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Santa Monica Bay Instruments Recovered
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'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.
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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:
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.
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August 2000
in this issue:
cover story:
Biscayne Nat'l Park Corals
Santa Monica Bay
Salvage for Science
Joint USGS—Monterey Aquarium Cruise
Teachers Tour WHFC
Students Tour WHFC
West Falmouth Harbor Water Sampling
World's Largest GIS Conference
Modeling Workshop
SC/GA Coastal Erosion Project
NOAA Data Integration
Talk at WHFC
New Babies in Western Region
New Coastal & Marine Geology Circular
August Publications List
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U. S. Department of the Interior | U.S. Geological Survey
previous story
