Numerical simulations of spreading of the Persian Gulf outflow into the Oman Sea

Abstract

Abstract.A three dimensional numerical model namely POM (Princeton Ocean Model) and observational data are used to study the Persian Gulf outflow structure and its spreading pathways during 1992. In the model, the monthly wind speed data were taken from ICOADS (International Comprehensive Ocean-Atmosphere Data Set) and the monthly SST (sea surface temperatures) were taken from AVHRR (Advanced Very High Resolution Radiometer) with the addition of monthly net shortwave radiations from NCEP (National Center for Environmental Prediction). The mean monthly precipitation rates from NCEP data and the calculated evaporation rates are used to impose the surface salinity fluxes. At the open boundaries the temperature and salinity were prescribed from the mean monthly climatological values from WOA05 (World Ocean Atlas 2005). Also the four major components of the tide were prescribed at the open boundaries. The results show that the outflow mainly originates from two branches at different depths in the Persian Gulf. The permanent branch exists during the whole year deeper than 40m along the Gulf axis and originates from the inner parts of the Persian Gulf. The other seasonal branch forms in the vicinity of the shallow southern coasts due to high evaporation rates during winter. Near the Strait of Hormuz the two branches join and form the main outflow source water. The results of simulations reveal that during the winter the outflow boundary current mainly detaches from the coast well before Ras Al Hamra Cape, however during summer the outflow seems to follow the coast even after this Cape. This is due to a higher density of the colder outflow that leads to more sinking near the coast in winter. Thus, the outflow moves to a deeper depth of about 500 m (for which Correspondence to: M. Ezam (ezam@srbiau.ac.ir) some explanations are given) while the main part detaches and spreads at a depth of about 300 m. However in summer it all moves at a depth of about 200-250 m. During winter, the deeper, stronger and wider outflow is more affected by the steep topography, leading to separation from the coast. While during summer, the weaker and shallower outflow is less influenced by bottom topography and so continues along the boundary.

Challenges in modeling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

“…13e and f for both WOA09 data and CM2.6 (model year 197), respectively. Figure 13e shows two separate tongues of salty water, one near the surface and one at the depth of ∼ 300 m. These salty water signals are consistent with the seasonal cycle of Persian Gulf outflow as discussed in Ezam et al (2010). On the other hand, CM2.6 shows one subsurface salty water signal from the northern part, which is deep and strong enough to result in weak stratification in the north to a depth of 250 m, as shown in Fig.…”

Physical Properties of Persian Gulf Outflow Thermohaline Intrusion in the Oman Sea

“…Vertical profiles starts from 100 and 150 meters depth, and increase to a depth of 250 to 300 m. Whereas in winter the outflow is at greater depth with respect to other seasons showing higher outflow density. In summer, as opposed to winter, Persian Gulf outflow that enters into Oman Sea is more unified because thermocline in Oman Sea is stronger than those for other seasons as [2] has observed.…”

“…All diagrams show a mass of warm and saline water between two cold and fresh water masses. In winter the outflow is at greater depth with respect to other seasons showing higher outflow density in winter [2]- [14]. …”

“…The average depth of the Persian Gulf outflow into the Oman Sea is about 250 -400 meters [2]. The outflow of the Persian Gulf, after entering the Sea of Oman near the break of the continental shelves, starts to sink towards the deeper part and mix with the surrounding waters as it reaches a buoyancy equilibrium depth of 100 -250 m. The thermohaline properties decrease in these areas due to strong mixing of the Persian Gulf outflow into the Oman Sea by the wind variability, bottom friction, breaking of the internal waves, until a depth of neutral buoyancy, about 220 meters [3] [4].…”

“…Heat and salinity fluxes and other parameters that are created by these lateral convection due to forcing as geothermal or climate can affect heat and salinity budgets [2].…”