Why is the Red Sea more saline than the open ocean?

The Red Sea is significantly more saline than the open ocean primarily due to its location in a hot, arid climate where evaporation rates are extremely high, exceeding 80 inches per year. Unlike the open ocean, the Red Sea receives virtually no freshwater input from rivers, and rainfall in the region is scant.1

This high salinity is further accentuated by the sea's relative isolation from the open ocean. While there is an inflow of lower-salinity water from the Gulf of Aden through the Bab el-Mandeb Strait to compensate for evaporation, the lack of significant freshwater dilution allows salt concentrations to remain elevated. Surface salinity in the Red Sea can reach approximately 41 parts per thousand (psu), compared to the open ocean average of about 35 psu. Additionally, the deepest portions of the sea contain isolated pools of hot brine with extremely high salt concentrations, though these are distinct from the general circulation of the sea's surface waters.213