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Measurements of oceanographic characteristics, currents, and tides in the Fram Strait and the Greenland Sea are analyzed using historical measurement data. Measurements on moorings across the Fram Strait made it possible to estimate the speeds of the East Greenland and West Spitsbergen currents. It is shown that the speeds of these currents are low (within 10 cm/s) and the amplitudes of the speed of tidal currents are two or more times greater. Tidal currents are intensifying on the shelf of Greenland and Svalbard. Direct measurements are compared with the University of Oregon barotropic tide model. [ABSTRACT FROM AUTHOR]

Below the surface of the ocean, currents, eddies, and other physical processes redistribute energy and biologically important elements. Measuring this transport can be challenging, and scientists must address a wide spectrum of oceanographic and engineering concepts when designing instruments to observe these processes. In this activity, high-school aged students are asked to consider some of these challenges by using easily-available material to design, assemble, and test their own simple deep-water floats, mimicking a tool used by oceanographers to measure transport below the ocean's surface. Students are asked to build floats that are neutrally buoyant at an interface between oil and water, teaching them key oceanographic concepts such as buoyancy and ocean stratification. Additionally, students manage a budget by selecting cost-effective materials to construct their floats. This activity aims to increase students' understanding of how ocean currents affect our planet's climate and ecosystems, how we observe these phenomena, and some of the practical challenges that oceanographers face. The project supports key educational standards and aims to deepen students' appreciation for marine science. [ABSTRACT FROM AUTHOR]

Understanding the wave and current conditions of coral reef ecosystems is essential for maintaining their health, as many reef processes are controlled by these hydrodynamic conditions. In this study, high-frequency measurements of tides, waves, and currents were made using acoustic, electromagnetic, and pressure instruments over a 28-d period on the fore-reef and reef flat of a coral reef atoll in the South China Sea. The research revealed wave transformation, tidal and wave modulation of flow, and wave setup conditions for the first time at this typical atoll. Three large wave processes dominated by gravity waves (GWs) are observed in the fore-reef. The GWs are significantly attenuated on the reef flat, whereas infragravity (IG) waves strengthened. The tidal modulation of GWs and IG waves on the reef flat is significant when the incident wave height exceeded 1 m. In the fore-reef, the modulation of progressive tidal waves and large waves leads to relatively stronger upper-layer currents, and weak near-bottom currents are primarily attributed to the dissipation of tidal wave energy by the rough coral terrain. In calm conditions, flow variations on the reef flat are modulated by tides, thereby allowing seawater flow to pass through the reef flat during spring tides. Conversely, during periods with large waves, tidal modulation of flow on the reef flat is less significant, and the cross-reef flow velocity increases with increasing incident wave height. The occurrence of wave setup on the reef flat enhances cross-reef flow towards the lagoon. The wave setup is positively linearly correlated with the incident wave height. The magnitude of wave setup is associated with the distance between the measurement sites on the fore-reef and reef flat. [ABSTRACT FROM AUTHOR]

The objective was to construct and test an economical, accurate, and open‐source Lagrangian drifter design suitable for lakes <200 km2. Lagrangian drifters are used to trace water currents in marine and freshwater settings and comprise of a low‐friction surface float containing instrumentation for location and environmental measurement, tethered to a high‐friction drogue at the depth of interest. Oceanic drifters are robust but expensive, and this design tailored to inland lake waterbodies fills a durability and cost gap for lake environments. Water‐following characteristics were tested using theoretical drag coefficient calculations, practical drag measurements, and comparison of wind and drifter vectors while deployed on two deep inland lakes (maximum area 175 km2) in the Finger Lakes region of New York, USA. The ratio of drag between float and drogue met or exceeded the minimum value of 40 recommended in the literature, and the vectors of wind and drifter during deployment were independent of one another, meaning the device accurately traced the movement of water currents at depth without undue influence of wind and waves. Each device cost USD $265 in 2021 and was built from materials readily available at hardware and sporting goods stores, allowing their use by research institutions and communities with smaller budgets. This design reliably measured lake currents at sampling depths that ranged from 2 to 30 m. We anticipate that this design will have application to a wide range of hydrodynamic and ecological research where empirical insights to physical processes like lake currents are sought by scientists and managers. Plain Language Summary: Lake currents are complex, yet often lack data for scientists to analyze them. We built and tested a low‐cost, accurate device that can follow water currents in lakes, made from easily available parts. Unlike similar devices for oceans which can be bulky and costly, this device is well‐suited for lakes. It works by floating on the water's surface and has a part that hangs below it in the water to track water movement at different depths. Tests in two New York lakes showed it does a great job of tracking water without being thrown off by wind or waves. Making each device costs USD $265, using parts found in regular stores, so it's affordable for smaller research teams or local communities. It's good for studying water movements from near the surface down to 30 m or even deeper, helping scientists and local managers learn more about how water moves in lakes. Key Points: An economical, open‐source Lagrangian drifter designed to collect current data on lakes <200 km2 was evaluated against existing designsThe new design was tested in deep inland lakes in the Finger Lakes region of New York, USA and is effective at tracking deep currentsThe ease and low‐cost of fabrication and launch/recovery should facilitate use of this design by less‐advantaged communities & researchers [ABSTRACT FROM AUTHOR]

A global inventory of extractive species mariculture in wave-exposed temperate waters shows that the longline is the technology used in more than 99% of the sites (Part 1 of this review). In this second part, I compare the static (longline at rest), quasi-static (tidal sea surface elevation, steady currents and mainline lifting operation) and dynamic (wind seas and swells) loading and motion of surface, semi-submerged and fully submerged longlines used to grow bivalves and kelp. This review is based on a hundred papers published on the subject mostly after 2010 and on simple analytical models used to illustrate the many compromises that must be made to ensure the survivability of the structure and the survival (retention), growth and quality of the cultured biomass. Surface longlines are unsuitable for fully exposed environments. To mitigate storm energy it is necessary to minimize the volume of surface buoys and submerge the mainline to the maximum depth possible. There is however a limit to minimizing the volume of surface buoys due to the uplifting of the mainline by currents. In the case of kelp, its optimal growing depth is within a few meters from the sea surface. This limitation can be partly circumvented by having the kelp float above the mainline. In the case of bivalves, mainline depth can be tens of meters below the sea surface. This comes with some disadvantages including difficulties in maintaining the delicate buoyancy balance, particularly for fully submerged longlines without legs, and reduced access to the mainline, particularly for fully submerged longlines with legs. Devices that allow autonomous or remote-controlled changes of mainline depth on a daily, occasional (husbandry and harvest operations) or seasonal basis have been tested but are not yet used commercially on longlines. [ABSTRACT FROM AUTHOR]

The content and distribution of precious metals in fine-grained bottom sediments, accumulated in the technogenic period (last decades) in the southwestern part of the Chukchi Sea, have been studied. The ubiquitous or local enrichment of the sediments with silver, gold, platinum, and palladium according to the average for the Earth's crust, as well as their enrichment with gold and palladium relative to pre-technogenic (Late Holocene) deposits, was shown. Differences in the conditions of the accumulation of precious metals in the Late Holocene and modern sediments were shown. Sources of input were determined, and the possibility of technogenic enrichment of the sources was proved by the methods of multicomponent statistical analysis of the total chemical composition of the sediments. [ABSTRACT FROM AUTHOR]

We study the near-inertial response of the salinity-stratified north Bay of Bengal to monsoonal wind forcing using 6 years of hourly observations from four moorings. The mean annual energy input from surface winds to near-inertial mixed layer currents is 10–20 kJ m−2, occurring mainly in distinct synoptic "events" from April–September. A total of fifteen events are analyzed: Seven when the ocean is capped by a thin layer of low-salinity river water (fresh) and eight when it is not (salty). The average near-inertial energy input from winds is 40% higher in the fresh cases than in the salty cases. During the fresh events, 1) mixed layer near-inertial motions decay about two times faster and 2) near-inertial kinetic energy below the mixed layer is reduced by at least a factor of three relative to the salty cases. The near-inertial horizontal wavelength was measured for one fresh and one salty event; the fresh was about three times shorter initially. A linear model of near-inertial wave propagation tuned to these data reproduces 2); the thin (10 m) mixed layers during the fresh events excite high modes, which propagate more slowly than the low modes excited by the thicker (40 m) mixed layers in the salty events. The model does not reproduce 1); the rapid decay of the mixed layer inertial motions in the fresh events is not explained by the linear wave propagation at the resolved scales; a different and currently unknown set of processes is likely responsible. [ABSTRACT FROM AUTHOR]

We prove that the area of each nonflat genus zero free boundary minimal surface embedded in the unit 3-ball is less than the area of its radial projection to S 2 . The inequality is asymptotically sharp, and we prove any sequence of surfaces saturating it converges weakly to S 2 , as currents and as varifolds. [ABSTRACT FROM AUTHOR]

Submarine pockmarks are typical indicators of submarine gas escape activity. The deep strata of the Xisha Uplift are rich in biogenic and thermogenic gas, accompanied by strong bottom current activity. Investigating the effects of controlling submarine gas escape and bottom current activity on the formation and development of pockmarks in the Xisha Uplift is significant for understanding the evolution of submarine topography and geomorphology. This study utilized high-resolution multibeam data to identify 261 submarine pockmarks in the northwest of the Xisha Uplift. These pockmarks were categorized based on their morphology into circular, elliptical, elongated, crescent-shaped, and irregular types. The diameters of pockmarks in the study area range from 0.21 to 4.96 km, with maximum depths reaching 30.88 m. Using high-resolution multi-channel seismic data, we conducted a detailed analysis of the subsurface strata characteristics of the pockmarks, identifying chaotic weak reflections, bright spots, and high-angle reflectors. We believe that deep gas in the northwest of the Xisha Uplift escapes to the seafloor through migration pathways, such as faults, fractures, and gas chimneys, resulting in the formation of submarine pockmarks. Bottom current activity has a significant impact on already-formed pockmarks. Crescent-shaped and elongated pockmarks in the Xisha Uplift are largely the result of bottom current modifications of pre-existing pockmarks. [ABSTRACT FROM AUTHOR]

Abstract—The Southern Ocean plays a key role in the global circulation of the World Ocean. The Weddell Gyre, being one of the two gyres that determine the large-scale dynamics of the Southern Ocean, makes a significant contribution to the global thermohaline circulation. In this regard, the study of the dynamics and structure of waters in the Weddell Sea is very relevant for improving our understanding of the processes occurring in the World Ocean. In this work, the vertical structure of currents on the slope in the western part of the Weddell Sea (northwestern and southern parts) was studied based on an array of data on current velocities from moorings collected from an open source (Pangaea). The main result of the analysis of mean velocity of currents is the intensification of currents in the bottom layer. It is likely that this effect is a characteristic feature of the Weddell Gyre both in its western and southern branches. An increase in velocities in the bottom layer at individual moorings at separate locations, previously noted in publications, was confirmed and shown based on an array of data on current velocities from 108 sensors at 37 moorings on the continental slope in the northwestern and southern parts of the Weddell Sea. [ABSTRACT FROM AUTHOR]

Beach morphology assessment is very important for the sustainable development of beaches and the implementation of beach development activities through management plans. The present study focuses on assessing beach morphology and developing ecosystem-based conservative strategies to control beach erosion and improve beach safety along the two blue-flag certified beaches, Padubidri and Kasarkod, in Karnataka state. The bathymetry of the two beaches varies by gradient changes between the winter and monsoon seasons, and as a result, waves break at a distance of 15–25 m from the shore. The estimated seabed deposition between the winter and monsoon periods of 2020 is 10329 cu m and 59.36 cu m at the Padubidri and Kasarkod beaches, respectively. This study also provides the rate of shoreline change at two beaches along the coast for the period 2018–2022, as measured using geospatial technology and field investigation. The assessment revealed that the Kasarkod and Padubidri coasts experienced maximum erosion of 11.7% and 12.7%, respectively for five years. The projected shoreline changes under the climate change show erosion of 59.12 m on the northern side and accretion of about 16.13 m on the southern side of Kasarkod Beach, whereas on Padubidri Beach, erosion of 40 m on the central part of the beach between 2020 and 2030. The nearshore current magnitude is stronger at the coast of Padubidri than at Kasarkod during the study. The sediment movement from the Kamini River at the Hejamadi endpoint (southern part of Padubidri) shapes the Padubidri beach and causes accretion and erosion during winter and monsoon seasons respectively. However, these beaches are being protected by ecosystem-based conservative strategies such as beach vegetation and dune conservation through the Beach Environment and Aesthetics Management Services (BEAMS) program. Therefore, the assessment of beach morphology and conservation strategies provides a better beach management plan, to control beach erosion, and enhance beach stability. [ABSTRACT FROM AUTHOR]

Hydrodynamic processes are a major driver for marine systems, linking marine organisms with their environment. However, a lack of hydrodynamic data at an ecologically relevant spatial resolution has stymied our understanding of reef function, as exemplified by Lizard Island on the Great Barrier Reef. To address this gap, 23 to 27 Marotte HS current meters were deployed over three periods, collecting 15 months of current velocity data. Combining these data with wind and tide datasets, we provide a preliminary description of the circulation in the Lizard Island lagoon, examining wind and tide influence, and flushing time. During south-easterly trade winds, flood tides flow through the Lagoon Entrance, while wind-induced waves cross the Bird-South crest, driving a north-westerly flow through Loomis Channel and across the western lagoon. Ebb tides flow east–south-east through the Lagoon Entrance and south-west through the Palfrey-South channel. Tides contribute a mean of 20.4% to the overall current speed, particularly in deeper sites with less reef interference, while shallow sites were more influenced by wind. Lizard Island lagoon flushing times ranged from a few hours to 10 days; longer during periods with low wind speeds. Hindcast flushing times during the 2016 coral bleaching event (following 8 Degree Heating Weeks) were approximately 22 h, suggesting that flushing time likely had minimal influence on bleaching. Our analyses provide initial insights into the circulation of the Lizard Island system and aid understanding of the potential relationships between reef organisms and their physical environment, bridging the gap between ecology and hydrodynamics. [ABSTRACT FROM AUTHOR]

The 1859 Carrington event is the most intense geomagnetic storm in recorded history, and the literature provides numerous explanations for what drove the negative H perturbation on the Earth. There is debate on what dominated the event. Our analysis shows a combination of causes of similar orders of magnitude. Previous analyses generally rely upon the observed H perturbation at Colaba, India; historic newspaper reports; and empirical models. We expand the analysis using two Space Weather Modeling Framework simulations to examine what drove the event. We compute contributions from currents and geospace regions to the northward B field on Earth's surface, BN. We examine magnetospheric currents parallel and perpendicular to the local B field, ionospheric currents, and gap region field–aligned currents (FACs). We also evaluate contributions from the magnetosheath, near–Earth, and neutral sheet regions. A combination of currents and geospace regions significantly contribute to BN on the Earth's surface, changing as the storm evolves. At storm onset, magnetospheric currents and gap–region FACs dominate in the equatorial region. At auroral latitudes, gap–region FACs and ionospheric currents are the largest contributors. At storm peak, azimuthal magnetospheric currents and gap–region FACs dominate at equatorial latitudes. Gap–region FACs and ionospheric currents dominate in the auroral zone, down to mid‐latitudes. Both the magnetosheath and FACs contribute at storm peak, but are less significant than that from the near–Earth ring current. During recovery, the near–Earth ring current is the largest contributor at equatorial latitudes. Ionospheric currents and gap–region FACs dominate in the auroral zone. Key Points: Prior Carrington event analyses attributed the ΔH perturbation observed on Earth to various causes, with debate on which dominatedUsing MHD simulations, we compute how currents in various systems and geospace regions contribute to ΔHRather than a dominant contributor, we find that multiple current systems and regions contribute with the same order of magnitude [ABSTRACT FROM AUTHOR]

Reconstructing the field of currents using remote sensing methods is a traditional task of oceanology. Satellite instruments such as altimeters, Doppler radars, and optical sensors are routinely used to solve oceanological problems for waters with large dimensions (open areas of the seas and oceans). The latter work well for reservoirs with significant water temperature gradients when applying the method of processing successive satellite images with varying time delays. Less commonly, areas of intense phytoplankton blooms, which are usual for productive waters, are used as markers for image matching. Such waters can be monitored with satellite ocean color sensors that provide high spatial resolution. The goal of the present paper is to investigate the possibility of reconstructing the flow field in the Gorki Reservoir, as an example of a medium-sized eutrophic reservoir, from sequent images of two different high-resolution ocean color sensors with a short time delay between images. This paper describes the field experiment under the satellite overpasses and presents the results of applying the maximum correlation method to two satellite images for the retrieval of the current field in comparison with shipboard data. It is shown that the proposed method has prospects for development. [ABSTRACT FROM AUTHOR]

In this survey we gather several results related to the set of m-subharmonic functions and m-positive currents. We focus on recent studies of the Hessian operator acting on the set of m-subharmonic functions as well as the same operator when it is associated to an m-positive closed current. [ABSTRACT FROM AUTHOR]

We derive several properties of the heat equation with the Hodge operator associated with the Rumin’s complex on Heisenberg groups and prove several properties of the fundamental solution. As an application, we use the heat kernel for Rumin’s differential forms to construct a Calderón reproducing formula on Rumin’s forms.

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

European navigation in the age of sail owes much to the scientific revolution of the seventeenth century and the development of instruments and advanced mathematical techniques. Important though these developments were, it is argued here that close observation of the environment: of the weather, ocean currents, clouds, birds, mammals, and a host of other factors played a far more important role in safe navigation from one part of the globe to another. [ABSTRACT FROM AUTHOR]

The potential hazard arising from the actions taken by the Japanese government regarding the discharge of technical radioactive water from the Fukushima-1 nuclear power plant storage facilities is studied. The contamination of the South Kuril Fishing Zone (SKFZ), which is one of the most promising fishing areas for the Russian Federation, with radioactive particles is considered. Based on the modeling of transport of passive markers simulating radioactive contamination, the pathways and mechanisms of pollution transfer to the SKFZ are analyzed. This research was conducted using altimetric data on the geostrophic speed for the period from August 24, 2022, to August 24, 2023. The transfer of pollution into the SKFZ is determined by a set of conditions related to the current regime of development of the First Kuroshio Meander and the local vortex system of various signs, both near the discharge site and at the SKFZ boundary. A seasonal dependence of the speed and quantity of infiltration of the polluted water toward the shores of the Russian Federation is established. The possibility of rapid advection of pollution into the SKFZ within 13 days is discovered. This speed is determined by the entrainment of contamination by the Kuroshio Meander and its further transport by the mesoscale vortex system to the SKFZ boundaries. The periodicity in the influx of pollution into the SKFZ is revealed. Graphs showing the distribution of the count of "dirty" markers with respect to the times of their release and the arrival of polluted water at the SKFZ boundary are constructed. [ABSTRACT FROM AUTHOR]

This paper tries to review and represent the earlier work about simulating the streams in Batabano Bay in Cuban waters. The simulation operating system, SIMulation of Currents (SIMCO), is a part of a method to predict sea flows into Cuban shelf. This method is set up on a lineal model. Batabano Gulf is a nearly enclosed shallow water area with smooth bottom, with a surface of 20850 km2 and its average depth is around 6m. In this paper the outcomes of such an assessment of the application of SIMCO to Gulf of Batabano and its flows are compared. SIMCO is a suitable model to analyze the water currents of the gulf. When SIMCO run with the horizontal resolution of 2min, the overestimation mean error is equal to 3.8cm/s for the south borderline of gulf and the overestimation errors reduces when the horizontal resolution increases. [ABSTRACT FROM AUTHOR]

The article presents observations of near-inertial internal waves (NIWs) in the slope waters of the Black Sea in winter and summer. Rotary spectral analysis of a time series of sea current velocity measurements revealed the prevailing anticyclonic component of the motions near the local inertial frequency f. The clockwise rotation of the velocity vector with depth implies that the NIWs propagate downwards. The amplitude of NIWs usually was 0.1–0.2 m s−1. NIWs were observed in the layer of the permanent pycnocline and the seasonal pycnocline, which attenuate below depths of 160 m and 80 m in winter and summer, respectively. The amplitude of the near-inertial kinetic energy (NIKE) showed a close relationship with vertical stratification. During winter, NIKE exhibited maximum values in the layer of the permanent pycnocline, whereas, in summer, it was primarily observed in the seasonal pycnocline layer. The near-inertial oscillations were generally more energetic in winter. [ABSTRACT FROM AUTHOR]

Submarine pockmarks are typical indicators of submarine gas escape activity. The deep strata of the Xisha Uplift are rich in biogenic and thermogenic gas, accompanied by strong bottom current activity. Investigating the effects of controlling submarine gas escape and bottom current activity on the formation and development of pockmarks in the Xisha Uplift is significant for understanding the evolution of submarine topography and geomorphology. This study utilized high-resolution multibeam data to identify 261 submarine pockmarks in the northwest of the Xisha Uplift. These pockmarks were categorized based on their morphology into circular, elliptical, elongated, crescent-shaped, and irregular types. The diameters of pockmarks in the study area range from 0.21 to 4.96 km, with maximum depths reaching 30.88 m. Using high-resolution multi-channel seismic data, we conducted a detailed analysis of the subsurface strata characteristics of the pockmarks, identifying chaotic weak reflections, bright spots, and high-angle reflectors. We believe that deep gas in the northwest of the Xisha Uplift escapes to the seafloor through migration pathways, such as faults, fractures, and gas chimneys, resulting in the formation of submarine pockmarks. Bottom current activity has a significant impact on already-formed pockmarks. Crescent-shaped and elongated pockmarks in the Xisha Uplift are largely the result of bottom current modifications of pre-existing pockmarks.

AbstractKinetic energy associated with inertia–gravity waves (IGWs) and other ageostrophic phenomena often overwhelms kinetic energy due to geostrophic motions for wavelengths on the order of tens of kilometers. Understanding the dependencies of the wavelength at which balanced (geostrophic) variability ceases to be larger than unbalanced variability is important for interpreting high-resolution altimetric data. This wavelength has been termed the transition scale. This study uses acoustic Doppler current profiler (ADCP) data along with auxiliary observations and a numerical model to investigate the transition scale in the eastern tropical Pacific and the mechanisms responsible for its regional and seasonal variations. One-dimensional kinetic energy wavenumber spectra are separated into rotational and divergent components, and subsequently into vortex and wave components. The divergent motions, most likely predominantly IGWs, account for most of the energy at wavelengths less than 100 km. The observed regional and seasonal patterns in the transition scale are consistent with those from a high-resolution global simulation. Observations, however, show weaker seasonality, with only modest wintertime increases in vortex energy. The ADCP-inferred IGW wavenumber spectra suggest that waves with near-inertial frequency dominate the unbalanced variability, while in model output, internal tides strongly influence the wavenumber spectrum. The ADCP-derived transition scales from the eastern tropical Pacific are typically in the 100–200-km range.

DeMarco, Krieger, and Ye conjectured that there is a uniform bound B , depending only on the degree d , so that any pair of holomorphic maps $f, g :{\mathbb {P}}^1\to {\mathbb {P}}^1$ with degree $d$ will either share all of their preperiodic points or have at most $B$ in common. Here we show that this uniform bound holds for a Zariski open and dense set in the space of all pairs, $\mathrm {Rat}_d \times \mathrm {Rat}_d$ , for each degree $d\geq 2$. The proof involves a combination of arithmetic intersection theory and complex-dynamical results, especially as developed recently by Gauthier and Vigny, Yuan and Zhang, and Mavraki and Schmidt. In addition, we present alternate proofs of the main results of DeMarco, Krieger, and Ye [ Uniform Manin-Mumford for a family of genus 2 curves , Ann. of Math. (2) 191 (2020), 949–1001; Common preperiodic points for quadratic polynomials , J. Mod. Dyn. 18 (2022), 363–413] and of Poineau [ Dynamique analytique sur $\mathbb {Z}$ II : Écart uniforme entre Lattès et conjecture de Bogomolov-Fu-Tschinkel , Preprint (2022), arXiv:2207.01574 [math.NT]]. In fact, we prove a generalization of a conjecture of Bogomolov, Fu, and Tschinkel in a mixed setting of dynamical systems and elliptic curves. [ABSTRACT FROM AUTHOR]

Sea surface currents probably are the most relevant essential ocean variable affecting diverse societal challenges concerning the marine environmental (as, for example, safe and efficient navigation, marine pollution and ecological connectivity). This work introduces a climatological Atlas (monthly resolution) of currents in the Mediterranean and Canary–Iberian–Biscay basins, based on today's state of the art reanalyses of the ocean circulation. The focus is on surface and subsurface reanalyses (here understood as $z\sim 0.5$ z ∼ 0.5 and $z\sim 15$ z ∼ 15 m, respectively) provided by the Copernicus Marine Environment Monitoring Service (CMEMS). The climatological values are computed from the median of the empirical probability density functions and the Atlas also includes the variance matrix and a bimodality index to have quantitative information on their variability. For both domains, the subsurface climatological fields are reasonably consistent with circulation schemes proposed in the previous literature but clearly improving the time and space resolution of the emerging patterns. For the Canary–Iberian–Biscay domain, the monthly climatological surface currents capture accurately the characteristic seasonal signal and its transition between a favourable and non-favourable upwelling regime. In the Mediterranean basin, differences between the near-surface and the 15 m velocity fields suggest a non-negligible role of winds over the variability of the uppermost ocean layer, specially in the Eastern Mediterranean basin. This is, up to our knowledge, the first time that such near-surface climatological patterns are computed. It has been found that, in general, the resulting patterns agree with surface drifter trajectories. In several regions, interannual variability foster bimodal and multimodal probability distributions. The Atlas has been conceived with the purpose of providing a first quantitative assessment on the surface circulation, thus being a complementary tool of real-time ocean forecasting systems. The Atlas is distributed following the FAIR principles and is accompanied with a digital version, with enhanced visualization capabilities for both research and assessment. [ABSTRACT FROM AUTHOR]

Gas hydrates were found in bottom sediments on the western slope of the Kuril Basin from the side of the Terpeniya Gulf (Okhotsk Sea) at 1020 m depths during expeditions in 2012 and 2013. However, on the eastern slope of the Tatar Strait, gas hydrates were sampled at an unusually shallow 322 m depth. During our research, we identified gas hydrate provinces based on both bottom water and sediment temperature measurement data and heat flow, earthquake, cold seep and sea current data analyses. These provinces have similar hydrological regimes, providing suitable temperature conditions for the existence of gas hydrates, to those at a 322 m depth in the Tatar Strait (Japan Sea) and at 725 and 1020 m depths on the slope of the Kuril Basin (Okhotsk Sea). [ABSTRACT FROM AUTHOR]

The fluctuations in both time and space of larval fish assemblages in relation to hydrographic characteristics in the waters surrounding Taiwan Bank were studied in October 2021 (autumn) and March 2022 (spring). Throughout the study period, we identified a total of 149 taxa of fish larvae, encompassing 96 genera and 71 families. Engraulis japonicus, Diaphus slender type, unidentified Gobiidae, Apogon sp., unidentified Clupeidae, and Benthosema pterotum were the six dominant taxa and together constituted 47.39% of the total catch. There were no notable temporal variations observed in the abundance of fish larvae, but the species number of fish larvae was greater in spring than in autumn. Significant variations in species composition were observed between the different cruises, and the cluster analysis unveiled a distinct temporal structure of the assemblages of fish larvae. The dynamics of the prevailing currents induced by seasonal monsoons contribute significantly to the transportation of fish larvae. The distribution of fish larvae showed a good association with hydrographic characteristics, where seawater temperature and salinity emerged as the primary explanatory factors influencing the composition of larval fish assemblages in the waters surrounding Taiwan Bank. While the increased influx of nutrients from upwelling ensures abundant food availability, the hydrographic conditions may not be suitable for every fish larva. [ABSTRACT FROM AUTHOR]

Many different surface drifter designs have been developed recently to track near-surface ocean currents, but the degree to which these drifters slip through the water because of mechanisms associated with the wind is poorly known. In the 2020 Tracer Release Experiment (TReX), 19 drifters of eight different designs, both commercially available and home-built, were simultaneously released with a patch of rhodamine dye. The dye rapidly spread vertically through the mixed layer but also more slowly dispersed horizontally. Although winds were light, drifters moved downwind from the dye patch at speeds of 3–17 cm s−1 (0.6%–4% of wind speed) depending on the design type. Measurements were made of wind and ocean conditions, and these were incorporated into a boundary layer model at the air–sea interface to estimate complete velocity profiles above and below the surface. Then, a steady-state drag model is used with these profiles to successfully predict drifter slip. Drogued drifters (those with a subsurface drag element) can be affected by Eulerian shear in the upper 0.5 m of the water column, as well as the Stokes drift, but undrogued drifters are in addition greatly affected by direct wind drag, and possibly by resonant interactions with waves. The dye, cycling vertically in the mixed layer, is largely unaffected by all of these factors; therefore, even "perfect" surface drifters do not move with a mixed layer tracer. Significance Statement: Surface drifters are used by oceanographers to measure ocean surface currents. However, different designs also slip downwind through the water at rates that are poorly known but are typically around a few percent of the wind speed. In 2020 we simultaneously deployed drifters of eight different designs along with rhodamine dye in a field experiment to see how well the different designs track the water. Here we independently and successfully model drifter slippage for the different designs. Slip factors are then estimated for a range of wind and ocean conditions. [ABSTRACT FROM AUTHOR]

Coastal zones supporting diurnal shelf waves near the South Kuril Islands were determined based on the analysis of small-scale amplitude and phase variations of diurnal O1 and K1 tidal waves estimated from along-track TOPEX/Poseidon altimetry data. The amplitudes and phases of these waves were revealed not only along the original tracks (1992–2002), but also along those shifted by half the intertrack distance (2002–2005). This made it possible to more accurately determine the zone supporting diurnal shelf waves. It was found that diurnal shelf waves in the form of baroclinic coastal trapped modes strongly influence tidal motions on the oceanic shelf of Urup and Iturup islands. Two wavelengths fit in this section of the shelf (one pair of quasi-stationary eddies is localized on the shelf of Urup Island and a second one on the shelf of Iturup Island). This is an unexpected result, as barotropic shelf modes usually form one pair of eddies (for example, on the northeastern shelf of Sakhalin Island, on the northern shelf of Hokkaido Island and on the oceanic shelf of the North Kuril Islands). We found that the zone of K1 and O1 tidal waves start from Chirpoi Island, which means that shelf waves are generated as a result of the diffraction of a large-scale Kelvin tidal wave in the deep Bussol Strait. The existence of the lower frequency O1 tidal shelf wave was found not only on the shelf of Urup and Iturup islands, but also on the shelf of Shikotan Island, which is consistent with the earlier results of Yefimov and Rabinovich (1980). Diurnal shelf waves cause significant increases in the O1 and K1 amplitudes on the coast of Iturup Island (especially at its southern part) and on Urup Island in comparison with the open ocean, and produce strong instrumentally-observed diurnal tidal currents in these regions. Baroclinic diurnal shelf (coastal trapped) waves also contribute to vertical movements, forcing water temperature variations at sufficiently great depths, which can have a significant impact on the living conditions of benthic communities. [ABSTRACT FROM AUTHOR]

The spatial distribution and seasonal variability of mesoscale eddies in the Sea of Japan have been investigated based on the regional database created from the AVISO Mesoscale Eddies Trajectory Atlas (1993–2020). The database contains information about the trajectories and parameters of mesoscale eddies in the Sea of Japan. The eddy detection method is based on the analysis of altimetric maps of absolute dynamic topography. A total of 578 eddies with a lifetime of more than 90 days have been identified (273 anticyclonic and 305 cyclonic). The average lifetime of eddies is 202 days for anticyclonic and 143 days for cyclonic and mean radius of 58 km for anticyclonic and 61 km for cyclonic. The mean speed of anticyclones and cyclones along their trajectories is 2.8 and 3.7 cm/s; the mean orbital velocities of geostrophic currents are 19.0 and 15.1 cm/s, respectively. The maximum number of cases of formation and destruction of anticyclones falls in July–September during the period with high values of water inflow through the Korea Strait. Most of the cyclonic eddies are generated between January and June and decay during the cold half of the year (October–March). A joint analysis of maps of the mean surface circulation in the Sea of Japan (satellite altimetry data) and the spatial distribution of mesoscale eddy shows that the stable eddies of the Sea of Japan are associated with the quasi-stationary meanders of the East Korea East Korea Warm Curent, Subpolar Front, and Tsushima current. The position of meanders is mainly determined by the interaction of the currents with the bottom topography. [ABSTRACT FROM AUTHOR]

Changes in the coastal zone under the influence of currents of different nature and wind waves are being investigated. A sandy beach located in the water area of the "Park of the 300th Anniversary of St. Petersburg", the Neva Bay of the Gulf of Finland of the Baltic Sea, is considered as an object. The beach is actively affected by wind waves and eventually washes away with the intensity of the retreat of the shore of about 4 m per year. For numerical modeling, a set of models is used: SWAN–wind-wave model and COASTOX-UN–a two-dimensional model of currents, sediment transport and bottom reformation. It was developed a model of the Neva Bay and the mouth of the Neva River from the Flood Prevention Facility Complex in the west to the river Neva near the Liteiny Bridge in the east. Based on the reanalysis of wind data, 36 strong storms were selected for a five-year period from 2014 to 2018, for the sequence of which numerical modeling of waves, currents and lithodynamic processes was carried out. It was obtained balances of alluvial and washouts after a ten-years simulated period for beach sectors. To verify the results, satellite images of the modeling area are used, it was found that the model adequately describes the main observed trends in the development of the beach. [ABSTRACT FROM AUTHOR]

Plastic pollution is a major problem in the world’s oceans (Hale et al., 2020). It is estimated that 10–28 billion pounds of trash entered the oceans in 2010 alone (Jambeck et al., 2015). This plastic is mostly microplastics, or plastic bits smaller than 5 mm (Cozar et al., 2014), which form as plastic products fragment into smaller pieces as they are exposed to environmental conditions. Marine debris researchers are interested in documenting the different types of plastics that accumulate in different oceans, and it is estimated that there are over 170 trillion plastic particles afloat in the world’s oceans today (Eriksen et al., 2023). We have developed a lesson plan by teaming marine science graduate students with K-12 teachers and informal educators, and have incorporated current research into an effective teaching product. In this activity designed for middle school, students will count, graph, compare and contrast, and share results with classmates regarding the plastic in one particular gyre of the ocean. Finally, students will create an action plan to reduce their use of single-use plastics.

Surface-canopy forming kelps (Macrocystis pyrifera and Nereocystis luetkeana) can be monitored along the Northeast Pacific coast using remote sensing. These kelp canopies can be submerged by tides and currents, making it difficult to accurately determine their extent with remote sensing techniques. Further, both species have morphologically distinct canopies, each made up of structures with differing buoyancies, and it is not well understood whether the differing buoyancies between these species’ canopies affects their detectability with remote sensing technologies. Here, we collected in situ above-water spectral signatures for the surface-canopies of Nereocystis and Macrocystis, providing the first direct hyperspectral comparison between the structures that make up the canopies of these species. Additionally, we compare the strength of their red-edge and near-infrared band signals, as well as the normalized difference red-edge (NDRE) and normalized difference vegetation index (NDVI) values. At the bed level, we compare detection of kelp canopy extent using both NDRE and NDVI classified unoccupied aerial vehicle imagery. We also characterized how changing tides and currents submerge the canopies of both species, providing insights that will allow remote sensors to more accurately determine the extent of kelp canopy in remote sensing imagery. Observations of canopy structures paired with in situ hyperspectral data and simulated multispectral data showed that more buoyant kelp structures had higher reflectance in the near-infrared wavelengths, but even slightly submerged canopy structures had a higher reflectance in the red-edge rather than the near-infrared. The higher red-edge signal was also evident at the bed level in the UAV imagery, resulting in 18.0% more canopy classified with NDRE than with NDVI. The area of detected canopy extent decreased by an average of 22.5% per meter of tidal increase at low current speeds (

Continuous two-year studies of particle fluxes and associated environmental parameters in the axial zone of the Arctic segment of the Mid-Atlantic Ridge at the junction of the Mohns and Knipovich ridges (Norwegian Sea) have been carried out for the first time. Sediment traps were deployed from the R/V Akademik Mstislav Keldysh in June 2019 in the northeastern part of the Mohns Ridge with revision in August 2020 and lifting in July 2021. It is shown that the sedimentation of particles in the study area was affected by the global transport of water masses in the northeasterly direction, with Atlantic waters in the subsurface layer and water masses of Arctic origin recirculating deeper in the subsurface. A weak positive temperature trend at a depth of more than 2500 m (0.02°C over two years) is detected. The bimodal vertical distribution of fluxes and changes in the composition of sinking particles corresponded to the pattern of sediment recycling in the ocean. The annual course of fluxes in the subsurface layer is determined by the activity of Si-concentrating and calcifying plankton, while the maximum bloom period is also manifested in the deep layer. At the same time, the main significant source of the flux deeper than 2000 m is the supply of lithogenic matter from the near-bottom nepheloid layer. [ABSTRACT FROM AUTHOR]

The ability to estimate surface current divergence and vorticity from space is assessed from simulated satellite Doppler radar scatterometer measurements of surface velocity with an effective footprint diameter of 5 km across an 1800-km measurement swath. The focus is on non-internal-wave contributions to divergence and vorticity. This is achieved by simulating Doppler radar measurements of surface velocity from a numerical model in which internal waves are weak because of high dissipation, seasonal cycle forcing, and the lack of tidal forcing. Divergence is much more challenging to estimate than vorticity because the signals are weaker and restricted to smaller scales. With the measurement noise that was anticipated based on early engineering studies, divergence cannot be estimated with useful resolution. Recent advances in the understanding of how the noise in measurements of surface currents depends on the ambient wind speed have concluded that measurement noise will be substantially smaller in conditions of wind speed greater than 6 m s−1. A reassessment of the ability to estimate non-internal-wave contributions to surface current divergence in this study finds that useful estimates can be obtained in such wind conditions; the wavelength resolution capability for divergence estimates in the middle of the measurement swaths will be better than 100 km in 16-day averages. The improved measurement accuracy will also provide estimates of surface current vorticity with a resolution nearly a factor of 2 higher than was previously thought, resulting in wavelength resolutions of about 50, 30, and 20 km in snapshots, 4-day averages, and 16-day averages, respectively. Significance Statement: The divergence of surface ocean velocity is of great interest to oceanographers because of its direct relation to the near-surface vertical velocity that has important implications for air–sea exchanges of CO2 and other gases, as well as the supply of nutrients from depth that are critical to biological productivity. Observational estimates of surface divergence are challenging because of the weakness of the divergence signals and the technical difficulties in acquiring two-dimensional observations of velocity with sufficient accuracy and spatial resolution to obtain accurate estimates of the divergence. The analysis presented here concludes that useful estimates of surface current divergence can be obtained from a future Doppler radar satellite mission that is in the early stages of development by NASA. [ABSTRACT FROM AUTHOR]

The development of autonomous surface vehicles, such as the Boeing Liquid Robotics Wave Glider, has revolutionized our ability to collect surface ocean–lower atmosphere observations, a crucial step toward developing better physical understanding of upper-ocean and air–sea interaction processes. However, due to the wave-following nature of these vehicles, they experience rapid shifting, rolling, and pitching under the action of surface waves, making motion compensation of observations of ocean currents particularly challenging. We present an evaluation of the accuracy of Wave Glider–based ADCP measurements by comparing them with coincident and collocated observations collected from a bottom-mounted ADCP over the course of a week-long experiment. A novel motion compensation method, tailored to wave-following surface vehicles, is presented and compared with standard approaches. We show that the use of an additional position and attitude sensor (GPS/IMU) significantly improves the accuracy of the observed currents. [ABSTRACT FROM AUTHOR]

Currents have a significant impact on wave parameters around islands. In this study, high-resolution unsteady current simulations based on island geography and wind fields from Weather Research and Forecasting (WRF) Model are used as input sources. The wave action balance model uses an unstructured grid to assess the wave conditions in the Atoll during Typhoon Noul. The characteristic wave parameters, with and without the effect of currents, are compared with the field observation data, including significant wave height, wave period, and the spatial distribution of significant wave height. The results show that simulated significant wave heights and wave periods are close to observed data, considering the effect of currents. The energy and shape of the spectrum are also verified during Typhoon Noul, and the observed agreement is improved when considering the currents. The effects of current within the Atoll are relatively weaker compared to the surroundings, while stronger current effects are observed in the deeper water outside the Atoll. Refraction caused by current expands the area of moderate sea state behind the island. Significance Statement: Several innovations of this article are as follows: 1) the influence of currents on wave conditions at the Atoll; 2) exploring the impact of currents using key parameters, such as significant wave height, wave period, and wave spectrum, especially during the passage of Typhoon Noul; 3) swell emerges as the dominant factor influencing wave conditions as the center of Typhoon Noul gradually moves away; and 4) refraction caused by current expands the area of moderate sea state behind the island. [ABSTRACT FROM AUTHOR]

The reasons for the origin of narrow time-dependent currents formed in the Black Sea in the lower region of the constant pycnocline and deeper are analyzed on the basis of the results of numerical modeling. The prepositions for the generation of deep-water countercurrents in the hydrophysical fields of the Black Sea are studied with reference to the example of its north-east region, where they manifest themselves most frequently. In September 2016 and February 2017 the countercurrents in the region of the North-Caucasian coast were fixed according to the observation data of the ARGO profiling float ID6901833. On the basis of the numerical model of the Marine Hydrophysical Institute (MHI) with a 1 km-resolution and the assimilated data of the hydrological observations of the temperature and salinity the hydrophysical fields of the Black Sea are numerically simulated for the period of 2016–2017. The results of the calculations are used to reproduce the variations in the deep-water flow directions in the above-noted region and to analyze the fields of the main geophysical parameters, together with their derivative parameters. The effect of the mesoscale anticyclonic eddies and the density gradients on the velocity field structure and variability is illustrated. It is established that countercurrents propagated during several days in the anticyclonic direction, along the continental slope on the horizons from 50–100 to 500 m, and their formation took place in the conditions of the attenuation of the cyclonic Black Sea Rim Current in the upper sea layer and the intensification of the Kerch anticyclone. [ABSTRACT FROM AUTHOR]

This study analyzes horizontal and vertical wind-driven circulation responses in small semienclosed bays, the associated offshore dynamic conditions, and the relative importance of each term in the momentum balance equations using a multiplatform observational system. The observational platform consists of three ADCPs and a land-based radar monitoring the velocity field within the bay and in the contiguous offshore area. The wind-driven patterns in the bay can switch from a barotropic cyclonic or anticyclonic circulation to a two-layer baroclinic mode response as a function of the wind regime (its direction and magnitude). For the baroclinic mode, the vertical location of the inflection point in the velocity profile can vary according to the proximity of the boundary current to the entrance of the bay. The influence of offshore combined meteorological and marine conditions on the inner-bay dynamics is evidenced under moderate to strong wind conditions and is almost nonexistent under negligible wind. The momentum balance analysis as well as the nondimensional numbers evidence the impact of wind stress, coastline shape, stratification, and the nonlinear advective terms. Advection can be at the same order of magnitude as pressure gradient, Coriolis, or wind stress terms and can be greater than the bottom stress terms. The nonlinear terms in the momentum equations are frequently neglected when analyzing wind-driven circulation by means of in situ data or analytical models. [ABSTRACT FROM AUTHOR]

Regulated water bodies like lakes and reservoirs are increasingly becoming an object of attention due to the problems of greenhouse gas emissions, regional ecology, and the necessity to ensure safe environmental management. However, for some local tasks, it is important to assess the contribution of a hydroelectric power plant (HPP) to various parameters of the nearest water environment, for example, mortality of zooplankton, transfer of suspended matter and phytoplankton, formation of secondary deposits, methane emissions, spatial features of stratification, etc. An example of such studies is the present paper. It is based on unique data of complex measurements of hydrophysical, hydrooptical, hydrobiological, and hydrochemical water parameters, as well as methane fluxes, that were collected at the Gorky Reservoir nearby a HPP in the spring, summer, and autumn of 2022. Preliminary correlations between these parameters were obtained. The results are useful for the correct interpretation of satellite images of inland waters, quantitative description of HPPs' influence on the water environment, knowledge of the main patterns of transformation of aquatic organism communities under conditions of runoff regulation, determination of water quality by hydrobiological parameters, development of mechanisms for improving the ecological state of water bodies, and accounting spatial heterogeneity of methane flows from the surface of the reservoir. [ABSTRACT FROM AUTHOR]