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Environmental management and simulation of coastal aquatic systems of the Thracian Sea (Doctoral thesis)

Κόκκος, Νικόλαος/ Kokkos, Nikolaos

The hydrodynamic characteristics of the surface plume produced by the outflow of the brackish Black Sea Water (BSW) through the Dardanelles Straights in the North Aegean Sea have been examined by a plethora of publications that thoroughly analyzed the characteristics of water circulation in the area. However, a significant gap exists between the results of these studies and the transfer of information to end-users operating in North Aegean Sea. Taking into account this gap a pilot online platform (Observatory) was developed at a pilot coastal Thracian Sea system, providing information and marine forecasts to users and the broad society. The platform collects, analyzes and processes historical and short-term prognostic data aiding decision-makers to formulate policies on ICZM matters engaging active citizens and the broader public into coastal zone issues, raising their awareness for coastal environmental protection, and promoting the distribution of information among coastal managers and stakeholders. The oceanographic and environmental processes in these systems are described giving real time information on sea conditions. To provide this information the platform is equipped with a series of modern coupled numerical models producing daily short-term prognostic results, which are then illustrated through maps at a wed based Geographic Information System (webGIS). Analyzing the outline of the thesis, it occurs that its first chapter reviews the existing operational oceanographic modelling efforts, and explains the objectives and the innovative elements of this work. Additionally, this chapter presents the main components of the developed platform and the interface of all interconnected models performed throughout the developed code sequence. The second chapter describes the study area (North Aegean Sea) and its essential features, as it is an area of complex topography in which a multitude of freshwater sources outflow along its surrounding coastal zone. In addition, the entry of the brackish Black Sea Water (BSW), a significant water mass for the circulation in the North Aegean Sea, together with the inflow of the higher in temperature and mare saline Levantine Intermediate Water (LIW) at the southern boundary of the region significantly affect the oceanographic characteristics of the area. At the third chapter the main features of applied meteorologic models (WRF and TAPM), the coupled hydrodynamic model (ELCOM) and the oceanographic database (myOcean) for the forecasting of coastal circulation and the distribution of oceanographic parameters such as water temperature, salinity and water density are presented. Furthermore, the interconnection of two biogeochemical models (a simple 1D water column model and a fully 3D model) developed specifically within the framework of the present thesis is explained. Chapter four describes the results produced by the high resolution numerical hydrodynamic simulation of the North Aegean Sea with the use of historical data during 2005-2009. The surface spreading of BSW plume is explained and its main trajectories are analyzed. The seasonality in the presence of meso-scale features developed in North Agean Sea is shown. Furthermore, the impact of BSW on water column stratification is discussed using the potential energy anomaly. Model results are validated using data derived from satellite images and field campaigns. In addition, the analysis of Empirical Orthogonal Functions (EOFs), a statistical method for complex spatio-temporal data analysis was applied on simulation results. The main hydrographic features describing the flow field were produced, showing that it is more effective to analyze data in representative variables by determining their modalities. In Chapter 5 the analysis of the main structures and the general circulation of water in the Thracian Sea is presented. Analysis focused on the surface layer of the water column, as shelf hydrodynamics in Thracian Sea depend on the meteorological effect, the spreading of BSW and the local freshwater outflows. Thus, an analysis of the outflow and impact of these rivers (Strymon, Nestos and Evros) in the wider Thracian Sea and their volume and nutrient fluxes is carried out. In addition, the main meso-scale structures appearing in the Thracian Sea, such as the Samothraki Anti-Cyclone, as well as the general cyclonic flow along the North Aegean coastline are analyzed. In Chapter 6 the webGIS platform implemented at at pilot area (Kavala Gulf) is presented. The aim was to provide to any end-user operating in the area short-term operational forecasts on the distribution of oceanographic parameters, such as water temperature, salinity, density, flow and sea surface level. In parallel, results from the biogeochemical models implementation are shown.