The Impact of Atmospheric Photochemistry on Marine Aerosols: Ice Nucleation and Droplet Activation

Oceans cover more than 70% of the Earth’s surface and are a critical component of global climate system. Sea spray aerosols (SSAs), derived from ocean surfaces, represent a unique and significant source of ice nucleating particles (INPs) and cloud condensation nuclei (CCN), yet their contribution to cloud processes remains poorly understood, with substantial uncertainties surrounding their role in climate systems. To address this gap, we investigate the atmospheric photochemical effects on marine aerosols and their implications for ice nucleation and droplet activation through controlled laboratory experiments.

Our study utilizes two key experimental systems: the AIDAd (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber and PINE (Portable Ice Nucleation Experiment). AIDAd, with its temperature-controlled walls capable of simulating temperature range from +30 °C to −55 °C and tropospheric cooling rates up to 10 °C min⁻¹, allows for precise investigations of aerosol-cloud interactions. PINE measures INP concentrations under mixed-phase cloud conditions at temperatures ranging from −10 °C to −38 °C.

For our experiments, marine aerosols were generated from three distinct seawater samples collected from diverse oceanic regions: the Indian Ocean, the South China Sea, and Jangmok Port (Korea). These samples capture the variability of natural marine environments and provide a comprehensive basis for understanding the effects of geographical and biological diversity on aerosol properties. These samples underwent photochemical treatment using a custom-built solar radiation simulator to replicate atmospheric conditions. The irradiated aerosols are subsequently analyzed using the AIDAd chamber and PINE, and further chemical analysis are done to evaluate changes in composition and ice nucleation potential.

This study provides critical insights into the interplay between marine aerosol sources, photochemistry, and cloud formation. By integrating data from AIDAd and PINE, we aim to unravel the mechanisms underlying ice nucleation and droplet activation of marine aerosols under simulated atmospheric conditions. Our findings will contribute to reducing uncertainties in the representation of marine aerosol-cloud interactions in climate models, enhancing our understanding of their role in the Earth's climate system.