HR: 13:40h
AN: PP33D-01    [Abstracts]
TI: Holocene Moisture Variations and Atmospheric Circulation Controls in the Qaidam Basin, Northwest China
AU: * Yu, Z
EM: ziy2@lehigh.edu
AF: Lehigh University, Department of Earth and Environmental Sciences, 31 Williams Drive, Bethlehem, PA 18015, United States
AU: * Yu, Z
EM: ziy2@lehigh.edu
AF: Lanzhou University, MOE Key Laboratory of Western China Environmental System, College of Earth and Environmental Sciences, Lanzhou, 730000, China
AU: Zhao, Y
EM: yanzhao@lzu.edu.cn
AF: Lanzhou University, MOE Key Laboratory of Western China Environmental System, College of Earth and Environmental Sciences, Lanzhou, 730000, China
AU: Zhao, C
EM: chz8@lehigh.edu
AF: Lehigh University, Department of Earth and Environmental Sciences, 31 Williams Drive, Bethlehem, PA 18015, United States
AU: Ito, E
EM: eito@umn.edu
AF: University of Minnesota, Limnological Research Center, Department of Geology and Geophysics, 310 Pillsbury Drive SE, Minneapolis, MN 55455, United States
AU: Chen, F
EM: fhchen@lzu.edu.cn
AF: Lanzhou University, MOE Key Laboratory of Western China Environmental System, College of Earth and Environmental Sciences, Lanzhou, 730000, China
AB: Regional climates in NW China are controlled by the interplay between the Asian summer monsoon, extratropical westerly circulation, and the topography of the Tibetan Plateau. Here we present sedimentary evidence from three lake basins in the Qaidam Basin on the NE Tibetan Plateau to investigate variations in effective moisture and their possible connection with changes in atmospheric circulation during the Holocene. The climate history derived from multiple proxy data of two cores from Hurleg Lake, including lithology, pollen, calcite isotopes, and ostracode isotopes and trace elements, indicates a dry climate at 11-9 ka (calibrated ages), a wettest climate at 9-8 ka (including evidence of laminated sediments), a highly variable and dry mid-Holocene, and a wet climate after 3 ka. This moisture pattern appears to be out of phase with that expected from Holocene monsoon history, including the record from Qinghai Lake (250 km east of our study sites), and with other records in westerly- dominated region. We attribute this spatially-contrasting pattern to secondary vertical circulation dynamics as modulated by insolation and topography. In particular, the intense heating and uplifting of air over the Tibetan Plateau accompanied by dry subsiding air in the surrounding areas, including the Qaidam Basin, are a likely explanation for the out-of-phase relationship, as high summer insolation would cause strong monsoon in SE China and on the Tibetan Plateau, but at the same time strong subsiding air and dry climate in the surrounding regions. Also, we speculate that a threshold response to slow changes in insolation during the Holocene might have caused shifts in the relative dominance of these competing controlling factors, that is, direct monsoon precipitation, westerlies, and topography-induced subsiding air motion. This shifting dominance might explain the changes in phasing relationship at 8 ka and 6 ka between the Qaidam Basin, the westerly region and monsoonal region.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1637 Regional climate change
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4952 Palynology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting