El Niño-Southern Oscillation drives major year-to-year changes in surface salinity across the Red Sea, with the strongest influence occurring in October.

How does ENSO affect the Red Sea’s salinity?

The researchers identified two atmospheric pathways linking ENSO to the Red Sea.

A tropical pathway sees ENSO-related changes alter atmospheric pressure over the Indian Ocean. Further north, atmospheric waves linked to ENSO create pressure changes over the Mediterranean region. Combined, these pressure differences alter winds over the Red Sea.

The winds affect salinity in two main ways. First, they control how much lower-salinity water enters the Red Sea from the Gulf of Aden through the Bab Al-Mandab Strait. Second, they affect evaporation differently across the northern and southern Red Sea, creating differing salinity changes across the basin.

To investigate these patterns over time, the team analysed a high-resolution hydrodynamic simulation of the Red Sea spanning 1997 to 2018, tracking monthly changes in surface salinity, evaporation and ocean currents. The simulation results were extensively validated against observational measurements from the Red Sea.

“Understanding these remote climate drivers gives us a much clearer picture of Red Sea dynamics,” says Junchuan Sun, lead author of the study and research scientist at KAUST. “In fact, by examining these changes at a monthly scale, we identified October as the time of year when ENSO-related changes in atmospheric pressure and winds have their clearest influence on Red Sea salinity.”

Read more at KAUST Discovery.