A numerical modeling study on oceanographic conditions in the former Gulf of Tartessos (SW Iberia): Tides and tsunami propagation

Abstract

At least five catastrophic tsunami events have affected the Iberian Atlantic coasts during the last 7000 years. During this time, the former Gulf of Tartessos evolved towards the present marshland area, in the lower Guadalquivir valley (SW Spain). Ancient cultures flourished and vanished around this waterbody which, with its tidal dynamics, was an essential part of their living environment. A numerical modeling study on oceano-graphic conditions (tide and tsunami propagation) in the former Gulf of Tartessos has been carried out, in order to improve our insight on how they could have influenced the human activities in this area. The model solves the 2D depth-averaged hydrodynamic equations with appropriate initial and boundary conditions for tides and tsunamis. The model has been tested through simulation of tides under present bathymetry and of past tsunamis for which historical records exist. Then the bathymetry of the Gulf of Tartessos has been reconstructed for 2200 and 4000 years BP. The two main tidal semidiurnal and diurnal constituents have been simulated. Results indicate that they suffer a strong attenuation in the Gulf for both bathymetries, with significant currents only in its entrance. The known main active faults in the Gulf of Cádiz and the 1755 Lisbon source have been selected as case studies of tsunami propagation in the former Gulf of Tartessos. The 1755 Lisbon tsunami represented the worst case situation, and its numerical simulation has been subjected to several sensitivity tests. Results reveal negligible impacts for the inner shoreline of the Gulf of Tartessos, but severe damage could have been produced along the Atlantic coasts of SW Spain, from Cádiz to Huelva.