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Study Describes Design and Testing of an Effective Biodegradable Ocean Drifter

July 10, 2018
Study author Guillaume Novelli deploys the eco-friendly CARTHE drifters, which are designed to measure shallow-depth surface currents.

Scientists detailed how they designed and tested an ocean drifter that tracks and measures shallow-depth (0.60 m) surface currents. The final version, called the CARTHE drifter, is made from a polymer produced by bacteria fed with corn sugar. The affordable and off-the-shelf electronic components include mercury- and lead-free alkaline battery packs not classified as hazardous by the U.S. Environmental Protection Agency. The team analyzed the motion of scaled models in a wind-wave-current flume, field tested full-scale models, and validated their trajectories against a well-established drifter model. Then, they produced and deployed over 1,000 units for the Lagrangian Submesoscale Experiment (LASER) campaign, which successfully tracked submesoscale features in the Gulf of Mexico. Because this technology is affordable and can be mass produced, it is transferable from academia to the private and public sector. The researchers published their findings in the Journal of Atmospheric and Oceanic Technology: A biodegradable surface drifter for ocean sampling on a massive scale.

Drifter tracking is the oldest way to measure currents; however, submesoscale currents (typically 102 – 104 meters in length and hours to days in time scales) have been understudied. These small-scale currents induce strong surface rotation or spinning and divergence fields that can cause floating material to initially cluster and then disperse and spread out. The LASER campaign sought to capture submesoscale events with the appropriate spatiotemporal resolution, which would require an improved drifter design and the deployment of the most drifters ever.

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