HR: 1340h
AN: PP13A-0581    [Abstracts]
TI: A Multiproxy Record of Marine Isotope Stage 11 (MIS 11) in the South China Sea (IMAGES-Core MD972142)
AU: * Lowemark, L A
EM: ludvig@earth.sinica.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 100 Taiwan
AU: Wei, K
EM: weiky@ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 100 Taiwan
AU: Wang, C
EM: chwang@earth.sinica.edu.tw
AF: Institute of Earth Sciences, Academia Sinica, P.O. Box 1-55, Nankang, Taipei, 115 Taiwan
AU: Song, S
EM: srsong@ccms.ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 100 Taiwan
AU: Chen, M
EM: mtchen@mail.ntou.edu.tw
AF: Institute of Applied Geosciences, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung, 20224 Taiwan
AU: Shiau, L
EM: ryoken@ms69.url.com.tw
AF: Institute of Applied Geosciences, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung, 20224 Taiwan
AU: Mii, H
EM: t44006@cc.ntnu.edu.tw
AF: Department of Earth Sciences, National Taiwan Normal University, No. 88, Sec.4, Ting Chou Road, Taipei, 11676 Taiwan
AU: Stephan, S
EM: ssteinke@uni-bremen.de
AF: Research Center Ocean Margins, Fachbereich Geowissenschaften, Universit„t Bremen, Postfach 33 04 40, Bremen, 28334 Germany
AB: A growing amount of evidence suggests that the tropics play an important role in the global climate system through their influence on the global heat and moisture budgets. Slight variations in sea surface temperature of the tropical oceans can influence the global climate through atmospheric teleconnections as demonstrated by the El Nino-Southern Oscillation phenomenon. The modern surface circulation in the South China Sea is strongly influenced by the East Asian monsoon system. The fact that the surface layers of the ocean respond "immediately" to changes in surface wind field allows a test of model predictions of changes in the monsoon system over glacial-interglacial cycles, as variations in the upper water structure are recorded by the isotopic composition of different foraminiferal species. Furthermore, the Asian monsoon controls seasonal winds, precipitation, land vegetation, volume and mineralogy of continental run-off, and flux of wind blown dust. Thus, the sediments in the South China Sea provide not only Quaternary paleoceanographic records, but also a record of variations in Southeast Asian continental climate. Here we present a comparison of multiproxy records from MIS 1-6 with records from MIS 10-12 from the southeastern South China Sea. First results show a clear glacial-interglacial signal in most measured parameters. Strongly increased TOC and heavier $\delta$ $^{13}$C$_{org}$ values were observed during the glacials compared to interglacials. To explain the observed changes in $\delta$ $^{13}$C$_{org}$ with variations in terrestrial input would require a massive change in the relative amount of terrestrial input in connection with a major shift toward C4 plants in the land vegetation. It seems more plausible to explain the increased TOC as an effect of increased marine productivity during glacial conditions. An increased difference in stable oxygen isotopes between the foraminifers {\it G. ruber} and {\it N. dutertrei} during interglacial compared to glacial conditions is interpreted as a result of weaker mixing of the upper water masses, likely due to a decrease in winter monsoon intensity. Conversely, the intensified winter monsoon under glacial conditions led to stronger mixing and an increased primary productivity reflected in stable carbon isotopes of the different foraminifer species as well as the TOC and $\delta$ $^{13}$C$_{org}$-records. Fluctuations in carbonate concentration and major elements primarily reflect variations in the input of terrigenous material. The sodium and phosphorus content reflect variations in weathering intensity. Partly contradictory data of opal, phosphorus and TOC data further emphasize the importance of an improved understanding of upper water hydrographic variations. Glacial-interglacial variations in Manganese content suggest fluctuations in the oxygenation of the deep-water masses, possibly related to the semi-enclosed nature of the basin during glacial times.
DE: 4243 Marginal and semienclosed seas
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
DE: 3030 Micropaleontology
DE: 1050 Marine geochemistry (4835, 4850)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting