In Situ Profiling of Eastern Arabian Sea Coastal Waters Using a New Autonomous Vertical Profiler

Abstract

The autonomous vertical profiler (AVP) presented here offers a fast, cost-effective, optimized approach to profiling in coastal waters. It consists of a hands-free, slightly buoyant, motor-driven in situ robot profiler that requires no operator skill or deployment gear, but fulfills the requirements of repetitive profiling of the water column. It uses standard oceanographic sensors to measure vertical structure at high resolution ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim}$</tex> </formula> 10 cm) in waters as shallow as 5 m and as deep as 200 m. The detailed engineering design, hydrodynamics, safety systems, endurance, and performance of the AVP relative to other profilers are covered in this paper. Proof-of-concept experiments in coastal waters present a clear picture, for the first time, of stable interactions between constant density contours and chlorophyll maxima in the waters of the Coral Island of Kavaratti (in the Lakshadweep Archipelago). The AVP has also been used in deep dives to 200 m in shelf regions of the Arabian Sea to record the presence of anoxic layers and phytoplankton existing in low-oxygen conditions.