engleski

Observation and modeling of periodic upwelling/downwelling in the Adriatic Sea

An experiment, carried out in the Adriatic between February and September 2006, showed that subsurface temperature oscillations, characterized by the 24, 12 and 8 h periods, were strong at the Lastovo island thermistor station and that corresponding baroclinic current variability was largest at a nearby ADCP station. Wavelet spectral analysis of meteorological and oceanographic time series revealed that the sea/land breezes were responsible for the periodic interchange of upwelling and downwelling in mid-July 2006, with the relatively weak morning breeze corresponding to thermocline reaching the deepest point, the relatively strong (up to 10 m/s) afternoon breeze coinciding with thermocline being close to the sea surface. The range of thermocline variability surpassed 20 m. A simple straight-coast, reduced-gravity model reproduced the observed phases but underestimated the corresponding amplitudes, probably because it did not allow for the resonant excitation of internal Kelvin waves traveling around the island and the nonlinear interaction of various wind-driven constituents. Further modeling addressed these issues, and also enabled the other spots at which diurnal upwelling/downwelling occurs and from which higher-frequency inertia-gravity waves emanate to be detected.

Adriatic Sea; upwelling; downwelling

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