Since 1970s, microplastic (MP) has been recognized as a threat for the oceanic environment and, since then, several studies has been carried out in the marine context. As the amount of plastic production (and inefficient disposal) has been intensively increasing, the presence of microplastic has extended to almost all environmental sectors. Among those, atmosphere has been recently identified and recognized not only as a receptor of MP pollution but also as a key medium of transport across the globe.

Nonetheless, little is known about actual emissions and concentrations of MP in the atmosphere. In this work, targeting the ocean as a critical area of plastic accumulation, we aim at understanding the role of the sea-atmosphere MP fluxes in the global atmospheric problem. Coupling a sea spray scheme (Grythe et al. 2014) with the ocean surface MP concentrations simulated by the NEMO-PISCES general circulation model (Richon et al. 2022), we estimate the MP emissions due to sea spray at 6-hourly resolution, over a one-year period. The MP emission fluxes are then fed into the Lagrangian atmospheric dispersion model FLEXPART (Stohl et al., 2005, Pisso et al., 2019), driven with hourly ERA5 data at 0.5° horizontal resolution, to provide a global picture of the atmospheric cycle of the MP of marine origin.

We discuss the main emission areas and their seasonal variability, the resulting atmospheric concentrations across the globe, its vertical spread from surface to the stratosphere and the deposition fluxes on both land and ocean surfaces. Finally, we compare simulated fluxes and concentrations with existing observations of MP in the marine atmosphere.

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