Satellite-observed characteristics and prediction of internal solitary waves in the Maluku Sea

Internal solitary waves (ISWs) are frequently observed in the Indonesian seas, where strong tides, complex topography, and stratified water masses generate energetic internal wave activity. The Maluku Sea is a key passage linking the western Pacific, Celebes Sea, and Banda Sea, yet the long-term characteristics and predictability of satellite-visible ISW signatures remain insufficiently documented. Here we focus on surface manifestations of ISWs, rather than reconstructing their full subsurface dynamics, using MODIS imagery spanning 2002–2025, and SWOT KaRIn sea surface height anomaly (SSHA) data. The MODIS archive shows two main pathways of satellite-visible ISW wavefronts. The dominant branch originates near the Lifamatola Passage and propagates northward across the basin, whereas a weaker branch enters from the Celebes Sea. Wavefront lengths increase from tens of kilometers near the source region to hundreds of kilometers in the central basin, then become constrained in the northern trough. Matched Terra/Aqua image pairs indicate predominantly northward or northwestward propagation, with apparent phase speeds mainly between 0.5 and 2.5 m/s. SWOT observations reveal ISW-related SSHA signatures with daily and spring-neap modulation. These results indicate a statistical link between satellite-visible ISW signatures and tidal forcing, without directly validating subsurface amplitude, displacement, or energy flux. We further developed a two-stage framework for predicting satellite-visible ISW wavefronts. STEP1 predicts source-region wavefront masks from time- and tide-conditioned inputs, and STEP2 uses a ConvLSTM model to estimate subsequent propagation speed and direction. STEP1 achieved test-set F1 and IoU score of 0.831 and 0.711. STEP2 yielded speed MAE/RMSE/R² of 0.09 m s⁻¹/0.13 m s⁻¹/0.97 and direction MAE/RMSE of 3.0°/5.7°. The results show that historical satellite-derived wavefront geometry provides useful prior information for predicting surface ISW signatures, while the framework should not be interpreted as a complete subsurface dynamical model.