Physical Oceanography

Physical oceanography is the study of physical conditions, processes and variables within the ocean, including temperature–salinity distributions, mixing of the water column, waves, tides, currents and air–sea interaction processes. Here we provide a critical review of how satellite sensors are being used to study physical oceanography processes at the ocean surface and its borders with the atmosphere and sea ice. The paper begins by describing the main sensor types that are used to observe the oceans (visible, thermal infrared and microwave) and the specific observations that each of these sensor types can provide. We then present a critical review of how these sensors and observations are being used to study: (i) ocean surface currents, (ii) storm surges, (iii) sea ice, (iv) atmosphere–ocean gas exchange and (v) surface heat fluxes via phytoplankton. Exciting advances include the use of multiple sensors in synergy to observe temporally varying Arctic sea ice volume, atmosphere–oce...

Diatoms tend to dominate the Arctic spring bloom, a key event in the ecosystem. Large sinking of diatoms is expected at the end of the bloom driven by deteriorated cell status associated to nutrients (silicon) depletion. However, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic 25 layer and assess their cell health status. The communities were sampled around the Svalbard Islands and encompassed a broad diversity of conditions and bloom stages. About 1/4 (mean±SE 24.2 ± 6.7 %) of the total water column (max. 415 m) diatom stock was found below the photic layer, indicating significant sinking of diatoms in the area. The fraction of living diatom cells in the photic layer averaged 59.4 ± 6.3 % but showed the highest percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were 30 dominated by dead cells (20.8 ± 4.9 % living cells). The percentage of diatom's stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. An experiment on board in a tall (1.35 m) sedimentation column confirmed that dead diatom cells from the Arctic community sank faster that living ones. Also, diatoms cell mortality increased in darkness, showing an averaged half life of 1.025 ± 0.075 d -1 . The results conform to a conceptual model where 35 diatoms grow during the bloom until silicic acid stocks are depleted, and support a link between diatom cell health status and sedimentation fluxes in the Arctic. Healthy arctic phytoplankton communities remained at the photic layer, whereas dying communities exported a large fraction of the biomass to the aphotic zone, fuelling carbon sequestration and benthic ecosystems.

Results from 3 yr of hydrographic time series are shown for Willapa Bay, Washington, a macrotidal, partially mixed estuary whose river and ocean end members are both highly variable. Fluctuating ocean conditionsalternations between wind-driven upwelling and downwelling, and intrusions of the buoyant Columbia River plume-are shown to force order-of-magnitude changes in salinity gradients on the event (2-10 day) scale. An effective horizontal diffusivity parameterizing all up-estuary salt flux is calculated as a function of riverflow: results show that Willapa's volume-integrated salt balance is almost always far from equilibrium. At very high riverflows (the top 15% of observations) the estuary loses salt, on average, while at all other riverflow levels it gains salt. Under summer, low-riverflow conditions, in fact, the effective diffusivity K is large enough to drive a net increase in salinity that is 3-6 times the seaward, river-driven salt flux. This diffusion process is amplified, not damped, by increased tidal forcing, contrary to the expectation for baroclinic exchange. Furthermore, K varies along the length of the estuary as ϳ5% of the rms tidal velocity times channel width, a scaling consistent with density-independent stirring by tidal residuals. To summarize Willapa's event-and seasonal-scale variability, a simple diagnostic parameter space for unsteady estuarine salt balances is presented, a generalization from the Hansen and Rattray steady-state scheme.

Upstream mean semidiurnal internal tidal energy flux has been found in the Gulf Stream in hydrodynamical model simulations of the Atlantic Ocean. A major source of the energy in the simulations is the south edge of Georges Bank, where strong and resonant Gulf of Maine tidal currents are found. An explanation of the flux pattern within the Gulf Stream is that internal wave modal rays can be strongly redirected by baroclinic currents and even trapped (ducted) by current jets that feature strong velocities above the thermocline that are directed counter to the modal wavenumber vector (i.e., when the waves travel upstream). This ducting behavior is analyzed and explained here with ray-based wave propagation studies for internal wave modes with anisotropic wavenumbers, as occur in mesoscale background flow fields. Two primary analysis tools are introduced and then used to analyze the strong refraction and ducting: the generalized Jones equation governing modal properties and ray equations that are suitable for studying waves with anisotropic wavenumbers.

The spectral energy density of the internal waves in the open ocean is considered. The Garrett and Munk spectrum and the resonant kinetic equation are used as the main tools of the study. Evaluations of a resonant kinetic equation that suggest the slow time evolution of the Garrett and Munk spectrum is not in fact slow are reported. Instead, nonlinear transfers lead to evolution time scales that are smaller than one wave period at high vertical wavenumber. Such values of the transfer rates are inconsistent with the viewpoint expressed in papers by C. H. McComas and P. Mu ¨ller, and by P. Mu ¨ller et al., which regards the Garrett and Munk spectrum as an approximate stationary state of the resonant kinetic equation. It also puts the self-consistency of a resonant kinetic equation at a serious risk. The possible reasons for and resolutions of this paradox are explored. Inclusion of near-resonant interactions decreases the rate at which the spectrum evolves. Consequently, this inclusion shows a tendency of improving of self-consistency of the kinetic equation approach.

We provide a first-principles analysis of the energy fluxes in the oceanic internal wavefield. The resulting formula is remarkably similar to the renowned phenomenological formula for the turbulent dissipation rate in the ocean which is known as the Finescale Parameterization. The prediction is based on the wave turbulence theory of internal gravity waves and on a new methodology devised for the computation of the associated energy fluxes. In the standard spectral representation of the wave energy density, in the two-dimensional vertical wavenumber -frequency (𝑚 -𝜔) ___domain, the energy fluxes associated with the steady state are found to be directed downscale in both coordinates, closely matching the Finescale-Parameterization formula in functional form and in magnitude. These energy transfers are composed of a 'local' and a 'scale-separated' contributions; while the former is quantified numerically, the latter is dominated by the Induced Diffusion process and is amenable to analytical treatment. Contrary to previous results indicating an inverse energy cascade from high frequency to low, at odds with observations, our analysis of all non-zero coefficients of the diffusion tensor predicts a direct energy cascade. Moreover, by the same analysis fundamental spectra that had been deemed 'no-flux' solutions are reinstated to the status of 'constant-downscale-flux' solutions. This is consequential for an understanding of energy fluxes, sources and sinks that fits in the observational paradigm of the Finescale Parameterization, solving at once two long-standing paradoxes that had earned the name of 'Oceanic Ultraviolet Catastrophe'.

Eventos de precipitação extrema promovem transporte de sedimentos e o crescimento ou diluição do fitoplâncton. Assim, investigou-se as alterações na concentração de material total em suspensão (MTS) e clorofila-a (CLA) no Litoral Central e Norte de São Paulo, frente ao evento de pluviosidade extrema de fevereiro de 2023. Foram utilizadas seis imagens Sentinel-2, de janeiro a junho/2023. A correção atmosférica e estimativas dos parâmetros foram obtidas por meio do processador C2RCC. Os resultados indicaram aumento das plumas de MTS e CLA ao longo do período analisado, em especial após o evento. Constatou-se a influência de ventos e correntes no transporte das plumas, bem como a descarga de rios locais no litoral norte. Por fim, o processo de aumento de MTS e CLA nas águas costeiras ocorreu por até três meses após o evento. Essas são informações importantes no auxílio de gestores em caso de eventos futuros.

alta frecuencia, a través de simulación numérica. 2017-17008" por el apoyo mensual para el desarrollo de las actividades de este trabajo. Agradecimientos enormes al profesor Vladimir Giovanni Toro, por su desmedido apoyo en este proceso, como asesor, como profesor y como mentor. Por regalarnos y trasmitirnos de su amor y entrega por las ciencias del mar, que será una base para la vida profesional y personal. Agradecemos a la profesora Yuley Cardona, por compartir con nosotros su amor por la investigación y por ser nuestra mentora en este proceso. Por brindarnos de su tiempo y su conocimiento.

Impacts of ocean deoxygenation on fisheries 519 Ocean deoxygenation: Everyone's problem CHAPTER 10 10 Impacts of ocean deoxygenation on fisheries • Fisheries (commercial, artisan, recreational harvest) are an ecosystem service that provide employment and nutrition in the global food system. Worldwide production of capture fisheries has levelled off, while demand continues to increase. Over-harvesting and effects on habitats and the food web switches fisheries from an ecosystem service to a stressor. • Deoxygenation is anticipated to expand over the next decades, and can affect fisheries through negative effects on growth, survival, and reproduction affecting biomass, and movement of fish affecting their availability to harvest. The extent of the deoxygenation effects on fisheries is anticipated to increase because the areas of the ocean that will show increasing deoxygenation overlap with the coastal and oceanic regions that support high fisheries production. • Quantifying the effects of deoxygenation on fisheries is complicated by the effects of co-varying environmental factors and other stressors that also affect the population dynamics of the species of interest, and because the dynamics of oxygen and fisheries (fishers and vessels) are highly site-dependent. Global climate change involves simultaneous changes in temperature, acidity, and oxygen, as well as effects caused by other stressors such as sea-level rise.

Mapping data onto aesthetics refers to how we visually encode data using different levels of representation in charts or graphics. Such visible properties (aesthetics) would better show the patterns, relationships, and insights available. Limited Key aesthetic mappings include position, color, size, shape, and transparency. Data visualization is the process of taking raw data and systematically and logically converting them into visual elements that comprise the final graphic. From that perspective, these variants may look completely different; for example, when viewing a scatter plot, pie chart, and heatmap, one might think these visualizations have no similarities. However, all data visualizations can be described through a common language: a description of how the data values are "mapped" onto graphics which are usually rendered with ink on paper or colored pixels on the screen. The vital thought that should strike one is this: All data visualizations map data values into measurable attributes of the graphic produced.

Book name: Fundamentals of Data Handling and Visualization

This study investigates the connection between gravitational wave detections and celestial alignment patterns, particularly involving the Sun and the Moon. Analysis of 20 known gravitational wave events from 2015 to 2023 revealed that over 80% occurred during periods of close angular alignment (<10°) and minimal perpendicular distance (<50,000 km) to the Moon or the Sun. We propose that gravitational imbalances due to solar and lunar tidal forces may create conditions under which gravitational wave signals become detectable.

Through combining analytical arguments and numerical models, this study investigates the finiteamplitude meanders of shelfbreak fronts characterized by sloping isopycnals outcropping at both the surface and the shelfbreak bottom. The objective is to provide a formula for the meander length scale that can explain observed frontal length scale variability and also be verified with observations. Considering the frontal instability to be a mixture of barotropic and baroclinic instability, the derived along-shelf meander length scale formula is [b 1 /(1 1 a 1 S 1/2 )]NH/f, where N is the buoyancy frequency; H is the depth of the front; f is the Coriolis parameter; S is the Burger number measuring the ratio of energy conversion associated with barotropic and baroclinic instability; and a 1 and b 1 are empirical constants. Initial growth rate of the frontal instability is formulated as [b 2 (1 1 a 1 S 1/2 )/(1 1 a 2 aS 1/2 )]NH/L, where a is the bottom slope at the foot of the front, and a 2 and b 2 are empirical constants. The formulas are verified using numerical sensitivity simulations, and fitting of the simulated and formulated results gives a 1 5 2.69, b 1 5 14.65, a 2 5 5.1 3 10 3 , and b 2 5 6.2 3 10 22 . The numerical simulations also show development of fastgrowing frontal symmetric instability when the minimum initial potential vorticity is negative. Although frontal symmetric instability leads to faster development of barotropic and baroclinic instability at later times, it does not significantly influence the meander length scale. The derived meander length scale provides a framework for future studies of the influences of external forces on shelfbreak frontal circulation and cross-frontal exchange.

The American Physical Society Anisotropic shear dispersion parameterization for ocean eddy transport SCOTT RECKINGER, Montana State University, BAYLOR FOX-KEMPER, Brown University -The effects of mesoscale eddies are universally treated isotropically in global ocean general circulation models. However, observations and simulations demonstrate that the mesoscale processes that the parameterization is intended to represent, such as shear dispersion, are typified by strong anisotropy. We extend the Gent-McWilliams/Redi mesoscale eddy parameterization to include anisotropy and test the effects of varying levels of anisotropy in 1-degree Community Earth System Model (CESM) simulations. Anisotropy has many effects on the simulated climate, including a reduction of temperature and salinity biases, a deepening of the southern ocean mixed-layer depth, impacts on the meridional overturning circulation and ocean energy and tracer uptake, and improved ventilation of biogeochemical tracers, particularly in oxygen minimum zones. A process-based parameterization to approximate the effects of unresolved shear dispersion is also used to set the strength and direction of anisotropy. The shear dispersion parameterization is similar to drifter observations in spatial distribution of diffusivity and high-resolution model diagnosis in the distribution of eddy flux orientation.

The American Physical Society Anisotropic shear dispersion parameterization for ocean eddy transport SCOTT RECKINGER, Montana State University, BAYLOR FOX-KEMPER, Brown University -The effects of mesoscale eddies are universally treated isotropically in global ocean general circulation models. However, observations and simulations demonstrate that the mesoscale processes that the parameterization is intended to represent, such as shear dispersion, are typified by strong anisotropy. We extend the Gent-McWilliams/Redi mesoscale eddy parameterization to include anisotropy and test the effects of varying levels of anisotropy in 1-degree Community Earth System Model (CESM) simulations. Anisotropy has many effects on the simulated climate, including a reduction of temperature and salinity biases, a deepening of the southern ocean mixed-layer depth, impacts on the meridional overturning circulation and ocean energy and tracer uptake, and improved ventilation of biogeochemical tracers, particularly in oxygen minimum zones. A process-based parameterization to approximate the effects of unresolved shear dispersion is also used to set the strength and direction of anisotropy. The shear dispersion parameterization is similar to drifter observations in spatial distribution of diffusivity and high-resolution model diagnosis in the distribution of eddy flux orientation.

University -Oceanic overflows occur when dense water flows down a continental slope into less dense ambient water. The resulting density driven plumes occur naturally in various regions of the global ocean and affect the large-scale circulation. General circulation models currently rely on parameterizations for representing dense overflows due to resolution restrictions. The work presented here involves a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Laboratory experiments are conducted using a rotating square tank customized for idealized overflow and a high-resolution camera mounted on the table in the rotating reference frame for data collection. Corresponding numerical simulations are performed using the MIT general circulation model (MITgcm) run in the non-hydrostatic configuration. Resolution and numerical parameter studies are presented to ensure accuracy of the simulation. Laboratory and computational experiments are compared across a wide range of physical parameters, including Coriolis parameter, inflow density anomaly, and dense inflow volumetric flow rate. The results are analyzed using various calculated metrics, such as the plume velocity.

Anisotropic mesoscale eddy transport in ocean general circulation models SCOTT RECKINGER, BAYLOR FOX-KEMPER, Brown University, SCOTT BACHMAN, University of Cambridge, FRANK BRYAN, JOHN DENNIS, GOKHAN DANABASOGLU, National Center for Atmospheric Research -In modern climate models, the effects of oceanic mesoscale eddies are introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically. However, the diffusive processes that the parameterization approximates, such as shear dispersion and potential vorticity barriers, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters from one to three: major diffusivity, minor diffusivity, and alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces temperature and salinity biases. These effects can be improved by parameterizing the oceanic anisotropic transport mechanisms.

Response of the Equatorial Atlantic Ocean to wind forcing anomalies M. Wade (1,2), Y. duPenhoat (2), G. Caniaux (1), and H. Giordani (1) (1) Centre National de Recherches Meteorologiques (CNRM) Toulouse France, (2) Institut de Recherche pour le Développement (IRD) Toulouse France

The interannual variability of the eastern equatorial Atlantic Cold Tongue (ACT) is closely linked to rainfall variability over the western African continent and particularly to the western Africa monsoon (WAM) jump. In this study we try to relate the variability of the ACT to the variability of the WAM. For this, several indexes are defined to characterize the ACT: mean

The formation of the Atlantic cold tongue (ACT) is the dominant seasonal sea surface temperature signal in the eastern equatorial Atlantic (EEA). A comprehensive analysis of variability in its spatial extent, temperature, and onset is presented. Then, the physical mechanisms which initiate ACT onset, as well as the feedbacks from the ACT to the maritime boundary layer, and how the ACT influences the onset of the West African monsoon (WAM) are discussed. We argue that in the EEA, the air-sea coupling between the ACT and WAM occurs in two phases. From March to mid-June, the ACT results from the intensification of the southeastern trades associated with the St. Helena anticyclone. Steering of surface winds by the basin shape of the EEA imparts optimal wind stress for generating the maximum upwelling south of the equator. During the second phase (mid-June-August), wind speeds north of the equator increase as a result of the northward progression of the intensifying trades and as a result of significant surface heat flux gradients produced by the differential cooling between the ACT and the tropical waters circulating in the Gulf of Guinea (GG). It is anticipated that the atmospheric divergence induced at low levels north of the equator reduces convection over the GG and that increased northward winds shift convection over land. Correlations between the ACT and the WAM onset dates over the last 26 years measure as much as 0.8. This suggests that the ACT plays a key role in the WAM onset.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The phenomenon of 1I/'Oumuamua introduced the interstellar object (ISO) class of celestial body into the astronomical lexicon, those objects with heliocentric speeds clearly in excess of that required to parabolically escape the Solar System-and therefore of extrasolar origin. A vogue topic at this moment in time is the possibility that some ISOs may impact with Earth, where they would be observed as bolides (meteor fireballs). There is the claim for instance that a meteor listed in the NASA-JPL CNEOS (Center for Near Earth Object Studies) database, CNEOS 2014-01-08 was interstellar, and additionally four further meteors from the database with interstellar origin have been proposed. This paper postulates that the origin of yet another meteor from this catalogue, CNEOS 2017-10-09 (observed over Bolivia, South America), was interstellar, as it may have been associated with 'Oumuamua. Note there is no direct velocity data for this object available, yet its observation time corresponds to the expected arrival time of an object ejected from 'Oumuamua and intersecting Earth's orbital position.

Development of anoxia in marine basins leads to formation of hydrogen sulfide and the intermediate reduced sulfur speciesthiosulfate, sulfite, zero-valent sulfur and sulfur of polysulfides. Except for thiosulfate, the data on the other reduced species of sulfur in the Black Sea water are scarce. The thiosulfate concentration in the papers of different authors varies from 20 to 40 μM; and it can be a consequence of hydrogen sulfide oxidation during sampling and analyzing. Data and methods. The previously proposed (by I. I. Volkov and N. N. Zhabina) method for determining the sulfur reduced species (sulfite + thiosulfate, zero-valent sulfur + sulfur of polysulfides) in the anaerobic basins' water has been re-evaluated and developed. Addition of suspension Zn 2 (OH) 2 CO 3 to a seawater sample destructs polysulfides and transfers the elemental sulfur to precipitation. The elemental sulfur, sulfur polysulfides and sulfides are separated from the sum of thiosulfate and sulfite by filtration. To analyze the reduced species of sulfur, we applied their reduction to hydrogen sulfide which is determined spectrophotometrically after its distillation in the argon stream and precipitation as ZnS. Results. The results of determining the sulfur species were tested by analyzing 2% solutions of NaCl with the introduced contents of thiosulfate (0.5-1.5 μmol), sulfite (< 1 μmol), elemental sulfur (< 1 μmol) against the background of much higher concentrations of hydrogen sulfide (60 µmol). Such ratios of concentrations of the sulfur reduced species and hydrogen sulfide are found in the Black Sea water. Discussion and conclusion. It is shown that the proposed method correctly reflects presence of the reduced species of sulfur in the solutions. To analyze the sulfur species, the Niskin bottles are necessarily filled with the inert gas and the samples are filtered in the inert atmosphere. The method for determining the sulfur reduced species is highly sensitive. The detection limit for ( -2 3 2 O S + -2 3 SO ) is 0.03 μM, for (S 0 + S 0 polysulfide) is 0.02 μM and for sulfide sulfur -0.01 μM.

The main task of the Center for Subsurface Sensing and Imaging Systems (CenSSIS), funded by the National Science Foundation, is to develop appropriate techniques to separate complex subsurface signals. This multi-university Engineering Research Center aims to revolutionize the existing technology for detecting and imaging objects under different layers, including underwater. The University of Puerto Rico at Mayaguez (UPRM), a main partner of CenSSIS, has created SeaBED for the development of improved remote sensing techniques for monitoring coral reefs. SeaBED includes both controlled laboratory facilities and a field test environment in the southwest coast of Puerto Rico that is being used to validate sensors, improve algorithms, understand physical models, and develop extraction tools and classification methods for underwater sensing. Multiple sensors with different spatial and spectral resolutions, such as Landsat TM, IKONOS, Hyperion, and AVIRIS, have been tested. In terms of image processing, different pattern recognition algorithms (e.g., image classification and spectral unmixing) and time series analyses for change detection have been used. Bottom reflectance and remote sensing reflectance have been measured from several coral reef zones, different species, and coral health conditions with a submersible spectroradiometer. Furthermore, for optical imaging of coral reefs present below one attenuation depth (approximately 20 m in oligotrophic waters), which defines a practical limit for effective airborne and satellite remote sensing, we have used an autonomous underwater vehicle (AUV) as an in situ platform for acquiring measurements. High-resolution optical imaging from the AUV is used for mapping and characterizing deeper reefs present between 30 to 100 meters.

Berdasarkan definisi dari International Hydrographic Organization (IHO, 2005), Lowest Astronomical Tide (LAT) secara Internasional digunakan sebagai Chart Datum, yaitu acuan tinggi permukaan air yang digunakan untuk survei  Hidro-Oseanografi. LAT ini ditentukan dengan prediksi pasut selama 18.61 tahun.  Dalam penelitian ini akan ditentukan bagaimana nilai LAT jika diprediksi dengan data pengamatan pasut kurang dari satu tahun. Dalam penentuan LAT, dilakukan analisis konstanta pasut dan prediksi. Analisis konstanta pasut  dihitung dengan menggunakan metode Least Square (kuadrat terkecil) mulai data pengamatan  pasut satu bulan, dua bulan, tiga bulan, empat bulan, enam bulan sampai dengan data pasut 12 bulan, kemudian dari hasil analisis konstanta pasut tersebut diprediksi pasut selama 18.61 tahun. Hasil prediksi tersebut akan diperoleh perbedaan nilai LAT data pasut  kurang dari satu tahun dengan data pasut selama satu tahun. Selanjutnya dari perbedaan nilai LAT tersebut  dilakukan a...

This paper discusses a mathematical model for the dynamics of pollution in the Arctic basin, considering spatial non-uniformities in the distribution of ecological and hydrodynamic parameters. The model features blocks simulating contaminant fluxes through the tropic chains. The results of numerical experiments are provided which demonstrate the model's capability to predict and assess the dynamics of heavy metals, radionuclides, and petroleum hydrocarbons in the Arctic basin. The model is adaptable to a global model. Climatic phenomena and anthropogenic forcing are described in the form of scenarios.

Two different types of numerical ocean circulation models are used in a classical idealized problem, the thermally induced circulation in an ocean basin bounded by two meridians to the east and west and by the equator and a line of constant latitude. A simple scaling theory exists for predicting poleward heat transport and the strength of meridional overturning as a function of vertical diffusivity and other external factors. However, previous studies have indicated conflicting results, and other scaling laws have been proposed. Experiments with two widely used types of numerical models, one based on depth coordinates and the other based on isopycnal layers, provide insight into the discrepancies of previous studies. In the numerical experiments vertical diffusivity is varied over a range of 200. The source of the difficulty in previous studies is in part traced to applying a fixed restoring coefficient at the upper boundary and considering the buoyancy forcing at the surface fixed irrespective of vertical diffusivity . Globally or zonally averaged results show a robust agreement between the two models and support the simple scaling law in a flat-bottom basin and a bowl-shaped basin, as long as the meridional circulation is estimated along isopycnal surfaces and in situ rather than externally imposed restoring density differences are used to estimate the geostrophic-scale velocity. Over the thermocline the vertical mean of the zonally averaged zonal baroclinic pressure gradient has constant ratio to the vertical mean of the zonally averaged meridional baroclinic pressure gradient, consistent with the scaling assumptions for a diffusive thermocline.

The expansion of the Popoh PPI in Popoh Village, Tulungagung, East Java affects the movement of currents and waves in the vicinity. The purpose of this study was to analysis sediments and the pattern of coastline changes and to elaborate these using wave modelling based around the expansion of the Fish Landing Port Popoh. The methods used in this research were sieve analysis, remote sensing and GIS for processing Sentinel-2 imagery, and hydrodynamic modeling using DHI MIKE 21. Sediment sampling was carried out based on a purposive sampling method, with 10 points spread over land and water using a sediment grab. The findings of the study showed that there was a fairly large accretion from 2015 to 2021, with sand and clay sediment types. The accretion process dominated the abrasion process at Popoh Beach. In the period 2015 to 2018, the area of accretion was 17.78 hectares and, in the period 2018 to 2021, the area of accretion was 9.32 hectares, so that for 6 years there was an accretion of 18.79 hectares. The average wave energy was 1.5 kW/m per year on eroded beaches with sandy sediments.

The coastal region is characterized by dynamic changes in its coastline, which can be attributed to various factors. However, the main causes of change along the Gresik coast have yet to be thoroughly studied. Therefore, this research aims to examine the patterns of coastline change along the Gresik coast around the Madura Strait and the influence of wind-generated waves on them. Specifically, the study focuses on four coastal zones: Ujung Pangkah, Sidayu, Bungah, and Manyar districts. The research utilizes satellite imagery and geographic information systems (GIS) as well as methods for calculating ocean waves to analyze the coastline change patterns. The study also examines the impact of ocean wave energy on coastal abrasion and accretion. The findings revealed that the accretion rate in the study area was higher than the erosion rate. The accretion in the coastal area of Gresik is attributed to the flow of the Bengawan Solo River, which carries sediment from upstream. The accretion and abrasion areas for the entire period from 2002 to 2019 were 1063.16 ha and 425.23 ha, respectively. The study also found that the mangrove areas exhibit a higher rate of accretion than abrasion, indicating their potential as a reliable indicator of the effects of sea level rise resulting from global warming. This study revealed that the northern part of Ujung Pangkah District and Bungah District experienced the highest abrasion patterns, whereas no abrasion was observed in Sidayu District. Between 2002 and 2019, the abrasion areas in Ujung Pangkah and Bungah districts totaled 243.96 ha and 178.29 ha, respectively. Windgenerated waves were likely the primary cause of the abrasion in these areas, though other factors may also have contributed to coastline changes. It is essential to consider these factors for effective coastal management in the region.

A new method for indirect calculation of the surface meridional velocity is presented. On the base of the known latitude function of the pressure an expression is found for the calculation of the mean meridional component of velocity in the winter season, including surface friction. Together with known values of the meridional wind in the higher levels the mean mass transport at the Northern Hemisphere in the planetary boundary layer is calculated. The computation shows that the mean meridional mass transport in the planetary boundary layer is southward and that it is greater than 2/3 of the total southward mass transport in the entire atmosphere. The mean vertical velocity is calculated from the continuity of the mass of air in the planetary boundary layer. The difference between measured and calculated meridional wind profile in the Ekman layer shows greater values in the lower latitudes than at higher ones. Ober die mittlere meridionale Zirkulation in der planetaren Grundschicht im Winter in der Nordhemisphiire Es wird eine neue Methode zur indirekten Berechnung der meridionalen Oberfl~ichengeschwindigkeit dargelegt. Auf Grund der bekannten Breitenabh~ingigkeit des Druckes wird eine Gleichung zur Berechnung der mittleren meridionalen Komponente der Geschwindigkeit im Winter mit Bemcksichtigung der Bodenreibung abgeleitet. Mit Beriicksichtigung der bekannten Werte des Windes in h6heren Schichten wird der mittlere Massentransport in der planetaren Grundschicht der Nordhemisph~re berechnet. Die Berechnung ergibt, dai~ dieser Massentransport gegen Stiden gerichtet ist und daf~ er gr6i~er ist als 2/3 des gesamten Massentransports nach Siiden in der ganzen Atmosph~ire. Die mitflere vertikale Geschwindigkeit wird aus der Kontinuit~t der Luftmasse in der planetaren Gmndschicht berechnet. Die Differenz zwischen gemessenem und berechnetem meridionalen Windproffl in der Ekman-Schicht weist in niedrigeren Breiten gr6t~ere Werte auf als in h6heren Breiten.

The importance of correcting for the thermal-lag effect in Sea-Bird CTD data is established for the strongly stratified waters of the Mediterranean thermocline in summer. Data collected with a SBE-25 CTD during an in situ experiment in the Balearic Sea in early summer are analysed. From the comparison between down and upcasts data, a large thermal-lag effect that contaminates the salinity data by errors up to 0.1 psu is diagnosed. A standard correction procedure is applied and results are discussed.

Arabia with the collaboration of International Union for Conservation of Nature and Natural Resources (IUCN) as an environmentally sensitive area. This study is considered to be a baseline study for Ras Hatiba Lagoon. The lagoon is located at the eastern coast of the Red Sea. It is shallow with an average depth of 2m. Tidal force is dominating the water circulation in the lagoon.

Water column conditions in a lagoon near Jeddah are investigated on the basis of changes in potential energy. Three major factors including balance of surface heat at the air-sea interface, wind and tidal mixing are considered. A negative potential energy change dv dt will develop stratification, whereas positive dv dt will tend to mix the water column. The tidal effect is greater in summer with wind mixing showing no great variations. The buoyancy effect of the heat balance at the surface is negative from April to October. This negative buoyancy effect will tend to develop stratification but the positive contributions of wind and tide counteract this and the water column remains mixed except in September and October, when a weak stratification may develop. Generally, the water column remains practically mixed throughout the year. The change in heat content of the water column from mid-April to mid-September is about 3.3 × 10 8 J. During this period the net heat input at the air interface is about 2.0 × 10 8 J, which is about 40% less than the

The semi-enclosed nature of the Red Sea can be used as a test volume in an attempt to assess the accuracy of climatological airsea interface fluxes, if the advective heat transport at Bab-el-Mandab is accurately known. However, there are few estimates of the advective heat to the Red Sea and even they differ significantly. A review of these estimates is made. It is shown that based on an evaporation rate of 2m.a -1 , and the monthly mean volume transports and average temperatures for the two/three layers near the sill, as shown from the previous studies, the annual average advective heat transport to the Red Sea is about 17W.m -2 .

The exchange of water between coastal inlets and the inner continental shelf is mainly due to astronomical, meteorological and thermohaline forces. The relative importance of these factors depends on local tides and characteristic wind speeds. Sharm Obhur is a shallow and narrow coastal inlet about 10 km long. The maximum depth at the entrance is about 35 m. It has marinas, hotels, and other tourist attractions along its periphery. The study of water exchange is of significant importance because of sewage coming from the hotels and marinas. Temperature and salinity vertical distribution showed that during winter at most of the stations the water column is well mixed and stratified during summer season. The study shows that the flushing time of Sharm Obhur is about 12 days. This time scale should be taken into account for any future constructions in Sharm Obhur to ensure the water quality.

The Unified Equation for ocean waves represents a groundbreaking theoretical framework that integrates the complex domains of gravitational, electromagnetic, and quantum mechanics. This sophisticated equation can potentially transform various industries, including energy production, aerospace innovation, defence strategies, medical science applications, and time synchronisation methods. The primary goal of developing a Unified Equation for ocean waves is to unify these fundamental physical forces into a singular, cohesive model. Should this ambitious equation be successfully formulated, its implications could lead to revolutionary advancements in energy generation technologies, pioneering methods for space travel, and the creation of advanced materials with unprecedented properties. This document details significant advancements in the optimisation of quantum field interactions and enhancements in energy conversion rates within the extensive framework of the Unified Ocean Wave Equation. Additionally, it examines the theoretical foundations and practical engineering aspects involved in developing advanced propulsion systems, with a specific focus on Gravity-Assisted Plasma Thrusters and Photonic and Quantum Vacuum Propulsion systems. This analysis encompasses the relevant physics equations, material selections, and spacecraft design considerations necessary for these cutting-edge technologies. A pivotal concept presented in this document is the innovative treatment of time as a spatial coordinate system. Within this framework, the present is represented by the coordinate x, the past by y, and the future by z. Under conditions approaching the speed of light, the distinctions between these temporal states may converge, opening up the possibility for groundbreaking new forms of propulsion and interstellar travel. The study not only derives a novel wave equation but also examines its profound implications for spacecraft design, including an assessment of potential travel speeds that could redefine our understanding of space exploration. Furthermore, the document thoroughly examines the theoretical foundations and engineering principles underpinning advanced propulsion methods, including Gravity-Assisted Plasma Thrusters and Photonic and Quantum Vacuum Propulsion systems. These innovative propulsion mechanisms utilise the principles of gravity waves, quantum fluctuations, and photonic interactions to enable travel at speeds approaching the speed of light. A spacecraft capable of achieving such astonishing velocities must harmoniously integrate principles from general relativity, quantum mechanics, and fluid dynamics. The proposed engine design is a sophisticated system that leverages the unified physics equation to manipulate spacetime effectively, propelling the vehicle through an intricate combination of exotic matter, advanced electromagnetic propulsion techniques, and cutting-edge relativistic fluid mechanics. The long-sought goal of unifying electromagnetism, gravity, quantum mechanics, and fluid dynamics within a coherent theoretical framework stands to enhance our capability for space travel significantly. Travelling at relativistic velocities introduces multiple biological challenges that must be addressed: Time Dilation, Radiation Exposure, Tissue Compression, and DNA damage mitigation.

Low-frequency currents and eddies transport sediment, pathogens, larvae, and heat along the coast and between the shoreline and deeper water. Here, low-frequency currents (between 0.1 and 4.0 mHz) observed in shallow surfzone waters for 120 days during a wide range of wave conditions are compared with theories for generation by instabilities of alongshore currents, by ocean-wave-induced sea surface modulations, and by a nonlinear transfer of energy from breaking waves to low-frequency motions via a two-dimensional inverse energy cascade. For these data, the low-frequency currents are not strongly correlated with shear of the alongshore current, with the strength of the alongshore current, or with wave-group statistics. In contrast, on many occasions, the low-frequency currents are consistent with an inverse energy cascade from breaking waves. The energy of the low-frequency surfzone currents increases with the directional spread of the wave field, consistent with vorticity injection by short-crested breaking waves, and structure functions increase with spatial lags, consistent with a cascade of energy from few-meter-scale vortices to larger-scale motions. These results include the first field evidence for the inverse energy cascade in the surfzone and suggest that breaking waves and nonlinear energy transfers should be considered when estimating nearshore transport processes across and along the coast.

We discuss the expuirncntaI methodology and presuit the resula of several ucperimuirs on h e onset and growth of instabilities in stratified shear flow. Our results include the assessment of the effcctive diffusivity prior to the development of the Kelvin-Heimhola (K-H) type instability and the measurement of the velocity fieid. This allows us to detennine that the onset of the instability takes place when the Richardson numbcr is close to 0.25, this value slightly decrcasing with increasinj initial interface thickness. Ttie formation of a fine layered structurc at &e interface is suggesttd by dcnsity profiles takcn immediately aftcr the generation of K-H biilows, but the size of the full inteñace as well as the layers thcmscives decrease in the following few seconds. We hypothesize rhat the time scale of the K-H billows in our laboratory experiments is so short that there is no time for addad Nxing to furrher dimibute and smoothen the initiai layer smcturc.

An analytic solution is presented for thc stcady-state dcpth-averaged western boundary current fiowing ovcr the continental slope by combining thrce higlily ideali~cd niodels: the Stonimel rnodel. <he Munk rnodel. and thc arresied ropographic wave modei. The main vonicity balance over the slope is between planetary vorlicity advection and the slope-induced bottom stress torque, which is proponional to rv(h-'), where r is the Rayleigh friction coefficient, h is the water depth, and v is the meridional velocity. This slope-induced torque provides the necessary source of vonicity for poleward fiow over the slope, its simple interpretation being that vorticity is produced because the bottom stress has to act over the seaward-deepening water column. The character of thc solution deperids on the slo e a as well as on the assumed bottom drag coefficient, and the length scale of the boundary current is -4. It is funher shown thnt, if the depth-averaged vclociiy Aows along isobaths. then the stretching of water columns associated with cross-isobath geostrophic ftow, which conipensates bottom Eknian transport, is identical ro [he slope-induced torque by the geosrrophic velocities.

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Small-scale turbulent mixing drives the upwelling of deep water masses in the abyssal ocean as part of the global overturning circulation 1 . However, the processes leading to mixing and the pathways through which this upwelling occurs remain insufficiently understood. Recent observational and theoretical work 2-5 has suggested that deep-water upwelling may occur along the ocean's sloping seafloor; however, evidence has, so far, been indirect. Here we show vigorous near-bottom upwelling across isopycnals at a rate of the order of 100 metres per day, coupled with adiabatic exchange of near-boundary and interior fluid. These observations were made using a dye released close to the seafloor within a sloping submarine canyon, and they provide direct evidence of strong, bottom-focused diapycnal upwelling in the deep ocean. This supports previous suggestions that mixing at topographic features, such as canyons, leads to globally significant upwelling 3,6-8 . The upwelling rates observed were approximately 10,000 times higher than the global average value required for approximately 30 × 10 6 m 3 s -1 of net upwelling globally 9 .

The global circulation driven solely by relaxation to an idealized surface temperature profile and to interior mixing is examined. Forcing by winds and evaporation/precipitation is excluded. The resulting circulation resembles the observed in many ways, and the overturning is of similar magnitude. The overturning is driven by large-scale upwelling in the interior (which is relatively large, because of the use of a constant mixing coefficient). The compensating downwelling occurs in the northern North Atlantic and in the Ross and Weddell Seas, with an additional, smaller contribution from the northern North Pacific. The latter is weaker because the Bering Strait limits the northward extent of the flow. The downwelling occurs in frictional layers near the boundaries and depends on the lateral shear in the horizontal flow. The shear, in turn, is linked to the imposed surface temperature gradient via thermal wind, and as such, the downwelling can be reduced or eliminated in selected reg...