HR: 16:15h
AN: OS42C-02    [PDF]
TI: The Clathrate Gun is firing blanks: Are there alternative scenarios?
AU: * Maslin, M
EM: mmaslin@geog.ucl.ac.uk
AF: University College London, Department of Geography, 26 bedford Way, London, WC1H 0AP United Kingdom
AU: Ridgwell, A
EM: andyr@citrus.ucr.edu
AF: University of California, Department of Earth Sciences, Riverside, CA 92521 United States
AB: Kennett et al. (2003) have proposed the release of clathrates as the primary cause of the rapid increases in atmospheric methane seen during deglaciation and the warm Dansgaard-Oeschger (D-O) events. To balance the global carbon isotope budget and make a deglacial biospheric carbon transfer of $\sim$1000 GtC compatible with the marine carbon isotope data, we deduce a release of $\sim$120 GtC gas hydrate methane (Maslin and Thomas, 2003). Compilation of the occurrence of continental slope failures over the last 45 ka supports the suggestion that there was large release of gas hydrates during the Allerod-Bolling and Pre-Boreal periods. But 120 GtC represents less than 30 percent of the enhanced atmospheric methane release between 18 and 8 ka observed in ice cores, leaving 70 percent unaccounted for. We outline a new model for driving atmospheric methane changes due to flooding and decomposition of organic rich continental shelf sediments by rising sea level, which may explain the very rapid rise in methane during both the Allerod-Bolling and Pre-Boreal periods. The underlying increase between glacial and interglacial methane however we maintain is due to the expansion of tropical wetlands. Compilation of the occurrence of continental slope failures suggest that during the last glacial period they occur during Heinrich events. This does not support the Clathrate Gun Hypothesis, which requires gas hydrates release synchronous with the warm D-O events. We therefore conclude that a continental shelf flooding hypothesis is a more plausible explanation, as rapid rises in sea level associated with the warm D-O cycles provides a direct and synchronous causal mechanism.
DE: 1890 Wetlands
DE: 3309 Climatology (1620)
DE: 3344 Paleoclimatology
DE: 4805 Biogeochemical cycles (1615)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting