The University of Washington Applied Physics Laboratory designed and installed state-of-the-art Shallow Profiler Moorings to meet the science requirements for the Cabled Array component of the National Science Foundation’s Ocean Observatories Initiative (OOI). The moorings are some of the most technologically advanced in the worlds’ oceans.
The two-legged Shallow Profiler Moorings are installed at the cabled Slope Base (2900 m), Oregon Offshore (600 m), and Axial Base (2700 m) sites. Data from 18 instruments on each mooring have been sent live to shore since late Summer, 2015 when the science components were replaced as part of the schedule Operations and Maintenance VISIONS’15 cruise. Each mooring hosts a 7 ton, 12 ft across platform 200 m beneath the oceans’ surface. The moorings are connected to the Cabled Array high power and bandwidth fiber optic cables, which provide live command and control capabilities from the University of Washington Operations Center and real-time data flow (engineering and science) into the OOI Data Portal.
Each 12 foot across platform hosts a stationary, instrumented platform assembly and a winched science pod. A significant technological challenge for the winched science pods was that they required a long-lived, underwater optical slip ring on the turning winch for live communications-data transmission, as well as a rugged, controllable underwater level wind to let the, cabled buoyant science pod rise and descend in the water column. Remarkably, since late Summer 2015, each winched science pod has made >1600 cycles from 200 m water depth to ~10 m beneath the oceans surface. When weather is bad and sea states are high, smart controllers built into the system keep the profiler pods deeper beneath the surface. Missions for the profilers include 9 trips/day through the water column and automated step functions to stop the profiler pod at specific depths and turning of instruments on and off that require stationary measurements (e.g. CO2).
Instruments on the stationary platform assembly at Slope and Axial Base include pH, broadband hydrophone, CTD-dissolved oxygen, 5-beam Acoustic Doppler Current Profiler (ADCP), 150 kHz ADCP and a digital still camera. At the Oregon Offshore site, instruments on the platform include zooplankton, pH, PCO2, and CTD-dissolved oxygen sensors. Instruments on the winched science pod at all sites include CTD-dissolved oxygen, nitrate, pH, optical attenuation, spectral irradiance, PAR, PCO2, fluorometer, and a current meter- temperature sensor. Significant expansion capabilities are also built into the mooring assembly for addition of new technologies (e.g. flow cytometers, 3D imagers, DNA analyzers).
In concert, the instrument and platform capabilities allow high temporal and spatial measurements to be made that were never before possible with live data flow and command and control. Current instruments on the platforms were included to address science questions that vary from the impacts of climate change and ocean acidification, to the understanding of biological-rich thin layers within the oceans. Corresponding sensor arrays near the seafloor address hypoxia events, internal tides and flow of currents onto the shelf, and the release of methane from the seafloor into the ocean.