Simulated ocean dynamics and lagrangian trajectory analysis in the Andaman Sea

The Andaman Sea is a complex tropical basin significantly influenced by monsoonal forcing, which dictates regional circulation and water mass properties. This study utilizes a high-resolution (1/36º) CROCO ocean model and the Ichthyop Lagrangian tool to analyze circulation, thermohaline structure, and particle trajectories from 2015 to 2019. Findings indicate that monsoons drive substantial seasonal variability; the Northeast Monsoon promotes a northward flow of low-salinity water from the Malacca Strait, while the Southwest Monsoon facilitates saline Indian Ocean intrusion. Vertical analysis shows the thermocline fluctuating between 30 and 180 m, primarily influenced by Indian Ocean Dipole (IOD) events. EOF analysis revealed dominant annual periodicities of 341 days for temperature and salinity, while Lagrangian simulations identified particle retention along Sumatra during the Northeast Monsoon and westward export into the Indian Ocean during the Southwest Monsoon. Mean meridional volume transport was calculated at +0.32 Sv. These results provide a critical scientific basis for understanding regional biological connectivity and transboundary marine debris management in the Andaman region.