Shallow Profiler Moorings

State-of-the-art Shallow Profiler Moorings on the Regional Cabled Array (RCA) are located at the Slope Base, Endurance Offshore, and Axial Base sites, spanning coastal to blue-water environments. The Shallow Profiler Mooring is a custom built, two-legged mooring built by the UW Applied Physics Laboratory. Over 30,000 profiles have been completed since 2015, providing unprecedented, high-resolution data on processes operating in the upper 200 m of the water column. The mooring includes a 3.66 m-across, 7-ton platform at ~200 m water depth. Each platform, which receives up to 3 kW power, hosts a stationary, instrumented Platform Interface Assembly and a winched Science Pod that traverses the upper ~200 m of the water column. The Science Pod assembly includes a long-lived, underwater optical slip ring on the turning winch for live communications and 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.

A Shallow Profiler winched science pod and stationary platform, which hosts 18 instruments (e.g. pH, CO2, temperature, chlorophyll, zooplankton, nutrients, currents) undergoes testing in the School of Oceanography saltwater tank. The platforms will be deployed 600 ft beneath the oceans surface. Since 2015, three of these pods have made >27,000 profiles, providing unprecedented measurements of our dynamic ocean in real-time. Credit: D. Kelley, University of Washington.

The system utilizes the high-power and real-time two-way communication capabilities of the RCA to interface with an array of up to 18 science instruments. The operating system provides command and control capabilities that include implementation of predefined missions, switching of missions, and changing of mission parameters ‘on the fly’ with commands from the UW Operations Center. Profiler missions 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).

Engineering (including video) and science data are streamed back live to shore. Data channel capacity from the profilers exceeds 40 Mbps. Inputs such as 3D gyro, acceleration, pressure-depth, and deployed cable calculations are monitored to assure safe operations during any sea state. The profilers are designed to approach within 5 m of the surface. Wave height calculations, based on ‘worst case’ peak-trough conditions, are done when the profiler Science Pod is in the docking station. At five meters, or three times the wave height, the Science Pod missions are modified to prevent incursion into unsafe conditions in the overlying water column.

Instruments on the stationary platform assembly at Slope and Axial Base include pH, broadband hydrophone, CTD-dissolved oxygen (O2), 5-beam Acoustic Doppler Current Profiler (ADCP), 150 kHz ADCP and a digital still camera. At the OR Offshore site, instruments include zooplankton, pH, PCO2, and CTD-O2 sensors. Instruments on the winched Science Pod at all sites include CTD- O2, nitrate, pH, optical attenuation, spectral irradiance, PAR, PCO2, fluorometer, and a current meter- temperature sensor. Expansion capabilities are also built into the mooring assembly for addition of new technologies  (e.g. flow cytometers, 3D imagers, DNA analyzers).

A complementary set of seafloor instruments document near-bottom and water-column processes. Instruments include a 150-kHz ADCP, broadband hydrophone, optical attenuation, CTD-O2, and a HPIES (Horizontal Electric Field, Pressure and Inverted Echo Sounder). In addition, a geophysical–focused suite of instruments includes a broadband seismometer, low-frequency hydrophone, current meter, pressure sensor, and temperature.

In concert, the instrument and platform capabilities allow high temporal and spatial measurements to be made that were never before possible through 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 internal waves within the oceans. Because of mission control capabilities, instruments on the winched Science Pod are particularly well suited to examine, in real-time, biologically-rich thin layers 1-2 m thick or less, stemming from small scale chemical or hydrodynamic gradients. Corresponding sensor arrays near the seafloor address hypoxia events, internal tides and flow of currents onto the shelf.

 

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