1,720,988 research outputs found
Indication of recent warming process at the intermediate level in the tyrrhenian sea from SOOP XBT measurements
No full textThe Tyrrhenian Sea is a sub-basin of the western Mediterranean crossed by intermediate and deep waters from the eastern basin. Across this sub-basin, temperature profiles of the water column from expendable bathythermographs (XBTs) have been acquired for fifteen years along transects realized by means of commercial vessels. Since 1999 two increases of temperature have been observed at intermediate depths interspersed with "colder" periods. These increases concern deeper and deeper depths over the course of the years, then involving the entire sub-basin in the 200-800 m range in September 2014, when the greatest anomalies over the entire period are found. The paper shows evidences of this rapid warming, giving insights into the origin and the diffusion of the warmer intermediate waters, then showing its evolution in the years
A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change
No full textThe evolution of ocean temperature measurement systems is presented with a focus on the development and accuracy of two critical devices in use today (expendable bathythermographs and conductivity-temperature-depth instruments used on Argo floats). A detailed discussion of the accuracy of these devices and a projection of the future of ocean temperature measurements are provided. The accuracy of ocean temperature measurements is discussed in detail in the context of ocean heat content, Earth's energy imbalance, and thermosteric sea level rise. Up-to-date estimates are provided for these three important quantities. The total energy imbalance at the top of atmosphere is best assessed by taking an inventory of changes in energy storage. The main storage is in the ocean, the latest values of which are presented. Furthermore, despite differences in measurement methods and analysis techniques, multiple studies show that there has been a multidecadal increase in the heat content of both the upper and deep ocean regions, which reflects the impact of anthropogenic warming. With respect to sea level rise, mutually reinforcing information from tide gauges and radar altimetry shows that presently, sea level is rising at approximately 3 mm yr-1 with contributions from both thermal expansion and mass accumulation from ice melt. The latest data for thermal expansion sea level rise are included here and analyzed. Key Points Oceanographic techniques and analysis have improved over many decadesThese improvements allow more accurate Earth-energy balance estimatesUnderstanding of ocean heat content and sea-level rise has also increased ©2013. American Geophysical Union. All Rights Reserved
Modeling and numerical simulation of the forces acting on a sphere during early-water entry
No full textMathematical modeling, absent simplifying assumptions and coupled with numerical simulation, has been implemented to determine the motions and forces experienced by a sphere penetrating a water surface from an air space above the surface. The model and simulation are validated by comparisons with extensive experimental data and with trends from approximate analyses. Although the present work adds to the understanding and quantification of the sphere as an entry object, its major contribution is model development and validation to enable investigation of water entry of objects of practical utility such as the expendable bathythermograph (XBT). The XBT device is widely used in the determination of temperature distributions in large water bodies such as oceans. The measured temperature distributions are, in turn, used to determine the thermal energy content of oceans. During the course of the numerical simulations, parametric variations were made of the sphere velocity, surface tension, flow regime (laminar or turbulent), and Reynolds number. The drag-coefficient results were found to be independent of these quantities. This outcome indicates that momentum transfer from the sphere to the adjacent liquid is responsible for the drag force and that friction is a secondary issue. © 2013 Elsevier Ltd
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
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
Reprocessing of eXpendable BathyThermograph (XBT) profiles from the Ligurian and Tyrrhenian seas over the time period 1999–2019 with a full metadata upgrade
Full text linkThe advent of open science and the United Nations Decade of Ocean Science for Sustainable Development are revolutionizing the ocean-data-sharing landscape for an efficient and transparent ocean information and knowledge generation. This blue revolution raised awareness on the importance of metadata and community standards to activate interoperability of the digital assets (data and services) and guarantee that data-driven science preserves provenance, lineage and quality information for its replicability. Historical data are frequently not compliant with these criteria, lacking metadata information that was not retained, crucial at the time of data generation and further ingestion into marine data infrastructures. The present data review is an example attempt to fill this gap through a thorough data reprocessing starting from the original raw data and operational log sheets. The data gathered using XBT (eXpendable BathyThermograph) probes during several monitoring activities in the Tyrrhenian and Ligurian seas between 1999 and 2019 have first been formatted and standardized according to the latest community best practices and all available metadata have been inserted, including calibration information never applied, uncertainty specification and bias correction from Cheng et al. (2014). Secondly, a new automatic quality control (QC) procedure has been developed and a new interpolation scheme applied. The reprocessed (REP) dataset has been compared to the data version, presently available from the SeaDataNet (SDN) data access portal, processed according to the pioneering work of Manzella et al. (2003) conducted in the framework of the European Union Mediterranean Forecasting System Pilot Project (Pinardi et al., 2003). The comparison between REP and SDN datasets has the objective to highlight the main differences derived from the new data processing process. The maximum discrepancy among the REP and SDN data versions always resides within the surface layer (REP profiles are warmer than SDN ones) until 150 m depth generally when the thermocline settles (from June to November). The overall bias and root mean square difference are equal to 0.002 and 0.041 °C, respectively. Such differences are mainly due to the new interpolation technique (Barker and McDougall, 2020) and the application of the calibration correction in the REP dataset. The REP dataset (Reseghetti et al., 2024; https://doi.org/10.13127/rep_xbt_1999_2019.2) is available and accessible through the INGV (Istituto Nazionale di Geofisica e Vulcanologia, Bologna) ERDDAP (Environmental Research Division’s Data Access Program) server, which allows for machine-to-machine data access in compliance with the FAIR (findable, accessible, interoperable and reusable) principles (Wilkinson et al., 2016)
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
ARGO floats vs. Ship-based CTDs: An overall metrological comparison in the whole Mediterranean Sea
No full textThe widespread network of temperature/salinity profiling floats, known as Argo, has nowadays become a fundamental component of the ocean observing system. Since Argo floats usually are not recovered and should last up to five years without any re-calibration, their onboard sensors can reasonably suffer some drift and/or offset. During the years, very refined methods have been developed and implemented to post-process the Argo data, in order to correct the response of their profiling CTD (Conductivity - Temperature - Depth) sensors, in particular adjusting the salinity drift. The core of this delayed-mode quality control is the comparison of Argo data with reference climatology. At the same time, it's still considered metrologically fundamental the experimental comparison of Argo profiles with quasi-collocated in space and quasi-simultaneous in time ship-based CTD profiles. In this paper an overall comparison of Argo floats vs. shipboard CTDs was made, in terms of temperature and salinity profiles in the whole Mediterranean Sea and under strict space-time matching conditions
COMPARISON BETWEEN XBT DATA AND TOPEX/POSEIDON SATELLITE ALTIMETRY IN THE LIGURIAN-TYRRHENIAN AREA
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