Temperature and Composition Dependence of Sea Spray Aerosol Production

Abstract

A discrepancy between laboratory and field‐derived parameterizations for the dependence of sea spray aerosol (SSA) particle number concentrations (Np) and size distributions on water temperature (Tw) exists. Here we address this discrepancy by quantifying the Tw dependence of SSA production over the range −2–25 °C for laboratory‐generated particles using a marine aerosol reference tank (MART), a miniature MART (miniMART), and a plunging jet. Four water types were considered: NaCl water, reef salt (RS) water, filtered and autoclaved reef salt (FARS), and filtered but not autoclaved seawater (NASW). For NaCl, RS, and FARS water the Np exhibited a moderate, monotonic increase with Tw for all generation methods (sensitivity of 2.1–4.1%/°C). This contrasts with some previous laboratory studies but is consistent with parameterizations derived from ambient observations. The reconciliation of laboratory results with these parameterizations supports their use in global models. The Tw sensitivity also increased with particle size in the submicron size range. This indicates the fraction of primary SSA that can act as cloud condensation nuclei has a different sensitivity to Tw than the total particle number. The particle production for actual seawater (NASW) differed from the other water types, exhibiting complex, irreproducible behavior with no clear Tw dependence due most likely to biologically or physically driven temporal evolution of seawater composition. This suggests that variability in seawater composition may have as large an impact as temperature on actual SSA production. These observations provide new constraints and context for understanding the dependence of SSA production on water temperature and composition.

The sensitivity of Southern Ocean aerosols and cloud microphysics to sea spray and sulfate aerosol production in the HadGEM3-GA7.1 chemistry-climate model

“…Along with Jaeglé et al (2011), other studies have found that SSA concentrations are correlated with sea surface temperature (Mårtensson et al, 2003;Sellegri et al, 2006;Sofiev et al, 2011;Grythe et al, 2014). More recently, Forestieri et al (2018) demonstrated that variability in seawater composition may have just as large an impact on SSA production as temperature. Nonetheless, our results demonstrate that for the Southern Ocean during winter when SSA is the dominant contributor to AOD, reducing the wind speed dependency of SSA production results in good agreement between the model and observations.…”

Variability in Marine Plankton Ecosystems Are Not Observed in Freshly Emitted Sea Spray Aerosol Over the North Atlantic Ocean

“…Alpert et al (2015) showed an increase in the number flux of up to three times in actively growing bacteria and phytoplankton mesocosm experiments while Christiansen et al (2019) showed a decrease in the number production flux with increases in algal biomass. Tyree et al (2007) and Forestieri et al (2018) reported mixed responses of the number production flux when including organic matter. This is clearly an area for further study.…”

Revisiting the Impact of Sea Salt on Climate Sensitivity

“…Multimodel assessments (Collins et al, 2017) are ongoing to characterize the spread in sea salt feedbacks across current climate models. Future work will aim at leveraging recent field and laboratory observational constraints (Bian et al, 2019;Forestieri et al, 2018;Saliba et al, 2019) on the response of sea salt to temperature. Of particular importance is the response of the sea salt size distribution to warming with recent experiments showing an increase sensitivity with size, which may modulate both the sea salt direct effect and the contribution of sea salt to the cloud condensation nuclei population (Forestieri et al, 2018;Modini et al, 2015;Partanen et al, 2014;Saliba et al, 2019;Quinn et al, 2017).…”

“…Future work will aim at leveraging recent field and laboratory observational constraints (Bian et al, 2019;Forestieri et al, 2018;Saliba et al, 2019) on the response of sea salt to temperature. Of particular importance is the response of the sea salt size distribution to warming with recent experiments showing an increase sensitivity with size, which may modulate both the sea salt direct effect and the contribution of sea salt to the cloud condensation nuclei population (Forestieri et al, 2018;Modini et al, 2015;Partanen et al, 2014;Saliba et al, 2019;Quinn et al, 2017). Our work also highlights that changes in sea salt lifetime with warming as well as the representation of AMOC and low-level clouds, all of which remain uncertain (Bony & Dufresne, 2005;Cheng et al, 2013;Struthers et al, 2013), also play important roles in modulating how changes in sea salt impact climate sensitivity.…”

“…In particular, recent field (Grythe et al, 2014;Jaeglé et al, 2011;Ovadnevaite et al, 2014;Saliba et al, 2019) and laboratory experiments (Callaghan et al, 2014;Forestieri et al, 2018;Zábori et al, 2012) show that sea salt emissions tend to increase with SST, which may reflect changes in water kinematic viscosity and bubble behavior with temperature (Norris et al, 2013). These recent advances suggest that sea salt emissions may increase significantly with global warming (e.g., 320 Tg K −1 , 7% K −1 , Jaeglé et al, 2011; 2.1% K −1 for number concentration, Forestieri et al, 2018). Such sensitivity is not included in most 10.1029/2019GL085601 climate models to date, which suggests that the climate feedback associated with sea salt emissions may be underestimated.…”