Integrating technology into a portable observatory
In the late 1990s, MBARI recognized the bright future for observatory science. Increasingly, the oceanographic community acknowledged that expeditionary research should be augmented by a new strategy of observatory research for a number of reasons. First, oceanographic processes are dominated by short-lived events: nutrient injections, plankton blooms, storms, earthquakes, etc. that are rarely captured during a research expedition. Second, the expeditionary mode of data collection is poorly suited to providing complete, comprehensive, and interdisciplinary data over long time periods, yet this is exactly what is needed to understand complex ocean systems. Despite the fact that there was wide agreement on these points, in the late '90s the oceanographic community was still in no position to implement observatory-style research, in which instruments and platforms are deployed long-term and collect data continuously.
This situation presented a clear opportunity for MBARI to help jump-start the community’s move to observatory science. In 1999, MBARI researchers laid out an ambitious plan for the Monterey Ocean Observing System (MOOS). The centerpiece of the MOOS effort would be a highly capable, transportable mooring that would provide power and communications from the ocean surface to the seafloor through an optical-electrical-mechanical cable.
The creation of this new deep-sea observatory was a long and challenging process that involved dozens of MBARI staff and required close coordination between engineers, scientists, ROV pilots, and the crew of the R/V Western Flyer. The success in large part is due to the efforts of the dedicated team, led by Keith Raybould and Mark Chaffey, that included many engineers and scientists who devoted their expertise to create a well-designed system that met the science requirements.
The Software Instrument Applications for MOOS (SIAM) team developed the systems software and wrote “instrument services” to adapt each instrument to the experiment protocol. The Shore Side Data System team provided archive services and tools for science users to access data from all the deployed instruments. Multidisciplinary science groups coordinated the deployment and collected and analyzed the scientific data.
All of the design work, prototyping, manufacturing, and testing culminated in 2006, when the MOOS mooring was installed outside of Monterey Bay in support of a major experiment to measure carbon transport to the deep sea via submarine canyons.The Shepard Meander Experiment, chosen as the first full field test of MOOS technology, was designed to identify and quantify the processes causing sediment to move into the deep sea. The existing paradigm is that deep-sea organisms live off organic matter that is produced in the overlying surface water and settles vertically to the seafloor. In contrast, recent investigations have shown that organic matter produced on land and transported off the continent into deep-sea canyons and fan channels may be much more important than previously realized for the nourishment of benthic communities.
The site selected for the experiment was in the Shepard Meander, which lies about 100 kilometers west of Moss Landing, at 3,450 meters deep in the active channel of Monterey Canyon. This site was selected for three reasons. First, it is far enough offshore to test the entire self-contained, yet portable, MOOS mooring technology, including over-the-horizon satellite communications technology. Second, it is easily reachable from Moss Landing by ship in case of technical problems. Finally, the site is located far enough down the canyon so that it is less likely to be disturbed by energetic sediment transport events that are now known to be common within the upper canyon. Given the amount of scientific equipment that has been sacrificed to extreme canyon-forming events further upslope, a more benign environment was deemed desirable for this first real application of MOOS technology.
The MOOS observatory was deployed in three steps. In the first phase, the observatory support group launched the surface buoy and the specialized anchor cable from the R/V Point Sur on June 29, 2006. Previous test moorings deployed from 2003 to 2005 had brought some system flaws and challenges to light. By the 2006 deployment, the designs of both the fiber-optic riser cable, which extends from the buoy on the surface to the seafloor, and the midwater flotation, which supports the cable, had been improved to make the system more robust based on the results from the earlier test deployments and destructive testing in an MBARI laboratory test facility.
In the second phase, after testing verified that this operation was successful, the R/V Western Flyer and ROV Tiburon with the MBARI cable-laying sled were used to connect a combined fiber-optic and power cable to the base of the mooring and to lay it approximately 2.5 kilometers along the seafloor to the first benthic instrument site on the canyon shelf, about 2 kilometers back from the edge of the canyon. This mission was more challenging than expected when the benthic cable formed “slinky-like” coils on the seafloor as it was laid. Due in large part to the perseverance and maneuvering skills of the Tiburon pilots, the job was completed in spite of the poor cable performance, a good example of the unique capabilities of MBARI, where all participants are united in achieving the mission objectives. The twisting of the cable was ultimately traced to a manufacturing defect in the cable construction.
Once the benthic cable was in place, the canyon-shelf instrument package was lowered by “benthic elevator” to the seafloor and connected using Tiburon, and electrical power was switched on from the mooring. In November 2006 the R/V Western Flyer/Tiburon completed the third phase of the installation with a redesigned benthic cable. Tiburon laid another 2.5 kilometers of cable from the flank instrument site, down the wall of the canyon to the second instrument site located in the center or axis of the canyon floor. This axis instrument node was then connected and powered. The Shepard Meander Experiment was the first successful installation of a seafloor observatory consisting of an interconnected array of benthic instruments.
The full payload enabled testing at the maximum design level for all of the hardware and software systems including the power system, the SIAM data collection system, the telemetry-to-shore system, and the shoreside data processing and archiving systems. Since the observatory installation, about two megabytes of data have been transferred to shore each day via satellite. These data are then processed and served up on the Internet.
The MOOS science experiment was designed to take full advantage of the large number and diversity of instruments the observatory can support. Seventeen separate science instruments on the surface buoy gather data to help estimate the biological productivity and vertical export of carbon from surface waters to the deep sea in response to variations in atmospheric forcing and ocean circulation. On the seafloor, the flank and axis instrument packages each contain five instruments for measuring suspended organic and inorganic matter, as well as two current meters for estimating the lateral transport of carbon and the influence of the submarine canyon. Two sediment trap moorings were also deployed as part of the experiment to measure vertical carbon flux and a lower water-column vertical profiler.
The data collected by this project indicate that relatively large volumes of organic-carbon-rich sediment have been transported out onto Monterey Fan in the last 100 to 200 years. While it has long been known that submarine canyons are the conduits for sediments to reach the deep sea, these data suggest that the importance of canyon systems in bringing organic material to nourish deep-sea organisms may have been significantly underestimated.
The MOOS observatory will continue to monitor the canyon for at least a year or two. It is likely, however, that most of the material moves through the canyon in episodic, energetic sediment transport events, rather than being carried along continuously. Geologists know little about the magnitudes and frequencies of these episodic events, even though evidence from the channels on Monterey Fan indicates that episodic sediment transport events have dominated sedimentation over the last 2,000 years. No significant sediment transport events have been observed in the Shepard Meander since the experiment began. But should such an event happen, the MOOS observatory will be there, waiting, monitoring, measuring, sampling, recording, and speeding the information shoreside in a way that no ship-based or manned expedition could ever hope to do. The age of observatory science has arrived.
MBARI Contributors to the Monterey Ocean Observing System: James Barry, Larry Bird, Mark Chaffey, Francisco Chavez, Jon Erickson, John Ferreira, Gernot Friederich, Kevin Gomes, John Graybeal, Andrew Hamilton, Kent Headley, Bob Herlien, Mike Kelley, Hans Jannasch, Brian Kieft, Gene Massion, Lance McBride, Ed Mellinger, Reiko Michisaki, Tom O'Reilly, Charles Paull, Wayne Radochonski, Keith Raybould, John Ryan, Karen Salamy, Brian Schlining, Rich Shramm, Bill Ussler, and Dan Wilkin.
|The engineering team for the MOOS science experiment at the Shepard Meander stands in front of the surface buoy before sending it out to sea. This group portrait does not show some of the scientists and ROV pilots who were integral to this ambitious project.
Image: Kim Fulton-Bennett (c) 2006 MBARI
- MBARI creates revolutionary deep-sea observatory
- The Shepard Meander expedition—a search for carbon
- MOOS test mooring returns to Monterey Bay
- Monterey Ocean Observing System