  We used transition path theory (TPT) to infer "reactive" pathways of floating
marine debris trajectories. The TPT analysis was applied on a pollution-aware
time-homogeneous Markov chain model constructed from trajectories produced by
satellite-tracked undrogued buoys from the NOAA Global Drifter Program. The
latter involved coping with the openness of the system in physical space, which
further required an adaptation of the standard TPT setting. Directly connecting
pollution sources along coastlines with garbage patches of varied strengths,
the unveiled reactive pollution routes represent alternative targets for ocean
cleanup efforts. Among our specific findings we highlight: constraining a
highly probable pollution source for the Great Pacific Garbage Patch;
characterizing the weakness of the Indian Ocean gyre as a trap for plastic
waste; and unveiling a tendency of the subtropical gyres to export garbage
toward the coastlines rather than to other gyres in the event of anomalously
intense winds.
