering Strait inflow intensity is linked to the timing and strength of the Aleutian Low's westward shift from the Gulf of Alaska to the Aleutian Basin in the early winter. These insights are crucial for understanding nutrient dynamics and primary production in the region. Furthermore, monitoring sea-ice retreat timing could serve as a useful proxy for predicting subsequent summer stratification changes. [ABSTRACT FROM AUTHOR]

This study provides the first estimation of sea ice-melt amount in the Sea of Okhotsk based on spring hydrographic data accumulated for nearly a hundred years. Just after sea ice melts completely, a low-salinity layer appears on the ocean surface, overlying the layer of Winter Water at the freezing point. The integration of the salinity decrease from Winter Water should correspond to the total ice-melt amount. We developed an algorithm to extract the profiles that clearly show the salinity deficit and converted the salinity deficit to the ice-melt amount from all available data. The climatological map shows that ice-melt amount decreases toward the ice edge and exhibits large values around the northern Sakhalin Island, reflecting the ice thickness distribution. In the southern area (south of 48°N), where sea ice is transported from the north, the average ice-melt amount is estimated to be ~ 71 cm in thickness. It is clearly shown that the ice-melt amount has decreased by ~ 30% in the southern area since the 1990s. These changes possibly affect the regional climate through the decreased latent heat of sea ice and potentially affect biological production through weakened stratification caused by decreased ice melt. We also suggested that ice-melt amount did not show a significant trend during the 1930s–1970s, implying that our methodology could extract information on sea ice before the era of satellite observations. [ABSTRACT FROM AUTHOR]

Reduction in soil salinity in the entire project area is a key indicator of proper functioning of the implemented subsurface drainage (SSD) projects. Electromagnetic induction (EMI) surveys were carried out to facilitate spatiotemporal assessment of soil salinity of a SSD project site in Kahni, Haryana (India). The surveys were conducted in two time frames: immediately after the start of SSD project in 2019 and after 2 years of successful operation in 2021. The collected data of 2 surveys was used to derive a depth‐specific calibrated correlation between the observed salinity (ECe) of collected soil samples and surveyed apparent electrical conductivity (ECa) observations in vertical (ECav) and horizontal (ECah) modes. Spatiotemporal analysis of soil salinity revealed notable changes in areas under different salinity classes over a period of 2 years, indicating the impact of SSD on soil desalinization. During the course of 2 years (2019–2021) of SSD operation, area under moderate salinity (4–8 dS m−1) in the top 0–0.15 m soil increased by 54.5% while it decreased by 40% and 6.6% under high (8–12 dS m−1) and very high (12–16 dS m−1) salinity classes. The rice and wheat yields were also enhanced by 24% and 7% respectively after 2 years operation of SSD in hitherto severally waterlogged saline soils. Overall findings of this study reinforce the scope of using EMI approach to quickly and effectively assess the efficacy of subsurface drainage. Creation of measurable soil salinity maps by proposed EMI and GIS techniques can help in planning and implementing site‐specific management strategies in saline soil reclamation projects. [ABSTRACT FROM AUTHOR]

The oceans remain one of Earth's most enigmatic frontiers, with approximately 75% of the world's oceans still unmapped. To create a seamless digital bathymetric model (DBM) from sparse bathymetric datasets, interpolation is employed, but this introduces uncertainties of unknown nature. This study aims to estimate and characterize these uncertainties, which is important in many fields, particularly nautical charting, and navigational safety. Complete seafloor coverage sonar depth data for five testbeds that varied in slope and roughness are sampled at a range of densities (1% to 50%) and interpolated across an entire area using Spline, Inverse Distance Weighting (IDW), and Linear interpolation. The resulting uncertainties are evaluated from both scientific and operational perspectives. Employing linear regression and machine learning techniques, the relationships between these uncertainties and ancillary parameters (distance to the nearest measurement, seabed roughness, and slope) are examined for quantifying and characterizing the interpolation uncertainty. Results indicate insignificant operational differences among the three interpolators in depth estimation, as well as the statistical significance of the examined uncertainty predictors. Additionally, findings suggest the potential presence of unaccounted-for factors shaping uncertainty, yet this work lays a foundational understanding for improving the estimate of uncertainty in DBMs. [ABSTRACT FROM AUTHOR]

In the field of coastal geomorphology, advancements in space technology have revolutionized coastal mapping and understanding. Satellite‐derived bathymetry (SDB) research has progressed, focusing on various estimation methods using high‐resolution satellite imagery and in‐situ data. Challenges arise when applying these methods to the Indian coastline due to its turbid waters and intricate features such as creeks and deltas, laden with sediment and submerged rocks. A study aims to assess multivariate machine learning (ML) regression techniques for estimating bathymetric data. The study employs ground‐truth data and imagery from Aster, Landsat‐8, and Sentinel‐2 at distinct sites known for complex underwater landscapes. Several algorithms including Multiple Linear Regression, Support Vector Regressor, Gaussian Process Regression (GPR), Decision Tree Regression, K‐Neighbors Regressor, k‐fold cross‐validation with Decision Tree Regression, and Random Forest (RF) are evaluated for SDB. Results from the Vengurla Site show that using the Landsat‐8 data set with the GPR algorithm achieves R2 0.94, root mean squared error (RMSE) 1.53 m, and MAE 1.14 m, utilizing visible spectrum bands. At Mormugao, the Sentinel‐2 data set with GPR and RF algorithms attains R2 0.97 and RMSE 1.23 m, with GPR outperforming RF, having an MAE of 1.05 m compared to RF's 1.22 m. This study underscores the potential of ML regression techniques in overcoming challenges with using SDB for mapping coastal geomorphology, particularly in intricate underwater terrains and turbid waters by assimilating sophisticated algorithms and their refined cartographic representation. Plain Language Summary: Researchers are leveraging advancements in space technology to enhance the mapping and comprehension of coastal regions, particularly focusing on satellite‐derived bathymetry (SDB). SDB utilizes high‐resolution satellite imagery in conjunction with on‐site data to estimate the submerged terrain. However, the application of these methodologies along the Indian coastline poses challenges due to factors such as turbidity and the presence of complex geological formations like creeks and deltas. This study explored the utilization of multivariate machine learning (ML) regression techniques to improve the estimation of SDB. Various algorithms were tested using data sourced from satellites such as Aster, Landsat‐8, and Sentinel‐2 across two different sites with diverse underwater landscapes. Results demonstrate promising accuracy, particularly when employing Landsat‐8 data in conjunction with Gaussian Process Regression (GPR), yielding an R2 value of 0.94. Similarly, at another site, the combination of SENTINEL‐2 data with GPR and RF achieved an R2 value of 0.97, underscoring the potential of ML techniques in mapping intricate coastal terrains despite challenges like turbid waters. Key Points: Advancements in space technology for coastal bathymetry mappingPredicting coastal geomorphology with satellite‐derived bathymetry (SDB)Multivariate machine learning regression for estimating SDB [ABSTRACT FROM AUTHOR]

Ice shelves in the Amundsen Sea have experienced the most rapid melting in the Antarctic and are expected to accelerate throughout this century under climate warming. In this study, a high‐resolution ocean‐sea ice‐ice shelf model is employed to conduct sensitivity experiments to explore the effects of increasing melt rates of the Amundsen Sea ice shelves on hydrography, sea ice and ice shelf in the Ross Sea. The results indicate that the substantial inflow of meltwater significantly freshens the Ross Sea, inhibiting the formation and export of the Dense Shelf Water, the volume of which is reduced by 19%–33% on the shelf. Temperatures in the eastern and western Ross Sea exhibit different responses to the enhanced meltwater input. The freshening of the western Ross Sea weakens the mesoscale eddy activities which are efficient in carrying warm Circumpolar Deep Water onto the shelf, leading to an average temperature decrease of 0.02–0.08°C. Conversely, in the eastern Ross Sea, there is a marked warming outside the shelf under increased meltwater, which results from zonal pressure gradients associated with the meltwater distributions. This consequently causes stronger on‐shelf heat transport and shows warming of 0.12–0.22°C on the eastern Ross Sea shelf. The narrow shelf in the eastern Ross Sea allows the warmer water to reach the Ross Ice Shelf (RIS) front, resulting in an about 6%–9% increase in the RIS melting. These results suggest a possible mechanism for acceleration in the RIS melting in the future that is associated with enhanced meltwater inflow. Plain Language Summary: Many studies suggest that the Amundsen Sea ice shelf will experience accelerated melting throughout this century, leading to the release of a substantial amount of freshwater, which will be transported westward and impact the Ross Sea downstream. In this study, a numerical model including ocean, ice shelves and sea ice is used to simulate the effects of increased melting rates of the Amundsen Sea ice shelves on the Ross Sea ocean and ice environments. The results indicate pronounced differences in temperature changes in the eastern and western Ross Sea under enhanced meltwater input. The freshening of the western Ross Sea weakens the warm water intrude onto the shelf, resulting in cooling of the western Ross Sea. In the eastern Ross Sea, there is warming associated with changes in large‐scale flows caused by the distributions of meltwater. More heat transport into the eastern Ross Sea shelf can reach the front of the Ross Ice Shelf (RIS) — the largest Antarctic ice shelf and promotes its melting. Our study proposes a mechanism for acceleration in the RIS melting in the future, highlighting the role of meltwater from the Amundsen Sea ice shelves. Key Points: Enhanced Amundsen Sea ice shelf melting causes marked freshening of the Ross Sea and inhibits the formation of Antarctic Bottom WaterThe increased meltwater inflow from the Amundsen Sea causes cooling of the western Ross Sea and warming of the eastern Ross SeaMore heat transport into the eastern Ross Sea shelf can reach the front of the Ross Ice Shelf and increase its melting rate [ABSTRACT FROM AUTHOR]

Climate change is causing widespread melting of land and sea ice in the Arctic, leading to an increase in freshwater input to the ocean. This may have an impact on ocean circulation, marine ecosystems, and biodiversity in the region. Our findings provide new insights into the summer hydrography conditions at proglacial fjord entrances along large parts of the east coast of Greenland. As most freshwater exits the Arctic Ocean through Fram Strait this study focuses on understanding the origin of spatial distribution of temperature and freshwater in the coastal waters in East Greenland. We find that Polar Water and the Atlantic Water variants (Eurasian Basin Atlantic Water/Subpolar Mode Water) dominate coastal waters north and south of Denmark Strait, respectively, and that coastal waters are influenced by advected meltwater from the Arctic Ocean, glacier meltwater and local precipitation. Combining hydrographic observations, water isotope data, and water source fraction analysis, we show that glacier meltwaters can be detected at fjord entrances and down to approximately 200 m. Integrated over the upper 200 m of the water column, glacial meltwater account for approximately 9%, precipitation for around 8% and Polar Water (including sea ice melt) for approximately 83% of the freshwater observed along the East Greenland coast. Below 200 m, Atlantic Water variants dominate the entire coastal section. The freshwater along East Greenland stays close to the coast and we could not detect any glacier meltwater at the slope. Plain Language Summary: The rapid warming of our planet has increased freshwater input to the Arctic Ocean. A major portion of this freshwater is exiting through Fram Strait. Also, meltwater runoff from tundra lands and glaciers connected to the Greenland ice sheet is an increasingly significant freshwater source to fjords. At present, incomplete observations exist regarding the spatial distribution of freshwater and its origin along East Greenland. Here we present results from a compressed survey of the pan‐East Greenland coastal system from the entrance of fjords. We describe the spatial distribution of water masses and source water fractions along East Greenland and their link to proglacial fjords. Key Points: Polar Water and Atlantic Water variants dominate East Greenland coastal waters north and south of Denmark Strait, respectivelyGlacier meltwater cannot be detected at the slope and most Polar Water, meteoric water, and glacier meltwater are confined to the coastAlong the coast, glacial meltwater account for ∼9%, precipitation for ∼8% and Polar Water (including sea ice melt) for ∼83% of the freshwater [ABSTRACT FROM AUTHOR]

Determining the geometric elements required for the probabilistic calculation of flood bands for watercourses within a hydrographical basin can be achieved by extracting information from remote sensing digital recordings. Given the increasing frequency of extreme hydrological phenomena, the use of data obtained through aerial remote sensing offers the advantage of rapidly determining the geometric characteristics needed to generate profiles for the probabilistic calculation of flood bands for all watercourses within a hydrographical basin. [ABSTRACT FROM AUTHOR]

The Ionian Sea is a crucial intersection for various water masses in the Mediterranean. Its hydrography and dynamics play a significant role in the seawater budgets and biogeochemistry of the neighboring sub-basins. Multiple theories have been formulated to gain a better understanding of the Ionian dynamics. These theories primarily attribute the variability of the near-surface Ionian circulation to internal processes. Here, we utilize horizontal currents and temperature–salinity profiles from the Copernicus reanalysis to examine the contribution of baroclinic modes to the variability of the basin horizontal circulation. Our findings demonstrate that, although the basin vertical structure is characterized by three layers, the primary patterns of the Ionian circulation can be attributed to the first baroclinic mode. This mode, along with the barotropic mode, accounts for over 85% of the overall variability in the Ionian circulation, suggesting that only one of the three interfaces separating the different water masses in the basin is dynamically active. We estimate the depth of this interface to be about 490 m. Additionally, our analysis shows that more than 90% of the kinetic energy over the water column is localized above this interface, indicating that the deep layer of the Ionian is dynamically nearly inert. [ABSTRACT FROM AUTHOR]

Esophageal thermal injury is one of the most devastating complications of atrial radiofrequency ablation, and its diagnosis can be challenging. In this report, we highlight the novel use of free water as a contrast material to better visualize the esophageal lumen in a patient with anaphylaxis to Iodinated contrast media and Gadolinium who recently underwent atrial fibrillation ablation. This becomes particularly handy in patients with contrast allergy, and further emphasizes the role of multimodality imaging. [Display omitted] • MR hydrography is a novel technique that can be used for evaluation of esophageal perforation after RF ablation procedures. • This technique is useful in a subset of patients with contrast allergy in whom multimodality imaging evaluation is necessary. • This report forms the basis of a new imaging technique that could potentially be used in clinical practice in the future. [ABSTRACT FROM AUTHOR]

Euphausiids are a vital component of global marine micronekton. To reveal the primary environmental factors influencing euphausiid distribution patterns in the previously overlooked low-latitude ecosystems, we investigated a large-scale community structure of euphausiids covering the North Pacific subtropical gyre (NPSG) and low-latitude eastern Indian (EI), and South Pacific Oceans (SP). A total of 41 euphausiid species from six genera were identified. Integrated primary production (PP) correlated significantly with the euphausiid abundance and species diversity and displayed the most critical influence on the variations in euphausiid community structure in low latitudes. Dissolved oxygen (DO) was the second significant environmental driver. Due to the distinct distribution patterns of euphausiid species in response to different PP and DO levels, the low-latitude euphausiid assemblages were mainly distinguished into subtropical and tropical communities. The subtropical euphausiid community associated with lower PP and higher DO demonstrated significantly lower euphausiid abundance but higher diversity than the tropical community. Euphausia brevis, E. mutica, and Stylocheiron abbreviatum, which characterize the subtropical community, appear to depend less on the phytoplanktonic prey. Euphausia diomedeae and Hansarsia gracilis, typifying the tropical population, showed stronger hypoxia tolerance. Additionally, each community was further divided into three subgroups under the influence of surface PP (subtropical: marginal NPSG, central NPSG, and austral EI-SP subgroups; tropical: the Bay of Bengal, equatorial EI, and equatorial EI-SP subgroups). These results suggested that food resource is the most important in shaping euphausiids' community structure in an oligotrophic ecosystem with subtle hydrography gradients. [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]

The Banda Sea is of crucial importance for the circulation of the world's oceans, as it is part of the connection between the Pacific to the Indian Ocean. One peculiarity of the upper ocean hydrography in the Banda Sea is the occurrence of barrier layers. The regionality and temporal variability of barrier layer thickness (BLT) in the Banda Sea are examined in this study utilizing in‐situ observations and ocean reanalysis output. It is found that a barrier layer occurs in over 90 % of the observational data profiles, and in over 72 % of those profiles, the BLT is shallower than 10 m. Furthermore, we find a seasonal cycle in BLT with a maximum thickness of about 60 m occurring during austral autumn and winter and coinciding with the presence of low saline waters fed by the regional river discharge and rainfall from the Java Sea and Makassar Strait. In addition, we identify the existence of a quasi‐permanent anticyclonic circulation cell in the Banda Sea that may support the trapping of surface freshwater by retention. The anticyclonic circulation is most likely wind‐driven because it coincides with the regional Ekman pumping pattern. Modulation of the anticyclone is via seasonal variability in the wind stress curl which in turn may explain the efficiency of freshwater retention and thus the BLT. The annual mean BLT distribution in the Banda Sea shows a preferential region of thickened barrier layers around 6o‐8oS and 124o‐126oE and resampling the pattern of the monthly mean climatology. Plain Language Summary: The Banda Sea is crucial to the circulation of the world's oceans and atmosphere due to its location within the equatorial regions of the Indonesian Maritime Continent. It links the Pacific and Indian Oceans' circulation via the Indonesian Throughflow and contributes to driving atmospheric conditions via heat and moisture fluxes. Strong salinity‐stratified barrier layers insulate the water exchange between the surface and subsurface. The formation and seasonal variation of barrier layer thickness (BLT) in the Banda Sea are analyzed based on all available observations and ocean reanalysis outputs. Observations show that the Banda Sea has a barrier layer for the most part of the season. The BLT maximum appears during austral winter (June to August) months. The seasonal BLT maximum is attributed to the near‐surface water freshening, which shoals the mixed layer depth (MLD) and deep isothermal layer depth (ILD) maintained by a steady anticyclonic gyre. Other processes, such as wind stress curl‐induced Ekman pumping associated convergence, also modulate its seasonal variability. Key Points: First study estimating barrier layer thickness (BLT) in the Banda Sea using comprehensive observationsA quasi‐permanent barrier layer exists in the Banda Sea with seasonal variation in occurrence and thicknessThe intrusion of low saline waters and anticyclonic circulation are identified as the main mechanisms for creating and modulating the local BLT [ABSTRACT FROM AUTHOR]

The West Antarctic Ice Sheet is experiencing rapid thinning of its floating ice shelves, largely attributed to oceanic basal melt. Numerical models suggest that the Bellingshausen Sea has a key role in setting water properties in the Amundsen Sea and further downstream. Yet, observations confirming these pathways of volume and tracer exchange between coast and shelf break and their impact on inter‐sea exchange remain sparse. Here we analyze the circulation and distribution of glacial meltwater at the boundary between the Bellingshausen Sea and the Amundsen Sea using a combination of glider observations from January 2020 and hydrographic data from instrumented seals. Meltwater distributions over previously unmapped western regions of the continental shelf and slope reveal two distinct meltwater cores with different optical backscatter properties. At Belgica Trough, a subsurface meltwater peak is linked with hydrographic properties from Venable Ice Shelf. West of Belgica Trough, the vertical structure of meltwater concentration changes, with peak values occurring at greater depths and denser isopycnals. Hydrographic analysis suggests that the western (deep) meltwater core is supplied from the eastern part of Abbot Ice Shelf, and is exported to the shelf break via a previously‐overlooked bathymetric trough (here named Seal Trough). Hydrographic sections constructed from seal data reveal that the Antarctic Coastal Current extends west past Belgica Trough, delivering meltwater to the Amundsen Sea. Each of these circulation elements has distinct dynamical implications for the evolution of ice shelves and water masses both locally and downstream, in the Amundsen Sea and beyond. Plain Language Summary: Floating ice shelves in West Antarctica are thinning, which is largely due to melting of the ice shelf base by the ocean. Here, measurements of ocean temperature, salinity, and dissolved oxygen, collected by a remotely‐controlled underwater vehicle (a glider), are used to estimate the amount of ice shelf meltwater released in the Bellingshausen Sea. Distinct cores of meltwater can be distinguished by the amount of suspended material that is present in the water, which we attribute to meltwater following different circulation pathways after entering the ocean. Historical data from seals equipped with temperature and salinity sensors provide additional information about how the meltwater circulates in the region. The seal data show the presence of a narrow coastal current that brings meltwater from the Bellingshausen Sea into the Amundsen Sea. The pathways of meltwater revealed in this study suggest an important influence of the Bellingshausen Sea on ice shelves throughout West Antarctica. Key Points: Hydrographic observations identify both shelf‐break and coastal meltwater pathways from the western Bellingshausen Sea into the Amundsen SeaDifferences in optical backscatter properties associated with meltwater are related to distinct coast‐to‐shelf break pathwaysThe main pathway to the shelf break is via Seal Trough, identified as the de facto western boundary of the Bellingshausen Sea [ABSTRACT FROM AUTHOR]

The common frog Rana temporaria L. was absent from a poorly buffered, anthropogenically acidified, inland area (Solhomfjell) of Southern Norway where the pH values of ponds and lakes ranged from 4.3 to 4.8 and the Ala concentration was usually below 150 μg/L. Closer to the coast, the calcium concentration was higher and R. temporaria was present, although not common. Successful spawning and larval development were recorded at pH values down to 4.6 and an Ala concentration of 100-300 μg/L. In a reference area (Høylandet) in Central Norway with similar altitude, geology and flora, and a pH in the range of 4.6 to 6.8, R. temporaria was very common at all pH levels. The Ala concentration was usually below 100 μg/L. The comparison between Solhomfjell and Høylandet strongly suggests that acidification explains the absence of R. temporaria at Solhomfjell. This was also demonstrated indirectly by the use of multivariate analyses, although chloride (NaCl) was shown to be the most important explanatory factor for the presence of R. temporaria in the acidified area. Also at Høylandet, where pH was not directly limiting, the lack of salts, and also increased humus content in the water, to some degree restricted the distribution of the frog. In both areas, a pH of approximately 4.6 may be critical for R. temporaria populations in small, poorly buffered, boggy, water bodies like those we have investigated.

High-resolution swath-bathymetric data were collected via multibeam sonar in Lystad Bay (Horseshoe Island, Antarctica). From 3D high-resolution data, important shallows that pose a danger to sailors have been identified. Successive depressions on the crystalline/volcanic bedrock (active lakes), elongated-streamline glacial landforms and glacial landforms with distinctive shapes in this subglacial margin were recognized, and how they may have developed was explained. Limited oceanographic data support that suspended material transport may also be effective in sediment accumulation. Suggestions have been made for geological and geophysical studies that are expected to be carried out in the future. [ABSTRACT FROM AUTHOR]

İzmit Bay, a 50 km long inlet at the eastern end of the Marmara Sea, is crucial for the region's economy, culture, and marine ecosystem. The bay's water circulation regulates nutrient distribution, stratification, sedimentation, oxygen levels, heat, and pollution levels. It is also influenced by meteorological events, such as short-term moderate to strong wind conditions. This study investigated the sensitivity of İzmit Bay Water Circulation to wind speed, direction, and duration using the MITgcm model with Orlanski boundary conditions and process-oriented modeling. The simulations showed that under weak forcing conditions, seawater temperature, salinity, and stratification do not significantly vary. However, strong forcing and wind speeds (statistically defined by percentiles of observation data) of 4.9 m/s (75%), 6.7 m/s (90%), and 10.1 m/s (99%) generate significant mesoscale and sub-mesoscale processes, depending on the direction. Westerly component winds cause downwelling at the eastern coastline, while easterly component winds bring sub-surface water to the surface. Strong winds from N, NE, and E sectors lead to the rise in lower-layer waters in the western basin, forcing them to overflow through the Hersek Delta sill into the central basin. Overall, severe wind events greater than 4.9 m/s (75%) significantly affect the bay's hydrography by transforming the upper layer, with a decrease in temperature up to 5 °C and an increase in salinity up to 10 ppt. [ABSTRACT FROM AUTHOR]

Global and basin-scale ocean reanalyses are becoming easily accessible and are utilized widely to study the Southern Ocean. Yet, such ocean reanalyses are optimized to achieve the best model-data agreement for their entire model domains and their ability to simulate the Southern Ocean requires investigations. Here, we compare several Massachusetts Institute of Technology general circulation model (MITgcm)-based ocean reanalyses (ECCOv4r5, ECCO LLC270, B-SOSE, and GECCO3) for the Southern Ocean. For the open ocean, the simulated time-mean hydrography and ocean circulation are consistent with observations. The MITgcm-based ocean reanalyses show Antarctic Circumpolar Currents (ACC) measuring approximately 149±11 Sv. The simulated 2 °C isotherms are located in positions similar to the ACC and roughly represent the southern extent of the current. Simulated Weddell and Ross Gyre strengths are 51±11 Sv and 25±8 Sv, respectively, consistent with observation-based estimates. However, our evaluation finds that the time evolution of the Southern Ocean is not well simulated in these ocean reanalyses. While observations showed little change in open-ocean properties in the Weddell and Ross Gyres, all simulations showed larger trends, most of which are excessive warming. For the continental shelf region, all reanalyses are unable to reproduce observed hydrographic features, suggesting that simulated physics determining on-shelf hydrography and circulation is wrong. Nevertheless, ocean reanalyses are valuable resources and can be used for generating ocean lateral boundary conditions for regional high-resolution simulations. We recommend that future users of these ocean reanalyses pay extra attention if their studies target open-ocean Southern Ocean temporal changes or on-shelf processes. [ABSTRACT FROM AUTHOR]

Deoxygenation is tied to organic carbon (Corg) supply and utilization in marine systems. Under oxygen-depletion, bacteria maintain Corg respiration using alternative electron acceptors such as nitrate. Since anaerobic respiration's energy yield is lower, Corg remineralization may be reduced and its residence time increased. We investigated the influence of oxygen and alternative electron acceptors' availability on Corg cycling by heterotrophic bacteria during a continuous culture experiment with Shewanella baltica, a facultative anaerobic g-Proteobacteria in the Baltic Sea. We tested six different oxygen levels, from suboxic (<5 µmol L-1) to fully oxic conditions, using a brackish (salinity=14 g L-1) media supplied with high (HighN) or low (LowN) inorganic nitrogen concentrations relative to glucose as labile Corg source. Our results show that suboxia limited DOC (glucose) uptake and cell growth only under LowN, while higher availability of alternative electron acceptors seemingly compensated oxygen limitation under HighN. N-loss was observed under suboxia in both nitrogen treatments. Under HighN, Nloss was highest and a C:N loss ratio of ~2.0 indicated that Corg was remineralized via denitrification. Under LowN, the C:N loss ratio under suboxia was higher (~5.5), suggesting the dominance of other anaerobic respiration pathways, such as dissimilatory nitrate reduction to ammonium (DNRA). Bacterial growth efficiency was independent of oxygen concentration but higher under LowN (34 ± 3.0%) than HighN (26 ± 1.6%). Oxygen concentration also affected dissolved organic matter (DOM) cycling. Under oxic conditions, the release of dissolved combined carbohydrates was enhanced, and the amino acid-based degradation index (DI) pointed to more diagenetically altered DOM. Our results suggest bacterial Corg uptake in lowoxygen systems dominated by S. baltica can be limited by oxygen but compensated by high nitrate availability. Hence, suboxia diminishes Corg remineralisation only when alternative electron acceptors are lacking. Under high nitrate:Corg supply, denitrification leads to a higher N:C loss ratio, potentially counteracting eutrophication in the long run. Low nitrate: Corg supply may favour other anaerobic respiration pathways like DNRA, which sustains labile nitrogen in the system, potentially intensifying the cycle of eutrophication. Going forward, it will be crucial to establish the validity of our findings for S. baltica in natural systems with diverse organic substrates and microbial consortia. [ABSTRACT FROM AUTHOR]

Future mass loss from the East Antarctic Ice Sheet represents a major uncertainty in projections of future sea level rise. Recent studies have highlighted the potential vulnerability of the East Antarctic Ice Sheet to atmospheric and oceanic changes, but long-term observations inside the ice shelf cavities are rare, especially in East Antarctica. Here, we present new insights from observations from three oceanic moorings below Fimbulisen Ice Shelf from 2009 to 2021. We examine the characteristics of Warm Deep Water (WDW) intrusions across a sill connecting the cavity to the open ocean, and investigate seasonal variability of the circulation and water masses inside the cavity. In autumn, solar-heated, buoyant Antarctic Surface Water (ASW) reaches below the 350 m deep central part of the ice shelf, separating colder Ice Shelf Water from the ice base and affecting the cavity circulation on seasonal timescales. At depth, the occurrence of WDW is associated with the advection of cyclonic eddies across the sill into the cavity. These eddies reach up to the ice base. The warm intrusions occur favorably from January to March and from September to November, and traces of WDW-derived meltwater close to the ice base imply an overturning of these warm intrusions inside the cavity. We suggest that both the offshore thermocline depth and interactions of the Antarctic Slope Current with the ice shelf topography over the continental slope cause this timing. Our findings provide a better understanding of the interplay between shallow ASW and deep WDW inflows for basal melting at Fimbulisen, with implications for the potential vulnerability of the ice shelf to climate change. [ABSTRACT FROM AUTHOR]

The harbour porpoise (Phocoena phocoena), a highly mobile cetacean species of the Northern Hemisphere, inhabits basins that vary broadly in salinity, temperature, and food availability; such variation can drive divergent adaptation among local populations. To shed light on range-wide population structure and local adaptation, we generated ddRAD sequencing data spanning the entire North Atlantic and the Baltic Sea, as well as the Black Sea as an outgroup, and mapped this data to the high-quality draft genome of the species. We identified 11,978 genome-wide SNPs from 150 individuals, which we used for population genetic inferences. Our results support genetic differentiation between North Atlantic and Baltic Sea populations, with Kattegat as a transition zone. Across the North Atlantic the population differentiation is subtle from west to east, congruent with an isolation-by-distance pattern, but indicates a separation of southern North Sea harbour porpoises. We identified genomic outlier regions, i.e., scaffold regions where SNPs with high FST across North Atlantic populations co-occur. Together with the draft genome annotation, these regions could point towards candidate genes for differential local adaptation processes among populations. Furthermore, they enable the development of a SNP panel for routine population assignment which will be useful in a conservation and management context. We identified six outlier loci putatively under positive selection, based on the population structure inferred from the complete SNP set. Our study highlights the value of genome resources in conservation and management and provides a crucial additional resource for the study of harbour porpoise evolution and phylogeny. [ABSTRACT FROM AUTHOR]

Eddy‐induced salt transport is essential in maintaining the oceanic salinity balance and global climate. However, the paucity of in situ measurements poses challenges in obtaining the spatial structure of the eddy salt transport globally. Here, we conduct a global estimation of eddy‐induced salinity anomalies and salt transport by eddy movement using 2 million historical hydrographic profile measurements and satellite‐based eddy observations spanning from 1993 to 2019. The results demonstrate rich geographic and vertical variability in the salinity anomalies induced by eddies across the global ocean. Vertical sign switches of salinity anomalies within eddies are observed in the tropical and subtropical oceans, as well as in the Kuroshio Extension region. Additionally, meridional sign switches of eddy‐induced salinity anomalies are observed in the Antarctic Circumpolar Current region. By integrating eddy occurrence probability, we refine the methodology for estimating eddy‐induced salt transport, and provide global spatial patterns of both meridional and zonal salt transport induced by eddy movement at each 2° × 2° grid. Significant salt transport by meridional eddy movement is observed in the mid‐latitude oceans, with the peak zonal‐depth integrated salt transport reaching 106 kg·s− 1 in the mid‐latitudes of the southern hemisphere. Specifically, the Brazil‐Malvinas Confluence region is identified as a highly efficient pathway for meridional salt transport, with a magnitude of − 1.28 × 106 kg·s− 1, significantly surpassing other regions in the global ocean. These findings may provide important references for the understanding and simulation of global oceanic salinity transport. [ABSTRACT FROM AUTHOR]

Simple Summary: The life history traits of Uroteuthis edulis, an economically important loliginid squid in the East China Sea (ECS), have always attracted attention, especially its migration. Understanding the early transport process and influencing factors is a prerequisite for grasping population recruitment and dynamics. To address this, this study used statolith microchemical information and particle tracer experiments to indicate changes in individual habitats and simulate early transport processes, respectively. The results showed that there were differences in early transport trajectories between spring stock and summer stock. Velocity, salinity, and temperature were the key environmental variables affecting early transport for spring stock, while mixed-layer depth (MLD), velocity, and chlorophyll a concentration (Chla) were the key environmental variables for summer stock. These results are related to the dominant characteristics of ocean currents during early transport, which in turn affects the growth and development status of paralarvae. This study provides scientific guidance for understanding population dynamic processes and the sustainable development of resources. Uroteuthis edulis (U. edulis) is an important economic loliginid resource in the East China Sea (ECS). Its flexible life history traits enable the population to quickly adapt to changes in habitat. Understanding the early transport process helps us to grasp the habitat requirements of populations at key life history stages. In this study, particle tracing was used to simulate the early transport trajectories (within 120 days). The gradient forest method (GFM) and generalized additive mixed models (GAMMs) were used to analyze the key environmental variables that affect the early transport trajectories and the impact of environmental factors on the transport process, respectively. The results showed that spring stock tracers were transported to the northeast of the release area (Pengjiayu water) and the Pacific side of Japan. Summer stock tracers were transported to the north and northeast of the release area (Zhoushan island). Current velocity, salinity, and temperature were key environmental variables that affected the trace element ratios of spring stock at early life history stages. Mixed-layer depth (MLD), velocity, and chlorophyll a concentration (Chla) were key environmental variables for summer stock. Zonal velocity was positively correlated with the trace element ratio for spring and summer stock (0.14–0.16 m/s), while the meridional velocity showed an opposite correlation. The physical driving mechanisms of the Kuroshio warm current (or the Taiwan warm current) and the Yangtze River determine the paralarva retention location during early transportation. The differences in the dominant factors of the water environment in the retention area may affect the paralarva physiological functions and food availability. This study provides a scientific basis for a comprehensive understanding of the migration characteristics of U. edulis with different stocks. [ABSTRACT FROM AUTHOR]

An evaluation of the vertical distribution of chlorophyll-a (Chl-a) levels, as an indicator of phytoplankton biomass, has strong repercussions in any marine ecosystem since it allows evaluating its productive potential and the amount of matter that is available for the higher trophic levels of the pelagic food web. This short communication aims to report the vertical distribution patterns of Chl-a levels and some selected hydrographic parameters during autumn in the Bay of La Paz, the biggest and deepest coastal environment inside the Gulf of California, a site also recognized for its high biodiversity. Two oceanographic research cruises were carried out during November 2014 and 2016. A CTD probe configured with dissolved oxygen and active fluorescence sensors, all pre-calibrated by the manufacturer, was used to acquire high-resolution data along the water column. The results showed two distribution patterns of Chl-a: 1) deep peaks (>60 m depth, with concentrations >6 mg m-3) associated with the bottom at nearshore stations, and 2) maximum concentration peaks associated with the thermocline/pycnocline with concentrations up to 7.40 mg m-3 observed at deep stations. A multivariate statistical analysis confirmed the role played by some physical variables in the distribution patterns described. The results shown in this study complement the previous research and fill in the existing gaps for the transition periods between the warm and the cold. [ABSTRACT FROM AUTHOR]

Over the nineteenth century, England and Portugal contested the possession of Delagoa Bay in south eastern Africa. Using documents from a British hydrographical survey mission of the east coast of Africa, and British Parliamentary Papers recording the dispute over possession of the bay in the 1870s, I demonstrate that bordermaking in the region was rooted in interimperial claims and disputes reaching back to the 1820s. The English claim to Delagoa Bay highlights how hydrography and cartography were used as tools of empire in the new imperial expansion and land appropriation of the nineteenth century. The production of the colonial border between Portuguese Mozambique and British South Africa interrupted and disconnected indigenous networks of relation, trade, and movement, while simultaneously entangling imperial projects of white worldmaking through racialized dispossession. [ABSTRACT FROM AUTHOR]

The subtropical North Atlantic is a key region for understanding climate impact in the ocean. Plankton studies in this region have been generally framed in biogeographic provinces or focused on latitudinal gradients. In this study, we demonstrate the benefits of using empirically constructed continuous gradients versus the use of average values for biogeographical provinces to characterize plankton assemblages along a longitudinal transect at 24.5° N using an unprecedented array of stations including hydrographic observations, abundance of phytoplankton and zooplankton, and plankton size spectra in the epipelagic layer (0–200 m). In addition, the variability of zooplankton assemblages was analyzed using detailed taxonomic identification at selected stations. We found significant gradients in most hydrographic and plankton variables. The former, including surface temperature and salinity, the depth of the upper mixing layer, and the depth of the chlorophyll maximum, displayed non-linear gradients with maximum or minimum values near the center of the transect. In contrast, most plankton variables showed linear zonal gradients. Phytoplankton, microzooplankton (<100 µm), and the slope and the intercept of the size spectra increased (and Trichodesmium decreased) to the west. Total mesozooplankton (>200 µm) did not show any significant zonal pattern, but the taxonomic assemblages were characterized by a gradual replacement of large Calanoids by small-bodied Cyclopoid copepods from east to west. The use of continuous gradients provides more detailed information on the zonal structure of subtropical plankton than the classical approach using discrete areas. [ABSTRACT FROM AUTHOR]

Calanoid copepods (CC) are key contributors to the biological carbon pump and pelagic trophic dynamics. The deep-water regions of Perdido and the Bay of Campeche in the western and southern Gulf of Mexico (GM), respectively, differ in hydrography and productivity, leading to potential differences in copepod biomass and community structure. Zooplankton (0-200 m) were collected from the shelf edge to the deep-water region during the winter and summer autumn 2016. Calanoids contributed 38-60% of total zooplankton biomass and 55-70% of overall copepod abundance. The Bay of Campeche had the highest total zooplankton biovolume (287±120 ml 1000 m−3) and total mean copepod abundance (CC and non-calanoids ~146,000 ind. 1000 m−3) during summer-autumn, likely resulting from cross-shelf nutrient transport fueling local productivity. Adult females dominated calanoid numerical abundance (43-50%), thus suggesting a high reproductive potential. Cluster analysis showed differences between seasons (~40% dissimilarity) but not regions. Environmental conditions explained 22% of the variability in community composition; the winter assemblage was significantly related to oxygen concentrations, whereas the summer-autumn community was related to warmer conditions and higher integrated chlorophyll- a concentrations. The CC community responded to seasonal changes more than regionally related hydrographic differences, with likely implications for organic matter cycling and export. [ABSTRACT FROM AUTHOR]

The Loop Current is a key component of global circulation via the northward transport of warm, salty water, and an important influence on Gulf of Mexico hydrography. Understanding how the Loop Current will respond to ongoing anthropogenic warming is critically important, but the history of the Loop Current is poorly known. Here, we present the results of a high resolution (3–8 m) multichannel seismic survey of pelagic carbonate sediment drifts on the eastern Campeche Bank associated with the Loop Current. We identify three seismic megasequences: Megasequence A is a Lower Cretaceous carbonate platform, Megasequence B comprises Cretaceous to lower Cenozoic pelagic carbonates with weak/no contour current flow, and Megasequence C comprises a series of large (100s of m thick) contourite drifts representing the inception and history of the Loop Current. The base of the contourites is marked by a regionally mappable unconformity eroding underling strata, sometimes incising hundreds of meters. The drifts contain a succession of sequence sets separated from each other by regional unconformities and comprising plastered drifts and massive mounded drifts, which characterize modern deposition with active moats on the seafloor. A lack of sediment cores in the study area precludes age determination of these drifts, except for the youngest (Late Pleistocene). Comparison to legacy seismic lines across Deep Sea Drilling Project Site 95, outside our study area, implies that the base of Megasequence C is Oligocene in age, and that the Loop Current developed during the global reorganization of ocean circulation around the Eocene‐Oligocene Transition. Plain Language Summary: The Loop Current flows into the Gulf of Mexico from the Caribbean through the Yucatán Strait and exits to the Atlantic Ocean through the Straits of Florida. It is part of a series of currents that carry warm, salty water to the far North Atlantic, where it cools and sinks, and becomes a critical part of global ocean circulation. The Loop Current is also important for Gulf of Mexico climate, as it sometimes spins off warm eddies which drift west, disrupting fisheries and providing a warm water fuel source for hurricanes. Because of its role in global and regional climate, it is important to understand how the Loop Current will respond to ongoing climate change, and an essential part of that effort is seeing how it has responded to past climate changes. Here, we report the results of a seismic survey of sediment drifts on the eastern Campeche Bank which we believe records the initiation and history of the Loop Current. A lack of sediment cores in this area makes it hard to put age constraints on our observations, so we evaluate several plausible hypotheses about when the Loop Current first formed and what that means for the current's future. Key Points: High resolution multichannel seismic data reveal the evolution of contourite drifts associated with the Loop CurrentContourite deposition began in the Cenozoic, and overlies Cenozoic and Cretaceous pelagic sediments with little evidence of bottom currentsComparison of seismic facies with those present at nearby DSDP Site 95 suggest the Loop Current began in the early Oligocene [ABSTRACT FROM AUTHOR]

The ice shelves in the Bellingshausen Sea are melting and thinning rapidly due to modified Circumpolar Deep Water (mCDW) intrusions carrying heat toward ice‐shelf cavities. Observations are, however, sparse in time and space, and extensive model‐data comparisons have never been possible. Here, using a circulation model of the region and ship‐based observations, we show that the simulated water mass distributions in several troughs traversing mCDW inflows are in good agreement with observations, implying that our model has the skills to simulate hydrographic structures as well as on‐shelf ocean circulations. It takes 7.9 and 11.7 months for mCDW to travel to the George VI Ice Shelf cavities through the Belgica and Marguerite troughs, respectively. Ice‐shelf melting is mainly caused by mCDW intrusions along the Belgica and Marguerite troughs, with the heat transport through the former being ∼2.8 times larger than that through the latter. The mCDW intrusions toward the George VI Ice Shelf show little seasonal variability, while those toward the Venable Ice Shelf show seasonal variability, with higher velocities in summer likely caused by coastal trapped waves. We also conduct particle experiments tracking glacial meltwater. After 2 years of model integration, ∼33% of the released particles are located in the Amundsen Sea, supporting a linkage between Bellingshausen Sea ice‐shelf meltwater and Amundsen Sea upper ocean hydrography. Plain Language Summary: The Bellingshausen Sea Ice Shelves have been affected by high ice‐shelf melt and ice‐loss rates in Antarctica. The reason for the ice loss is the presence of warm modified Circumpolar Deep Water (mCDW) over the continental shelf, which intrudes into ice‐shelf cavities. Recently, studies combining observations and models have significantly advanced our understanding of Ice‐Ocean interactions around Antarctica. For example, in the Amundsen Sea, the region neighboring the Bellingshausen Sea and contributing the most to Antarctic glacial ice loss, such an approach has revealed the drivers and pathways of ocean heat intrusions as well as the impact of glacial meltwater on the Antarctic coastal circulation. We follow this approach and evaluate our ocean model by comparing it with ship‐based and satellite‐based observations. Using this model simulation, we show that the simulated mCDW intrudes from the continental shelf break toward ice‐shelf cavities mainly through two deep cross‐shelf troughs. The glacial meltwater is transported by the westward Antarctic Coastal Current (AACC) flowing into the Amundsen Sea. The mCDW inflow and AACC in the coastal area show seasonal variabilities with higher velocities in the summer, which are likely caused by coastal trapped waves. Key Points: The simulated hydrographic structures over the Bellingshausen Sea continental shelf region are in good agreement with observationsThe warm water intrusions toward the Venable Ice Shelf show peaks of higher velocities in summer, likely caused by coastal trapped wavesGlacial meltwater from about 33% of the area underneath the BS ice shelves flows into the Amundsen Sea within 2 years [ABSTRACT FROM AUTHOR]

Traditional architecture is the result of collective experience in the optimum use of available materials in a given location and adapted to specific conditions and needs. Although forms and groups also depend on other cultural and social issues, the constructive techniques used depend mostly on geographical conditioning factors such as altitude, hydrography, lithology, climate, etc. This text aims to analyse the possible relationships among the multiple variants and specific geographical conditioning factors of each location; in turn, this should provide an understanding of the reasons motivating or reducing their use and the mechanisms adapting these techniques to these conditioning factors. The analysis cross-referenced GIS systems from a database compiling information on 1160 half-timbered walls with a series of themed maps containing information on geographical factors. The conclusions reached show that a single technique adapts to different geographical conditioning factors, giving rise to a wide range of solutions which can provide greater durability and improved habitability. This capacity to adapt to the location is a lesson in sustainability that can be applied at present and is above all part of the intrinsic wealth and value of traditional architecture. [ABSTRACT FROM AUTHOR]

Abstract In the field of coastal geomorphology, advancements in space technology have revolutionized coastal mapping and understanding. Satellite‐derived bathymetry (SDB) research has progressed, focusing on various estimation methods using high‐resolution satellite imagery and in‐situ data. Challenges arise when applying these methods to the Indian coastline due to its turbid waters and intricate features such as creeks and deltas, laden with sediment and submerged rocks. A study aims to assess multivariate machine learning (ML) regression techniques for estimating bathymetric data. The study employs ground‐truth data and imagery from Aster, Landsat‐8, and Sentinel‐2 at distinct sites known for complex underwater landscapes. Several algorithms including Multiple Linear Regression, Support Vector Regressor, Gaussian Process Regression (GPR), Decision Tree Regression, K‐Neighbors Regressor, k‐fold cross‐validation with Decision Tree Regression, and Random Forest (RF) are evaluated for SDB. Results from the Vengurla Site show that using the Landsat‐8 data set with the GPR algorithm achieves R2 0.94, root mean squared error (RMSE) 1.53 m, and MAE 1.14 m, utilizing visible spectrum bands. At Mormugao, the Sentinel‐2 data set with GPR and RF algorithms attains R2 0.97 and RMSE 1.23 m, with GPR outperforming RF, having an MAE of 1.05 m compared to RF's 1.22 m. This study underscores the potential of ML regression techniques in overcoming challenges with using SDB for mapping coastal geomorphology, particularly in intricate underwater terrains and turbid waters by assimilating sophisticated algorithms and their refined cartographic representation.

Submesoscale fronts, with horizontal scale of 0.1–10 km, are key components of climate system by driving intense vertical transports of heat, salt and nutrients in the ocean. However, our knowledge on how large the vertical transport driven by one single submesoscale front can reach remains limited due to the lack of comprehensive field observations. Here, based on high-resolution in situ observations in the Kuroshio-Oyashio Extension region, we detect an exceptionally sharp submesoscale front. The oceanic temperature (salinity) changes sharply from 14 °C (34.55 psu) to 2 °C (32.7 psu) within 2 km across the front from south to north. Analysis reveals intense vertical velocities near the front reaching 170 m day−1, along with upward heat transport up to 1.4 × 10−2 °C m s−1 and salinity transport reaching 4 × 10−4 psu m s−1. The observed heat transport is much larger than the values reported in previous observations and is three times as that derived from current eddy-rich climate models, whereas the salinity transport enhances the nutrients concentration with prominent implications for marine ecosystem and fishery production. These observations highlight the vertical transport of submesoscale fronts and call for a proper representation of submesoscale processes in the next generation of climate models. [ABSTRACT FROM AUTHOR]

Dynamic topography (DT) refers to the time-varying component of the sea surface height influenced by factors like ocean currents, temperature, and salinity gradients. Accurate estimation of DT is crucial for comprehending oceanic circulation patterns and their impact on climate. This study introduces two approaches to estimating DT: (1) utilizing satellite altimetry to directly observe sea surface height and (2) considering the steric and non-steric components of sea level anomalies. The steric term is calculated using salinity and temperature data obtained from local buoy data, Argo observations, and the World Ocean Atlas model. The non-steric term is calculated using GRACE Satellite gravimetry data. To estimate the assimilated DT, four methods are utilized, including variance component estimation (VCE), Bayesian theory, Kalman filter, and 3D variational (3DVAR). These methods assimilate the two aforementioned schemes. The validity of the estimated DT is assessed by comparing the calculated sea surface current, derived from the obtained DT, with observations from local current meter stations. The results indicate that the VCE method outperforms other methods in determining the final DT. Furthermore, incorporating the steric and non-steric terms of sea level in determining DT in coastal areas enhances the accuracy of estimating sea surface currents. [ABSTRACT FROM AUTHOR]

This study aimed to describe the distribution and diversity of soft bottom mollusk community in the Syrian transitional region and to assess the state of alien species in the northern part of the Syrian coast north of Latakia (Ibn Hani site) since 2010, at depths ranging between 110- 160 m. Sixty benthic samples were collected monthly using a Van-Veen grab 1/40 m2 . Water temperature, salinity, pH, and dissolved oxygen of the subsurface water were measured. Molluscan specimens were isolated and identified at the species level. The abundance and biomass for each species in the samples and per square meter were considered to assess spatial and temporal variation of Molluscan assemblages between depths within the months. A total of 167 mollusk species belonging to 3 classes were identified, 57 newly recorded in Syria, and 18 (10.7%) non-indigenous species were found. Among these, three new aliens of Retusa truncatula, Styloptygma beatrix, and Afrocardium richardi were recorded for Syria. The presence of these mollusks was associated with the soft sediments (mud), which did not differ by time or depths. The results revealed that the Molluscan community was dominant by Bittium arenarium, B. tarentinum, Odostomia lorioli, Turritella turbona, Varicorbula gibba, Nucula nucleus, and Lembulus pella. A significant decrease in biomass is expected due to overfishing and severe nutrient deficiency. Our study adds a large number of mollusks to the list of previously recorded species and confirms the increase in the number of aliens and the expansion of their spread in the medium depths. Greater efforts are required to detect more aliens and evaluate their progress, spread, and their relationship with natives, especially in harbors and port environments. [ABSTRACT FROM AUTHOR]

Observations of hydrography and suspended particles supply a large amount of information regarding material transport with respect to the changing marginal sea. To investigate the nepheloid layer structure and variability along the highly energetic continental margin of the northern South China Sea, we combined optical data and time series of acoustic backscatter data. The surface nepheloid layers and subsurface nepheloid layers were widely developed, but the bottom nepheloid layers (BNLs) and intermediate nepheloid layers (INLs) showed regional differences. On the western side of Dongsha Island, there was a large variability of strong INLs, with concentrations up to 0.94 mg L−1, and they occasionally formed and exceeded 200 m in a few hours, with concentration changes up to an order of magnitude. On the eastern side, INLs thicker than 100 m were rare. However, the BNL was larger and more stable, and the strongest BNLs with nepheloid inversion had concentrations up to 0.55 mg L−1 and unexpectedly thickened to be greater than 1,500 m, extending upward to the thermocline. Time series data found that the recurring nonlinear internal waves (NLIWs) dominated the enhancement of BNLs in the Dongsha Slope. The NLIW‐induced vertical velocity reached 0.5 m s−1, increasing the concentration of BNLs and resuspending sediment to 10 m above the bottom. The NLIWs strongly erode the sediments and provide a material source for the upward development of BNLs, while centimeter‐scale rippled scours form on the seafloor. These findings provide evidence of strong lateral transport across continental margins. Plain Language Summary: To understand the structure and variability of nepheloid layers along the continental margin of the northern South China Sea where energetic nonlinear internal waves (NLIWs) are active, we combined conductivity, temperature, depth data from 2017 and time series of lander data from 2022. Our observations revealed that surface nepheloid layers and subsurface nepheloid layers were widely developed, but there were significant regional differences in the structure of bottom nepheloid layers (BNLs) and intermediate nepheloid layers (INLs) between the western and eastern sides of Dongsha Island. On the western side of Dongsha Island, there was a large variability in the thickness of strong INLs. However, INLs rarely had a thickness greater than 100 m on the eastern side, but the BNLs unexpectedly thickened to more than 1,500 m, with nepheloid inversion. Time series data found that the recurring NLIW dominated the enhancement of BNLs in the Dongsha Slope. The NLIWs induced bottom sediment resuspension up to 10 m above the bottom and the formation of rippled scours on the seafloor. These findings provide evidence of strong lateral transport across continental margins and highlight the importance of NLIWs in this process. Key Points: The investigation of nepheloid layer dynamics along the continental margin of the South China Sea reveals their weak to strong variabilityThe recurring nonlinear internal wave trains dominated the enhancement of deep‐sea bottom nepheloid layers (BNLs) in the continental slopeThe thick intermediate nepheloid layers and over‐kilometers BNL are evidence of strong lateral transport from margins [ABSTRACT FROM AUTHOR]

Intertidal sediments are rich in biological resources, which are important for material circulation and energy exchange. Meanwhile, these areas can be treated as sinks as well as sources of coastal heavy metal pollutants. Due to the influence of the tide, the intertidal sediments are in a state of periodic flooding and exposure, and environmental factors such as dissolved oxygen, salinity and overlying water pressure are changeable. Heavy metals in sediments are prone to migration and transformation with the dynamic effects of tidal water and the changes in the environment factors, which increase the bioavailability of heavy metals. In this review, the characteristics of distribution and the bioavailability of heavy metals in intertidal sediments are described; the migration and transformation behavior of heavy metals and its influencing factors under tidal conditions are analyzed; and the mechanisms of heavy metal's migration and transformation in the intertidal zone are summarized. Moreover, the bioaccumulation of heavy metal by organisms and the remediation techniques are discussed. Therefore, this review systematically summarizes the states of existence, the transport mechanisms, and the fate of heavy metals in the intertidal sediment, fills in the research gap of the cycling of heavy metal in the intertidal zone, and provides a theoretical basis for the control of heavy metal pollution. [ABSTRACT FROM AUTHOR]

Satellite altimetry data are useful for monitoring water surface dynamics, evaluating and calibrating hydrodynamic models, and enhancing river-related variables through optimization or assimilation approaches. However, comparing simulated water surface elevations (WSEs) using satellite altimetry data is challenging due to the difficulty of correctly matching the representative locations of satellite altimetry virtual stations (VSs) to the discrete river grids used in hydrodynamic models. In this study, we introduce an automated altimetry mapping procedure (AltiMaP) that allocates VS locations listed in the HydroWeb database to the Multi-Error Removed Improved Terrain Hydrography (MERIT Hydro) river network. Each VS was flagged according to the land cover of the initial pixel allocation, with 10, 20, 30 and 40 representing river channel, land with the nearest single-channel river, land with the nearest multi-channel river and ocean pixels, respectively. Then, each VS was assigned to the nearest MERIT Hydro river reach according to geometric distance. Among the approximately 12 000 allocated VSs, most were categorized as flag 10 (71.7 %). Flags 10 and 20 were mainly located in upstream and midstream reaches, whereas flags 30 and 40 were mainly located downstream. Approximately 0.8 % of VSs showed bias, with considerable elevation differences (≥15 m) between the mean observed WSE and MERIT digital elevation model. These biased VSs were predominantly observed in narrow rivers at high altitudes. Following VS allocation using AltiMaP, the median root mean square error of simulated WSEs compared to satellite altimetry was 7.86 m. The error rate was improved meaningfully (10.6 %) compared to that obtained using a traditional approach, partly due to bias reduction. Thus, allocating VSs to a river network using the proposed AltiMaP framework improved our comparison of WSEs simulated by the global hydrodynamic model to those obtained by satellite altimetry. The AltiMaP source code (10.5281/zenodo.7597310, Revel et al., 2023a) and data (10.4211/hs.632e550deaea46b080bdae986fd19156, Revel et al., 2022) are freely accessible online, and we anticipate that they will be beneficial to the international hydrological community. [ABSTRACT FROM AUTHOR]

The current global water body maps have a resolution of approximately 30 m depending on the available remote sensing data. A water body map with higher spatial resolution is required to distinguish smaller rivers for advanced applications involving global carbon cycle and real-time flood predictions. Conventional water extraction methods use water indices that combine visible and infrared spectra. State-of-the-art remote sensing data including aerial photography, offers a few-meter spatial resolution but only contains the visible spectrum. Here, we established a water extraction method at 60-cm resolution via Bayesian inference, using aerial photography's visible spectrum combining the Landsat-based Global 1-second Water Body Map and the Open Street Map (OSM). The Japan Flow Direction Map (J-FlwDir) was used to link the water bodies. Our method detected the main streams of the Tsurumi and Tama rivers and their tributaries, which were not resolved by the Landsat-based dataset. With our approach, rivers with widths >10 m were detected and water extent was obtained for 37% of small rivers, represented as lines on the OSM. These findings indicate that our method, solely based on visible spectra with hydrography data and existing water body maps, improves the spatial resolution of water mapping without requiring infrared. [ABSTRACT FROM AUTHOR]

The development of low‐oxygen zones threatening marine life (hypoxia) occurs annually in multiple coastal regions of the world. The largest estuary of the continental United States, the Chesapeake Bay, typically has ≈10 km3 of water with dioxygen concentrations <3 mg L−1 in July. As numerical methods for refining model resolutions in targeted areas are becoming common, there is interest in assessing the feasibility of simulating coastal hazards such as hypoxia in Earth System Models (ESMs). These coupled models are typically not constrained by observations and thus likely to feature systematic biases in their land, atmosphere, or ocean components. This study relies on four numerical experiments to evaluate the sensitivity of Chesapeake Bay hypoxia to changes or biases in its external physical forcings. Hypoxia exhibits only a minor decrease (−1.6%) after reducing the Bay's terrestrial freshwater discharge by 9.5% (but keeping terrestrial nutrient loadings the same). Changes in freshwater discharges have their largest impact on hypoxia during one extreme event (−37% during 2011 tropical storm Lee). Similarly, changing oceanic conditions on the shelf or their temporal frequency impact hypoxia by only 5%–6%, indicating that the latter is predominantly dictated by local conditions. Although these results are promising from the perspective of ESMs, additional components of ESMs will need to be evaluated before general conclusions can be reached. We notably speculate that the Bay's hypoxia would exhibit higher sensitivity to other forcings not examined here, notably air temperatures and nutrient loadings. Plain Language Summary: Many coastal embayments of the world experience the development of "dead zones" during the summer, defined by very low concentrations of oxygen in water. The dead zones negatively affect the ecosystem including commercially‐important fisheries. Such a dead zone can be found every summer in the Chesapeake Bay, the largest and most productive estuary in the continental United States. Although these phenomena are typically the focus of local or regional managers, recent improvements in computer capabilities raise the possibility that dead zones could be successfully represented in the same type of computer simulators used for century‐long projections of the Earth's climate. Such simulators would provide a long term projection for the severity of dead zones throughout the world. The present study examines whether a realistic representation of the Chesapeake Bay dead zone can be obtained using information from these global computer simulations. The results show that the representation of the dead zone is not substantially different when using the global data sets selected for this study. This positive outcome opens the door for additional tests that should focus on other components of the global simulators, notably air temperatures and nutrients inputs from the land to the coastal embayments. Key Points: Chesapeake Bay hypoxia shows only a weak sensitivity to continental shelf conditions and variabilityChanges in shelf hydrography propagate throughout the Bay but surface temperatures are set by the meteorological forcingShort term hydrological events are not always captured well by global land models which can impact hypoxia substantially [ABSTRACT FROM AUTHOR]

Copyright of Revista Tamoios is the property of Editora da Universidade do Estado do Rio de Janeiro (EdUERJ) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Streamflow duration is important for aquatic ecosystems and assigning stream protection status. This study predicts streamflow duration, represented as the fraction of time with flow each year, using a combination of sensor data and crowd‐sourced visual observations for a study area in northern Colorado, USA. We used 11 stream stage sensors and 177 visual monitoring points to examine how frequently streams should be sampled to compute flow fractions accurately. This showed that the number of visual observations needed to compute accurate flow fractions increases with decreasing flow duration. We then developed random forest models to predict mean annual flow fractions using climate, topographic, and land cover predictors and found that snow persistence, summer precipitation, and drainage area were important predictors. Model performance was best when using sites with ≥10 visual observations. Our model predicts that almost all (98%) of streams in the study region are non‐perennial, about 10% more than the amount of non‐perennial streams in the National Hydrography Dataset. Stream type maps are sensitive to the time period of data collection and to thresholds used to represent perennial versus non‐perennial flow. To improve maps of non‐perennial streams, we recommend moving beyond categorical classification of streams to a continuous variable like flow fraction. These efforts can be best supported with frequent observations in time that span streams with a wide range of flow fractions and drainage area attributes. Plain Language Summary: Most small streams in the world are not monitored, so we know little about when they are flowing or dry. Yet, the amount of time streams flow can determine whether they are protected by water quality legislation and streamside management plans. In this study we used visual observations of stream flow/no flow and stream sensors to develop a model that predicts the fraction of time that streams flow. At a study area in northern Colorado, volunteer observers documented stream flow/no flow at 177 stream segments, and we placed sensors in 11 headwater streams at different elevations. We found that streams needed to be visited approximately weekly to determine how long they flow each year. Streams that rarely flow needed to be visited more often than those that flow most of the time. Our model shows that most (98%) of the streams in the study area do not flow continuously. The amount of time that streams flow is sensitive to changing climate and water demands. Ongoing monitoring of these streams will help us track and predict the range of flow conditions that are possible throughout the vast networks of small streams that feed larger rivers and lakes. Key Points: Predicted April–September fraction of time with flow using sensors, crowd‐sourced observations, and statistical models in Colorado streamsSnow persistence, summer precipitation, and drainage area are dominant predictors of flow fractions in the Northern Colorado study areaDeveloping a reliable model of flow fraction requires sampling diverse streams that span the full spectrum of flow fractions (0–1) [ABSTRACT FROM AUTHOR]

Copyright of Revista de Historía da Sociedade e da Cultura is the property of Revista de Historia da Sociedade e da Cultura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Arabian Sea is an area of intense ocean‐atmospheric coupling that impacts its physicochemical, and biological processes. During the summer monsoon (June‐September), in the central Arabian Sea, a low‐level atmospheric jet blows parallel to the Arabian Peninsula causing open ocean upwelling in the north and downwelling in the south of the jet axis. High wind speeds are witnessed in the jet axis which advect nutrients from the Somali coast. Consequently, hydrography and physicochemical parameters show high spatial variability. In this dynamic region, phytoplankton size class distribution, directly controlled by nutrient supply, can be modulated by monsoon wind variability via upwelling, advection, and entrainment, however, has not been investigated recently. We studied phytoplankton size class related to atmospheric forcing, hydrography, and nutrient stoichiometry in August 2017 and 2018 along 64°E (11°N–21°N). Chemical taxonomy‐based analysis (CHEMTAX and manual) revealed that in the north, upwelling‐driven nutrient enrichment supported microphytoplankton, mostly diatoms contributing ∼50% to phytoplankton biomass. A stronger upwelling due to higher wind forcing in 2018 compared to 2017 resulted in an enhanced nutrient supply as well as an increased contribution of diatoms. Prymnesiophytic nanophytoplankton distribution was linked to mixed layer depths with insignificant spatial variability (20%–30%). Conversely, in the nutrient‐poor southern region, zeaxanthin and DV‐Chla containing picocyanobacteria and prochlorophytes contributed >50% to the total phytoplankton biomass and were associated with high temperatures. Likely, increasing warming and related changes in monsoon intensity might directly influence phytoplankton size classes impacting trophic transfer and carbon cycling. Plain Language Summary: The Arabian Sea, a part of the North Indian Ocean, is an area of strong ocean‐atmospheric coupling and high biological productivity. This basin provides livelihood to the surrounding countries; however, the increasing rate of sea surface temperature (SST) raises our concern about the subsequent changes in ecosystem services. During the summer monsoon, high biological productivity occurs at certain locations due to upwelling when nutrients are added to the surface by physical forcing. In this study, we have described the results from two cruises (August 2017 and 2018) along the central Arabian Sea that experiences open ocean upwelling in its northern flank and downwelling in the south during the summer monsoon. Atmospheric forcing was found to directly control the hydrography, nutrient availability, and phytoplankton size class distribution across the central Arabian Sea with a distinct interannual difference. The phytoplankton size classes (micro, nano, and picophytoplankton) constructed using the marker pigment data showed prominent spatial and interannual variability that was consistent with the microscopic study. Any future change in the strength and onset of monsoon or increase in SST may directly impact nutrient distribution that can be cascaded to the phytoplankton community, higher trophic level, and carbon export flux. Key Points: Marker pigment‐based phytoplankton community and size classes were analyzed during the summer monsoon (2017–2018) in the central Arabian SeaPhytoplankton community and size classes were mostly governed by hydrography and nutrient stoichiometry induced by monsoon wind forcingAny future change in monsoon strength could impact phytoplankton size classes and can be cascaded to trophic transfer and carbon export [ABSTRACT FROM AUTHOR]