1,720,978 research outputs found
Faunal activity rhythms influencing early community succession of an implanted whale carcass offshore Sagami Bay, Japan
No full textBenthic community succession patterns at whale falls have been previously established by means of punctual submersible and ROV observations. The contribution of faunal activity rhythms in response to internal tides and photoperiod cues to that community succession dynamism has never been evaluated. Here, we present results from a high-frequency monitoring experiment of an implanted sperm whale carcass in the continental slope (500 m depth) offshore Sagami Bay, Japan. The benthic community succession was monitored at a high frequency in a prolonged fashion (i.e. 2-h intervals for 2.5 months) with a seafloor lander equipped with a time-lapse video camera and an acoustic Doppler profiler to concomitantly study current flow dynamics. We reported here for the first time, to the best of our knowledge, the occurrence of strong 24-h day-night driven behavioral rhythms of the most abundant species (Simenchelys parasitica; Macrocheira kaempferi, and Pterothrissus gissu). Those rhythms were detected in detriment of tidally-controlled ones. Evidence of a diel temporal niche portioning between scavengers and predators avoiding co-occurrence at the carcass, is also provided. The high-frequency photographic and oceanographic data acquisition also helped to precisely discriminate the transition timing between the successional stages previously described for whale falls’ attendant communities. © 2018, The Author(s)
Tidal current energy resource assessment: The Strait of Messina test case
No full textIn this paper we present the assessment of tidal energy resource for the Strait of Messina. After considering both the constraints (geometric, site specific and operational) and the current potential of the area, the energy resource has been evaluated through the application of the method of energy flow and the method of farm. Four different converter devices have been considered: GEM, Kobold, MCT SeaGen and Verdant Power. Their performances have been compared assuming a theoretical common maximum power and considering the total amount of tidal energy produced in a number of potential selected locations. The GEM, Kobold and MCT SeaGen turbines reveal to be very competitive and effective. This analysis is particularly significant as at present, an extensive and accurate current assessment for the Italian seas is not yet available. © 2013 IEEE
Inertial bioluminescence rhythms at the Capo Passero (KM3NeT-Italia) site, Central Mediterranean Sea
No full textIn the deep sea, the sense of time is dependent on geophysical fluctuations, such as internal tides and atmospheric-related inertial currents, rather than day-night rhythms. Deep-sea neutrino telescopes instrumented with light detecting Photo-Multiplier Tubes (PMT) can be used to describe the synchronization of bioluminescent activity of abyssopelagic organisms with hydrodynamic cycles. PMT readings at 8 different depths (from 3069 to 3349 m) of the NEMO Phase 2 prototype, deployed offshore Capo Passero (Sicily) at the KM3NeT-Italia site, were used to characterize rhythmic bioluminescence patterns in June 2013, in response to water mass movements. We found a significant (p < 0.05) 20.5 h periodicity in the bioluminescence signal, corresponding to inertial fluctuations. Waveform and Fourier analyses of PMT data and tower orientation were carried out to identify phases (i.e. the timing of peaks) by subdividing time series on the length of detected inertial periodicity. A phase overlap between rhythms and cycles suggests a mechanical stimulation of bioluminescence, as organisms carried by currents collide with the telescope infrastructure, resulting in the emission of light. A bathymetric shift in PMT phases indicated that organisms travelled in discontinuous deep-sea undular vortices consisting of chains of inertially pulsating mesoscale cyclones/anticyclones, which to date remain poorly known. © 2017 The Author(s)
Uncertainty evaluation of CTD measurements: a metrological approach to water-column coastal parameters in the Gulf of La Spezia area
No full textThe ENEA Marine Environment Research Centre of S. Teresa has been involved since the ‘70s in monitoring, analysis and comprehension of physical, chemical and biological processes in marine environment. The purpose of this work is to describe the recently-implemented metrological approach aimed at evaluating the uncertainty associated with measurements performed by a Conductivity-Temperature-Depth profiler (CTD) during routine coastal campaigns in the Eastern Ligurian Sea, close to the Gulf of La Spezia. Main effort of this work is focused on applying, to each involved parameter, the standard framework for uncertainty evaluation as prescribed by the Guide to the expression of uncertainty in measurement. To this aim, an appropriate uncertainty evaluation is performed by combining type A and B contributions, evaluated from experimental data obtained in reproducibility conditions and from calibration certificates periodically supplied by manufacturer, respectively. Concerning in situ measured practical salinity, probability density functions modelling water pressure, temperature and conductivity, from which salinity depends, are propagated by application of the Monte Carlo method for propagation of distributions, hence obtaining the salinity uncertainty. © 2018 Elsevier Lt
Using SeaDataNet management system to preserve the XBT data-set of the Mediterranean Sea
No full textA significant amount of Expendable Bathythermograph (XBT) data has been collected in the Mediterranean Sea since 1999 in the framework of operational oceanography activities. The management and storage of such a volume of data poses significant challenges and opportunities. The SeaDataNet project, a pan-European infrastructure for marine data diffusion, provides a convenient way to avoid dispersion of these temperature vertical profiles and to facilitate access to a wider public. The XBT data flow, along with the recent improvements in the quality check procedures and the consistence of the available historical data set are described. The main features of SeaDataNet services and the advantage of using this system for long-term data archiving are presented. Finally, focus on the Ligurian Sea is included in order to provide an example of the kind of information and final products devoted to different users can be easily derived from the SeaDataNet web portal. © 2015 IEEE
A Medium-Resolution Wave Hindcast Study Over the Central and Western Mediterranean Sea
No full textThe present study is aimed at determining the confidence limits of design wave parameters derived from numerical modeling - for both extremes and operational conditions - over the Central and Western Mediterranean Sea. The paper presents the methodology and results of an extensive validation activity conducted on a chain of medium resolution third generation wave models used for hindcast purposes. The stringent requirements of state-of-art coastal and offshore engineering applications over this area make the adoption of medium or high resolutions hindcast wave and wind models almost mandatory because of the complex coastal geometry, bathymetry and orography that in turn lead to large variations of the design wave parameters even within small regions. The chains of nested meteorological and wave models used in this hindcast study belong to the ETA and WaveWatch III families respectively.
In this study the wind and wave numerical models have been run over the past 20 years, with increasing resolutions of the wave models from 0.2° up to 0.04°. The results here presented have a 0.1° resolution for both wind and wave models. The wave data obtained are compared with available measurements from 14 wave buoys in coastal zones in the Central and Western Mediterranean Sea
The Tyrrhenian Intermediate Water (TIW): Characterization and formation mechanisms
No full textThis work focuses on the Tyrrhenian Intermediate Water, a water mass present in the Tyrrhenian Sea (Western Mediterranean Sea), which approximately lies between 100 m and 200 m of depth, and is characterized by a local minimum of temperature. Here, for the first time, a thorough investigation of the Tyrrhenian Intermediate Water has been performed, based on the analysis of long time series of observations (XBT, Argo float, dissolved oxygen data) and on modeling results. It was found that this water is present in a large part of the Tyrrhenian basin, and is a persistent feature of the basin hydrology. It is formed by winter convection, with some differences between the southern part of the basin and the northern part, where strong winter cooling produces deeper convection and mixing. The process of formation of the Tyrrhenian Intermediate Water has been investigated in detail, through the analysis of the experimental datasets, of dedicated numerical experiments with a one-dimensional mixed layer model, and of the outputs of a three-dimensional ocean circulation model. Such analysis has excluded remote contributions from intermediate waters produced in the western portion of the Western Mediterranean basin. On the other hand, the presence of the Tyrrhenian Intermediate Water has been found to impact not only the Tyrrhenian Sea hydrology, but also that of the adjacent Liguro-Provençal basin, because this water mass outflows from the Corsica Strait, and is transported as far as the Gulf of Lion, in the core of the region where deep waters are formed. Recent changes in the properties of this intermediate water mass have also been highlighted, which result from the warming of the neighboring water layers. © 2018 Elsevier Lt
Use of ADCP acoustic backscatter to estimate seawater total suspended solids in continuous along a transect. Test case in a near shore area (Ligurian Sea, La Spezia Gulf)
Full text linkAcoustic Doppler Current Profilers (ADCPs), as a secondary output, allow to estimate the concentration of Total Suspended Solids (TSS) in the water column through the analysis of the acoustic backscatter signal. This method was applied during a dedicated ENEA campaign in a near-shore area of the Gulf of La Spezia. ADCP measurements were performed throughout the cruise and joint measurements of TSS (discretely sampled) and Turbidity (by nephelometer) were performed along the water column in one station. The application of the simplified sonar equation made possible to calibrate the ADCP vs TSS by means of a linear regression model, whose correlation coefficient resulted reasonably good (R2 was in fact equal to 0.87), with slope Kc = (0.239 ± 0.008) dB count-1 and intercept Ck = (-69.88 ± 0.59) dB, respectively. The method, whose reliability was proved by comparison with an independent TSS profile, was then applied to obtain a continuous quasi-synoptic mapping of TSS values along the water column throughout the cruise. The overall uncertainty budget of the method was estimated, too: the relative combined standard uncertainty resulted to be less than 30% for TSS values higher than about 3 mg l- 1. The method, although not completely exhaustive due to the multiplicity and unpredictability of the conditions (above all, the type and size and actual distribution of scattering particles), is to be considered valid for a quick acquisition of local situations, allowing to obtain fast and almost zero cost TSS mappings. Results prove that this consolidated approach can be applied in the near-shore area, where ENEA performs its monitoring campaigns and where the interest in TSS measures is also motivated by the presence of fish and mussel farms, the transit of container ships and the proximity of the estuary of the Magra river. The present technical report is intended to serve as a basis for developing procedures more and more compliant to international metrological standards, with the aim of further guaranteeing the metrological traceability of oceanographic quantities
Uncertainty evaluation of CTD measurements: a metrological approach to water-column coastal parameters in the Gulf of La Spezia area
Full text linkThe ENEA Marine Environment Research Centre of S. Teresa has been involved since the ‘70s in monitoring, analysis and comprehension of physical, chemical and biological processes in marine environment. The purpose of this work is to describe the recently-implemented metrological approach aimed at evaluating the uncertainty associated with measurements performed by a Conductivity-Temperature-Depth profiler (CTD) during routine coastal campaigns in the Eastern Ligurian Sea, close to the Gulf of La Spezia. Main effort of this work is focused on applying, to each involved parameter, the standard framework for uncertainty evaluation as prescribed by the Guide to the expression of uncertainty in measurement. To this aim, an appropriate uncertainty evaluation is performed by combining type A and B contributions, evaluated from experimental data obtained in reproducibility conditions and from calibration certificates periodically supplied by manufacturer, respectively. Concerning in situ measured practical salinity, probability density functions modelling water pressure, temperature and conductivity, from which salinity depends, are propagated by application of the Monte Carlo method for propagation of distributions, hence obtaining the salinity uncertainty
New Insights into Tyrrhenian Sea Warming and Heat Penetration through Long-Term Expendable Bathythermograph Data
Full text linkThe warming trend of the Mediterranean region is already well known, but there is still a lack of information on its seasonal/annual to multidecadal time scales and its distribution in all water masses, including deep water. New temporal and spatial evidence of this thermal variability has been presented in the Tyrrhenian Sea, thanks to twenty-year continuous monitoring by eXpendable BathyThermographs (XBTs) along a fixed route from Genoa to Palermo. The Tyrrhenian Sea is one of the deepest Mediterranean sub-basins (with a maximum depth of about 4000 m), but its interaction with neighbouring basins is controlled by topographical factors, such as the Sardinian Channel to the south and the Corsican Channel to the north. The way in which the warm signal, originating from the Levantine sub-basin, and entering from the south, affects the entire Tyrrhenian Basin spreading rapidly northwards is studied, considering its peculiarities, such as topography, surface circulation, and strong stratification, as well as its climate variability. The warming trend observed for the Tyrrhenian Sea is consistent with the trend for the Mediterranean Sea as a whole. However, the Tyrrhenian Sea shows some peculiar features: around 2014, a shift to a new equilibrium (warmer) state was detected, with mean values along the monitored route that were significantly higher than the previous period (from 1999 to 2013), especially for the subsurface level, from 100 to 450 m depth
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