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

• Main Authors: Petrenko, VV, Severinghaus, JP, Smith, AM, Riedel, K, Brook, EJ, Schaefer, H, Baggenstos, D, Harth, C, Hua, Q, Buizert, C, Schilt, A, Fain, X, Mitchell, L, Bauska, TK, Orsi, A, Weiss, RF
• Format: Conference Object
• Language: English
• Published: American Geophysical Union 2017
• Subjects: Antartica; Methane; Atmospheres; Gas hydrates; Carbon; Hydrates; Geology; Morphology; Sea bed; Geophysics; Fractures; Geological faults; Taylor Glacier; Antarc*; Antarctica; antartic*; ice core; Methane hydrate; North Atlantic
• Online Access: http://apo.ansto.gov.au/dspace/handle/10238/8719; http://abstractsearch.agu.org/meetings/2016/FM/OS44A-04.html

Marine methane hydrate destabilization has been proposed as a potentially large source of methane to the atmosphere in response to both past and future warming. We present new measurements of 14C of paleoatmospheric methane (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 abrupt warming was centered in the North Atlantic, occurred partway through the global warming of last deglaciation and was associated with a 50% increase in atmospheric CH4 concentrations. 14C can unambiguously identify CH4 emissions from old carbon sources, such as CH4 hydrates. 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. Our results show that neither the abrupt regional warming nor the gradual global warming that preceded it resulted in detectable CH4 release to the atmosphere from CH4 hydrates during the YD PB transition. Our results are thus consistent with the hypothesis that the vast majority of CH4 that is released from dissociating hydrates or other old-carbon seafloor CH4 sources is oxidized prior to reaching the atmosphere. © American Geophysical Union