Why does the Persian Gulf have high salinity?

The Persian Gulf experiences high salinity primarily due to a combination of high water temperatures and a limited influx of fresh water.1

The region's climate leads to significant evaporation, which consistently exceeds the volume of fresh water provided by rivers such as the Tigris, Euphrates, and Karun. Because the rate of evaporation is so high, the remaining water becomes increasingly concentrated with salt.1

This process creates a distinct circulation pattern: as surface water enters from the Indian Ocean, it undergoes evaporation, becomes denser, and eventually sinks to flow back out into the ocean beneath the incoming surface currents. These conditions are so extreme that they lead to the precipitation of sodium chloride and calcium sulfate, contributing to the formation of coastal salt flats known as sabkhas.12