On the Origin of a Chain of Eddies in the Gulf of Eilat/Aqaba

Abstract

he Gulf of Eilat/Aqaba is a terminal, elongated basin that exchanges water with the northern Red Sea via the Straits of Tiran. This study used energy budgets of mean kinetic energy (MKE) and eddy kinetic energy (EKE; differentiated by a simple horizontal averaging filter), instability analysis, and numerical simulations to study the horizontal circulation of the gulf, which is characterized by the existence of a chain of eddies along its main axis. The kinetic energy is predominantly in the form of EKE. Energy conversion between MKE and EKE is negligible where the main sources for both energy reservoirs are the conversions from the available potential energy (APE). This term is balanced by the work done by pressure at the straits in case of MKE and by dissipation in the case of EKE. The MKE balance represents the coupling between the exchange flow at the straits and the wintertime dense water formation. The dense water exits through the straits while sinking adiabatically along the gulf. The strong variation in the shoreline/bathymetry triggers a baroclinic instability that enhances the eddy activity in the gulf. Thus, the baroclinic instability is an effective mechanism that transfers energy from the APE to the EKE. The EKE?APE conversion term involves vertical adiabatic motions that occur through the upwelling of relatively warm water in anticyclonic circulation regions and downwelling of colder water in adjacent regions with cyclonic circulation. Through these processes, the horizontal circulation is powered by the energy transferred from the APE. This explains the coupling between the temperature gradient and the eddy formation along the gulf.