Inertia‐induced accumulation of flotsam in the subtropical gyres

• Published in: Geophysical research letters 2016-12, Vol.43 (23), p.12,228-12,233
• Main Authors: Beron‐Vera, F. J., Olascoaga, M. J., Lumpkin, R.
• Format: Article
• Language: English
• Subjects: Accumulation; Buoyancy; Constraints; Convergence; Debris; Density; Drift; drifter; Drifters; drogue; Flotsam; Garbage; Geophysics; Gyres; Inertia; Litter; Mathematical analysis; Mathematical models; Movement; Ocean currents; patch; Patches (structures); Plastic debris; Plastics; Polymers; Submerged; Surveys; Wind
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2016GL071443

Recent surveys of marine plastic debris density have revealed high levels in the center of the subtropical gyres. Earlier studies have argued that the formation of great garbage patches is due to Ekman convergence in such regions. In this work we report a tendency so far overlooked of drogued and undrogued drifters to accumulate distinctly over the subtropical gyres, with undrogued drifters accumulating in the same areas where plastic debris accumulate. We show that the observed accumulation is too fast for Ekman convergence to explain it. We demonstrate that the accumulation is controlled by finite‐size and buoyancy (i.e., inertial) effects on undrogued drifter motion subjected to ocean current and wind drags. We infer that the motion of flotsam in general is constrained by similar effects. This is done by using a newly proposed Maxey‐Riley equation which models the submerged (surfaced) drifter portion as a sphere of the fractional volume that is submerged (surfaced). Key Points Undrogued drifters and plastic debris accumulate similarly in the subtropical gyres The accumulation is too fast to be due to Ekman convergence Inertial effects (i.e., of finite size and buoyancy) explain the accumulation