Mixing of North Pacific water masses in the Bali Sea

Abstract

As part of the Indonesian Throughflow (ITF) from western route, water masses in the Bali Sea are fed by North Pacific water masses. We examined the mixing strength in the Bali Sea which contributes to reducing the core layer S-max of the North Pacific Subtropical Water (NPSW) from 34. 8 – 35 psu in the source region to 34.5 psu in the Bali Sea. Using Thorpe method, we found the mixing strength in the Bali Sea is relatively low. The turbulent kinetic energy dissipation rate (ɛ) of O( 10-11 - 10-6 ) WKg-1 and density turbulent diffusivity (Kρ) are O (10-5 10-3) m-2s-1 were similar to typical open ocean values. However, mixing in the eastern region of the Bali Sea is relatively stronger than in the western region. Based on the critical Ri #, we found the Thorpe scale (LT) under Ri# < 0.25 in the eastern region, which is contrary to other parts. It indicated the turbulent mixing was dominantly caused by shear instability. Shear from the strong outflow of ITF towards the Lombok Strait and the reversal northward current in the lower layer forces a strong turbulent layer.