Water mass characteristics and estimation of turbulent mixing in Banggai Sea and Maluku Sea

Water masses can influence the mixing processes in the ocean. Temperature, salinity, and density data obtained from the CTD instrument during the BUDEE Expedition in September 2022 were used to identify the different water mass types and quantify their turbulence values. Turbulence was estimated using the Optimized Thorpe Method. The results revealed five types of water masses originating from the North Pacific, including NPSW and NPIW; from the South Pacific, including SPSW and SPSLTW; and from the Antarctic, identified as AAIW. The highest vertical eddy diffusivity value was found in the Banggai region, reaching 1.5 × 10⁻³ m² s⁻¹. In contrast, the Molucca and Seram seas showed much lower values, on the order of 10 < ⁻¹ > < ⁻¹ > m² s < ⁻¹ > ¹. The higher turbulence in the Banggai waters is likely due to its proximity to the Bote Strait and its relatively shallow topography. The lower turbulence in the Molucca and Seram Seas is attributed to deeper waters and limited interactions that induce water mass mixing. Overall, topography played a significant role in enhancing the mixing process by disturbing the stability of the water column.