Cross-shelf and along-shelf fluxes derived from observation and modelling in the Gulf of Naples

Hydrological and currentmeter observations were collected on the continental shelf and slope of the Gulf of Naples during the GELATO experiment in the framework of med-TOSCA project (27 July to 6 August 2012). Results from the cruise are used to estimate the onshore/offshore cross-frontal transport at the shelf break of the Gulf of Naples. The hydrological structures evidence well-stratified water masses on the eastern and western ends of the shelf. In the coastal area the situation is quite complex, with the influence of the Sarno river's freshwater plume in the first meters of the water column. ADCP current profiles were used to estimate integrated transport along the meridional transect connecting the northern and southern gulf coast. ADCP data are missing in the surface layer because of the transducer ringing effect. To add the surface contribution to the total transport, HF radar current measurement were used to determine this component. CTD measurement were collected approximately along the same transect so both the barotropic and baroclinic contribution to the total transport can be evaluated. In addition, coastal circulation is simulated with a high resolution three-dimensional numerical model forced by daily realistic forcing along with heat and salt fluxes calculated by bulk formulae. The model outputs are in agreement with the main hydrological and circulation patterns and reproduces well the onshore transport

Characterizing the coastal dynamics behaviour within the Gulf of Naples using modelling, HF radar and in situ measurements

The integration of numerical models in coastal observatories represents a current challenge for the scientific community, constituting a frontier both for research purposes and for a variety of practical applications, ranging from coastal protection to search and rescue activities, or support to engineering works and operational structures. Here we present the monitoring network installed in the Gulf of Naples, our recent advances in coastal and in-situ observations and the integrated ocean-atmosphere modelling approach, through connections to the state of the art and still opened research issues that will be the challenges for the next years. Currently, the monitoring network of the Gulf of Naples is composed of moored instrumentation and a HF radar system composed of three antennas that provide hourly data of surface currents for the entire Gulf at a spatial resolution of 1 km. The ocean model configuration is a ROMS (Regional Ocean Modeling System)-based code, configured on the region (~13-15E, 40-42N). The increasing availability of long-term observations, the large dataset recently acquired in sea-truth campaigns and numerical output from meteorological and ocean models allow us to use these integrated tools to characterize the coastal dynamics processes, and thus provide quantitative support to decision makers in the field of management strategy on oil spill and search and rescue operations, vulnerability of coasts and correct management strategies of the environmental heritage. This talk presents diverse scientific issues recently addressed by the DiSAm (University of Naples Parthenope) in the broad activity of developing and tuning of the oceanic components of modeling system. We will show some numerical model results in the Gulf of Naples basin in response to high resolution atmospheric forcing provided by the SKIRON model focusing mainly on the seasonal circulation and on the mesoscale and submesoscale variability associated with the current system of the basin. A particular attention is devoted to the analysis of the fate of waters originated inside the Gulf and in the Tyrrhenian Sea, which circulate in the area, giving insights as to the water renewal mechanisms of individual subareas. The results of simulations are compared with eulerian synoptic measurements of surface currents provided by the HF radar system installed on the Gulf's coasts, showing a very good agreement between the two data sets

Inshore/offshore water exchange in the Gulf of Naples

The Gulf of Naples is a coastal area of the south-eastern Tyrrhenian Sea (Western Mediterranean) in which zones of great environmental and touristic value coexist with one of the largest seaports in the Mediterranean Sea, industrial settlements and many other pollution sources, in a context characterized by a very intense anthropic pressure. In such an environment, water renewal mechanisms are of crucial importance for the good ecological status of coastal waters. In this papers we focus on water exchange between the interior of the Gulf and the neighboring open Tyrrhenian sea. The surface dynamics of the Gulf has been investigated on the basis of measurements carried out with a HF radar system, which has proved to be an excellent tool for the synoptic assessment of the dynamics of coastal areas. The vertical component of the current field has been provided by an ocean circulation model, the Regional Ocean Modeling System (ROMS), implemented in a larger area of the Tyrrhenian Sea which includes the Gulf of Naples. We present results of a one-year long analysis of data and simulation results relative to the year 2009, which was characterized by episodes of severe decrease of the water quality in the southeastern sector of the Gulf. The general description of the dynamics of the area is accompanied by a detailed analysis of in-/offshore exchanges, assessed by looking at the zonal component of the surface and subsurface current field across a transect which represents a sort of threshold between the interior of the Gulf and the open sea. This also allows to reconstruct the short-term origin of waters found inside the Gulf in the different forcing and circulation conditions

Inshore/offshore water exchange in the Gulf of Naples

The Gulf of Naples is a coastal area of the south-eastern Tyrrhenian Sea (Western Mediterranean) in which zones of great environmental and touristic value coexist with one of the largest seaports in the Mediterranean Sea, industrial settlements and many other pollution sources, in a context characterized by a very intense anthropic pressure. In such an environment, water renewal mechanisms are of crucial importance for the good ecological status of coastal waters. In this papers we focus on water exchange between the interior of the Gulf and the neighboring open Tyrrhenian sea. The surface dynamics of the Gulf has been investigated on the basis of measurements carried out with a HF radar system, which has proved to be an excellent tool for the synoptic assessment of the dynamics of coastal areas. The vertical component of the current field has been provided by an ocean circulation model, the Regional Ocean Modeling System (ROMS), implemented in a larger area of the Tyrrhenian Sea which includes the Gulf of Naples. We present results of a one-year long analysis of data and simulation results relative to the year 2009, which was characterized by episodes of severe decrease of the water quality in the southeastern sector of the Gulf. The general description of the dynamics of the area is accompanied by a detailed analysis of in-/offshore exchanges, assessed by looking at the zonal component of the surface and subsurface current field across a transect which represents a sort of threshold between the interior of the Gulf and the open sea. This also allows to reconstruct the short-term origin of waters found inside the Gulf in the different forcing and circulation conditions

Filament formation and evolution in buoyant coastal waters: Observation and modelling

This paper presents a detailed analysis of the formation and subsequent evolution of filament-like structures observed in a relatively small area of the mid-Tyrrhenian Sea (Mediterranean Sea). The filament dynamics and potential impact on the cross-shelf exchange budget are investigated based on a combined use of remote sensing imagery, in situ data and numerical modelling. The complexity of these phenomena is shown by focusing on four distinct events that led to cross-shelf transport, each representative of a different dynamic process and a distinct expected impact on the coastal area. A systematic analysis of available observations for the years 1998–2006 underlines the role of the interplay of atmospheric freshwater fluxes, river loads and wind stress variations, which may create favourable conditions for the convergence of shelf waters (particularly at coastal capes) and the subsequent formation of short-lived filaments along the coast. The response of the buoyant coastal waters to periods of wind reversal and fluctuating freshwater discharge rates is examined through idealised Regional Ocean Modeling System (ROMS) simulations. The filaments observed in remote sensing imagery were well reproduced by the numerical exercise, where the filaments appear as organised submesoscale structures that possess high relative vorticity and develop at the river mouths or adjacent capes. In both scenarios, the filaments appear largely determined by (i) the presence of a buoyancy anomaly, (ii) the angle between the wind pulse direction and the coast and (iii) irregularities in the coastal profile. The ensemble of results suggests that the occurrence of such transient, intense structures may contribute considerably to the biological variability and cross-shelf exchange in coastal areas with similar traits

Currents, Tides and Waves measured by an HF Radar in the Gulf of Naples

An HF radar has been operating in the Gulf of Naples (Southeastern Tyrrhenian Sea) since 2004. The system is a SeaSonde manufactured by CODAR Ocean Sensors Ltd. Three mono-static radar units working at about 25 Mhz ensure the surface current mapping over nearly the entire Gulf of Naples area. The grid resolution is 1 Km with a range of approximately 40 Km. From continuous observations of the surface current fields several characteristics of the surface circulation were assessed. One of the most prominent evidences is the wind field forcing of the surface current, which determines different but recurrent circulation patterns affecting the transport and the off-in shore exchanges. The analysis of long and continuous current observations has revealed significant tidal currents. Previous studies regarding the tide magnitude in the Southern Tyrrhenian Sea showed a very limited tidal contribution to the current field. The determination of tidal current in the Gulf of Naples has pointed out a prevalent diurnal contribution and intensity values up to a maximum of 10 cm/s. Waves are one of the most important elements in a coastal management framework. HF radar may provide an estimate of the main parameters characterizing the wave field: wave direction, significant height and period. Waves were studied in the Gulf of Naples over a range cell located between 5 and 6 km from the coast. This choice, based upon preliminary sensitivity studies, allowed us to analyze the surface gravity wave field over an area of the Gulf where the depth is not too shallow and the sea echo intensity is sufficiently high to ensure good data quality. A pluriannual wave observation time series was studied in order to depict typical seasonal pattern