Natural Geologic Methane Emissions
Methane is a powerful greenhouse gas and has been an important contributor to recent global warming. Important uncertainties remain in understanding today’s global methane budget. One of the largest uncertainties is the question of how fossil emissions of methane are partitioned between human-caused emissions and natural “geologic” seepage. Isotopic studies of methane in the atmosphere cannot distinguish between natural and anthropogenic fossil emissions, because from the perspective of isotopes the methane looks the same. This means that we need to know the magnitude of geologic emissions in order to be able to accurately estimate anthropogenic emissions and guide policy for reducing these emissions.
One of the ways in which we are trying to improve estimates of geologic methane emissions is the “bottom-up” approach: making measurements of ground sources and then extrapolating to larger areas.
An ongoing project is focusing specifically on understanding geologic emissions via “microseepage”, which is the widespread flux of methane to the atmosphere from the ground in areas of hydrocarbon (fossil fuel) deposits. We are making measurements in several hydrocarbon basins around the US in order to understand the parameters and relationships that determine the magnitude of microseepage emissions (for example, proximity to large methane seeps or geologic faults, characteristics of the hydrocarbon deposits, local climate and ecosystem). We will then use our measurements and the determined relationships to produce improved estimates of geologic emissions to the atmosphere.
This project has been / is being supported by NSF Awards AGS-2039234 and by the Packard Foundation.
Kazemi, R., Schlageter, W., Hmiel, B., Weber, T.S., Murray, L.T., Petrenko, V.V. 2021. Investigating methane emissions from geologic microseepage in Western New York State, United States. Elementa, 9:1. https://online.ucpress.edu/elementa/article/9/1/00066/117169/Investigating-methane-emissions-from-geologic.
Dyonisius, M.N., V.V Petrenko, A.M. Smith, Q. Hua, B. Yang, J. Schmitt, J. Beck, B. Seth, M. Bock, B. Hmiel, I. Vimont, J.A. Menking, S.A. Shackleton, D. Baggenstos, T.K. Bauska, R.H. Rhodes, P. Sperlich, R. Beaudette, C. Harth, M. Kalk, E.J. Brook, H. Fischer, J.P. Severinghaus, R.F. Weiss. 2020. Old carbon reservoirs were not important in the deglacial methane budget. Science, 367, 907 - 910. https://science.sciencemag.org/content/367/6480/907
Hmiel, B., V.V Petrenko, M.N. Dyonisius, C. Buizert, A.M. Smith, P.F. Place, C. Harth, R. Beaudette, Q. Hua, B. Yang, I. Vimont, S.E. Michel, J.P. Severinghaus, D. Etheridge, T. Bromley, J. Schmitt, X. Faïn, R.F. Weiss, E.J. Dlugokencky, Preindustrial 14CH4indicates greater anthropogenic fossil CH4emissions, Nature. 2020. https://doi.org/10.1038/s41586-020-1991-8
Petrenko, V.V., A.M. Smith, H. Schaefer, K. Riedel, E.J. Brook, D. Baggenstos, C. Harth, Q. Hua, C. Buizert, A. Schilt, X. Fain, L. Mitchell, T. Bauska, A. Orsi, R.F. Weiss, J.P. Severinghaus. 2017. Minimal geological methane emissions during the Younger Dryas – Preboreal abrupt warming event. Nature. 548, 443 – 446. https://www.nature.com/articles/nature23316