[AOS22-02] Turbulent mixing in the Indonesian throughflow exit passages, the Lesser Sunda waters
Keywords:Indonesian throughflow (ITF), dissipation rates, Thorpe scale, Ellison scale, vertical mixing
Turbulent kinetic energy dissipation rates in the Indonesian throughflow (ITF) exit passages to the Indian Ocean, the Lesser Sunda waters, are inferred from archived CTD measurements and recent high-resolution time series data sets. Dissipation rates from archived data sets are inferred using an improved Thorpe scale method validated against microstructure measurements. Elevated dissipation rates ~[10-6-10-7] m2s-3 were observed in the straits, where internal tides are generated. Tidal variations seemingly influence the dissipation rates and diffusivities as has been suggested from the yoyo profiling data sets. The spatial pattern of dissipation rates inferred from the high-resolution 3D hydrodynamics model output of Nagai et al (2015) shows a general agreement with the observations in the location of the mixing hot spots and suggests that the M2 internal tide is the dominant factor driving the turbulent kinetic dissipation rates in this region. The bias in the model is possible due to the lack of representation of the ITF and mesoscale circulation in the model. We also investigate short temporal variability in one of the main passages in the region, the Lombok Strait, and found the turbulent kinetic energy dissipation rate inferred using Thorpe and Ellison scales of the order ~[10-6-10-7] m2 s-3, with enhanced values in the thermocline layer, possibly driven by shear instabilities. From this study, we underlined that the use of Ellison scale is a promising alternative for indirectly estimating the dissipation rate from high-resolution time series data sets.