This is because the evaporation of the Red Sea is large, the bottom of the sea is high in salinity, and it is supplemented by seawater flowing from the Gulf of Aden through the eastern waterway of the Mande Strait, which dilutes the salinity of the seawater in the southern part of the Red Sea.

The Red Sea Basin is a part of the Asian-African Rift Valley, with a length of about 2100km, an average depth of 558m and a maximum depth of 2514m. According to the theory of submarine expansion and plate tectonics, it is considered that the Red Sea and the Gulf of Aden are the embryonic forms of the ocean.

No big river flows into the Red Sea. The precipitation is small, but the evaporation is large, the salinity is 4. 1%, and the annual evaporation is 2000 mm, which exceeds the precipitation. In summer, the surface water temperature exceeds 30℃, and the total average temperature is 22℃. Low rainfall and lack of fresh water injection lead to net evaporation and high salinity of 2050 mm per year.

The large annual evaporation contributes to the high salinity of the Red Sea, which also makes the water surface of the Red Sea lower than the surrounding waters and makes the Mande Strait current flow to the Red Sea. The salinity of seawater flowing through the eastern channel of the Mande Strait from the Gulf of Aden is much lower than that of the Red Sea, and the narrow terrain of the Red Sea can not fully mix the north and south seawater, so the salinity in the south of the Red Sea is obviously lower than that in the back.

Red Sea