4th International Submarine Canyon Symposium (INCISE2018)

5-7 November 2018, Shenzhen, CHINA

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This is the detail of In-situ observation of the subaqueous sand dunes at the upper slope of the northeast South China Sea

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Author
Yulong ZHAO
Co-Author(s)
Zhifei LIU, Yanwei ZHANG, Pengfei MA
Abstarct Title
In-situ observation of the subaqueous sand dunes at the upper slope of the northeast South China Sea
Abstarct Body
Subaqueous sand dunes are significant sedimentary and geomorphological features of the upper northern South China Sea continental slope. Herein we present in-situ observation re-sults of these subaqueous sand dunes, performed during the “KK1803” NSFC open cruise in April to May 2018. The remoted operated vehicle (ROV) “ROPOS” of the Canadian Scientific Submersible Facility (CSSF) was adopted to deploy/recover tripods and sand-dune markers, and to obtain high-definition videos and photos. It is observed that sand dunes of different amplitudes and directions are developed. The first-order sand dunes have wave length of ~ 200-350 m and wave amplitude of 5-15 m, extending roughly parallel to the shelf break of the northern South China Sea. Overlapped on the crests of these large sand dunes, the second-order sand ridges, generally 0.5-2 m wide and 0.1-0.3 m high, are developed. These sand ridges are generally parallel to the large sand dunes, and 5-20 m apart from each other. Asymmetry sand ripples of smaller scales, usually with wave length of 10-20 cm and height of 1-2 cm, are found over-lapped on both the first- and second-order sand dunes. According to the results of the ADCP equipped on the tripod, sedimentary dynamics of the sand dunes are strongly linked to the high velocity and suspended sediment concentration in the benthic boundary layer, triggered by activities of the internal solitary waves during spring tides. Such internal solitary wave activities cause, in average, a ~10-cm movement of the second-order sand ridges in 22 days.
INCISE Theme
Session 2: New ways to study submarine canyons: integrated programmes, new technologies and coordinated monitoring efforts
Presentation Type
Oral Presentation
Keywords
subaqueous sand dunes, remoted operated vehicle (ROV), internal solitary waves, in-situ observation

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