[AOS29-P07] Near-source detection of lowest and very high modes of internal tide in comparison with the JCOPE-T ocean circulation model
Keywords:internal tide, ocean bottom observation, seismic oceanography, ocean circulation
In order to examine the consistency of the above observational result with a state of art tide-resolving ocean general circulation model (JCOPE-T), we analyzed the synthetic bottom pressure records for this model using the same method with the same array configuration in the same period as for the observed data. The analysis detected a clear signal of eastward propagation of the M2 internal tide with amplitude and speed comparable to those of the observation (Fig. 1). By successively moving the hypothetical array upslope from the observational site, we found a location at which the propagating direction of the simulated internal wave is reversed. This location can be regarded as a generation site of the mode-1 internal tide. The simulated temperature fluctuation field tuned to the M2 frequency range shows how unique this location is. For example, the 11°C isotherm above this location undergoes semidiurnal vertical oscillation, the disturbance of which propagates both eastward and westward with an approximate speed of 1 m/s.
In this area, an extensive MCS (multi-channel seismic) survey was carried out in 2008.
The longest EW survey line passes right through our pressure gauge array. This legacy MCS data were reanalyzed to obtain ocean acoustic reflection images, which largely consist of reflections from high-mode tidal beams (vertical wavelengths around 30m). We compared the longest EW reflection profile to the simulated temperature fluctuation profile along the same line. Although the seismic profile delineates the spatial distribution of very high-mode tidal beams while the simulated profile describes the temperature disturbances due to very low modes of internal tide, their overall patterns commonly indicate a largest cell of the mode-1 internal tide with the source longitude at ~140°E and a half horizontal-wavelength of ~50 km. The wave field near the generation site appears to be rich in high-mode internal waves carried with and created from the lowest several modes of internal tides generated at the source.