Satellite Observed Diurnal Internal Tide Beams in the Northwestern Pacific Ocean

Abstract

Through a combination of plane wave analysis and two-dimensional band-pass spatial filtering, multisourced diurnal internal tide beams in the northwestern Pacific Ocean were identified and investigated using 27 years of multi-satellite altimeter data. Along the Pacific western boundary, both the strait-type and slope-type topographies were found to radiate mode-1 internal tides into the Philippine Sea basin. Satellite altimetry revealed that the Taiwan Island slope is a significant source for diurnal internal tides, which is distinct from the Luzon Strait. The diurnal internal tides in the basin exhibit a notable North-South asymmetry due to both propagation and interference. In the northern region, these tides display a long-range progressive nature, emanating mainly from the Luzon Strait and its vicinity. Conversely, in the southern region, the most significant source is the Miangas Ridge, with the secondary source at the northern sill of the Halmahera Sea. These tides converge around 600 km east of Mindanao, forming a nodal and anti-nodal interference pattern. This study presents an observed energy flux mapping for multisourced diurnal internal tides. It highlights slope-type sources along the ocean boundary in generating and shaping diurnal internal tide spatial pattern, a source topography type which is generally not favorable for semidiurnal internal tide generation among the global ocean.