Deployment of Drifting Buoys with pCO 2 Sensors in the Pacific Ocean

To reduce areas lacking data of surface seawater pCO 2 , which is an indispensable property for the evaluation of atmospheric CO 2 uptake by the ocean, in 2016 we started a 5-year project to deploy drifting buoys with pCO 2 sensors in the South Pacific. The drifting buoy is compact (diameter, 315 mm; height, 566 mm; weight, ∼10 kg) and easy to manage. For efficient deployment, we determined appropriate deployment positions along a ship track by particle tracking experiments. During the MR16-09 cruise of R/V Mirai, we deployed seven drifting buoys. The tracks of drifting buoys generally followed those predicted by the experiments. pCO 2 values observed by drifting buoys and considered to be reliable were on the whole within values expected from interpolated pCO 2 values. However, the pCO 2 sensor needs to be improved to raise the pCO 2 observation yield ratio of each drifting buoy.