HR: 0800h
AN: PP31A-0173    [Abstracts]
TI: Mid-Holocene South China Sea Paleoceanographic reconstruction using corals from the Northern Philippines coast
AU: * Kobayashi, T
EM: tatsuya.k@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
AU: Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
AU: Yokoyama, Y
EM: yokoyama@eps.s.u-tokyo.ac.jp
AF: Institute for Earth Evolution, Japan Agency for Earth-Marine Science and Technology, 2-15 natsusimacyo, Yokosuka, 237-0061, Japan
AU: Suzuki, A
EM: a.suzuki@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba central No. 7, 1-1-1 Higashi, Tsukuba, 305- 8567, Japan
AU: Siringan, F P
EM: fpsiringan@upmsi.ph
AF: Marine Science Institute, University of the Philippines, Velasquez Street, Quezon, 1101, Philippines
AU: Maeda, Y
EM: holma@kcc.zaq.ne.jp
AF: Institute for Environmental Sciences, Hyogo Prefectural University, 1-3-3 Higashikawasakicyo, tyuo-ku, Kobe, 650-0044, Japan
AU: Minoshima, K
EM: kayo.minoshima@aist.go.jp
AF: Geological Survey of Japan, AIST, Tsukuba central No. 7, 1-1-1 Higashi, Tsukuba, 305- 8567, Japan
AU: Matsuzaki, H
EM: hmatsu@n.t.u-tokyo.ac.jp
AF: Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
AU: Kawahata, H
EM: kawahata@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164- 8639, Japan
AB: South China Sea (SCS) is a pivotal area to understand the past variability of the East Asian Monsoon system, because it is a major moisture source for the Eastern Eurasian continent. High resolution speleothems records as well as sediment cores from inland lake suggested progressive decreased monsoon intensity during the Holocene. Recently, several high-resolution coral-based reconstructions of Holocene paleoclimate have been reported from the northern margin of the SCS, mostly from Hainan Island (e.g Sun et al., 2005). However, no such study has been conducted along the eastern part of the SCS. We studied, therefore, modern and fossil Porites corals using delta 18O from Luzon Island, the Philippines, in order to reconstruct the paleoceanography in the region. As annual extension rates of the samples well exceeded ~5mm/year, coral delta 18O values can be used as a reliable climate proxy for temperature and salinity of the region. Corals from the Philippines with mid- Holocene ages (4.0-6.1ky BP) showed ~0.62 permil higher delta 18O values compared to the modern corals. Similar delta 18O annual variations between the modern and fossil corals suggest that the seasonality variation between the two time periods is negligible. We compared our coral delta 18O records with Hainan island corals, located in the same latitude in the SCS but in the west coast, to examine the relative contributions from changes in temperature and salinity between the modern and mid-Holocene. Two components can be distinguished since Hainan island corals have been measured both delta 18O and Sr/Ca ratios (Yu et al., 2005). The modern delta 18O difference between Luzon and Hainan corals corresponds well with the differences in sea surface temperature (SST: ~2.9 degrees C) between the two regions. Given that the same SST difference had been existed during the Holocene in the two regions, the Luzon Island SST was higher than the modern as much as 1.6 degrees C. Consequently, at least 0.91 permil of delta 18O has to be attributed as the changing seawater isotopes namely seawater off Luzon Island should had been higher than the present. Assuming that SCS has been a major moisture source during the Holocene, coral records evidently captured the signatures of the East Asian Summer Monsoon intensity variations throughout the Holocene has also influence on in the oceanographic conditions of SCS.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4875 Trace elements (0489)
DE: 4916 Corals (4220)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting