EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Modelling the seasonal cycle of atmospheric δ13C-CH4 using source specific δ13C-CH4 values

Vilma Kangasaho1, Aki Tsuruta1, Tuula Aalto1, Leif Backman1, Sander Houweling2,3, Maarten Krol2,4,5, Wouter Peters4,6, Ingrid Luijkx4, Sebastian Lienert7, Fortunat Joos7, Edward Dlugokencky8, Sylvia Michael9, James White9, and Rebecca Fisher10
Vilma Kangasaho et al.
  • 1Finnish Meteorological Institute, Finland
  • 2SRON Netherlands Institute for Space Research, the Netherlands
  • 3Vrije Universiteit Amsterdam, Netherlands
  • 4Wageningen University &, Research, Meteorology and Air Quality, the Netherlands
  • 5IMAU, Utrecht University, the Netherlands
  • 6University of Groningen, Centre for Isotope Research, the Netherlands
  • 7University of Bern, Climate and Environmental Physics, Switzerland
  • 9INSTAAR, University of Colorado, USA
  • 10Royal Holloway, University of London, UK

The atmospheric burden of methane (CH4) has more than doubled since the 18th Century. Currently the abundance of CH4 in the atmosphere is well known, but emission rates from different source sectors are uncertain. CH4 is emitted to the atmosphere from various sources. To better understand the changes in atmospheric CH4 abundance before and after 2006, it is important to study the contribution from these different sources separately. Most CH4 source have process specific δ13C-CH4 values, which can be used to broadly identify source sectors.

This study examines the seasonal cycle of atmospheric δ13C-CH4 in recent decades using the TM5 atmospheric transport. TM5 is driven by ECMWF ERA-Interim meteorological fields, and uses pre-calculated OH-fields and reaction rates with Cl and O(1D) to account for the CH4 sink processes in the atmosphere. TM5 is run at a 1ox1o resolution over Europe and globally at 6ox4o. Emissions for enteric fermentation and manure management, landfills and waste water treatment, rice cultivation, coal industry, oil and gas industry, and residential are taken from the EDGAR inventory. Natural emission for wetlands, peatlands and mineral soils, and soil sinks are taken from the LPX-Bern DYPTOP ecosystem model. Emissions for geological seeps including onshore hydrocarbon macro-seeps (including mud volcanoes), submarine (offshore) seeps, diffuse microseepage and geothermal manifestations are included. Emissions for fires (GFED v4), termites, wild animals and from the ocean are also included. Several sensitivity analyses are carried out. The sensitivity analyses include simulations with and without seasonal cycles in the anthropogenic emission fields (EDGAR v4.2 FT2010 vs EDGAR v4.3.2), and with and without spatial variations in source specific  δ13C-CH4 values, which are used to calculate 13CH4/CH4 emission ratios. The effect of including the seasonal cycle in the anthropogenic emissions were not significant, which means natural sources probably play more important role in determining the seasonal cycle of δ13C-CH4. The global observations of atmospheric CH4 and δ13C-CH4, provided by NOAA’s GMD, the INSTAAR and Royal Holloway, the University of London, are used for evaluation. We present the importance of having reasonable initial fields of atmospheric 13CH4, which will be later used as inputs for CarbonTracker Europe-δ13CH4 (CTE-δ13CH4) data assimilation system to optimise CH4 emissions by source category.

How to cite: Kangasaho, V., Tsuruta, A., Aalto, T., Backman, L., Houweling, S., Krol, M., Peters, W., Luijkx, I., Lienert, S., Joos, F., Dlugokencky, E., Michael, S., White, J., and Fisher, R.: Modelling the seasonal cycle of atmospheric δ13C-CH4 using source specific δ13C-CH4 values, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13274,, 2020.


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