Diapycnal mixing in the Banda Sea: Results of the first microstructure measurements in the Indonesian Throughflow

Models involving basin‐averaged T/S properties [ Ffield and Gordon , 1992; Hautala et al. , 1996] and barotropic/baroclinic tidal energy conversion [ Sjöberg and Stigebrandt , 1992] suggest that the Indonesian archipelago is a site of active mixing. This paper describes the first microstructure measurements made in the region. Aboard the R/V Baruna Jaya IV, we repeated 18 km legs centered on (6.5°S, 128°E), in the central Banda Sea, for two weeks during Oct/Nov 1998. With the Modular Microstructure Profiler, we gathered 519 profiles of potential temperature, salinity, potential density, pressure and kinetic energy dissipation rate. The cruise‐mean diapycnal diffusivity from 20–300 m is , similar to “open ocean” [ Garrett and Munk , 1975] values ( K ρ = 5.1 × 10 −6 m²s −1 ), and an order of magnitude below basin‐ and time‐averaged values obtained from the Ffield and Gordon [1992] and Hautala et al. [1996] models ( K ρ ≥ 1 × 10 −4 m²s −1 ). Sea‐surface temperature displays some evidence of a fortnightly modulation, interpreted by Ffield and Gordon [1996] as evidence for tidal mixing, but is uncorrelated with the dissipation rate just below the mixed layer.