HR: 1340h
AN: PP33C-1598    [Abstracts]
TI: Constraints on Late Glacial Methane Budgets From Stable Carbon Isotope Ratios
AU: * Schaefer, H
EM: schaefeh@geo.oregonstate.edu
AF: Oregon State University, 104 Wilkinson Hall, Corvallis, OR 97331 United States
AU: * Schaefer, H
EM: schaefeh@geo.oregonstate.edu
AF: University of Victoria, PO Box 3055, Victoria, BC V8W 3P6 Canada
AU: Whiticar, M J
EM: whiticar@uvic.ca
AF: University of Victoria, PO Box 3055, Victoria, BC V8W 3P6 Canada
AU: Brook, E J
EM: brooke@geo.oregonstate.edu
AF: Oregon State University, 104 Wilkinson Hall, Corvallis, OR 97331 United States
AU: Severinghaus, J P
EM: jseveringhaus@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093
AU: Petrenko, V
EM: vpetrenko@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093
AB: Measurements of stable carbon isotope ratios (δ¹³C) in samples from a West Greenland horizontal ice core provide constraints for methane sources in the Younger Dryas (YD) cold period and throughout the abrupt climate transition into the Preboreal (PB) warm stage. All measured isotope ratios during this interval are more enriched in ¹³C than the modern atmosphere, indicating that commonly used natural methane budgets are either missing a ¹³C-rich source type or that δ¹³C of major emissions, e.g. from tropical wetlands, is different than assumed. The rapid methane concentration increase at the end of the YD is not associated with changes in δ¹³C, which is not compatible with any of the main hypotheses regarding the origin of the concentration increase. An abrupt burst of methane from marine clathrates is ruled out, and gradual release from this source is severely constrained by the presented data. A combination of decreased sink strength and emissions from a ¹³C-rich source is the most likely scenario. The δ¹³C of this implied source lies between typical values for biogenic and thermogenic methane and its nature cannot be resolved with current knowledge of natural methane budgets.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0714 Clathrate
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005