Wind-Driven Influence on Submicron Sea Spray Aerosol Chemical Mixing State

Sea spray aerosols (SSA) influence cloud properties by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INP), yet the factors controlling their climate-relevant properties remain poorly constrained. Current models often oversimplify SSA composition while neglecting the potential impact of wind speed variability. Here, we present the first direct measurements of SSA chemical mixing state under controlled wind speeds (11–18 m/s) in the Scripps Ocean-Atmosphere Research Simulator (SOARS). These experiments isolate the impact of wind speed on SSA chemical mixing state while limiting biological variability. Increasing wind speed drives a transition toward more homogeneous, salt-enriched SSA, increasing from 46% at 11 m/s to 80% at 18 m/s. Simultaneously, aerosolized coastal water pollutants decline sharply, while organic-enriched and biologically influenced particles increase, consistent with wind-driven disruption of the sea surface microlayer. As the size of SSA particles approaches the CCN-relevant range, we observe enhanced organic fractions, largely associated with sea salt. Moreover, the rise in larger accumulation mode SSA (>700 nm) enriched with biological species at high wind speeds is consistent with observed increases in INP concentrations in parallel SOARS measurements. This study demonstrates how wind-driven changes alter SSA mixing state, underscoring the need to incorporate these effects when modeling SSA climate properties and aerosol–cloud interactions.