Indian Ocean Dipole affects eastern tropical Atlantic salinity through Congo River Basin hydrology

Abstract

AbstractThe Indian Ocean Dipole is associated with a pronounced sea surface temperature gradient between eastern and western Indian Ocean. Here, we describe a striking contrast in Congo basin rainfall, river discharge and Eastern Tropical Atlantic surface salinity linked to the recent strong 2019 positive Dipole event and strong 2016 negative Dipole event. The sea surface temperature gradient across the Indian Ocean during the 2019 positive event drove tropospheric circulation changes that led to an increase in moisture convergence and convection over the Congo basin and an increase in Congo River discharge that was later reflected in a decrease in eastern tropical Atlantic surface salinity in early 2020. Opposite tendencies were observed in association with the 2016 negative event. This sequence of linkages is shown to apply more generally to Dipole events over the past several decades and thus represents a source of predictability for forecasting Congo basin hydrology and eastern tropical Atlantic oceanic conditions.