Data Collection and Applications of Seafloor Water current Velocity

In the measurement of water current velocities, sound waves are commonly used to detect the Doppler effect caused by small scattering particles. The widely known Acoustic Doppler Current Profilers (ADCPs) operate based on this principle (Gould et al., 2001). Although ADCPs are widely used for measuring water current velocity, single-point current meters are considered a better choice for precise and continuous measurements of near-seafloor water current velocity.

In this study, a single-point current meter (Aquadopp-6000m Current Meter) was mounted on the Yardbird-BB OBS (Lin et al., 2024) to form a Seafloor Current Meter (SCM). The SCM was used to measure and record water current disturbances above the OBS seismic sensor. The data collected by the SCM can be used not only for analyzing the overall OBS orientation, the time of contact with the seafloor, the moment the seismic sensor detached from the A-frame and settled onto the seafloor, and the sound speed, temperature, and pressure profiles during the instrument's descent, but also for broader applications.

By increasing the sampling rate to 1 sps, the continuous observation data can be analyzed alongside OBS data to study the relationship between background seismic noise and seafloor current velocity, as well as changes in seafloor current velocity before and after seismic events. Moreover, atmospheric pressure changes—occurring even thousands of kilometers away before a typhoon forms—can affect seawater pressure, seafloor current velocity, and subtle variations in seafloor temperature, which in turn influence ocean sound speed.

This study analyzes and discusses SCM data collected in the northeastern offshore waters of Taiwan, at the western end of the Okinawa Trough..

Reference:

Gould, J., B. Sloyan, and M. Visbeck. (2013). In Situ ocean observations: a brief history, present status and future directions. In, G. Siedler, S. Griffies, J. Gould, and J. Church. (eds.) Ocean Circulation and Climate: A 21st Century Perspective. 2nd Ed. (HASH(0xa0a5e98), Oxford, GB. Academic Press, pp. 59-82. https://eprints.soton.ac.uk/358924/

Lin, C.R., Y.C. Liao, C.C. Wang, B.Y. Kuo, H.H. Chen, J.P. Jang, P.C. Chen, H.K. Chang, F.S. Lin and K.H. Chang. (2024). Development and evaluations of the broadband ocean bottom seismometer (Yardbird-BB OBS) in Taiwan. Terr Atmos Ocean Sci. 35, 4. Doi: https://doi.org/10.1007/s44195-024-00062-w