HR: 15:25h
AN: PP13B-08    [Abstracts]
TI: Dansgaard-Oeschger Cycles in Marine Isotope Stages 3 and 6
AU: * Shackleton, N J
EM: njs5@cam.ac.uk
AF: Department of Earth Sciences University of Cambridge, Godwin Laboratory Pembroke Street, Cambridge, CB2 3SA United Kingdom
AU: Vautravers, M
EM: mv217@cus.cam.ac.uk
AF: Department of Earth Sciences University of Cambridge, Godwin Laboratory Pembroke Street, Cambridge, CB2 3SA United Kingdom
AB: The oxygen isotope record of Marine Isotope Stage (MIS) 3 planktonic foraminifera in deep-sea sediment cores from the Iberian Margin is readily correlated to the oxygen isotope record in Greenland ice (Johnsen et al., J.Quat. Sci. 16, 299, 2001). Shackleton et al. (Paleoceanography 15, 565, 2000) analysed core MD95-2042 and placed the data on a Greenland ice age scale; they then showed that the benthic record closely resembles the D/H record of theAntarctic Vostok ice core (Petit et al., Nature 399, 429, 2000) when this is put on a consistent age scale using methane in the air bubbles to synchronise the records (Blunier et al., Nature 394, 739, 1998). We have analysed core MD01-2444 from 2656m water depth and have replicated this relationship; indeed with a closer sampling interval (3-cm) the resemblance between the benthic oxygen isotope (Globobulimina affinis) and the Antarctic D/H records is even more striking. The estimated standard error for G. affinis analysed in groups of about 12 is ñ0.06%. Analyses for Hoeglundina elegans, Uvigerina peregrina and Cibicidoides wuellerstorfi (groups of 1 - 3) are slightly more scattered (about ñ0.13%). Globobulimina affinis lives in the sediment where dissolved oxygen approaches zero, so that its carbon isotopic composition provides information on the water mass at its source, rather than providing information on the deepwater mass at the core site. The G. affinis carbon isotope record in MD01-2444 parallels the G. affinis oxygen isotope record, suggesting that this oxygen isotope record may be dominantly a water mass record and not primarily an ice-volume record. Core MD01-2444 extends to late MIS7 at about 190 ka. The benthic oxygen isotope record of MIS6 (sampled at 3-cm intervals, equivalent to about 300 years) contains a pattern of stadial-interstadial variability that can be convincingly correlated to the D/H record in the Vostok ice core. The triplet of interstadials older than 165 ka appear to have the same planktonic-benthic phase relationship as is observed in MIS3, suggesting that the "bipolar seesaw" was operating during that interval as during MIS3.
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting