MODELLING OF TIDAL DYNAMICS AND MIXING OVER THE NATUNA WATERS

• Main Author: Ramadhia Moussafy, Ivannsa
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/51006
• Institution: Institut Teknologi Bandung

Study of tidal dynamics over the Natuna waters is required to support the utilization of marine fisheries potential. Tides may induce vertical mixing so the nutrients for marine life necessities in the bottom layer can be lifted to the the surface. This study examines the characteristics of tidal dynamics, discovers location, and strength of tidal mixing over the Natuna waters using 3D hydrodynamics model Regional Ocean Modelling System (ROMS). The astronomical tides harmonic constants data as the input of simulation were obtained from The Oregon State University TOPEX/Poseidon Global Inverse Solution Model Version 7.2 (TPXO 7.2). Simulation was run for 45 days (2 October–15 November 2007). Tidal mixing analysis was based on the thickness of bottom boundary layer (BBL) which was calculated using the root mean square (RMS) of bottom friction velocity. The simulation results show that the Natuna waters is dominated by the K1 tide, which ranges from 40–60 cm (North Natuna Sea) and 30–70 cm (Natuna Sea). Meanwhile, M2 tide is more dominant especially in the South Natuna Islands and northwestern Kalimantan. The tides in Natuna waters flow from the South China Sea (SCS). The highest maximum depth averaged (2D) velocity of K1 tidal current is located in the South Natuna Islands region with the velocity up to 65.33 cm/s. K1 tide induces strong tidal mixing, which can lead to effective vertical mixing of water masses in the Laut Island, Bunguran Island (on the northwest and southeast side), Midai Island, South Natuna Islands, and Sambas (northwest Kalimantan). The bottom boundary layer (BBL) thickness due to K1 tide in these waters reach > 29 m so that BBL can cover the entire depth of the water and a perfect vertical mixing due to tides may occur.