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Baroclinic M 2 tidal circulation in Algeciras Bay and its implications for the water exchange with the Strait of Gibraltar: Observational and 3‐D model results
Author(s) -
González Carlos J.,
Álvarez Óscar,
Mañanes Rafael,
Izquierdo Alfredo,
Bruno Miguel,
Gomiz Juan J.,
Chioua Jamal,
López Laura
Publication year - 2013
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/jgrc.20404
Subject(s) - baroclinity , barotropic fluid , bay , outflow , geology , stratification (seeds) , inflow , oceanography , current (fluid) , annual cycle , climatology , seed dormancy , botany , germination , dormancy , biology
The M 2 tidal circulation in Algeciras Bay (Strait of Gibraltar) is analyzed using a 3‐D, nonlinear, baroclinic, hydrodynamic model, in conjunction with observed data series. Results show the influence of the density stratification on the vertical structure of the M 2 currents in Algeciras Bay, although its tidal dynamics shows major differences with respect to the Strait of Gibraltar. Whereas the M 2 currents in the Strait present mainly barotropic behavior, the baroclinic effects prevail in Algeciras Bay. A notable finding is the presence of a tidal M 2 counter‐current system between the upper Atlantic and the lower Mediterranean water layers within the Bay, with amplitudes of up to 25 cm s −1 . The interface between the two layers oscillates in antiphase relation with respect to the free‐surface elevation, with amplitudes of almost 20 m. The presence of the submarine Algeciras Canyon was found to be determinant in the three‐dimensional structure of tidal currents within the Bay, strengthening the baroclinic tidal regime of currents. This situation has quantitative consequences for the flow‐exchange processes between Algeciras Bay and the outer Strait, with rates 20 times higher than those obtained when considering only the barotropic behavior, as well as inflow/outflow lateral recirculation volumes during half a tidal cycle that account for more than 20% of the net accumulated volume. This flow‐exchange system was found to be affected by the nonlinear interaction processes between the first baroclinic period of resonance of Algeciras Bay and the M 2 tide.