HR: 0800h
AN: PP51C-0610    [Abstracts]
TI: Paleocene-Eocene Boundary: Methane Hydrate Reservoirs on a Warm Earth
AU: * Lyle, M
EM: mlyle@cgiss.boisestate.edu
AF: Boise State University, CGISS Dept, MS 1536 1910 University Drive, Boise, ID 83725 United States
AU: Huber, M
EM: huberm@purdue.edu
AF: Purdue University, Dept of Earth and Atmospheric Science, West Lafayette, IN 47907 United States
AU: Olivarez Lyle, A
EM: aml@cgiss.boisestate.edu
AF: Boise State University, CGISS Dept, MS 1536 1910 University Drive, Boise, ID 83725 United States
AB: A large release (ca. 2000 Gt C) of methane from gas hydrates may have been the cause of the Paleocene-Eocene Thermal Maximum (PETM) an important warm climate transient that occurred at 55 Ma. The amount of methane outgassed at the PETM, estimated by the carbon isotope change at the Paleocene-Eocene boundary, is comparable to estimates of the size of the modern global methane hydrate reservoir even though ocean temperatures at 55 Ma were roughly 10 degrees C warmer than modern conditions. Warm oceans present a problem for buildup of hydrate reservoirs, since methane hydrate would only be stable at a water depth below around 1.5 km in an average Paleocene water column. Methane hydrates should thus have been confined to the slopes of continental margins. Since the rain of particulate organic carbon falls off away from shore, it is rare to have high enough organic carbon rain on continental slopes to drive high rates of methanogenesis and formation significant methane hydrate deposits. Few margins could support large deposits of methane hydrates. Two factors accelerate the production of methane and its capture as a hydrate: low temperature and low salinity. Low temperature helps to decrease the minimum depth of hydrate stability and opens more continental margin area for hydrate storage. Low salinity reduces the amount of organic matter degradation through sulfate reduction and increases the total amount of methane production per unit of organic carbon. Both low salinity and relatively low temperature should have been found in the Arctic in the Paleocene, and recently completed IODP drilling in the Arctic confirms low salinity. It is likely that the Arctic may have been the major methane hydrate reservoir at 55 Ma, and Arctic temperature fluctuations caused the catastrophic methane release at the PETM.
DE: 0428 Carbon cycling (4806)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4930 Greenhouse gases
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005