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Holocene variations of thermocline conditions in the eastern tropical Indian Ocean
Stockholm University, Faculty of Science, Department of Meteorology . University of Bremen, Germany.
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2015 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 114, 33-42 p.Article in journal (Refereed) Published
Abstract [en]

Climate phenomena like the monsoon system, El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are interconnected via various feedback mechanisms and control the climate of the Indian Ocean and its surrounding continents on various timescales. The eastern tropical Indian Ocean is a key area for the interplay of these phenomena and for reconstructing their past changes and forcing mechanisms. Here we present records of upper ocean thermal gradient, thermocline temperatures (TT) and relative abundances of planktic foraminifera in core SO 189-39KL taken off western Sumatra (0 degrees 47.400' S, 99 degrees 54.510' E) for the last 8 ka that we use as proxies for changes in upper ocean structure. The records suggest a deeper thermocline between 8 ka and ca 3 ka compared to the late Holocene. We find a shoaling of the thermocline after 3 ka, most likely indicating an increased occurrence of upwelling during the late Holocene compared to the mid-Holocene which might represent changes in the IOD-like mean state of the Indian Ocean with a more negative IOD-like mean state during the mid-Holocene and a more positive IOD-like mean state during the past 3 ka. This interpretation is supported by a transient Holocene climate model simulation in which an IOD-like mode is identified that involves an insolation-forced long-term trend of increasing anomalous surface easterlies over the equatorial eastern Indian Ocean.

Place, publisher, year, edition, pages
2015. Vol. 114, 33-42 p.
Keyword [en]
Indian Ocean, Sumatra, Indian Ocean Dipole, Mg/Ca, Thermocline, Holocene, Planktic foraminifera
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-117453DOI: 10.1016/j.quascirev.2015.01.028ISI: 000353090000003OAI: diva2:812547


Available from: 2015-05-19 Created: 2015-05-19 Last updated: 2015-05-19Bibliographically approved

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Varma, Vidya
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