4th International Submarine Canyon Symposium (INCISE2018)

5-7 November 2018, Shenzhen, CHINA

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This is the detail of Capturing hyperpycnal events in the benthic nepheloid layer of a submarine canyon in the wake of a typhoon

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Author
James T. Liu
Co-Author(s)
Ray T. Hsu
Abstarct Title
Capturing hyperpycnal events in the benthic nepheloid layer of a submarine canyon in the wake of a typhoon
Abstarct Body
In 2010 two moorings each configured with a CTD and an ADCP, one with an additional non-sequential sediment trap, were deployed in the head region of the Gaoping Submarine Canyon 3 days after the typhoon-induced peaks of the runoff and suspended sediment concentration (SSC) of the Gaoping River in southern Taiwan. Our data show a demarcation between tidal and hyperpycnal regimes in the temperature, salinity, and flow fields. The latter existed in the first 5 days out of the 18-day deployment, as defined by higher water density due to high SSC. Several lines of evidence indicate the presence of the tail end of a hyperpycnal turbidity current (HTC), including the retention of warm water near the canyon floor, high SSC, down-canyon directed residual flow and its vertical structure, and high terrestrial fraction (larger than 70%) of the organic particles carried by the flow. AMS δ14C dating results show that the river-sourced organic particles captured by the sediment trap were thousands of years old. The decreasing mass flux during the deployment is also an indication of a waning HTC. Our findings show that the vertical flow structure and the direction of the gravity-driven down-canyon HTC were retarded by the instantaneous up-canyon-directed tidal oscillations in the submarine canyon.
INCISE Theme
Session 1: Canyon processes in space and time (formation, evolution, circulation)
Presentation Type
Oral Presentation
Keywords
hyperpycnal turbidity current, tidal regime, typhoon, sediment trap, terrestrial sediment

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