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In this study we investigated the hydrodynamics and the interaction between riverine and marine waters in the Po River‐Delta‐Sea (RDS) system (Italy). Through the application of an unstructured 3D numerical model to a domain comprising the Po river branches, seven coastal lagoons and the shelf sea, many of the hydrodispersive phenomena evolving from the interaction of the different water bodies of the RDS system were described. The model was successfully calibrated and validated for water levels, fluxes at the inlets and at the river branches, and water temperature and salinity observations. The use of such a comprehensive approach allows the characterization of the general hydrodynamics of all the components of the Po RDS system, of the water exchange between different water bodies as well as the Po river discharge distribution among all branches. The analysis of calculated coastal current patterns in the prodelta of two different years and during a flood event confirms that the Po River is the main driver of the baroclinic coastal sea circulation. However, when strong winds occur (Sirocco and Bora), the surficial circulation of the shelf area is significantly modified. Generally, the lagoons of the Po RDS system can be considered hydrodynamically active since their tidal prisms represent a relevant fraction of each lagoon's volume. The natural consequence is that the lagoons show an active flushing with water renewal times in the order of few days. The hydrodynamics is mainly forced by the tide and is locally enhanced by riverine inputs and wind. Where freshwater inputs are significant, they are responsible of the lagoons salinity patterns that show high spatial gradients (not all the lagoons are well mixed) and temporal variability. The variability of the freshwater discharges and the complex morphology of the Po RDS allows the presence of both marine and riverine environments. Key Points: The application of a 3‐D shallow water equation hydrodynamic model simulated the circulation, freshwater mixing, and residence time in the Po River‐Delta‐Sea systemThe hydrodynamic characterization of the different water bodies, their mutual interaction, and mixing properties were studiedThe spatial and temporal variability of the renewal times and flushing properties of the lagoons were investigated, as like the main natural factors driving them [ABSTRACT FROM AUTHOR]

Human interventions have drastically altered the hydrologic regime of the Razelm - Sinoe Lagoon System. Over the past four decades, following the closure of the main inlet (Gura Portiei) and the engineering of the other main communication inlets and channels, significant changes have occurred in the hydrological regime. This major disruption of the water and sediment circulation generated, at its turn, significant changes of the water chemistry, biology and lagoon ecosystems, transforming the system in eutrophic environment with all related consequences. Due to the significant decrease in sediment load transported along the coastal zone, the barrier beach separating the Lagoon System from the Black Sea is almost entirely subject to coastal erosion. Environmental improvement and rehabilitation is already a major demand of the local communities. Nevertheless, environmental recovery plans must be based on the detailed understanding of the water circulation in the lagoon system. This can be achieved only by the involvement of numerical modelling. Simulations have been performed using the hydrodynamic model SHYFEM, in order to obtain a response of the Razelm - Sinoe Lagoon System to the main forcings. The results show that the salinity distribution in the Lagoon System is, mainly, controlled by the freshwater discharge and, secondly, by wind, which can intensify the freshwater input. The calculated renewal times of the Razelm - Sinoe Lagoon System are very high, over one year, and classify the lagoon as a chocked system. This work represents a first step towards the detailed quantitative study of this sensitive part of the Danube Delta Biosphere Reserve. [ABSTRACT FROM AUTHOR]

Transitional areas such as lagoons are among the most impacted and delicate environments, threatened by the combined effects of climate change and human action. The integrated management of these specific systems would require the possibility to investigate and cope with induced changes in the hydrodynamics, morphodynamics and ecosystem characteristics. The main goal of the present work is to examine, by means of a modeling tool, the effects of the combined action of sea level rise, climate changes and human activities, such as the building of structures for coastal defense (mobile barriers), on transitional area habitats. The finite element coastal model SHYFEM was applied on the Venice Lagoon, which fully represents the example of a natural-anthropogenic environment, due to the continuous action of humans in changing it for preservation. The model was forced by a regional downscaling from a global climate atmospheric model, simulating both the control century (1960–1990) and three periods (2010–2039, 2040–2069, 2070–2100) of the Intergovernmental Panel for Climate Change (IPCC) A1B scenario that corresponds to a very rapid economic and demographic growth combined with the introduction of more efficient technologies. A relation on the interaction between salt marshes inundation and growth and salt marshes halophytes distribution was discussed. Results showed a tendency of the system to marine physical characteristics, in terms of an increase in salinity. The hypothetic increase of sea level tends to produce a decrease of areas like salt marshes, up to a total extinction for the most extreme scenario. The modeling results identified the correlation of halophytes growth and specific physical conditions of the environment (salinity, exposure time, soil depth respect to mean sea level), leading to the preliminary conclusion that the halophyte more resilient to the increase of flooding and of salinity ( Salicornia veneta ) would be the only one present in the future. The modeling implementation allowed the investigation of the whole lagoon, providing an hypothesis of the evolution of halophytes population in future scenarios and a precious tool also for the integrated management of these typologies of environment, in a climate change perspective. [ABSTRACT FROM AUTHOR]

An integrated approach was used to understand how wind and freshwater input influence the water circulation along the Romanian Black Sea coast. Field data from different ADCP (Acoustic Doppler Current Profiler) surveys in the area of the delta were combined with a 3D finite element model. The model SHYFEM (Shallow Water HYdrodynamic Finite Element Model), developed at the Institute of Marine Sciences (ISMAR - National Research Council, Venice, Italy), was used on the entire Black Sea, with higher resolution near the Romanian coast and the Danube River distributaries. Several theoretical simulations were carried out, varying the wind velocity and river discharge, according to the available long-term data and using measured data as a reference for model validation. The simulated currents have the same order of magnitude as the measured ones. The results show that the Danube discharge influences the circulation along the entire Romanian Black Sea coast, generating a longshore current, mainly localized in the surface layers. This current occurs even at low river discharges and is found both at low and high wind velocity. In this study we compared the results of the simulations for two main wind directions, NE and SE, but the wind from SW (generally inland) was also considered since it is opposite to the downdrift buoyant flow propagation. Maps of the current field and the fluxes, calculated on several sections perpendicular to the coast, were analyzed for all these forcings. We made the simulations both for the cold and warm season, by applying different temperature and salinity fields. The results show that, for both cold and warm seasons, the constantly blowing wind becomes a significant factor in the formation of coastal currents. Calculated fluxes on cross-sections versus Danube discharge usually show important differences between the cold and warm seasons, which are due to the distribution of temperature and salinity. Those seasonal differences are less significant in the case of increased wind velocity. Thus, at higher velocity, wind becomes a dominant factor, controlling the overall circulation. This study is a first step towards the development of a fully operational oceanographic model for the northwestern part of the Black Sea. Future developments will include the use of real meteorological forcing, modelling of the waves and sediment transport. [ABSTRACT FROM AUTHOR]

Modeling studies of future changes in coastal hydrodynamics, in terms of storm surges and wave climate, need appropriate wind and atmospheric forcings, a necessary requirement for the realistic reproduction of the statistics and the resolution of small scale features. This work compares meteorological results from different climate models in the Mediterranean area, with a focus on the Adriatic Sea, in order to assess their capability to reproduce coastal meteorological features and their possibility to be used as forcings for hydrodynamic simulations. Five meteorological datasets are considered. They are obtained from two regional climate models, implemented with different spatial resolutions and setups and are downscaled from two different global climate models. Wind and atmospheric pressure fields are compared with measurements at four stations along the Italian Adriatic coast. The analysis is carried out both on simulations of the control period 1960-1990 and on the A1B Intergovernmental Panel for Climate Change scenario projections (2070-2100), highlighting the ability of each model in reproducing the statistical coastal meteorological behavior and possible changes. The importance of simulated global- and regional-scale meteorological processes, in terms of correct spatial resolution of the phenomena, is also discussed. Within the Adriatic Sea, the meteorological climate is influenced by the local orography that controls the strengthening of north-eastern katabatic winds like Bora. Results show indeed that the increase in spatial resolution provides a more realistic wind forcing for the hydrodynamic simulations. Moreover, the chosen setup and the global climate models that drive the regional downscalings appear to play an important role in reproducing correct atmospheric pressure fields. The comparison between scenario and control simulations shows a small increase in the mean atmospheric pressure values, while a decrease in mean wind speed and in extreme wind events is observed, particularly for the datasets with higher spatial resolution. Finally, results suggest that an ensemble of downscaled climate models is likely to provide the most suitable climatic forcings (wind and atmospheric pressure fields) for coastal hydrodynamic modeling. [ABSTRACT FROM AUTHOR]

The main aim of this study is the understanding on how winds and freshwater inputs influence the currents circulation along the Romanian coast. It is a "sensitivity" study of how the Romanian coastal circulation varies changing the main forcings acting on it. In order to do this, a finite element model of the entire Black Sea was used, having a high resolution mesh near the Romanian coast and the Danube distributaries. Several theoretical simulations were carried out in order to understand the influence of the Danube discharge and of the wind on the coastal current. The obtained results show that the water discharge from the Danube influences the current along the entire Romanian Black Sea coast, generating a longshore current mainly in the surface layers. This current occurs even at low discharges and is evident both at low and high wind velocity. [ABSTRACT FROM AUTHOR]

This study is focused on the southern Romanian coast, confined by the city of Constanta (north) and Vama Veche village, at the border with Bulgaria (south). Here the coastal morphology is influenced by nearshore current circulation, disrupted during the last few decades by severe human interventions, such as building groins, jetties and other coastal protection activities. Nevertheless, the dynamics of coastal currents has not been thoroughly studied (or at least the works have not been published) over the past decades. This is why this paper aims to present the preliminary results of a numerical hydrodynamic model applied for coastal currents circulation in the above mentioned study area. All available data concerning the bathymetry of the Black Sea, the boundary conditions and the wind velocity are used in a process based hydrodynamic model. Hydrodynamic simulations provide the calculated surge and coastal current velocity. The simulations took into account two representative periods (February 2006 and June 2006) and the results indicate the large variability of the nearshore currents. Despite this variability, the dominant direction of the currents follows the characteristics of the wind climate of the study zone. [ABSTRACT FROM AUTHOR]

Abstract: To protect Venice from flooding, a number of protective measures have been adopted, including a system of mobile barriers known as MOSE. These separate the lagoon from the surges in the Adriatic Sea but interfere with shipping and on port activities. We estimate direct costs on ship traffic resulting from the use of MOSE, i.e., the additional costs of longer waiting time when passing through the Venice Lagoon. Our estimate uses inputs from a hydrodynamic model applied to the ship traffic between 2000 and 2002 and indicate that these costs range from €347,943 to €1.3million a year, depending on the hypotheses adopted. [Copyright &y& Elsevier]

Background, aim and scope Opposite interests must coexist in coastal areas: the presence of significant cities and urban centres, of touristic and recreational areas, and of extensive shellfish farming. To avoid local pollution caused by treated wastewaters along the Northern Adriatic coast (Friuli Venezia-Giulia and Veneto regions), marine outfall systems have been constructed. In this study, the application of a numerical dispersion model is used to support the traditional monitoring methods in order to link information concerning the hydrodynamic circulation and the microbiological features, to evaluate possible health risks associated with recreational and coastal shellfish farming activities. The study is a preliminary analysis of the environmental impact of wastewater treatment plants (WWTPs) with submarine discharge outfalls. It also could be useful for the water profile definition according to the Directive 2006/7/EC on the quality of bathing water and for the integrated areal analysis (Ostoich et al. 2006), to define the area of influence of each submarine discharge point. Materials and methods Historical data on discharges of the considered WWTPs were recovered and evaluated. Data on discharges' control for Veneto region (WWTPs of Lido and Cavallino) were produced by the WWTPs' manager Veritas Laboratory service, while data for the WWTPs of Friuli Venezia-Giulia region were produced by the regional environmental protection agency in the institutional control activity following official methods. The hydrodynamic model used in this work is the three-dimensional version of the finite element model SHYFEM, developed at ISMAR-CNR (Marine Science Institute of the Italian National Research Council) in Venice (Umgiesser et al. J Mar Syst 51:123-145, 2008). Results and discussion Numerical simulations have been carried out with the 3D version of the finite element model SHYFEM for 3 months during autumn 2007 to evaluate the bacterial pollution dispersion along the coasts of Veneto and Friuli Venezia-Giulia regions, prescribing meteomarine forcings and concentration values at the points corresponding to the positions of the submarine outfalls. Model results show that during autumn 2007 the discharges of the submarine outfalls of the Venice province seem to have no impact on the surface water quality, while there are some visible effects in the Gulf of Trieste. This reflects the behaviour of the experimental data collected by ARPAV and ARPA FVG and monitoring campaigns both on water and shellfish quality.… [ABSTRACT FROM AUTHOR]

This paper deals with the interaction and small-scale processes occurring around the inlets that connect the Venice Lagoon with the Northern Adriatic Sea. In a previous paper, barotropic processes have been investigated, whereas here, the focus is on the baroclinic processes. The hydrodynamics of the area are studied by means of a 3D shallow water hydrodynamic finite-element model, suitable to describe areas of complex morphology such as the coasts and the interaction channels. This is the first work that models the 3D interaction between the Venice Lagoon and the Adriatic Sea. Three different sets of simulations have been carried out to identify the physics behind the small-scale processes and the influence of the main forcings on the study area. The first imposes different idealized forcings, such as tides, wind, and river runoff. The vorticity maps of the first two layers show the predominance of wind forcing in the coastal area and tidal forcing in the three inlets of the Lagoon. Bora wind acts homogeneously, increasing the littoral currents, while Sirocco wind mainly impacts near Chioggia inlet, with a coastal current reversal, inducing its detachment offshore. Freshwater patterns are present along the coast, near the river mouths. Rivers do not directly influence the circulation close to the coast in front of the Venice Lagoon, except for the area near Chioggia inlet, where the Brenta river action can be seen. The second set of simulations deals with a sensitivity analysis to define the importance of the advection and of the baroclinic pressure gradient terms in the creation of persistent structures, such as small-scale coastal vortices seen along the littoral very close to the inlets. This analysis shows how advection is the main physical process responsible for the persistence of the positive vorticity structures close to the coast between the inlets, while the negative vorticity structures, also seen by the HF Radar, are due to the baroclinic-advective interaction. Finally, a real case, year 2004, has been simulated both to validate the model with observations and to identify the occurrence during the year of the characteristic hydrodynamic features attributable to the main forcings. The action of Bora wind characterizes the surface current patterns of February and November 2004, while Sirocco influences the month of May 2004. During periods of weak wind, the model reproduces the small-scale vortical structures close to the littoral. [ABSTRACT FROM AUTHOR]

Abstract: An operational surge forecast system based on a combination of a hydrodynamic model and an artificial neural network is described. The system runs at the Centre for sea level forecasting and flood warnings of the Venice Municipality (ICPSM, Istituzione Centro Previsioni e Segnalazioni Maree) and is focused on the prediction of the surge near Venice. The hydrodynamic model provides a five-day forecast for the Mediterranean Sea. Then, results near Venice are extracted and improved using a neural network. The method exposed in this paper reduced by half the average error of the hydrodynamic model for the first day forecast and maintains good performances also for longer forecasts. Moreover it is able to reduce the bias error of the model. [Copyright &y& Elsevier]

A finite element hydrodynamic model has been used to describe the water circulation and the water transport times of the Lagoons of Marano and Grado, Italy. The hydrodynamic circulation of the lagoon has been simulated taking into account different forces such as tide, wind and rivers. The model has been validated by comparing the simulation results against measured water levels and salinity and water temperature data collected in several stations inside the lagoons. Once the model has been validated, water residence time have been estimated for two different scenarios. [ABSTRACT FROM AUTHOR]

In this work the flushing features of a tidal active coastal basin, the Venice lagoon, have been investigated. The water transport time scale (TTS) has been computed by means of both an eulerian and a lagrangian approach. The obtained results have been compared in order to identify the main differences between the two methods. The eulerian water transport time (WRT) scale has been computed through the definition of the remnant function of a passive tracer released inside the lagoon whereas the lagrangian water transport time (WTT) scale has been computed tracking the trajectories of simulated particles released inside the basin. Both the methodologies rely on computer modeling. A 2D hydrodynamic model based on the finite element method has been used. The model solves the shallow water equations on a spatial domain that represents the whole Adriatic Sea and the Venice lagoon. Numerical computations show that the two techniques, when applied to a tidal active coastal basin, characterized by a complex morphology and dynamic, are differently influenced by the tidal variability. In particular, the type and the phase of the tidal forcing at the beginning of the computation strongly influence the WTTs distribution within the basin. On the other hand, the WRTs computation is not affected by the tidal forcing variability. [Copyright &y& Elsevier]

The finite element model SHYFEM was used to study the hydrodynamics and variability of water level, salinity, temperature, and water residence time (WRT) in the Oualidia lagoon located on the Moroccan Atlantic coast. The lagoon hosts a RAMSAR convention-protected area and also offers a set of valuable ecosystem services providing the source of income for the local population. To assess the effects of submarine groundwater discharge (SGD) inputs in the study area, four simulations were set up using different SGD inputs estimates in addition to tidal forcing, bathymetry, meteorological data including solar radiation, rain, and wind, in addition to boundary conditions in the Atlantic such as salinity, water level, and water temperature. The model was calibrated and validated using hydrodynamic measurements of previous studies in 2012 and 2013. The final results from the model are in good agreement with measured data. The simulation with SGD input ~0.05 m3 s−1 produced salinity values closest to the observed ones. Calculated spatial distribution of WRT, temperature, and salinity reduced to coordinates in two PCA axes is consistent with lagoon zones developed earlier using the benthic macroinvertebrate distribution. The calculated spatial distribution of WRT allowed us to evaluate the placement of oyster aquaculture farms and small-scale fisheries in relation to water quality issues existing in the lagoon. [ABSTRACT FROM AUTHOR]

A hydrodynamic model of the Venice Lagoon and the Adriatic Sea has been developed in order to study the exchanges at the inlets of the Venice Lagoon, a complex morphological area connecting the sea and the lagoon. The model solves the shallow water equations on a spatial domain discretized by a staggered finite element grid. The grid represents the Adriatic Sea and the Venice Lagoon with different spatial resolutions varying from 30 m for the smallest channels of the lagoon to 30 km for the inner areas of the central Adriatic Sea. Data from more than ten tide gauges displaced in the Adriatic Sea have been used in the calibration of the simulated water levels. After the calibration, the tidal wave propagation in the North Adriatic and in the Venice Lagoon is well reproduced by the model. To validate the model results, empirical flux data measured by acoustic Doppler current profiler probes installed inside the inlets of Lido and Malamocco have been used and the exchanges through the three inlets of the Venice Lagoon have been analyzed. The comparison between modeled and measured fluxes at the inlets outlines the efficiency of the model to reproduce both tide- and wind-induced water exchanges between the sea and the lagoon. Even in complex areas, where highly varying resolution is needed, the model is suitable for the simulation of the dominating physical processes. [ABSTRACT FROM AUTHOR]

In this work, water circulation in the Gulf of Oristano was investigated using a 2D hydrodynamic model. The model is based on the finite-element method. This solves the shallow-water equations on a spatial domain representing the Gulf of Oristano and the surrounding coastal sea. The hydrodynamic features of the gulf were investigated when the basin is influenced by different wind regimes. In order to evaluate the renewal capacity of the basin, the residence and the transit times were computed for each scenario. The study reveals that the gulf is characterized by circulation patterns promoting strong trapping phenomena. The results obtained are partially confirmed by the heavy-metal distribution in the sediments. In particular, the southern part of the basin is characterized by the presence of high heavy-metal concentrations in the bottom sediment, in the same areas where model results reveal a strong trapping capacity. This study can be considered as a first attempt to investigate the wind-driven water circulation in the Gulf of Oristano, and the results obtained can help in planning hydrological campaigns in the basin. [ABSTRACT FROM AUTHOR]

Three years of mobile barrier operations have been simulated with a hydrodynamic model to check the efficiency of the barriers in defending the city of Venice from flooding. The simulations have been carried out in the actual situation and with a sea-level rise of 30 and 50 cm. Moreover, the interference of the barrier operations with the ship traffic has been studied. It is found that without a security increment for the forecasted water levels, the mobile barriers cannot defend completely Venice from flooding due to the uncertainty in the forecast. With a security increment of 10 cm, the barriers work well in actual conditions but still cannot avoid flooding with a global sea-level rise. The interference with the ship traffic is acceptable under actual conditions but becomes prohibitive with a sea-level rise of 50 cm, when nearly two-thirds of the ship passages are blocked or delayed. [ABSTRACT FROM AUTHOR]

Abstract: In this work the water residence time of the Venice Lagoon has been computed using a 2D hydrodynamic model. The model is based on the finite element method. It solves the shallow water equations on a spatial domain that represents the whole Adriatic Sea and the Venice Lagoon. The residence time has been defined through the remnant function of a passive tracer released inside the lagoon. The renewal capacity of the Venice Lagoon has been investigated when forced by the astronomic tide and by the two main local winds, bora and scirocco. The importance of the return flow from the Adriatic into the lagoon is shown. This influence has been quantified by the definition of the return flow factor that has been computed for each scenario. [Copyright &y& Elsevier]

Abstract: A framework of numerical models has been developed and applied to the coastal lagoon of Cabras in Sardinia, Italy. These models consist of a two-dimensional hydrodynamic model, a radiational transfer module of heat at the water surface and a transport diffusion model. In the first part of the research the hydrodynamic circulation of the lagoon has been simulated taking in account different forces such as tide, wind and rivers. A finite element hydrodynamic model has been applied to the lagoon, describing its geometry and bathymetry with about 6000 triangular elements. The time integration is handled by a semi-implicit algorithm. With the same model the evolution of the salinity in the lagoon has then been investigated. Moreover, a thermal radiative model has been implemented that can describe the temporal variation of the temperature in the lagoon. An ad hoc field campaign between November 2000 and October 2001 has been set-up in order to gather temperature and salinity data to compare with the results of these models. A special scenario has been also simulated in which the Scolmatore channel, which connects the lagoon to the sea and that is closed by a dam, has been opened, allowing the tide to enter more directly into the lagoon and enhance the water exchange. [Copyright &y& Elsevier]

A Finite Element Ecological Model (FEEM) has been set up by fully coupling a primitive equation finite element hydrodynamic model (FEM) to an ecological model derived from EUTRO, the ecological submodel contained in the water quality model WASP, released by US-EPA. The work required the ‘decoupling’ of EUTRO from WASP and its transformation into a standalone program, the testing of such a structure versus the results obtained by running the WASP in the 0D version, the improvement of its parameterisation up to the inclusion of zooplankton as a dynamic variable explicitly modelled, the definition of an interface module, and the actual coupling of the improved ecological module and the hydrodynamic primitive equation model. The integrated model has then been applied, as a first test, to the Venice Lagoon (VELFEEM). To this aim idealised forcings (tide, meteo) have been used together with actual field data (river discharge, nutrient loadings) to run simulations over a one-year period. Analysis of the results shows that the model is numerically stable, variations in the state variables are consistent, and nutrients, plankton and oxygen evolves in space and time in a ecologically coherent way. Main features of the lagoon, namely oxygen seasonal evolution and dispersion of nutrients from the point sources are qualitatively reproduced.An additional result is that the improved version of the 0D ecological submodel has been organised as an independent module which can be run by a single subroutine call, and therefore can be easily integrated in any structure and coupled to any hydrodynamic model. The coupling here presented demonstrates the ease of such an integration. [Copyright &y& Elsevier]

The Mar Menor lagoon has been subjected to high anthropogenic pressures. Among them, in the early 1970s, dredging and enlargement of one of the inlets to make a navigable channel has had strong consequences on the hydrology, ecology, and fisheries of the lagoon. In recent years, changes in agricultural practices have induced an eutrophication process, leading to loss of water quality. As a solution, some management proposals have included dredging of the inlets in order to increase the water renewal. However, these proposals did not take into account the negative effects of previous experiences nor the consequences on environmental conditions of the lagoon and therefore on biological processes. The purpose of this work is to assess the effect that proposed mitigation measures, could have on the hydrodynamic conditions and discuss its possible ecological consequences. A three-dimensional (3D) numerical model has been used to simulate the lagoon under different dredging scenarios, covering different dredging depths and extensions. The simulated current fields and fluxes through the inlets, as well as water renewal times have been compared for the different scenarios. It is found that some of the considered scenarios take the system beyond the threshold of sustainability, where the modified current dynamics could affect sediment transport, beach dynamics and fishing capacities in a significant way. Water exchange with the Mediterranean is also strongly affected, with consequences for species connectivity, and a homogenization of the water renewal times that could lead to loss of ecosystem heterogeneity and structural complexity. The study demonstrates the utility of numerical models as effective tools for the management of coastal areas. [ABSTRACT FROM AUTHOR]

In this study the effects that lagoons exert on the barotropic tidal dynamics of a regional sea, the Adriatic Sea, were numerically explored. This semi-enclosed basin is one of the places with the highest tidal range in the Mediterranean Sea and is characterised by the presence of several lagoons in its northern part. The tidal dynamics of a system comprising the whole Adriatic Sea and the lagoons of Venice, Marano-Grado and Po Delta were investigated using an unstructured hydrodynamic model. Numerical experiments with and without lagoons reveal that even if the considered shallow water bodies represent only the 0.5 and 0.002% of the Adriatic Sea surface and volume, respectively, they significantly affect the entire Northern Adriatic Sea tidal dynamics by enhancing tidal range (by 5%) and currents (by 10%). The inclusion of lagoons in the computation improved the model performance by 25% in reproducing tidal constituents in the Adriatic Sea. The back-effect of the lagoons on the open-sea tide is due to the waves radiating from the co-oscillating lagoons into the adjacent sea. This is the first time these processes are shown to be relevant for the Adriatic Sea, thus enhancing the understanding of the tidal dynamics in this regional sea. These findings may also apply to other coastal seas with connections to lagoons, bays and estuaries. [ABSTRACT FROM AUTHOR]

Satellite data are rarely used in storm surge models because of the lack of established methodologies. Nevertheless, they can provide useful information on surface wind and sea level, which can potentially improve the forecast. In this paper satellite wind data are used to correct the bias of wind originating from a global atmospheric model, while satellite sea level data are used to improve the initial conditions of the model simulations. In a first step, the capability of global winds (biased and unbiased) to adequately force a storm surge model are assessed against that of a high resolution local wind. Then, the added value of direct assimilation of satellite altimeter data in the storm surge model is tested. Eleven storm surge events, recorded in Venice from 2008 to 2012, are simulated using different configurations of wind forcing and altimeter data assimilation. Focusing on the maximum surge peak, results show that the relative error, averaged over the eleven cases considered, decreases from 13% to 7%, using both the unbiased wind and assimilating the altimeter data, while, if the high resolution local wind is used to force the hydrodynamic model, the altimeter data assimilation reduces the error from 9% to 6%. Yet, the overall capabilities in reproducing the surge in the first day of forecast, measured by the correlation and by the rms error, improve only with the use of the unbiased global wind and not with the use of high resolution local wind and altimeter data assimilation. [ABSTRACT FROM AUTHOR]

Abstract: Since advection and diffusion are the main physical processes that influence the cleaning capacity of coastal transitional waters, the 3-D spatial distribution of the water renewal times was used to delineate a physically-based zonation scheme. The temporal and spatial variations of the hydrodynamics are assessed using a validated three dimensional hydrodynamic finite element model. The developed methodology was applied to the Cape Peloro system, a coastal protected area located in the Messina Strait (Italy) consisting of two connected small brackish basins: the shallow Lake Ganzirri and the deep meromictic Lake Faro. The hydrodynamics of the two coastal lakes shows strong seasonal and spatial variation. The 3-D distribution of the water renewal times suggests a horizontal partition of the Lake Ganzirri into two sub-basins and a vertical zonation of the Lake Faro, with the mixolimnion extending till 10m depth and the presence of a persistent bottom stagnant layer. The derived physically-based zonation scheme helps in explaining the highly heterogeneous spatial distribution of many biogeochemical variables in the Cape Peloro coastal system. [Copyright &y& Elsevier]

Abstract: To describe the exchange of water and sediment through the Venice Lagoon inlets a 3-D hydrodynamic and sediment transport model has been developed and applied to a domain comprising Venice Lagoon and a part of the Adriatic Sea. The model has been validated for both current velocities and suspended particle concentration against direct observations and from observations empirically derived fluxes from upward-looking acoustic Doppler current profiler probes installed inside each inlet. The model provides estimates of the suspended sediment transport in the lower 3m of the water column that is not detected by acoustic Doppler current profiler sensors. The bedload model prediction has been validated against measured sand transport rates collected by sand traps deployed in the Lido and Chioggia inlets. Results indicate that, in the Lido inlet, 87% of the total load is in suspension, while the rest moves as bedload. [Copyright &y& Elsevier]

A number of parameterisations for the simulation of mixing processes in the thermocline are compared and tested against the microstructure data of the PROVESS campaigns, conducted in the northern part of the North Sea during the autumn of 1998. The transport term in the turbulent kinetic energy equation is parameterised via the introduction of a third stability function Sk for turbulent energy diffusion. The formulations are compared with a simpler scheme based upon limiting conditions for turbulence variables. Improved results are obtained with a new form of Sk. The best agreement is, however, found with the simpler limiting scheme. This is explained in terms of a turbulence length scale theory for stably stratified turbulence. In agreement with previous laboratory and ocean data it is found that the ratios of the Thorpe and Kolmogorov scales to the Ozmidov length scale approach critical limiting values in the thermocline. The first of these conditions is satisfied when limiting conditions are implemented into the scheme, providing the necessary minimum value for the dissipation rate, whereas the schemes without limiting conditions fail to produce this critical ratio. The basic reason for this failure is that the Thorpe scale is overestimated, which is shown to be connected to an even larger overprediction of the dissipation rate of temperature variance. To investigate the impact of non-resolved advective processes and salinity stratification on the turbulence predictions, additional numerical experiments were conducted using a simple scheme for data assimilation. The best agreement is found again with the limiting scheme, which is able to make reasonable predictions for the dissipation rate without knowing the detailed shape of the mean stratification profile. It is shown that advective transport due to tidally and wind-driven motions has a non-negligible impact on vertical mixing. This is seen in the data and the models by periodic enhancements of turbulent mixing inside the thermocline. [Copyright &y& Elsevier]

In this study we investigated the tidal dynamics in a system of inter-connected land-locked basins formed by the Mediterranean, the Marmara, the Black and the Azov seas (MMBA system). Through the application of an unstructured grid hydrodynamic model to a unique domain representing the whole MMBA system, we simulated the tidal propagation and transformation inside each basin and in the straits connecting them. The model performance was evaluated against amplitudes and phases of major tidal constituents from 77 tidal gauges. The numerical results provided a description of the characteristics of the principal semi-diurnal, diurnal and long-term tides over the entire system. Even if the narrow straits act as a barrier for the tidal sea surface oscillations, our numerical results demonstrated that the along-strait interface slope produces water fluxes between the adjacent basins of the same order of magnitude of the climatological transports estimated by several authors. The long-term tidal modulations of the water exchange between the Mediterranean and the Black seas resulted to be non negligible and may partially explain the monthly and fortnightly flow variability observed in the Dardanelles and Bosphorus straits. [ABSTRACT FROM AUTHOR]

Abstract: A numerical model, based on a finite element discretisation technique, was used to study water circulation in the Black Sea׳s north-western shelf, particularly near the Danube Delta and the Romanian coast. The numerical grid covers the entire Black Sea and the model resolution is gradually increased versus the Romanian coast to resolve both mesoscale and microscale hydrodynamic features. Sea level, water temperature and CTD profiles, collected in the north-western shelf, were used to validate the model. The seasonal and daily coastal hydrodynamics, in 2009, were studied using 3-D water current and salinity fields. Moreover, different numerical tracers were released on the Danube׳s arms to characterise the Danube׳s plume extension. Results show that near the Danube Delta the strong salinity stratification confines most of the wind momentum input to the surface water layer, while the subsurface current is mostly influenced by the open sea circulation. In the southern Romanian coast, the vertical salinity gradient is weaker and the action of the wind can reach deeper layers. The numerical tracers show a net predominance of the Kilia branch and how coastal anticyclonic eddies can trap the river freshwater, carrying it away from the coast. This happens especially in spring, when the Danube׳s discharge is high and a large eddy is active in front of the Kilia branch. [Copyright &y& Elsevier]

Abstract: A tide-surge-wave modelling system, called Kassandra, was developed for the Mediterranean Sea. It consists of a 3-D finite element hydrodynamic model (SHYFEM), including a tidal model and a third generation finite element spectral wave model (WWMII) coupled to the hydrodynamic model. The numerical grid of the hydrodynamic and wave models covers the whole Mediterranean with variable resolution. The comparison with coastal tide gauge stations along the Italian peninsula results in a root sum square error for the main tidal components equal to 1.44cm. The operational implementation of the Kassandra storm surge system through the use of a high resolution meteorological model chain (GFS, BOLAM, MOLOCH) allows accurate forecast of total water level and wave characteristics. The root mean square error for the first day of forecast is 5cm for the total water level and 22cm for the significant wave height. Simulation results indicate that the use of a 3-D approach with a depth-varying loading factor and the inclusion of the non-linear interaction between tides and surge improve significantly the model performance in the Italian coast. [Copyright &y& Elsevier]

Abstract: The study of impacts of the global climate change in the coastal lagoons, specially in the Mediterranean region, is an important starting point for all the vulnerability studies, risk assessment and management consideration about the mitigation measurements for these areas. The coastal lagoon of Mar Menor has been chosen in order to investigate the response of a transitional environment to A2 IPCC scenario using a numerical tool. A model to reproduce the hydrodynamical processes and the salinity and temperature distribution in the Mar Menor (Spain) was developed. The hydrodynamic model was forced with real wind and water level data (1985–1986) and the results of the simulation were used to calibrate the hydrodynamic model. Simulations of salinity and temperature were carried out in order to validate the model and to reproduce measurements for the year 1997. The model results show a good agreement with data and the model is able to reproduce the salinity and temperature field in the Mar Menor. The climate change simulation was carried out applying the A2 anomalies for 2100 to the 1997 input data set, in order to evaluate the response of the basin in terms of water exchange temperature and salinity variations. The results of the climate change simulation show an increase of the annual mean temperature of 3.28°C and a decrease of the salinity value of 1.53PSU. [Copyright &y& Elsevier]

Abstract: The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy. Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water endmember. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d). A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 ± 1.5, 3.8 ± 0.7, 3.0 ± 1.3, and 3.5 ± 1.0 × 1010 L d−1 for 223,224,226, 228Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 × 109 L d−1). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater. [Copyright &y& Elsevier]

Abstract: The MoSE project (construction of mobile barrier to safeguard the Lagoon of Venice) entails changes to the structure of the lagoon''s inlets. This could have consequences for the areas near the inlets and for the dynamics of the lagoon ecosystem as a whole. In order to predict the effects of the proposed alterations on the hydrodynamics of the lagoon, a well-tested hydrodynamic-dispersion model was applied. Simulations were carried out considering both idealised and realistic tide and wind scenarios. The results show that with the new structures the Lido sub-basin tends to increase its extension due the southward movement of the watershed, at the expense of the Chioggia sub-basin, whereas the Malamocco sub-basin changes its relative position, but not its extension. The residence time shows variations in agreement with this trend, decreasing in the southern part of the Lido sub-basin and increasing in the inner part of the Chioggia sub-basin. The variations in residence time and return flow factor indicate that they are caused by changes in both instantaneous current velocities and sea–lagoon interaction. In fact the new breakwaters in front of the Malamocco and Chioggia inlets modify the length and direction of the outflow jet (up to 1ms−1) and the patterns of the currents around the inlets and the nearby coast. The new artificial island in the Lido inlet changes the current pattern and increases the current velocity on the southern side of the channel propagating this effect up to the Venice city. The risks and benefits individuated from our conclusion are that the Lido sub-basin can improve its renewal time, but the more intense current speeds can be a risk for the conservation of habitats and infrastructures. Finally the micro-circulation between the breakwater and the coast in Chioggia and Malamocco inlets can be a trap for pollutants or suspended sediment. [Copyright &y& Elsevier]

Abstract: A mass balance of the naturally occurring short-lived radium isotopes (223,224Ra) in the Venice Lagoon was conducted by an integrated approach combining the directly estimated individual Ra contributions and hydrodynamic model results. Hydrodynamic data allows for the calculation of the Ra mass balance in sub-sections of the Venice Lagoon (boxes), which are characterized by physically homogeneous properties, instead of investigating the entire lagoon. Utilizing this method, both the seasonal and the spatial variability of the submarine groundwater discharge in the Venice Lagoon have been estimated. Between 14–83×109 L d−1 of water were calculated to flow across the sediment–sea interface, corresponding to 5–28 times the mean annual river input. The submarine groundwater discharge estimates were correlated with the residence time calculation to better understand spatial and seasonal variation. [Copyright &y& Elsevier]