Testing High-Resolution Profiling Instruments for Studying Sediment Movement Near the Sea Floor

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Testing High-Resolution Profiling Instruments for Studying Sediment Movement Near the Sea Floor

By Marinna Martini
September 2003

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Testing the Pulse Coherent Acoustic Doppler Profiler and Acoustic Doppler Current Profiler off the dock
Above: Testing the PCADP and ADCP off the dock to determine the best setup. Steve Ruane is in the background.
Below: Transporting the tripod on the research vessel Asterias. Sensor heads of the four tested instruments (labeled) extend below the tripod's superstructure.

U.S. Geological Survey (USGS) scientists Chris Sherwood, Jon Borden, Joanne Ferreira, Jessie Lacy, Steve Ruane, Marinna Martini, and Amit Bohara have had fun in the sun with acoustic instrumentation this summer. First at the dock in Woods Hole, MA, then at the Woods Hole Oceanographic Institution (WHOI)'s Coastal Observatory off Martha's Vineyard, the gang tested several acoustic-profiling systems that marine geologists use to study sediment transport at and near the sea floor. Deployed were the following:

a Sontek Acoustic Doppler Velocimeter (ADV), which uses sound waves and the Doppler effect to make very accurate, high-frequency measurements of water velocity at a single point above the sea floor;

a Sontek Pulse Coherent Acoustic Doppler Profiler (PCADP), which uses sound waves and the Doppler effect to measure water velocity at numerous points above the sea floor, to obtain a vertical profile showing how water velocities vary with height above the bottom;

an RD Instruments' Acoustic Doppler Current Profiler (ADCP) in a pulse-coherent mode, which also uses sound waves and the Doppler effect to measure water velocity at numerous points above the sea floor; and

an Aquatec Aquascat Acoustic Backscatter Sensor (ABS), which uses sound waves to measure vertical profiles of suspended-sediment concentration.

We deployed the instruments at WHOI's Coastal Observatory, mounted on a bottom-tripod frame borrowed from Peter Traykovski at WHOI. The test is part of an ongoing, joint effort between WHOI and the USGS to characterize errors in these instruments and develop calibration techniques.

Amit is a Summer Student Fellow in Oceanography at WHOI working with Chris Sherwood this summer on the calibration of the ABS. Amit is a student at Gustavus Adolphus College in Minnesota and is originally from Nepal. The USGS' Woods Hole Field Center is designing a new low-flow-disturbance tripod frame, similar to the one shown, for near-bed high-resolution profiling.

Woods Hole Field Center
U.S. Geological Survey (USGS), Woods Hole, MA

Martha's Vineyard Coastal Observatory
Woods Hole Oceanographic Institution (WHOI)

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September 2003

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in this issue: cover story:
Ancient Landscapes Beneath South Carolina Beaches

Tracking Hawaiian Coral Larvae

Suspended Sediment in Hawaiian Waters

Sediment Movement Near the Sea Floor

Gulf of Mexico Fishery Management Council

Helping Spadefoot Toads in California

ESRI User Conference

Diving Into Coral Disease

September Publications List