TIDAL DYNAMICS OF THE SOUTH-WEST LAGOON OF NEW-CALEDONIA - OBSERVATIONS AND 2D NUMERICAL MODELING

The purpose of this paper is to determine, with the aid of a two-dimen sional model, the depth-averaged tidal stream in the south-west lagoon of New Caledonia. A description based on field data is given first. C oastal sea level and open-sea data (bottom pressure, currents) are har monically and spectrally analysed. The first-order dynamics of this la goon are dominated by semi-diurnal tides. Except for the passes, diurn al tides and currents are weak, only the two tidal harmonics M-2 and S -2 are subsequently investigated. A numerical model is used to provide a coherent and dense picture of the tidal dynamics of M-2 and S-2 and their variability. The validity of the model is assessed by comparing its results with measured sea level and current data. Amplitudes and phase-lags of the M-2 tide increase from south to north. M-2 currents are maximum in the south and in the passes. S-2 amplitudes increase fr om south to north but slower than M-2. S-2 phases spread from north-we st to south-east. Using model results, the long-term movement of the w ater mass due to tidal influence is estimated by calculating the resid ual Lagrangian velocity. (C) Elsevier, Paris.