Posts Tagged ‘continental shelf’

UGA Skidaway Institute participates in Gliderpalooza 2013

September 18, 2013

More than a dozen underwater robotic vehicles called “gliders” will be launched simultaneously this month in a massive, cooperative project involving 10 east coast research institutions, including the University of Georgia Skidaway Institute of Oceanography. Dubbed Gliderpalooza 2013, the fleet of gliders will cruise the waters of the east coast for several weeks, collecting data that could help improve future hurricane forecasts. 

UGA Skidaway Institute scientist Catherine Edwards makes adjustments to the glider “Modena” while R/V Savannah crewman Mickey Baxley assists.

UGA Skidaway Institute scientist Catherine Edwards makes adjustments to the glider “Modena” while R/V Savannah crewman Mickey Baxley assists.

The gliders are torpedo-shaped vehicles, equipped with sensors and recorders to collect observations under all conditions. These autonomous underwater vehicles, or AUVs, move through the water by adjusting their buoyancy and pitch. Because they are highly energy efficient, gliders can remain on a mission for weeks at a time. Every 4 to 6 hours over their mission, they surface, report their data by satellite phone and receive instructions as needed.

According to Skidaway Institute scientist Catherine Edwards, one goal of Gliderpalooza 2013 is to test the feasibility of using a fleet of gliders to work together and to integrate their data—collected in the same time period, but over a wide geographical range.

“Gliders are powerful tools for oceanographers,” Edwards said. “We believe there is great potential to expand the value of them by working together on the deployments and integrating the data each collects.”

Another reason for promoting the use of gliders is their relatively inexpensive cost of operation. Gliders can operate for weeks at a time and in all kinds of weather conditions for a small fraction of the daily coast of an ocean-going research vessel.

“Gliders will never replace ships in oceanography—ship surveys are often the best way to collect data,” Edwards said. “But AUVs require far fewer resources and personnel than shipboard work, and can operate in conditions that would be impossible for traditional ship surveys. For lengthy data-collection missions, a glider can operate for pennies on the dollar by comparison.”

Scientists at Rutgers University are coordinating the project. Computers there will gather the data from the various glider groups, and make it available through a data assembly center for access to and visualization of the data in real time. Glider groups participating in Gliderpalooza will contribute pictures, updates and other notes of interest to scientists and the general public on a blog available at http://maracoos.org/blogs/main/

September was chosen as the month for deployment because many important fish species migrate in that month, and a coordinated experiment can provide a more complete picture of oceanographic conditions and fish populations. September is the most active month for hurricanes, and there is interest in the use of gliders to better understand the effects of major storms on the mixing and transport of heat, nutrients and material.

The Skidaway Institute glider, nicknamed “Modena,” and several others will also be equipped with a special instrument to monitor fish migration. In order to track fish migration, some fisheries biologists tag fish with an acoustic transmitter. The tag-transmitter sends out a sound signal identifying the fish. Typically, receivers on buoys and other stationary platforms monitor these signals. This will be the first time a fleet of moving gliders will be used to monitor fish migration.

Gliderpalooza will also serve as a field test of a new glider navigation system developed by Georgia Tech graduate students, Dongsik Chang, Klimka Szwaykowska and Sungjin Cho, who are supervised by Edwards and Georgia Tech collaborator Fumin Zhang.

Catherine Edwards works on Modena with her team of grad students.

Catherine Edwards works on Modena with her team of grad students.

Gliders can only receive GPS information at the surface. They navigate underwater by dead reckoning, using information on ocean currents from the last leg of their mission. However, the strong tidal currents on the Georgia shelf, combined with the fast-moving Gulf Stream at the shelf edge often exceed a glider’s forward speed. This creates the opportunity for significant navigational errors.

The Glider Environmental Network Information System (GENIoS) is an automated system that optimizes glider navigation based on real time data from ocean models, high frequency radar and measurements from the glider itself. By integrating these data with ocean models, GENIoS provides a more accurate prediction of the currents the glider will navigate through, and chooses the most efficient target waypoints for the glider to aim for as those currents change in space and time.   

During Gliderpalooza, the Skidaway Institute glider will conduct a triangle-shaped mission that includes one leg along the edge of the continental shelf, which also corresponds roughly to the western edge of the Gulf Stream.

“The combination of strong tidal currents and the influence of the Gulf Stream will serve as a strong test of the system,” Edwards said.

The collected glider data will go through NOAA’s National Data Buoy Center to the National Weather Service, the U.S. Navy and other data users for modeling. Data from the glider missions will also be public and available on the Integrated Ocean Observing System Glider Asset Map and at http://www.ndbc.noaa.gov/gliders.pahp.

Funding for Modena’s mission is provided by the UGA Skidaway Institute of Oceanography and the Southeast Coastal Ocean Observing Regional Association.

More information and an ongoing update on the progress of the project are available on the Gliderpalooza 2013 blog at http://maracoos.org/blogs/main/?p=448.

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Glider-robots!

December 19, 2011

We had a real nice story on the front page of this morning’s Savannah Morning News. A big thanks to Mary Landers and her editors!

Skidaway Institute, Georgia Tech-Savannah partner on phytoplankton research

April 18, 2011

Sometimes scientific advances provide answers, and sometimes, they simply present more questions. That is what happened when scientists began using satellite imagery to study the ocean.

When Skidaway Institute of Oceanography scientists Jim Nelson and Catherine Edwards looked at satellite imagery of the ocean off the Carolinas, they noticed persistent blooms of phytoplankton, an important part of the marine food web. These mysterious blooms occurred during the winter along edge of the continental shelf off Long Bay — located between Cape Romain, South Carolina and Cape Fear, North Carolina. Phytoplankton blooms like those observed off Long Bay can provide a considerable boost to the bottom of the food chain, with significant implications for fisheries.

“The immediate cause of the blooms is an input of nutrients, like nitrogen and phosphorous, associated with transport and mixing of deep, cold onto the continental shelf,” said Edwards. “The Long Bay blooms persist for weeks or even months during the winter, suggesting multiple modes of nutrient input.”

Two of the guiding questions are why this feature is so persistent over the winter, and what are the dynamics that sustain this bloom?

Edwards and Nelson are teaming with Harvey Seim from the University of North Carolina and Fumin Zhang from Georgia Tech-Savannah on a project to answer those questions. The project is funded by a $1.6 million grant from the National Science Foundation supporting a team of scientists from all three institutions. With the help of Skidaway Institute research coordinators Trent Moore, Julie Amft and Charles Robertson, the project team will deploy moored and mobile instrument packages and conduct shipboard surveys to test hypotheses of how the winter blooms are formed and sustained.

The team will use some cutting-edge technology that will enhance its ability develop a clear picture of what is happening. This includes instrument packages mounted on moorings; mobile, autonomous “gliders”; underway ship surveys; standard ship-based station sampling; and satellite measurements of sea surface temperature and ocean color.

Skidaway Institute researchers (l-r) Catherine Edwards, Trent Moore, Julie Amft and Jim Nelson examine a glider.

Three moored packages will be deployed to provide continuous measurements of water properties and currents through the winter months. One mooring will be placed at 35 meters of depth, the approximate position of the shoreward edge of the winter bloom.

Two more packages will be placed in approximately 75 and 150 meters of water, with the 75 meter mooring equipped with an instrument package called a SeaHorse. Powered by wave motion, the Seahorse moves up and down its mooring wire, taking measurements throughout the water column. A telemetry system in the surface mooring periodically reports its observations.

The research team will also use another high-tech tool, autonomous underwater vehicles, also called gliders.

Skidaway Institute researchers lower a glider into a tank of water to adjust buoyancy and trim. (l-r) Trent Moore, Dongsik Chang, Charles Robertson and Julie Amft

Two of these torpedo-shaped vehicles, equipped with sensors and recorders, will provide the ability to collect observations under all conditions, including during winter storms when ship operations are not possible. The gliders will survey across the study area, taking and recording measurements as they go. From time to time over the four to five week missions, they will surface, report their data by satellite phone and receive instructions as needed.

The gliders will be controlled from shore with an autonomous glider control system co-developed by Fumin Zhang at Georgia Tech Savannah. Two Georgia Tech-Savannah graduate students, Klimka Szwaykowska and Dongsik Chang, are developing algorithms to optimize the glider sampling given real-time data collected by satellite, the SeaHorse profiler and the gliders themselves.

Catherine Edwards (r) and Dongsik Chang work on the tail of a glider while Klimka Szwaykowska looks on.

Members of the research team will spend much of the winter of 2012 aboard the Skidaway Institute research vessel R/V Savannah, conducting experiments and collecting data.

Armed with a better understanding of the physical processes that “fertilize” the outer shelf and how phytoplankton take advantage of the nutrient input, the research team will be able to answer larger questions about how biology and physics interact in Long Bay.

The project will run for three years.