engleski

Characterising continental shelf waves in the Southern Adriatic Sea: from observational hints to a numerical modelling description

Continental Shelf Waves (CSWs) are oscillatory phenomena associated with modulations induced by continental margin morphology in the potential vorticity field. They are controlled by a combination of the bathymetric gradient and the current rotation, in the same way as planetary Rossby waves are controlled by the meridional modulation of the Coriolis parameter. Under favourable conditions CSWs can be triggered by a number of factors, such as intense vorticity injections from wind or bathymetric perturbations. Along the continental margin of the Adriatic sea, an epicontinental basin of the Mediterranean sea, the possible occurrence of CSWs has been theoretically assessed, but these pulsing features have never been observed up to now. In this work we combine observational data and numerical model fields for detecting the presence of CSWs along the Southern Adriatic Margin (SAM) and investigating their dynamics during an episode of dense water downflow in spring 2012. Starting from the observation of high-intensity velocity pulses with a period of approximately 2 days, we analyse the results of a high-resolution, ocean currents- waves coupled numerical modelling experiment reproducing dense water formation and migration in that episode. The properties and the extent of the perurbations are described in terms of their rotary spectral parameters and oscillation patterns, while their propagation along the continental margin is characterized by wave length and propagation velocity. The comparison of the resulting wave parameters against dispersion relations theoretically compatible with the SAM morphology show that the observed modulation was indeed related to a perturbation system propagating south-eastwards along the Italian coast as a train of CSWs along the shelf break and on the continental slope. This provides, to the best of our knowledge, the first evidence of the occurrence of such waves on the SAM. Results allow to infer that CSWs provide a significantJoint Assembly 2017, Abstract Book Page |1183 contribution to dense water flows off the continental margin, by advecting dense water masses and triggering downflow throughout the slope. This work paves the way to further investigations of these pulsing features, their implications on dense water dynamics and related impacts on benthic environments.

Adriatic Sea, waves, continental shelf

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