Horsch, G.M. and Fourniotis, N.Th., 2017. Wintertime tidal hydrodynamics in the Gulf of Patras, Greece.

Three-dimensional numerical simulations have been applied to simulate the winter barotropic hydrodynamic response that develops in the Gulf of Patras due to tidal and wind forcing. The simulations were performed using the code MIKE 3 flexible mesh hydrodynamic module. They reproduce already-known features of the tidal flow entering the Gulf of Patras from the Ionian Sea, such as reflection of the tidal wave at the Rio-Antirio Straits and the cove of the Bay of Nafpaktos. Furthermore, details of the flow structure are revealed, such as the gyre that develops during the transition from ebb to flood tide in front of the Messolonghi Lagoon and the gyre in the Bay of Nafpaktos from flood to ebb. The action of prevailing winds on tidal circulation is to create strong nearshore currents, which dictate the sense of rotation of gyres that develop nearshore at both the northern and southern shores of the gulf, when the wind opposes the tide. The exchange flow, which develops between the Gulf of Patras and the adjacent Nafpaktos Bay, was found to be dominated, in general, by the tide, rather than by the wind; this nevertheless creates a lag in exchange flow when the wind opposes the tide. Finally, tidal circulation was found to create upwellings during the wintertime regime, reported herein for the first time, at the same locations in the Gulf where upwellings are known to develop in the summertime baroclinic flow, although not under the same wind conditions.