Changes in Sea Salt Emissions Enhance ENSO Variability

Two 150-yr preindustrial simulations with and without interactive sea salt emissions from the Community Earth System Model (CESM) are performed to quantify the interactions between sea salt emissions and El Nino-Southern Oscillation (ENSO). Variations in sea salt emissions over the tropical Pacific Ocean are affected by changing wind speed associated with ENSO variability. ENSO-induced interannual variations in sea salt emissions result in decreasing (increasing) aerosol optical depth (AOD) by 0.03 over the equatorial central-eastern (western) Pacific Ocean during El Nino events compared to those during La Nina events. These changes in AOD further increase (decrease) radiative fluxes into the atmosphere by +0.2 (-0.4) W m(-2) over the tropical eastern (western) Pacific. Thereby, sea surface temperature increases (decreases) by 0.2-0.4K over the tropical eastern (western) Pacific Ocean during El Nino compared to La Nina events and enhances ENSO variability by 10%. The increase in ENSO amplitude is a result of systematic heating (cooling) during the warm (cold) phase of ENSO in the eastern Pacific. Interannual variations in sea salt emissions then produce the anomalous ascent (subsidence) over the equatorial eastern (western) Pacific between El Nino and La Nina events, which is a result of heating anomalies. Owing to variations in sea salt emissions, the convective precipitation is enhanced by 0.6-1.2 mm day(-1) over the tropical central-eastern Pacific Ocean and weakened by 0.9-1.5 mm day(-1) over the Maritime Continent during El Nino compared to La Nina events, enhancing the precipitation variability over the tropical Pacific.