Ice core measurements of 14CH4 show no evidence of methane release to atmosphere from methane hydrates during a large warming event 11,600 years ago
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Date
2016-03-07
Journal Title
Journal ISSN
Volume Title
Publisher
Antarctic Climate and Ecosystems Cooperative Research Centre
Abstract
Thawing permafrost and marine methane hydrate destabilization have been proposed as large sources of methane to the atmosphere in response to both past and future warming.
We present measurements of 14C of paleoatmospheric CH4 over the Younger Dryas – Preboreal (YD – PB) abrupt warming event (≈11,600 years ago) from ancient ice
outcropping at Taylor Glacier, Antarctica. The YD – PB event was associated with a ≈ 50% increase in atmospheric CH4 concentrations. 14C can unambiguously identify CH4 emissions from “old carbon” sources, such as permafrost and CH4 hydrates. The only prior study of
paleoatmospheric 14CH4 (from Greenland ice) suggested that wetlands were the main
driver of the YD - PB CH4
increase, but the results were weakened by an unexpected and poorly understood 14CH4 component from in situ cosmogenic production directly in nearsurface
ice. In this new study, we have been able to accurately characterize and correct for
the cosmogenic 14CH4
component. All samples from before, during and after the abrupt warming and associated CH4 increase yielded 14CH4 values that are consistent with 14C of
atmospheric CO2 at that time, indicating a purely contemporaneous methane source. These new measurements rule out the possibility of large CH4
releases to the atmosphere from
methane hydrates or old permafrost carbon in response to the large and rapid YD - PB
warming, and confirm that wetlands were the main driver of the CH4 increase.
Description
Keywords
Pleistocene epoch, Glaciers, Greenhouse gases, Paleoclimatology, Climatic change, Antarctica, Greenland, Methane
Citation
Petrenko, V.V., Severinghaus, J.P., Smith, A.M, Riedel, K., Brook, E., Schaefer, H.,Baggenstos, D., Harth, C. M., Hua, Q., Buizert, C., Schilt, A., Fain, X., Mitchell,L., Basuka, T.K., Orsi, A. J.,& Weiss, R. F. (2016). Ice core measurements of 14CH4 show no evidence of methane release to atmosphere from methane hydrates during a large warming event 11,600 years ago. Paper presented at the IPICS 2016, International Partnerships in Ice Core Sciences, Second Open Science Conference, 7-11 March 2016, Hobart, Tasmania.