• Energy Research

A multi-proxy study of a Holocene sediment core (RF 93-30) from the western flank of the central Adriatic, in 77m of water, reveals a sequence of changes in terrestrial vegetation, terrigenous sediment input and benthic fauna, as well as evidence for variations in sea surface temperature spanning the last 7000 years. The chronology of sedimentation is based on AMS 14C dates of foraminifera extracted from the core, palaeomagnetic secular variation, pollen indicators and dated tephra. The temporal resolution increases towards the surface and is sub-decadal for the last few centuries. This paper illustrates the potential value of high resolution near-shore marine sedimentary sequences for recording wide-scale human impact on marine sedimentation and fauna and, potentially, disentangling evidence for human activities from that for past changes in climate. The main changes recorded in vegetation, sedimentation and benthic foraminiferal assemblages appear to be directly related to human activity in the sediment source area, which includes the Po valley and the eastern flanks of the central and northern Apennines. The most striking episodes of deforestation and expanding human impact begin around 3600 BP (Late Bronze Age) and 700 BP (Medieval) and each leads to an acceleration in mass sedimentation and an increase in the proportion of terrigenous material, reflecting the response of surface processes to widespread forest clearance and cultivation. Although human impact appears to be the proximal cause of these changes, climatic effects may also have been important. During these periods, signs of stress are detectable in the benthic foram morphotype assemblages. Between these two periods of increased terrigeneous sedimentation there is smaller peak in sedimentation rate around 2400BP which is not associated with evidence for deforestation, shifts in the balance between terrigenous and authigenic sedimentation, or changes in benthic foraminifera. The mineral magnetic record provides a sensitive indicator of changing sediment sources: during forested periods of reduced terrigenous input it is dominated by authigenic bacterial magnetite, whereas during periods of increased erosion, anti-ferromagetic minerals (haematite and/or goethite) become more important, as well as both paramagnetic minerals and super-paramagnetic magnetite. Analysis of the alkenone, UK’37, record provides an indication of possible changes in sea surface temperature during the period, but it is premature to place too much reliance on these inferred changes until the indirect effects of past changes in the depth of the halocline and in circulation have been more fully evaluated.

The northern Adriatic Sea is a basin where dense shelf waters form during winters if the following favorable con- ditions are attained: high salinities, mainly related to low river water discharge (Po river in primis) during fall season, and strong heat fluxes induced by cold and dry Bora wind events blowing from north-east. Extremely favorable conditions to Northern Adriatic Dense Waters (NAdDW) formation characterized winter 2012 when, following several months of low Po river runoff, a strong event of Cold Air Outbreak (CAO) occurred from the end of January until mid-February. Consequently, the mean temperature of northern Adriatic waters dropped to about 6°C and exceptional densities (potential density anomaly locally exceeding 30.0 kg m -3 ) were reached. The production and spreading mechanisms of dense water in the Adriatic Sea have been modeled by means of the COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment-Transport) modeling system. The model builds upon a high-resolution (1 km spaced horizontal grid), fully 3-D primitive equations hydrodynamic model coupled with a phase-averaged wave model and sediment routines, and is driven by simulated atmospheric forcings. The dataset used to assess model outputs relies on the measurements acquired during the dedicated field campaigns "Operation Dense Water", a set of two rapid response cruises carried out in southern Adriatic during winter 2012, and by five mooring arrays deployed in the Southern Adriatic Margin (SAM) that allowed the continuous acquisition of temperature, salinity, currents and suspended matter samples. Results from the integrated data-model approach suggest that the NAdDW propagates along the shelf to the southern basin following both a shallower vein and a deeper stream, with a process characterized by a strong var- iability (mean value of 0.31 Sv with peaks rapidly growing in the first weeks after the CAO up to 2.19 Sv). Addi- tionally, COAWST capability to couple different numerical models allowed to disentangle the relative importance of aspects on dense water generation, mixing and spreading, demonstrating how coupled runs can lead to vol- umes up to 50% larger with respect to uncoupled simulations. Additional light is shed on the transport pathways off the shelf and on possible sediment transport phenomena in the area, in this benefiting from an unprecedented spatial resolution and a new bathymetry reflecting very high resolution data acquired via multi-beam techniques. Although dense water propagation appears as a relatively large-scale process involving the whole western side of the SAM, topographic local discontinuities and seabed slopes appear crucial in triggering descent and governing flow patterns. The presence of suspended sediment along the water column, despite not significantly influencing the overall fluxes across sections, is responsible of pulling part of the veins towards deeper zones.

This work presents the results of long-term deep-water observations carried out in the southwestern Adriatic margin. Hydrodynamics and thermohaline measurements were carried out in the last 100 m of the water column using two long-term moorings placed at two different locations along the western sector of the Adriatic continental margin (open slope vs. submarine canyon). The observations, carried out over a period of almost 10 years, made it possible to define the intra- and interannual deep-water dynamics, which are mainly influenced by the passage of cold, dense water. The hydrodynamic field is influenced by seasonal behavior and varies from year to year, with no clear temporal trend or periodicity. Thermohaline properties follow hydrodynamics but also show a climatological trend toward higher temperatures and salinity. The combination and variability of preconditioning factors explains the interannual variability in dense water passage at the mooring sites triggering the formation of dense water in the northern Adriatic. The impulsive nature of the dense water flow, which is difficult to capture with sporadic oceanographic surveys, and its linkage with the large-scale atmospheric circulation make continuous monitoring essential to answer open questions about cascading processes and deep-water dynamics under a global change scenario.

Marine sediments are part of the hydrological cycle and the ultimate storage compartment of land-derived organic matter, including pollutants. Since relevant microbially-driven processes occurring at benthic level may affect the quality of the overall aquatic system, the necessity for incorporating information about microbial communities functioning for ecosystem modelling is arising. The aim of this field study was to explore the links occurring between sediment contamination patterns by three selected class of organic pollutants (Polycyclic Aromatic Hydrocarbons, PAHs, Nonylphenols, NPs, Bisphenol A, BPA) and major microbial properties (Prokaryotic Biomass, PB; total living biomass, C-ATP; Prokaryotic C Production rate, PCP; Community Respiration rate, CR) across a gradient of anthropogenic pollution. Sediments were sampled from 34 sites selected along 700 km of the western coastline of the Adriatic Sea. Organic contamination was moderate (PAHs <830 ng g-1; NPs <350 ng g-1; BPA <38 ng g-1) and decreased southward. The amount of PAHs-associated carbon (C-PAHs) increased significantly with sediment organic carbon (OC), along with microbial functional rates. The negative relation between PCP/CR ratio and OC indicated the shift toward oxidative processes in response to organic pollution and potential toxicity, estimated as Toxic Equivalents (TEQs). Our outcomes showed that sediment organic contamination and benthic microbial processes can be intimately linked, with potential repercussions on CO2 emission rates and C-cycling within the detritus-based trophic web.

This volume contains the main results of the EC FP7 “The Ocean of Tomorrow” Project CoCoNet, divided in two sections: 1) a set of guidelines to design networks of Marine Protected Areas in the Mediterranean and the Black Seas; 2) a smart wind chart that will allow evaluating the possibility of installing Offshore Wind Farms in both seas. The concept of Cells of Ecosystem Functioning, based on connectivity, is introduced to define natural units of management and conservation. The definition of Good Environmental Status, as defined in the Marine Strategy Framework Directive, is fully embraced to set the objectives of the project, by adopting a holistic approach that integrates a full set of disciplines, ranging from physics to bio-ecology, economics, engineering and many sub-disciplines. The CoCoNet Consortium involved scientist sfrom 22 states, based in Africa, Asia, and Europe, contributing to build a coherent scientific community. peer-reviewed

The paper describes formation and spreading of dense shelf waters in the Adriatic Sea (North Adriatic Dense Water, NAdDW) during the winter of 2012 as a consequence of an intense and long cold air outbreak of northeasterly Bora winds. As a result, during February 2012 northern Adriatic Sea water temperature dropped to about 6 degrees C and density exceeded 1030 kg/m(3), most likely the maximum value since 1929. NAdDW dynamics has been investigated by means of a 3-D ocean-wave coupled model running on a high resolution and eddy-permitting grid. The numerical experiments have relied on the Coupled-Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) system forced one-way with atmospheric forcings provided by the model COSMO-17. A suite of observational data has been used to characterize the Bora event and evaluate numerical model performance. At sub-basin scales, the newly formed waters flowing southerly have produced a water renewal of the northern Adriatic, as more than 50% of water volumes have left the basin. Dense waters volume transports, evaluated through different Adriatic cross-sections, have been modulated by tides (damped for the densest water masses) and reached about 1 Sv. The contribution of wave-induced forcings has been quantified and examined, indicating that these represent a major driving mechanism during NAdDW production and spreading phases. This work provides evidence that NAdDW is spread accordingly with two different mechanisms: at early stages of its formation, the wind-driven ocean circulation pushes newly formed waters to leave the northern basin with relatively high speeds (about 0.30 m/s). Later on, remaining NAdDW leaks slowly out (0.09 m/s as average) from the production site. Residence times of dense waters in the north, middle, and south Adriatic Sea are also documented. (C) 2014 Elsevier Ltd. All rights reserved.