Evolution of a buoyant outflow in the presence of complex topography: The Dardanelles plume (North Aegean Sea)

Abstract

The outflow of Waters of Black Sea origin (BSW) through the Dardanelles Strait is the strongest buoyant input for the North Aegean Sea (NAS). Two opposing flows exist across the Dardanelles exit: a lighter, upper layer outflow (BSW) and a denser, deeper layer inflow (waters of Mediterranean origin). This study examines the processes influencing the plume development and evolution. The complex topography of the receiving basin (NAS) plays a significant role on the preferred BSW pathways that are controlled by the buoyancy and wind forcing. A high-resolution numerical model, the NAS-HYCOM (Hybrid Coordinate Ocean Model), is implemented to perform process-oriented experiments that examine the relative role of the forcing factors and topographic effects. Three major pathways are identified. In the absence of wind, an anticyclonic bulge is formed inducing a Westward Jet that is topographically guided between two islands near the outflow. Topography also controls the development of a buoyancy-driven Coastal Current and a Rim Current along the North Aegean shelf areas. Comparison of model results to analytical calculations suggests that topography modifies the formation and the ballooning of the anticyclonic bulge, which are controlled by the outflow rate, the resulting stratification and Coriolis. Experiments also employ several wind directions and magnitudes in combination with different outflow characteristics. The study elucidates the importance of the Aegean morphology on the processes controlling the coupling to the Black Sea. The BSW are found to influence both deep and shelf Aegean basins, along their overall cyclonic pathway toward the eastern Mediterranean. Copyright 2011 by the American Geophysical Union.