An Arctic climatology of particle number size distributions and cloud condensation nuclei during warm and moist intrusions
Abstract
Recent studies indicate that warm and moist intrusions are significant sources of aerosols in the Arctic. Yet their contribution to different aerosol particle size modes, cloud condensation nuclei (CCN), and droplet number concentrations (N d ) remains largely unconstrained. Here, we use long-term aerosol observations from five Arctic observatories and show that intrusions are a major driver of CCN perturbations, particularly in summer, significantly increasing accumulation mode particle, CCN and N d number concentrations at all sites. In winter and spring, intrusions decrease concentrations at sites near 0°longitude (Zeppelin, Villum, Alert) but increase them at sites near 180°(Tiksi, Utqiaġvik/Barrow). These contrasting patterns reflect the interplay between emission sources and wet scavenging along air mass trajectories. Our findings highlight that intrusions have a strong impact on Arctic aerosol and cloud properties and are a key component of the Arctic climate system.
Climate change in the Arctic is more pronounced than in other regions, manifesting itself through increases in surface temperatures three to four times that of the global average, a phenomenon referred to as Arctic Amplification (AA) 1 . Studies show that AA is driven by mechanisms including sea ice and water vapor feedback, as well as feedbacks involving aerosols and clouds, which are among the most uncertain factors in the AA and radiative forcing estimates 2-5 .
Increased heat and moisture transport to the Arctic from lower latitudes, primarily occurring through warm and moist air intrusions (also referred to as intrusions throughout the study) 6-9 , has been shown to potentially contribute to AA. These episodic events occur in all seasons 10 , originate from various longitudes, and are mainly driven by Rossby wave breaking and the subsequent development of atmospheric blocking or extratropical cyclones 11-14 . They account for more than 65% of the total moisture flux into the region 11,15 . This influx of heat and moisture triggers a cascade of impacts across the Arctic, including increased low-level mixedphase clouds (MPCs), changes in cloud microphysical properties, enhanced downward long-wave radiation, and a sea ice cover response to an anomalous positive surface energy balance 7,8,16-19 . Improving our understanding of these processes is essential for better constraining AA estimates.
Warm and moist intrusions drive long-range transport of not only heat and water vapor but also of aerosols, which can significantly influence the local and regional climate by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INPs), thereby affecting Arctic cloud properties 18,20-26 . A recent study documented a sharp rise in aerosol particle number concentrations during a springtime intrusion event, linked to aerosol transport from western Siberia and observed during the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic 25 . During this event, accumulation mode number concentrations increased to levels comparable to those found in European cities, with median values exceeding five times the yearlong median observed during the expedition. This aerosol enhancement was accompanied by increased CCN concentrations and notable changes in aerosol chemical composition and hygroscopicity. Another study 27 , focusing on the MOSAiC expedition winter/spring period, identified 15 intrusions, of which more than half were associated with elevated concentrations of climate-relevant pollutants, including black carbon, sulfur dioxide, and CCN-sized particles 27 . These polluted intrusions consistently originated from industrial regions of northern Siberia. Conversely, clean intrusions showed no increase in surface pollution, likely due to en-route scavenging, vertical decoupling, or marine-dominated air masses. Some clean intrusions transported biologically derived INPs from oceanic or marginal ice zone regions, highlighting the diverse aerosol populations associated with intrusions. Overall, the MOSAiC observations indicate that winter and spring intrusions can episodically deliver CCN and INPs in the central Arctic, underscoring their importance as regulators of aerosol populations.
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BibTeX
@article{donmez2026arctic,
title = {{An Arctic climatology of particle number size distributions and cloud condensation nuclei during warm and moist intrusions}},
author = {Berkay Dönmez and Jakob Boyd Pernov and Romanos Foskinis and Radiance Calmer and Paraskevi Georgakaki and Hélène Angot and Eija Asmi and John Backman and Tak Chan and Radovan Krejci and Peter Tunved and Andreas Massling and Henrik Skov and Alfred Wiedensohler and Athanasios Nenes and Julia Schmale},
journal = {npj climate and atmospheric science},
year = {2026},
month = sep,
doi = {10.1038/s41612-026-01461-1},
url = {https://hal.science/hal-05768583v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - An Arctic climatology of particle number size distributions and cloud condensation nuclei during warm and moist intrusions
AU - Berkay Dönmez
AU - Jakob Boyd Pernov
AU - Romanos Foskinis
AU - Radiance Calmer
AU - Paraskevi Georgakaki
AU - Hélène Angot
AU - Eija Asmi
AU - John Backman
AU - Tak Chan
AU - Radovan Krejci
AU - Peter Tunved
AU - Andreas Massling
AU - Henrik Skov
AU - Alfred Wiedensohler
AU - Athanasios Nenes
AU - Julia Schmale
PY - 2026
DA - 2026/09/29
JO - npj climate and atmospheric science
DO - 10.1038/s41612-026-01461-1
UR - https://hal.science/hal-05768583v1
AB - Recent studies indicate that warm and moist intrusions are significant sources of aerosols in the Arctic. Yet their contribution to different aerosol particle size modes, cloud condensation nuclei (CCN), and droplet number concentrations (N d ) remains largely unconstrained. Here, we use long-term aerosol observations from five Arctic observatories and show that intrusions are a major driver of CCN perturbations, particularly in summer, significantly increasing accumulation mode particle, CCN and N d number concentrations at all sites. In winter and spring, intrusions decrease concentrations at sites near 0°longitude (Zeppelin, Villum, Alert) but increase them at sites near 180°(Tiksi, Utqiaġvik/Barrow). These contrasting patterns reflect the interplay between emission sources and wet scavenging along air mass trajectories. Our findings highlight that intrusions have a strong impact on Arctic aerosol and cloud properties and are a key component of the Arctic climate system. Climate change in the Arctic is more pronounced than in other regions, manifesting itself through increases in surface temperatures three to four times that of the global average, a phenomenon referred to as Arctic Amplification (AA) 1 . Studies show that AA is driven by mechanisms including sea ice and water vapor feedback, as well as feedbacks involving aerosols and clouds, which are among the most uncertain factors in the AA and radiative forcing estimates 2-5 . Increased heat and moisture transport to the Arctic from lower latitudes, primarily occurring through warm and moist air intrusions (also referred to as intrusions throughout the study) 6-9 , has been shown to potentially contribute to AA. These episodic events occur in all seasons 10 , originate from various longitudes, and are mainly driven by Rossby wave breaking and the subsequent development of atmospheric blocking or extratropical cyclones 11-14 . They account for more than 65% of the total moisture flux into the region 11,15 . This influx of heat and moisture triggers a cascade of impacts across the Arctic, including increased low-level mixedphase clouds (MPCs), changes in cloud microphysical properties, enhanced downward long-wave radiation, and a sea ice cover response to an anomalous positive surface energy balance 7,8,16-19 . Improving our understanding of these processes is essential for better constraining AA estimates. Warm and moist intrusions drive long-range transport of not only heat and water vapor but also of aerosols, which can significantly influence the local and regional climate by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INPs), thereby affecting Arctic cloud properties 18,20-26 . A recent study documented a sharp rise in aerosol particle number concentrations during a springtime intrusion event, linked to aerosol transport from western Siberia and observed during the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic 25 . During this event, accumulation mode number concentrations increased to levels comparable to those found in European cities, with median values exceeding five times the yearlong median observed during the expedition. This aerosol enhancement was accompanied by increased CCN concentrations and notable changes in aerosol chemical composition and hygroscopicity. Another study 27 , focusing on the MOSAiC expedition winter/spring period, identified 15 intrusions, of which more than half were associated with elevated concentrations of climate-relevant pollutants, including black carbon, sulfur dioxide, and CCN-sized particles 27 . These polluted intrusions consistently originated from industrial regions of northern Siberia. Conversely, clean intrusions showed no increase in surface pollution, likely due to en-route scavenging, vertical decoupling, or marine-dominated air masses. Some clean intrusions transported biologically derived INPs from oceanic or marginal ice zone regions, highlighting the diverse aerosol populations associated with intrusions. Overall, the MOSAiC observations indicate that winter and spring intrusions can episodically deliver CCN and INPs in the central Arctic, underscoring their importance as regulators of aerosol populations.
SN - 2397-3722
ER -