October 15, 2015
Instruments used in the Coordinated Canyon Experiment
The illustration below (not to scale) shows the locations and depths of some of the instruments researchers are placing in Monterey Canyon as part of the Coordinated Canyon Experiment. Each of these instruments is described in greater detail below. Click on the illustration to see larger version. Image: © 2015 MBARI.
Moored instrument arrays
Six moored instrument arrays are being installed at depths of 200 to 1,900 meters in Monterey Canyon. Instruments on each array are suspended up to 80 meters (260 feet) above the seafloor on cables with floats at the upper end (floats shown in orange on the illustration above). Instruments on the moorings will be used to monitor plumes of turbulent water that rise dozens of meters above the seafloor. These instruments include:
- Sediment traps to collect samples of suspended sediment (see photo at left)
- Acoustic doppler current profilers (ADCPs) that use sound waves to measure current velocities, sediment concentrations, and the sizes of particles in the water.
- Transmissometers that measure the murkiness of the water, which provides additional information on the concentrations and sizes of suspended sediment particles.
A vertical profiler is being suspended on a mooring at a depth of 1,800 meters in Monterey Canyon. This automated instrument package travels up and down a mooring line, collecting data on water properties and currents at different depths.
Benthic Instrument Node (BIN)
Near the outer edge of the study area, a benthic instrument node (BIN) is being deployed at a depth of 1,850 meters. This array contains instruments that measure current velocities, sediment concentrations, particle sizes, water temperature, salinity, turbidity, and oxygen concentrations.
Sediment transport event detectors (STEDs)
Two sediment transport event detectors (STEDs) are being placed on the floor of the canyon at 300 and 500 meters to serve as early warning devices, alerting researchers when sediment flows occur in the canyon. These relatively low-tech instruments look like large wind vanes, sitting upright on the seafloor. The vanes keep the STEDs facing into the near-bottom current. When the current reaches a certain pre-set velocity, it pushes on a paddle which in turn releases a float (the yellow rectangular object in the photo at left). The float rises to the surface and sends a signal to shore to alert researchers that a strong current has flowed past the STED.
Benthic event detectors (BEDs)
Not all of the instruments in the canyon are designed to stay in place during sediment-flow events. MBARI researchers are burying four beach-ball-like benthic event detectors (BEDs) in the canyon floor at depths of 200, 300, 400, and 500 meters. BEDs are “smart boulders” designed to be carried down-canyon along with sediment flows, recording the detailed movements of the sediment as they go. These devices can not only survive being pummeled and buried by underwater avalanches, but they can transmit their data to researchers even when buried beneath a meter or two of sediment.
Autonomous Monitoring Transponder (AMT)
The AMT array is being placed on the floor of Monterey Canyon at a depth of 300 meters. This array uses extremely sensitive tilt-meters and a pressure (depth) sensor to detect small movements in the seafloor.
Wave sensor (image not available)
Close to shore, just west of Salinas River State Beach, in about 30 meters of water, a wave sensor will let scientists know when large waves are arriving near the head of Monterey Canyon. Such waves move large quantities of sand along the shoreline and into the head of the canyon, sometimes triggering underwater avalanches.
Autonomous underwater vehicles
Researchers will use one of MBARI’s autonomous underwater vehicles, the D. Allan B. to make extremely detailed maps of the canyon floor every six months.
Wave gliders (essentially robotic, self-propelled surfboards) allow researchers to communicate with some of the instruments in the canyon. Radio signals from researchers on shore are transmitted to the Wave Glider, then converted into sound pulses that are relayed down to the instruments. The instruments “reply” using their own sound pulses, which are converted to radio signals and sent back to shore.
For additional information or images relating to this article, please contact: Kim Fulton-Bennett