Increasing Sea Surface Temperature Suppresses Sea Spray Aerosol-Mediated Microplastics Emission

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.