Technology Demonstration of a Novel Seabed Resident Event-Driven Profiling System

The seabed resident event-driven profiling system (SREP) was deployed in the northeastern Arabian Sea for winter convention studies. SREP is an autonomous profiling system consisting of two parts: a stationary seabed unit and a positively buoyant tethered profiling unit (profiler). It offers a novel and optimized approach to profiling in coastal waters from close to seabed (14.63 m above seabed) to the sea surface. The seabed unit houses an underwater winch system, underwater acoustic modem, pressure sensor, low-power electronics, batteries and divinylcell hydraulic crush point foam for subsea applications. The profiler houses a suite of oceanographic sensors: conductivity– temperature–depth, DO, chlorophyll, PAR, underwater acoustic modem, low-power electronics, batteries and divinylcell hydraulic crush point foam for subsea applications. The underwater winch system on the seabed unit spools out and spools in the profiler throughout the water column. Data acquisition on the profiler is done during ascending. The profiler ascends gradually in the water column at an average velocity of 20 cm/s. The seabed unit and the profiling unit communicate using a pair of underwater acoustic modems operating at 18–34 kHz. SREP was developed to obtain time-series water column measurements of coastal waters during the summer monsoon season (June–September) when the sea wave and wind conditions are extreme, thus making it difficult to deploy profiling packages from the ship. A description of SREP and observations made during the field deployment are presented in this article.