Buoyancy-Driven Circulation in the Red Sea

Ping Zhai, Ph.D., 2014
Amy Bower and Lawrence Pratt, Co-advisors

This thesis explores buoyancy-driven circulation in the Red Sea, using a combination of observations, as well as a numerical modeling and an ad hoc analytical model. Observations of hydrographic data and chlorofluorocarbon-12 suggest that the Red Sea Overflow Water (RSOW) is formed through open-ocean convection in the northern Red Sea. Walin’s method indicates that vertical diffusivity is required to close the transport budget of RSOW. The thesis also studies buoyancy-forced circulation in an idealized Red Sea. By including β-effect and a linear buoyancy forcing, the resultant mean Red Sea circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In mid-basin, the northward surface flow crosses from the western boundary to the eastern boundary. The mechanism that controls the crossover of boundary currents is further explored using an ad hoc analytical model based on PV dynamics. It suggests that the competition between advection of planetary vorticity and buoyancy-loss related term determines the crossover latitude. The thesis also investigates three mechanisms that account for eddy generation in the Red Sea, by conducting a series of numerical experiments. The three mechanisms are: i) baroclinic instability; ii) meridional structure of surface buoyancy loss; iii) cross-basin wind fields.