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Giovanni Bortoluzzi, Federico Giglio, Marco Ligi, Fabrizio Del Bianco, Valentina Ferrante, Luca Gasperini, Mariangela Ravaioli
The seafloor geomorphology of Boka Kotorska Bay

One of the most intriguing feature along the entire Adriatic coast is the bay of Boka Kotorska, where the sea enters inland for over 20 km. The Bay is located along the Montenegro margin and is part of a ria coastal system surrounded by high mountains that are part of the Dinaric range. The Bay is composed by three major basins, connected by two narrow straits with a maximum depth of 67 m. Despite its historical and geostrategic role the morphology and geology of the Bay is poorly known. New high resolution multibeam and seismic reflection data reveal unknown details of present-day morphologies and sedimentary infilling geometries. Several processes are involved in shaping the bay and its seafloor. Our results show that the observed morphologies are due to the interaction at different timescales of climate, water circulation, sealevel changes, erosion, sedimentation and tectonics constrained by the geological and structural setting of the area.

Passaro S.
A tool for a fast, semi-automatic cleaning of multibeam swath bathymetric records from spikes

Here we show a tool for the auto-cleaning of Digital Terrain Models (DTM) from spikes. This tool basically fits the contiguity of well developed depth measurements in a regularly spaced DTM, that helps to individuate and remove spikes from survey records. The method consist in a recursive approach in which a bathymetric grid is generated starting from very large cell size values (e.g., about ten times the grid cell size of the final product) and then compared with the vertical distance between each measurement and the filtered DTM (residuals). Finally, a threshold value is opportunely chosen and beams with residuals that are larger than the threshold value are excluded from the cleaned record. The processing flow requires several iterations cycles, made by reducing both the cell size and the threshold value for each iteration step. The method here proposed is a self-excluding process that helps to choose between data by killing (or not) each single measurement, thus resulting in a simple removal of wrong measurement from the original bathymetric record.

Passaro S., Ventura G.
On the use of morphometric indicators to improve and simplify the interpretation of multibeam swath bathymetric data: case studies from volcanic and non-volcanic settings

The widespread, increasing availability of high-resolution multibeam swath bathymetric data in the last years provides an opportunity to study with unprecedented detail the seafloor morphology throughout the use of morphometric parameters. These are characterized by factors that help to highlight local or general properties of the seafloor both in coastal and deep marine environment as well as in volcanic and non-volcanic settings. Here, we show some tools used over the last ten years, either new or readjusted from previously existing, which helpe to improve the interpretation and emphasize the results in terms of quantitative descriptions of the morphological features of marine landforms. We show the use of morphometric indicators to enhance: 1) the structural properties of seamounts; 2) the spatial arrangement and structural control on apparently chaotic sets; 3) the semi-automatic mapping such as the use of profile curvature to identify objects/targets outcropping from the seabed as archaeological outliers.

Daniele Casalbore
Repeated bathymetric surveys as a fundamental tool to measure rapid seafloor variations in geologically-active areas: examples from Southern Italian coastlines

Multibeam bathymetry has deeply changed our vision of the seafloor, allowing to map a large suite of landforms associated to oceanographic, sedimentary, volcanic and tectonic processes. Besides the advances in understanding the processes shaping the seafloor, these data represent a basic input both for a first assessment of marine geohazards and for planning more detailed studies. In this regard, the use of repeated bathymetric surveys in geologically-active areas is becoming a fundamental tool to evidence and monitor areas affected by rapid seafloor variations, whose genesis can be linked to active natural phenomena that otherwise would be often undetectable. In this paper, we show a review of examples from Southern Italy, where the application of such methodological approach allowed to monitor active erosive-depositional and volcanic processes.

C. García Izquierdo, A. Garcia-Benadí, P. Corredera, D. del Campo, S. Hernandez, J. del Río Fernandez, M. Nogueres-Cervera, C. Pulido de Torres
Traceable Sea Temperature measurements performed by Optical fibers

In the framework of the EMRP project “ENV 58. Metrology for essential climate variables”, a new technique to perform traceable temperature measurements of the sea water column and sea water surface was designed and it is being studied and applied to real situation in the submarine observatory (www.obsea.es). This new technique is based on optical fiber Bragg gratings, which implies the distribution of temperature sensors along the fiber. In the design of these distributed thermometers special attention was paid to the involved materials in order to avoid the damages of such corrosive environment. These fibers were calibrated as optical instruments and as thermometers, in order to get traceable measurements, as well as, reliable uncertainty calculation of the seawater temperature profile and of the sea water surface temperature, that are being continuously measured. Besides, these new devices are continuously compared to the current thermometers, CTD, located in the submarine observatory.

Frank Bastkowski, Beatrice Sander, Steffen Seitz, Jens Daniel Müller
Traceability of pHT values of equimolal TRIS buffered artificial seawater solutions in brackish waters

Assessment of seawater acidification can be achieved by the measurement of pH. A prerequisite for reliable and comparable pH values is traceability of pH measurement results to an agreed higher order pH standard. While this has already been established for low ionic strength aqueous solutions, traceability of pH measurement results for high ionic strength solutions is about to be realized for artificial seawater samples in the middle salinity range (5-20) on the so called total pH scale (pHT). In the present work we show details of the pHT measurement procedure for the measurement of TRIS (Tris(hydroxymethyl)- aminomethane) buffered artificial seawater solutions and the traceability of the measurement results to the SI system of units.

Steffen Seitz
Verification of the metrological Reliability of Standard Seawater Calibration

The calibration of standard seawater, the most relevant standard for worldwide Practical Salinity measurements, is based on a conductance ratio measurement of standard seawater and a defined KCl solution. The results of an interlaboratory comparison measurement of such conductance ratios are presented at various salinities (7, 19, 35) and temperatures (5, 15, 25, 35 °C). The comparison reveals a dependence of the conductance ratios on the measurement systems that is larger than the uncertainty currently assigned to Practical Salinity measurements. This jeopardizes long term continuity of Practical Salinity measurements, if the type of instrument currently used for standard seawater calibration should not be available one day. There is a need for a metrological network for oceanographic observables to put Practical Salinity measurements on a sustainable metrological ground.

Maria Celia Magno, Francesco Venti, Giovanni Gaglianone, Giancarlo Pierfranceschi, Elena Romano
Grain Size Analysis: A Comparison Between Laser Granulometer and Sedigraph

A total of 24 sediment samples from 5 different Italian marine sites (4 from Tyrrhenian Sea and 1 from Adriatic Sea) were analyzed for grain size using two different instruments: Laser Granulometer (LG) and X-ray Sedigraph (XS). The analysis was carried out exclusively on the fine fraction (<63 um), obtained by dry sieving, in order to compare data results and highlight potential differences. The results show an increase of 15-25% of clay content in the samples analyzed by XS with respect to the ones analyzed by LG. In spite of analyzing the <63 um fraction, both instruments recorded the presence of variable amount of sand in most samples, with high percentages (up to 53.3% for XS and 30% for LG) in the Bagnoli samples. The different results supplied by the two instruments may be attributed to the different principles of functioning of the two instruments and to the peculiar physical properties of the particles such as shape, density and mineralogical composition.

Sacchi M., Matano F., Passaro S.
Integrated geophysical techniques to image short to very short-term ground deformation associated with unrest at coastal calderas: a case study from the Pozzuoli Bay, Campi Flegrei, South Italy

Campi Flegrei is an active, large (about 200 km2) volcanic complex located offshore in the northern sector of the Naples Bay. The inner, peri-calderic area is characterized by severe, non-linear ground deformation and associated displacement of manufacts (bradyseism). Here we show the results of marine geophysical surveys (multibeam swath bathymetry) and satellite observations (SAR Interferometry) aimed at the detection and measurement of the coastal horizontal and vertical displacements of segments compounding the Pozzuoli Bay, and mostly corresponding to the inner part of the Campi Flegrei Caldera. Radar satellite observations provided a means for the definition of both regional and local displacement (uplift and/or subsidence) of discrete areas and associated infrastrucures (e.g. buildings, landmarks, archeological remains) on the emerged portion of the caldera structure, thus allowing for the understanding of the active trends of bradyseism for each coastal segment over the last 25 years. At same time, high-resolution multibeam swath bathymetry provided unprecedented accurate imaging of geomorphological lineaments, as well as of the Roman archaeological outliers presently extending over the seafloor. These data served as a constrain to reconstruct the evolution of vertical displacements in the coastal sector of the Pozzuoli Bay over the last 2.000 years ca. The integration of datasets also offers sound base information to define the recentmost-to-current trends of ground deformation at Campi Flegrei.

Elena Romano, Luisa Bergamin, Maria Celia Magno, Antonella Ausili
Comparison of Gravity and Vibro Corer for Acquisition of Environmental Data in Highly Impacted Areas. The Case of Augusta Harbor (Eastern Sicily, Italy)

Sediment cores may be used to reconstruct the chronological evolution of contamination in impacted areas and deep core levels may be used as reference conditions for the assessment of environmental status. For this, it is necessary to collect undisturbed cores, in which textural and chemical characteristics of each analyzed sediment layers correspond to the environmental conditions of the deposition times. Several devices are available and, among these, vibro and gravity corers are the most used ones. In this study, chemical (Ba, Hg, PCBs and PAHs) and grain size data obtained by means of gravity (SW-104) and vibro (Rossfelder®) corer from 3 stations of the heavily contaminated Augusta harbor were considered. They were compared considering the different technical characteristics of the corers, in order to demonstrate which is the difference for the data acquisition in terms of penetration depth. The results show that, for areas characterized by high sedimentation rates, the vibrocorer results the best choice for the higher penetration capacity. As regards sediment compaction and potential downward drag of any contaminants, the two devices do not show significant differences.

Page 273 of 977 Results 2721 - 2730 of 9762