Sea surface salinity extremes over the global ocean

Abstract

Sea surface salinity (SSS) extremes, characterized as events surpassing a certain threshold percentile, pose a threat to stenohaline organisms worldwide. This study presents the first global mapping of SSS extreme metrics and investigates their underlying drivers using daily reanalysis data. Our key findings have revealed that mesoscale eddies drive SSS extremes over most of the global ocean with peaks in duration ranging from 5 to 10 days and peaks in intensity ranging from 0.2 to 0.3 g/kg. Freshwater fluxes and mean currents are generally associated with the occurrence of prolonged and intense SSS extremes in tropical and extratropical oceans, respectively. Freshwater fluxes related to interannual climate modes contribute to the asymmetric distribution of high and low SSS extremes in the central Pacific Ocean and the western Indian Ocean. These results highlight the distinct impacts of different local drivers on the mean states of SSS extremes.