Satellite Observed Multisource Internal Tide Radiation and Interference in the Banda Sea

Both the semidiurnal and diurnal internal tides in the Banda Sea were investigated using multi-satellite altimeter data, through a combination of plane wave analysis technique and two-dimensional band-pass spatial filtering. The west and central Banda Sea are found to be dominated by semidiurnal internal tides, while the diurnal internal tides dominate the east. Multiple internal tidal sources were located at or nearby the Banda Arc, radiating significant internal tides inwards in complex interference patterns in the Banda Sea basin. The semidiurnal sources were situated on the northern and southern sides of the Banda Arc, emanating internal tides in opposite meridional directions. The semidiurnal tidal beams then experienced interference, shaping the heterogeneous energy fields in the west and central Banda Sea. The primary diurnal source was situated over the steep slope in the Aru Basin, with significant energy radiation westward and diffraction in the east Banda Sea. Based on the estimation of 27-year coherent satellite results, the total energy flux of mode-1 internal tides into the Banda Sea is about 4.82 GW, 58% contributed by semidiurnal tides and 42% by diurnal tides. This study represents the first observed mapping of the complex and inhomogeneous mode-1 semidiurnal and diurnal internal tidal energy fields over the entire Banda Sea. Furthermore, this study enables further characterization of tidal mixing properties and improvement of model mixing parameterizations in the Indonesian seas. The Indonesian seas, an internal tide hotspot, have attracted much attention recently. The magnitude and geography of internal tides in this area were mainly by numerical simulations. The lack of sufficient in situ observations hampers further understanding on their energy transfer and dissipation processes, as well as the realistic validation of ocean models. The satellite altimetry is by now a unique technique that can globally map internal tidal energy field, but its applications in marginal seas are very limited. In this work, we used the multi-satellite altimeter data to provide the first observational map of the semidiurnal and diurnal internal tidal radiation in the Banda Sea. Particularly, we revealed an east-west asymmetric internal tidal energy field in the Banda Sea, indicating its complex and inhomogeneous distributed nature. We further explored their multiple physical processes, including the interference, spreading, focusing and diffraction. The map we provided highlights the relatively important but previously overlooked significances of diurnal internal tides in the Indonesian seas. The map can serve as a basin-covered validation for many numerical simulations. Moreover, this method is applicable to other basins of the Indonesian seas, supporting further understanding of their internal tidal energy redistribution and tidal mixing parameterizations in ocean models. Multisource semidiurnal and diurnal internal tidal radiation from the Banda Arc is revealed by multi-satellite altimetryThe M2 multi-wave interference shapes the spatially inhomogeneous energy fields in the west and central Banda SeaAn energetic K1 beam radiates and spreads from the steep slope in the Aru Basin, diffracting westward to the east Banda Sea

Automated summary

This study uses multi-satellite altimeter data to observe, for the first time, the semidiurnal and diurnal internal tidal energy fields in the Indonesian Banda Sea. The study reveals the complex and inhomogeneous distribution of these internal tides and explores their physical processes. This research provides important insights for understanding and modeling tidal energy transfer and mixing in this region.