Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols

Abstract

Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.

Pan-Arctic seasonal cycles and long-term trends of aerosol properties from 10 observatories

“…Third, an assessment of whether the currently monitored aerosol properties are appropriate to capture changes in natural aerosol compounds is needed. Source apportionment based on speciated organic aerosol components is currently lacking except for a few short-term case studies (Moschos et al, 2022b). Those together with isotopic analyses of carbon, nitrogen and sulfur can shed light on natural aerosol changes.…”

“…Those need to be identified using statistical tools or models. For the latter, observations and speciation of organic aerosol with spatial coverage in the Arctic, and in particular secondary organic aerosol, are desperately needed for better source apportionment (Petäjä et al, 2020;Moschos et al, 2022b). Analyses based on short-term efforts clearly show the potential of various analysis techniques (mass spectrometry or Fourier transform infrared spectral analysis) to isolate signatures of anthropogenic versus natural organic aerosol contribution (Fu et al, 2009;Kawamura et al, 2010;Leaitch et al, 2018;Willis et al, 2017).…”

Understanding Sources and Drivers of Size-Resolved Aerosol in the High Arctic Islands of Svalbard Using a Receptor Model Coupled with Machine Learning

“…The response of secondary aerosol to Arctic warming is more complicated because it has both anthropogenic and natural origins. 12 A decrease in biogenic aerosol above 0 °C may be counterbalanced by an increase in secondary aerosol. Mineral dust : The nonlinear response of local dust to temperature with an inflection point at ∼0 °C suggests that both the seasonality and emissions will change in a warming Arctic.…”

“…The response of secondary aerosol to Arctic warming is more complicated because it has both anthropogenic and natural origins. 12 A decrease in biogenic aerosol above 0 °C may be counterbalanced by an increase in secondary aerosol.…”

“… 5 Positive matrix factorization (PMF) can quantitatively separate source-related factors for both number and volume/mass concentrations. 9 − 12 While there are a few studies of source apportionment of Arctic aerosols in mass, 9 , 12 no studies to date have quantified source contributions to PN, which is crucial for cloud formation. Furthermore, previous studies suggested that annual cycles of Arctic aerosols with different diameters are governed by different processes.…”