HR: 11:05h
AN: U22B-04 INVITED    [Abstracts]
TI: 300,000 Years of Asian Monsoon History from Caves: Piecing Together the Patterns, Triggers, and Feedbacks of Abrupt and Orbital-Scale Climate Change
AU: * Edwards, R
EM: edwar001@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
AU: Cheng, H
EM: cheng021@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
AU: Wang, Y
EM: yjwang@njnu.edu.cn
AF: College of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Xianlin, Nanjing, 210097, China
AU: Yuan, D
EM: dxyuan@karst.edu.cn
AF: Karst Dynamics Lab, Ministry of Land and Resources, 40 Qixing Road, Guilin, 541004, China
AU: An, Z
EM: anzs@loess.llqg.ac.cn
AF: Institute of Earth Environment, Chinese Academy of Sciences, 10 Fenghui South Road, Xi'an, 710075, China
AU: Kelly, M J
EM: kell0738@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
AU: Dykoski, C A
EM: dyko0008@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
AU: Wang, X
EM: wang0452@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, United States
AB: We present a continuous 300,000-year record of the oxygen isotopic composition of cave calcite from stalagmites from Hulu, Dongge, and Shanbao Caves, in southeastern China. In its present state, the record is substantially improved in resolution (oxygen isotope resolution of a few to several decades) and range over published results. The record is, in essence, a history of the oxygen isotopic composition of meteoric precipitation through time, which, in turn, is related to monsoonal precipitation in the region. The chronology is established with precise uranium-thorium ages. The monsoon is dominated by orbital-scale variability throughout, and millennial-scale variability during glacial periods. At orbital scales, the monsoon follows northern summer insolation with no discernable phase shift, supporting a direct link between seasonal heating and the monsoon. At millennial scales, the last glacial record correlates strikingly with that observed in Greenland, with Chinese correlatives to all 25 Greenland interstadial events, and broadly similar millennial-scale sequences observed and established for the penultimate and antepenultimate glacial periods. The monsoon exhibits remarkable relationships with the ice core atmospheric gas record. A tie to the oxygen isotopic composition of atmospheric oxygen supports the idea that shifts in the monsoon and low latitude hydrology change the Dole Effect, likely through a combination of changing terrestrial productivity and changes in the average isotopic composition of waters used by land plants. A close tie to methane confirms links among atmospheric methane, the low latitude hydrologic cycle, and the extent of low-latitude wetlands. We are able to correlate features in the monsoon record to ice core, marine, and other cave records, thereby establishing, for key periods, the timing and sequence of events recorded around the globe in different surface environments. Correlation strategies include the methane-monsoon relationship to correlate cave and ice core records, a link between Heinrich Events and the monsoon to correlate cave and North Atlantic marine records, and a link between the monsoon and positions of surface currents to correlate cave and Northwest Pacific marine records. Using these strategies, we have determined the timing and sequence of events during the terminations of the last 4 glacial cycles. Our correlations place new constraints on the causes of glacial terminations, a problem that still remains unsolved despite decades of study. The relationships that we observe suggest that terminations are triggered by small orbitally-induced changes in the seasonal distribution of insolation, coupled with multiple positive feedbacks within the climate system.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4958 Speleothems
SC: Union [U]
MN: 2007 Fall Meeting