Designing a Glider Network to Monitor Rapid Climate Change:

1. Designing a Glider Network to Monitor Rapid Climate Change: Evaluation of Thermal Glider Flight Characteristics Holly Ibanez1, Amelia Snow2, Darcy Glenn3, Scott Glenn2, Oscar Schofield2 1 Florida Institute of Technology, 2 Rutgers University, 3 University of Vermont Background Datasets and Methodologies Conclusions The oceans absorb approximately 80% of heat from the atmosphere. Much of this heat is stored and transported through ocean currents and gyres; therefore, the ocean plays a crucial role in weather patterns and climate change. Studies have shown that ocean temperatures are rising, which may have an effect on heat transport and weather. Models and observations have linked variability in the Meridional Overturning Circulation (MOC) and global climate patterns along 26.5⁰N. The MOC is the north-south flow of water in the Atlantic Ocean, which brings warm water northward along the surface and cold, dense water southward along the bottom. Changes in the strength of each of those components are suspected to have an effect on one another; however, a lack of data makes this hypothesis difficult to test. A steering issue was identified on Cook, which occurred after inflections due to fluid pitch beginning 24 seconds before the valve was programmed to open. This resulted in the glider turning up to 180⁰ off course for as much as 200 meters of each dive. Poor steering is noted for about 20% of each profile that was examined. Steering tests by Webb Research were conducted, but failed to correct the problem. Based on the glider data, a new set of steering parameters was suggested and implemented on RU 21 as a test. Since thermal gliders are still in development, it is important to analyze characteristics such as heading error, pitch, velocity, and roll in order to optimize flight. -15⁰ 0⁰ -55⁰ -115⁰ 55⁰ 115⁰ 0⁰ 15⁰ 200 200 400 400 Meters Meters 600 600 Downcast Upcast Downcast Upcast 800 Depth divided by 10 Average Heading Error Heading Error Standard Deviation Average Fin 800 1000 1000 1200 1200 Fig 3: Cook experienced heading error up to 180⁰ and even completed a full 360⁰ rotation. Fig 4: Pitch was set to -15⁰ during downcasts and +15⁰ during upcasts. Objectives 2⁰ 1⁰ 0⁰ The main objective of Cook’s mission was to evaluate the potential of multiple gliders to monitor critical survey lines to help detect rapid climate change. The data collected by the gliders would contribute to the RAPID Program initiated in the United Kingdom. By analyzing Cook’s flight characteristics, it is possible to determine how to optimize flight of a fleet of gliders. 0.40 0.35 0.45 0.50 m/s 200 200 400 400 Meters 600 Meters 600 800 800 Downcast Upcast Downcast Upcast 1000 1000 1200 1200 8/02 7/27 7/29 Fig 5: Velocity remained constant throughout the voyage and averaged 10 cm/s faster during upcasts. Fig 6: Cook experienced less than 5⁰ roll during both upcasts and downcasts. Fig 1: Projected path of the Challenger Mission Technology Results The slocum gliders used by Rutgers University were engineered by Teledyne Webb Research, and are programmed to contact RUCOOL using an iridium system. Electric gliders require alkaline or lithium batteries and pump water into the nose to change buoyancy. Thermal gliders are more efficient for use in the Challenger Mission because they have a much longer life span (about 3 to 4 years as compared to 30 days for an electric glider); however a 15⁰C difference in the water temperature is required to fly optimally. To determine whether Cook’s CTD was accurately collecting data, temperature and salinity were compared to predictions made by HYCOM. Fig 9: At the beginning of RU 21’s mission, instantaneous gain was set to 1 and integrated gain was turned off, or set to 0. On July 29, integrated gain was set to default value 0.03. This caused the heading error to reach 50⁰. On July 30, integrated gain was once again set to zero, and the instantaneous gain was doubled. This resulted in a more responsive fin, and less heading error. Fig 7: Temperature data collected by Cook matches up with HYCOM’s prediction. References Glenn, Darcy E., Holly A. Ibanez, and Amelia E. Snow. "Cook Flight Summary." Print. "Introduction to Rapid Climate Change (RAPID and RAPID-WATCH)." British Oceanographic Data Centre. <http://www.bodc.ac.uk/projects/uk/rapid/introduction>. Kanzow, Torsten, Stuart A. Cunningham, Darren Rayner, Joel J. M. Hirschi, William E. Johns, Molly O. Baringer, Harry L. Bryden, Lisa M. Beal, Christopher S. Meinen, and Jochem Marotzke. "Observed Flow Compensation Associated with the MOC at 26.5⁰N in the Atlantic." Science 5840th ser. 317 (2007). "Oceanography Vocabulary: Irminger Sea." Home: Woods Hole Oceanographic Institution. <http://www.whoi.edu/page.do?pid=27635>. "RAPID-WATCH." National Oceanography Centre, Southampton - Home. Web. 30 July 2010. <http://www.noc.soton.ac.uk/rapid/rw/>. Fig 8: Salinity data collected by Cook does not match up with HYCOM’s prediction. Since the CTD is proven to be accurate, it is concluded that a glider is an efficient means to collect ocean data. Acknowledgements This work was made possible by funding from the Office of Naval Research, National Science Foundation, and the Department of Homeland Security. SlocumGliders were designed and built by Teledyne Webb Research Corporation. Collaboration was established and results were contributed by PLataforma Oceanica de CANarias and Universidad de las Palmas de Gran Canaria. Fig. 2: A thermal glider uses a change in buoyancy as well as a change in ocean temperature to fly through the water.