Sellegri, Karine, Barthelmess, Theresa, Trueblood, Jonathan, Cristi, Antonia, Freney, Evelyn, Rose, Clémence, Barr, Neill, Harvey, Mike, Safi, Karl, Deppeler, Stacy, Thompson, Karen, Dillon, Wayne, Engel, Anja and Law, Cliff (2023) Quantified effect of seawater biogeochemistry on the temperature dependence of sea spray aerosol fluxes. Atmospheric Chemistry and Physics, 23 (20). pp. 12949-12964. DOI 10.5194/acp-2022-790.

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Abstract

Future change in sea surface temperature may influence climate via various air-sea feedbacks and pathways. In this study, we investigate the influence of surface seawater biogeochemical composition on the temperature dependence of sea spray number emission fluxes. Dependence of sea spray fluxes was investigated in different water masses (i.e. subantarctic, subtropical and frontal bloom) with contrasting biogeochemical properties across a temperature range from ambient (13–18 °C) to 2 °C, using seawater circulating in a plunging jet sea spray generator. We observed sea spray total concentration to increase significantly at temperatures below 8 °C, with an average 4-fold increase at 2 °C relative to initial concentration at ambient temperatures. This temperature dependence was more pronounced for smaller size sea spray particles (i.e. nucleation and Aitken modes). Moreover, temperature dependence varied with water mass type and so biogeochemical properties. While the sea spray flux at moderate temperatures (8–11 °C) was highest in frontal bloom waters, the effect of low temperature on the sea spray flux was highest with subtropical seawaters. The temperature dependence of sea spray flux was also inversely proportional to the seawater cell abundance of the cyanobacterium Synechococcus, which facilitated parameterization of temperature dependence of sea spray emission fluxes as a function of Synechococcus for future implementation in modelling exercises.

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