HR: 0800h
AN: PP51F-1366    [Abstracts]
TI: Alkenone and planktic foraminifer sea-surface temperature reconstructions at ODP Site 1240: 500-900 kya
AU: * Yu, P
EM: menardii@sinamail.com
AF: Institute of Applied Geosciences, National Taiwan Ocean University, 2, Pei-Ning, Keelung, 20224 Taiwan
AB: One of the objectives of ODP Leg 202 is to retrieve high-resolution sediment cores from the eastern equatorial Pacific, an area in which modern interannual-scale climate are dynamically fluctuating. In this study we aimed to reconstruct paleoceanographic records from the ODP Site 1240 (0o1.311'N; 86o27.758'W; WD: 2921m) from the Leg 202. One of our objectives in the paleoceanographic reconstructions is to better understand how tropical oceans interact with global climate over orbital time scales, and focus on testing hypotheses of ENSO-like oscillation and of extra-tropical forcing prevailed in long-term climate variations in the tropics. We are especially interested in examining an abnormally "warm and wet" climate in glacial MIS 14 shown in Chinese loess and South China Sea marine records and looking for any tropical origin of forcing or feedback for explaining the abnormality. Site 1240 was chosen for this purpose as this site is ideal for monitoring upwelling and circulation changes in the eastern equatorial Pacific, and is likely very sensitive to if any ENSO-like oscillations occurred in this particular time interval. In this preliminary study, the age model of cores from Site 1240 was constructed primarily based upon 4 calcareous nannofossil datums at the top 80 meters composite depth (mcd) and the average sedimentation rate is ~10cm/kyr. We have also generated alkenone SSTs from an interval of 500-900 kya of the cores. Initial observations indicate that high alkenone concentrations are associated low SSTs and vice versa at this interval. Alkenone SSTs calculated from Prahl's equation show an amplitude ~$4-5\deg$C variations over major glacial-interglacial periods in this interval and suggest a dynamic climate pattern in the EEP. Comparison of the alkenone SSTs and relatively low-resolution planktic foraminifer fauna MAT-SSTs also indicates that these two estimates appear to be of similar amplitudes, though the MAT-SSTs are apparently warmer than alkenone SSTs by ~$1-2\deg$C. In the interval equivalent to MIS 13-15 based on our very initial age model, both SST proxies show large cooling (~$4\deg$C) which suggest a strong equatorial circulation at this time.
DE: 9355 Pacific Ocean
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting