Does Ocean Saltiness Influence El Niño?

Researchers from the Nicholas School of the Environment found that variability in ocean salt content affects El Niño intensity

Stormy ocean

This is a summary of a story that originally appeared on Nicholas School of the Environment.

Duke researchers found that ocean saltiness can influence the strength of El Niño, a climate phenomenon that can dramatically affect global weather. The results could inform development of more precise El Niño forecasts.

El Niño occurs every two to seven years, marked by wetter conditions in some parts of the world and drier weather in others. Existing research has overlooked the potential role of ocean salinity, or saltiness, in shaping El Niño events. Ocean salt is not uniform — some areas are saltier, some fresher, depending on rainfall, evaporation and other factors.

Variability in saltiness could potentially “influence ocean currents and thus climate phenomena like El Niño,” explains Shineng Hu, assistant professor of climate dynamics at the Nicholas School of the Environment, who oversaw the study.

Hu’s team used publicly available ocean data to identify global patterns in saltiness that have preceded major El Niño events over the past 65 years.

They found compelling correlations between saltiness and El Niño. Next, they used computer models to see if saltiness actually influences El Niño — for example, by making it more or less likely, or more or less intense. 

The results confirmed that certain patterns in ocean saltiness can fuel El Niño strength. During springtime in the western Pacific, a combination of fresher water at the equator and saltier water farther away promote eastward ocean currents. Those currents push warm surface waters east that fuel El Niño development, the authors explained.

This process can increase the intensity of El Niño by about 20% and make an extreme El Niño twice as likely, according to the study. More intense El Niño events can cause catastrophic flooding and severe droughts, among other disasters.

The findings indicate that ocean saltiness — information now consistently provided by satellite measurements — should receive more attention and be adequately incorporated into future El Niño forecast models, according to the authors.

Learn more about this climate research in the full story on Nicholas School of the Environment.