The Madden-Julian Oscillation imprint on the Indonesian Throughflow

Air-sea heat flux associated with the Madden-Julian Oscillation (MJO) affects sea surface temperature (SST) at intraseasonal timescales in some major basins of the Indonesian Seas (Napitu et. al., 2015). The MJO demonstrates seasonality and strongly projects on intraseasonal SST during boreal winter. Seasonal SST variations over the Indonesian Seas are also regulated by the Indonesian Throughflow (ITF), the flow of Pacific water into the Indian Ocean. Here, we investigate the impact of strong MJO events on the ITF variability during 2004-mid 2011. Observations at some ITF channels reveal that the MJO relaxes the ITF transport through two mechanisms: 1. Westerly wind bursts attributed to the MJO drives Ekman transport within the upper 50 m of the ITF passages, resulting in the weakening or reversing the ITF transport; 2. The MJO forced-oceanic Kelvin waves generated over the equatorial Indian Ocean penetrate into the ITF passages and propagate against and relax the ITF transport, a couple of weeks after the MJO’s westerly wind bursts cease over the Indonesian Seas. The first mechanism appears to cool SST, while the second one accelerates SST recovery over the Indonesian Seas. Moreover near-inertial motions are also evident in the ITF variability in the wake of the MJO events. This near-inertial variability increases sheared currents within the upper 100-m which potentially intensifies vertical mixing and prolongs SST cooling following the MJO passages.