1Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA
2Department of Earth and Environmental Sciences, University of Rochester, Rochester, USA
3UJF-Grenoble/CNRS, Laboratory for Glaciology and Geophysics of the Environment, Grenoble, France
4UJF-Grenoble/CNRS, Grenoble Image Parole Signal Automatique, St. Martin d'Hères, France
5Institute for Marine and Atmospheric Research Utrecht, Utrecht University, the Netherlands
6School of Environmental Sciences, University of East Anglia, Norwich, UK
7Max Planck Institute for Chemistry, Mainz, Germany
8Niels Bohr Institute, University of Copenhagen, Denmark
9Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Aspendale, Australia
10Global Monitoring Division, Earth Systems Research Laboratory, NOAA, Boulder, USA
Received: 01 Apr 2013 – Published in Atmos. Chem. Phys. Discuss.: 15 May 2013
Abstract. The short-chain non-methane hydrocarbons (NMHC) are mostly emitted into the atmosphere by anthropogenic processes. Recent studies have pointed out a tight linkage between the atmospheric mole fractions of the NMHC ethane and the atmospheric growth rate of methane. Consequently, atmospheric NMHC are valuable indicators for tracking changes in anthropogenic emissions, photochemical ozone production, and greenhouse gases. This study investigates the 1950–2010 Northern Hemisphere atmospheric C2–C5 NMHC ethane, propane, i-butane, n-butane, i-pentane, and n-pentane by (a) reconstructing atmospheric mole fractions of these trace gases using firn air extracted from three boreholes in 2008 and 2009 at the North Greenland Eemian Ice Drilling (NEEM) site and applying state-of-the-art models of trace gas transport in firn, and by (b) considering eight years of ambient NMHC monitoring data from five Arctic sites within the NOAA Global Monitoring Division (GMD) Cooperative Air Sampling Network. Results indicate that these NMHC increased by ~40–120% after 1950, peaked around 1980 (with the exception of ethane, which peaked approximately 10 yr earlier), and have since dramatically decreased to be now back close to 1950 levels. The earlier peak time of ethane vs. the C3–C5 NMHC suggests that different processes and emissions mitigation measures contributed to the decline in these NMHC. The 60 yr record also illustrates notable increases in the ratios of the isomeric iso-/n-butane and iso-/n-pentane ratios. Comparison of the reconstructed NMHC histories with 1950–2000 volatile organic compounds (VOC) emissions data and with other recently published ethane trend analyses from ambient air Pacific transect data showed (a) better agreement with North America and Western Europe emissions than with total Northern Hemisphere emissions data, and (b) better agreement with other Greenland firn air data NMHC history reconstructions than with the Pacific region trends. These analyses emphasize that for NMHC, having atmospheric lifetimes on the order of < 2 months, the Greenland firn air records are primarily a representation of Western Europe and North America emission histories.
Revised: 26 Nov 2013 – Accepted: 09 Dec 2013 – Published: 10 Feb 2014
Helmig, D., Petrenko, V., Martinerie, P., Witrant, E., Röckmann, T., Zuiderweg, A., Holzinger, R., Hueber, J., Thompson, C., White, J. W. C., Sturges, W., Baker, A., Blunier, T., Etheridge, D., Rubino, M., and Tans, P.: Reconstruction of Northern Hemisphere 1950–2010 atmospheric non-methane hydrocarbons, Atmos. Chem. Phys., 14, 1463-1483, doi:10.5194/acp-14-1463-2014, 2014.