In closed sea areas in the world the eutrophication is being progressed day by day. Nowadays in closed sea areas in Japan it is hard to control the seawater quality in deep areas because of the poor oxygen seawater or the anoxic seawater. Aerobic microorganisms can contribute to decompose organic compounds in the seawater as long as they live to consume oxygen. As a result the oxygen decreases in deep areas. It is necessary to maintain that the seawater is clean and rich in nature for the sustainable development. One of methods is this sustainable seawater purification system built in quays and piles using purifying functions of microorganisms and the tidal energy (Dan et al. 2017). It is shown that this system can decrease Chemical Oxygen Demand (CODMn) in the seawater experimentally and can be utilized in order to purify the seawater from the depth to the shallows using this system built in piles partially around a pile and using this system built in quays widely along a quay. This system has following advantages. 1.Using the tidal energy –> “ecosystem” 2.Using the purifying functions of microorganisms, decomposing organic materials –> “ecological and natural without chemicals”, 3.Capable of purifying the seawater in the shallow area, especially also in the deep area –> “useful” in closed sea areas 4.This system built in piles or quays is simple. Not to construct new quays but to construct the purifying room additionally. It costs less. –> “economical” The initial CODMn is almost 8 by putting sugar adequately in seawater and mixing (Fig. 9 and 10). The changing process of CODMn is checked by measuring CODMn according to JIS K 0102 (Japanese industrial Standards). In the case of seawater purification system CODMn is becoming smaller and it is found that this system can reduce CODMn in seawater. In future in order to construct this system built in piles or in quays in the field following procedure is considered, 　①When the field site to construct this system is selected and the tidal range z is given. 　②Because the velocity v in the vessel through gravels is sufficiently small for microorganisms to decompose organic compounds then v

Regional numerical modeling provides a valuable means to assess important aspects of natural systems when the cost and effort of direct observation is impractical; the Arctic Ocean and its marginal seas and archipelagos represent a domain where such applications abound. We describe the configuration of and results from a set of coupled sea-ice ocean circulation models that are based on the Regional Ocean Modeling System (ROMS). Challenging features include large fresh water fluxes from the major Arctic rivers, seasonal land-fast ice, and ice-covered open boundary conditions in nested models. A broad-scale domain, dubbed the Pan-Arctic ROMS (PAROMS) model, extends from the Aleutian Islands to southern Greenland using a telescoping horizontal grid spacing that varies from 4 km in the Pacific to 8 km in the Atlantic. Higher-resolution domains include nested grids at 3 km and 500 m grid spacing. Coastal discharges are prescribed as lateral inflows distributed over the depth of the ocean-land interface. The model includes tides, sea ice, updated bathymetry, and atmospheric forcing from the MERRA reanalysis. We assess the model’s performance with respect to tides, storm surges, wind-driven circulation, and thermohaline fields. A hindcast integrated over 1983-2015 provides a means to assess synoptic, seasonal and inter-annual variability. Applications include investigations of shelf flow field pathways, residence times and advective timescales, and energetics balances.

The North Brazil Current transport displays a pronounced multidecadal variability with about a 7 Sv peak-to-peak amplitude. Although it has been suggested that this variability is related to that of the Atlantic Meridional Overturning Circulation, its origin is still unknown. Here we present results of an analysis of model data from a long (200 years) simulation of a high-resolution (0.1 horizontally) version of the Parallel Ocean Program that indicates a connection between multidecadal variability in the Southern Ocean, due to the so-called Southern Ocean Mode, and multidecadal variability in the North Brazil Current. The interaction of the large-scale ocean circulation and eddies is crucial for the existence of the Southern Ocean Mode. We present the mechanisms of this teleconnection in detail, which involves the vertical displacement of isopycnals, generation of Rossby waves and meridional propagation of sea surface height and ocean heat content anomalies. In addition, we show that the same mechanism connecting Southern Ocean and North Brazil Current multidecadal variability is also found in a (200 years) simulation of a high-resolution global version of the Community Earth System Model, with the same horizontal ocean resolution of 0.1. The results provide a new mechanism for the multidecadal variability of the North Brazil Current.

The biodiversity of reef fish in the Florida Keys National Marine Sanctuary was evaluated in terms of abundance, biomass, evenness, species richness, Shannon diversity, Simpson diversity, and functional diversity, using observations collected from 1999 – 2016 by the Reef Visual Census program. To compare the different diversity indices, species richness, Shannon diversity, Simpson diversity, and functional diversity were converted into effective number of species. We examined the seven indices by level of protection and type of no-take marine zones and by three habitat strata. The study detected abundance, biomass, and diversity were significantly greater (except evenness) inside no-take marine zones compared to areas open to fishing. Smaller reserves had higher abundance, biomass, and richness values than larger reserves and areas open to fishing, but had moderately higher diversity values. This may be attributed to a few species with many individuals that are dominant inside and outside no-take marine zones. Surprisingly, none of the indices were significantly different (except for functional diversity) between the larger Ecological Reserve and areas open for consumption. This may be due to spillover effects. Furthermore, the no-take marine zones only explained a small proportion of total percent deviance in the indices. Habitat type had a greater influence on patterns in composition and diversity where high relief reef habitats had the greatest abundance, biomass, and diversity indices. Based on our results managers should prioritize preserving high relief reefs through a network of small reserves to enhance reef fish composition and biodiversity.

While waves propagating over a uniform current are simply subject to a Doppler shift of their phase, inhomogeneous flows can modify the wavenumber, direction, and amplitude of the waves, having the potential to largely modulate the surface wave field. Even though the theoretical basis for such interactions is well established, comprehensive observations and modeling of wave–current interactions are mostly limited to either tidal or large–scale currents and a lot remains unknown about how waves and currents interact when both fields are highly variable, such as near ocean fronts and eddies. In the present work, the extent to which the surface wave field off the California coast is modulated by the California Current System is investigated. Optimized currents and winds from a state estimate of the California Current System are used to force the wave model WaveWatch III in order to quantify the relative importance of local winds and currents in modulating the surface wave variability in this region. As satellite altimeters evolve towards resolving finer scales, knowing the wave field with precision may help the interpretation of sea surface height measurements at high wavenumbers and frequencies, which has particular relevance for the planning of the Surface Water and Ocean Topography (SWOT) mission.

We present a data-derived, ecosystem mapping approach for the global ocean as commissioned by the Group on Earth Observations (GEO) and as a contribution to the Marine Biodiversity Observation Network (MBON). These ecological marine units (EMUs) are comprised of a global point mesh framework, created from over 52 million points from NOAA’s World Ocean Atlas with a spatial resolution of 1 by 1 degree (∼27 x 27 km at the equator) at 44 varying depths and a temporal resolution that is currently decadal. Each point carries attributes of chemical and physical oceanographic structure (temperature, salinity, dissolved oxygen, nitrate, silicate, phosphate) as likely drivers of many marine ecosystem responses. We used a k-means statistical clustering algorithm to identify physically distinct, relatively homogenous, volumetric regions within the water column (the EMUs). Backwards stepwise discriminant analysis determined if all of six variables contributed significantly to the clustering, and a pseudo F-statistic gave us an optimum number of clusters worldwide at 37. A major intent of the EMUs is to support marine biodiversity conservation assessments, economic valuation studies of marine ecosystem goods and services, and studies of ocean acidification and other impacts. As such, they represent a rich geospatial accounting framework for these types of studies, as well as for scientific research on species distributions. To further benefit the community and facilitate collaborate knowledge building, data products are shared openly and interoperably via www.esri.com/ecological-marine-units. This includes provision of 3D point mesh and EMU clusters at the surface, bottom, and within the water column in varying formats via download, web services or web apps, as well as generic algorithms and GIS workflows that scale from global to regional and local. Work is in progress to delineate EMUs at finer spatial and temporal resolutions and to include ocean currents and various biodiversity observations. A major aim is for the ocean science community members to move the research forward with higher-resolution data from their own field studies or areas of interest, with the original EMU project team assisting with GIS implementation (especially via a new online discussion forum), and hosting of additional data products as needed.

Marine aggregates are ubiquitous particles formed from the accretion of smaller biogenic and non-biogenic components. Visible aggregates, known as marine snow, are typically in the 0.5 to few mm size range. Aggregates are well recognised as hotspot of microbial and planktonic activities. Aggregates formation is an important pathway for transferring materials and carbon flux from surface to the deep ocean. Because aggregate sinking velocity and carbon mass content is size dependent, understanding the physical mechanism controlling aggregate size distribution is fundamental to determining the biological carbon pump efficiency. Turbulence is a physical mechanism in the aggregates formation and destruction. However, the relative roles of turbulence in aggregates formation and destruction have not been fully tested in observational studies. In this study, we analysed simultaneous in-situ observations of turbulence and aggregate in the various aquatic systems. A microstructure profiler, TurboMAP-L, was used to collect shear data and a digital still logger camera was used to collect images of aggregates. Digital images were subsequently used to determine aggregates abundances and size distributions. Direct comparison of turbulence intensity and aggregate size distributions show that turbulence below 𝜀=10-6[W/kg] enhances aggregation, increasing average particle size; greater turbulence causes particle breakup, limiting the average maximum aggregate size and decreasing the slopes of size distributions. This indicates the role of turbulence controlling aggregate size distributions. We also present fluorescence data collected by TurboMAP-L and focus on difference of aggregates size distributions among different aquatic systems.

Water sample collection is a simple, but fundamental approach for measuring water properties that cannot currently be sensed in situ with instruments or for conducting experiments requiring water samples. Conventional approaches to water sampling typically employ research vessels which are costly, limited by sea state, and are often restricted by scheduling and other logistics. These factors can limit the ability to sample transient phenomena in inland and coastal waters. They can also restrict sampling frequency for time series measurements. We describe the use of aerial drones and newly developed sampling bottles that allow sub-surface water collection without the use of research vessels. The sampling bottles are similar in operation to conventional Niskin bottles, but with the different methods for closing the bottles. We have experimented with two closing methods. One uses a float and mechanical linkage to close bottles at fixed depths and the other uses pressure sensors to close bottles at programmed depths. Drone-based water sampling is currently employed in the Santa Barbara Coastal Long Term Ecological Research (SBC LTER) project to obtain weekly time series of water samples for pH and total alkalinity at a long-term oceanographic mooring. The water samples are also being used to calibrate pH sensors on the mooring and assess data quality. Drone sampling will be expanded to other SBC LTER moorings in the future. Aerial drones offer a new approach for sampling the coastal ocean and inland waters. Drone-based sampling is in its infancy, but we envision the development of a suite of specialized instrumentation and water collection devices that take advantage of the capabilities of aerial drones. This will allow rapid response for sampling transient events such as harmful algal blooms and toxic spills in a wide range of environmental conditions.

Recent observations of warming trends in the Red Sea raise more attention to the response of the basin under a warming climate. Using two remotely sensed datasets, the Hadley Centre Sea Ice and Sea Surface Temperature [HadISST] and Extended Reconstructed Sea Surface Temperature [ERSST.v3], we investigate the reported sudden increase in the Red Sea sea surface temperatures (SST) in terms of average and maximum and assess their relation to multi-decadal climate variability. Prior to the analysis, the two datasets are successfully validated with respect to their ability to reproduce the recent observed and reported trends and their spatial features. Analysis of long-term SST variability revealed a sequence of alternating and similar in amplitude positive and negative trends, characterized by a period of nearly 70 years. Similar oscillations have been reported in other basins and have been related to atmospheric disturbances associated with the Atlantic Multidecadal Oscillation (AMO). A point-by-point spectral analysis of SST evolution shows a significant correlation with the basic modes of the AMO that explains a large fraction of its temporal and spatial variability. Projections on the major modes of the spectral analysis suggest a possible decreasing effect on local SST in the near future. Under this assumption, recent projected trends in the Red Sea may be exaggerated, whilst trends that may be related to anthropogenic influence could be masked by the projected negative influence of the AMO in the near future.

The Inter-Tropical Convergence Zone (ITCZ) is a persistent band of organized convection in the tropics that arises due to the surface convergence of the Hadley cells. The location and intensity of the ITCZ is heavily influenced by sea surface temperature and low-level latent heat transport. The ITCZ undergoes an annual march across the equator, and during the summer moves north over India and the Bay of Bengal, affecting the Indian summer monsoon. Occasionally a second parallel band of convection forms to the south, referred to as a double-ITCZ. Double-ITCZs in the tropical east Pacific have been heavily studied, and their development is understood to be linked to seasonal changes in sea-surface temperature. The existence of double ITCZs over the tropical Indian Ocean is well documented, but the underlying mechanism is poorly understood. We develop an algorithm to identify this phenomenon in NOAA outgoing longwave radiation data, and create a thirty-year record of double-ITCZ occurrence. We then use this record to investigate linkages between summer-time double-ITCZ occurrence and intra-seasonal variability in the Indian summer monsoon, and discuss possible physical mechanisms.

Natural methane gas release from the seafloor is a widespread phenomenon that occurs at cold seeps along most continental margins. Since their discovery in the early 1980s, seeps have been the focus of intensive research, partly aimed to refine the global carbon budget. However, deep-sea research is challenging and expensive and, to date, few works have successfully monitored the variability of methane gas release over long time periods (> 1 yr). Long-term monitoring is necessary to study the mechanisms that control seabed gas release. The M³ project, funded by the German Ministry of Education and Research, aims to study the temporal and spatial variability of gas emissions at the Southern Hydrate Ridge (SHR) by acoustically monitoring and quantifying gas effluxes over several years. Located 850 m deep on the Cascadia accretionary prism offshore Oregon, the SHR is one of the most studied seep sites and persistent but variable gas release has been observed for more than 20 years. Since 2015, the Ocean Observatories Initiative’s (OOI) Cabled Array observatory, provides power supply and two-way communication to the SHR, making it an ideal site for continuous long-term monitoring work. In this work, we present how we will take advantage of the OOI infrastructure and deploy several instruments on the seabed for at least 1.5 year. A multi-beam “overview” sonar mounted on a rotor will identify every gas bubble stream located within 200 m from the sonar location. A scanning “quantification” sonar will be used to estimate the amount of gas that is released from discrete gas streams. A camera system and a CTD probe will help process and analyze the hydro-acoustic data. All instruments will be powered and controlled from land through the OOI infrastructure. We present the instrument design, the operation protocol, as well as the data processing steps and expected results.

High performance liquid chromatography (HPLC) remains one of the most widely applied methods currently available for estimation of phytoplankton taxonomy from ocean samples. This method measures the concentrations of phytoplankton pigments, some of which are useful chemotaxonomic markers that can be used to diagnose the relative abundance of phytoplankton groups. Here, we use HPLC phytoplankton pigment concentrations measured on surface water samples from 38 field surveys for a total of over 3,000 distinct samples that cover every major ocean basin and represent a wide range of ecological regimes. The data compilation has been quality controlled to remove measurements below pigment detection limits and outliers from the linear regression of total chlorophyll-a concentration with total accessory pigment concentrations and only samples from labs that have participated in round-robin quality assurance experiments (e.g. NASA SeaHARRE) have been included. We assess the environmental and spatial drivers controlling the global distribution and co-variability of individual phytoplankton pigments. Preliminary results of hierarchical clustering show strong differentiation in phytoplankton pigments following known relationships between phytoplankton size class and relative pigment concentration, partitioning their contributions by micro-, nano-, and pico-phytoplankton size classes. However, the exact clusters relationships change when the data are divided by ocean basin or latitude. We also use statistical techniques, including EOFs and network-based exploration, to examine the associations between groups of pigments over a range of environmental conditions on local to global scales and diagnose the main controls on these associations.

The Reykjanes Ridge is a major topographic feature that lies south of Iceland in the North- Atlantic Ocean and strongly influences the Subpolar Gyre (SPG) circulation. Based on velocity and hydrographic measurements carried out along the crest of the Ridge from the Icelandic continental shelf to 50°N during the RREX cruise in June-July 2015, we derived the first direct estimates of volume and water masses transports over the Ridge. The circulation was mainly westward north of 53.35°N and eastward south of it. The westward transport was estimated at 21.9 ± 2.5 Sv (Sv = 10 6 m 3 s -1 ) and represents the SPG intensity. The westward flows followed two main pathways at 57°N near Bight Fracture Zone and at 59 – 62°N. We argue that those pathways were respectively connected to the northern branch of the North Atlantic Current and to the Sub-Arctic Front that were intersected by the southern part of the section. In addition to this horizontal circulation, mixing and bathymetry shaped the water mass distribution. Water mass transformations in the Iceland Basin lead to the formation of weakly stratified SubPolar Mode Water (SPMW). We explain why SPMW, which was the main contributor in terms of water mass to the westward flow, was denser at 57°N than at 59–62°N along the Ridge. At higher densities, both Intermediate Water, defined by a dissolved oxygen minimum, and Icelandic Slope Water contributed as much to the westward transport across the Ridge as the sum of Labrador Sea Water and Iceland-Scotland Overflow Water.

Increasing CO2 in the ocean leads to warming, reduced pH (ocean acidification), and lower oxygen content in deeper ocean waters. Warming, ocean acidification, and hypoxia in deep ocean waters can have important consequences for nearshore marine ecosystems especially for regions with seasonal upwelling such as the California Current. In these regions, seasonal upwelling combined with internal waves brings low pH, low oxygen waters into nearshore reefs where animals are exposed to intermittent stressful conditions. We compared exposure between present-day and future climate scenarios (RCP85) using ROMS coupled with a biogeochemical model.

A Bayesian data assimilation scheme is formulated for advection-dominated or hyperbolic evolutionary problems, and observations. It uses the physics to dynamically update the likelihood in order to extend the impact of the likelihood on the posterior, a strategy that would be particularly useful when the the observation network is sparse in space and time and the associated measurement uncertainties are low. The filter is applied to a problem with linear dynamics and Gaussian statistics, and compared to the exact estimate, a model outcome, and the Kalman filter estimate. By comparing to the exact estimate the dynamic likelihood filter is shown to be superior to model outcomes and to the Kalman estimate, when the observation system is sparse. The added computational expense of the method is linear in the number of observations and thus computationally efficient, suggesting that the method is practical even if the space dimensions of the physical problem are large.

During the Norwegian young sea ICE (N-ICE2015) campaign, which took place in the first half of 2015 north of Svalbard, a deep winter snow pack (50 cm) on sea ice was observed, that was 50% thicker than earlier climatological studies suggested for this region. Moreover, a significant fraction of snow contributed to the total ice mass in second-year ice (SYI) (9% snow by mass), while very little snow was present in first-year ice (FYI) (3% snow by mass). We use a 1-D snow/ice thermodynamic model forced with reanalyses data in autumn and winter 2014/15. We show that snow-ice would form on SYI even with an initial ice thickness of 2 m in autumn. By the end of winter snow-ice can contribute up to 24-44% of the total thickness of SYI, if the ice is thin in autumn (0.6 m). This is important, especially in the absence of any bottom thermodynamic growth due to the thick insulating snow cover. We also show that growth of FYI north of Svalbard is controlled by the timing of growth onset relative to snow precipitation events and cold spells. These usually short-lived conditions are largely determined by the frequency of storms entering the Arctic from the Atlantic Ocean. In our case, a later freeze onset was favorable for FYI growth, due to less snow accumulation in early autumn. This limits snow accumulation on FYI but promotes bottom thermodynamic growth. We show our findings are related to regionally higher precipitation in the Atlantic sector of the Arctic, where frequent storms bring lot of precipitation in autumn and winter, and also affect the duration of cold temperatures required for ice growth in winter. We discuss the implications and the importance of snow-ice in the future Arctic, formerly believed to be non-existent in the central Arctic, due to thick perennial ice and little snow precipitation. The combination of sea ice thinning and high precipitation in the “Transpolar Drift region” highlights the need to understand the regionality of these processes across the Arctic.

Spreading and transport of the Maximum Salinity Core Layer (MSCL), defined as water with salinity higher than 36 psu, is investigated from hydrographic data sets collected along twelve cross-sections by the Sea education Association (SEA) between Tahiti and the equator from 2008 and 2015, the ARGO data objectively mapped from JAMSTEC and satellite remote sensing. Aquarius sea surface salinity data show that the MSCL occupied an area averaged over time of about 6.7 106 km² with an increase of the occupancy in 2015. The variation of the area occupied by the MSCL at the surface does not show any seasonal cycle. Hydrographic dataset are used to show the extent of the MSCL below the surface. The SEA dataset exhibits the spreading of the MSCL northward of Tahiti between isopycnals 24 σt and 25 σt and is observed as far north as 4°S. The MSCL is observed at the surface as far north as 12°S and the disappearance of the MSCL from the surface is due to input of fresher water from the equatorial region or from the west. Even tough ARGO data have a poorer vertical resolution, comparison with SEA dataset shows that the core of the MSCL is well determined. But ARGO data has a better time resolution and monthly data are available from 2001 to 2017. ARGO data allow us to visualize the whole volume of the MSCL and the westward extension of the MSCL. Geostrophic currents are calculated from ARGO data relative to the surface where surface currents are adjusted to velocities provided by the satellite derived OSCAR data set. The transport calculation shows that most of the water north of Tahiti is transported westward with the highest volume during an El Niño year.

Particle sinking velocity is an important determinant of carbon transport and sequestration to the deep-sea. It is however technically challenging to measure in situ particle sinking velocities. Recently, methods based on the radioactive pairs, (234Th-238U and 210Po-210Pb) were developed to estimate average sinking velocity (ASV), along the classical carbon export flux estimates. The influence of ASVs on key metrics of the biological carbon pump such as (i) the particle export efficiency (defined as the proportion of PP being exported below the surface ocean) (ii) carbon export fluxes and attenuation, still remain uncertain and need to be further evaluated. ASVs are calculated in five biogeochemically contrasting sites: high latitude (Irminger Basin; Scotia Sea), temperate (PAP site) and oligotrophic (BATS, Equator) North Atlantic. ASVs are also calculated for different bloom stages (bloom - post bloom) in the North Atlantic and at the start of the bloom in two contrasting sites in the Southern Ocean (Scotia Sea). A systematic increase of ASVs with depth, inversely correlated to carbon flux attenuation, is detected. We assess whether the increase in ASV with depth is correlated with either temperature or community structure (phytoplankton and/or zooplankton). Evidences of ASV correlation with carbon export efficiency are detected, but they vary strongly with season and location, e.g. very distinct relationships are found for the results from Scotia Sea, likely driven by zooplankton abundance.