Articles | Volume 17, issue 21
Atmos. Chem. Phys., 17, 13119–13138, 2017

Special issue: NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

Atmos. Chem. Phys., 17, 13119–13138, 2017

Research article 07 Nov 2017

Research article | 07 Nov 2017

Frequent ultrafine particle formation and growth in Canadian Arctic marine and coastal environments

Douglas B. Collins1, Julia Burkart1, Rachel Y.-W. Chang2, Martine Lizotte3, Aude Boivin-Rioux4, Marjolaine Blais4, Emma L. Mungall1, Matthew Boyer2, Victoria E. Irish5, Guillaume Massé3, Daniel Kunkel6, Jean-Éric Tremblay3, Tim Papakyriakou7, Allan K. Bertram5, Heiko Bozem6, Michel Gosselin4, Maurice Levasseur3, and Jonathan P. D. Abbatt1 Douglas B. Collins et al.
  • 1Department of Chemistry, University of Toronto, Toronto, ON, M5S 3H6, Canada
  • 2Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 4R2, Canada
  • 3Département de Biologie (Québec-Océan), Université Laval, Québec City, QC, G1V 0A6, Canada
  • 4Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, Rimouski, QC, G5L 3A1, Canada
  • 5Department of Chemistry, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada
  • 6Johannes Gutenberg University of Mainz, Institute of Atmospheric Physics, 55099 Mainz, Germany
  • 7Center for Earth Observation Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada

Abstract. The source strength and capability of aerosol particles in the Arctic to act as cloud condensation nuclei have important implications for understanding the indirect aerosol–cloud effect within the polar climate system. It has been shown in several Arctic regions that ultrafine particle (UFP) formation and growth is a key contributor to aerosol number concentrations during the summer. This study uses aerosol number size distribution measurements from shipboard expeditions aboard the research icebreaker CCGS Amundsen in the summers of 2014 and 2016 throughout the Canadian Arctic to gain a deeper understanding of the drivers of UFP formation and growth within this marine boundary layer. UFP number concentrations (diameter > 4 nm) in the range of 101–104 cm−3 were observed during the two seasons, with concentrations greater than 103 cm−3 occurring more frequently in 2016. Higher concentrations in 2016 were associated with UFP formation and growth, with events occurring on 41 % of days, while events were only observed on 6 % of days in 2014. Assessment of relevant parameters for aerosol nucleation showed that the median condensation sink in this region was approximately 1.2 h−1 in 2016 and 2.2 h−1 in 2014, which lie at the lower end of ranges observed at even the most remote stations reported in the literature. Apparent growth rates of all observed events in both expeditions averaged 4.3 ± 4.1 nm h−1, in general agreement with other recent studies at similar latitudes. Higher solar radiation, lower cloud fractions, and lower sea ice concentrations combined with differences in the developmental stage and activity of marine microbial communities within the Canadian Arctic were documented and help explain differences between the aerosol measurements made during the 2014 and 2016 expeditions. These findings help to motivate further studies of biosphere–atmosphere interactions within the Arctic marine environment to explain the production of UFP and their growth to sizes relevant for cloud droplet activation.

Short summary
The sources of aerosol particles and their growth to sizes large enough to act as cloud droplet seeds is of major importance to climate since clouds exert substantial control over the atmospheric energy balance. Using ship-board measurements from two summers in the Canadian Arctic, aerosol formation events were related to co-sampled atmospheric and oceanic parameters, providing insight into factors that drive particle formation and motivating further study of ocean–atmosphere interactions.
Final-revised paper