Substantial Seasonal Contribution of Observed Biogenic Sulfate Particles to Cloud Condensation Nuclei

Abstract

Biogenic sources contribute to cloud condensation nuclei (CCN) in the clean marine atmosphere, but few measurements exist to constrain climate model simulations of their importance. The chemical composition of individual atmospheric aerosol particles showed two types of sulfate-containing particles in clean marine air masses in addition to mass-based Estimated Salt particles. Both types of sulfate particles lack combustion tracers and correlate, for some conditions, to atmospheric or seawater dimethyl sulfide (DMS) concentrations, which means their source was largely biogenic. The first type is identified as New Sulfate because their large sulfate mass fraction (63% sulfate) and association with entrainment conditions means they could have formed by nucleation in the free troposphere. The second type is Added Sulfate particles (38% sulfate), because they are preexisting particles onto which additional sulfate condensed. New Sulfate particles accounted for 31% (7 cm−3) and 33% (36 cm−3) CCN at 0.1% supersaturation in late-autumn and late-spring, respectively, whereas sea spray provided 55% (13 cm−3) in late-autumn but only 4% (4 cm−3) in late-spring. Our results show a clear seasonal difference in the marine CCN budget, which illustrates how important phytoplankton-produced DMS emissions are for CCN in the North Atlantic.

Observations of Aerosol‐Cloud Interactions During the North Atlantic Aerosol and Marine Ecosystem Study

“…Our analysis of NAAMES‐1 and NAAMES‐2 cloud properties in combination with the analysis of aerosols by Sanchez et al () suggests that cloud microphysical properties over the North Atlantic Ocean are being influenced by the phytoplankton bloom, leading to a cloud brightening effect. However, meteorological differences between the campaigns also play an important role, and therefore, the magnitude of the cloud property changes due to biogenic activity remains uncertain.…”

“…A large increase in aerosol mass and CCN concentrations is observed between the NAAMES-1 and NAAMES-2 campaigns. Sanchez et al (2018) used a combination of radon concentrations, combustion tracers, and back trajectories to determine that few aerosols originated from continents during NAAMES-1 and NAAMES-2 with most aerosols having biogenic marine sources. These findings also agree with previous work that found that variances in marine CCN concentrations can be largely explained by DMS from a phytoplankton bloom over the North Atlantic Ocean (Cavalli et al, 2004;Yoon et al, 2007) and in other oceanic basins (Andreae et al, 1995;Charlson et al, 1987;Hegg et al, 1991).…”

“…Radiative forcing due to changes in cloud properties in the remote and unpolluted marine atmosphere is particularly sensitive to changes to CCN (Twomey, 1991;Wood, 2005). Several regional studies suggest that changes in marine CCN concentrations are related to variations in dimethlysulphide (DMS; Charlson et al, 1987;Andreae et al, 1995;Hegg et al, 1991;Sanchez et al, 2018). These variations in marine boundary layer DMS have long been linked to a seasonal cycle in phytoplankton activity, which is highly variable in time and location (Bates et al, 1998;Quinn et al, 2000).…”

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…They attributed this to the important influence of entrainment of particles from the free troposphere to the MBL. Sanchez et al () further explored the seasonal aerosol variability during NAAMES and concluded that changes in the ocean ecosystem and resulting DMS emissions give rise to an increased aerosol SO 4 2‐ contribution to CCN observed during springtime bloom periods, both from new particle formation and from condensation onto existing particles. The NAAMES aerosol‐cloud sampling strategy followed a similar set of stacked aircraft legs used by others in ACI‐focused campaigns (Crosbie et al, ; Sorooshian et al, ) and sampled clouds under both typical marine aerosol loadings (order of hundreds per cm 3 of air) and severely aerosol‐depleted conditions (order of tens per cm 3 of air).…”

Sea-surface dimethylsulfide (DMS) concentration from satellite data at global and regional scales

“…Nevertheless, atmospheric studies powered by new analytical techniques (Kulmala et al, 2014) and modeling have shown instances where marine DMS controls ultrafine aerosol particle formation in the Arctic (Leaitch et al, 2013;Park et al, 2017), temperate North Atlantic (Sanchez et al, 2018), Antarctica (Yu and Luo, 2010) and the tropical South Pacific atmospheres (Modini et al, 2009). Moreover, Quinn et al (2017) recently reported that DMS-derived aerosols dominate cloud condensation nuclei populations over most of the global ocean.…”