Vertical structure of the semidiurnal tidal currents at Camarinal Sill, the strait of Gibraltar

Abstract

The dynamical mode decomposition (DMD) technique is applied to the data of currentmeter and CTD measurements taken during the 1985–1986 Gibraltar Experiment and the 1989 survey so as to clarify features of the vertical structure of the M 2 and S 2 tidal currents at the Camarinal Sill. It is shown that in conformity with the inference made on the basis of the empirical orthogonal function (EOF) decomposition technique, these currents are mainly due to the M 2 and S 2 barotropic modes. At the same time the first three baroclinic modes are responsible not only for the vertical variability of the tidal currents but also for the velocity and density amplitude variances at semidiurnal frequencies. Certain quantitative discrepancies between the values of barotropic tidal current characteristics as deduced from DMD and EOF decomposition techniques are revealed. In order to eliminate these, new currentmeter data are required with a finer vertical resolution than those which are available. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS barotropic and baroclinic modes / tidal current / dynamical mode decomposition / Strait of Gibraltar