The Role of Ekman Currents, Geostrophy, and Stokes Drift in the Accumulation of Floating Microplastic

Onink, Victor; Wichmann, David; Delandmeter, Philippe; Sebille, Erik (2019). The Role of Ekman Currents, Geostrophy, and Stokes Drift in the Accumulation of Floating Microplastic. Journal of Geophysical Research: Oceans, 124(3), pp. 1474-1490. AGU 10.1029/2018JC014547

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Floating microplastic in the oceans is known to accumulate in the subtropical ocean gyres, but unclear is still what causes that accumulation. We investigate the role of various physical processes, such as surface Ekman and geostrophic currents, surface Stokes drift, and mesoscale eddy activity, on the global surface distribution of floating microplastic with Lagrangian particle tracking using GlobCurrent and WaveWatch III reanalysis products. Globally, the locations of microplastic accumulation (accumulation zones) are largely determined by the Ekman currents. Simulations of the North Pacific and North Atlantic show that the locations of the modeled accumulation zones using GlobCurrent Total (Ekman+Geostrophic) currents generally agree with observed microplastic distributions in the North Pacific and with the zonal distribution in the North Atlantic. Geostrophic currents and Stokes drift do not contribute to large‐scale microplastic accumulation in the subtropics, but Stokes drift leads to increased microplastic transport to Arctic regions. Since the WaveWatch III Stokes drift and GlobCurrent Ekman current data sets are not independent, combining Stokes drift with the other current components leads to an overestimation of Stokes drift effects and there is therefore a need for independent measurements of the different ocean circulation components. We investigate whether windage would be appropriate as a proxy for Stokes drift but find discrepancies in the modeled direction and magnitude. In the North Pacific, we find that microplastic tends to accumulate in regions of relatively low eddy kinetic energy, indicating low mesoscale eddy activity, but we do not see similar trends in the North Atlantic.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Onink, Victor

Subjects:

500 Science > 530 Physics

ISSN:

2169-9275

Publisher:

AGU

Language:

English

Submitter:

Victor Onink

Date Deposited:

22 Jul 2019 11:33

Last Modified:

25 Feb 2020 13:53

Publisher DOI:

10.1029/2018JC014547

BORIS DOI:

10.7892/boris.131871

URI:

https://boris.unibe.ch/id/eprint/131871

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