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Santa Monica Bay Instruments Recovered

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'next generation' Geoprobe
'next generation' Geoprobe: The "next-generation" Geoprobe tripod back on deck. Its new downward-looking PC-ADP is the lowest instrument, beside Marlene Noble's left shoulder.
Instruments deployed in Santa Monica Bay by Coastal and Marine Geology (CMG) researchers last January (see Related Sound Waves story below) were recovered in late May. Chief scientist Marlene Noble and skipper Louis Zimm directed recovery of tripods and moorings at all three sites from aboard the Scripps research vessel Gordon Sproul in a textbook-perfect operation. The CMG crew included Jonathan Borden and Rick Rendigs from Woods Hole, and Tim Elfers, Joanne Ferreira, Dave Gonzales, and Chris Sherwood from Menlo Park. Everything was made easier by the calm seas and clear skies, although some of the crew were distracted by the booming 10-ft, 17-sec swells peeling across the Malibu beaches.

The crew left the Scripps Marine Facility in San Diego on the afternoon of May 23rd and steamed across crowded shipping lanes to Santa Monica Bay. The next day dawned clear and calm, and the first guard buoy was on board before breakfast. By four in the afternoon, three guard-buoy moorings and three tripods were aboard, sediment samples had been taken, and the Sproul was headed home a full day early.

Some new instrumentation was deployed on this cruise, including a downward-looking pulse-coherent acoustic doppler profiler (PC-ADP), intended to replace the array of aging electromagnetic current meters on the Geoprobe tripods. The PC-ADP appears to have performed well. A new acoustic backscatter sensor for sediments also worked continuously, providing 6 gigabytes of data for future analysis. These data will help scientists studying modern sedimentation and the fate of pollutants on the Los Angeles continental shelf.

Aboard the Gordon Sproul Aboard the Gordon Sproul: Guard buoy (foreground) and three tripods on the deck of the Gordon Sproul, with Harbor Island in the background. The three recovered tripods are, from left to right, the mini-pod, the "next-generation" Geoprobe, and the Geoprobe "classic." We are trying to modernize the Geoprobe, and the latest ("next-generation") model has a downward-looking PC-ADP (pulse-coherent acoustic doppler velocity profiler) for measuring current velocity in the bottom boundary layer. The old Geoprobe attempts the same task using electromagnetic current meters, which are difficult to calibrate and maintain. The mini-pod is a simple, rugged tripod that was used for deployment on the rocky shelf between Santa Monica and Redondo Canyons.

Once again, the operation was a success thanks to careful preparation by CMG technicians at the Woods Hole Field Center and the Redwood City Marine Facilities. As always, the professional seamanship, well-maintained facilities, and cheerful assistance provided by Scripps made the cruise efficient, safe, and enjoyable.

Related Sound Waves Stories
Tripods Deployed for Studies of Sediment and Pollutant Transport off Southern California
February, 2000

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Biscayne Nat'l Park Corals

Santa Monica Bay

Salvage for Science

Joint USGS—Monterey Aquarium Cruise

Outreach Teachers Tour WHFC

Students Tour WHFC

West Falmouth Harbor Water Sampling

Meetings World's Largest GIS Conference

Modeling Workshop

SC/GA Coastal Erosion Project

NOAA Data Integration

Staff & Center News Talk at WHFC

New Babies in Western Region

Publications New Coastal & Marine Geology Circular

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