Investigating the downwelling of Persian Gulf Water in the Gulf of Oman

In Gulf of Oman, the sinking of Persian Gulf Water mass has been reported. In the current study, the FVCOM ocean model has been used in 20 layers to investigate the phenomenon of downwelled Persian Gulf Water in the Gulf of Oman. The bathymetry of the simulated area (47˚-59.45˚E, 22˚-32˚N) was achieved from GEBCO-2019 by the resolution of 30 seconds. Triangular grid was generated in SMS. The open boundary fluctuations were also extracted from TMD. The temperature and salinity were obtained from the output of HYCOM (standard depths). Satellite data were used for the verification. The results showed the downward vertical velocity of Persain Gulf Water is higher in the area of the sudden depth change than the other parts in all seasons. This fact indicated the downwelled water was in a form of a spot. The rate of downwards penetration of water was different (winter: -2cm/s, spring: -1cm/s, summer: -1.2cm/s, autumn: -1.7cm/s). In summer, the salinity contours were very close to each other in the east of the Strait of Hormuz, or intense stratification. Therefore, the slope of the salt wedge was less. In winter, the calculated slope of the salt wedge (1.5×10^-1 degrees) was greater than summer (3.8×10^-2 degrees). The larger angle or slope of the salt wedge means the greater horizontal component of the weight of water (mgsinθ). It causes the displacement of saline water, and faster movement of Persian Gulf Water. Therefore, the water of the Persian Gulf moves faster to lower depths in Gulf of Oman in winter than summer