Subsurface ADCP Buoy for Near Surface Current Observations in 200-300m Coastal Waters

Several recent field applications at the National Oceanic and Atmospheric Administration (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) have required measurements of current profiles in the top 30m of a 200-300 m water column, for a 60-90 day duration. Maximum near surface current speeds at sites of interest range from 2-2.5 m/s. To address this emerging requirement, CO-OPS developed and field tested a subsurface, moored buoy system consisting of commercial-off-the shelf (COTS) components. The moorings topmost component is an ellipsoid, syntactic foam buoy, which houses an upward looking 300 kHz acoustic Doppler current profiler (ADCP). The ellipsoid buoy has lower drag than a spherical shaped buoy and significantly higher buoyancy than many COTS available streamlined buoys, allowing the ADCP to be positioned within the top 50 m of the water column when moored with adequate line length. CO-OPS very recently completed a long-term field demonstration of the system off the coast of North Carolina near the Gulf Stream in approximately 275 m of water, from May 2017 - June 2018. Details of the mooring design along with initial field test results will be presented.