Hydrography and turbulent mixing in the Banda Sea inferred from Argo profiles

Abstract

Two Argo floats circulating in the Banda Sea from July 2017 until April 2019 were analysed to inspect the hydrography and vertical mixing properties. The maximum intrusion of Pacific thermocline and intermediate layers in the Banda Sea were identified during the Southeast Monsoon period with high temporal variability in the mixed layer (<100 m), where fresher and warmer waters are maximum during the transition season, from Northwest to Southeast Monsoon months. The monsoonal variability was also featured by the signature of downwelling and upwelling events, respectively. The upwelling rate of the colder water, isotherm 27° C, from 100 m to 10 m depth is ∼0.7 m day−1, from March to June 2018. The thickening of mixed layer occurred during the Northwest Monsoon months. The monsoonal gyre exists in the Banda Sea as shown by Argo floats trajectory. The highest rate of turbulent kinetic energy dissipation and vertical diffusivity of >10−8 m2 s−3 and [10−5–10−4] m2 s−1, respectively, were observed in the mixed layer and thermocline layer, with the decreasing trend deeper. The dissipation rate and diffusivity are comparable to previous direct estimates and models, suggesting the potential use of Argo float datasets to quantify vertical mixing in the future.