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  • 1. Porter, Grace C. E.
    et al.
    Adams, Michael P.
    Brooks, Ian M.
    Ickes, Luisa
    Karlsson, Linn
    Stockholms universitet, Institutionen för miljövetenskap.
    Leck, Caroline
    Stockholms universitet, Meteorologiska institutionen (MISU).
    Salter, Matthew E.
    Stockholms universitet, Institutionen för miljövetenskap.
    Schmale, Julia
    Siegel, Karolina
    Stockholms universitet, Meteorologiska institutionen (MISU).
    Sikora, Sebastien N. F.
    Tarn, Mark D.
    Vüllers, Jutta
    Wernli, Heini
    Zieger, Paul
    Stockholms universitet, Institutionen för miljövetenskap.
    Zinke, Julika
    Stockholms universitet, Institutionen för miljövetenskap.
    Murray, Benjamin J.
    Highly Active Ice-Nucleating Particles at the Summer North Pole2022Inngår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 127, nr 6, artikkel-id e2021JD036059Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The amount of ice versus supercooled water in clouds is important for their radiative properties and role in climate feedbacks. Hence, knowledge of the concentration of ice-nucleating particles (INPs) is needed. Generally, the concentrations of INPs are found to be very low in remote marine locations allowing cloud water to persist in a supercooled state. We had expected the concentrations of INPs at the North Pole to be very low given the distance from open ocean and terrestrial sources coupled with effective wet scavenging processes. Here we show that during summer 2018 (August and September) high concentrations of biological INPs (active at >−20°C) were sporadically present at the North Pole. In fact, INP concentrations were sometimes as high as those recorded at mid-latitude locations strongly impacted by highly active biological INPs, in strong contrast to the Southern Ocean. Furthermore, using a balloon borne sampler we demonstrated that INP concentrations were often different at the surface versus higher in the boundary layer where clouds form. Back trajectory analysis suggests strong sources of INPs near the Russian coast, possibly associated with wind-driven sea spray production, whereas the pack ice, open leads, and the marginal ice zone were not sources of highly active INPs. These findings suggest that primary ice production, and therefore Arctic climate, is sensitive to transport from locations such as the Russian coast that are already experiencing marked climate change.

  • 2.
    Siegel, Karolina
    Stockholms universitet, Meteorologiska institutionen (MISU).
    Chemical composition of summertime High Arctic aerosols2020Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents new insights into the chemical composition of semi-volatile compounds in aerosol samples collected in the central Arctic Ocean close to the North Pole in September 2018. The central Arctic Ocean is an inaccessible location due to the lack of land areas along with heavy pack ice conditions. Therefore, large knowledge gaps remain to understand the Arctic climate system, and in particular the role of aerosol particles in its pristine atmosphere.

    The chemical composition of the aerosol samples was analysed on a molecular level using High Resolution Time-of-Flight Chemical Ionization Mass Spectrometry coupled to a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). The analysis revealed a significant signal from compounds that are likely from marine sources. One important precursor for marine aerosols is dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae in the Arctic Ocean. DMS oxidises in the atmosphere to produce oxidation products that can contribute to aerosol growth. Analysis of air mass origin with backward trajectories showed that the highest ambient DMS concentrations originated from marine areas around the pack ice. However, no correlation could be shown within the pack ice between ambient DMS and its oxidation product methanesulfonic acid (MSA) in the particle phase.

    As FIGAERO-HRToF-CIMS is commonly used in areas with higher particle concentrations and has never been used in the central Arctic before, this thesis further demonstrates its suitability for measurements of aerosol chemical composition in this remote region.

  • 3.
    Siegel, Karolina
    et al.
    Stockholms universitet, Institutionen för miljövetenskap.
    Neuberger, Almuth
    Stockholms universitet, Institutionen för miljövetenskap.
    Karlsson, Linn
    Stockholms universitet, Institutionen för miljövetenskap.
    Zieger, Paul
    Stockholms universitet, Institutionen för miljövetenskap.
    Mattsson, Fredrik
    Stockholms universitet, Institutionen för miljövetenskap.
    Duplessis, Patrick
    Dada, Lubna
    Daellenbach, Kaspar
    Schmale, Julia
    Baccarini, Andrea
    Krejci, Radovan
    Stockholms universitet, Institutionen för miljövetenskap.
    Svenningsson, Birgitta
    Chang, Rachel
    Ekman, Annica M. L.
    Stockholms universitet, Meteorologiska institutionen (MISU).
    Riipinen, Ilona
    Stockholms universitet, Institutionen för miljövetenskap.
    Mohr, Claudia
    Stockholms universitet, Institutionen för miljövetenskap.
    Using Novel Molecular-Level Chemical Composition Observations of High Arctic Organic Aerosol for Predictions of Cloud Condensation Nuclei2022Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 56, nr 19, s. 13888-13899Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

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