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Volume 19, issue 1
Atmos. Chem. Phys., 19, 57-76, 2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

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

Atmos. Chem. Phys., 19, 57-76, 2019
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 03 Jan 2019

Research article | 03 Jan 2019

Aircraft-based measurements of High Arctic springtime aerosol show evidence for vertically varying sources, transport and composition

Megan D. Willis1,a, Heiko Bozem2, Daniel Kunkel2, Alex K. Y. Lee3, Hannes Schulz4, Julia Burkart5, Amir A. Aliabadi6, Andreas B. Herber4, W. Richard Leaitch7, and Jonathan P. D. Abbatt1 Megan D. Willis et al.
  • 1Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
  • 2Institute for Atmospheric Physics, Johannes Gutenberg University of Mainz, Mainz, Germany
  • 3Department of Civil and Environmental Engineering, National University of Singapore, Singapore
  • 4Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany
  • 5Faculty of Physics, Aerosol Physics and Environmental Physics, University of Vienna, Vienna, Austria
  • 6School of Engineering, University of Guelph, Guelph, Ontario, Canada
  • 7Environment and Climate Change Canada, Toronto, Ontario, Canada
  • anow at: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA

Abstract. The sources, chemical transformations and removal mechanisms of aerosol transported to the Arctic are key factors that control Arctic aerosol–climate interactions. Our understanding of sources and processes is limited by a lack of vertically resolved observations in remote Arctic regions. We present vertically resolved observations of trace gases and aerosol composition in High Arctic springtime, made largely north of 80°N, during the NETCARE campaign. Trace gas gradients observed on these flights defined the polar dome as north of 66–68°30′N and below potential temperatures of 283.5–287.5K. In the polar dome, we observe evidence for vertically varying source regions and chemical processing. These vertical changes in sources and chemistry lead to systematic variation in aerosol composition as a function of potential temperature. We show evidence for sources of aerosol with higher organic aerosol (OA), ammonium and refractory black carbon (rBC) content in the upper polar dome. Based on FLEXPART-ECMWF calculations, air masses sampled at all levels inside the polar dome (i.e., potential temperature  < 280.5K, altitude  <  ∼ 3.5km) subsided during transport over transport times of at least 10 days. Air masses at the lowest potential temperatures, in the lower polar dome, had spent long periods ( > 10 days) in the Arctic, while air masses in the upper polar dome had entered the Arctic more recently. Variations in aerosol composition were closely related to transport history. In the lower polar dome, the measured sub-micron aerosol mass was dominated by sulfate (mean 74%), with lower contributions from rBC (1%), ammonium (4%) and OA (20%). At higher altitudes and higher potential temperatures, OA, ammonium and rBC contributed 42%, 8% and 2% of aerosol mass, respectively. A qualitative indication for the presence of sea salt showed that sodium chloride contributed to sub-micron aerosol in the lower polar dome, but was not detectable in the upper polar dome. Our observations highlight the differences in Arctic aerosol chemistry observed at surface-based sites and the aerosol transported throughout the depth of the Arctic troposphere in spring.

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Short summary
The vertical distribution of Arctic aerosol is an important driver of its climate impacts. We present vertically resolved measurements of aerosol composition and properties made in the High Arctic during spring on an aircraft platform. We explore how aerosol properties are related to transport history and show evidence of vertical trends in aerosol sources, transport mechanisms and composition. These results will help us to better understand aerosol–climate interactions in the Arctic.
The vertical distribution of Arctic aerosol is an important driver of its climate impacts. We...