3:45 PM - 4:00 PM
[MIS24-02] Intensive XBT measurement reveals short-period gravitational internal wave in the sea: its impact on GNSS/acoustic seafloor geodetic survey
Keywords:acoustic ranging, GNSS/acoustic, internal gravitational wave, sound speed, seafloor geodesy
Then we conducted intensive XBT profiling of water column concurrently with GNSS/acoustic point survey in Kumano-nada, Nankai trough in 2016. Total 12 XBT-based temperature profiles with an interval of 10 minutes (lasting 2 hours), and a single XCTD-based density profile at the end were obtained, which provide fundamental information on the wave period. In the temperature profiles, we clearly identify up to 20 m of vertical oscillation of the water column shallower than 600 m. In the next step, we will estimate horizontal wavelength of this observed internal wave and calculate the local horizontal gradient of the net sound speed structure in order to be compared with apparent horizontal fluctuation observed in the concurrent GNSS/acoustic survey. These fundamental data in the water column will also contribute to understand small fluctuation in pressure at ocean bottom.
This work has been supported by SIP (Enhancement of societal resiliency against natural disasters) and Kakenhi 15H04228, 15K13557.