Preprints
https://doi.org/10.5194/egusphere-2022-1257
https://doi.org/10.5194/egusphere-2022-1257
 
11 Jan 2023
11 Jan 2023
Status: this preprint is open for discussion.

Estimating Methane Emissions in the Arctic nations using surface observations from 2008 to 2019

Sophie Wittig1, Antoine Berchet1, Isabelle Pison1, Marielle Saunois1, Joël Thanwerdas1, Adrien Martinez1, Jean-Daniel Paris1, Tochinobu Machida2, Motoki Sasakawa2, Douglas E. J. Worthy3, Xin Lan4,5, Rona L. Thompson6, Espen Sollum6, and Michael Arshinov7 Sophie Wittig et al.
  • 1Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
  • 2Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan
  • 3Environment and Climate Change Canada, Climate Research Division, Toronto, Ontario, Canada
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, CO, USA
  • 5NOAA Global Monitoring Laboratory, Boulder, CO, USA
  • 6Norsk Institutt for Luftforskning, NILU, Kjeller, Norway
  • 7Independent researcher

Abstract. The Arctic is a critical region in terms of global warming. Environmental changes are already progressing steadily in high northern latitudes whereby, among other effects, a high potential of enhanced methane (CH4) emissions is induced. With CH4 being a potent greenhouse gas, additional emissions from Arctic regions may intensify global warming in the future by positive feedback. Various natural and anthropogenic sources are currently contributing to the Arctic’s CH4 budget; however the quantification of those emissions remains challenging. Assessing the amount of CH4 emissions in the Arctic and their contribution to the global budget still remains challenging. This is on the one hand due to the difficulties in carrying out accurate measurements in such remote areas. Besides, high variations in the spatial distribution of methane sources and a poor understanding of the effects of ongoing changes in carbon decomposition, vegetation and hydrology also complicate the assessment. Therefore, the aim of this work is to reduce uncertainties on current bottom-up estimates of CH4 emissions as well as soil oxidation by implementing an inverse modeling approach in order to better quantify CH4 sources and sinks for the most recent years (2008 to 2019). More precisely, the objective is to detect occurring trends in the CH4 emissions and potential changes in seasonal emission patterns. The implementation of the inversion included footprint simulations obtained with the atmospheric transport model FLEXPART, various emission estimates from inventories and land surface models as well as data of atmospheric CH4 concentrations from 42 surface observation sites in the Arctic nations. The results of the inversion showed that the majority of the CH4 sources currently present in high northern latitudes are poorly constrained by the existing observation network. Therefore, conclusions on trends and changes in the seasonal cycle could not be obtained for the corresponding CH4 sectors. Only CH4 fluxes from wetlands are adequately constrained, predominantly in North America. Within the period under study, wetland emissions show a slight negative trend in North America and a slight positive trend in East Eurasia. Overall, the estimated CH4 emissions are lower compared to the bottom-up estimates but higher than similar results from global inversions.

Sophie Wittig et al.

Status: open (until 22 Feb 2023)

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Sophie Wittig et al.

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Short summary
Here, an inverse modeling approach is applied to estimate CH4 sources and sinks in the Arctic from 2008 to 2019. We study the magnitude, seasonal patterns and trends from different sources during recent years. We also assess how the current observation network helps constraining fluxes. We find that constraints are only significant for North America and in a lesser extent West Siberia, where the observation network is relatively dense. We find not clear trend over the period of inversion.