Repeated pulses of vertical methane flux recorded in glacial sediments from the southeast Bering Sea

There is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glaci...

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Bibliographic Details
Published in:Paleoceanography 2011-06, Vol.26 (2), p.np-n/a
Main Authors: Cook, Mea S., Keigwin, Lloyd D., Birgel, Daniel, Hinrichs, Kai-Uwe
Format: Article
Language:English
Subjects:
anaerobic methane oxidation
biomarkers
Dansgaard-Oeschger events
Hypotheses
Methane
Sediments
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Summary:There is controversy over the role of marine methane hydrates in atmospheric methane concentrations and climate change during the last glacial period. In this study of two sediment cores from the southeast Bering Sea (700 m and 1467 m water depth), we identify multiple episodes during the last glacial period of intense methane flux reaching the seafloor. Within the uncertainty of the radiocarbon age model, the episodes are contemporaneous in the two cores and have similar timing and duration as Dansgaard‐Oeschger events. The episodes are marked by horizons of sediment containing 13C‐depleted authigenic carbonate minerals; 13C‐depleted archaeal and bacterial lipids, which resemble those found in ANME‐1 type anaerobic methane oxidizing microbial consortia; and changes in the abundance and species distribution of benthic foraminifera. The similar timing and isotopic composition of the authigenic carbonates in the two cores is consistent with a region‐wide increase in the upward flux of methane bearing fluids. This study is the first observation outside Santa Barbara Basin of pervasive, repeated methane flux in glacial sediments. However, contrary to the “Clathrate Gun Hypothesis” (Kennett et al., 2003), these coring sites are too deep for methane hydrate destabilization to be the cause, implying that a much larger part of the ocean's sedimentary methane may participate in climate or carbon cycle feedback at millennial timescales. We speculate that pulses of methane in these opal‐rich sediments could be caused by the sudden release of overpressure in pore fluids that builds up gradually with silica diagenesis. The release could be triggered by seismic shaking on the Aleutian subduction zone caused by hydrostatic pressure increase associated with sea level rise at the start of interstadials. Key Points There are multiple episodes of intense vertical methane flux in MIS3 sediments The episodes have similar timing and duration as D‐O events These sites are too cold and deep for the Clathrate Gun Hypothesis
ISSN:0883-8305
2572-4517
1944-9186
2572-4525
DOI:10.1029/2010PA001993