The circulation of the Arabian (Persian) Gulf: A model study of its dynamics

The Arabian (Persian) Gulf is a semi-enclosed sea characterized by negative water mass balance caused by the aridity of the region. Its physical oceanography has not been investigated adequately. There is considerable uncertainty about the driving forces of the non-tidal currents in the basin. In order to investigate the effects of buoyancy and wind forcings and identify the dominant dynamics of the Gulf circulation system, modeling studies are undertaken. The two-dimensional model uses the full Navier-stokes and diffusion equations to study the vertical cross-section structure along the minor-axis of the Gulf. The three-dimensional primitive equations model simulates the three-dimensional current and salinity structures of the general water circulation pattern. Both models use an idealized topography and are forced by buoyancy at the Strait of Hormuz, evaporation at the sea surface, and the observed average uniform wind field of 5 m/s along the major axis of the basin.; The 2-D model gives the description of the vertical circulation pattern from the Strait up to the mid-length vertical cross-section of the Gulf. It also reveals the detailed aspect of the evaporative convection process and establishes an accurate measure of the vertical velocity. In addition, the 2-D model establishes the analogy between light water inflow and mass diffusion.; The 3-D model identifies the role of buoyancy and wind forces on the dynamics of the establishment of current and density structures of the Gulf. The isolated effects of topography, winds and stratification are also examined. A prominent mechanism in the dynamics of establishment of the Gulf circulation system is the excitation of short and long topographic Rossby waves by the density current. The short topographic Rossby waves, in particular, induce upwelling along the Arabian shelf stronger than the downwelling convection of the evaporation process. Therefore, density-driven flow alone may not be able to account for all the observed features of the circulation pattern. Solutions forced by both buoyancy and the average observed wind field compare favorably with the available field observations. Thus, wind forcing is an essential component of the Gulf circulation dynamics.