A HYCOM modeling study of the Persian Gulf: 2. Formation and export of Persian Gulf Water

The circulation and water mass transformation processes in the Persian Gulf and the water exchange with the Indian Ocean through the Strait of Hormuz are studied using the Hybrid Coordinate Ocean Model (HYCOM). Model results suggest that intruding Indian Ocean Surface Water (IOSW) is transformed into hypersaline waters with salinity >41 practical salinity unit by the fresh water loss in the northern end of the gulf and in the southern shallow banks. During wintertime, intense heat loss from sea to air leads to the formation of cold and saline waters both in the northern gulf and in the southern gulf. Dense waters formed in the southern gulf have higher salinity and spill into the axial deep trough of the gulf as a sporadic bottom outflow in winter, which leads to high-salinity pulses in the strait as observed, whereas in summer their buoyancy is increased due to heating and they are exported as a warm yet salty intermediate depth flow through the strait. Dense waters formed in the northern gulf propagate toward the strait along the axial trough throughout the year. Correspondingly, there are two branches of seasonal overturning circulation in density classes: the northern branch peaking in August with strength of 0.13 Sv and the southern branch peaking in February and December with strength of 0.08 Sv. These two branches outflow together feed a seasonally varying deep outflow through the strait with an annual mean volume transport of 0.12 Sv.