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A new instrument system to investigate sediment dynamics on continental shelves |
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| Authors: | DA Cacchione DE Drake |
| Institution: | U.S. Geological Survey, Menlo Park, Calif., U.S.A. |
| Abstract: | A new instrumented tripod, the GEOPROBE system, has been constructed and used to collect time-series data on physical and geological parameters that are important in bottom sediment dynamics on continental shelves. Simultaneous in situ digital recording of pressure, temperature, light scattering, and light transmission, in combination with current velocity profiles measured with a near-bottom vertical array of electromagnetic current meters, is used to correlate bottom shear generated by a variety of oceanic processes (waves, tides, mean flow, etc.) with incipient movement and resuspension of bottom sediment. A bottom camera system that is activated when current speeds exceed preset threshold values provides a unique method to identify initial sediment motion and bed form development. Data from a twenty day deployment of the GEOPROBE system in Norton Sound, Alaska, during the period September 24 – October 14, 1976 show that threshold conditions for sediment movement are commonly exceeded, even in calm weather periods, due to the additive effects of tidal currents, mean circulation, and surface waves. |
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