337 / 2024-09-14 14:05:26

Significant salinity effect in the central equatorial Pacific conducive to ENSO development and complexity

ENSO,Ocean salinity,tropical Pacific

ENSO is well known for its significant impacts on global climate, yet it exhibits complex features including diversity and asymmetry. Among the various air-sea dynamical processes that govern ENSO evolution, salinity has been found to exert a positive effect by modulating vertical stratification; however, the potential impact of salinity on ENSO complexity remains unclear. Previous studies have demonstrated that salinity anomalies exhibit distinct zonal structures during different events, wherein its maximum anomaly is located further east in the central equatorial Pacific (CEP) during eastern Pacific El Niño (El Niño) compared to those located more westward during central Pacific El Niño (La Niña). Based on OGCM experiments, we found the salinity effects on ENSO temperature development is highly sensitive to its zonal location through modulating vertical entrainment and mixing. Notably, this positive effect reaches the strongest when the salinity anomalies located at around 170°W in the CEP. Such that these different zonal locations of maximum salinity anomalies contribute to stronger El Niño than La Niña, but also increasing the difference in intensity between the two types of El Niño by about 10%. Here using 19-year Argo date, we highlight the CEP(170°E-160°W, 5°S-5°N) as the location of positive salinity effects on ENSO. This is attributed to the large change in the mixed layer induced by salinity anomalies, but also nourished by a weak ILD change there during ENSO cycle. This study emphases the importance of salinity effects in the CEP during the ENSO cycle, which may have great prospects in improving ENSO modeling and forecasting skills.