Internal solitary waves (ISWs) in the NE South China Sea (SCS) are tidally generated at the Luzon Strait. Their propagation, evolution, and dissipation processes involve numerous issues still poorly understood. In June,2012, a novel method of seismic oceanography capable of capturing oceanic fine scale structures is used to study ISWs in the slope region of the NE South China Sea (SCS) by Dr. TANG Qunshu and his workgroup. It is the first time that they captured such strong dynamic processes of ocean surface using the seismic method. Near-simultaneous observations of two ISWs were acquired using seismic (Figure 1), satellite(Figure 2), and XBT measurements. During the seismic data acquisition, the survey geometry should be optimized in order to image the upper layer of the water column.
The workgroup of Dr. TANG found that there were two prominent near-surface ISWs on the seismic image in tandem. The vertical and horizontal length scales of the seismic observed ISWs are around 50 m and 1–2 km, respectively. Wave phase speeds calculated from seismic observations, satellite images, and water column data are consistent with each other. Observed waveforms and vertical velocities also correspond well with those estimated using KdV theory. Consistencies of the results are shown from mutual verification among seismic, satellite, and site observations. The results also suggest that the seismic reflection profiling, in conjunction with conventional hydrographic observations, could be an excellent method to study near-surface ocean processes such as ISWs.
This study was supported financially by the National Natural Science Foundation of China (NSFC, grants 41376023, 41176026, 41106008, and 91228202)and the Knowledge Innovation Project, Chinese Academy of Sciences(KZCX2-EW-Y040). The NFSC Open Cruise Project of Geophysics is highly appreciated.
This work entitled“Seismic, satellite, and site observations of internal solitary waves in the NE South China Sea”has been published in Scientific Reports.
Figure 1.(a) Seismic image of the water column in the NE SCS. Black triangles are the locations of XBT stations. Detailed structures in the two whiteboxes of (a) are expanded in (b) and (c), respectively.(Image by SCSIO)
Figure 2.Filtered MODIS image.The observed ISWs at 11:05 on 27 June2012 (local time, UTC 18:00) in a MODIS image (http://oceancolor.gsfc.nasa.gov). Two red squares mark the locations of ISW1 (left) and ISW2(right) when observed on the seismic image.(Image by SCSIO)