On the response of a turbulent coastal buoyant current to wind events: the case of the Western Adriatic Current
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This numerical study focuses on the response of the Western Adriatic Current to wind forcing. The turbulent buoyant surface current is induced by the Po river outflow in the Adriatic Sea. Idealized and realistic wind conditions are considered by retaining the complex geomorphology of the middle Adriatic basin. In the absence of wind, the Adriatic Promontories force the current to separate from the coast and induce instabilities. Persistent 7-m s − 1 downwelling favorable northwesterly winds thicken and narrow the current. Instabilities whose size is ~10 km develop but ultimately vanish, since there is not enough across-shore space to grow. On the contrary, 7-m s − 1 upwelling favorable southeasterly winds thin and widen the current, and instabilities can grow to form mesoscale (~35 km) features. When realistic winds are considered, the same trends are observed, but the state of the sea set up by previous wind events also plays a crucial role. The turbulent regimes set up by different winds affect mixing and the WAC meridional transport. With downwelling winds, the transport is generally southward and mixing happens mostly between the fresher (S ≤ 38) salinity classes. With upwelling winds, the transport decreases and changes sign, and mixing mainly involves saltier (S > 38) waters. In all cases, mixing is enhanced when a finer 0.5-km horizontal resolution is employed.
KeywordsMesoscale variability Adriatic Sea Western Adriatic Current Instabilities Gargano Promontory Cape Transport Mixing
The research is supported by the National Science Foundation grant OCE0620661 (MGM, TMO), Office of Naval Research grants N00014-05-1-0094/95 (TMO, AG). A Rosenstiel School of Marine and Atmospheric Science Teaching Assistantship supported MGM. Insightful discussions on the numerical setup with Mehmet Ilıcak and on the wind data with Angelique Haza are also acknowledged. The Croatian Meteorological and Hydrological Service and Paul Martin are thanked for providing the wind data. All the simulations of this study were run thanks to the support of the High Performance Computing core at the Center for Computational Science of the University of Miami. The DART experiments were part of a Research Program lead jointly by the NATO Undersea Research Center and the Naval Research Laboratory at Stennis Space Center, in collaboration with 33 partner institutions whose contribution is gratefully acknowledged. The authors also thank Konstantin Korotenko and one anonymous reviewer for their comments and for improving the manuscript.
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