Analysis of Characteristics and Turbulent Mixing of Seawater Mass in Lombok Strait

Abstract

The Lombok Strait, as one of the outlet straits, is part of the ITF route, which is directly adjacent to the Indian Ocean. There is a sill in the Lombok Strait, which is a place for internal wave generation. Leg-1 data from the Japan Agency for Marine-Earth Science and Technology in collaboration with the Agency for the Assessment and Application of Technology which is part of the Tropical Ocean Climate Study Expedition including CTD Yoyo and ADCP taken using ship vehicles R/V Kaiyo. CTD Snapshot from PUSHIDROSAL using the KRI Spica 934 vehicle part of the Opssurta Baruna Jaya 2 Expedition. Determination of seawater mass stratification with the criteria for the thermocline layer is ≥ 0.05 °C.m-1. Four types of water masses were identified, Java Sea, mixed seawater mass (Java Sea - ITF) which occurred diapycnal mixing, North Pacific Subtropical Water (NPSW) and North Pacific Intermediate Water (NPIW). The seawater mass stratification in the Lombok Strait based on temperature, salinity and density which are seen to follow the internal tidal pattern. The average values for energy dissipation and vertical diffusivity for each layer and replication were 5.73 x 10-7 W.Kg-1 and 3.67 x 10-2 m2.s-1 for CTD Yoyo and 2.25 x 10-6 W.Kg-1 and 7.38 x 10-2 m2.s-1 for CTD Snapshot. The value obtained is greater than the open ocean and straits in other studies. The high shear value confirms this in the thermocline layer. The Richardson gradient value> 0.25 is relatively constant in the thermocline layer.

Seasonal Water Mass Transformation in the Eastern Indian Ocean from In Situ Observations

“…Furthermore, water mass types were widely used to analyze the structure of the stratification and mixing in the water column [36]. In this study, the concepts and definitions were classified and defined the key properties of main water masses in the EIO based on WOD-18 data products by referring to previous findings (Table 3) [6,36]. Furthermore, the stability of the water column was analyzed based on the variable derivation of the Brunt-Väisälä Frequency (BVF), which can be calculated by the Equation [37][38][39]:…”

“…These physical processes produce strong and complex circulations in the eastern Indonesia Seas [4,5]. Alongside being part of the global thermohaline circulation, four main straits in the northern EIO (i.e., the Lombok Strait, Savu Strait, Ombai Strait, and Timor Sea) influence the turbulent processes in the water column and have developed specific characteristics [6]. The outflow circulations from the Indonesian Seas to the EIO regions primarily bring warm (>28 • C) and less-saline (~34.5 psu) water to the upper layer [7,8].…”

Deteksi dan Kuantifikasi Internal Wave Menggunakan Instrumen Broadband Echosounder SIMRAD EK80 di Perairan Padang Bay Bali

“…Gradien suhu vertikal berdasarkan sebaran suhu ialah 0,2624 ˚C/m. Nilai gradien suhu vertikal lebih besar dari 0,05 ˚C/m mengindikasikan adanya lapisan thermoklin [16,17] dan adanya pembentukan pycnocline pada kedalaman 14 meter hingga 28 meter selama periode pasang.…”