Elizabeth L. Creed

Using a fleet of slocum battery gliders in a regional scale coastal ocean observatory

Rutgers University is constructing the New Jersey Shelf Observing System (NJSOS), a regional-scale (300 km /spl times/ 300 km) observatory for the coastal ocean which includes the LEO15 site. Spatially extensive surface remote sensing systems (CODAR, satellites) are continuously collecting data in this region. However, only during the month of July in 1998, 1999, 2000 and 2001 were extensive subsurface physical and optical data collected and only in the LEO15 vicinity. The July samplings were labor and boat intensive. Obtaining the subsurface data in the LEO15 area required the use of up to seven boats and manpower to collect, process and analyze the information. To make the collection of subsurface data in the NJSOS more efficient, less expensive and more complete both spatially and temporally, Rutgers University has worked with Webb Research Corporation on their development of the Slocum Glider autonomous underwater vehicles. Currently Rutgers owns a fleet of four Gliders that can be used individually or as a group to collect subsurface data in the observatory region.

Inter-comparison of turbidity and sediment concentration measurements from an ADP, an OBS-3, and a LISST

A two-year study is being conducted jointly by Stevens Institute of Technology and Rutgers, The State University of New Jersey to create a sediment budget for the Port of New York and New Jersey to further the understanding of the physical processes responsible for persistent siltation of New York Harbor. Scientists are investigating the extent to which marine sediments are suspended due to meteorological events, dredging practices and/or vessel traffic. Thus far hydrodynamic and sediment concentration measurements have been made twice in 2000 and thrice in 2001 in Newark Bay, the Arthur Kill and the Kill van Kull using multi-instrumented moorings deployed simultaneously at the three sites for two to four week periods. Each mooring contains a SonTek Acoustic Doppler Current Profiler (ADP), a SeaBird MicroCat CTD, a D&A Instruments OBS-3 and a Sequoia Scientific LISST-100. The optical measurement obtained by the OBS-3, which can be translated into suspended sediment load, is dependent on grain size distribution and concentration. The acoustic backscatter intensity from the ADP can also be used as an indicator of turbidity in the water column, which is dependent on grain size distribution and concentration, as well as particle shape and density. The LISST, a laser forward-scattering instrument, reports the sediment concentration and the grain size distribution from 1.25 to 500 /spl mu/m in situ. The measured concentration is dependent on sediment concentration and shape as the LISST assumes that all particles are spheres. A comparison of time-history signals among the LISST, the OBS-3 and the ADP was conducted to examine whether changes in the OBS-3 and ADP output signals represent real changes in sediment concentration, or merely changes in grain size distribution and particle composition.

LEO-15 Observatory - the next generation

The cabled LEO-15 observatory was a vision of Fred Grassle and Chris von Alt that became a reality in 1996 with the deployment of Nodes A and B in 15 meters of water off of Tuckerton, New Jersey. These nodes have served the scientific community well for almost a decade providing power to a variety of sensors and bi-directional real-time communication between the sensors and the PIs computer located on shore. However, technology and scientific needs have changed since these nodes were deployed making it necessary to upgrade the nodes to meet not only todays demands but also to provide expandability and flexibility for the future. The nodes must be able to do more than provide real-time data. They need to be a part of a sustained and interactive network of autonomous and remote platforms that coordinate sampling in space as well as in time. Rutgers University Mid-Atlantic Bight National Undersea Research Center (MABNURC) has partnered with WETSAT, Inc. to accomplish the LEO upgrade and expansion. The nodes will be expanded to include 10 guest ports for visiting scientists to plug their sensors into as well as ports for an auto-profiling unit, and two video ports (with lights and pan/tilt capability). There will also be expansion capabilities with two 10/100BASE-TX ports so that more guest ports can be added if necessary. Communications will be upgraded to TCP/IP over Gigabit Ethernet. Each science port will have regulated isolated power, at a software selectable voltage where necessary that is individually ground fault and over-current protected. Finally, the DACNet ocean observatory operating system software will be used to control the observatory. Phase 1 of the node upgrade, will be completed in the summer of 2005, and is concentrated on the refurbishment of Node A and installation of DACNet. In addition to the nodes, plans are underway to deploy an instrumented buoy and bottom mooring on the Endurance Line at the 60 in isobath to augment the Slocum Gliders that operate between LEO-15 and the shelf break.

Transition of Slocum Electric Gliders to a sustained operational system

In the 1980s Slocum Gliders were a vision of Douglas C. Webb, which Henry Stommel promoted in a science fiction article published in Oceanography in 1989. In the early 1990s the glider concept was proven and in the late 1990s open water test flights were done at LEO15. In 2002 Rutgers University COOL Group began collaborating with Webb Research Corporation on the development and deployment of the Gliders. Initially the deployments were on the order of hours to a few days with constant human supervision. By the latter half of 2003 Slocum Gliders were routinely flying multiple week missions and calling in to the automated Glider Command Center on Rutgers main campus via satellite phone to provide a status update, download data and receive any new mission commands. The ability to operate Gliders with minimal human intervention for extended periods of time has allowed Rutgers to integrate them into the New Jersey Shelf Observing System. Since November 2003 a Glider has been occupying the Endurance Line, a 123 km track located between the LEO15 nodes and the shelf break, on a monthly basis. The sustained data set being collected permits scientists to go beyond collecting snapshots of information for short-term projects and gather long-term, expanded region data sets that would allow the tracking of trends over multiple years. While the Endurance Line Glider has been flying, additional Gliders have been operating for shorter periods of time on the West Florida Shelf, in the northwestern Mediterranean and in the Hudson River plume. Like the Endurance Line Glider, these Gliders are controlled by the Glider Command Center via satellite phone. Rutgers would be adding 2 Gliders to its fleet the end of this year bringing the total to 6 electric Gliders. One Glider would be dedicated to the West Florida Shelf Red Tide research program and the second would be used in the Mediterranean to look at the significance of Sahara Desert dust on biological and optical signals. Dedication of the new Gliders to these two research projects would enable Rutgers to have a continual presence in these regions as well as on the shelf of New Jersey.

Automated control of a fleet of Slocum gliders within an operational coastal observatory

Rutgers University, Webb Research, Dinkum Software, Wetlabs, and Mote Marine Lab have been collaborating on the development and deployment of a fleet of Slocum gliders to continuously patrol the coastal oceans. The gliders are AUVs that move up and down in the water column in a saw-toothed pattern by changing their buoyancy. Presently, during a deployment, humans must look at the data, determine if a change in the sampling protocol is indicated by the data and if so, upload a new mission to the glider. Rutgers has been focusing on the development and testing of the software to automate the control of the gliders. Using agent oriented programming, the goal of the software is to assimilate data received by the command center from the gliders and other agents, such as CODAR and satellites, and generate new missions for the glider fleet. The software is being developed on a Linux system. The ability of the command center computer to automatically analyze data from a glider or gliders and recognize thermoclines and haloclines were the first pieces of the control software to be developed. Testing of the thermocline software has been completed using both hand generated data and real data collected in January 2003 from the Gulf of Mexico. New sensors are being added for applications in the New York Bight and on the West Coast Florida Shelf.

Real-time data transmission between research vessel and shore command center

A distributed network of real-time coupled physical/bio-optical observation systems that span scales from the deep ocean to the near-shore is being used to define the physical forcing of biological productivity for the mid-continental shelf and near-shore coastal waters of the Middle Atlantic Bight. A critical component of the network is the ability to gather real-time subsurface data below the spatially extensive remote sensing surface data. The subsurface data will be collected by remotely operated nodes (LEO-15), autonomous nodes (REMUS navigation buoys), survey ships and autonomous underwater vehicles (Coastal Electric Glider). Data from the remotely operated nodes, which consist of physical and bio-optical profilers, have been transmitted to the shore operations center real-time, via fiber optic cable, since August 1996. During the summer 1999 field season thermistor data from the REMUS navigation buoys, survey ship data including towed ADCP and CTD data, and data from the Coastal Electric Glider was transmitted to shore in real-time using RF links. For ship to shore data communication, each vessel had its own local area network which communicated with the shore command center via FreeWave Spread Spectrum Data Transceiver/Ethernet bridge. As data came into the shore station from the research platforms it was processed and put on the Internet. The data was also immediately viewed by scientists, on shore and at sea, to determine if adjustments to the sampling protocol were necessary and to coordinate the sampling of high frequency episodic events.

Observed response of the Hudson River plume to wind forcing using a nested HF radar array

One objective of the Lagrangian Transport and Transformation Experiment (LaTTE) is to determine the relative advantages of studying the Hudson River plume within the spatial and temporal context provided by an operational research observatory. Towards this end, a shelf-wide observational backbone was locally enhanced with high-resolution relocatable systems in the New York Bight apex. The permanent backbone includes local acquisition of international satellite ocean color imagery, a network of long-range High Frequency radars, and a cross-shelf Endurance line occupied by an autonomous underwater glider. The high resolution systems, including higher resolution HF Radar, glider and mooring networks, were moved to the New York Bight Apex to support the specific interdisciplinary process study. During the LaTTE field effort, datasets from the nested observation network, including a triple nested HF Radar array, were assembled in real-time at a shore-based acquisition center, and high-resolution atmospheric forecasts were performed. Surface current observations will be reviewed, with specific emphasis placed on the observed response of the Hudson River plume to local winds. The observatory results provide a spatial and temporal context for viewing the LaTTE dye release, chemical and biological results.

Integration of a RSI microstructure sensing package into a Seaglider

Seagliders are a type of propeller-less AUV that glide through the water by changing their buoyancy. They have become mainstream collectors of standard oceanographic data (conductivity, temperature, pressure, dissolved oxygen, fluorescence and backscatter) and are increasingly used as trucks to carry a wide variety of hydrographic and bio-geochemical sensors. The extended sensor capability enhances the utility of the gliders for oceanographic observations. Seagliders are designed and optimized for long-term missions (up to 10 months) and deep sea profiling (up to 1000 m). They provide high resolution oceanographic data with very good temporal and spatial density, in near real-time, at a fraction of the cost of ship collected data. These performance parameters are sometimes at odds with the physical dimensions and electrical requirements of the hydrographic and bio-geochemical sensors scientists want installed in gliders. However, as the acceptance of gliders as an integral component of the oceanographic suite of measurement tools grows so do the efforts of sensor vendors to develop products that meet the size, weight and power requirements for successful glider integration. Turbulence microstructure sensors are one measurement system that scientists desired on Seagliders but that until recently did not fit the glider footprint. In collaboration with Rockland Scientific, Inc., a suite of RSI turbulence microstructure sensors was recently integrated into a Seaglider and the systems performance validated during field tests in Puget Sound near Seattle, WA and in Loch Linnhe on the west coast of Scotland. Ocean turbulence controls the mixing of water masses, biogeochemical fluxes within them, and facilitates ocean-atmosphere gas exchange. As a result, turbulence impacts global ocean circulation, polar ice melt rates, drawdown of atmospheric carbon dioxide and carbon deposition, coastal and deep ocean ecology, commercial fisheries, and the dispersion of pollutants. Turbulent mixing is also recognized as a key parameter in global climate models, used for understanding and predicting future climate change. Seagliders equipped with turbulence microstructure sensors will allow scientists to map the geographical distribution and temporal variability of mixing in the ocean on scales not possible with ship-based measurements. This presentation discusses the technical aspects of the integration of the turbulence sensor suite on a Seaglider with an emphasis on achieving high data quality, while retaining the performance characteristics of the Seaglider. We will also describe applications for this sensor suite, examine the turbulence measurement data already collected by the Seaglider and discuss future deployment plans.