HR: 1340h
AN: PP23A-1076    [Abstracts]
TI: Late Holocene Climate Changes Derived From Multi-proxy Lake Sediment Records in the Northeastern Tibetan Plateau and Possible Solar Forcing
AU: * Zhao, C
EM: chz8@lehigh.edu
AF: Department of Earth and Environmental Sciences, Lehigh University, 31 Williams Drive, Bethlehem, PA 18015, United States
AU: Zhao, Y
EM: yanzhao@lzu.edu.cn
AF: MOE Key Laboratory of Western China Environmental System, Lanzhou University, 222 South Tianshui Road, Lanzhou, GS 730000, China
AU: Yu, Z
EM: ziy2@lehigh.edu
AF: Department of Earth and Environmental Sciences, Lehigh University, 31 Williams Drive, Bethlehem, PA 18015, United States
AU: Yu, Z
EM: ziy2@lehigh.edu
AF: MOE Key Laboratory of Western China Environmental System, Lanzhou University, 222 South Tianshui Road, Lanzhou, GS 730000, China
AU: Liu, X
EM: liuxiuju@gmail.com
AF: MOE Key Laboratory of Western China Environmental System, Lanzhou University, 222 South Tianshui Road, Lanzhou, GS 730000, China
AU: Ito, E
EM: eito@umn.edu
AF: Limnological Research Center, University of Minnesota, Minneapolis, 310 Pillsbury Drive, SE., Minneapolis, MN 55455, United States
AU: Chen, F
EM: fhchen@lzu.edu.cn
AF: MOE Key Laboratory of Western China Environmental System, Lanzhou University, 222 South Tianshui Road, Lanzhou, GS 730000, China
AB: Solar variation has been recognized as an important forcing on centennial-scale climatic changes from high to low latitudes in the North Hemisphere. In eastern Asia, several records on monsoon activities and regional temperature over the last 2000 years have been correlated to solar forcing. However, in arid Northwest China, the impact of solar forcing on regional climate variations is poorly understood due to the complex topographic setting. Moreover, few lake sediment records have been recovered with adequate resolution to investigate centennial- scale regional climate changes in this period. Recently, we obtained two short cores from two, paired, hydrologically connected but contrasting fresh and saline lakes, Hurleg Lake (core HL06-2) and Toson Lake (core TL06-1) in the northeastern Tibetan Plateau. Chronology was controlled by Pb-210 and Cs-137 analysis on both cores, 5 calibrated AMS-14C dates on plant fragments in HL06-2 and inter-site correlation. Loss-on-ignition analysis results from both cores show consistent and coherent changes in carbonate content, ranging from 30- 60% in HL06-2 and 15-35% in TL06-1. In our pilot study at Hurleg Lake, surface samples along a transect of water depth show that carbonate content increases with water depth. Ostracode and mollusc abundance in both cores shows a striking reverse relationship with carbonate content: there are abundant ostracode shells at low carbonate levels. So, increased ostracode and mollusc shells may suggest littoral environment. The preliminary data from LOI and ostracode abundance indicate clear periodic variations in effective moisture with a cycle of 218 years. Also, the Artemisia/Chenopodiaceae pollen ratios from both lakes show large oscillations between xx and xxx, with similar significant centennial periodicities. These centennial-scale oscillations at these lakes show similarities with tree-ring record during the late Holocene from mountains just north of study sites. In addition, the good correlation between our records and the oxygen isotope record from Dunde ice core may represent a wet/cool and warm/dry climate association, which is in contrast to monsoon influenced region with a wet/warm and cool/dry climate association. The similar trend between the curves from both cores indicates synchronous hydrochemical responses to climate forcing in the paired contrasting lakes, but possibly with dampened amplitude in the saline lake. Our new results and future stable isotope data likely suggest a warm/dry climate association in Eurasian continental interior and possible solar forcing for the 218 year drought frequency during the last 2000 years.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1015 Composition of the core
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting