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We perform an out-of-distribution analysis of ~12,000,000 semi-independent 128x128 pixel^2 SST regions, which we define as cutouts, from all nighttime granules in the MODIS R2019 Level-2 public dataset to discover the most complex or extreme phenomena at the ocean surface. Our algorithm (Ulmo) is a probabilistic autoencoder, which combines two deep learning modules: (1) an autoencoder, trained on ~150,000 random cutouts from 2010, to represent any input cutout with a 512-dimensional latent vector akin to a (non-linear) EOF analysis; and (2) a normalizing flow, which maps the autoencoder's latent space distribution onto an isotropic Gaussian manifold. From the latter, we calculate a log-likelihood value for each cutout and define outlier cutouts to be those in the lowest 0.1% of the distribution. These exhibit large gradients and patterns characteristic of a highly dynamic ocean surface, and many are located within larger complexes whose unique dynamics warrant future analysis. Without guidance, Ulmo consistently locates the outliers where the major western boundary currents separate from the continental margin. Buoyed by these results, we begin the process of exploring the fundamental patterns learned by Ulmo, identifying several compelling examples. Future work may find that algorithms like Ulmo hold significant potential/promise to learn and derive other, not-yet-identified behaviors in the ocean from the many archives of satellite-derived SST fields. As important, we see no impediment to applying them to other large, remote-sensing datasets for ocean science (e.g., sea surface height, ocean color)., Comment: 16 pages, 12 figures

The Regional Ocean Modeling System (ROMS), including an ice shelf component, has been applied on a circum-Antarctic domain to derive estimates of ice shelf basal melting. Significant improvements made compared to previous models of this scale are the inclusion of tides and a horizontal spatial resolution of 2 km, which is sufficient to resolve on-shelf heat transport by bathymetric troughs and eddy-scale circulation. We run the model with ocean–atmosphere–sea ice conditions from the year 2007 to represent nominal present-day climate. We force the ocean surface with buoyancy fluxes derived from sea ice concentration observations and wind stress from ERA-Interim atmospheric reanalysis. Boundary conditions are derived from the ECCO2 ocean state estimate; tides are incorporated as sea surface height and barotropic currents at the open boundary. We evaluate model results using satellite-derived estimates of ice shelf melting and established compilations of ocean hydrography. The Whole Antarctic Ocean Model (WAOM v1.0) qualitatively captures the broad scale difference between warm and cold regimes as well as many of the known characteristics of regional ice–ocean interaction. We identify a cold bias for some warm-water ice shelves and a lack of high-salinity shelf water (HSSW) formation. We conclude that further calibration and development of our approach are justified. At its current state, the model is ideal for addressing specific, process-oriented questions, e.g. related to tide-driven ice shelf melting at large scales.

Ice algae play a fundamental role in shaping polar marine ecosystems and biogeochemistry. This role can be investigated by field observations, however the influence of ice algae at the regional and global scales remains unclear due to limited spatial and temporal coverage of observations, and because ice algae are typically not included in current Earth System Models. To address this knowledge gap, we introduce a new model intercomparison project (MIP), referred to here as the Ice Algae Model Intercomparison Project phase 2 (IAMIP2). IAMIP2 is built upon the experience from its previous phase, and expands its scope to global coverage (both Arctic and Antarctic) and centennial timescales (spanning the mid-twentieth century to the end of the twenty-first century). Participating models are three-dimensional regional and global coupled sea ice–ocean models that incorporate sea-ice ecosystem components. These models are driven by the same initial conditions and atmospheric forcing datasets by incorporating and expanding the protocols of the Ocean Model Intercomparison Project, an endorsed MIP of the Coupled Model Intercomparison Project phase 6 (CMIP6). Doing so provides more robust estimates of model bias and uncertainty, and consequently advances the science of polar marine ecosystems and biogeochemistry. A diagnostic protocol is designed to enhance the reusability of the model data products of IAMIP2. Lastly, the limitations and strengths of IAMIP2 are discussed in the context of prospective research outcomes.

The international Thermodynamic Equation of Seawater 2010 (TEOS-10) defined the enthalpy and entropy of seawater, thus enabling the global ocean heat content to be calculated as the volume integral of the product of in situ density, ρ, and potential enthalpy, h0 (with reference sea pressure of 0 dbar). In terms of Conservative Temperature, Θ, ocean heat content is the volume integral of ρcp0Θ, where cp0 is a constant “isobaric heat capacity”. However, many ocean models in the Coupled Model Intercomparison Project Phase 6 (CMIP6) as well as all models that contributed to earlier phases, such as CMIP5, CMIP3, CMIP2, and CMIP1, used EOS-80 (Equation of State – 1980) rather than the updated TEOS-10, so the question arises of how the salinity and temperature variables in these models should be physically interpreted, with a particular focus on comparison to TEOS-10-compliant observations. In this article we address how heat content, surface heat fluxes, and the meridional heat transport are best calculated using output from these models and how these quantities should be compared with those calculated from corresponding observations. We conclude that even though a model uses the EOS-80, which expects potential temperature as its input temperature, the most appropriate interpretation of the model's temperature variable is actually Conservative Temperature. This perhaps unexpected interpretation is needed to ensure that the air–sea heat flux that leaves and arrives in atmosphere and sea ice models is the same as that which arrives in and leaves the ocean model. We also show that the salinity variable carried by present TEOS-10-based models is Preformed Salinity, while the salinity variable of EOS-80-based models is also proportional to Preformed Salinity. These interpretations of the salinity and temperature variables in ocean models are an update on the comprehensive Griffies et al. (2016) paper that discusses the interpretation of many aspects of coupled Earth system models.

Assessing the risk of tsunami-driven debris has increasingly been recognized as an important design consideration. The recent ASCE/SEI7-16 standard Chapter 6 requires all the areas included within a 22.5° spreading angle from the debris source to consider the debris impact. However, it would be more reasonable to estimate the risks using numerical simulation models. Although a number of simulation models to predict tsunami debris transport have been proposed individually, comparative studies for these simulation models have rarely been conducted. Thus, in the present study, an inter-model comparison for tsunami debris simulation model was performed as a part of the virtual Tsunami Hackathon held in Japan from September 1 to 3 in 2020. The blind benchmarking experiment, which recorded the transport of three container models under a tsunami-like bore, was conducted to generate a unique dataset. Then, four different numerical models were applied to reproduce the experiments. Simulated results demonstrated considerable differences among the simulation models. Essentially, the importance of accurate modelling of a flow field, especially a tsunami front, was confirmed to be important in simulating debris motion. Parametric studies performed in each model and comparisons between different models also confirmed that a drag coefficient and inertia coefficient would influence the simulated debris trajectory and velocity. It was also shown that two-way coupled modelling to express the interaction between debris and a tsunami is important to accurately model the debris motion.

In this study, the Adriatic Sea and Coast (AdriSC) kilometre-scale atmosphere–ocean climate model covering the Adriatic Sea and northern Ionian Sea is presented. The AdriSC ocean results of a 31-year-long (i.e. 1987–2017) climate simulation, derived with the Regional Ocean Modeling System (ROMS) 3 km and 1 km models, are evaluated with respect to a comprehensive collection of remote sensing and in situ observational data. In general, it is found that the AdriSC model is capable of reproducing the observed sea surface properties, daily temperatures and salinities, and the hourly ocean currents with good accuracy. In particular, the AdriSC ROMS 3 km model demonstrates skill in reproducing the main variabilities of the sea surface height and the sea surface temperature, despite a persistent negative bias within the Adriatic Sea. Furthermore, the AdriSC ROMS 1 km model is found to be more capable of reproducing the observed thermohaline and dynamical properties than the AdriSC ROMS 3 km model. For the temperature and salinity, better results are obtained in the deeper parts than in the shallow shelf and coastal parts, particularly for the surface layer of the Adriatic Sea. The AdriSC ROMS 1 km model is also found to perform well in reproducing the seasonal thermohaline properties of the water masses over the entire Adriatic–Ionian domain. The evaluation of the modelled ocean currents revealed better results at locations along the eastern coast and especially the northeastern shelf than in the middle eastern coastal area and the deepest part of the Adriatic Sea. Finally, the AdriSC climate component is found to be a more suitable modelling framework to study the dense water formation and long-term thermohaline circulation of the Adriatic–Ionian basin than the available Mediterranean regional climate models.

The Kitikmeot Sea is a semi-enclosed, east–west waterway in the southern Canadian Arctic Archipelago (CAA). In the present work, the ice conditions, stratification, and circulation of the Kitikmeot...

– Introducing a new method for mapping submerged archaeological landscapes. – Airborne hyperspectral data allows estimation of bottom depth and reflectance for archaeological surveys in shallow waters.

The paper reports a numerical investigation into the effect of rubble mounds inside perforated caisson breakwaters (PCBs), in which a line-shaped mass source wavemaker is proposed for generating random waves. A series of experiments are employed to validate the numerical model, and good agreements are observed in the comparison of the experimental and numerical results. With the use of the validated numerical model, the numerical investigation is performed, in which the attention is mainly paid to two parameters: the slope angle and porosity of the inner rubble mound. The result shows that, as the slope angle of the inner rubble mound increases, the reflection coefficient is observed to decrease first and then increase, and compared to the experiment, both the positive and negative hydrodynamic pressure acting on the solid rear wall of PCBs is weakened. On the other hand, although a larger inner rubble mound porosity is beneficial to diminish the reflection coefficient, the reduction is not obvious especially when the front wall porosity is small. Furthermore, as the increase of front wall porosity and relative wave absorption chamber length (the ratio of wave absorption chamber length to significant wavelength), the effect of the slope angle and porosity of the inner rubble mound becomes more significant because more waves could enter the wave absorption chamber. The relative wave absorption chamber length considered in the present study ranges from 0.06 to 0.21, and the recommended slope angle is approximately 45 degrees.

In this paper, a numerical study is presented to investigate wave force on the connections of main parts of a side-anchored straight floating bridge concept for the Bjørnafjorden fjord crossing. The floating bridge is supported by 18 pontoons, and three groups of mooring lines are employed to restrain the bridge against horizontal loads and increase its transverse stiffness. The created wave forces at the connections of pontoon-column and column-girder of the floating bridge considering the effects of short-crested and long-crested waves, varying wave direction, hydrodynamic interaction between pontoons, and mooring system are analyzed. It is found that short-crested and long-crested waves depending on their direction decrease or increase the wave forces on the joints. Considering that the effect of hydrodynamic interaction between pontoons can increase or reduce the wave forces and moments created in the joints, which means the neglect of the hydrodynamic interaction effects between the pontoons to simplify the modeling of this type of floating bridge, may be unacceptable. Moreover, the results showed that the bridge mooring system does not merely reduce the wave forces and moments at joints along the bridge.

The North River estuary (Massachusetts, USA) is a tidal marsh creek network where tidal dispersion processes dominate the salt balance. A field study using moorings, shipboard measurements, and drone surveys was conducted to characterize and quantify tidal trapping due to tributary creeks. During flood tide, saltwater propagates up the main channel and gets “trapped” in the creeks. The creeks inherit an axial salinity gradient from the time-varying salinity at their boundary with the main channel, but it is stronger than the salinity gradient of the main channel because of relatively weaker currents. The stronger salinity gradient drives a baroclinic circulation that stratifies the creeks, while the main channel remains well-mixed. Because of the creeks’ shorter geometries, tidal currents in the creeks lead those in the main channel; therefore, the creeks never fill with the saltiest water which passes the main channel junction. This velocity phase difference is enhanced by the exchange flow in the creeks, which fast-tracks the fresher surface layer in the creeks back to the main channel. Through ebb tide, the relatively fresh creek outflows introduce a negative salinity anomaly into the main channel, where it is advected downstream by the tide. Using high-resolution measurements, we empirically determine the salinity anomaly in the main channel resulting from its exchange with the creeks to calculate a dispersion rate due to trapping. Our dispersion rate is larger than theoretical estimates that neglect the exchange flow in the creeks. Trapping contributes more than half the landward salt flux in this region.

A recently developed energy flux diagnosis scheme, which incorporates a smooth connection between the tropical and subtropical zones, is used in the present study to investigate vertically propagating waves in the tropical Indian Ocean (IO) based on the result of a linear, continuously stratified ocean model driven by climatological wind forcing. This extended diagnosis reveals deep-reaching eastward energy fluxes at the equator which develop four times per year and are associated with equatorial Kelvin waves (KWs) generated by semiannual winds. The authors find that the downward transfer of wave energy is particularly deep in the southern Bay of Bengal (SBoB). This downward flux is attributed to off-equatorial Rossby waves and appears four times per year, maximizing its amplitude during November–December. Southwesterly winds in the Arabian Sea intensify eastward energy flux of KWs at mid-depth, which maximizes in amplitude in August. This is contrastive to KW energy flux at the surface which peaks in May. These mid-depth equatorial KW packets subsequently arrive at the eastern boundary of the IO and are diffracted poleward to produce downward energy flux in November and December detected in the SBoB.

A long simulation over the period 1901–2010 with an eddy-permitting ocean circulation model is used to study the variability of the upper layer circulation in the North Ionian Gyre (NIG) in the Eastern Mediterranean Sea (EMed). The model is driven by the atmospheric forcing from the twentieth century reanalysis data set ERA-20C, ensuring a consistent performance of the model over the entire simulation period. The main modes of variability known in the EMed, in particular the decadal reversals of the NIG upper layer circulation observed since the late 1980s are well reproduced. We find that the simulated NIG upper layer circulation prior to the observational period is characterized by long-lasting cyclonic phases with weak variability during years 1910–1940 and 1960–1985, while in the in-between period (1940–1960) quasi-decadal NIG circulation reversals occur with similar characteristics to those observed in the recent decades. Our simulation indicates that the NIG upper layer circulation is rather prone to the cyclonic mode with occasional kicks to the anticyclonic mode. The coherent variability of the NIG upper layer circulation mode and of the Adriatic Deep Water (AdDW) outflow implies that atmospheric forcing triggering strong AdDW formation is required to kick the NIG into an anticyclonic circulation 1–2 years later. A sensitivity experiment mimicking a cold winter event over the Adriatic Sea supports this hypothesis. Our simulation shows that it is the multi-decadal variability of the salinity in the Adriatic Sea that leads to periods where low salinity prevents strong AdDW formation events. This explains the absence of quasi-decadal NIG reversals during 1910–1940 and 1960–1985.

In August 2018, a remarkable polynya was observed off the north coast of Greenland, a perennial ice zone where thick sea ice cover persists. In order to investigate the formation process of this polynya, satellite observations, a coupled ice-ocean model, ocean profiling data, and atmosphere reanalysis data were applied. We found that the thinnest sea ice cover in August since 1978 (mean value of 1.1 m, compared to the average value of 2.8 m during 1978−2017) and the modest southerly wind caused by a positive North Atlantic Oscillation (mean value of 0.82, compared to the climatological value of −0.02) were responsible for the formation and maintenance of this polynya. The opening mechanism of this polynya differs from the one formed in February 2018 in the same area caused by persistent anomalously high wind. Sea ice drift patterns have become more responsive to the atmospheric forcing due to thinning of sea ice cover in this region.

Tropical Storm Eta impacted the coast of west-central Florida from 11 November to 12 November 2020 and generated high waves over elevated water levels for over 20 hours. A total of 148 beach and nearshore profiles, spaced about 300 m (984 ft) apart, were surveyed one to two weeks before and one to eight days after the storm to examine the beach changes along four barrier islands, including Sand Key, Treasure Island, Long Key, and Mullet Key. The high storm waves superimposed on elevated water level reached the toe of dunes or seawalls and caused dune erosion and overwash at various places. Throughout most of the coast, the dune, dry beach, and nearshore area was eroded and most of the sediment was deposited on the seaward slope of the nearshore bar, resulting in a roughly conserved sand volume above closure depth. The longshore variation of beach-profile volume loss demonstrates an overall southward decreasing trend, mainly due to a southward decreasing nearshore wave height as controlled by offshore bathymetry and shoreline configurations. The Storm Erosion Index (SEI) developed by Miller and Livermont (2008) captured the longshore variation of beach-profile volume loss reasonably well. The longshore variation of breaking wave height is the dominant factor controlling the longshore changes of SEI and beach erosion. Temporal variation of water level also played a significant role, while beach berm elevation was a minor factor. Although wider beaches tended to experience more volume loss from TS Eta due to the availability of sediment, they were effective in protecting the back beach and dune area from erosion. On the other hand, smaller profile-volume loss from narrow beach did not necessarily relate to less dune/ structure damage. The opposite is often true. Accurate evaluation of a storm’s severity in terms of erosion potential would benefit beach management especially under the circumstance of increasing storm activities due to climate change.

Hurricane Isaias struck the Cape Fear Region of North Carolina around 23:00 EDT on 3 August 2020, making landfall at Ocean Isle Beach as a Category 1 storm with peak wind speeds of 80 mph. An array of nearshore Sofar Spotter wave buoys captured the wave field at two beaches off the coasts of Bald Head Island (south-facing and east-facing beaches) and Masonboro Island. Local variations in significant wave height and peak wave direction were observed along the Lower Cape Fear Region, due to large shoal features impacting the regional wave climate. A cross-shore transect of five pressure sensors was installed at the north end of Masonboro Island 2.5 days prior to landfall to measure storm surge, wave runup, and variation of gravity/ infragravity wave energy across the barrier island. The three fast-sampling wave gauges along the backshore became buried before Hurricane Isaias peak storm surge, and the two gauges on and behind the dune were never inundated. A low-cost (< $250) Storm Surge Observation Camera (SSOC) prototype captured storm surge and coastal erosion at Kure Beach, in conjunction with pre- and post-storm RTK GPS beach profile surveys. Kure Beach experienced more than 1.0 m of vertical erosion of the berm, while Masonboro Island experienced around 0.1 m of accretion across the backshore, despite nearly identical wave and wind forcing conditions at the two beaches separated by ~20 km. Pre-storm berm height and width (higher and wider at Kure Beach), as well as foreshore slope (steeper, 1:9, at Kure Beach), are likely factors influencing significant erosion at Kure Beach, while slight accretion was observed at Masonboro Island.

Since August 2017, the Kuroshio has taken a large-meander (LM) path, which has forced the Kuroshio extension (KE) to be in its stable state against its wind-forced decadal variability. How such current conditions have impacted the formation and advection of North Pacific subtropical mode water (STMW) over its distribution region was examined using Argo float data during 2005–2020. Out of the whole STMW defined as a low-potential vorticity layer of 16–19.5 ºC, a relatively cold variety of 16–18 ºC, which was formed south of the KE and advected westward and southward, occupied more than 80% of the total volume. The formation rate of the 16–18 ºC variety was low during 2006–2009 in an unstable-KE period and high during 2010–2015 in a stable-KE period, and then dropped drastically in 2016 despite the KE still being in the stable state. After a short unstable-KE period in 2016–2017, the LM-forced, stable-KE period began, but the formation rate of the 16–18 ºC variety has not restored, possibly due to stronger background stratification propagated from the central North Pacific. In addition, the 16–18 ºC variety has had to make a southern detour around the LM, and its westward advection from the formation region south of the KE to the region south of Japan has been significantly decreased, possibly because it is dissipated more strongly over a southern part of the Izu–Ogasawara Ridge. Due to such decline in the formation and advection, the volume of the 16–18 ºC variety and hence that of the whole STMW have gradually decreased since 2016.

Five high-resolution hydrographic sections were conducted at the periphery of an anticyclonic mesoscale eddy north of the Kuroshio Extension (KE) to explore the evolution of submesoscale structure in the subsurface layer associated with mesoscale eddies. The five sections continuously captured patches of low temperature and salinity water originated from the subarctic region with a horizontal scale of 10–20 km and a vertical scale of 100 m in the strain field at the periphery and in the interior of the eddy detected mainly by the surface Okubo-Weiss parameter. Each patch on the same isopycnal constituted a submesoscale filament. A cold and fresh filament in the intermediate layer in and around the eddy was recently ventilated compared with ambient water, suggesting that submesoscale filaments contribute to a rapid water mass transport from the outside to the inside of the eddy, as well as from the subarctic to the KE region. Filaments at the periphery of the eddy were forced by the convergence in the cross-frontal direction. The horizontal tracer gradient of the filaments evolved in the downstream direction, and 10–50% of the evolution was explained by geostrophic forcing. Moreover, the analysis implied that the evolution of the vertical tracer gradient might have been caused by the vertical shear of the horizontal velocity. The resulting patches were expected to contribute to an effective mixing, suggesting the influence of submesoscale filaments on not only the water mass transport but also the transformation in and around mesoscale eddies in the KE region.

A high-resolution (1/20∘) global ocean general circulation model with graphics processing unit (GPU) code implementations is developed based on the LASG/IAP Climate System Ocean Model version 3 (LICOM3) under a heterogeneous-compute interface for portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and three-dimensional parallelization (also partitioned in the vertical direction) is applied. The HIP version of LICOM3 (LICOM3-HIP) is 42 times faster than the same number of CPU cores when 384 AMD GPUs and CPU cores are used. LICOM3-HIP has excellent scalability; it can still obtain a speedup of more than 4 on 9216 GPUs compared to 384 GPUs. In this phase, we successfully performed a test of 1/20∘ LICOM3-HIP using 6550 nodes and 26 200 GPUs, and on a large scale, the model's speed was increased to approximately 2.72 simulated years per day (SYPD). By putting almost all the computation processes inside GPUs, the time cost of data transfer between CPUs and GPUs was reduced, resulting in high performance. Simultaneously, a 14-year spin-up integration following phase 2 of the Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing was performed, and preliminary results were evaluated. We found that the model results had little difference from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the 1/20∘ LICOM3-HIP can reproduce the observations and produce many smaller-scale activities, such as submesoscale eddies and frontal-scale structures.

Hydrogenetic ferromanganese crusts in the northwestern (NW) Pacific seamounts are considered as potential future sources of strategic metals. The details of their regional and fine-scale variations...

The lateral deformation behaviour of inclined piles in calcareous sand is investigated with model testing and numerical analysis. A model pile is instrumented with quasi-distributed strain sensors ...

The Yellow River Delta is one of the most abundant offshore energy areas in China, and the construction of offshore projects is rapidly developing. In this paper, four typical regions of the Yellow...

In this study, laboratory experiments are conducted to assess the effects of a set of novel ring-type collars and prevalent spiral threading around a circular pier on scouring in a clear-water flow...

Based on the nonlinear Winkler theory, a simplified method for evaluating the lateral bearing capacity of the caisson-pile foundation (CCPF) considering the effect of scour-hole dimensions was prop...

The article analyzes the position of individual and average data points of the Archean and Early Proterozoic metaaleuropelites (Isua and Akilia associations, West Greenland; Beit Bridge Complex, Limpopo Province, South Africa; Moodies, Mozaan, and Pretoria groups, Barberton Mountain Land, South Africa; Kola Group, Baltic Shield, Russia; Nurmes paragneisses, Eastern Finland; Onot greenstone belt, southeastern Sayan region, Russia; Rampur Group, Lesser Himalayas, India; Kan metamorphic complex, eastern Sayan region, Russia; Ladoga Group, northern Ladoga region, Russia; Yenisei metamorphic complex, Russia; and others) in the (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams with classification fields constructed from data on the content of REE and Th in the fine grained clastic/aleuropelitic sediments near the estuary of different-category modern rivers, according to (Bayon et al., 2015). It has been shown that the vast majority of data points of metaaleuropelites are localized in fields 1 (particulates of major rivers in the world), 2 (particulates of rivers draining sedimentary substrates) and 4 (particulates of rivers flowing through volcanic rock terrains), as well as the zone overlapping fields 1–3 (particulates of rivers feeding on erosion products of the magmatic/metamorphic terrains). Data points of all examined objects with an age of more than 2.8 Ga in the (La/Yb)N–Eu/Eu* diagram are concentrated mainly in field 4. If all our assumptions are correct, these observations suggest the following conclusion: until the above-indicated time, large rivers and, most likely, rivers draining mainly sedimentary rocks did not exist, and processes of the recycling of fine-grained aluminosiliciclastics were reduced.

Vietnam is a country with diverse and abundant mineral resources with nearly 5000 mines and ore spots of about 60 different minerals. Mining and processing of mineral resources have contributed about 9.6–10.6% of the country’s GDP since the year of 2000. However, the exploitation and processing of mineral resources have been leading to a certain soil and sediment contamination by heavy metals. Soil and sediment samples around lead-zince mines have been collected and analyzed for Cu, Zn, As, Cd, Hg, Pb and Ni in Cho Don district, Bac Kan province, Vietnam. Single pollution, geoaccumulation and enrichment indices have been used for assessing the sediment quality in terms of heavy metals by comparison with threshold and ecological risk limits. High concentration of Cu and Zn in the sediment is due to extremely high content of the two metals in the ore-surrounding soil in the lead-zinc mines, i.e. high background values. High concentration of As and Cd in the sediment is affected in a greater extent by high content of the two metals in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. High Pb concentration in sediment is affected in a greater extent by high content of the metal in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. The pollution sequence based on an average single pollution index is Pb(125.76) > As(55.48) > Zn(26.82 > Cd(14.17) > Cu(5.08) > Ni(1.36) > Hg(0.42), while based on the average geoaccumulation index, the sediment is mostly uncontaminated with the sequence Cd(1.1) > As(0.7) > Cu, Zn, Hg, Pb, Ni( Hg(4.1) > Pb(1.4) > Cu(0.9) > Ni(0.6). The results highlight the need for a comprehensive and detailed study program on heavy metal content in different soil and sediment resources to identify the magnitude and details of the problem associated with heavy metal contamination for development of a remediation plan and more effective pollution preventing measures including technology develop for recovering of useful components.

The chemical and isotopic compositions of manganese carbonate and oxide ores and host dolomites of the Porozhinsk deposit are studied. Manganese carbonates are characterized by low values of δ13C (–19.0 to –8.4‰, PDB) and δ18O (8.8 to 27.3‰, SMOW). These data indicate the participation in their formation of the isotopically light carbon from oxidized organic matter, and the water of ore-depositing solutions was most likely meteogenic. The host dolomites (Pod”emsk Formation, Chapa Group) are characterized by a heavier isotopic composition of carbon (2.3‒2.6‰) and oxygen (22.5‒31.3‰) that are typical of marine sedimentary carbonates in the Late Proterozoic sedimentation basin. The simplest organisms played a significant role in the genesis of manganese ores. Microbial structures were preserved in manganese carbonates and oxides.

Satellite observations are used to establish the dominant magnitudes, scales, and mechanisms of intraseasonal variability in ocean dynamic sea level (ζ) in the Persian Gulf over 2002–15. Empirical orthogonal function (EOF) analysis applied to altimetry data reveals a basinwide, single-signed intraseasonal fluctuation that contributes importantly to ζ variance in the Persian Gulf at monthly to decadal time scales. An EOF analysis of Gravity Recovery and Climate Experiment (GRACE) observations over the same period returns a similar large-scale mode of intraseasonal variability, suggesting that the basinwide intraseasonal ζ variation has a predominantly barotropic nature. A linear barotropic theory is developed to interpret the data. The theory represents Persian Gulf average ζ () in terms of local freshwater flux, barometric pressure, and wind stress forcing, as well as ζ at the boundary in the Gulf of Oman. The theory is tested using a multiple linear regression with these freshwater flux, barometric pressure, wind stress, and boundary ζ quantities as input and as output. The regression explains 70% ± 9% (95% confidence interval) of the intraseasonal variance. Numerical values of regression coefficients computed empirically from the data are consistent with theoretical expectations from first principles. Results point to a substantial nonisostatic response to surface loading. The Gulf of Oman ζ boundary condition shows lagged correlation with ζ upstream along the Indian subcontinent, Maritime Continent, and equatorial Indian Ocean, suggesting a large-scale Indian Ocean influence on intraseasonal variation mediated by coastal and equatorial waves and hinting at potential predictability. This study highlights the value of GRACE for understanding sea level in an understudied marginal sea.

The circulation in the northern South China Sea (SCS) strongly responds to anticyclonic eddies that shed from the Kuroshio intruding across Luzon Strait. An eddy tracking algorithm was applied to 26 years of altimetry data to better quantify the surface characteristics of eddies in and near the Luzon Strait with an emphasis on eddies with significant westward propagation across the northern SCS. Spatial mean eddy characteristics revealed that the most robust anticyclonic eddies are in the region of 20–22° N and 118–120° E (where eddies have been observed to shed from the Kuroshio into the northern SCS) and in the North Pacific Gyre east of the Luzon Strait (18–22° N, 121–124° E). The composite structure of mesoscale eddies revealed stronger, more high-amplitude eddies east of the Kuroshio for both circulation types, which was true in all seasons but the starkest contrast was during the summer monsoon. We then isolated the ten farthest westward-propagating eddies that generated in the Luzon Strait region. The majority of these long-propagating eddies occurred during the boreal fall and winter when the cyclonic basin-scale circulation was conducive to eddy propagation along the Chinese shelf break. Using the Kuroshio South China Sea Index (KSI), we find that a highly viable condition for generation of North Pacific Gyre eddies that propagated westward across the Luzon Strait was found when the Kuroshio bifurcates with one branch into the northern SCS and the other northward along eastern Taiwan. In this state, an anticyclonic eddy can generate east of the Kuroshio and be advected into the SCS.

To clarify the Tsushima Warm Current (TWC) system around a downstream region of Noto Peninsula (NP) where Toyama Trough (TT) causes a discontinuity of the along shelf-current, numerical experiments were performed using two-layered ocean model with simplified bottom topography. When a current trapped by the continental slope representing an offshore branch of TWC (OB) encounters the NP and TT, the OB was trapped by the coast facing the TT. A clockwise lee-eddy developed between a current axis and a coastline over the TT, which results in a current path transition offshore (CPT). The OB finally adjusted to a current path which crosses TT by shifting from the discontinuity point of the continental slope. If a coastal current representing a coastal branch of the TWC (CB) developed under this situation, the CB also formed lee-eddy within the identical region of the OB’s eddy, resulting in CPT. Period for the CPT of the CB was shorter with increase of the OB volume transport. These results indicate that the OB acted to accelerate CPT of the CB within the TT. To support these results, observational data comprising mooring current, tidal, and CTD measurements obtained in and around the TT, along with the output from high-resolution data-assimilated ocean model DR_C were analyzed. Although the lee-eddy of the CBs was generated in every summer, the CPT events did not fully develop when the OB was absent over the continental slope because of the slow growth rate of the lee-eddy.

Long-term arrays of satellite optical measurements of Landsat-5,7,8 and Sentinel-2 were used to describe the characteristics of submesoscale eddy (SE) dynamics in different parts of the Crimean coast: their geometric and kinematic characteristics, the main sites and mechanisms of formation, and impact on the redistribution of suspended matter. The dynamic characteristics of SE were computed on the base of the 4D variational assimilation method from the pair of consecutive Landsat-8/Sentinel-2 images. The orbital velocity of submesoscale cyclonic eddies (SCE) with a diameter of 1 km reaches 0.15 m/s, indicating the cyclostrophic balance with a high Rossby number (RO) exceeding 2. Submesoscale cyclones were detected much more frequently than the usually larger submesoscale anticyclones. High-resolution satellite imagery gives a possibility to observe complex submesoscale dynamic processes, such as the generation of chains of SCE, large cyclones behind the capes consisting of densely packed arrays of SCEs, topographic submesoscale anticyclones with a number of attached SCEs, mushroom-like current structures, and frontal SE. Despite the diversity of the processes considered, several basic mechanisms of formation of submesoscale eddies can be identified on the basis of satellite data: (1) Separation of the boundary current, often wind-driven, behind the capes; (2) barotropic instability due to the horizontal shear on the coastal periphery of mesoscale anticyclones or alongshore currents; (3) formation of the mushroom-like structure due to the interaction of offshore currents with deep waters near the capes or due to offshore winds; and (4) frontal instabilities on the coastal upwelling. The results of the analysis were used to create a scheme of the spatial variability of submesoscale processes near the Crimean coast and compare it to the results of the high-resolution modeling. The model was able to describe the main areas of SE formation, which was located near the major capes. It provides additional data about SE generation near the rocky capes of the South Crimea, where satellite data was limited by the absence of optical tracers.

Currents in the Baltic Sea are generally weak, but during strong winds they can grow high enough to affect the surface wave propagation and evolution. To evaluate the significance of wave-current interactions in the Baltic Sea, we conducted a study using the wave model WAM, comparing a run without surface currents to one with current forcing from a NEMO hydrodynamical model simulation. The overall changes to the wave field caused by currents were quite small. Changes of over 10 cm in significant wave height (SWH) or 1 s in the peak period (Tp) occurred only in some areas and typically less than 3% of the time. Current refraction changed the SWH annual mean by up to 2 cm, but changes up to 60 cm were seen in the maximum values. Tp had occasionally large changes due to shifts in the peak energy in two-peaked swell and wind-sea spectra. Including currents typically led to a stronger changes in swell energy compared to the changes in wind sea energy. A comparison with a wave buoy in the Gulf of Finland showed that this change in the swell energy improved the accuracy of the simulation in this narrow gulf. Current-induced refraction was most prominent near the coastal areas, where current speed occasionally exceeded 0.3 m/s. In general, SWH decreased in the coastal areas with strong currents and slightly increased in adjacent open sea areas. The current effects were most frequent in the Gulf of Finland, the Western Gotland Basin and the Åland Sea.

Analysis and design with simple correlations are always of interest to engineers. Predicting the bearing capacity of a spudcan in a multi-layered clay soil is one of the challenges facing jack-up d...

The South Atlantic subtropical underwater (STUW) is a high-salinity water mass formed by subduction within the subtropical gyre. It is a major component of the subtropical cell and affects stratification in the downstream direction due to its high salinity characteristics. Understanding the interannual variability in STUW subduction is essential for quantifying the impact of subtropical variability on the tropical Atlantic. Using the output from the ocean state estimate of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO), this study investigates the interannual variability in STUW subduction from 1992 to 2016. We find that heat fluxes, wind stress, and wind stress curl cause interannual variability in the subduction rate. Heat fluxes over the subduction area modulate the sea surface buoyancy and regulate the mixed layer depth (MLD) during its deepening and shoaling phases. Additionally, the wind stress curl and zonal wind stress can modulate the size of the subduction area by regulating the probability of particles entrained into the mixed layer within 1 year of tracing. This analysis evaluates the influence of subtropical wind patterns on the South Atlantic subsurface high-salinity water mass, highlighting the impact of heat and wind on the interannual changes in the oceanic component of the hydrological cycle.

To examine the coral reef limestone–concrete shear failure characteristics, we conducted large-scale direct shear tests to study five types of interfaces: planar, sloped, arc shaped, stepped, and t...

The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the Kamchatka Eddy (KE). This eddy is quasi-stationary. More generally, the oceanic region east of the EKC contains many eddies, several of them large and long lasting. Using surface currents derived from altimetry, particle tracking and a simple two-dimensional numerical model of fluid flow, we investigate the variability of this eddy field, the generation of eddies in the bays of Kamchatka by the EKC and fluxes of water to and from these bays. Firstly, we recover in our analysis of long-lasting eddies, the main eddies of the region. Among strong eddies, the parity bias favors anticyclones. Our numerical simulations give a possible explanation for the process of eddy creation in the bays of the peninsula and show that the northernmost bay produces most anticyclones. Then, we track forward the water particles from these bays and we determine their fate in the open ocean; southeastward and southwestward trajectories are the most frequent. We also track water particles backward from the KE site; they often drift near the Kamchatka coast, but others drift south of this site and remain there, a priori trapped in other eddies. This study confirms the complexity of mesoscale motions and water exchanges in this region.

A recent linear stability analysis and a numerical simulation suggest that diffusive convection (DC), a regime of the double-diffusive convection, plays a potential role in onset of thermohaline–shear instability, implying that DC could contribute to turbulence production in the oceans. However, an existence of such a thermohaline–shear instability has not been examined in real oceans. We examine if this newly proposed instability mechanism exists in the subarctic North Pacific by analyzing our fine- and micro-scale turbulence measurement data. Vertical inversions were cautiously detected in seawater density profiles and used as a proxy for instability events for gradient Richardson number larger than the critical value of 1/4. We found that a portion of inversions were associated with active DC. Such DC-related inversions exhibited elevated levels of turbulent kinetic energy dissipation rate even for gradient Richardson number largely exceeding 1/4. Our estimate suggested that the thermohaline–shear instability contributes to roughly only 10% of the dissipation of turbulent kinetic energy in the diffusively convective layer in our observation site.

The response of a jet to sudden winds was examined using a simple numerical regional model and an analytical model to investigate the mechanism underlying the local wind dynamics of seasonal velocity variations in the upper layer of the Kuroshio. The numerical model was used to simulate the distinct seasonal features in summer and autumn in the East China Sea and successfully reproduced the seasonal features in the velocity field under different sudden wind conditions. The current speed increased and decreased under summer and autumn wind conditions, respectively; and the current axis shifted to the offshore and inshore sides under summer and autumn wind conditions, respectively. We focused on the current speed variation and hypothesized that the current speed variation is forced by the thermocline variation due to nonlinear Ekman pumping. This hypothesis was examined using a rigid-lid reduced-gravity analytical model with Ekman layer dynamics. The analytical model results showed that the asymmetry of the jet profile has a marked effect on the current speed variation. With a higher wavenumber on the west side of a northward jet, the current speed increased and decreased under summer and autumn wind conditions, respectively. These findings can be used to explain the seasonal velocity variations in the upper layer in the East China Sea and over the entire Kuroshio path.

Herein, seasonal velocity variations from the sea surface to a depth of 1000 m over the entire Kuroshio path are investigated using satellite altimetry and reanalysis datasets. The data analysis results show that velocities in the upper layer (from 0 to approximately 500 m) reach a maximum in July and a minimum in autumn (October to November) or winter (December to February) with different tendencies in each region. However, those in the lower layer (> 500 m depth) show a reversed seasonal variation—reaching a maximum in winter—especially in the continental slope area from the east of Luzon Island to the east of the Ryukyu Islands chain, which is regarded as a route of the deeper Kuroshio flow. Using a realistic general circulation model, we performed numerical experiments to clarify the role of the local wind stress as the driving force in seasonal Kuroshio velocity variations in the upper layer. These experiments revealed that seasonal Kuroshio velocity variations in the upper layer are mainly caused by the local response to wind stress upon the current itself. These numerical results cannot be explained by conventional mechanisms, such as flow–topography interactions or coastal upwelling/downwelling. On the other hand, seasonal Kuroshio velocity variations in the lower layer can be explained by the Sverdrup theory, in which barotropic responses to the wind stress curl over the area west of the Izu–Ogasawara Ridge are responsible.

—The area of southwestern Crimea includes the ending of the Crimean Mountains that arose during the neotectonic activation at the place of the Cretaceous–Paleogene denudation plain and the adjacent shallow-water carbonate sedimentation basin. The Crimean Mountains are one of the links of the Alpine–Himalayan orogenic belt formed during the collision of the Eurasian, African, and Indo–Australian plates. Their area includes late Cenozoic marine terraces of the complete Mediterranean series and a staircase of Neogene, Paleogene and Cretaceous planation surfaces over them. The planation surfaces of different ages resulted from the successive lowering of the World Ocean level. Their subsequent deformations make it possible to outline the area of the neotectonic uplifting and determine its parameters. The main mechanism of the neotectonic activation was the thrust of the East Black Sea microplate under the Scythian one and the formation of a ramp fold structure. The amplitude of the neotectonic uplifting of southwestern Crimea for the past 2 Myr varies from 0 to 800 m, i.e., is up to 0.04 mm/year. The recent neotectonic structure of the area is formed by the northern flank of the ramp fold; it is a monocline of NW dip consisting of “keys” of NW strike separated by the latest faults with vertical displacements of 10 to 120 m. The uplifting of the area and the lowering of the World Ocean level led to a widespread of denudation surfaces. Their good preservation makes it possible to refine the sequence of neotectonic events, whose first pulses reached the study area in the Oligocene, and the main activation phase began in the Pliocene.

River morphological processes are among the most complex and least understood phenomenon in nature. Recent research indicates that the braiding of marine waterways of the estuary zone occurs at an ...

The insufficiency of research on the calculation of the sidewall friction of large and deep-water caissons lies in that the longitudinal and lateral distribution of the sidewall friction is not cle...

The coexistence of multiple wave systems generated locally and by remote storms is common in the ocean and its quantification is required in the design of marine facilities. This study identifies the multimodal sea states at six locations in the shelf seas of India based on partitioned wave output data from numerical model WAVEWATCH-III for 26 years (1990 to 2015). The different systems are identified by the propagation direction and frequencies with a relatively high probability of occurrence of spectral partitions. Four to seven types of distinct clusters of wave systems are present among the study locations. The occurrence of these systems and co-occurrence of this with other systems are examined. The southernmost location experiences the effect of seven wave systems. At all locations, two wave systems from the south with relatively low partial significant wave height (Hs) are present for more than 71% of the time and co-occurred with other systems during 2–67%. The most energetic systems are observed 23% (system 5 at station 3) to 60% (system 4 at station 4) of the time with maximum mean partial Hs values of 1 to 3 m during summer monsoon months. The southernmost location (3) experienced maximum opposing (18%) and crossing (78%) sea states.

We used historical CTD observations and Argo data to obtain the characteristics of the Kamchatka Current halocline and its eddies. Kamchatka Current eddies have a cold low salinity core in contrast with Aleutian eddies that contain warm and saline waters of Alaskan Stream origin. The Kamchatka Current eddies are smaller with diameter of ~ 100–120 km. Kamchatka Current eddies have a thick cold layer in a halocline. The temperature in their core increased by ~ 2.4 °C from the beginning of observations in 1990, while salinity decreased. We found that 2012 was the coldest year in the Kamchatka Current. Record-breaking warming occurred in the Kamchatka Current during 2015 to 2018. Temperature in the halocline rose by ~ 3 °C from 2012 to 2018 at 26.6σθ, while in the western Bering Sea temperature rose by 2.3 °C. It is plausible that the warming in the Kamchatka Current halocline during 2012 to 2018 is associated with the lowest recorded sea ice coverage in the Bering Sea. Similar warming occurred in the Oyashio Current. Salinity, temperature and specific density in the 2012 Simushir eddy were extremely low for the 30-year row of observations from 1990 to 2020. Extremely low salinity was also found in the 2012 Aleutian eddy off the Near Strait.

Lake Urmia is located in the northwest of Iran and shared between the provinces of West Azarbaijan and East Azarbaijan. In the last two decades, there has been a considerable decline in the lake’s ...

The Southern Ocean has a profound impact on the Earth's climate system. Its strong winds, intense currents, and fierce waves are critical components of the air-sea interface and contribute to absorbing, storing, and releasing heat, moisture, gases, and momentum. Owing to its remoteness and harsh environment, this region is significantly undersampled, hampering the validation of prediction models and large-scale observations from satellite sensors. Here, an unprecedented data set of simultaneous observations of winds, surface currents, and ocean waves is presented, to address the scarcity of in situ observations in the region-https://doi.org/10.26179/5ed0a30aaf764 (Alberello et al., 2020c) and https://doi.org/10.26179/5e9d038c396f2 (Derkani et al., 2020). Records were acquired underway during the Antarctic Circumnavigation Expedition (ACE), which went around the Southern Ocean from December 2016 to March 2017 (Austral summer). Observations were obtained with the wave and surface current monitoring system WaMoS-II, which scanned the ocean surface around the vessel using marine radars. Measurements were assessed for quality control and compared against available satellite observations. The data set is the most extensive and comprehensive collection of observations of surface processes for the Southern Ocean and is intended to underpin improvements of wave prediction models around Antarctica and research of air-sea interaction processes, including gas exchange and dynamics of sea spray aerosol particles. The data set has further potentials to support theoretical and numerical research on lower atmosphere, air-sea interface, and upper-ocean processes. .

A large number of water masses are presented in the Atlantic Ocean, and knowledge of their distributions and properties is important for understanding and monitoring of a range of oceanographic phenomena. The characteristics and distributions of water masses in biogeochemical space are useful for, in particular, chemical and biological oceanography to understand the origin and mixing history of water samples. Here, we define the characteristics of the major water masses in the Atlantic Ocean as source water types (SWTs) from their formation areas, and map out their distributions. The SWTs are described by six properties taken from the biased-adjusted Global Ocean Data Analysis Project version 2 (GLODAPv2) data product, including both conservative (conservative temperature and absolute salinity) and non-conservative (oxygen, silicate, phosphate and nitrate) properties. The distributions of these water masses are investigated with the use of the optimum multi-parameter (OMP) method and mapped out. The Atlantic Ocean is divided into four vertical layers by distinct neutral densities and four zonal layers to guide the identification and characterization. The water masses in the upper layer originate from wintertime subduction and are defined as central waters. Below the upper layer, the intermediate layer consists of three main water masses: Antarctic Intermediate Water (AAIW), Subarctic Intermediate Water (SAIW) and Mediterranean Water (MW). The North Atlantic Deep Water (NADW, divided into its upper and lower components) is the dominating water mass in the deep and overflow layer. The origin of both the upper and lower NADW is the Labrador Sea Water (LSW), the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW). The Antarctic Bottom Water (AABW) is the only natural water mass in the bottom layer, and this water mass is redefined as Northeast Atlantic Bottom Water (NEABW) in the north of the Equator due to the change of key properties, especially silicate. Similar with NADW, two additional water masses, Circumpolar Deep Water (CDW) and Weddell Sea Bottom Water (WSBW), are defined in the Weddell Sea region in order to understand the origin of AABW.

This study modeled Stokes drift in the marginal ice zone (MIZ) of the Arctic Ocean using WAVEWATCH III. Applying two viscoelastic and one empirical frequency-dependent wave–ice models, modeled wave parameters and spectra were compared with field observations from the Beaufort–Chukchi Sea. The three wave–ice parameterizations showed similar ability in reproducing the surface Stokes drift estimated using buoy measurements. Comparison with buoy drift showed the estimation of total surface drift was improved by considering Stokes drift during significant wave events. Based on 5-year (2015–2019) hindcasted directional spectra of the summer-autumn Arctic, we investigated monthly mean surface Stokes drift (1–10 cm/s), e-folding depth (1–14 m), and vertically integrated transport (< 0.23 m2/s) in the MIZ. The results showed that Stokes drift in the MIZ increased in strength from July to October. When bulk wave parameters were adopted to estimate Stokes drift fields, the surface Stokes drift was underestimated by about 34–50%, while the Stokes e-folding depth was overestimated by approximately 1.4–5.0 times, increasing from the interior to the edge of the ice cover. We compared the modeled surface Stokes drift with the Eulerian mean flow from reanalyzed data. It showed the mean surface Stokes drift is typically approximately 30% of the Eulerian current over large parts of the Arctic Ocean MIZ with mean ice concentration < 60%, and is the same order of magnitude as (or even larger than) some areas of the Chukchi, East Siberian, and Laptev Seas. It implies Stokes drift should be considered to improve modeling of the dynamic processes of sea ice, especially ice floe drift.

Wind dominates the ocean surface circulation in the subtropical coastal upwelling regions. Although the wind events in these regions are mostly favorable for upwelling, other types of wind events are occasionally dominant. The typical patterns and statistics of wind events over the waters off northern Baja California are described. The identification of wind events was carried out using a systematic technique based on both the admittance magnitude and phase. This technique proved useful and has some of the crucial characteristics expected from a classification standpoint. This technique is applied to 29 years (1990–2018) of cross-calibrated multiplatform (CCMP) 10-m wind data. Equatorward along the coast (upwelling-favorable), offshore (Santa Ana), onshore, poleward along the coast (downwelling-favorable), and relaxation events are identified. The wind stress and wind stress curl mean fields and the statistics of occurrence are described on a year-to-year and month-to-month basis for each wind type. The upwelling-favorable and relaxation events are the most frequent and occur throughout the year; the typical duration is 4 and 1.5 days, respectively. The offshore (Santa Ana), onshore, and poleward wind events are sporadic and occur only during autumn-winter. The year-to-year variation of the frequency of occurrence of the equatorward wind events shows no trend during the study period.

The classification of seabed soil in the Yellow River Subaquatic Delta can be obtained more accurately by cone penetration test (CPT). The Soil behavior type index (Ic), over-consolidation ratio (O...