Abstract:
The seafloor topography of the Andaman Sea is complex. Its tectonic basins, island chain systems, straits, and steep slopes provide favorable dynamic conditions for the generation of internal tides, and also determine the high variability of the spatio-temporal distribution of internal tides. To enhance the understanding of the dominant mode-1 M
2 internal tides in the Andaman Sea, this study is based on the multi-source satellite altimetry datasets (including Jason-2/3, Sentinel-3, HY-2A/B, SARAL/AltiKa, 2014–2023), HYCOM temperature and salinity data, and GEBCO_2023 bathymetric data, adopting a plane wave fitting method to analyze the distribution characteristics of the mode-1 M
2 internal tide waves in the Andaman Sea. Results show that prominent active regions of these internal tides are primarily located distributed in the central Andaman Basin, southern Great Channel-Ten Degree Channel tectonic zones, northern shelf margins, and the coastal waters off northern Sumatra. The large amplitude areas exhibit significant spatial coupling characteristics with steep topographic features (e.g., the Great Channel Fault Zone and Andaman Mid-Ridge), confirming the critical controlling role of seafloor topography on internal tide generation and energy amplification. Seasonal distributions reveal stronger amplitudes and energy fluxes in autumn/winter and weaker signals in spring/summer: the average amplitude in autumn reaches 17.6 mm (14.5 mm in winter), significantly higher than those in summer (12.1 mm) and spring (8.3 mm). Energy flux estimation shows that the average intensity is 205 kW/m in autumn, which is 2.0, 2.4 and 5.2 times that in winter (100.5 kW/m), summer (85.0 kW/m), and spring (39.7 kW/m), respectively. This spatio-temporal difference is caused by the effects of local topographic forcing, such as the continental shelf slope fold zone and the strait constriction effect. It is also affected by the seasonal evolution of stratification. In autumn, enhanced stratification promotes energy conversion. In winter, the deepening of the mixed layer suppresses baroclinic internal tides. In spring, the lag in the reconstruction of the thermocline reduces the conversion efficiency. In summer, Ekman pumping destroys the stratification and suppresses energy focusing. Additionally, it is influenced by the circulation modulation driven by the monsoon. Previous studies have conducted limited comprehensive analyses of the multi-scale spatio-temporal distribution of M
2 internal tides in the Andaman Sea. This study systematically reveals the multi-scale spatio-temporal distribution patterns of M
2 internal tides in the Andaman Sea, providing critical observational evidence for clarifying the internal tide energy transport pathways, mixing process, and their regulatory mechanisms on marine ecosystems in this region.