Thermocline temperature variability in the Timor Strait over the last two glacial cycles
Abstract
*Lo Giudice Cappelli, E elgc@gpi.uni-kiel.de Institute of Geosciences, Christian-Albrechts-University, Kiel, Germany Holbourn, A ah@gpi.uni-kiel.de Institute of Geosciences, Christian-Albrechts-University, Kiel, Germany Kuhnt, W wk@gpi.uni-kiel.de Institute of Geosciences, Christian-Albrechts-University, Kiel, Germany Regenberg, M regenberg@gpi.uni-kiel.de Institute of Geosciences, Christian-Albrechts-University, Kiel, Germany Garbe- Schönberg, D dgs@gpi.uni-kiel.de Institute of Geosciences, Christian-Albrechts-University, Kiel, Germany Seafloor temperature variations within the path of the Indonesian Throughflow are mainly influenced by the intensity of the cool throughflow and by glacial-interglacial sea-level changes. We present a study based on core 18471 (9°21.987' S, 129°58.983' E, 485m water depth, 13.5m long) and 30 core tops retrieved in the Timor Sea during the R/V Sonne Cruise 185 ("VITAL"). Multicorer core tops were retrieved along two transects between 130 and 2400m water depths, representing a range of present day bottom water temperatures between 2 and 21°C. For the downcore study, we measured Mg/Ca-ratios in ~10 tests of the benthic foraminifera Hoeglundina elegans, Cibicidoides wuellerstorfi and Hyalinea balthica in 10cm intervals (1-2kyr time resolution). The preservation of tests was checked with a scanning electron microscope. Cibicidoides wuellerstorfi and H. balthica were used in one interval, where H. elegans was rare. Duplicate samples were analyzed to inter-calibrate the three species. Mg/Ca ratios were converted into temperature using published calibrations and our regional calibration based on Timor Sea core tops. Preliminary results show that Mg/Ca ratios in H. elegans vary between 0.8 and 2.2mmol mol-1 corresponding to a temperature range between 4 and 10.5°C, in contrast to a modern annual average temperature of 7.9°C at 400m. 22-paired analyses in H. elegans give a reproducibility of 0.16mmol mol-1 (standard deviation), corresponding to a temperature difference of ±0.9°C. The amplitude of the temperature change during deglaciation is ~2°C between MIS2 and the Holocene and ~3°C between MIS6 and MIS5e. In contrast, the highest amplitude variability (~6.5°C) is detected during MIS3, suggesting transient shutdown of the Indonesian Throughflow leading to thermocline warming.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMPP41A1993L
- Keywords:
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- 4924 PALEOCEANOGRAPHY / Geochemical tracers;
- 4944 PALEOCEANOGRAPHY / Micropaleontology