The Oceanic Remote Chemical/Optical Analyzer (ORCA)—An Autonomous Moored Profiler

Abstract

An autonomous, moored profiler [the Oceanic Remote Chemical/Optical Analyzer (ORCA)] was developed to sense a variety of chemical and optical properties in the upper water column. It is presently used to monitor water quality parameters in South Puget Sound?a largely undeveloped area subject to extensive future urbanization. ORCA has three main components: 1) a three-point moored Autonomous Temperature Line Acquisition System (ATLAS) toroidal float; 2) a profiling assembly on the float with computer, winch, cellular system, meteorological sensors (wind, temperature, humidity, irradiance), solar panels, and batteries; and 3) an underwater sensor package consisting of a Seabird CTD profiler, YSI dissolved oxygen electrode, Wetlabs transmissometer, and Wetlabs chlorophyll fluorometer. At regular sampling intervals, ORCA profiles the water column using the winch and pressure information from the CTD. The data are recorded on the computer and transmitted to the lab automatically via cellular communications. Data are presented from a 1-day deployment in May 2000 and from a long-term, 7-month deployment. The dataset reveals the combination of intermittent stratification mixing and strong seasonal forcing in this estuarine system.