Potential of Clumped Isotopes in Constraining the Global Atmospheric Methane Budget
Chung, Edward and Arnold, Tim LU
(2021)
In Global Biogeochemical Cycles
35(10).
- Abstract
Atmospheric methane (CH4) and its isotopic composition trends over the last decades are explained by various flux scenarios, from tropical wetland emission increases through to reductions in global hydroxyl (OH). In this study, we develop a modeling framework to assess the potential usefulness of clumped isotope measurements to distinguish between the main drivers of change in the CH4 burden. We model interhemispheric differences of 0.12‰ and 0.38‰ and seasonal cycles of 0.02‰–0.04‰ and 0.21‰–0.32‰ for Δ13CH3D and Δ12CH2D2, respectively, which is insignificant relative to the uncertainty of measurements that could eventually be made. We show, however, that... (More)
Atmospheric methane (CH4) and its isotopic composition trends over the last decades are explained by various flux scenarios, from tropical wetland emission increases through to reductions in global hydroxyl (OH). In this study, we develop a modeling framework to assess the potential usefulness of clumped isotope measurements to distinguish between the main drivers of change in the CH4 burden. We model interhemispheric differences of 0.12‰ and 0.38‰ and seasonal cycles of 0.02‰–0.04‰ and 0.21‰–0.32‰ for Δ13CH3D and Δ12CH2D2, respectively, which is insignificant relative to the uncertainty of measurements that could eventually be made. We show, however, that measurements of Δ12CH2D2 specifically could provide constraints for understanding trends in the global total source and sink magnitudes, which has not been possible with the current sets of observables. Changes in OH concentration of 10% developed across three decades result in a difference of up to 2‰ in Δ12CH2D2, which would be observable given current measurement uncertainty limits. For this type of global-scale analysis, we show that measurements of Δ13CH3D would be unlikely to provide additional useful information. We suggest an emphasis should now be on developing the methods to make measurements from ambient air samples, followed by measurements of Δ13CH3D and Δ12CH2D2 from sampling at clean Northern and Southern Hemisphere sites, combined with more accurate and precise laboratory measurements of the clumped kinetic isotope effects relevant for the atmospheric sinks.
(Less)
- author
- Chung, Edward
and Arnold, Tim
LU
- publishing date
- 2021-10
- type
- Contribution to journal
- publication status
- published
- in
- Global Biogeochemical Cycles
- volume
- 35
- issue
- 10
- article number
- e2020GB006883
- publisher
- Wiley-Blackwell
- external identifiers
-
- scopus:85118247459
- ISSN
- 0886-6236
- DOI
- 10.1029/2020GB006883
- language
- English
- LU publication?
- no
- additional info
- Publisher Copyright: © 2021. American Geophysical Union. All Rights Reserved.
- id
- f902143c-4875-4bc2-b3b3-c85095be74d2
- date added to LUP
- 2024-10-22 10:17:30
- date last changed
- 2025-05-07 02:30:28
@article{f902143c-4875-4bc2-b3b3-c85095be74d2,
abstract = {{<p>Atmospheric methane (CH<sub>4</sub>) and its isotopic composition trends over the last decades are explained by various flux scenarios, from tropical wetland emission increases through to reductions in global hydroxyl (OH). In this study, we develop a modeling framework to assess the potential usefulness of clumped isotope measurements to distinguish between the main drivers of change in the CH<sub>4</sub> burden. We model interhemispheric differences of 0.12‰ and 0.38‰ and seasonal cycles of 0.02‰–0.04‰ and 0.21‰–0.32‰ for Δ<sup>13</sup>CH<sub>3</sub>D and Δ<sup>12</sup>CH<sub>2</sub>D<sub>2</sub>, respectively, which is insignificant relative to the uncertainty of measurements that could eventually be made. We show, however, that measurements of Δ<sup>12</sup>CH<sub>2</sub>D<sub>2</sub> specifically could provide constraints for understanding trends in the global total source and sink magnitudes, which has not been possible with the current sets of observables. Changes in OH concentration of 10% developed across three decades result in a difference of up to 2‰ in Δ<sup>12</sup>CH<sub>2</sub>D<sub>2</sub>, which would be observable given current measurement uncertainty limits. For this type of global-scale analysis, we show that measurements of Δ<sup>13</sup>CH<sub>3</sub>D would be unlikely to provide additional useful information. We suggest an emphasis should now be on developing the methods to make measurements from ambient air samples, followed by measurements of Δ<sup>13</sup>CH<sub>3</sub>D and Δ<sup>12</sup>CH<sub>2</sub>D<sub>2</sub> from sampling at clean Northern and Southern Hemisphere sites, combined with more accurate and precise laboratory measurements of the clumped kinetic isotope effects relevant for the atmospheric sinks.</p>}},
author = {{Chung, Edward and Arnold, Tim}},
issn = {{0886-6236}},
language = {{eng}},
number = {{10}},
publisher = {{Wiley-Blackwell}},
series = {{Global Biogeochemical Cycles}},
title = {{Potential of Clumped Isotopes in Constraining the Global Atmospheric Methane Budget}},
url = {{http://dx.doi.org/10.1029/2020GB006883}},
doi = {{10.1029/2020GB006883}},
volume = {{35}},
year = {{2021}},
}