Development of a Coastal Oceanographic Observatory for the North Aegean Sea: The AEGIS projects

The North Aegean Sea is a sub-basin of the Mediterranean which exhibits a range of oceanic processes at various scales. Due to the inflow of very light, mesotrophic Black-Sea waters it is the most productive region of the seas around the Hellenic Peninsula, although the regular seasonal coastal upwelling along its eastern shores does not contribute to its productivity. Despite the continuous buoyancy import by the Black Sea, the North Aegean hosts the densest waters of the Eastern Mediterranean. Finally, three semi-enclosed bays located in two islands of the North Aegean exhibit an alternating behavior as sources or sinks of buoyancy for the basin, while their productivity and natural beauty support a range of coastal activities. For the above reasons, the University of the Aegean has invested over several years in the development of a coastal oceanographic observatory (AEGIS), covering both the open North Aegean Sea and the three main bays of the islands of Lesvos and Lemnos. The Observatory consists of a numerical modeling component and an observational component.

The modeling component of the observatory consists of four coastal circulation models (for the three bays and the island of Lesvos) nested within a larger domain circulation model covering the whole Aegean Sea north of 37º N. Data assimilation, employing both satellite (sea-surface temperature and sea-level) and field data (employing mostly ARGO float observations) is used in the model of the extended domain (an implementation/configuration of the ROMS system), while the observations obtained in the coastal regions are currently used for coastal models’ (DELFT-3D FLOW and ROMS) validation. In addition to the above circulation models, SWAN is used to simulate the surface waves and DELFT-3D WAQ is being implemented to simulate the biochemical functioning at the various model domains.

The observational component at small geographical scales (in the Bays) comprise of continuous meteorological and oceanographic observations through an oceanographic mooring in the middle of the Bay of Kalloni, sea-level observations at the Bays of Kalloni and Gera, and High-Frequency radar observations of sea-surface currents and waves in a region east of Lemnos island, aiming to monitor the Black Sea outflow into the Aegean. The above continuous measurements are supplemented by periodic hydrographic and biogeochemical measurements in the three Bays, to validate the models and calibrate the in-situ continuous data. A recent addition to the AEGIS’s observational arsenal is an ocean glider aimed to capture the variability of the open North Aegean sea.

The AEGIS Observatory provides the necessary background to support strategic planning of human interventions at regional and local scales, such as Marine Spatial Planning or the construction of river dams affecting sensitive coastal basins. The implementation of the Coastal Laboratory has been supported by several projects, the most recent being the project “Coastal Environment Observatory and Risk Management in Island Regions AEGIS+” (MIS 5047038), implemented within the Operational Programme “Competitiveness, Enterpreneurship and Innovation” (NSRF 2014-2020), cofinanced by the Hellenic Government (Ministry of Development and Investments) and the European Union (European Regional Development Fund).