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Volume 12, issue 22
Atmos. Chem. Phys., 12, 10833-10839, 2012
https://doi.org/10.5194/acp-12-10833-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Radical chemistry over sunlit snow: interactions between HOx...

Atmos. Chem. Phys., 12, 10833-10839, 2012
https://doi.org/10.5194/acp-12-10833-2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 16 Nov 2012

Research article | 16 Nov 2012

Overview of the 2007 and 2008 campaigns conducted as part of the Greenland Summit Halogen-HOx Experiment (GSHOX)

J. L. Thomas1,2, J. E. Dibb3, J. Stutz1, R. von Glasow4, S. Brooks5, L. G. Huey6, and B. Lefer7 J. L. Thomas et al.
  • 1Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA
  • 2UPMC Univ. Paris 06, UMR8190, CNRS/INSU – Univ. Versailles St.-Quentin, LATMOS-IPSL, Paris, France
  • 3Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA
  • 4School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
  • 5NOAA ATDD, 456 S. Illinois Ave, P.O. Box 2456, Oak Ridge, TN 38731, USA
  • 6School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30033, USA
  • 7Department of Geosciences, University of Houston, TX 77204, USA

Abstract. From 10 May through 17 June 2007 and 6 June through 9 July 2008 intensive sampling campaigns at Summit, Greenland confirmed that active bromine chemistry is occurring in and above the snow pack at the highest part of the Greenland ice sheet (72°36´ N, 38°25´ W and 3.2 km above sea level). Direct measurements found BrO and soluble gas phase Br mixing ratios in the low pptv range on many days (maxima < 10 pptv). Conversion of up to 200 pg m−3 of gaseous elemental mercury (GEM) to reactive gaseous mercury (RGM) and enhanced OH relative to HO2 plus RO2 confirm that active bromine chemistry is impacting chemical cycles even at such low abundances of reactive bromine species. However, it does not appear that Bry chemistry can fully account for observed perturbations to HOx partitioning, suggesting unknown additional chemical processes may be important in this unique environment, or that our understanding of coupled NOx-HOx-Bry chemistry above sunlit polar snow is incomplete. Rapid transport from the north Atlantic marine boundary layer occasionally caused enhanced BrO at Summit (just two such events observed during the 12 weeks of sampling over the two seasons). In general observed reactive bromine was linked to activation of bromide (Br) in, and release of reactive bromine from, the snowpack. A coupled snow-atmosphere model simulated observed NO and BrO at Summit during a three day interval when winds were weak. The source of Br in surface and near surface snow at Summit is not entirely clear, but concentrations were observed to increase when stronger vertical mixing brought free tropospheric air to the surface. Reactive Bry mixing ratios above the snow often increased in the day or two following increases in snow concentration, but this response was not consistent. On seasonal time scales concentrations of Br in snow and reactive bromine in the air were directly related.

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