Quantified effect of seawater biogeochemistry on the temperature dependence of sea spray aerosol fluxes

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 number-based sea spray emission fluxes. The 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 a significant increase in the sea spray total concentration at temperatures below 8 ∘C. Specifically, at 2 ∘C, there was an average 4-fold increase compared to the initial concentration at ambient temperatures. This temperature dependence was more pronounced for smaller-sized sea spray particles (i.e., nucleation and Aitken modes). Moreover, the temperature dependence varied based on the seawater type and its 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 in subtropical seawaters. The temperature dependence of the sea spray flux was found to be inversely proportional to the abundance of the cyanobacterium Synechococcus in seawater. This relationship allows for parameterizing the temperature dependence of sea spray emission fluxes based on Synechococcus, which may be utilized in future modeling exercises.