The Ny-Ålesund Aerosol Cloud Experiment (NASCENT): Overview and First Results

J. T. Pasquier; R. O. David; G. Freitas; R. Gierens; Y. Gramlich; S. Haslett; G. Li; B. Schäfer; K. Siegel; J. Wieder; K. Adachi; F. Belosi; T. Carlsen; S. Decesari; K. Ebell; S. Gilardoni; M. Gysel-Beer; J. Henneberger; J. Inoue; Z. A. Kanji; M. Koike; Y. Kondo; R. Krejci; U. Lohmann; M. Maturilli; M. Mazzolla; R. Modini; C. Mohr; G. Motos; A. Nenes; A. Nicosia; S. Ohata; M. Paglione; S. Park; R. E. Pileci; F. Ramelli; M. Rinaldi; C. Ritter; K. Sato; T. Storelvmo; Y. Tobo; R. Traversi; A. Viola; P. Zieger
2022 | Bull. Amer. Meteor. Soc. (E2533-E2558)

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

Composition and mixing state of Arctic aerosol and cloud residual particles from long-term single-particle observations at Zeppelin Observatory, Svalbard

Kouji Adachi; Yutaka Tobo; Makoto Koike; Gabriel Freitas; Paul Zieger; Radovan Krejci
2022 | Atmos. Chem. Phys. | 22 (14421-14439)

The Arctic region is sensitive to climate change and is warming faster than the global average. Aerosol particles change cloud properties by acting as cloud condensation nuclei and ice-nucleating particles, thus influencing the Arctic climate system. Therefore, understanding the aerosol particle properties in the Arctic is needed to interpret and simulate their influences on climate. In this study, we collected ambient aerosol particles using whole-air and PM10 inlets and residual particles of cloud droplets and ice crystals from Arctic low-level clouds (typically, all-liquid or mixed-phase clouds) using a counterflow virtual impactor inlet at the Zeppelin Observatory near Ny-Ålesund, Svalbard, within a time frame of 4 years. We measured the composition and mixing state of individual fine-mode particles in 239 samples using transmission electron microscopy. On the basis of their composition, the aerosol and cloud residual particles were classified as mineral dust, sea salt, K-bearing, sulfate, and carbonaceous particles. The number fraction of aerosol particles showed seasonal changes, with sulfate dominating in summer and sea salt increasing in winter. There was no measurable difference in the fractions between ambient aerosol and cloud residual particles collected at ambient temperatures above 0 ∘C. On the other hand, cloud residual samples collected at ambient temperatures below 0 ∘C had several times more sea salt and mineral dust particles and fewer sulfates than ambient aerosol samples, suggesting that sea spray and mineral dust particles may influence the formation of cloud particles in Arctic mixed-phase clouds. We also found that 43 % of mineral dust particles from cloud residual samples were mixed with sea salt, whereas only 18 % of mineral dust particles in ambient aerosol samples were mixed with sea salt. This study highlights the variety in aerosol compositions and mixing states that influence or are influenced by aerosol–cloud interactions in Arctic low-level clouds.

Understanding and addressing the planetary crisis of chemicals and plastics.

Carney Almroth, B.; Cornell, S.E.; Diamond, M.L.; de Wit, C.A.; Fantke, P.; Wang, Z.
2022 | One Earth 5 (1070-1074)

Atmospheric Black Carbon Loadings and Sources over Eastern Sub- Saharan Africa Are Governed by the Regional Savanna Fires

Leonard Kirago; Örjan Gustafsson; Samuel M. Gaita; Sophie L. Haslett; H. Langley deWitt; Jimmy Gasore; Katherine E. Potter; Ronald G. Prinn; Maheswar Rupakheti; Jean de Dieu Ndikubwimana; Bonfils Safari; August Andersson
2022 | Environ. Sci. Technol.

Vast black carbon (BC) emissions from sub-Saharan Africa are perceived to warm the regional climate, impact rainfall patterns, and impair human respiratory health. However, the magnitudes of these perturbations are ill-constrained, largely due to limited ground-based observations and uncertainties in emissions from different sources. This paper reports multiyear concentrations of BC and other key PM2.5 aerosol constituents from the Rwanda Climate Observatory, serving as a regional receptor site. We find a strong seasonal cycle for all investigated chemical species, where the maxima coincide with large-scale upwind savanna fires. BC concentrations show notable interannual variability, with no clear long-term trend. The Δ14C and δ13C signatures of BC unambiguously show highly elevated biomass burning contributions, up to 93 ± 3%, with a clear and strong savanna burning imprint. We further observe a near-equal contribution from C3 and C4 plants, irrespective of air mass source region or season. In addition, the study provides improved relative emission factors of key aerosol components, organic carbon (OC), K+, and NO3−, in savanna-fires-influenced background atmosphere. Altogether, we report quantitative source constraints on Eastern Africa BC emissions, with implications for parameterization of satellite fire and bottom-up emission inventories as well as regional climate and chemical transport modeling.

Using Novel Molecular-Level Chemical Composition Observations of High Arctic Organic Aerosol for Predictions of Cloud Condensation Nuclei

Siegel, K.; Neuberger, A.; Karlsson, L.; Zieger, P.; Mattsson, F.; Duplessis, P.; Dada, L.; Daellenbach, K.; Schmale, J.; Baccarini, A.; Krejci, R.; Svenningsson, B.; Chang, R.; Ekman, A.; Riipinen, I.; Mohr, C.
2022 | Environ. Sci. Technol. | 56 (19) (13888-13899)
aerosol chemistry , aerosol−cloud interactions , atmospheric aerosol , CCN closure , chemical ionization mass spectrometry (CIMS) , cloud droplet activation , High Arctic

Predictions of cloud droplet activation in the late summertime (September) central Arctic Ocean are made using κ-Köhler theory with novel observations of the aerosol chemical composition from a high-resolution time-of-flight chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an aerosol mass spectrometer (AMS), deployed during the Arctic Ocean 2018 expedition onboard the Swedish icebreaker Oden. We find that the hygroscopicity parameter κ of the total aerosol is 0.39 ± 0.19 (mean ± std). The predicted activation diameter of ∼25 to 130 nm particles is overestimated by 5%, leading to an underestimation of the cloud condensation nuclei (CCN) number concentration by 4–8%. From this, we conclude that the aerosol in the High Arctic late summer is acidic and therefore highly cloud active, with a substantial CCN contribution from Aitken mode particles. Variability in the predicted activation diameter is addressed mainly as a result of uncertainties in the aerosol size distribution measurements. The organic κ was on average 0.13, close to the commonly assumed κ of 0.1, and therefore did not significantly influence the predictions. These conclusions are supported by laboratory experiments of the activation potential of seven organic compounds selected as representative of the measured aerosol.

ACS Environmental Au – How to Improve the Reach of Your Open Access Research

Praetorius, A.; Cousins, I.T.
2022 | ACS Environ. Au | 2 (5) (373-375)

Influences of climate change on long-term time series of persistent organic pollutants (POPs) in Arctic and Antarctic biota.

Vorkamp,K.; Carlsson, P.; Corsolini, S.; de Wit, C.A.; Dietz, R.; Gribble, M.O.; Houde, M.; Kalia, V.; Letcher, R.J.; Morris, A.; Rigét, F.F.; Routti, H.; Muir, D.C.G.
2022 | Environ. Sci.: Processes Impacts | 24 (1643)

Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea

Birgit Wild; Natalia Shakhova; Oleg Dudarev; Alexey Ruban; Denis Kosmach; VladimirTumskoy; Tommaso Tesi; Hanna Grimm; Inna Nybom; Felipe Matsubara; Helena Alexanderson; Martin Jakobsson; Alexey Mazurov; Igor Semiletov; Örjan Gustafsson
2022 | Nat. Commun. | 13

Emission of primary bioaerosol particles from Baltic seawater

Gabriel P. Freitas; Christian Stolle; Paul H. Kaye; Warren Stanley; Daniel P. R. Herlemann; Matthew Salter; Paul Zieger
2022 | Environ. Sci. Atmos.

Bioaerosols are particles of biological origin with various important atmospheric implications, for example, within cloud formation where bioaerosols can act as cloud condensation or ice nuclei. Their sources and properties, however, are poorly understood. We conducted a controlled sea spray experiment to determine the properties and emission of primary biological aerosol particles (PBAP) originating from Baltic seawater. Using a single-particle fluorescence and light-scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), we differentiated PBAP within sea spray aerosol (SSA). Overall, approximately 1 in 104 particles larger than 0.8 μm in diameter were classified as PBAP. The optically-determined morphology of the nascent and fluorescent SSA particles showed a clear transition in symmetry and elongation most likely due to changes in the biogeochemical properties of the surface water. These shifts were also reflected in a clear change of the bacterial community composition of the aerosol and seawater as determined by 16S rRNA-gene analysis, which were significantly distinct from each other, suggesting a preferential emission of specific bacteria to the atmosphere. Our results demonstrate the capability of the MBS to identify and count PBAP within SSA on a single-particle basis and will help to better constrain the emission of marine PBAP and their dependence on the seawater's biogeochemical properties.

The Effect of Seawater Salinity and Seawater Temperature on Sea Salt Aerosol Production

2022 | J. Geophys. Res.-Atmos. | 127

To improve our understanding of the impact of sea salt aerosols (SSA) on the Earth's climate, it is critical to understand the physical mechanisms which determine the size-resolved SSA production flux. Of the factors affecting SSA emissions, seawater salinity has perhaps received the least attention in the literature and previous studies have produced conflicting results. Here, we present a series of laboratory experiments designed to investigate the role of salinity on aerosol production from artificial seawater using a continuous plunging jet. During these experiments, the aerosol and surface bubble size distributions were monitored while the salinity was decreased from 35 to 0 g kg−1. Three distinct salinity regimes were identified: (a) A high salinity regime, 10–35 g kg−1, where lower salinity resulted in only minor reductions in particle number flux but notable reductions in particle volume flux; (b) an intermediate salinity regime, 5–10 g kg−1, with a local maximum in particle number flux; (c) a low salinity regime, <5 g kg−1, characterized by a rapid decrease in particle number flux at lower salinities and dominated by small particles and larger bubbles. We discuss the implications of our results through comparison of the size-resolved aerosol flux and the surface bubble population at different salinities. Finally, by varying the seawater temperature at three specific salinities we have also developed a simple parameterization of the particle production flux as a function of seawater temperature and salinity. The range of seawater salinity and temperature studied is representative of the global oceans and lower salinity water bodies such as the Baltic Sea.

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