Direct Estimates of Turbulent Mixing in the Indonesian Archipelago and Its Role in the Transformation of the Indonesian Throughflow Waters
Taira Nagai, Toshiyuki Hibiya, Fadli Syamsudin
Abstract
Abstract Turbulent mixing enhanced in the Indonesian Archipelago (IA) is thought to influence the coupled ocean‐climate system through sea surface temperature cooling and water‐mass transformation. The present study describes the first extensive microstructure measurements conducted in the IA in 2019. A total of 120 profiles of turbulent energy dissipation rates showed that strong turbulent mixing was extremely localized in a few narrow tidal straits, where large density overturns and high vertical diffusivity associated with downslope jets were found. Far away from mixing hotspots, in contrast, observed vertical diffusivities were similar to typical open ocean values. Microstructure measurements together with a high‐resolution numerical simulation suggest that significant water‐mass transformation occurred within very short distances, O (10 km), in these narrow tidal straits through not only vertical mixing but also horizontal mixing enhanced by submesoscale topographic eddies.