Researchers from Florida State University's Center for Ocean-Atmospheric Prediction Studies (COAPS) took home a top prize late last year in a Department of Defense competition that encourages development of new models predicting the movement of free-floating objects on the ocean's surface.

COAPS research faculty member Philippe Miron led the team, composed of COAPS director and distinguished professor of oceanography Eric Chassignet, associate research scientists Dmitry Dukhovskoy, Xiaobiao Xu, and research scientist Olmo Zavala, to a third-place overall in the Defense Advanced Research Projects Agency Forecasting Floats in Turbulence Challenge along with a $10,000 prize.

“The DARPA challenge was a great opportunity to apply our understanding of ocean dynamics and how floating objects at sea move when subject to the combined effects of ocean currents, wind and waves,” Miron said. “The ability to better model the ocean’s surface currents has real-world applications such as man-overboard recovery, improved ship route planning, and oil-spill response.”

The goal of the challenge was to develop algorithms, among other methods, to predict where 90 drifters, originally released by DARPA into the Atlantic Ocean, would travel over a 10-day period. Drifters are spherical, basketball-sized floating devices with sensors that record data including temperature and salinity, and they are typically tracked via GPS to measure ocean current properties.

Teams received the previous 20 days of location data from the drifters’ GPS coordinates, and using that data, they trained their models to predict where they would travel 10 days into the future. Points were awarded based on prediction accuracy of drifters’ location in 2-day, 4-day, 6-day, 8-day and 10-day forecasts. The further out the forecast, the higher the point value for accuracy.

“COAPS uses global and regional models to improve both short- and long-term ocean current forecasts and to study ocean processes such as ocean circulation and water mass formation,” Chassignet said. “This contest was an opportunity for us to consider and overcome some of the difficulties involved in long-term trajectory forecasting in an applied way.”

The COAPS team used a model that accounted for ocean currents, waves and winds. After performing a series of optimizations, they realized that the Stokes Drift (wave-induced motion) had much more influence than expected on the drifters' trajectories. To decrease the initial error between the model predictions and the observations, the team used the last known positions of the drifters to correct the model prediction in the first critical hours of the forecast.

According to DARPA project manager John Waterson, there is currently no way to accurately predict where a message in a bottle floating in the open sea will be in a week, let alone where it will eventually wash ashore. Finding ways to precisely forecast where a drifting object in the ocean will be in the following days or weeks can be incredibly useful.

“This knowledge is helpful in solving real-world problems like rescuing people or ships lost at sea, determining the amount and location of sargassum that may reach the coast, defining the best cleaning strategies when an oil spill occurs by estimating the future path of the oil slick or defining the trajectories of different types of pollution in the ocean,” Zavala said.

The COAPS mission is to promote interdisciplinary research in air-sea interaction, the coupled ocean-atmosphere-land-ice earth system, and climate prediction on scales of weeks to decades in order to increase understanding of the physical, social, and economical consequences of ocean-atmospheric variations. COAPS is part of the FSU College of Arts and Sciences, and COAPS teaching faculty are also members of the FSU Department of Earth, Ocean and Atmospheric Science.

The interdisciplinary nature of COAPS’ work creates a team of researchers who have diverse skillsets, interests and backgrounds, which was a major contributing factor to the team’s success in the DARPA challenge.

“Our team consisted of scientists with multi-disciplinary backgrounds, ranging from physical oceanography, mechanical engineering, computational fluid dynamics and scientific computing. Also, each team member has a different country of origin — Canada, France, Russia, China and Mexico. This project is a success story of building research groups that are diverse and multi-disciplinary,” Zavala said.