HR: 0800h
AN: PP11B-0526    [Abstracts]
TI: Indonesian Throughflow and Australasian Monsoon Variability Over the Last two Glacial Cycles
AU: * Kuhnt, W
EM: wk@gpi.uni-kiel.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Holbourn, A
EM: ah@gpi.uni-kiel.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Xu, J
EM: jx@gpi.uni-kiel.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Nuernberg, D
EM: dnuernberg@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, Wischhofstr. 1-3, Kiel, D-24148, Germany
AU: Bolliet, T
EM: tb@gpi.uni-kiel.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Duerkop, A
EM: anked@gpi.uni-kiel.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Zuraida, R
EM: rzuraida@ifm-geomar.de
AF: Institute of Geosciences, Christian-Albrechts University, Olshausenstr. 40, Kiel, D-24118, Germany
AU: Zuraida, R
EM: rzuraida@ifm-geomar.de
AF: Leibniz-Institute of Marine Sciences, Wischhofstr. 1-3, Kiel, D-24148, Germany
AU: Kawamura, H
EM: hkawamura@iodp-mi-sapporo.org
AF: IODP Management International, N10 W8, Kita-ku, Sapporo, 060-0810, Japan
AB: The climate and hydrography of the tropical Indian Ocean are strongly influenced by the intensity and vertical profile of the Indonesian Throughflow (ITF) and seasonal changes in wind direction associated with the southward migration of the Intertropical Convergence Zone (ITCZ) during austral summer. We use a multiproxy approach to reconstruct monsoonal wind and circulation patterns along the NW Australian continental margin as well as changes in the vertical profile of the Indonesian Throughflow on glacial, precessional and suborbital timescales. Our records from the Timor Passage and Timor Sea (Sonne 185 and IMAGES WEPAMA cruises) closely track changes in the structure of the upper water column within one of the main outflow passages of the ITF. We use (1) XRF scanning records to reconstruct continental runoff and eolian dust transport, (2) paleoproductivity proxy data related to vertical mixing of the upper water column by monsoonal winds, (3) SST, SSS and mixed layer thickness estimates from combined oxygen isotope and Mg/Ca analyses of surface and thermocline dwelling planktonic foraminifers. XRF-scanner derived terrigenous flux and paleoproductivity fluctuations over the last 460 ky were strongly influenced by monsoonal wind patterns offshore NW Australia (23 and 19 ky), the position of the ITCZ (southward shift during precession minima) and were also modulated by sea-level related variations in the intensity of the ITF (100 ky). Our results indicate that the intensity of the Australian summer monsoon over the last two glacial cycles was controlled both by summer insolation over NW Australia and by the strength of the boreal winter monsoon, as the southward migration of the ITCZ is closely linked to northern hemisphere cooling. A comparison of water mass properties within the main outflow in the Timor Strait and within the mixing zone between ITF and eastern Indian Ocean waters reveals a higher thermocline temperature gradient between the eastern Indian Ocean and Timor Strait during glacials and stadials, implying a decrease in ITF thermocline flow. Centennial records spanning Terminations I and II reveal cooling and freshening of thermocline waters during the early part of MIS5e and early Holocene, indicating a change from surface to thermocline dominated ITF flow, when the ITCZ moves southward and Australian monsoon strengthens.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting