Seasonal and Fortnight Variations in Internal Solitary Waves in the Indonesian Seas from the SWOT Measurements

Using the wide-swath sea surface height data from the 1-day repeat calibration/validation phase of the Surface Water and Ocean Topography (SWOT) mission, we explored fine-scale evolution of nonlinear internal solitary waves (ISWs) in the Banda/Molucca Seas in the Indonesian Archipelagos. Generated in the Ombai Strait and Lifamatola Passage through semidiurnal tide-topography interaction, respectively, ISWs in the Banda/Molucca Seas have a sea surface height amplitude of 10~20 cm and exhibit multiple wave packets with the leading wave crest followed by a series of rank-ordered secondary wave crests. Due to nonlinearity, the ISWs are observed to propagate northward at a speed faster than the regional mode-1 internal gravity waves and their amplitudes are modulated fortnightly following the regional spring-neap tidal cycle. On longer timescale, the observed ISW amplitudes are controlled by seasonal upper ocean stratification changes with a weaker stratification favoring a larger amplitude. By converting the SWOT-measured sea surface height data to the interior ocean pressure signals, we quantified the depth-integrated energy flux associated with the northward-propagating ISWs to be 5 kW m-1 and 2 kW m-1 in the central Banda and Molucca Seas, respectively. Comparisons with past studies indicate that the ISWs contribute to close to 100% and 40% of the tidally-induced, northward energy fluxes, respectively, across the Banda and Molucca Seas