Marine aerosols are a major source of uncertainty in climate forcing estimates because marine clouds are highly sensitive to the cloud condensation nuclei (CCN) and ice nucleating particles (INP) provided by these aerosols. Over the remote oceans, CCN and INP populations are shaped by primary sea spray and secondary formation, and are increasingly influenced by transported dust, smoke, and anthropogenic pollution. Marine aerosols are also vertically coupled, but this coupling remains poorly quantified: the free troposphere delivers aerosols down into the marine boundary layer, while the marine boundary layer feeds particles and precursors back aloft. Constraining the resulting climate impacts requires ambient observations, laboratory experiments and modelling across scales to be brought together.

This session brings together work on the sources, formation processes and impacts of marine aerosols across the full depth of the marine atmosphere - from the boundary layer to the free troposphere - and across primary, secondary and transported origins. We welcome observations from diverse platforms, alongside laboratory experiments and modelling from regional to global scales. Studies that connect emission and formation processes to cloud and climate response are particularly encouraged.

Topics of interest include, but are not limited to:
• Primary marine aerosol: production mechanisms, fluxes, size distribution, composition, CCN/INP activity
• Secondary marine aerosol: iodine, sulfur, ammonia, amine and organic emissions and mechanisms, their chemical transformation and new particle formation
• Transported aerosols: dust, smoke, anthropogenic and volcanic plumes over the ocean, their fates and impacts
• Vertical coupling: entrainment, convective transport and detrainment, aerosol and precursor exchange between the marine boundary layer and free troposphere
• Marine aerosol-cloud interactions: CCN/INP control of clouds; cloud processing and wet removal of aerosols; radiative and precipitation responses
• Perturbations of the marine background: shipping emissions and fuel-sulfur regulation, and proposed interventions such as marine cloud brightening
• Climate response and model evaluation: marine aerosol radiative effects and feedbacks, the pre-industrial baseline and future projections, and representation of marine aerosol in Earth system models