Proceedings of the Twenty-second (2012) International Offshore and Polar Engineering Conference www.isope.org Rhodes, , June 17–22, 2012 Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE) ISBN 978-1-880653-94–4 (Set); ISSN 1098-6189 (Set)

Early Summer Circulation in the Gulf of (Greece)

Nikolaos Th. Fourniotis and Georgios M. Horsch Department of Civil Engineering, University of Patras, Greece

ABSTRACT recorded in the area. To address these concerns, it is crucial to understand the hydrodynamic circulation of the Gulf. Further, The hydrodynamic circulation of the has been studied knowledge of the circulation is essential for predicting the transport of using three-dimensional numerical simulations, performed using the sediment along the coasts, which is expected to be particularly useful MIKE 3 FM (HD) code. During the winter months, the wind-induced for the maintenance of the new port of the city of Patras, constructed in flow creats strong currents near the coasts and at the Rio-Antirio straits. 2010. Strong, tidal currents have been simulated to develop at the straits of Rio-, and when the wind is also blowing, nearshore gyres Our rather rudimentary understanding of hydrodynamic behavior of the develop, the sense of rotation of which is dictated by the wind Gulf is based mainly on three studies. The first study consists of direction. During the early summer months, starting from June, temperature and salinity measurements at several stations, current stratification develops and the flow becomes baroclinic. The speed measurements at selected points, and sea-level records at three simulations show that the currents induced by medium-strength winds, locations (Papailiou 1982). In the second study (Lascaratos et al. 1989) are restricted in the epilimnion, while the tidal action causes the a large number of satellite infrared images, taken over the gulfs of generation of internal waves at the straits of Rio-Antirio. Salient Patras, and Corinth (the latter two being the eastern features of the summer circulation, which were simulated, are strong continuation of the Gulf of Patras) were analyzed, giving a description upwellings and the development of a central cyclonic gyre. The of sea surface temperature features and their evolution in time, during upwellings occur along the northwesterly coasts of the Nafpaktos bay, the summer regime. The satellite data were interpreted using theories situated at the east of the Gulf of Patras, under southwesterly wind, and of wind-induced upwelling near capes, providing an attempt to explain to the south of Rio cape at the front of the city of Patras, under wind-induced movements and upwellings. In the third study, which is northeasterly wind. The numerical predictions have been validated rather more local in character, measurements were conducted mainly against satellite images,which closely confirm the simulation results. across the Rio-Antirio straits, at the eastern end of the Gulf, before the erection, during the year 2004, of the Rio-Antirio bridge (Antonopoulos KEY WORDS: Gulf of Patras, stratification, hydrodynamic et al. 1992, Hadjitheodorou et al. 1992). The objective of these circulation, internal waves, MIKE 3 FM (HD). measurements was to analyze the local dynamics of water surface elevation, density, salinity and temperature fields, taking into INTRODUCTION consideration the forcing provided by tidal action, river discharges and the wind action. The Gulf of Patras (also referred to, below, as the Gulf) and the adjacent eastern are among the busiest transport routes in In recent years, numerical circulation models have provided new Greece, because the port of the city of Patras connects opportunities for improving the quantitative description of the with the rest of Europe. These regions and particularly the hydrography and circulation of coastal water bodies. In the present northwestern part of the Gulf are expected to be the focus of attention paper, we study the three-dimensional baroclinic circulation in the in the coming years, since it has been found that in this area lies one of Gulf, using the 3-D finite volume code MIKE 3 FM (HD). In order to the largest oil inventories in southern Europe. As a consequence of the outline the specific characteristics of summer wind- and tide-induced on-going increase in industrial and transport activities in the wider area, circulation, we present, in counterpoint, the simulated summer and marine pollution will also be of concern. This, is in addition to the winter regimes, resulting from similar forcing, thus showing the current environmental pollution loads in the Gulf, which include seasonal changes in the hydrography of the region. continuous sources, such as municipal sewage discharge, and sporadic ones, such as oil spills and ship-related pollution which have been

740