Spatially Resolved Isotopic Source Signatures of Wetland Methane Emissions. Issue 8 (21st April 2018)

• Record Type: Journal Article
• Authors: Ganesan, A. L.; Stell, A. C.; Gedney, N.; Comyn‐Platt, E.; Hayman, G.; Rigby, M.; Poulter, B.; Hornibrook, E. R. C.
• Is Part Of: Geophysical research letters. Volume 45:Issue 8(2018)
• Page Start: 3737
• Page End: 3745
• Publication Date: 2018-04-21
• Subjects: wetlands -- methane -- greenhouse gas -- isotopes; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2018GL077536
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We present the first spatially resolved wetland δ 13 C(CH4 ) source signature map based on data characterizing wetland ecosystems and demonstrate good agreement with wetland signatures derived from atmospheric observations. The source signature map resolves a latitudinal difference of ~10‰ between northern high‐latitude (mean −67.8‰) and tropical (mean −56.7‰) wetlands and shows significant regional variations on top of the latitudinal gradient. We assess the errors in inverse modeling studies aiming to separate CH4 sources and sinks by comparing atmospheric δ 13 C(CH4 ) derived using our spatially resolved map against the common assumption of globally uniform wetland δ 13 C(CH4 ) signature. We find a larger interhemispheric gradient, a larger high‐latitude seasonal cycle, and smaller trend over the period 2000–2012. The implication is that erroneous CH4 fluxes would be derived to compensate for the biases imposed by not utilizing spatially resolved signatures for the largest source of CH4 emissions. These biases are significant when compared to the size of observed signals. Plain Language Summary: Concentrations of methane are increasing in the atmosphere. In order to understand the reasons behind such variations, carbon isotopes are used to help identify changes in emission sources and sinks. We present a new global map of the carbon isotope signature associated with wetland methane emissions, the largest global source of methane to the atmosphere. We show how this newly synthesized information can lead to more accurate understanding of the causes of variations in the amount and rate of increase of methane in the atmosphere. Key Points: Large regional differences exist in wetland methane isotopic source signatures Spatially resolved methane isotope signatures are critical for simulating atmospheric variability Biases will result in atmospheric inversions if spatial patterns are not accounted for in methane isotope source signatures