The See‐Saw Radiation of Semidiurnal Internal Tides From the Lesser Sunda Islands

Abstract

The Lesser Sunda Islands (LSI) form a long chain over 1,000 km across major exits of the Indonesian Throughflow (ITF), through which Pacific waters enter the eastern Indian Ocean. The region hosts energetic internal tides and intense mixing that affect ITF water‐mass transformation, with implications for Indo‐Pacific exchange and global overturning circulation. Previous studies have focused on individual straits, leaving the island‐chain‐scale internal tide field poorly resolved. Using multi‐satellite altimetry, we provide the first coherent mode‐1 semidiurnal internal tide energy flux map across the LSI. A see‐saw radiation pattern emerges across the island chain, shaped substantially by the combined strait‐island‐basin topography during generation and propagation. In the west side, internal tides from the Lombok Strait interact with those from the Australian Northwest Shelf, forming an interference pattern in the basin. In the central region, local generation near Benteng Island replenishes the diffracted northward Sape beam, allowing it to propagate over 500 km into the Gulf of Boni, highlighting a unique strait‐basin‐island‐gulf long‐range‐traversed propagation. In the east side, the northward Ombai beam bifurcates and diffracts around the Wakatobi Islands, redirecting coherent energy into separate branches. Straits, islands, and basins combine to contribute to an asymmetric north–south internal tide radiation, with the southward semidiurnal coherent energy flux (2.5 GW) exceeding its northward component (1.8 GW). These results show how equatorial island chains organize and modulate multisource internal tides, advancing understanding of internal tide dynamics and energetics among global marginal seas and providing observational constraints for ocean and climate models.