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Duplessis, P., Karlsson, L., Baccarini, A., Wheeler, M., Leaitch, W. R., Svenningsson, B., . . . Chang, R.-W. Y. (2024). Highly Hygroscopic Aerosols Facilitate Summer and Early-Autumn Cloud Formation at Extremely Low Concentrations Over the Central Arctic Ocean. Journal of Geophysical Research - Atmospheres, 129(2), Article ID e2023JD039159.
Open this publication in new window or tab >>Highly Hygroscopic Aerosols Facilitate Summer and Early-Autumn Cloud Formation at Extremely Low Concentrations Over the Central Arctic Ocean
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2024 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 129, no 2, article id e2023JD039159Article in journal (Refereed) Published
Abstract [en]

Arctic clouds are sensitive to atmospheric particles since these are sometimes in such low concentrations that clouds cannot always form under supersaturated water vapor conditions. This is especially true in the late summer, when aerosol concentrations are generally very low in the high Arctic. The environment changes rapidly around freeze-up as the open waters close and snow starts accumulating on ice. We investigated droplet formation during eight significant fog events in the central Arctic Ocean, north of 80 degrees, from August 12 to 19 September 2018 during the Arctic Ocean 2018 expedition onboard the icebreaker Oden. Calculated hygroscopicity parameters (kappa) for the entire study were very high (up to kappa = 0.85 +/- 0.13), notably after freeze-up, suggesting that atmospheric particles were very cloud condensation nuclei (CCN)-active. At least one of the events showed that surface clouds were able to form and persist for at least a couple hours at aerosol concentrations less than 10 cm-3, which was previously suggested to be the minimum for cloud formation. Among these events that were considered limited in CCN, effective radii were generally larger than in the high CCN cases. In some of the fog events, droplet residuals particles did not reactivate under supersaturations up to 0.95%, suggesting either in-droplet reactions decreased hygroscopicity, or an ambient supersaturation above 1%. These results provide insight into droplet formation during the clean late-summer and fall of the high Arctic with limited influence from continental sources. The Arctic atmosphere can be very clean in the summer, to the point that clouds cannot form because there are insufficient particles present for the water vapor to condense upon. This has important implications for the radiation budget, which is highly dependent on clouds. As part of the Arctic Ocean 2018 expedition in the central Arctic Ocean near the North Pole, we investigated the ability of particles to turn into droplets throughout the whole cruise (August 12 to 19 September 2018), and during eight significant fog events. Overall, we found that after the sea ice started to freeze, the particles were more capable of turning into cloud droplets. During one fog event, we observed fog droplets forming when the particle concentrations were lower than the limit that past studies had suggested that fog/cloud could be sustained. During several fog events, the dried fog droplets did not always re-form droplets when exposed to cloud-like conditions, which suggests that the original droplets must have formed under extreme conditions. Our results show that in the summer/fall in the high Arctic, liquid droplets sometimes form under unusual circumstances that are likely not always considered in models. Aerosol hygroscopicity was greater after surface water freeze-up than beforeHygroscopicity of Aitken mode particles was generally greater than accumulation mode particlesCloud droplet effective radii during aerosol-limited periods were larger generally than periods with higher aerosol concentrations

Keywords
Arctic aerosols, aerosol-cloud interactions, fog, cloud condensation nuclei, Groundbased counterflow virtual impactor, aerosol hygroscopicity
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-225976 (URN)10.1029/2023JD039159 (DOI)001142005700001 ()2-s2.0-85182464862 (Scopus ID)
Available from: 2024-01-31 Created: 2024-01-31 Last updated: 2024-01-31Bibliographically approved
Bulatovic, I., Savre, J., Tjernström, M., Leck, C. & Ekman, A. M. L. (2023). Large-eddy simulation of a two-layer boundary-layer cloud system from the Arctic Ocean 2018 expedition. Atmospheric Chemistry And Physics, 23(12), 7033-7055
Open this publication in new window or tab >>Large-eddy simulation of a two-layer boundary-layer cloud system from the Arctic Ocean 2018 expedition
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2023 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 23, no 12, p. 7033-7055Article in journal (Refereed) Published
Abstract [en]

Climate change is particularly noticeable in the Arctic. The most common type of cloud at these latitudes is mixed-phase stratocumulus. These clouds occur frequently and persistently during all seasons and play a critical role in the Arctic energy budget. Previous observations in the central (north of 80 N) Arctic have shown a high occurrence of prolonged periods of a shallow, single-layer mixed-phase stratocumulus at the top of the boundary layer (BL; altitudes ∼ 300 to 400 m). However, recent observations from the summer of 2018 instead showed a prevalence of a two-layer boundary-layer cloud system. Here we use large-eddy simulation to examine the maintenance of one of the cloud systems observed in the summer of 2018 and the sensitivity of the cloud layers to different micro- and macro-scale parameters. We find that the model generally reproduces the observed thermodynamic structure well, with two near-neutrally stratified layers in the BL caused by a low cloud (located within the first few hundred meters) capped by a lower-altitude temperature inversion and an upper cloud layer (based around one kilometer or slightly higher) capped by the main temperature inversion of the BL. The simulated cloud structure is persistent unless there are low aerosol number concentrations (≤ 5 cm−3), which cause the upper cloud layer to dissipate, or high large-scale wind speeds (≥ 8.5 m s−1), which erode the lower inversion and the related cloud layer. The changes in cloud structure alter both the short- and longwave cloud radiative effect at the surface. This results in changes in the net radiative effect of the modeled cloud system, which can impact the surface melting or freezing. The findings highlight the importance of better understanding and representing aerosol sources and sinks over the central Arctic Ocean. Furthermore, they underline the significance of meteorological parameters, such as the large-scale wind speed, for maintaining the two-layer boundary-layer cloud structure encountered in the lower atmosphere of the central Arctic.

National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-220984 (URN)10.5194/acp-23-7033-2023 (DOI)001020186800001 ()2-s2.0-85164341735 (Scopus ID)
Available from: 2023-09-13 Created: 2023-09-13 Last updated: 2023-09-13Bibliographically approved
Porter, G. C. E., Adams, M. P., Brooks, I. M., Ickes, L., Karlsson, L., Leck, C., . . . Murray, B. J. (2022). Highly Active Ice-Nucleating Particles at the Summer North Pole. Journal of Geophysical Research - Atmospheres, 127(6), Article ID e2021JD036059.
Open this publication in new window or tab >>Highly Active Ice-Nucleating Particles at the Summer North Pole
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2022 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 127, no 6, article id e2021JD036059Article in journal (Refereed) Published
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.

Keywords
Arctic, ice-nucleating particles, ice, mixed-phase clouds
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-204007 (URN)10.1029/2021JD036059 (DOI)000776467500024 ()2-s2.0-85127305449 (Scopus ID)
Available from: 2022-04-20 Created: 2022-04-20 Last updated: 2022-04-20Bibliographically approved
Karlsson, L., Baccarini, A., Duplessis, P., Baumgardner, D., Brooks, I. M., Chang, R.-W. Y. W., . . . Zieger, P. (2022). Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition. Journal of Geophysical Research - Atmospheres, 127(11), Article ID e2021JD036383.
Open this publication in new window or tab >>Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition
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2022 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 127, no 11, article id e2021JD036383Article in journal (Refereed) Published
Abstract [en]

Detailed knowledge of the physical and chemical properties and sources of particles that form clouds is especially important in pristine areas like the Arctic, where particle concentrations are often low and observations are sparse. Here, we present in situ cloud and aerosol measurements from the central Arctic Ocean in August–September 2018 combined with air parcel source analysis. We provide direct experimental evidence that Aitken mode particles (particles with diameters ≲70 nm) significantly contribute to cloud condensation nuclei (CCN) or cloud droplet residuals, especially after the freeze-up of the sea ice in the transition toward fall. These Aitken mode particles were associated with air that spent more time over the pack ice, while size distributions dominated by accumulation mode particles (particles with diameters ≳70 nm) showed a stronger contribution of oceanic air and slightly different source regions. This was accompanied by changes in the average chemical composition of the accumulation mode aerosol with an increased relative contribution of organic material toward fall. Addition of aerosol mass due to aqueous-phase chemistry during in-cloud processing was probably small over the pack ice given the fact that we observed very similar particle size distributions in both the whole-air and cloud droplet residual data. These aerosol–cloud interaction observations provide valuable insight into the origin and physical and chemical properties of CCN over the pristine central Arctic Ocean.

National Category
Meteorology and Atmospheric Sciences Environmental Sciences
Identifiers
urn:nbn:se:su:diva-204135 (URN)10.1029/2021JD036383 (DOI)000806579000001 ()
Available from: 2022-04-26 Created: 2022-04-26 Last updated: 2022-06-30Bibliographically approved
Siegel, K., Karlsson, L., Zieger, P., Baccarini, A., Schmale, J., Lawler, M., . . . Mohr, C. (2021). Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS. Environmental Science: Atmospheres, 1(4), 161-175
Open this publication in new window or tab >>Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS
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2021 (English)In: Environmental Science: Atmospheres, E-ISSN 2634-3606, Vol. 1, no 4, p. 161-175Article in journal (Refereed) Published
Abstract [en]

The remote central Arctic during summertime has a pristine atmosphere with very low aerosol particle concentrations. As the region becomes increasingly ice-free during summer, enhanced ocean-atmosphere fluxes of aerosol particles and precursor gases may therefore have impacts on the climate. However, large knowledge gaps remain regarding the sources and physicochemical properties of aerosols in this region. Here, we present insights into the molecular composition of semi-volatile aerosol components collected in September 2018 during the MOCCHA (Microbiology-Ocean-Cloud-Coupling in the High Arctic) campaign as part of the Arctic Ocean 2018 expedition with the Swedish Icebreaker Oden. Analysis was performed offline in the laboratory using an iodide High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). Our analysis revealed significant signal from organic and sulfur-containing compounds, indicative of marine aerosol sources, with a wide range of carbon numbers and O : C ratios. Several of the sulfur-containing compounds are oxidation products of dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae. Comparison of the time series of particulate and gas-phase DMS oxidation products did not reveal a significant correlation, indicative of the different lifetimes of precursor and oxidation products in the different phases. This is the first time the FIGAERO-HRToF-CIMS was used to investigate the composition of aerosols in the central Arctic. The detailed information on the molecular composition of Arctic aerosols presented here can be used for the assessment of aerosol solubility and volatility, which is relevant for understanding aerosol-cloud interactions.

Keywords
aerosol, chemical composition, mass spectrometry, dimethyl sulfide, oxidation, Arctic
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-184289 (URN)10.1039/D0EA00023J (DOI)000870704200001 ()2-s2.0-85121774671 (Scopus ID)
Funder
Swedish Research Council, 2016-03518, 2018-04255, 2016-05100Swedish Research Council Formas, 2015-00748, 2017-00567Knut and Alice Wallenberg Foundation, 2016.0024, 2017.0165EU, Horizon Europe, 821205, 867599
Available from: 2020-08-24 Created: 2020-08-24 Last updated: 2023-02-10Bibliographically approved
Orellana, M. V., Hansell, D. A., Matrai, P. A. & Leck, C. (2021). Marine Polymer-Gels' Relevance in the Atmosphere as Aerosols and CCN. Gels, 7(4), Article ID 185.
Open this publication in new window or tab >>Marine Polymer-Gels' Relevance in the Atmosphere as Aerosols and CCN
2021 (English)In: Gels, E-ISSN 2310-2861, Vol. 7, no 4, article id 185Article in journal (Refereed) Published
Abstract [en]

Marine polymer gels play a critical role in regulating ocean basin scale biogeochemical dynamics. This brief review introduces the crucial role of marine gels as a source of aerosol particles and cloud condensation nuclei (CCN) in cloud formation processes, emphasizing Arctic marine microgels. We review the gel's composition and relation to aerosols, their emergent properties, and physico-chemical processes that explain their change in size spectra, specifically in relation to aerosols and CCN. Understanding organic aerosols and CCN in this context provides clear benefits to quantifying the role of marine nanogel/microgel in microphysical processes leading to cloud formation. This review emphasizes the DOC-marine gel/aerosolized gel-cloud link, critical to developing accurate climate models.

Keywords
marine gels, DOC, aerosols, CCN, SML, central Arctic Ocean
National Category
Chemical Sciences
Identifiers
urn:nbn:se:su:diva-201374 (URN)10.3390/gels7040185 (DOI)000742740700001 ()34842644 (PubMedID)
Available from: 2022-01-24 Created: 2022-01-24 Last updated: 2022-02-25Bibliographically approved
Lawler, M. J., Saltzman, E. S., Karlsson, L., Zieger, P., Salter, M. E., Baccarini, A., . . . Leck, C. (2021). New Insights Into the Composition and Origins of Ultrafine Aerosol in the Summertime High Arctic. Geophysical Research Letters, 48(21), Article ID e2021GL094395.
Open this publication in new window or tab >>New Insights Into the Composition and Origins of Ultrafine Aerosol in the Summertime High Arctic
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2021 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 48, no 21, article id e2021GL094395Article in journal (Refereed) Published
Abstract [en]

The summertime high Arctic atmosphere is characterized by extremely low aerosol abundance, such that small natural aerosol inputs have a strong influence on cloud formation and surface temperature. The physical sources and the mechanisms responsible for aerosol formation and development in this climate-critical and changing region are still uncertain. We report time-resolved measurements of high Arctic Aitken mode (∼20–60 nm diameter) aerosol composition during August–September 2018. During a significant Aitken mode formation event, the particles were composed of a combination of primary and secondary materials. These results highlight the importance of primary aerosol sources for high Arctic cloud formation, and they imply the action of a poorly understood atmospheric mechanism separating larger particles into multiple sub-particles.

Keywords
ultrafine aerosol, Arctic, marine boundary layer, aerosol composition, nanoparticle, aerosol formation
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-200696 (URN)10.1029/2021GL094395 (DOI)000716768700040 ()
Available from: 2022-01-13 Created: 2022-01-13 Last updated: 2022-04-26Bibliographically approved
Zinke, J., Salter, M. E., Leck, C., Lawler, M. J., Porter, G. C. E., Adams, M. P., . . . Zieger, P. (2021). The development of a miniaturised balloon-borne cloud water sampler and its first deployment in the high Arctic. Tellus. Series B, Chemical and physical meteorology, 73(1), 1-12, Article ID 1915614.
Open this publication in new window or tab >>The development of a miniaturised balloon-borne cloud water sampler and its first deployment in the high Arctic
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2021 (English)In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 73, no 1, p. 1-12, article id 1915614Article in journal (Refereed) Published
Abstract [en]

The chemical composition of cloud water can be used to infer the sources of particles upon which cloud droplets and ice crystals have formed. In order to obtain cloud water for analysis of chemical composition for elevated clouds in the pristine high Arctic, balloon-borne active cloud water sampling systems are the optimal approach. However, such systems have not been feasible to deploy previously due to their weight and the challenging environmental conditions. We have taken advantage of recent developments in battery technology to develop a miniaturised cloud water sampler for balloon-borne collection of cloud water. Our sampler is a bulk sampler with a cloud drop cutoff diameter of approximately 8 mu m and an estimated collection efficiency of 70%. The sampler was heated to prevent excessive ice accumulation and was able to operate for several hours under the extreme conditions encountered in the high Arctic. We have tested and deployed the new sampler on a tethered balloon during the Microbiology-Ocean-Cloud-Coupling in the High Arctic (MOCCHA) campaign in August and September 2018 close to the North pole. The sampler was able to successfully retrieve cloud water samples that were analysed to determine their chemical composition as well as their ice-nucleating activity. Given the pristine conditions found in the high Arctic we have placed significant emphasis on the development of a suitable cleaning procedure to minimise background contamination by the sampler itself.

Keywords
instrument development, balloon-borne sampling, cloud water composition, Arctic, clouds, cloud water sampling
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-193994 (URN)10.1080/16000889.2021.1915614 (DOI)000649431100001 ()
Available from: 2021-06-09 Created: 2021-06-09 Last updated: 2022-02-25Bibliographically approved
Bulatovic, I., Igel, A. L., Leck, C., Heintzenberg, J., Riipinen, I. & Ekman, A. M. L. (2021). The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic - a simulation study supported by observational data. Atmospheric Chemistry And Physics, 21(5), 3871-3897
Open this publication in new window or tab >>The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic - a simulation study supported by observational data
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2021 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 21, no 5, p. 3871-3897Article in journal (Refereed) Published
Abstract [en]

The potential importance of Aitken mode particles (diameters similar to 25-80 nm) for stratiform mixed-phase clouds in the summertime high Arctic (> 80 degrees N) has been investigated using two large-eddy simulation models. We find that, in both models, Aitken mode particles significantly affect the simulated microphysical and radiative properties of the cloud and can help sustain the cloud when accumulation mode concentrations are low (< 10-20 cm(-3)), even when the particles have low hygroscopicity (hygroscopicity parameter - kappa = 0.1). However, the influence of the Aitken mode decreases if the overall liquid water content of the cloud is low, either due to a higher ice fraction or due to low radiative cooling rates. An analysis of the simulated supersaturation (ss) statistics shows that the ss frequently reaches 0.5 % and sometimes even exceeds 1 %, which confirms that Aitken mode particles can be activated. The modelling results are in qualitative agreement with observations of the Hoppel minimum obtained from four different expeditions in the high Arctic. Our findings highlight the importance of better understanding Aitken mode particle formation, chemical properties and emissions, particularly in clean environments such as the high Arctic.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-192038 (URN)10.5194/acp-21-3871-2021 (DOI)000630173500004 ()
Available from: 2021-04-11 Created: 2021-04-11 Last updated: 2022-09-16Bibliographically approved
Christiansen, S., Ickes, L., Bulatovic, I., Leck, C., Murray, B. J., Bertram, A. K., . . . Bilde, M. (2020). Influence of Arctic Microlayers and Algal Cultures on Sea Spray Hygroscopicity and the Possible Implications for Mixed-Phase Clouds. Journal of Geophysical Research - Atmospheres, 125(19), Article ID e2020JD032808.
Open this publication in new window or tab >>Influence of Arctic Microlayers and Algal Cultures on Sea Spray Hygroscopicity and the Possible Implications for Mixed-Phase Clouds
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2020 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 125, no 19, article id e2020JD032808Article in journal (Refereed) Published
Abstract [en]

As Arctic sea ice cover diminishes, sea spray aerosols (SSA) have a larger potential to be emitted into the Arctic atmosphere. Emitted SSA can contain organic material, but how it affects the ability of particles to act as cloud condensation nuclei (CCN) is still not well understood. Here we measure the CCN-derived hygroscopicity of three different types of aerosol particles: (1) Sea salt aerosols made from artificial seawater, (2) aerosol generated from artificial seawater spiked with diatom species cultured in the laboratory, and (3) aerosols made from samples of sea surface microlayer (SML) collected during field campaigns in the North Atlantic and Arctic Ocean. Samples are aerosolized using a sea spray simulation tank (plunging jet) or an atomizer. We show that SSA containing diatom and microlayer exhibit similar CCN activity to inorganic sea salt with a kappa value of similar to 1.0. Large-eddy simulation (LES) is then used to evaluate the general role of aerosol hygroscopicity in governing mixed-phase low-level cloud properties in the high Arctic. For accumulation mode aerosol, the simulated mixed-phase cloud properties do not depend strongly on kappa, unless the values are lower than 0.4. For Aitken mode aerosol, the hygroscopicity is more important; the particles can sustain the cloud if the hygroscopicity is equal to or higher than 0.4, but not otherwise. The experimental and model results combined suggest that the internal mixing of biogenic organic components in SSA does not have a substantial impact on the cloud droplet activation process and the cloud lifetime in Arctic mixed-phase clouds.

Keywords
sea spray aerosol, CCN, sea surface microlayer, mixed-phase clouds, Arctic, hygroscopicity
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-188239 (URN)10.1029/2020JD032808 (DOI)000582482800009 ()
Available from: 2020-12-28 Created: 2020-12-28 Last updated: 2022-10-28Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6621-5261

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