Field Test Results from Ellipsoid ADCP Buoy Moored at the Edge of the Gulf Stream

The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) and the Coastal Studies Institute (CSI) recently partnered to complete a successful 401 day field trial of a new subsurface ADCP buoy. The mooring system tested was new to CO-OPS, developed in response to several emerging current survey applications that require 6 to 12 months of current profile measurements in the topmost 30-50 m of a water column with depths ranging from 200-300m. Near surface current speeds at sites of interest reach 2-3 m/s. CSI has similar interest in measuring current profiles in the topmost, 50 m of the water column within the Gulf Stream, an area where currents may not be captured by bottom mounted ADCPs nor HF radar measurements. The mooring developed consists of commercial-off-the shelf (COTS) components. The 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 and CSI completed a long-term field demonstration of the system off the coast of North Carolina near the Gulf Stream in approximately 325 m of water, from May 2017 - June 2018. The system was successfully recovered following a 401 day deployment. An overview of the mooring system and preliminary field results were presented in a 2018 conference proceedings paper, shorty after the field test conclusion (MTS/IEEE OCEANS18, Charleston). This second conference paper presents additional data and further analysis, including model results to help interpret observed buoy depth excursions. Plans for continuing work guided by initial field test results will also be discussed.