Linking marine phytoplankton emissions, meteorological processes, and downwind particle properties with FLEXPART

Abstract

Abstract. Marine biogenic particle contributions to atmospheric aerosol concentrations are not well understood though they are important for determining cloud optical and cloud-nucleating properties. Here we examine the relationship between marine aerosol measurements (with satellites and model fields of ocean biology) and meteorological variables during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). NAAMES consisted of four field campaigns between November 2015 and April 2018 that aligned with the four major phases of the annual phytoplankton bloom cycle. The FLEXible PARTicle (FLEXPART) Lagrangian particle dispersion model is used to spatiotemporally connect these variables to ship-based aerosol and dimethyl sulfide (DMS) observations. We find that correlations between some aerosol measurements with satellite-measured and modeled variables increase with increasing trajectory length, indicating that biological and meteorological processes over the air mass history are influential for measured particle properties and that using only spatially coincident data would miss correlative connections that are lagged in time. In particular, the marine non-refractory organic aerosol mass correlates with modeled marine net primary production when weighted by 5 d air mass trajectory residence time (r=0.62). This result indicates that non-refractory organic aerosol mass is influenced by biogenic volatile organic compound (VOC) emissions that are typically produced through bacterial degradation of dissolved organic matter, zooplankton grazing on marine phytoplankton, and as a by-product of photosynthesis by phytoplankton stocks during advection into the region. This is further supported by the correlation of non-refractory organic mass with 2 d residence-time-weighted chlorophyll a (r=0.39), a proxy for phytoplankton abundance, and 5 d residence-time-weighted downward shortwave forcing (r=0.58), a requirement for photosynthesis. In contrast, DMS (formed through biological processes in the seawater) and primary marine aerosol (PMA) concentrations showed better correlations with explanatory biological and meteorological variables weighted with shorter air mass residence times, which reflects their localized origin as primary emissions. Aerosol submicron number and mass negatively correlate with sea surface wind speed. The negative correlation is attributed to enhanced PMA concentrations under higher wind speed conditions. We hypothesized that the elevated total particle surface area associated with high PMA concentrations leads to enhanced rates of condensation of VOC oxidation products onto PMA. Given the high deposition velocity of PMA relative to submicron aerosol, PMA can limit the accumulation of secondary aerosol mass. This study provides observational evidence for connections between marine aerosols and underlying ocean biology through complex secondary formation processes, emphasizing the need to consider air mass history in future analyses.

Editorial: Unraveling Mechanisms Underlying Annual Plankton Blooms in the North Atlantic and Their Implications for Biogenic Aerosol Properties and Cloud Formation

“…This finding is consistent with processes of biogenic VOC emissions and subsequent photolysis in the atmosphere allowing detection significantly distant from source regions, and also implies an important role of wind speed and trajectory (Saliba et al, 2019(Saliba et al, , 2020. Future composition and microphysical measurements are still needed to better quantify radiative impacts of the direct and indirect aerosol effects sourced from the ocean (Saliba et al, 2019(Saliba et al, , 2020Wilbourn et al, 2020;Sanchez et al, 2021;Bell et al;Hendrickson et al).…”

“…Notably, these findings demonstrate the long-hypothesized link between phytoplankton and atmospheric aerosols and are a step forward in understanding processes producing aerosols in the marine environment (Brooks and Thornton, 2018). Even so, debate persists regarding quantitative budgets (Bates et al, 2020) and the direct flux of marine aerosol remains unquantified (Sanchez et al, 2018(Sanchez et al, , 2021.…”

“…Total aerosol mass was not correlated with surface layer dissolved organic carbon mass, indicating aerosol production through multiple processes with difference timescales (Sanchez et al, 2021). DMS and primary marine aerosol correlate on short air-mass timescales (i.e., local sources).…”

Measurement report: Cloud Processes and the Transport of Biological Emissions Regulate Southern Ocean Particle and Cloud Condensation Nuclei Concentrations

“…Typically, clouds contain a range of peak supersatu- rations, which are controlled by the strength of the updraft and the cloud droplet number concentration (Hudson and Svensson, 1995;Pawlowska and Grabowski, 2006;Siebert and Shaw, 2017). The effective supersaturation accounts for the CCN that have activated adiabatically near cloud base and subsequently dried through sub-adiabatic mixing processes (Sanchez et al, 2017). In general, the observed CDNC weakly correlate to the effective supersaturation (Fig.…”

“…In the event that the cloud droplets do not precipitate, the evaporated particles are larger than their original size since aqueous oxidation of volatile compounds (i.e., DMS, MSA, SO 2 and nitric acid) have formed non-volatile sulfates and nitrates that remain in the particle phase. This added mass eventually shifts Aitken-mode particles to the accumulation mode (Hoppel et al, 1986;Hudson et al, 2015;Kaufman and Tanré, 1994;Sanchez et al, 2017;Schmale et al, 2019). Results from McCoy et al (2015) show that, despite the ambiguous results from focused modeling and observational studies of such aerosol processes, their general global model simulations of natural aerosol account for more than half the spatial and temporal variability in the satellite-derived CDNC over the SO.…”