HR: 12:05h
AN: OS42A-08    [Abstracts]
TI: In-situ Chemical Exploration and Mapping using an Autonomous Underwater Vehicle
AU: * Camilli, R
EM: rcamilli@whoi.edu
AF: Woods Hole Oceanographic Institution, MS#7, Woods Hole, MA 02543 United States
AU: Bingham, B S
EM: bbingham@whoi.edu
AF: Woods Hole Oceanographic Institution, MS#7, Woods Hole, MA 02543 United States
AU: Jakuba, M
EM: mjakuba@whoi.edu
AF: Woods Hole Oceanographic Institution, MS#7, Woods Hole, MA 02543 United States
AU: Whelan, J
EM: jwhelan@whoi.edu
AF: Woods Hole Oceanographic Institution, MS#7, Woods Hole, MA 02543 United States
AU: Singh, H
EM: hsingh
AF: Woods Hole Oceanographic Institution, MS#7, Woods Hole, MA 02543 United States
AU: Whiticar, M
EM: whiticar@uvic.ca
AF: University of Victoria, PO Box 3055, Victoria, BC V8W 3P6 Canada
AB: Recent advances in in-situ chemical sensing have emphasized several issues associated with making reliable chemical measurements in the ocean. Such measurements are often aliased temporally and or spatially, and may suffer from instrumentation artifacts, such as slow response time, limited dynamic range, hysteresis, and environmental sensitivities (eg., temperature and pressure). We focus on the in-situ measurement of light hydrocarbons. Specifically we examine data collected using a number of methods including: a vertical profiler, autonomous underwater vehicles (AUV) surveys, and adaptive spatio-temporal survey techniques. We present data collected using a commercial METS sensor on a vertical profiler to identify and map structures associated with ocean bottom methane sources in the Saanich inlet off Vancouver, Canada. This sensor was deployed in parallel with a submersible mass spectrometer and a shipboard equilibrator-gas chromatograph. Our results illustrate that spatial offsets as small as centimeters can produce significant differences in measured concentration. In addition, differences in response times between instruments can also alias the measurements. The results of this preliminary experiment underscore the challenges of quantifying ocean chemical processes with small-scale spatial variability and temporal variability that is often faster than the response times of many available instruments. We explore the capabilities and current limitations of autonomous underwater vehicles for extending the spatial coverage of new in-situ sensor technologies. We present data collected from deployments of Seabed, a passively stable, hover capable AUV, at large-scale gas blowout features located along the U.S. Atlantic margin. Although these deployments successfully revealed previously unobservable oceanographic processes, temporal aliasing caused by sensor response as well as tidal variability manifests itself, illustrating the possibilities for misinterpretation of localized periodic anomalies. Finally we present results of recent experimental chemical plume mapping surveys that were conducted off the coast of Massachusetts using adaptive behaviors that allow the AUV to optimize its mission plan to autonomously search for chemical anomalies. This adaptive operation is based on coupling the chemical sensor payload within a closed-loop architecture with the vehicle's navigation control system for real-time autonomous data assimilation and decision making processes. This allows the vehicle to autonomously refine the search strategy, thereby improving feature localization capabilities and enabling surveys at an appropriate temporal and spatial resolution.
UR: http://dsl.whoi.edu/DSL/hanu/seabed/index.html
DE: 4820 Gases
DE: 4894 Instruments and techniques
DE: 4294 Instruments and techniques
DE: 1694 Instruments and techniques
DE: 1635 Oceans (4203)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting