Sea spray aerosols (SSAs) make up a substantial proportion of aerosols in the global atmosphere and, especially when considering marine haze and cloud layers, can have a large impact on cloud formation and atmospheric radiative balance. Although SSA has the highest cloud condensation nuclei (CCN) activation potential, the majority of its population, residing in sub-micrometre sizes, are often obscured by non-sea-spray CCN. Quantification of SSA-derived CCN is fundamental in understanding the radiative budget. Recent approaches to estimate the sub-micrometre SSA employed a free-monomodal lognormal analysis that depicts the global oceanic CCN population comprising less than 30% SSA. Here we derive SSA distributions from a unique five-year dataset of aerosol microphysics and hygroscopicity (water uptake ability) over Atlantic waters. This approach utilizes the distinctive ultra-high hygroscopicity signature of inorganic sea salt and is able to identify the sub-micrometre sea spray down to 35 nm diameter with high time and size resolution. In stark contrast to previous studies, the hygroscopicity coupled multimodal fitting analysis yields SSA-derived CCN as much as 500% in excess of estimates produced using the free-monomodal approach. Our results suggest the contribution of SSA to global CCN, particularly Aitken mode SSA, has probably been overlooked.
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The meteorological parameters can be found at https://www.met.ie/. The monthly global reanalysis of the distribution of U10 can be found through https://doi.org/10.24381/cds.bd0915c6. All data are available in the repository: https://doi.org/10.17632/gjdd5r4ywf.1. Source data are provided with this paper.
The R codes used to analyse the data are available upon reasonable request.
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We thank J. Bialek for operating HTDMA at MHD from 2008 to 2014. The work was supported by the Science Foundation Ireland (Research Centre for Energy, Climate and Marine Research and Innovation, SFI Spokes Award 14/SP/2740 (Ocean Monitoring)); Environmental Protection Agency Ireland (No. AEROSOURCE, 2016-CCRP-MS-31); the National Natural Science Foundation of China (No. 41925015); the Chinese Academy of Sciences (No. XDB40000000 and No. ZDBS-LY-DQC001); the Cross Innovative Team fund from the State Key Laboratory of Loess and Quaternary Geology (No. SKLLQGTD1801). The Chinese Scholarship Council (No. 201706310154) is acknowledged for the financial support for W.X.
The authors declare no competing interests.
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Xu, W., Ovadnevaite, J., Fossum, K.N. et al. Sea spray as an obscured source for marine cloud nuclei. Nat. Geosci. 15, 282–286 (2022). https://doi.org/10.1038/s41561-022-00917-2