Linking Surface Hydrology in the Tropical Indian Ocean, Ocean Circulation, and Atmospheric Methane Over the Last two Climatic Cycles
Abstract
Core MD 98-2165 (9° 38'96 S, 118° 20'31 E, 2100 m) from the tropical Indian Ocean has been studied at a time resolution of about 200 y over the two last climatic cycles within the POP project. Oxygen and carbon isotopic composition (δ 18O and δ 13C) of benthic and planktonic foraminifera has been measured. The benthic d18O record is remarkably similar to Antarctica ice deuterium (δ D) or δ 18O records. 15 AMS 14C dates covering the last 26 kyrs allowed us to verify that our benthic δ 18O record is perfectly synchronous with the ice records. This finding indicates that the impressive similarity found between a benthic δ 18O record from the Iberian Margin and Vostok δ D (Shackleton, 2000) between 24 and 64 kyrs BP, is not restricted to this particular deep sea core and to marine isotopic stage 3. Correlating our high resolution benthic δ 18O records to Dome Fuji ice δ 18O record dated by the inverse approach of Parrenin et al. (2001), we obtain a high resolution marine time scale which 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, hence yielding a great improvement in our ability to compare marine and ice records over the last two to three climatic cycles. In this new marine chronology, we examine the relative timing of changes in surface and deep-water variability in the tropical Indian Ocean with respect to the air temperature and atmospheric methane concentration records from Antarctic ice cores. Our results highlight a tight correspondence between sea surface salinity in the tropics and atmospheric methane concentration. In contrast, the millennial scale climatic variability characterising glacial periods does not exhibit a clear relationship between sea surface salinity in the tropical Indian Ocean and atmospheric methane concentration.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFMPP22A1192W
- Keywords:
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- 1620 Climate dynamics (3309);
- 4215 Climate and interannual variability (3309);
- 4267 Paleoceanography;
- 4283 Water masses;
- 9340 Indian Ocean