Abstract
The method of Argo float termination is discussed from legal, technical and scientific points of view. According to our domestic law, a label specifying the ownership of the float is necessary, and having a plan to retrieve the float after the mission is preferable in order to avoid a claim of ocean dumping. In this context, we are to terminate the mission of the float so as to allow it to drift on the sea surface after a certain times of dive. For a better retrieval plan, the behavior of the float after the mission is estimated by using a global surface drifting buoy database prepared by the Atlantic Oceanographic and Meteorological Laboratory, which shows 17% and 7% of terminated buoys will be stranded and picked up, respectively, within a year. In the Pacific Ocean, the stranding rate of terminated Argo float will be low in the subtropical gyre, high in the subarctic gyre, and middle in the equatorial area, where the floats tend to be stranded on islands near the equator, New Guinea, and the Philippines within a year. An example shows that retrieving an Argo float is practicable, and suggests that attachment of fouling organisms to the float is possible to sink it within a year after termination. However, positive retrieval should be encouraged because it is very useful for checking the sensor stability and for data quality control.
