El Nino’s long reach influences Red Sea salt balance

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.”

Why does changing salinity matter?

Salinity plays an important role in how ocean waters form layers, mix, and circulate. Changes in salinity can therefore alter the physical conditions experienced by marine organisms adapted to the Red Sea’s highly saline environment.

Furthermore, understanding these changes can support Red Sea coral reef conservation, marine environmental management and planning, as well as broader efforts to adapt to climate change.

“This study is critical in advancing scientists’ understanding of how climate variability in one part of the world can influence distant seas”, says Ibrahim Hoteit, KAUST Professor of Earth Systems Science and Engineering.

“With an unusually strong El Niño developing in 2026 and the potential for more extreme changes in the future, studying these connections is particularly timely,” Hoteit adds. “Our findings help us better understand how stronger climate events in the Pacific could translate into more pronounced changes in the region.”