Earth Sciences

ABSTRACT A sand ridge field with crests oriented NE-SW (52°) located between 55 and 85 m water depth on the Valencia continental shelf (Spain) was mapped with multibeam swath bathymetry and characterized with seismic profiling and sediment sampling. Boundary-layer hydrodynamic measurements conducted over a sand ridge at 66 m depth show evidence of wave and current sediment resuspension during a major storm event with a three-year recurrence period. From the measured intrawave sediment concentration profiles it is shown that the suspended sediment time evolution is related not only to mean currents but also to the wave field. The near-bottom shear stress generated during storm conditions reached around 1 N/m2 and was able to resuspend and transport sandy and muddy sediments for more than 32 hours. The total suspended sediment transport in a layer of 1 m above the bottom was around 4000 kg per meter width and directed 160°.

... Florida Summer 1997 A Shoreface Zonation in the Ebro Delta Based on Grain Size Distribution ... iu7r~ ABSTRACT I GUILLEN, J. and PALANQUES, A., 1997. A Shoreface Zonation in the Ebro Delta Based on Grain Size Distribution. Journal of Coastal Research, 13(3), 867-878. ...

ABSTRACT Turbidity, CTD, and temperature and shear microstructure data recorded along a 25 km transect from 8 to 69 m depth across the Ebro Delta shelf (northwestern Mediterranean) are presented. The water column was stratified and prior to the campaign the regional southwest flow was measured to have superimposed diurnal and sub-inertial components. The bottom boundary layer (BBL) at all stations deeper than 20 m has a vertical extension of 3 to 9 m, increasing to 12 m at the deeper stations and even to 14 m at a station at 45 m depth outside the studied transect. The law of the wall was identified at almost all stations with an extension ranging from 40% to 100% of that of the BBL. At some stations high dissipation rates were found in the interior of the bottom layer. The study shows the correspondence between the turbidity contents and the local mixing processes at the BBL and suggests that sub-critical reflection of internal waves could play an important role in boundary mixing. Our data also suggest that during the campaign, after two consecutive short episodes of high winds, the first baroclinic mode shifted to the second one.

ABSTRACT Publicación online disponible en: http://www.icm.csic.es/scimar/index.php The water turbidity measured with optical methods (transmittance and backscattering) is usually expressed as beam attenuation coefficient (BAC) or formazin turbidity units (FTU). The transformation of these units to volumetric suspended sediment concentration (SSC) units is not straightforward, and accurate calibrations are required in order to obtain valuable information on suspended sediment distributions and fluxes. In this paper, data from field calibrations between BAC, FTU and SSC are presented and "best-fit" calibration curves are shown. These calibrations represent an "average" from different marine environments of the western Mediterranean (from estuary to continental slope). However, the general curves can only be applied for descriptive or semi-quantitative purposes. Comparison of turbidity measurements using the same sensor with different calibration ranges shows the advantage of simultaneously combining two instruments calibrated in different ranges when significant changes in suspended sediment concentrations are expected. Data used in this paper were collected during the projects: FANS (MAS3-CT95-0037), CONCENTRA (AMB92-0251-C02-01), FLUXALB (MAR96 -1781-CO2-01), IMPACT (CEE. REF. 95/52), METRO-MED (MAS3-CT96-0049), PNEC and CAÑONES (MAR1999-1060-C03-01). Peer reviewed

ABSTRACT In a recent study, Gómez-Pujol et al. [Gómez-Pujol, L., Orfila, A., Cañellas, B., Alvarez-Ellacuria, A., Méndez, F.J., Medina, R., Tintoré, J., 2007. Morphodynamic classification of sandy beaches in low energetic marine environment. Mar. Geol. 242, pp. 235–246] used the Wright and Short beach classification scheme fed with hindcasted wave and sediment settling velocity data to classify the morphodynamic states of a group of low-energy Mediterranean beaches (Mallorca, Spain). Here, we use morphodynamic data obtained from an Argus video station and a morphodynamic model to assess the validity of this type of model for predicting beach states under typical Mediterranean wave conditions. The results show that Ω-values alone do not provide a realistic prediction of beach states statistics and that the intensity of the forcing, represented by the wave energy level and the duration of the events, must also be taken into account.

As part of the FRUELA experiment, 11 sediment cores were recovered from the Bellingshausen Sea, the western Bransfield and Gerlache Straits (Antarctic Peninsula) to determine the spatial distribution of organic carbon (OC), biogenic silica (BSi), and nitrogen (N) in the sediment under regions of known irregular primary production rates (PPRs).OC, BSi, and N contents ranged from 0.3% to 1.2%, from

... beach interventions were carried out during the study period, a nourishment of Bogatell and La Barceloneta in summer 2002 (Ojeda and Guillén ... of the beaches was obtained from November 2001 to December 2004 by means of an Argus video system (Holman and Stanley ...

The Ebro Delta coast is a microtidal, sandy shoreline affected by a low-energy mean wave climate. Consecutive topographical and bathymetrical surveys during the years 1990 and 1991 have allowed us to identify nine major longshore bar and trough systems as the main ...

The relative distribution of individual grain size fractions across the cross-shore coastal profile of Terschelling (North Sea) displays a constant shape when “average” conditions are considered. The shape of the distribution curve depends on the hydrodynamic processes acting in the littoral zone and, if the curve is contemplated in a normalized, relative form, it can be considered as a permanent

... An Argus video system (Holman and Stanley, 2007) has been used to study the beaches and the submerged sandbars since October 2001. Five cameras located at 142-m height offer a 180o view of the littoral zone (see Ojeda and Guill n (2008) for a more detailed description). ...

Two experiments were carried out to study the effects of trawling in the muddy prodeltaic deposit of the Llobregat River in the northwestern Mediterranean. Trawling was conducted in two experimental lines, and bottom morphology, sediment texture, and water turbidity ...

Images from an Argus beach monitoring station were analyzed to count the number of people on two city beaches in Barcelona (NW Mediterranean) every hour for 4 years. Daily, weekly, seasonal, and interannual user distribution patterns were clearly established. Two ...

The variability of the bottom sediment grain size was estimated at two sites located at 8.5 and 12.5 m depth across the Ebro Delta inner shelf from cores taken at the beginning and end of three one-month-long current meter + turbidimeter deployments. The sediment variability ...

... The lower river Ebro was an estuary that has evolved to a delta during the last millennium (from references in Bayerri 1934). The present promontory of the Ebro delta system (Fig.l) has mainly developed as a conse quence of human activities. ...