Observed internal tides in the deep northwestern Pacific by argo floats

This study aims to extract the observed internal wave signals in the northwestern Pacific from Argo floats with Iridium-telecommunication that can directly measure the hourly temperature, salinity and pressure near 1000 dbar. Vertical displacements and spectral features of internal tides can be interpreted from Argo float data. More than 10,000 parking-phase observations of 252 Argo floats were used to estimate their spatial-temporal characteristics. Vertical displacements attributed to internal tides exceeded 30 dbar near energetic sources, such as the Luzon Strait, Izu ridge, Mariana Arc and Palau. The observed internal tides feature both seasonal and spring-neap cycles corresponding to barotropic tidal variations. The diurnal and semidiurnal peaks in the energy spectra differed with latitude in related to different internal wave properties. Particularly, energetic local-trapped diurnal internal tides (topographic waves) occurred at 33°N near Izu Ridge, which is poleward of diurnal critical latitude. The internal tidal energy was calculated by theoretical fitting the vertical displacements from one layer to the full-depth water. The observed e-folding decay scales of the semidiurnal internal tidal energy were estimated as ∼550–950 km in the deep basin. The Argo parking data provide a unique view for observing the basin-scale pattern and energy sink of deep-ocean internal tides, which could supplement the widely-used surface altimetry observations and contribute to a more accurate parameterization of tidal mixing.