HR: 0800h
AN: PP11B-1463    [Abstracts]
TI: Orbital-Scale Variability of Deep-Water Circulation in the South China Sea
AU: * Loewemark, L A
EM: ludvig@ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 106 Taiwan
AU: Wei, K
EM: weiky@ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 106 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: Lee, C
EM: cylee@ccms.ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 106 Taiwan
AU: Song, S
EM: srsong@ccms.ntu.edu.tw
AF: Institute of Geosciences, National Taiwan University, P.O. Box 13-318, Taipei, 106 Taiwan
AU: Chen, M
EM: mtchen@mail.ntou.edu.tw
AF: Institute of Applied Geosciences, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung, Keelung, 20224 Taiwan
AU: Shiau, L
EM: shiaulj@earth.sinica.edu.tw
AF: Institute of Applied Geosciences, National Taiwan Ocean University, 2 Pei-Ning Road, Keelung, Keelung, 20224 Taiwan
AU: Mii, H
EM: t44006@cc.ntnu.edu.tw
AF: Department of Earth Sciences, National Taiwan Normal University, 162, HePing East Road, Taipei, 106 Taiwan
AU: Steinke, S
EM: ssteinke@uni-bremen.de
AF: Research Center Ocean, Geowissenschaften, University Bremen, Postfach 33 04 40, Bremen, 28334 Germany
AU: Lin, H
EM: hllin@mail.nsysu.edu.tw
AF: National Sun-Yat Sen University, 70 Lien-hai Rd., Kaohsiung, 804 Taiwan
AU: Kao, S
EM: sjkao@gate.sinica.edu.tw
AF: Research Center for Environmental Changes, Academia Sinica, P.O. Box 1-55, Nankang, Taipei, 115 Taiwan
AB: Sedimentary records covering approximately the last four glacial-interglacial cycles from two cores from the northern and southeastern South China Sea were used to reconstruct variations in deep-water circulation. Core MD972142 (12°41.33'N, 119°27.90'E) was retrieved at a water depth of 1557 m at the continental slope off Palawan Island during the 1997 IMAGES-III-IPHIS Cruise, and the 1215 cm long piston core GIK17925-3 (119°2.8'E, 19°51.2'N, 2980 m water depth) was taken from the north-eastern South China Sea during the SONNE 95 cruise in 1994. Sedimentary organic carbon (TOC) content shows a strong glacial-interglacial cyclicity with enhanced values during glacial periods, but also higher frequency oscillations corresponding to precession and obliquity controlled insolation variations. Stable carbon isotopes of the organic carbon suggest that increased marine productivity rather than changes in terrestrial input is responsible for the fluctuations in TOC. Proposed explanations for these increased glacial levels of TOC include enhanced primary productivity due to stronger mixing of surface waters by the winter monsoon or nutrient trapping caused by decreased exchange with the open ocean during sea-level low-stands. Manganese/Aluminum and Phosphorus/Aluminum ratios, however, suggest major variations in bottom water oxygenation related to sea level changes with clearly decreased bottom water oxygenation during glacial maxima and well-oxygenated conditions during peak interglacial conditions. We therefore propose that the TOC record is a palimpsest record of short-term productivity signals primarily controlled by insolation variations and longer-term preservation signals governed by variations in deep-water circulation, ultimately controlled ice-volume/sea-level variations.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1051 Sedimentary geochemistry
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4934 Insolation forcing
DE: 4999 General or miscellaneous
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005