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AGU: Global Biogeochemical Cycles

 

Keywords

  • atmospheric methane
  • ice cores
  • trace gas emissions

Index Terms

  • Atmospheric Composition and Structure: Geochemical cycles
  • Biogeosciences: Biogeochemical cycles, processes, and modeling
  • Biogeosciences: Biosphere/atmosphere interactions
  • Biogeosciences: Isotopic composition and chemistry
  • Biogeosciences: Paleoclimatology and paleoceanography

Abstract

GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 19, GB2002, 12 PP., 2005
doi:10.1029/2004GB002408

Records of the δ13C of atmospheric CH4 over the last 2 centuries as recorded in Antarctic snow and ice

Todd Sowers

Department of Geosciences and the Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania, USA

Sophie Bernard

Laboratoire de Glaciologie et Géophysique de l'Environnement, St. Martin d'Hères, France

Olivier Aballain

Laboratoire de Glaciologie et Géophysique de l'Environnement, St. Martin d'Hères, France

Jérôme Chappellaz

Laboratoire de Glaciologie et Géophysique de l'Environnement, St. Martin d'Hères, France

Jean-Marc Barnola

Laboratoire de Glaciologie et Géophysique de l'Environnement, St. Martin d'Hères, France

Thomas Marik

Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany

Methane is one of the important greenhouse gases accumulating in the atmosphere today. The increased loading over the past 2 centuries is thought to be the result of increased anthropogenic emissions. Here we present records of the δ13C of CH4 in firn air from the South Pole and in trapped bubbles in a short ice core from Siple Dome, Antarctica, that help constrain historical emissions of various sources throughout the last 2 centuries. Using two firn air samplings in 1995 and 2001 we calculate that δ13CH4 has increased by an average of 0.06 ± 0.02‰/yr over the 6 years between samplings. Our ice core results suggest the δ13C of atmospheric CH4 has increased by 1.8 ± 0.2‰ between 1820 A.D. and 2001 AD. The δ13CH4 changes in both data sets are the result of an increase in the relative proportion of CH4 sources with elevated 13C/12C isotope ratios. One explanation for observed trends involves a 16 Tg/yr increase in CH4 emissions associated with biomass burning over the past 2 centuries.

Received 9 November 2004; accepted 10 February 2005; published 2 April 2005.

Citation: Sowers, T., S. Bernard, O. Aballain, J. Chappellaz, J.-M. Barnola, and T. Marik (2005), Records of the δ13C of atmospheric CH4 over the last 2 centuries as recorded in Antarctic snow and ice, Global Biogeochem. Cycles, 19, GB2002, doi:10.1029/2004GB002408.

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