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IncreasingSea Surface Temperature Suppresses SeaSpray Aerosol-Mediated Microplastics Emission
Summary
As oceans warm from climate change, they actually release *fewer* tiny plastic particles into the air—which might sound good, but scientists warn we shouldn't celebrate yet, since the ocean still emits thousands of tons of microplastics into the atmosphere each year. These airborne plastic particles can travel long distances and potentially end up in the air we breathe and the food we eat, so understanding what controls their release is important for predicting how widespread this pollution becomes. This research shows that ocean temperature is a major factor controlling microplastic emissions, which will help scientists create better models to track where these invisible pollutants go and how they might affect human health.
Floating marine plastics undergo weathering and fragmentation, generating abundant small microplastics (MPs) (≤10 μm) that can be released into the atmosphere by sea spray aerosol (SSA), enabling long-range atmospheric transport. However, despite being increasingly recognized as emerging pollutants, the cross-boundary transport and cycling of MPs remain poorly constrained, and the response of their sea-to-air transfer mechanisms and fluxes to environmental drivers remains highly uncertain. Here, we combine controlled laboratory simulations with model estimation to quantify how sea surface temperature (SST) regulates the SSA-mediated emission of size-resolved MPs (0.5–10 μm). We find that warming SST significantly suppresses MPs enrichment in SSA, with stronger effects observed for smaller MPs. Compared to 0 °C seawater, size-resolved MPs enrichment factors decreased by factors of 1.5 to 4.2 at 30 °C, and this trend was coupled with the decrease in particle size of MPs. Mechanistic analyses indicate that warming SST reduces the submerged bubble scavenging and interfacial enrichment during bubble bursting, thereby impeding the transfer of MPs from the ocean to the atmosphere. By incorporating SST-driven changes in SSA production, surface-ocean MPs concentrations, and size-dependent enrichment of MPs, we developed a high-resolution global emission inventory, yielding total SSA-mediated MPs emissions in the range 3.85–23.32 tons yr–1. These findings identify SST as a key parameter regulating the release of marine MPs, which has significant implications for improving global emission inventories and atmospheric transport modeling.