HOW CLOSELY ARE MILLENNIAL SCALE BENTHIC 18O AND ANTARCTIC ICE RECORDS RELATED?

Core MD 98-2165 (9°38'96 S, 118°20'31 E, 2100 m) from the Tropical Indian Ocean and core MD 00-2374 (46°02 S, 96°29 E, 3250m) from the Subantarctic Indian Ocean have been studied at a time resolution of about 200 y over the two last climatic cycles within the POP project. The oxygen and carbon isotopic composition (d¹⁸O and d¹³C) of benthic and planktonic foraminifera has been measured. The benthic d¹⁸O records are remarkably similar to the ice deuterium (dD) or d¹⁸O records of Antarctica. This finding indicates that the impressive similarity found between a benthic d¹⁸O record from the Iberian Margin and Vostok dD (Shackleton, 2000) between 24 and 64 ky BP, is likely a global feature that prevailed during past glacial periods. Correlating our high resolution benthic d¹⁸O records to Dome Fuji ice d¹⁸O record dated by the inverse approach of Parrenin et al. (2001), we obtain a high resolution marine time scale that is consistent with the Antarctic ice cores time scales. Moreover, the error on the relative age of the marine versus ice core records is necessarily lower than the duration of the millennial events recognised in both records, yielding a great improvement in our ability to compare marine and ice records over the last three to four climatic cycles.

In this new marine chronology, we examine the relative timing of changes in surface and deep-water variability recorded at the low latitude site with respect to that recorded at the subantarctic site. Finally, we discuss the links between the records of surface hydrology generated for the Indian Ocean POP cores and the air temperature and atmospheric methane concentration records from Antarctic ice cores.