OS42A-01 10:20h
Improved performance of a broadband ocean bottom seismograph connected to off-shore submarine cable off-Tokachi, Hokkaido, Japan.
A seismograph deployed in the seafloor is subject to seafloor current which results in severe noise especially at frequencies below 0.1Hz. Burial of seismographs below seafloor to reduce the effect of seafloor current was suggested, and has been tried in several seafloor deployments. There is, though, not clear indication of how much reduction can be achieved by surficial burying. We compared the background noise levels of a broadband ocean bottom seismograph (OBS) before and after burial operation. In July 2004, we deployed a Guralp CMG-1T broadband seismograph in off-Tokachi, Hokkaido, Japan seafloor. This is where three ocean bottom seismographs (OBS) using submarine cable are installed. The Tokachi earthquake of magnitude 8.0 occurred in September 26, 2003 below the submarine cable OBS network. By installing additional broadband OBS, we aim to monitor postseismic activity of the large earthquake. The broadband OBS, as well as a pressure gauge, was connected to the submarine cable via the branch module of the cable to recover data. The burial of the ocean bottom seismograph was performed by a remotely operated vehicle (ROV) "Hyper-Dolphin" of JAMSTEC. Using a hydraulic pump, the ROV pumped out sediment from a PVC caisson on the seafloor to submerge it in the seafloor. The broadband OBS was then installed inside the caisson. The caisson buried in the seafloor was finally filled with glass beads to eliminate space between the broadband sensor and the caisson. Improvement of the background noise level by the burial operation of the broadband OBS was apparent in two frequency bands; below 0.1 Hz and above 4Hz. Below 0.1 Hz, the background noise became about 20dB or more quieter after burial for both vertical and horizontal components. Above 4Hz, a persistent noise peak around 5 Hz disappeared after burial. Thus, we consider this peak as an artificial noise due to the seismograph package. After burial, we could clearly notice several noise peaks above 2Hz which was only just visible before burial. These peaks probably show seismic resonance in the sediment layer.
OS42A-02 10:35h
Cabled Observatory Recorded a M8 earthquake -Revealed phenomena and Necessity to future ocean observatories-
Scientific results started appearing in the literature using realtime and continuous time series of data obtained on the seafloor for seismic and micro-tsunamic observations. JAMSTEC has developed three out of a total of seven cabled observatories in the Japanese water. The installed observatories are all operating to aid earthquake studies for disaster mitigation at the future potential hazards which take place at plate boundaries surrounding the Japanese islands. Along with earthquake activity monitoring purposes, it has become clear that there are potentially and scientifically meaningful outcome from such observations. We summarize the latest scientific results from monitored data produced by our cabled observatories and, then, to demonstrate advantages of such underwater seismic and tsunamic stations. We also have experienced the latest M8 plate boundary earthquake in September 2003. The cabled observatory has proven the effectiveness of such observation system in the monitoring of earthquakes in the ocean. Discussions finally make it clear that it is necessary to deploy such observatories and to enhance the resolution or signal-to-noise ratio of observations on top of the existing technology of cabled observatories. Especially, much closer access should be tried to seismogenic zones to monitor deep processes or to detect any precursory of plate boundary megathrust earthquakes. It is obvious that newly deployed monitoring systems have revealed meaningful phenomena which have been invisible due to lack of observations in the offshore. Technical and theoretical developments for offshore earthquake minitoring and any related natural events must be well considered.
OS42A-03 10:50h
Operable Data Management for Ocean Observing Systems
As oceanographic observing systems become more numerous and complex, data management solutions must follow. Most existing oceanographic data management systems fall into one of three categories: they have been developed as dedicated solutions, with limited application to other observing systems; they expect that data will be pre-processed into well-defined formats, such as netCDF; or they are conceived as robust, generic data management solutions, with complexity (high) and maturity and adoption rates (low) to match. Each approach has strengths and weaknesses; no approach yet fully addresses, nor takes advantage of, the sophistication of ocean observing systems as they are now conceived. In this presentation we describe critical data management requirements for advanced ocean observing systems, of the type envisioned by ORION and IOOS. By defining common requirements -- functional, qualitative, and programmatic -- for all such ocean observing systems, the performance and nature of the general data management solution can be characterized. Issues such as scalability, maintaining metadata relationships, data access security, visualization, and operational flexibility suggest baseline architectural characteristics, which may in turn lead to reusable components and approaches. Interoperability with other data management systems, with standards-based solutions in metadata specification and data transport protocols, and with the data management infrastructure envisioned by IOOS and ORION, can also be used to define necessary capabilities. Finally, some requirements for the software infrastructure of ocean observing systems can be inferred. Early operational results and lessons learned, from development and operations of MBARI ocean observing systems, are used to illustrate key requirements, choices, and challenges. Reference systems include the Monterey Ocean Observing System (MOOS), its component software systems (Software Infrastructure and Applications for MOOS, and the Shore Side Data System), and the Autonomous Ocean Sampling Network (AOSN).
OS42A-04 11:05h
A New Submersible Imaging-in-flow Instrument to Monitor Nano- and Microplankton: Imaging FlowCytobot
Understanding of how coastal plankton communities are regulated has traditionally been limited by undersampling, but cabled observatories now provide opportunities to deploy submersible sensors that have high power and data transmission requirements. We have developed an in situ instrument to carry out high-resolution, long term monitoring of phytoplankton and microzooplankton in the size range 10 to100 micrometers, to be deployed at cabled research facilities such as the Martha's Vineyard Coastal Observatory (MVCO). The new instrument is designed to complement FlowCytobot, a submersible flow cytometer currently deployed at MVCO that uses fluorescence and light scattering signals from a laser beam to characterize the smallest phytoplankton cells (less than 10 micrometers). Imaging FlowCytobot uses a combination of flow cytometric and video technology to capture images of organisms for identification and to measure chlorophyll fluorescence associated with each image. Images will be classified using neural net software, while the measurements of chlorophyll fluorescence will allow us to discriminate heterotrophic from phototrophic cells. The new instrument, like the original FlowCytobot is autonomous but remotely programmable. It utilizes a computer controlled syringe pump and distribution valve that allows periodic anti-fouling treatment and analysis of standard beads. Samples are analyzed continuously (0.25 to 2.5 ml per min) and data is sent over a fiber optic link to a remote computer for analysis. Preliminary results indicate that we can detect cells as small as 5 micrometers and discriminate several taxa of diatoms and dinoflagellates.
OS42A-05 11:20h
Towards Determining the Upper Temperature Limits to Life on Earth: An In-situ Sulfide-Microbial Incubator
Determining the maximum conditions under which life thrives, survives, and expires is critical to understanding how and where life might have evolved on our planet and for investigation of life in extraterrestrial environments. Submarine black smoker systems are optimal sites to study such questions because thermal gradients are extreme and accessible within the chimney walls under high-pressure conditions. Intact cells containing DNA and ribosomes have been observed even within the most extreme environments of sulfide structure walls bounded by 300\deg C fluids. Membrane lipids from archaea have been detected in sulfide flanges and chimneys where temperatures are believed to be 200-300\deg C. However, a balanced inquiry into the limits of life must focus on characterization of the actual conditions in a given system that favor reactions necessary to initiate and/or sustain life. At present, in-situ instrumentation of sulfide deposits is the only effective way to gain direct access to these natural high-temperature environments for documentation and experimentation. With this goal in mind, three prototype microbial incubators were developed with funding from the NSF, University of Washington, and the W.M. Keck Foundation. The incubators were deployed in 2003 in the walls of active black smoker chimneys in the Mothra Hydrothermal Field, Endeavour Segment of the Juan de Fuca Ridge. All instruments were successfully recovered in 2004, and one was redeployed for a short time-series experiment. Each 53-cm-long titanium assembly houses 27 temperature sensors that record temperatures from 0 to 500\deg C within three discrete incubation chambers. Data are logged in a separate housing and inductively coupled links provide access to the data loggers without removal of the instruments. During the initial deployment, data were collected from 189 to 245 days, with up to $\sim478\deg$ K temperature measurements completed for an individual instrument. Temperatures within the chimney walls ranged from near ambient conditions to $\sim280\deg$ C. Distinct thermal gradients were delineated extremely well in each of the three discrete environmental chambers in all instruments. In one instrument numerous perturbations were recorded simultaneously on all 27 probes showing temperature increases of up to $\sim30\deg$ C. Smaller-scale fluctuations resulting from tidal perturbations were ubiquitous in all instruments. Tidal pumping that mixes oxygenated seawater and reduced, volatile-rich hydrothermal fluids may be critical for development of dense and diverse microbial communities within the outer chimney walls. Preliminary examination of some sterile mineral surfaces emplaced within the chambers shows extensive biofilm development. Culturing experiments are ongoing and DNA has been successfully extracted from many of the chambers for genetic characterization. This experiment is a component of the W.M. Keck Foundation-funded proto-NEPTUNE Observatory and Ridge R2K program at Endeavour.
OS42A-06 11:35h
Medusa-Isosampler: A modular, network-based observatory system for combined physical, chemical and microbiological monitoring, sampling and incubation of hydrothermal and cold seep fluids
The study of life in extreme environments provides an important context from which we can undertake the search for extraterrestrial life, and through which we can better understand biogeochemical feedback in terrestrial hydrothermal and cold seep systems. The Medusa-Isosampler project is aimed at fundamental research into understanding the potential for, and limits to, chemolithoautotrophic life, i.e. primary production without photosynthesis. One environment that might foster such life is associated with the high thermal and chemical gradient environment of hydrothermal vent structures. Another is associated with the lower thermal and chemical gradient environment of continental margin cold seeps. Under NERC, NASA and industrial support, we have designed a flexible instrumentation system, operating as networked, autonomous modules on a local area network, that will make possible simultaneous physical and chemical sampling and monitoring of hydrothermal and cold seep fluids, and the in situ and laboratory incubation of chemosynthetic microbes under high pressure, isobaric conditions. The system has been designed with long-term observatory operations in mind, and may be reconfigured dynamically as the requirements of the observatory installation change. The modular design will also accommodate new in situ chemical and biosensor technologies, provided by third parties. The system may be configured for seafloor use, and can be adapted to use in IODP boreholes. Our overall project goals are provide an instrumentation system capable of probing both high and low-gradient water-rock systems for chemolithoautotrophic biospheres, to identify the physical and chemical conditions that define these microhabitats and explore the details of the biogeochemical feedback loops that mediate these microhabitats, and to attempt to culture and identify chemolithoautotrophic microbial communities that might exist there. The Medusa-Isosampler system has been produced and is now undergoing initial deployments at sea.
OS42A-07 11:50h
Mapping hydrothermal plumes in their rising and neutrally buoyant regimes with an autonomous underwater vehicle
Propeller-driven autonomous underwater vehicles (AUVs) potentially enable unique perspectives on hydrothermal plumes that address both the temporal and spatial variability inherent in these structures. Like a lowered or profiling CTD, an AUV offers a platform capable of collecting multiple coregistered data; however, precise navigation and control of an AUV enables complex survey patterns and makes available the possibility of altering vehicle trajectory in real-time. We present data collected by the Autonomous Benthic Explorer (ABE) in June/July 2004 in both the buoyant and neutral components of hydrothermal plumes above the Main Endeavour Field, Juan de Fuca Ridge. The ABE recorded coregistered optical backscatter, temperature and conductivity from two vertically separated probe pairs, redox potential (eH), and water column current velocity from a doppler velocity log (DVL). Bottom-referenced vehicle velocity from the DVL and long baseline positioning enabled the water column velocities from the DVL to be accurately referenced to a stationary world frame. Despite the fact that background currents vary considerably over the course of a single AUV survey due to tidal effects, the use of water column velocity DVL data permits the recovery of better approximations to the time-varying structure of the tracer field in the plume. Using data from above the Juan de Fuca Ridge, we present several candidate triggers that could initiate autonomous behavior to increase survey resolution locally, for instance to improve the possibility of unabiguous detection of rising plume stems from within the neutrally buoyant plume. The envisioned adaptive strategy would result in precisely oriented fine-scale grids within the wider-spaced pre-defined survey. Such a strategy could provide an improvement in spatial resolution in critical regions of the plume without sacrificing the large-scale temporal resolution of the plume.
OS42A-08 12:05h
In-situ Chemical Exploration and Mapping using an Autonomous Underwater Vehicle
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.
http://dsl.whoi.edu/DSL/hanu/seabed/index.html