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This work attempts to define metrics for hydrodynamic exposure, using known oceanographic variables to provide a universal site assessment method for mariculture structures. Understanding environmental conditions driving openocean mariculture siting is crucial in establishing consistent ocean governance, minimizing adverse environmental impacts, and facilitating economically sustainable farm operations. To provide a metric of oceanic conditions and associated requirements for structural design and operation of aquaculture systems, six Exposure Indices (EI) are proposed that consider physical energy levels related to hydrodynamic forces at a site. Four of the proposed indices consider only environmental conditions, while the other two also consider the dimensions of the gear that is exposed to the external loads. These indices are: Exposure Velocity (EV), Exposure Velocity at ReferenceDepth (EVRD), SpecificExposureEnergy (SEE), Depth integrated Energy Flux (DEF), Structure-centeredDepth-integrated Energy (SDE), and aStructure-centeredDrag-to-BuoyancyRatio (SDBR). While these indices are derived with a focus on aquaculture structures, they may also have applications for estimating biological stressors and operational challenges. The proposed exposure indiceswere evaluated for a range of known aquaculture sites around the world. A sensitivity analysis was conducted that quantified the relationship between the exposure indices and storm event return period. At a regional scale, hindcast numerical data for the German Bight combined with calculations of 50-year extreme values were used to calculate and map each proposed index spatially. Resulting maps showed that exposure is not simply a function of distance from shore. The six indices show plausible performance regarding the objective assessment of aquaculture sites. The authors herein present the indices to the aquaculture and ocean engineering communities for discussion, application, and potential adoption of one or more of the proposed indices. [ABSTRACT FROM AUTHOR]

Patterns of population connectivity shape ecological and evolutionary phenomena from population persistence to local adaptation and can inform conservation strategy. Connectivity patterns emerge from the interaction of individual behavior with a complex and heterogeneous environment. Despite ample observation that dispersal patterns vary through time, the extent to which variation in the physical environment can explain emergent connectivity variation is not clear. Empirical studies of its contribution promise to illuminate a potential source of variability that shapes the dynamics of natural populations. We leveraged simultaneous direct dispersal observations and oceanographic transport simulations of the clownfish Amphiprion clarkii in the Camotes Sea, Philippines, to assess the contribution of oceanographic variability to emergent variation in connectivity. We found that time‐varying oceanographic simulations on both annual and monsoonal timescales partly explained the observed dispersal patterns, suggesting that temporal variation in oceanographic transport shapes connectivity variation on these timescales. However, interannual variation in observed mean dispersal distance was nearly 10 times the expected variation from biophysical simulations, revealing that additional biotic and abiotic factors contribute to interannual connectivity variation. Simulated dispersal kernels also predicted a smaller scale of dispersal than the observations, supporting the hypothesis that undocumented abiotic factors and behaviors such as swimming and navigation enhance the probability of successful dispersal away from, as opposed to retention near, natal sites. Our findings highlight the potential for coincident observations and biophysical simulations to test dispersal hypotheses and the influence of temporal variability on metapopulation persistence, local adaptation, and other population processes. [ABSTRACT FROM AUTHOR]

During the Atlantic References and Convection (ARC) ship campaign with the reference MSM114/2, which took place in early 2023, the German research vessel Maria S. Merian travelled from Mindelo, Cape Verde, to Punta Arenas, Chile. One of the main objectives of ARC was to obtain vertically resolved cross sections of the Intertropical Convergence Zone (ITCZ). To this end, we crossed the ITCZ three times in the meridional direction. We present the atmospheric and oceanographic measurements collected during ARC in a standardized way to facilitate working with data from different instruments and to make the data easily accessible. This approach is not limited to ARC but could serve as a prototype for future (and past) ship campaigns. We present data from the integrated ship sensors (DShip), a Humidity and Temperature Profiler (HATPRO), a Ceilometer, aerosol instruments (DustTrak, Microtops, and Calitoo), radiosondes, Uncrewed Aircaft Vehicles (UAV), and Conductivity, Temperature, and Depth (CTD) profiles of the upper ocean. We distinguish temporal continuous data (DShip, HATPRO, Ceilometer, DustTrak) from point measurements (radiosondes, UAVs, CTDs, Calitoo, Microtops). To illustrate the data sets provided, we present examples of measurements taken during the three crossings of the ITCZ and during a storm in the Roaring Forties in the South Atlantic at the end of the campaign. All data sets can be downloaded from Köhler et al. (2024a). An overview of all available data sets, including dois, can be found here: https://doi.pangaea.de/10.1594/PANGAEA.966616. For references to the individual data sets, please refer to the data availability section. [ABSTRACT FROM AUTHOR]

Over 60 years of oceanographic observations from Ocean Station Papa (OSP) in the northeast Pacific indicate faster dissolved oxygen loss than the global average. The greatest negative trends in oxygen concentration occur on isopycnals in the upper water column (σθ = 26.1–26.8 kg m−3, ∼110–200 m) but have considerable uncertainty due to natural variability. In this paper, we use eight Argo profiling floats equipped with optode oxygen sensors to assess the 2008–2016 interannual variability of subsurface dissolved oxygen near OSP. We developed a method using high frequency Conductivity‐Temperature‐Depth data to correct optode profiles for slow response times and used reference profiles from the OSP time series to calibrate the optodes. Response time correction markedly improves subsurface bias caused by slow optode equilibration. Our analysis indicates that episodic shoaling of isopycnals can cause rapid reduction in dissolved oxygen concentration. Changes in ventilation, horizontal mixing, and water mass age are unlikely drivers for the rapid O2 loss events examined. We link dissolved oxygen loss during shoaling events to organic matter export, due to higher concentrations of organic matter and greater respiration rates at shallower depths. Reduced net community production during the "Blob" marine heatwave may have reduced the impact of the second shoaling event examined. Natural variations in dissolved oxygen in these layers provide context for uncertainty estimates of long‐term trends and insight toward the potential for future extreme oxygen minima from the combined impact of the long‐term decline and episodic shoaling. Plain Language Summary: Oxygen dissolved in the ocean is declining worldwide as temperatures increase. Widespread ecological stress and altered marine chemistry will be a likely result. The subarctic northeast Pacific Ocean has been losing oxygen even faster than the global average rate. In this study, we use data from ocean observing robots in this region to investigate factors causing episodes of faster oxygen depletion. To do this accurately, we developed and applied a method to correct the data for how slowly the oxygen sensor responds as it moves upward through the water column. We identify two periods of rapid oxygen loss in subsurface water layers of about 1.5 years each. Both episodes happen when regional wind patterns cause these water layers to move closer to the surface. When shallower, these layers experience faster oxygen consumption by respiration, because the supply of organic detritus from the surface is higher. Such oxygen depletion episodes, driven by periodic wind shifts, can be regarded as natural variations in the ocean's oxygen content and need to be considered when interpreting the potential for long‐term anthropogenic trends. Key Points: We observe two episodes of rapid oxygen loss in the upper pycnocline of the NE Pacific coincident with isopycnal shoalingWe propose enhanced respiration at shallower depths as the most likely driver of oxygen declines during these shoaling eventsHigh‐frequency Conductivity‐Temperature‐Depth data can be used to obtain float ascent velocities to correct oxygen optode lag [ABSTRACT FROM AUTHOR]

The Agulhas Return Current (ARC) transports warm tropical and subtropical waters eastward into the southern Indian Ocean. It plays a crucial role in the oceanographic connections between the Indian, Atlantic, and Southern oceans. Modern oceanographic observations show that the latitudinal position of the ARC varies interannually. However, its historical positional variations remain poorly understood. Calcareous nannofossils can be a good indicator of ancient current migration, although their record in the Southwest Indian Ocean is poorly studied. This research aims to understand the characteristics and downcore variation of the calcareous nannofossil assemblages and trace the record of the ancient ARC. To achieve these goals, this study analyzed pelagic sediments of multicore 34IV-SWIR-S021MC03, 34IV-SWIR-S032MC04, and 34IV-SWIR-S040MC05 from the Southwest Indian Ocean. A total of 13 nannofossil species have been identified. The assemblages belong to the subtropical convergence zone regime. They are characterized by warm and cold water species, dominated by Emiliania huxleyi, Calcidiscus leptoporus, Gephyrocapsa muellerae, and Florisphaera profunda. According to the AMS[sup 14]C age model and phytoplankton ecological signatures, this study establishes a calcareous nannofossil indicator to trace the migration of the ancient ARC during the last 40 kyr. The result shows three periods of migration: 40-22 kyr, the ancient ARC was in the far north and was moving southward; 22-14 kyr, a transitional period, the ancient ARC was moving northward; 14-3 kyr, the ARC was moving southward. This further suggests that the migration of the ancient ARC is more complex than the two recognized phases, and there were essential turning points around the last glacial maximum period. It also acknowledges that the ancient ARC is sensitive to interglacial periods and can be influenced simultaneously by the Southern Hemisphere monsoon and westerly winds. [ABSTRACT FROM AUTHOR]

Despite significant recent technological advances, oceanographic observations on horizontal scales of meters to a few kilometres prove challenging. Exploiting legacy seafloor cables presents a disruptive prospect to address this gap, as it may provide low‐cost sustained observations with high space‐time resolution, enabled through novel opto‐electronic interrogation of optical fibers within the cables. Here, we demonstrate this approach in a renewable tidal energy cable embedded within a region with a strong barotropic tide. By making remote measurements continuously over 12 hr, we obtain the distributed differential strain experienced by 2 km of offshore cable from a diverse range of oceanic flow processes, with an along‐cable resolution of 2.04 m. We successfully identify: (a) nearshore wave breaking and its modulation by changes in water depth; (b) along‐cable tidal velocity, shown to be linearly related to the differential strain; and (c) high‐frequency motions consistent with 3‐dimensional turbulent processes, either of natural origin or from flow‐cable interaction. These inferences are supported by nearby conventional measurements of water depth and velocity. Plain Language Summary: While new marine observational tools have greatly improved our understanding of the oceans, a gap in our ability to observe processes occurring on scales of meters to a few kilometers still persists. In this study, we demonstrate the use of a legacy seafloor cable as a disruptive observational platform to enable oceanic velocity measurements on such scales. Using this cable, we measure: (a) surface wave breaking at the beach; (b) the along‐cable water‐velocity from the stretching and compression of the cable; and (c) fast motions associated with small‐scale ocean turbulence. These observations are supported by conventional oceanographic measurements in the same region. Our results highlight the potential of legacy seafloor cabled infrastructure, comprising both energy and telecommunications cables, for sustainably obtaining high‐resolution observations of ocean circulation at low cost. Key Points: A fiber optic embedded within a legacy energy cable is interrogated using distributed sensing techniques for 12 hrThe cable strain data captures the modulation of near‐coast wave breaking by tidal changes in water depthStrain is shown to be linearly related to the local velocity, highlighting the potential for high space‐time resolved velocity sensing [ABSTRACT FROM AUTHOR]

Hypersaline Hamelin Pool, with mean salinity >65, is located in Shark Bay, Western Australia. The high salinity has reduced its biodiversity, but it is home to a diverse assemblage of modern marine stromatolites. The limited exchange of water between Hamelin Pool and the rest of Shark Bay, due to the presence of the shallow Faure Sill together with high evaporation and low rainfall-runoff have resulted in a hypersaline environment. With climate-change-induced mean sea level rise (MSLR), hydrodynamic processes that maintain the hypersaline environment may be affected and are the focus of this paper. Oceanographic observations, together with hydrodynamic model results, were used to examine the hydrodynamic processes under present and future MSLR scenarios. A large attenuation in the tidal range, changes in the tidal characteristics, and current speeds together with a strong salinity gradient were observed across the Faure Sill under present-day conditions. Under an MSLR scenario of 1 m, the tidal amplitude decreased by up to 10% to the north, whilst to the south, the tidal range increased by up to 15%. Regions of strong vertical stratification were present on both sides of the Faure Sill. The simulations indicated that, under MSLR scenarios, these regions expanded in area and exhibited higher levels of vertical stratification. The salt flux across the Faure Sill was maintained as a diffusive process under MSLR scenarios. [ABSTRACT FROM AUTHOR]

The heat transfer between the warm oceanic water and the floating portion of the Antarctic ice sheet (the ice shelves) occurs in a dynamic environment with year‐to‐year changes in the distribution of icebergs and fast‐ice (the “icescape”). Dramatic events such as the collapse of glacier tongues are apparent in satellite images but oceanographic observations are insufficient to capture the synoptic impact of such events on the supply of oceanic heat to ice shelves. This study uses a 3D numerical model and semi‐ idealized experiments to examine whether the current high melting rates of ice shelves in the Amundsen Sea could be mitigated by certain icescape configurations. Specifically, the experiments quantify the impacts on oceanic heat supply of presence/absence of the Thwaites Glacier Tongue, Bear Ridge Iceberg Chain, tabular iceberg B22, and fast‐ice cover seaward of Pine Island Ice Shelf (PIS). The experiments reveal that future changes in the coastal icescape are unlikely to reverse the high ice shelf melting rates of the Amundsen Sea, and that icescape changes between 2011 and 2022 actually enhanced them slightly. Ice shelves such as Crosson and Thwaites are found to have multiple viable sources of oceanic heat whose relative importance may shift following icescape reconfigurations but the overall heat supply remains high. Similarly, the formation of a fast‐ice cover seaward of PIS slows down the cavity circulation (by 7%) but does not reduce its heat supply. [ABSTRACT FROM AUTHOR]

The article provides information about the Japan Meteorological Agency's research vessel, Ryofu Maru, and its role in conducting long-term oceanographic and marine meteorological observations in the western North Pacific. The vessel has undergone several generations of upgrades, with the latest generation, Ryofu Maru IV, featuring advanced observation equipment and environmentally friendly design. The observations conducted by the research vessels contribute to climate change monitoring, global warming prediction accuracy, and decision-making on climate change countermeasures. The article also outlines the hull outline, maneuvering equipment, and observation equipment of Ryofu Maru IV. Despite the limitations imposed by the COVID-19 pandemic, the vessel continues to play a key role in monitoring climate and environmental change in the western North Pacific region. [Extracted from the article]

The underwater environment is filled with various sounds, with its soundscape composed of biological, geographical, and anthropological sounds. Our work focused on developing a novel method to observe and classify these sounds, enriching our understanding of the underwater ecosystem. We constructed a biologging system allowing near-real-time observation of underwater soundscapes. Utilizing deep-learning-based edge processing, this system classifies the sources of sounds, and upon the tagged animal surfacing, it transmits positional data, results of sound source classification, and sensor readings such as depth and temperature. To test the system, we attached the logger to sea turtles (Chelonia mydas) and collected data through a cellular network. The data provided information on the location-specific sounds detected by the sea turtles, suggesting the possibility to infer the distribution of specific species of organisms over time. The data showed that not only biological sounds but also geographical and anthropological sounds can be classified, highlighting the potential for conducting multi-point and long-term observations to monitor the distribution patterns of various sound sources. This system, which can be considered an autonomous mobile platform for oceanographic observations, including soundscapes, has significant potential to enhance our understanding of acoustic diversity. [ABSTRACT FROM AUTHOR]

The mobile ocean weather observation system, named Marine Weather Observer (MWO), developed by the Institute of Atmospheric Physics (IAP), consists of a fully solar-powered, unoccupied vehicle and meteorological and hydrological instruments. One of the MWOs completed a long-term continuous observation, actively approaching the center of Typhoon Sinlaku from 24 July to 2 August 2020, over the South China Sea. The in situ and high-temporal-resolution (1 min) observations obtained from MWO were analyzed and evaluated through comparison with the observations made by two types of buoys during the evolution of Typhoon Sinlaku. First, the air pressure and wind speed measured by MWO are in good agreement with those measured by the buoys before the typhoon, reflecting the equivalent measurement capabilities of the two methods under normal sea conditions. The sea surface temperature (SST) between MWO and the mooring buoys is highly consistent throughout the observation period, indicating the high stability and accuracy of SST measurements from MWO during the typhoon evolution. The air temperature and relative humidity measured by MWO have significant diurnal variations, generally lower than those measured by the buoys, which may be related to the mounting height and sensitivity of sensors. When actively approaching the typhoon center, the air pressure from MWO can reflect some drastic and subtle changes, such as a sudden drop to 980 hPa, which is difficult to obtain by other observation methods. As a mobile meteorological and oceanographic observation station, MWO has shown its unique advantages over traditional observation methods, and the results preliminarily demonstrate the reliable observation capability of MWO in this paper. [ABSTRACT FROM AUTHOR]

The Totten Ice Shelf (TIS) and Moscow University Ice Shelf (MUIS), along the Sabrina Coast of Wilkes Land, are the floating seaward terminuses of the second-largest freshwater reservoir in the East Antarctic Ice Sheet. Being a marine ice sheet, it is vulnerable to the surrounding ocean conditions. Recent comprehensive oceanographic observations, including bathymetric measurements off the Sabrina Coast, have shed light on the widespread intrusion of warm modified Circumpolar Deep Water (mCDW) onto the continental shelf and the intense ice–ocean interaction beneath the TIS. However, the spatiotemporal coverage of the observation is very limited. Here, we use an ocean–sea ice–ice shelf model with updated bathymetry to better understand the regional ocean circulations and ocean–cryosphere interactions. The model successfully captured the widespread intrusions of mCDW, local sea ice production and the ocean heat and volume transports into the TIS cavity, facilitating an examination of the overturning ocean circulation within the ice shelf cavities and the resultant basal melting. We found notable differences in the temporal variability in ice shelf basal melting across the two adjacent ice shelves of the TIS and the western part of the MUIS. Ocean heat transport by mCDW controls the low-frequency interannual-to-decadal variability in ice–ocean interactions, but the sea ice production in the Dalton Polynya strongly modifies the signals, explaining the regional difference between the two ice shelves. The formation of a summertime eastward-flowing undercurrent beneath the westward-flowing Antarctic Slope Current is found to play an important role in the seasonal delivery of ocean heat to the continental shelf. [ABSTRACT FROM AUTHOR]

Typical patterns of the water temperature distribution in the upper mixed layer of the Bering Sea in winter are determined on all available oceanographic data obtainedby research institutions of Russia, Japan, USA, and China. Previously [Luchin, 2023], the data were sorted to two sets presenting «cold» and «warm» winters. The proper set includes 2,492 oceanographic stations and the latter one – 2,130 stations. Spatial distribution of the temperature has some common patterns for both sets: the highest values (3–4 to 5–6 оC) are observed at the central and eastern passages between Aleutian Islands, primarily reflecting the Pacific waters invasion to the sea, then these waters are involved into the large-scale cyclonic gyre over the deep-water basin and transported along the continental slope that is indicated by 3оC isotherm. However, different types of the temperature distribution are well distinguished by prominent difference of its values that is amounted in 1.0–1.5о, up to 3–4о at the northwestern coast including the western part of the eastern Bering Sea slope. A wide set of potential predictors for interannual variability of thermal and dynamic conditions in the Bering Sea are examined using correlation analysis,including the global and regional climatic indices. There is concluded that the winter temperature fields are formed by several key factors, as the warm Pacific waters advection, the basin-scale cyclonic circulation, the vertical and lateral water mixing in the Aleutian sounds and at the continental slope, and fall-winter cooling of the surface layer driven by air–sea heat exchange.

Year-to-year variations of temperature in the upper mixed layer are considered for the ice-free waters of the Bering Sea in cold season (from December to March) using all data of the deep-sea oceanographic observations available to date (12,430 stations for the period from 1943 to 2022). Series of annual mean fields of the mixed layer temperature in December-March were decomposed by applying the empirical orthogonal function (EOF); dynamics of the first two components of decomposition (described in sum 50.4 % of the initial fields variability) are analyzed. The first component (32.4 % of variation) indicates synchronous oscillations over the entire sea area with the maximum contribution at the continental slope. The second component (18.0 % of variance) reflects opposite oscillations in two vast regions of the sea located along the continental slope from Cape Navarin to Alaska Peninsula and in the western, central and southern parts of the deep basin. The following statistically significant periodic oscillations are revealed by spectral analysis: quasi-biennial and those with periods of 4, 7, and 17–20 year for the 1st EOF and quasi-biennial and those with periods of 3 and 4 year for the 2nd EOF. A statistically significant linear trend to warming is detected for the time coefficient of the 1st EOF in the period of 1958–2022. Approximation of this coefficient dynamics with 6-degree polynomial function (polynomial trend) shows a tendencies to the mixed layer cooling in winters of 1969–1972 and 1992–2004 but the opposite tendencies to warming in 1973–1991 and 2005–2022. Variations of time coefficient for the 2nd EOF correspond to opposite tendencies in the areas with positive and negative values of this EOF. For the period from 1958 to 2022, winters in the Bering Sea are classified by the mixed layer temperature, taking into account the contribution of the 1st EOF only, as «warm» (1958, 1959, 1963, 1964, 1966, 1979, 1982, 1985, 1987, 1997, 2001, 2003, 2004, 2015–2018, 2020, and 2022), «normal» (1960–1962, 1965, 1967, 1968, 1970, 1971, 1974, 1978, 1980, 1981, 1983, 1986, 1989–1994, 1996, 1998, 2005–2007, 2011, 2013, 2014, 2019, and 2021), «cold» (1969, 1972, 1973, 1975–1977, 1984, 1988, 1995, 1999, 2000, 2002, 2008, and 2010), and extremely cold (2009 and 2012).

Temperature is an essential oceanographic variable (EOV) that still today remains coarsely resolved below the surface and near the seafloor. Here, we gather evidence to confirm that Distributed Acoustic Sensing (DAS) technology can convert tens of kilometer-long seafloor fiber-optic telecommunication cables into dense arrays of temperature anomaly sensors having millikelvin (mK) sensitivity, thus allowing to monitor oceanic processes such as internal waves and upwelling with unprecedented detail. Notably, we report high-resolution observations of highly coherent near-inertial and super-inertial internal waves in the NW Mediterranean sea, offshore of Toulon, France, having spatial extents of a few kilometers and producing maximum thermal anomalies of more than 5 K at maximum absolute rates of more than 1 K/h. We validate our observations with in-situ oceanographic sensors and an alternative optical fiber sensing technology. Currently, DAS only provides temperature changes estimates, however practical solutions are outlined to obtain continuous absolute temperature measurements with DAS at the seafloor. Our observations grant key advantages to DAS over established temperature sensors, showing its transformative potential for the description of seafloor temperature fluctuations over an extended range of spatial and temporal scales, as well as for the understanding of the evolution of the ocean in a broad sense (e.g. physical and ecological). Diverse ocean-oriented fields could benefit from the potential applications of this fast-developing technology. [ABSTRACT FROM AUTHOR]

In this study, a smoothing method was applied to improve the accuracy of peak wave period estimation using water surface elevation data collected from two oceanographic and meteorological observation towers situated on the western coast of the Korean Peninsula. The effectiveness of the smoothing method was validated by assessing the surface elevation variance and total wave energy. Subsequently, we examined the impact of the smoothing application. The results of our analysis revealed a reduction of approximately 27% in comparison to the confidence interval of the initially estimated spectrum upon applying the smoothing method. Furthermore, a slight variation of approximately 1–2 s was observed between the peak wave period calculated from the estimated spectrum and that obtained through the smoothing process. Utilizing statistical methods to determine the optimal smoothing parameter count, we observed an increasing trend as the range of significant wave heights decreased. [ABSTRACT FROM AUTHOR]

The editorial discusses the need for international standards in marine technology to address the impact of human activities on the marine environment. It emphasizes the importance of consensus-based standards to support the development and application of new technologies in marine observation, exploration, and environmental protection. The article highlights the challenges of balancing marine observation and exploration with environmental sustainability, and the establishment of a Marine Technology Subcommittee by the International Standardization Organization to address these issues. The research presented in the editorial focuses on standardizing marine technology to assess and mitigate the environmental impacts of marine exploration and engineering activities. [Extracted from the article]

The editorial discusses the need for international standards in marine environment impact assessment to address the negative effects of marine observation and exploration on the environment. The International Standardization Organization has established a Marine Technology Subcommittee to negotiate requirements for eco-friendly marine activities. Studies in the research topic focus on standardizing marine technology to assess environmental impacts and provide a framework for future international standards. The research aims to support policymakers and international organizations in establishing practical assessment methods for marine investigation, exploration, and engineering. [Extracted from the article]

The recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6‐day helicopter‐based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5–1°C) occupying a large previously unsampled area of the Sabrina Coast (116.5°E−120°E) below 550–600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (∼−0.7°C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116°E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (∼330 m) profiles. We also highlight the advantages of helicopter‐based observations for accessibility, speed, maneuverability, and cost‐efficiency. The combination of ship‐ and helicopter‐based observations using the JARE61 approach will increase the potential of future polar oceanographic observations. Plain Language Summary: Totten Glacier hosts the most rapidly thinning ice in East Antarctica. This record of thinning is due to rapid melt along the grounding line of the Totten Ice Shelf (TIS), where warm ocean water from the open ocean flows into ice shelf cavities. To understand the pathways and mechanisms of warm water inflow, ocean observations for entire continental shelf regions are necessary. This has historically not been possible due to intense sea ice and icebergs in the region. To overcome this problem, we conducted a 6‐day helicopter‐based oceanographic campaign during the 61st Japanese Antarctic Research Expedition. Our measurements show that warm ocean water occupies a large area of the continental shelf off the TIS. We identify glacial meltwater outflow from the TIS cavity west of 116°E, which provides direct evidence of TIS melting. We also show that helicopter‐based measurements are better for the following aspects; (a) helicopter operations are insensitive to sea ice conditions, (b) helicopter travels faster than a ship, (c) helicopter can conduct measurement in a small ice crack, and (d) helicopter is cheaper to operate than an ice breaker. By combining ship‐based and helicopter‐based approaches, we may be able to enhance the efficiency of future polar oceanographic observations. Key Points: Six‐day helicopter‐based observations retrieved 67 temperature profiles covering the entire continental shelf region off the Totten Ice Shelf (TIS)Between 116.5°E and 120°E, modified Circumpolar Deep Water can be found uniformly over the continental shelf region below 550–600 mGlacial meltwater outflow from the TIS cavity is identified west of 116°E [ABSTRACT FROM AUTHOR]

The efficacy of marine protected areas (MPAs) may be reduced when climate change disrupts the ecosystems and human communities around which they are designed. The effects of ocean warming on MPA functioning have received attention but less is known about how multiple climatic stressors may influence MPAs efficacy. Using a novel dataset incorporating 8.8 million oceanographic observations, we assess exposure to potentially stressful temperatures, dissolved oxygen concentrations, and pH levels across the California MPA network. This dataset covers more than two-thirds of California's 124 MPAs and multiple biogeographic domains. However, spatial-temporal and methodological patchiness constrains the extent to which systematic evaluation of exposure is possible across the network. Across a set of nine well-monitored MPAs, the most frequently observed combination of stressful conditions was hypoxic conditions (<140 umol/kg) co-occurring with low pH (<7.75). Conversely, MPAs exposed most frequently to anomalously warm conditions were less likely to experience hypoxia and low pH, although exposure to hypoxia varied throughout the 2014–2016 marine heatwaves. Finally, we found that the spatial patterns of exposure to hypoxia and low pH across the MPA network remained stable across years. This multiple stressor analysis both confirms and challenges prior hypotheses regarding MPA efficacy under global environmental change. [ABSTRACT FROM AUTHOR]

Barium is widely used as a proxy for dissolved silicon and particulate organic carbon fluxes in seawater. However, these proxy applications are limited by insufficient knowledge of the dissolved distribution of Ba ([Ba]). For example, there is significant spatial variability in the barium–silicon relationship, and ocean chemistry may influence sedimentary Ba preservation. To help address these issues, we developed 4095 models for predicting [Ba] using Gaussian process regression machine learning. These models were trained to predict [Ba] from standard oceanographic observations using GEOTRACES data from the Arctic, Atlantic, Pacific, and Southern oceans. Trained models were then validated by comparing predictions against withheld [Ba] data from the Indian Ocean. We find that a model trained using depth, temperature, and salinity, as well as dissolved dioxygen, phosphate, nitrate, and silicate, can accurately predict [Ba] in the Indian Ocean with a mean absolute percentage deviation of 6.0 %. We use this model to simulate [Ba] on a global basis using these same seven predictors in the World Ocean Atlas. The resulting [Ba] distribution constrains the Ba budget of the ocean to 122(± 7) × 10 12 mol and reveals oceanographically consistent variability in the barium–silicon relationship. We then calculate the saturation state of seawater with respect to barite. This calculation reveals systematic spatial and vertical variations in marine barite saturation and shows that the ocean below 1000 m is at equilibrium with respect to barite. We describe a number of possible applications for our model outputs, ranging from use in mechanistic biogeochemical models to paleoproxy calibration. Our approach demonstrates the utility of machine learning in accurately simulating the distributions of tracers in the sea and provides a framework that could be extended to other trace elements. Our model, the data used in training and validation, and global outputs are available in Horner and Mete (2023, 10.26008/1912/bco-dmo.885506.2). [ABSTRACT FROM AUTHOR]

To clarify the impacts of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a, and stable oxygen isotopic ratios (δ18O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf off the TIS and flowed along bathymetric troughs into the TIS cavity, where it formed a buoyant mixture with glacial meltwater from the ice shelf base. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, photosynthesis and dilution by meltwater from sea ice and the ice shelf base decreased DIC, TA, and nutrient concentrations in surface water near the ice front. These causes also reduced the partial pressure of CO2 (pCO2) in surface water by more than 100 μatm with respect to mCDW in austral summer of 2018 and 2020, and the surface water became a strong CO2 sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, pCO2 decreased mostly as a result of photosynthesis while dilution by glacial and sea ice meltwater had a small effect. The nutrient consumption ratio suggested that photosynthesis was stimulated by iron in the water column, supplied to the surface layer via buoyancy‐driven upwelling and basal ice shelf meltwater in addition to sea ice meltwater. Plain Language Summary: Oceanographic observations were made from the offshore continental slope to the Totten Ice Shelf (TIS) front in Sabrina Coast, East Antarctica, during spring/summer 2018, 2019, and 2020. Results revealed that surface water was strongly influenced by phytoplankton activity and the dilution effect of meltwater from sea ice and the base of the ice shelf. The nutrient consumption ratio between the winter water near the ice shelf front and surface water suggested that enough iron was present in the water column to stimulate photosynthesis. The iron was likely introduced into the surface water by buoyancy‐driven upwelling and meltwater from the base of the TIS in addition to sea ice meltwater. Key Points: The inflow of modified Circumpolar Deep Water supplied biogeochemical components under the Totten Ice ShelfSurface water was influenced by dilution from ice shelf basal meltwater and sea ice meltwater and was changed by biological productivityIron delivered by buoyancy‐driven upwelling, basal ice shelf meltwater, and sea ice meltwater stimulated photosynthesis in surface water [ABSTRACT FROM AUTHOR]

The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf. The Totten Glacier in East Antarctica is grounded below sea level and vulnerable to ocean forcing. Observations and simulations demonstrate warm water access from offshore to the glacier, facilitated by deep topography off the Sabrina Coast. [ABSTRACT FROM AUTHOR]

The mobile ocean weather observation system, named Marine Weather Observer (MWO), developed by the Institute of Atmospheric Physics (IAP), consists of a fully solar-powered, unmanned vehicle and meteorological and hydrological instruments. One of the MWOs completed a long-term continuous observation, actively approaching the Typhoon Sinlaku center from July 24 to August 2, 2020, over the South China Sea. The in-situ and high temporal resolution(1-min) observations obtained from MWO were analyzed and evaluated by comparing with the observations made by two types of buoys during the evolution of Typhoon Sinlaku. First, the air pressure and wind speed measured by MWO are in good agreement with those measured by the buoys before the typhoon, reflecting the equivalent measurement capabilities of the two methods under normal sea conditions. The sea surface temperature (SST) between MWO and the mooring buoys is highly consistent throughout the observation period and even less difference after the typhoon's arrival, indicating the high stability and accuracy of SST measurements from MWO during the typhoon evolution. The air temperature and relative humidity measured by MWO have significant diurnal variations, generally lower than those measured by the buoys, which may be related to the mounting height of the sensor. When actively approaching the typhoon center, the air pressure from MWO can reflect some drastic and subtle changes, such as a sudden drop to 980 hPa, which is difficult to obtain by other observation methods. As a mobile meteorological and oceanographic observation station, MWO has shown its unique advantages over traditional observation methods, and the results preliminary demonstrate the reliable observation capability of MWO in this paper. [ABSTRACT FROM AUTHOR]

Copyright of Revista Fuentes, El Reventón Energético is the property of Universidad Industrial de Santander 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 estimated biomass of mesopelagic fishes has been revised recently, indicating the importance of their roles in oceanic ecosystems and global biogeochemical cycling. This study clarified the occurrence patterns of larval mesopelagic fish species in the surface layers of the highly eutrophic Tokyo Bay. Oceanographic observations and larval fish sampling were conducted across four seasons in 2003 and 2005–06 from the inner area to the mouth of the bay. The number of mesopelagic fishes sampled was 2,276 individuals of 78 species (14 families), accounting for 0.4% of total specimens and 25.4% of the total species number. Myctophidae comprised the largest number of species, with 43 species/morphotypes, followed by Gonostomatidae (seven species). Most larvae in Tokyo Bay were found to belong to tropical/subtropical species. The number of mesopelagic species was negatively correlated with the distance from the Kuroshio Current axis to the mouth of the bay, suggesting that these species were transported by the Kuroshio Current. A thermohaline front likely functions as a barrier preventing mesopelagic fish larvae from entering the inner bay area. Species in the outer bay and mouth of the bay clearly differed, likely due to the differing vertical distributions innate to each species. On the other hand, some species occurred in surface layers penetrated by inner bay water. In addition, the abundances of a myctophid species and copepods, which are potential food items for larvae, were positively correlated, suggesting that some mesopelagic larvae actively approach productive coastal waters due to the advantage of food availability. [ABSTRACT FROM AUTHOR]

Marine industries, war fighters, and world leaders demand accurate maps of ocean properties to underpin tactical and strategic decisions. Oceanographers have approached this challenge by borrowing mapping techniques from weather forecasters. However, compared to the atmosphere, the spatial scales of the ocean are small, and ocean properties are vastly under-sampled. Not surprisingly, despite decades of dedicated effort, the quality of maps of under-sea conditions remains poor. Feature mapping is a new approach to this problem that treats every ocean eddy individually. It strictly limits the influence of each observation to the oceanographic feature that it directly observes. Resulting maps are precise and realistic and may revolutionise ocean forecasting. [ABSTRACT FROM AUTHOR]

The hydroacoustic environment of a rapidly warming Arctic Ocean will be impacted by interconnected changes in the physical environment and increased human activity. Previous acoustic calculations will need to be updated to reflect current and future conditions. Earth System Models are important tools for making projections of changes in a wide range of physical processes under future climates. We present a comparison of Arctic acoustic travel times based on output from the Department of Energy's Energy Exascale Earth System Model with measured travel times from the 2016–2017 Canada Basin Acoustic Propagation Experiment and with travel times predicted by empirical temperature and salinity observations. This comparison allows us to test the impact of changes in Arctic sound speed profiles on acoustic travel times and connects Arctic hydroacoustics with the changing Arctic environment as described by a climate model. Plain Language Summary: As the Arctic Ocean changes due to a warming climate and increased human activity, its acoustic environment will also change. Earth System Models that allow interactions between the ocean, sea ice, atmosphere, and other parts of the global water cycle are important tools for investigating conditions under future climates. Measuring acoustic travel time between two points can help constrain the physical properties that control propagation of sound in the ocean. We use the Department of Energy's Energy Exascale Earth System Model to estimate temperature and salinity at different depths in the Arctic Ocean and use these profiles to calculate the time taken for sound waves to travel between a source and a receiver. We compare these estimates to arrival times directly measured in the 2016–2017 Canada Basin Acoustic Propagation Experiment, and to travel times computed for temperature and salinity data measured by instruments in the Arctic. Through this comparison, we test the impact of changes in the Arctic environment on acoustic travel times and demonstrate how a climate model can describe acoustic properties in a changing Arctic Ocean. Key Points: We compare Arctic Ocean acoustic travel times based on an Earth System Model, oceanographic observations, and an acoustic experimentSound speeds in the upper 400 m of the western Arctic Ocean are rapidly changing due to warming and freshening of water layersThe Energy Exascale Earth System Model captures the layered structure of the Canada Basin but not its relative sound speed variations [ABSTRACT FROM AUTHOR]

Dr. Susumu (Sus) Tabata, a preeminent Canadian physical oceanographer, passed away on February 5, 2024, at the age of 99. He was known for his role in initiating and maintaining the long Station P/Line P oceanographic observations, which have provided scientists with a high-quality, long time series for climate change and numerical model evaluation. Dr. Tabata's research on changes in the ocean with time, as well as his analysis of ocean currents and eddies, has had a significant impact on multi-disciplinary research and fisheries management. He was also involved in the development of new technology for ocean measurements. Dr. Tabata's contributions to ocean research were recognized with the John P. Tully Medal in Oceanography in 2008. He is survived by his two daughters, son, and three grandchildren. [Extracted from the article]

The Antarctic Intermediate Water (AAIW), one of the most important global intermediate water masses, spreads over the world ocean. Its propagation limit at the Northeast Subtropical Atlantic is characterized by its encounter with the Mediterranean Water (MW), which presents dissimilar thermohaline properties. Previous studies of the AAIW in this region have been based on traditional oceanographic cruise observations, which were later complemented by observations using autonomous systems such as ARGO floats. However, these observations present limitations for the study of processes occurring at mesoscale and smaller scales. In this study, we used high-resolution observations made by cutting edge platforms such as underwater gliders. Specifically, a meridional glider section realized in spring 2016 between the islands of Madeira and Gran Canaria has been used. The temperature, salinity and dissolved oxygen minima have allowed the detection of the AAIW signal north of the Canarian archipelago and significantly westward from its main northward propagation pathway in this region. The results of this work have shown that the encounter of AAIW and MW generates thermohaline intrusions or interleaving layers. It is suggested that double diffusion processes may play a role in the development of these structures, which may be important for water masses mixing and, therefore, in determining the northward spreading boundary of AAIW. The use of the high-resolution glider observations combined with other data products is essential for the study of water masses and dynamics when relevant processes have a wide range of scales. [ABSTRACT FROM AUTHOR]

Variation of the Kuroshio path south of Japan has an important impact on weather, climate, and ecosystems due to its distinct features. Motivated by the ever-popular deep learning methods using neural network architectures in areas where more accurate reference data for oceanographic observations and reanalysis are available, we build four deep learning models based on the long short-term memory (LSTM) neural network, combined with the empirical orthogonal function (EOF) and complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), namely, the LSTM, EOF–LSTM, CEEMDAN–LSTM, and EOF–CEEMDAN–LSTM. Using these models, we conduct long-range predictions (120 days) of the Kuroshio path south of Japan based on 50-yr ocean reanalysis and nearly 15 years of satellite altimeter data. We show that the EOF–CEEMDAN–LSTM performs the best among the four models, by attaining approximately 0.739 anomaly correlation coefficient and 0.399° root-mean-square error for the 120-day prediction of the Kuroshio path south of Japan. The hindcasts of the EOF–CEEMDAN–LSTM are successful in reproducing the observed formation and decay of the Kuroshio large meander during 2004/05, and the formation of the latest large meander in 2017. Finally, we present predictions of the Kuroshio path south of Japan at 120-day lead time, which suggest that the Kuroshio will remain in the state of the large meander until November 2022. [ABSTRACT FROM AUTHOR]

We demonstrate that bistatic reception of high-frequency oceanographic radars can be used as single-frequency oblique ionospheric sounders. We develop methods that are agnostic of the software-defined radio system to estimate the group range from the bistatic observations. The group range observations are used to estimate the virtual height and equivalent vertical frequency at the midpoint of the oblique propagation path. Uncertainty estimates of the virtual height and equivalent vertical frequency are presented. We apply this analysis to observations collected from two experiments run at two locations in different years, but utilizing similar software-defined radio data collection systems. In the first experiment, 10 d of data were collected in March 2016 at a site located in Maryland, USA, while the second experiment collected 20 d of data in October 2020 at a site located in South Carolina, USA. In both experiments, three Coastal Oceanographic Dynamics and Applications Radars (CODARs) located along the Virginia and North Carolina coast of the US were bistatically observed at 4.53718 MHz. The virtual height and equivalent virtual frequency were estimated in both experiments and compared with contemporaneous observations from a vertical incident digisonde–ionosonde at Wallops Island, VA, USA. We find good agreement between the oblique CODAR-derived and WP937 digisonde virtual heights. Variations in the virtual height from the CODAR observations and the digisonde are found to be nearly in phase with each other. We conclude from this investigation that observations of oceanographic radar can be used as single-frequency oblique incidence sounders. We discuss applications with respect to investigations of traveling ionospheric disturbances, studies of day-to-day ionospheric variability, and using these observations in data assimilation. [ABSTRACT FROM AUTHOR]

The Rockall Trough (RT) accommodates the warmest and saltiest branch of the North Atlantic Current, which delivers water from the Gulf Stream into the marine environment around western Europe. In addition, the European Slope Current (ESC) carries warm water northward along the eastern boundary of the RT, and exchange between the ESC and the continental shelf is a dominant factor in determining the oceanographic conditions around the British Isles. However, the picture of the mean circulation and variability in the RT is still emerging, with a continuous observational campaign still in its relative infancy. The ESC, in particular, is poorly constrained by ship‐based, mooring, and satellite observations. In this paper, we examine the RT circulation and volume transport using a temporally extended and spatially expanded observing network. Six years of continuous mooring occupation reveal that a large‐amplitude, basin‐scale freshening event, previously detected south of Iceland around 2015, impacted the RT around 2017. Geostrophic transport was greatly reduced during this period, driven by a concurrent subsurface temperature increase at the western boundary. The circulation regained strength during the latter part of the record. We gathered 110 glider transects over 22 months which capture the ESC velocity field in unprecedented detail. The data are sufficient to characterize both the mean state and the emergent seasonal variability of the ESC, and reveal the year‐round presence of a southward countercurrent at depth. Variability in the strength and structure of this previously unstudied feature modulates net northward transport in the eastern boundary current system. Plain Language Summary: The Rockall Trough (RT) is a key pathway for warm and salty water flowing northward, a process which plays a key role in dictating the western European climate. However, the amount of water flowing northward, and how it changes over time, is still rather uncertain. In particular, the narrow boundary current in the eastern RT has previously proven difficult to measure. In this paper, we use 6 years of continuous oceanographic observations in the RT to monitor the flow. We also used underwater robots, called gliders, to focus on the narrow current in the eastern boundary. The data gathered give the best description of the ocean currents in the region to date. The study period coincided with a period of profound change across the subpolar North Atlantic, with a strong freshwater signal detected in the RT around 2017. The glider observations give a detailed view of the narrow eastern boundary current and how it varies seasonally, and also revealed the presence of a southward‐flowing current at depth. Key Points: Eastern boundary current system captured in unprecedented detail using 22 months of near‐continuous glider observationsLarge‐scale freshening event in subpolar North Atlantic impacted Rockall Trough (RT) around 2017Interannual variability in poleward transport driven by subsurface temperature anomalies at the western flank of the RT [ABSTRACT FROM AUTHOR]

Sea surface temperature (SST) is of paramount importance for comprehending ocean dynamics and hence the Earth's climate system. Accordingly, it is also the most measured oceanographic parameter. However, until the end of the XIX century, no continuous time series of SST seems to exist, with most of the available data deriving from measurements on ships. Here, we present a continuous digitalized record of surface water measurements originally written in a book published in 1853. The measurements were retrieved thrice daily in the Venice lagoon, in the northeastern part of the Italian peninsula, from June to August 1851 and 1852. To the best of our knowledge, these data constitute the oldest time series of the entire world ocean. The measurements were performed by immersing a Réaumur thermometer a few meters deep in the lagoon water at 8 a.m., 12 p.m., and 8 p.m. Despite several limitations affecting these data (e.g., lacking information regarding the exact water depth where measurements were performed and instrumental metadata), they are of utmost significance, as they put many decades backward the date of the development of a fundamental aspect of oceanographic observations. Moreover, the data were collected close to the Punta della Salute site, where actual sea water temperature measurements have been performed since 2002. Therefore, a unique comparison between surface water temperatures within the Lagoon of Venice across three centuries is possible. [ABSTRACT FROM AUTHOR]

Denman Glacier, which drains a marine‐based sector of the East Antarctic Ice Sheet with an ice volume equivalent to 1.5 m of global sea level rise, has accelerated and undergone grounding line retreat in recent decades. A deep trough and retrograde bed slope inward of the grounding line leave this glacier prone to marine ice sheet instability. The ocean heat flux to the ice shelf cavity is a critical factor determining the susceptibility of the glacier to unstable retreat. Profiling float observations show modified Circumpolar Deep Water as warm as −0.16°C reaches a deep trough extending beneath the Denman Ice Tongue. The ocean heat transport (0.77 ± 0.35 TW) is sufficient to drive high rates of basal melt (70.8 ± 31.5 Gt y−1), consistent with rates inferred from glaciological observations. These results suggest the Denman Glacier is potentially at risk of unstable retreat triggered by transport of warm water to the ice shelf cavity. Plain Language Summary: The Denman Glacier is a vast river of ice that drains the East Antarctic Ice Sheet. The Denman holds a volume of ice equivalent to 1.5 m of global sea level rise, so changes in the glacier could have a large impact on future sea level rise. The vulnerability of the Denman Glacier to melting by warm ocean waters has been difficult to assess because very few oceanographic observations have been collected in the region. We use new profiling float measurements to show warm water reaches a deep trough that extends inland beneath the glacier, exposing the base of the ice to ocean‐driven melting. We estimate that the amount of warm water entering the cavity is sufficient to melt 70.8 billion tons of ice each year. These observations suggest that the Denman Glacier is potentially at risk from unstable retreat driven by warm water flowing into the cavity and melting the ice from below. Key Points: Float profiles show warm (up to −0.16°C) modified Circumpolar Deep Water at depth in a trough extending below the Denman Ice TongueA bottom‐intensified current on the eastern side of the deep trough transports 138 ± 65 mSv of water warmer than −1°C into the cavityOcean heat transport into the cavity is sufficient to drive high basal melt (70.8 ± 31.5 Gt y−1), consistent with glaciological observations [ABSTRACT FROM AUTHOR]

Using observational data, satellite altimeters, and reanalysis model products, we have investigated eddy-induced seawater anomalies and heat and salt transport in the northeastern tropical Pacific Ocean. An eddy detection algorithm (EDA) was used to identify eddy formation at the Mexican Tehuantepec Gulf (TT) in July 2018 during an unusually strong summer wind event. The eddy separated from the coast with a mean translation velocity of 11 cms-1 and a mean radius of 115 km and traveled 2050–2400 km westwards off the Central American coast, where it was followed at approx 114 ∘ W and 11 ∘ N for oceanographic observation between April and May 2019. The in situ observations show that the major eddy impacts are restricted to the upper 300 m of the water column and are traceable down to 1500 m water depth. In the eddy core at 92 m water depth an extreme positive temperature anomaly of 8.2 ∘ C, a negative salinity anomaly of -0.78 psu, a positive fluorescence anomaly of +0.8 mgm-3 , and a positive dissolved oxygen concentration anomaly of 137 µmolkg-1 are observed. Compared with annual climatological averages in 2018, the water trapped within the eddy is estimated to transport an average positive westward zonal heat anomaly of 85×1012 W and an average westward negative salt anomaly of -2.1×106 kg s -1. The heat transport is the equivalent of 1 % of the total annual zonal eddy-induced heat transport at this latitude in the Pacific Ocean. Understanding the dynamics of long-lived mesoscale eddies that may reach the seafloor in this region of the Pacific Ocean is especially important in light of potential deep-sea mining activities that are being targeted on this area. [ABSTRACT FROM AUTHOR]

Multifarious and continuous oceanographic observation data is of considerable significance to oceanographic research and military application. In this paper, a novel oceanographic observation method with dual-modal underwater vehicle able to switch between the Argo and Glider modes is proposed and is studied experimentally in the South China Sea. Using the Newton–Euler formulation, a complete dynamic model considering the variation in gravity/buoyancy due to mode switching is thus established. Then, based on Lyapunov stability criterion, a nonlinear adaptive inverse controller with multiple inputs and multiple outputs is developed which enables the observation platform to freely switch between various modes. By analyzing the numerical and experimental data of a single mode, the results demonstrate that the proposed method can supplement the observation data and improve the accuracy of oceanographic data. Finally, based on experimental data acquired by the dual-modal underwater vehicle in the South China Sea, three-dimensional regional oceanic temperature and salinity fields are constructed with the spatio-temporal Kriging method, and feature surfaces are extracted from the oceanic fields. Furthermore, the proposed method can be applied in other stirring dynamic regions, such as ocean eddies, ocean fronts, filaments, etc. [ABSTRACT FROM AUTHOR]

Copyright of Hydrographic Surveying & Charting / Haiyang Cehui is the property of Hydrographic Surveying & Charting Editorial Board 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.)

One of the proposed mechanisms for energy loss in the ocean is through dissipation of internal waves, in particular above rough topography where internal lee waves are generated. Rates of dissipation and diapycnal mixing are often estimated using linear internal wave generation theory and a constant value for mixing efficiency. However, previous oceanographic measurements found that nonlinear dynamics may be important close to topography. To investigate the role of nonlinear interactions, we conduct idealized 3D direct numerical simulations (DNS) of steady flow over 1D topography and vary the topographic height, which correlates to the degree of flow nonlinearity. We analyze the spatial distribution of energy transfer rates between internal waves and the nongeostrophic portion of the time-mean flow, and of dissipation and diapycnal mixing rates. In our simulations with taller, more nonlinear topographies, energy transfer rates are similar to previously unexplained oceanographic observations near topography: internal waves gain energy from time-mean flow through horizontal straining and lose energy through vertical shearing. In the tall topography simulations, buoyancy fluxes also play a significant role, consistent with observations but contrary to linear wave theory, suggesting that quasigeostrophy-based approximations and linear theory may not hold in some regions above rough topography. Both dissipation and mixing rates increase with topographic height, but their vertical distributions differ between topographic regimes. As such, the vertical profile of mixing efficiency is different for linear and nonlinear topographic regimes, which may need to be incorporated into parameterizations of small-scale processes in models and estimates of ocean energy loss. [ABSTRACT FROM AUTHOR]

The deep ocean to the east and south of Taiwan Island‒including the Okinawa Trough, Ryukyu Arc, Philippine Sea, Luzon Strait, and the northeast South China Sea‒is one of the most prominent mixing hotspots of the global ocean. The high‐resolution seismic reflection technique can provide detailed views of the water's finestructure and near‐transient turbulent mixing therein. Using legacy data from two seismic cruises, we present the finestructure and quantify turbulent mixing within the thermocline and sub‐thermocline (100–1,000 m depths) to the east and south offshore Taiwan. We derive dissipation rate ε and diapycnal diffusivity Kρ by analyzing the inertial convective turbulence regime of horizontal slope spectra from the seismically auto‐tracked wave‐fields. Dissipation and diffusivities are locally enhanced close to the topography exceeding 10−6 W⋅kg−1 and 10−2 m2⋅s−1, and gradually decrease to 10−9 W⋅kg−1 and 10−4‒10−5 m2⋅s−1 beyond tens of kilometers. The mean diffusivity distribution pattern suggests that a large fraction of the energy dissipates close to the topography and a significant fraction is radiated into the open ocean. Both the tides and west boundary current drive the significantly enhanced mixing close to the topography of ridges, isolated islands and continental slopes. Kuroshio and eddy activities are responsible for the local anomalously enhanced mixing patches far away from the topography. Comparisons among seismic results, numerical simulations and eddy analyses suggest that the energy cascades downward from large‐scale motions to small‐scale turbulence via multiple mechanisms of tide‐topography interaction, flow‐topography interaction, and frontal instability around the island of Taiwan. Plain Language Summary: Rough topography behaves like stirring rods that help to mix the stratified water in the open ocean. The deep ocean area around the island of Taiwan is a well‐known mixing hotspot due to its extremely strong energy dissipation effect close to complex topography via interactions with tides. The seismic reflection method has been widely used to study various oceanic phenomena in the global ocean at a high spatial resolution of ∼10 m. Here we use this method to characterize the mixing across density surfaces for the vast deep‐sea area around the island of Taiwan. We find that strong tidal activity is the main cause of the strong mixing around topography. In addition, flow‐topography interaction of Kuroshio or eddy currents is another important contribution to enhanced mixing in the study region, especially atop the Ryukyu Arc. The mixing mechanisms around Taiwan are more complex than those at the Mariana Ridge. Integrating this novel seismic observation with conventional oceanographic methods is therefore a potential way to reveal a close‐to‐complete energy cascading scenario of "source‐path‐sink" in the ocean. Key Points: Enhanced mixing in the deep ocean around Taiwan Island is observed using seismic oceanographyEmpirical diffusivity structures varying with topography are constructed for the mixing hotspotTide‐ and flow‐topography interactions are the dominant mixing mechanisms [ABSTRACT FROM AUTHOR]

Wave Glider is an unmanned autonomous vehicle fully powered by renewable energy, which converts wave energy into thrust and converts solar energy into power for electronic devices. It is extensively applied in large-scale, long-term ocean observation. However, photovoltaic power generation capacity of Wave Glider is relatively weak (continuous power available to payloads: 10 Watts), which limits the sensing and communication ability of Wave Glider. This paper presents a Wave Glider with a WEC called WEC-Glider scheme, i.e., the fluctuating tension of umbilical drives the slider to do a reciprocating movement, and then the slider drives the ball screw to spin the generator. The WEC-Glider is capable of converting wave energy into electricity as well as propulsion. Based on Fossen's equation, the 6-DOF dynamic models are established. A numerical model is established via Matlab/Simulink, to simulate the dynamic response with different parameters. The numerical results show that the proposed WEC-Glider can achieve 34 Watts power generation under the given regular waves. In the future, the WEC-glider could be used in the oceanographic observation to cope with insufficient photovoltaic power generation of the traditional Wave Glider, especially on continuous cloudy days or in high latitude region. [ABSTRACT FROM AUTHOR]

We investigated liquid freshwater content (FWC) in the upper 100 m layer of the Arctic Ocean using oceanographic observations covering the period from 1990 through 2018. Our analysis revealed two opposite tendencies in freshwater balance—the freshening in the Canada Basin at the mean rate of 2.04 ± 0.64 m/decade and the salinization of the eastern Eurasian Basin (EB) at the rate of 0.96 ± 0.86 m/decade. In line with this, we found that the Arctic Ocean gained an additional 19,000 ± 1000 km3 of freshwater over the 1990–2018 period. FWC changes in the EB since 1990 demonstrate an intermittent pattern with the most rapid decrease (from ~5.5 to 3.8 m) having occurred between 2000 and 2005. The 1990–2018 FWC changes in the upper ocean were concurrent with prominent changes of the thermohaline properties of the intermediate Atlantic Water (AW)—the main source of salt and heat for the Arctic Basin. In the eastern EB, we found a 50 m rise of the upper AW boundary accompanied by a ~0.5 °C increase in the AW core temperature. The close relationship (R > 0.7 ± 0.2) between available potential energy in the layer above the AW and FWC in the eastern EB suggests a positive feedback mechanism that links the amount of freshwater with the intensity of vertical heat and salt exchange in the halocline and upper AW layers. Together with other mechanisms of Atlantification, this feedback creates a complex picture of interactions behind the observed changes in the hydrological and ice regimes of the Eurasian sector of the Arctic Ocean. [ABSTRACT FROM AUTHOR]

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The inception of a moored buoy network in the northern Indian Ocean in 1997 paved the way for systematic collection of long-term time series observations of meteorological and oceanographic parameters. This buoy network was revamped in 2011 with Ocean Moored buoy Network for north Indian Ocean (OMNI) buoys fitted with additional sensors to better quantify the air–sea fluxes. An intercomparison of OMNI buoy measurements with the nearby Woods Hole Oceanographic Institution (WHOI) mooring during the year 2015 revealed an overestimation of downwelling longwave radiation (LWR↓). Analysis of the OMNI and WHOI radiation sensors at a test station at National Institute of Ocean Technology (NIOT) during 2019 revealed that the accurate and stable amplification of the thermopile voltage records along with the customized datalogger in the WHOI system results in better estimations of LWR↓. The offset in NIOT measured LWR↓ is estimated first by segregating the LWR↓ during clear-sky conditions identified using the downwelling shortwave radiation measurements from the same test station, and second, finding the offset by taking the difference with expected theoretical clear-sky LWR↓. The corrected LWR↓ exhibited good agreement with that of collocated WHOI measurements, with a correlation of 0.93. This method is applied to the OMNI field measurements and again compared with the nearby WHOI mooring measurements, exhibiting a better correlation of 0.95. This work has led to the revamping of radiation measurements in OMNI buoys and provides a reliable method to correct past measurements and improve estimation of air–sea fluxes in the Indian Ocean. Significance Statement: Downwelling longwave radiation (LWR↓) is an important climate variable for calculating air–sea heat exchange and quantifying Earth's energy budget. An intercomparison of LWR↓ measurements between ocean observing platforms in the north Indian Ocean revealed a systematic offset in National Institute of Ocean Technology (NIOT) Ocean Moored buoy Network for north Indian Ocean (OMNI) buoys. The observed offset limited our capability to accurately estimate air–sea fluxes in the Indian Ocean. The sensor measurements were compared with a standard reference system, which revealed problems in thermopile amplifier as the root cause of the offset. This work led to the development of a reliable method to correct the offset in LWR↓ and revamping of radiation measurements in NIOT-OMNI buoys. The correction is being applied to the past measurements from 12 OMNI buoys over 8 years to improve the estimation of air–sea fluxes in the Indian Ocean. [ABSTRACT FROM AUTHOR]

Current glacier melt rates in West Antarctica substantially exceed those around the East Antarctic margin. The exception is Wilkes Land, where for example Totten Glacier underwent significant retreat between 2000 and 2012, underlining its sensitivity to climate change. This process is strongly influenced by ocean dynamics, which in turn changes in accordance with the evolution of the ice caps. Here, we present new oceanographic data (temperature, salinity, and dissolved oxygen) collected during austral summer 2017 offshore the Sabrina Coast (East Antarctica) from the continental shelf break to ca 3000 m depth. This area is characterized by very few oceanographic in situ observations. The main water masses of the study area, identified by analysing thermohaline properties, are the Antarctic Surface Water with potential temperature θ>-1.5 ∘C and salinity S<34.2 (σθ<27.55 kgm-3), the Winter Water with -1.92<θ<-1.75 ∘C and 34.00 ∘C and S>34.5 (σθ>27.7 kgm-3), and Antarctic Bottom Water with -0.50<θ<0 ∘C and 34.6328.30 kgm-3). The latter is a mixture of dense waters from the Ross Sea and Adélie Land continental shelves. Such waters are influenced by the mixing processes they undergo as they move westward along the Antarctic margin, also interacting with the warmer Circumpolar Deep Water. The spatial distribution of water masses offshore the Sabrina Coast also appears to be strongly linked with the complex morpho-bathymetry of the slope and rise area, supporting the hypothesis that downslope processes contribute to shaping the architecture of the distal portion of the continental margin. Oceanographic data presented here can be downloaded from 10.25919/yyex-t381 (CSIRO; Van Graas, 2021). [ABSTRACT FROM AUTHOR]

Baynes Sound (BS), located in the waters of Georgia Strait, British Columbia (B.C.), is considered one of the most prolific production sites for bivalve culture in B.C. Bivalve production is influenced by a balance of water quality, hydrodynamics (bay flushing), and food supply (plankton). An ecological carrying capacity assessment is required to assess this balance, where mathematical models can integrate these complex interactions using a highresolution spatially-explicit model. The Finite Volume Community Ocean Model (FVCOM) was coupled with a Bivalve Culture Ecosystem Model (BiCEM) resorting to the Dynamic Energy Budget (DEB) to simulate bivalve physiology and their interactions with the ecosystem. These models were previously developed to address aquaculture issues in the Broughton Archipelago and Discovery Islands regions of B.C. The physical oceanographic conditions are simulated using FVCOM, analogous to previous aquaculture-motivated applications in the Broughton Archipelago and Discovery Islands. Both oceanographic observations and FVCOM outputs show a characteristic two-layered estuarine circulation over BS. This estuarine circulation appears to be strengthened or weakened by river run-off and atmospheric forcing on a seasonal scale and constitutes an overall key feature for the Sound's water inner circulation and exchange with the Strait of Georgia (SoG). The biogeochemical processes are simulated using BiCEM, which predicted that wind forcing, tidal mixing, and estuarine residual circulation contribute to the regular nutrient replenishment from the deep waters of the SoG, leading to high levels of pelagic primary productivity (phytoplankton). In turn, this phytoplankton productivity supports the potential for secondary production of zooplankton and bivalve culture. In general, the response of zooplankton and wild bivalve populations to the existing shellfish aquaculture activity indicates a system within the bounds of its ecological carrying capacity. Although the planned expansion of additional farm coverage and stock, currently under review, would impose an increased demand on the Sound's pelagic resources, the results do not indicate that the additional bivalve production could not be sustained. However, a precautionary approach should be considered with high-stocking scenarios and concentrated areas, such as, Fanny, Mud, and Deep Bays. Gradual aquaculture development in concert with proper monitoring of environmental and cultured shellfish conditions (Research Paper #2) in sensitive areas may provide sustainability of BS. [ABSTRACT FROM AUTHOR]

Historically, energy constraints have limited the spatial range, endurance and capabilities of ocean observation systems. Recently developed wave energy conversion technologies have the potential to help overcome these limitations by providing co-located and persistent power generation for ocean observations, enabling new opportunities for ocean research. In this paper, we develop the first techno-economic model for wave-powered ocean observation systems and use the model to study system characteristics and cost drivers. Our model utilizes time-domain simulation and optimization to identify cost-optimal system characteristics and to estimate capital and operational costs. Using our model, we evaluate the use of wave energy to power a 200 W ocean observation system deployed for five years at five unique geographic locations. We found that, depending on the geographic location, cost-optimal wave energy powered systems require an ≈ 0.5–3 kW wave energy converter and an ≈ 15-50 kWh battery. The corresponding range of power system costs over the deployment duration is between $110,800 and $673,200. We build on these results by performing a sensitivity analysis of key model parameters and identifying the potential economic impact of future technology advancements. Overall, our results indicate that characteristics of the geographic location, power system durability, and electrical power demand are key drivers of power system economics for ocean observing. • For a 200 W load, ∼0.5–3 kW WECs and ∼15–50 kWh battery banks are cost-optimal. • Geographical variations, durability, and power demand are primary economic drivers. • Battery replacements are not required throughout a five year system lifetime. • Changes in service intervals do not affect cost-optimal power system capacities. [ABSTRACT FROM AUTHOR]

In the Sea of Japan, changes in the oceanographic conditions affect fisheries, and new phenomena such as blooms of the harmful dinoflagellate Margalefidinium polykrikoides and mass occurrences of the giant jellyfish Nemopilema nomurai have been observed since the 2000s. In order to elucidate and formulate countermeasures to such new issues, it is essential to enhance the oceanographic/biological data. However, data especially on the phytoplankton assemblage are limited. In the present study, we investigated the population dynamics of the phytoplankton community together with environmental factors at two stations off Tajima, southwestern Sea of Japan for seven fiscal years from September 2009 to March 2016. The oceanographic observations revealed the general pattern in the seasonal and annual abundance of phytoplankton off Tajima. The major component of size-fractionated chlorophyll a concentrations were micro-size (filtered pore size: >10 µm). The results indicated that there was usually a low abundance of phytoplankton in this area. Relatively high abundances (cell densities over 100 cells mL-1) of micro-sized phytoplankton were observed only in spring, but total cell densities were less than 10 cells mL-1 in most months of the other three seasons. The major phytoplankton component was diatoms. Based on the abundance and frequency, the dominant seven diatom taxa were classified into three groups: Skeletonema spp., Thalassiosira spp. and Eucampia zodiacus were dominant in spring, Chaetoceros spp. and Pseudo-nitzschia spp. were dominant in spring and autumn, and Rhizosolenia spp. and Leptocylindrus danicus were dominant in autumn. [ABSTRACT FROM AUTHOR]