Linking Marine Biogeochemistry and Primary Organic Marine Aerosol

Tuesday, May 13, 2014 - 07:00
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Surface-active organic molecules are strongly enriched in primary sea spray aerosol (SSA) as a result of their adsorption onto bubble films, and accumulation in the sea surface microlayer. We have developed a new modeling framework that predicts the enrichment of organics in the aerosol on the basis of their surface activity, which is now being implemented into the Community Atmosphere Model (CAM) for the purpose of atmospheric simulations, and which has the potential to be fully coupled to the biogeochemistry codes in the Parallel Ocean Program (POP). We utilize output from POP biogeochemistry to describe the geographic distribution of several classes of organic compounds in the ocean. We assign chemical properties to each class based on laboratory measurements, and use the Langmuir adsorption isotherm to predict the organic mass fraction of the generated SSA. Our model has the potential to resolve discrepancies in recent observations of sea spray aerosol composition across several ocean regions, which have led to differing conclusions regarding the correlation of chlorophyll-a and SSA organic mass fraction. In particular, our model predicts a strong positive correlation of chlorophyll-a and SSA organic mass fraction in nutrient-rich regions such as the North Atlantic, largely driven by the seasonal cycle of phytoplankton blooms, but less variability and a negatively correlated seasonal cycle in nutrient-poor regions such as the southeast Pacific. This represents an advance in understanding of differences between the drivers of SSA composition in different ocean regions.