Primary productivity of an aquatic system like Arabian Sea is broadly determined by the concentration of Chlorophyll-a (Chl-a/Ca) pigment. The present study is essaying to validate the Chl-a data set of prominent ocean color sensors (OC3M - MODIS, OC-OCM2, and OC3V-VIIRS) with sea truth data, collected from 204 stations for three year period (2015-2017). The in-situ concentrations of Chl-a depicts the geographic region under the mesotrophic and eutrophic spans ((0.1>Ca>1.0 mg m-3). The ratio of CaOCM2/CaIn-situ is 0.97±0.27 mg m-3 (n=199), in unsimilarity with CaVISSR/CaIn-situ is 1.75±0.79 mg m-3 (n=170) and CaMODIS/CaIn-situ is 2.53±1.42 mg m-3 (n=158). The regression analysis proclaims a moderate significant relationship for MODIS (r2 = 0.36; p<0.001), followed OCM2 (r2 = 0.32; p<0.001) and VISSR (r2 = 0.19; p<0.001) with evident overestimation (MODIS and VIRRS) and in tune (OCM2) with the satellite-derived datasets. The global ocean color missions aimed to set RMSE error at 0.35, the OCM2 shown the lowest RMSE as 0.13, which is relatively lower than the reference error limit. In overall performance among three algorithms, the OCM2 will provide a better estimation of Chl-a with a prediction of 32% accuracy and 34.37 % of bias. The log bias values for MODIS (0.35) and VIIRS (0.20) algorithms indicating the overestimation of Chl-a with in-situ concentrations, but the OCM2 algorithm is suitable in the region with a negligible bias of -0.03. The biogeochemical processes and ecosystem characteristics are dynamic from region to region, as yet in its urgent need to validate global and formulate regionally tuned algorithms periodically.

An unusually large positive salinity anomaly was observed across the eastern Gulf of Maine (GoM) in winter 2017-2018. Buoy measurements in Jordan Basin found this anomaly extended down to at least 100 m, the deepest mixing observed in the past 19 years. Similarly, this is the strongest positive regional salt anomaly in sea surface salinity (SSS) satellite observations. To determine the source waters driving this event and to diagnose the relative importance of forcing processes, passive tracer adjoint sensitivity experiments are performed using a data assimilating version of the Regional Ocean Modeling System. The model shows that northeastward Scotian Shelf wind anomalies cause a dramatic decrease in freshwater transport to Jordan Basin, which leads to an early winter upper water column salinity surplus. This salinity change weakens the normally haline-controlled vertical stratification across the eastern Gulf. Modeled upper ocean density and vertical diffusivity from 2007-2021 both show a maximum in January 2018. Winter 2017-2018 is the only period where the enhanced winter mixing extends below 100 m. Thus, anomalous vertical entrainment of saltier subsurface Gulf water is the major factor driving the extreme positive satellite-observed SSS anomaly across the eastern Gulf including Jordan Basin. Other factors, including a modest increase in wind-forced slope water transport, and positive fall 2017 salinity anomalies on the Scotian Shelf and Slope Sea appear to play lesser roles in the observed salinification. The adjoint sensitivity analysis demonstrates its utility for back tracing transport pathways for periods of several months.

Oceanic Transform Faults (TF) comprise first order discontinuities bounded between mid-ocean ridge spreading centres. TF mainly accommodate strike slip motion, separating lithospheric plates of different age and thermal structure. Oceanic TF are intriguing in that they do not produce earthquakes as large as might be expected given their long length, with seismic slip corresponding only to a small fraction of the total tectonic slip. The relative geologic simplicity of oceanic TF means that they are an important analogue for more hazardous continental TF, with high potential for improving insights into the earthquake cycle. We investigate the earthquake properties along Chain, a ~300 km long TF in the equatorial MAR by combining both microseismic and teleseismic data. We use the ~1-year microseismicity data (total of 812 events) gathered during the PI-LAB (Passive Imaging of the Lithosphere-Asthenosphere Boundary) experiment and EURO-LAB (Experiment to Unearth the Rheological Lithosphere-Asthenosphere Boundary). We perform cluster analysis in multi-dimensional phase space, consisting of various seismic (epicentral coordinates, magnitude) and geophysical (gravity anomalies, bathymetry, tidal height) parameters. We investigate potential triggering mechanisms, including tidal, static and dynamic stresses. We extend our analysis back in time by considering stronger earthquakes (MW>~5.0) from Global Centroid Moment Tensor (GCMT) since 1976. We find three unique, 50-100 km long clusters or segments from our analysis going from east to west, separated by seismic gaps. Microseismic activity is highest at the eastern segment of Chain where there is the largest positive flower structure, negative rMBA gravity anomaly but very few M>5.5 events. The western segment has reduced seismicity rates relative to the eastern, and is associated with a positive rMBA and a few small flower structures. The central segment is bounded between two seismic gaps and demonstrates relatively high activity rates in the middle. Our result suggests that trans-pression of highly altered mantle/crust and/or high pore pressure due to hydrothermal fluid circulation in the eastern flower structure enhances seismic activity. Overall, we find the existence of consecutive locking and creeping segments, with some of the patches exhibiting hybrid behaviour, potentially causing their sporadic activation/reactivation.

Hydrothermal alteration of ultramafic rock (serpentinization) creates extremely reducing (H2-rich) fluids in the oceanic crust, resulting in strong thermodynamic drives to reduce CO2 to organic molecules in the absence of life. Timescales on which such hydrothermal fluids circulate (thus produce or destroy such organic molecules) have remained enigmatic. In their new publication, Moore et al. (2021, https://doi.org/10.1029/2021JC017886) present compelling radioisotope-based estimates of fluid residence times in a widely known site of purported abiotic synthesis - the Lost City Hydrothermal Field. Using a model that accounts for the sorptive behavior of Ra radionuclides during circulation, they find that fluids at Lost City must have inordinately short residence times, averaging 0.5 to 2 yr or less. The study represents a critical step forward in our understanding of Earth’s abiotic organic kitchen, as it now places a constraint on the timeframe in which such organic molecule creation should occur in such fluids (if at all) prior to venting at the seafloor.

The seasonal Predictability Barrier (PB) of Sea Surface Temperature Anomaly (SSTA) is characterized by a rapid loss of prediction skills at a specific season in dynamic models. To investigate whether this PB phenomenon is caused by the inherent nonlinearity of the air-sea coupled system that leads to chaos under certain conditions, a statistical method - Sample Entropy, was introduced to investigate the spatial-temporal distribution of the chaotic degree of SSTA time series in the tropic Pacific. The results showed that high chaotic values existed in Niño 3 and Niño 3.4 regions in April and May, and in Niño 4 region in May and June, which matched the PB timing previously reported in these regions. Furthermore, the chaotic signal moves westward from March to June longitudinally in the tropical Pacific, leading to a similar linear variation of PB timing along the longitude.

Seismic ambient noise sources have received increased attention recently, creating new possibilities to study the Earth’s subsurface and the atmosphere-ocean-solid Earth coupling. In efforts to locate such noise sources using nonlinear finite-frequency inversions, methodological developments such as pre-computed wavefields and spatially variable grids were necessary. These make inversions feasible for the secondary microseismic sources in a frequency range up to 0.2 Hz on a daily basis. By obtaining a starting model for the inversion using Matched Field Processing (MFP) we are able to further steer the inversion towards acceptable global noise source models and improve the final result. Analysis of one year of daily inversions shows the seasonal variations of the secondary microseisms and their dependence on the atmosphere-ocean-solid Earth coupling due to storm-induced ocean waves. We present a web framework, SANS (Seismic Ambient Noise Sources, sans.ethz.ch), where daily regional- to global-scale seismic ambient noise source maps are made available to the public. This eases the implementation of time-variable noise source distributions into full-waveform ambient noise tomography and time-dependent subsurface monitoring methods. Additionally, it encourages other studies to verify if changes in the seismic data are due to changes in the subsurface velocity or spatio-temporal variations of noise sources.

Past sea-level changes in the Mediterranean Sea are highly non-uniform and can deviate significantly from both the global average sea-level rise and changes in the nearby Atlantic. Understanding the causes of this spatial non-uniformity is crucial to the success of coastal adaptation strategies. This, however, remains a challenge owing to the lack of long sea-level records in the Mediterranean. Previous studies have addressed this challenge by reconstructing past sea levels through objective analysis of sea-level observations. Such reconstructions have enabled significant progress towards quantifying sea-level changes, however, they have difficulty capturing long-term changes and provide little insight into the causes of the changes. Here, we combine data from tide gauges and altimetry with sea-level fingerprints of contemporary land-mass changes using spatial Bayesian methods to estimate the sources of sea-level changes in the Mediterranean Sea since 1960. We find that sea level in the Mediterranean rose slowly until 1990 (0.4±0.5 mm yr-1), at which point it started accelerating significantly, driven by both sterodynamic changes and land-ice loss, reaching an average rate of 3.4±0.3 mm yr-1 in the period 2000-2018. The rate of sea-level rise shows considerable spatial variation in the Mediterranean Sea, primarily reflecting changes in the large-scale circulation of the basin. Since 2000, sea level has been rising faster in the Adriatic, Aegean, and Levantine Seas than anywhere else in the Mediterranean Sea.

Recent progress in the direct measurement of turbulent dissipation in the Arctic Ocean has highlighted the need for an improved parametrization of the turbulent diapycnal diffusivities of heat and salt that is suitable for application in the turbulent environment characteristic of this polar region. In support of this goal we describe herein a series of direct numerical simulations of the turbulence generated in the process of growth and breaking of Kelvin-Helmholtz billows. These simulations provide the data sets needed to serve as basis for a study of the stratified turbulent mixing processes that are expected to obtain in the Arctic Ocean environment. The mixing properties of the turbulence are studied using a previously formulated procedure in which the temperature and salinity fields are sorted separately in order to enable the separation of irreversible Arctic mixing from reversible stirring processes and thus the definition of turbulent diffusivities for both heat and salt that depend solely upon irreversible mixing. These analyses allow us to demonstrate that the irreversible diapycnal diffusivities for heat and salt are both solely dependent on the buoyancy Reynolds number in the Arctic Ocean environment. These are found to be in close agreement with the functional forms inferred for these turbulent diffusivities in the previous work of Bouffard & Boegman (2013). Based on a detailed comparison of our simulation data with this previous empirical work, we propose an algorithm that can be used for inferring the diapycnal diffusivities from turbulent dissipation measurements in the Arctic Ocean.

The Antarctic Slope Current (ASC) plays a central role in redistributing water masses, sea ice, and tracer properties around the Antarctic margins, and in mediating cross-slope exchanges. While the ASC has historically been understood as a wind-driven circulation, recent studies have highlighted important momentum transfers due to mesoscale eddies and tidal flows. Furthermore, momentum input due to wind stress is transferred through sea ice to the ASC during most of the year, yet previous studies have typically considered the circulations of the ocean and sea ice independently. Thus it remains unclear to what extent the momentum input from the winds is mediated by sea ice, tidal forcing, and transient eddies in the ocean, and how the resulting momentum transfers serve to structure the ASC. In this study the dynamics of the coupled ocean/sea ice ASC circulation are investigated using high-resolution process-oriented simulations, and interpreted with the aid of a reduced-order model. In almost all simulations considered here, sea ice redistributes almost 100% of the wind stress away from the continental slope, resulting in approximately identical sea ice and ocean surface flows in the core of the ASC. This ice-ocean coupling results from suppression of vertical momentum transfer by mesoscale eddies over the continental slope, which allows the sea ice to accelerate the ocean surface flow until the speeds coincide. Tidal acceleration of the along-slope flow exaggerates this effect, and may even result in ocean-to-ice momentum transfer. The implications of these findings for along-and across-slope transport of water masses and sea ice around Antarctica are discussed.

The response time of the southern subtropical oceans to an increase in the wind stress is examined in a climate model perturbation simulation where there is an abrupt increase in the wind stress. The ocean response time is shown to vary among fields: The intensification of the gyres and vertical movement of isopycnals happens over 5-10 years, while the change in ideal age, temperature, and salinity in mode and intermediate waters occurs much slower, with the response time exceeding 100 years at depths of 500-1000 m. While the response time for ideal age is longer than that for the surface circulation it is notable that it is much younger than the ideal age itself. The different response times indicate that changes in the winds over the southern oceans and in the horizontal circulation / density structure will occur near simultaneously, but there may be a substantial lag in subsurface changes from wind changes and these may persist for decades even if no further changes in the winds occurs

Isoprene produced by marine phytoplankton acts as a precursor of secondary organic aerosol and thereby affects cloud formation and brightness over the remote oceans. Yet, the marine isoprene emission is poorly constrained, with discrepancies among estimates that reach 2 orders of magnitude. Here we present ISOREMS, the first satellite-only based algorithm for the retrieval of isoprene concentration in the Southern Ocean. Sea surface concentrations from six cruises were matched with remotely-sensed variables from MODIS Aqua, and isoprene was best predicted by multiple linear regression with chlorophyll-a and sea surface temperature. Climatological (2002-2018) isoprene distributions computed with ISOREMS revealed high concentrations in coastal and near-island waters, and within the 40º-50ºS latitudinal band. Isoprene seasonality paralleled phytoplankton productivity, with annual maxima in summer. The annual Southern Ocean emission of isoprene was estimated 61 Gg C yr $\mathrm{^{-1}}$. The algorithm can provide spatially and temporally realistic inputs to atmospheric and climate models.

We have equipped the unstructured-mesh global sea-ice and ocean model FESOM2 with a set of physical parameterizations derived from the single-column sea-ice model Icepack. The update has substantially broadened the range of physical processes that can be represented by the model. The new features are directly implemented on the unstructured FESOM2 mesh, and thereby benefit from the flexibility that comes with it in terms of spatial resolution. A subset of the parameter space of three model configurations, with increasing complexity, has been calibrated with an iterative Green’s function optimization method to test fairly the impact of the model update on the sea-ice representation. Furthermore, to explore the sensitivity of the results to different atmospheric forcings, each model configuration was calibrated separately for the NCEP-CFSR/CFSv2 and ERA5 forcings. The results suggest that a complex model formulation leads to a better agreement between modeled and the observed sea-ice concentration and snow thickness, while differences are smaller for sea-ice thickness and drift speed. However, the choice of the atmospheric forcing also impacts the agreement of FESOM2 simulations and observations, with NCEP-CFSR/CFSv2 being particularly beneficial for the simulated sea-ice concentration and ERA5 for sea-ice drift speed. In this respect, our results indicate that the parameter calibration can better compensate for differences among atmospheric forcings in a simpler model (i.e. sea-ice has no heat capacity) than in more energy consistent formulations with a prognostic ice thickness distribution.

There are growing evidences that the warming marginal seas impact the torrential rainfall events in many parts of the world. The sea surface temperature (SST) in the East Asian marginal seas (EAMS) exhibits rapid rise during the last decades compared to the global mean, but its impact is still a matter of debate. Here we assess the impact of the recent warming trend of the EAMSs on the torrential rainfall event that caused devastating flooding and landslides in Kyushu Island located in the western part of Japan in July 2017, using a high-resolution cloud permitting model. The warming trend of EAMS with atmospheric warming since 1980s increases the simulated 12-hr precipitation to 6.8%, corresponding to approximately 10% increase per 1 K of SST rise, consistent with the previous data analysis study. Slight increase in heat and moisture supplies due to the warming EAMS has impacted a conditionally unstable condition of air masses flowing into an area of the precipitation, leading to more vigorous convective systems. Moisture budget analysis indicates that the changes in the amount of precipitation is not responsible for the availability of precipitable water but the intensification of the convective system. Since the change in precipitation amount exhibits high sensitivity to the SST trends, use of multiple SST datasets is desirable to provide a more reliable estimate and its uncertainty.

Estimating surface heat fluxes via direct covariance measurements or bulk formulae is observation-intensive and costly. We present a methodology whereby we estimate net surface heat fluxes as the difference between the depth-integrated heat tendencies and the depth-integrated horizontal heat exchanges in a hydrodynamic model. We calibrate the model to achieve a good representation of mixing and advection and then assimilate satellite sea-surface-temperature (SST) observations into the model at an eight-day scale. The SST data assimilation forces a good representation of observed temperatures and heat tendencies both at the surface and throughout the water column. We estimate the horizontal heat exchange directly from the model output and then infer the surface fluxes required to close the budget. When we apply this methodology to a model with prescribed surface heat fluxes and without data assimilation, we can recover the prescribed fluxes with an RMS error of ±10 Wm−2 and an r2 of 0.998. When we compare our results to those estimated using COARE bulk formulae with observations in western Long Island Sound, we find similarly good agreement.

We develop a data assimilation scheme with the Icosahedral Non-hydrostatic Earth System Model (ICON-ESM) for operational decadal and seasonal climate predictions at the German weather service. For this purpose, we implement an Ensemble Kalman Filter to the ocean component as a first step towards a weakly coupled data assimilation. We performed an assimilation experiment over the period 1960-2014. This ocean-only assimilation experiment serves to initialize 10-year long retrospective predictions (hindcasts) started each year on 1 November. On multi-annual time scales, we find predictability of sea surface temperature and salinity as well as oceanic heat and salt contents especially in the North Atlantic. The mean Atlantic Meridional Overturning Circulation is realistic and the variability is stable during the assimilation. On seasonal time scales, we find high predictive skill in the tropics with highest values in variables related to the El Niño/Southern Oscillation phenomenon. In the Arctic, the hindcasts correctly represent the decreasing sea ice trend in winter and, to a lesser degree, also in summer, although sea ice concentration is generally much too low in both hemispheres in summer. However, compared to other prediction systems, prediction skill is relatively low in regions apart from the tropical Pacific due to the missing atmospheric assimilation. In addition, we expect a better fine-tuning of the sea ice and the oceanic circulation in the Southern Ocean in ICON-ESM to improve the predictive skill. In general, we demonstrate that our data assimilation method is successfully initializing the oceanic component of the climate system.

Estuaries are the transitional systems between the riverine freshwaters and the ocean salt water. Increasing salt-wedge intrusions are mentioned as one of the major impacts of climate change in coastal areas. We propose a new methodology to predict salt wedge intrusions with an intermediate complexity model, so-called Estuarine Box Model (EBM), that allows to use hydrology and ocean climate scenarios to predict salt wedge intrusions. We apply this methodology to the Goro branch of the Po river flowing into the Northern Adriatic Sea. A 30 years’ period (1982-2011) is used to train and test the EBM that is then used to project the salt wedge in the (2021-2050) time period under the RCP8.5 emission scenario. The numerical results show that in the (2021-2050) period, the Po di Goro salt wedge intrusion length will increase by 15% on an annual basis (up to 50% in summertime) and the outflowing salinity will increase 9% on annual basis (up to 35% in summer). Finally, a statistical estimation of the extreme values of salt wedge and outflowing salinity shows return periods of 10 years for extremes twice the present mean values. It means that a 16 Km of salt-wedge intrusion, and outgoing salinity about 28 psu are highly expected as an extreme event with 10 years return period

North Pacific atmospheric and oceanic circulations are key missing pieces in our understanding of the reorganisation of the global climate system since the Last Glacial Maximum (LGM). Here, using a basin-wide compilation of planktic foraminiferal δ18O, we show that the North Pacific subpolar gyre extended ~3 degrees further south during the LGM, consistent with sea surface temperature and productivity proxy data. Analysis of an ensemble of climate models indicates that the expansion of the subpolar gyre was associated with a substantial gyre strengthening. These gyre circulation changes were driven by a southward shift in the mid-latitude westerlies and increased wind-stress from the polar easterlies. Using single-forcing model runs, we show these atmospheric circulation changes are a non-linear response to the combined topographic and albedo effects of the Laurentide Ice Sheet. Our reconstruction suggests the gyre boundary (and thus westerly winds) began to migrate northward at ~17-16 ka, during Heinrich Stadial 1.

Atmospheric input of trace element micronutrients to the oceans is difficult to determine as even with collection of high-quality aerosol chemical concentrations such data by themselves cannot yield deposition rates. To transform these concentrations into rates, a method of determining flux by applying an appropriate deposition velocity is required. A recently developed method based on the natural radionuclide Be has provided a means to estimate the bulk (wet + dry) deposition velocity (V) required for this calculation. Here, water column Be inventories and aerosol Be concentrations collected during the 2018 US GEOTRACES Pacific Meridional Transect are presented. We use these data together with those from other ocean basins to derive a global relationship between rain rate (m/y) and bulk depositional velocity (m/d), such that V= 999±96 x Rain rate + 1040±136 (R=0.81). Thus with satellite -derived rainfall estimates, a means to calculate aerosol bulk deposition velocities is provided.

An efficient combination of the data collected by multiple instruments and platforms is needed to obtain accurate 3D ocean state estimates, representing a fundamental step to describe ocean dynamics and its role in the Earth climate system and marine ecosystems. Observations can either be assimilated in ocean general circulation models or used to feed data-driven reconstructions and diagnostic models. Here we describe an innovative deep learning algorithm that projects sea surface satellite data at depth after training with sparse co-located in situ vertical profiles. The technique is based on a stacked Long Short-Term Memory neural network, coupled to a Monte-Carlo dropout approach, and is applied here to the measurements collected between 2010 and 2018 over the North Atlantic Ocean. The model provides hydrographic vertical profiles and associated uncertainties from corresponding remotely sensed surface estimates, outperforming similar reconstructions from simpler statistical algorithms and feed-forward networks.

Hearty, P. J., Rovere, A., Sandstrom, M. R., O’Leary, M. J., Roberts, D., & Raymo, M. E. (2020). Pliocene‐Pleistocene stratigraphy and sea‐level estimates, Republic of South Africa with implications for a 400 ppmv CO2 world. Paleoceanography and Paleoclimatology, 35, e2019PA003835. https://doi.org/10.1029/2019PA003835 The Mid-Pliocene Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3 Ma) records, offers potential past analogues for our 400-ppmv world. The coastal geology of western and southern coasts of the Republic of South Africa expose an abundance of marine deposits of Pliocene and Pleistocene age. In this study, we report differential GPS elevations, detailed stratigraphic descriptions, standardized interpretations, and dating of relative sea-level indicators measured across ~700 km from the western and southern coasts of the Cape Provinces. Wave abrasion surfaces on bedrock, intertidal sedimentary structures, and in situ marine invertebrates including oysters and barnacles provide precise indicators of past sea levels. Multiple sea-level highstands imprinted at different elevations along South African coastlines were identified. Zone I sites average +32 ± 5 m (6 sites). A lower topographic Zone II of sea stands were measured at several sites around +17 ± 5 m. Middle and late Pleistocene sites are included in Zone III. Shoreline chronologies using 87Sr/86Sr ages on shells from these zones yield ages from Zone I at 4.6 and 3.0 Ma, and Zone II at 1.04 Ma. Our results show that polar ice sheets during the Plio-Pleistocene were dynamic and subject to significant melting under modestly warmer global temperatures. These processes occurred during a period when CO2 concentrations were comparable to our current and rapidly rising values above 400 ppmv.

Compound flooding, characterized by the co-occurrence of multiple flood mechanisms, is a major threat to coastlines across the globe. Tropical cyclones (TCs) are responsible for many compound floods due to their storm surge and intense rainfall. Previous efforts to quantify compound flood hazard have typically adopted statistical approaches that may be unable to fully capture spatio-temporal dynamics between rainfall-runoff and storm surge, which ultimately impact total water levels. In contrast, we pose a physics driven approach that utilizes a large set of realistic TC events and a simplified physical rainfall model and simulates each event within a hydrodynamic model framework. We apply our approach to investigate TC flooding in the Cape Fear River, NC. We find TC approach angle, forward speed, and intensity are relevant for compound flood potential, but rainfall rate and time lag between centroid of rainfall and peak storm tide are the strongest predictors of compounding magnitude. Neglecting rainfall underestimates 100-yr flood depths across 28% of the floodplain, and taking the max of each hazard modeled separately still underestimates 16% of the floodplain. We find the main stem of the river is surge-dominated, upstream portions of small streams and pluvial areas are rainfall-dominated, but midstream portions of streams are compounding zones, and areas close to the coastline are surge-dominated for lower return periods but compounding zones for high return periods (100-yrs). Our method links joint rainfall-surge occurrence to actual flood impacts and demonstrates how compound flooding is distributed across coastal catchments.

The world surrounding us is more over covered with plastics and we are in a “plastic era”. The bigger plastic materials, as the time moves, disintegrate into micro or nano particles may be as a result of radiations or weathering. These are termed as microplastics and nanoplastics. Technically these microparticles do not create a direct impact, instead they make their way to the food chain or rather a complex food chain. These can be through various steps ranging from filter feeding to adherence. They will start to accumulate, as the trophic level increases their accumulations also get increased. These trophic transfer is mainly through ingestion of smaller to higher organisms. Thus they create various damages and diseases to organisms in successive trophic levels. That can be ranging from respiratory disorders to endocrine or oncogenic issues. Not only in the marine world, the terrestrial world is also prone to these microplastics, either by airborne or through sewage water plants. Moreover in a developing or developed country, exposure to these tiny things are much more. The impacts are showing now and will entangle in the near future, unless this is not dealt as a serious issue to be considered. This article focuses on the classification, sources, exposure to food chain or food web, trophic concentrations, health issues, and remedies of microplastics.

A decade (2007-2016) of hourly 6 km resolution maps of the surface currents across the Mid Atlantic Bight (MAB) generated by a regional-scale High Frequency Radar network are used to reveal new insights into the spatial patterns of the annual and seasonal mean surface flows. Across the 10-year time series, temporal means, inter- and intra-annual variability are used to quantify the variability of spatial surface current patterns. The 10-year annual mean surface flows are weaker and mostly cross shelf near the coast, increasing in speed and rotating to more alongshore directions near the shelf break, and increasing in speed and rotating to flow off-shelf in the southern MAB. The annual mean surface current pattern is relatively stable year to year compared to the hourly variations within a year. The ten-year seasonal means exhibit similar current patterns, with winter and summer more cross-shore while spring and fall transitions are more alongshore. Fall and winter mean speeds are larger and correspond to when mean winds are stronger and cross-shore. Summer mean currents are weakest and correspond to a time when the mean wind opposes the alongshore flow. Again, intra-annual variability is much greater than interannual, with the fall season exhibiting the most interannual variability in the surface current patterns. The extreme fall seasons of 2009 and 2011 are related to extremes in the wind and river discharge events caused by different persistent synoptic meteorological conditions, resulting in more or less rapid fall transitions from stratified summer to well-mixed winter conditions.

Despite many studies on seafloor hydrothermal systems conducted to date, the generation mechanism of seafloor massive sulfide (SMS) deposits is not yet fully understood. To elucidate this mechanism, this study clarifies the three-dimensional regional temperature distribution and fluid flow of a seafloor hydrothermal system of the Iheya North, middle Okinawa Trough. Lateral flow and boiling of hydrothermal fluids below the seafloor were the main features found by the simulation, leading to an interpretation of two-layered SMS deposit generation as follows. Hydrothermal fluids discharging from black smokers first formed the upper SMS deposits on the seafloor. Caprocks formed below the seafloor, and the above-mentioned occurrences were then induced under the caprocks. In the present system, vapor-rich hydrothermal fluids poor in metals are discharged from the vents as white smokers, whereas liquid-dominated hydrothermal fluids rich in metals flow laterally below the caprocks, forming lower SMS deposits tens of meters below the seafloor.