ENSO-Driven Modulation of the Caribbean Subsurface Salinity Maximum

Yongfei Deng , Tianning Wu, Joseph Gradone, William Douglas Wilson, Travis N Miles, Ruoying He

This study identifies El Niño–Southern Oscillation (ENSO) as the primary driver of interannual subsurface salinity variability in the Caribbean Sea. Using 30 years of high-resolution, data-assimilative ocean reanalysis (1993–2022), we show that the Subsurface Salinity Maximum (SSM) closely tracks ENSO cycles: El Niño events correspond to a saltier and deeper SSM, while La Niña drives a fresher and shallower SSM, with contrasts of ~+0.028 to +0.054 g kg−1 in salinity and ~+10 m in depth. Two coupled mechanisms govern these shifts: local wind stress curl anomalies inducing anomalous Ekman downwelling or upwelling, driving vertical SSM displacements; and enhanced or reduced remote advection of Subtropical Underwater (STUW) from the North Atlantic Subtropical Gyre, delivering anomalous salinity into the SSM layer. These findings position the Caribbean as a critical node where Pacific climate signals are imprinted onto Atlantic hydrography, with implications for upper-ocean buoyancy and North Atlantic circulation and climate predictability.