The Gulf of Eilat/Aqaba: a natural driven cavity?

High-resolution ground-based radar observations of flow structures in the Gulf of Eilat/Aqaba, a nearly rectangular basin in the northern tip of the Red Sea, revealed an occasional and perplexing presence of a large (much of the domain) spatially coherent eddy with a lifetime of a day or so. Such coherent eddies are rare and appear only a few times a year, from November to April, and only when the wind is relatively calm. Most of the time the surface circulation in the northern gulf is chaotic and unorganized.

We use a combination of (1) a reduced-gravity, shallow water model within a rectangular domain and (2) a realistic 3D ocean general circulation model driven by wind stress derived from simulation using a regional atmospheric model, to explore the possibility that these eddies are driven by the external flow at the Gulf opening. In other words, we propose and explore the driven cavity approach to this geophysical phenomenon. While the lid-driven cavity has long been considered a benchmark problem in computational fluid dynamics, its oceanographic context has not been considered. Despite the additional effects of rotation and stratification, our modeling demonstrates that when the fluid within a cavity geometrically similar to the Gulf of Eilat is driven by the external current, an interior vortex can develop as in our observations.