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Modern and past processes of ocean-atmosphere-climate interactions in the low-latitude western Pacific and Indian Ocean
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Glacial-interglacial variations in opal and organic carbon accumulation in the eastern equatorial Indian Ocean
Wednesday 9th @ 1450-1510, Conference Room 1
Selvaraj Kandasamy* , Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Peng Yang, Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Cheng Jin, Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Zhiqiang Wang, Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Huawei Wang, Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Qianqian Liu, State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, PR China
Stephan Steinke, Department of Geological Oceanography, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, PR China
Mahyar Mohtadi, Center for Marine Environmental Sciences (MARUM), University of Bremen, Germany
Presenter Email: selvaraj@xmu.edu.cn |
| Marine silica cycle has a tight link with the carbon cycle on glacial-interglacial timescales along the coastal and equatorial upwelling regions and other high productivity areas. Estimation of carbon burial in the eastern equatorial Indian Ocean, in particular areas off Sumatra and Java, has been suggested to hold between 0.1% and 7.1% of the global annual carbon burial. Nonetheless, the role of biogenic silica productivity/ burial and its relation to carbon burial on glacial-interglacial timescales in this region are unknown. Here we investigate opal and total organic carbon (TOC) contents in two, radiocarbon-dated sediment cores (GeoB-10029-4 and GeoB-10038-4) from the eastern equatorial Indian Ocean to understand the link between their accumulation rates and mechanisms responsible for their variations over the past ~40 thousand years (kyr). Both opal and TOC contents were roughly two times higher in core GeoB-10029-4 than in core GeoB-10038-4, though the location of the former is not affected by the seasonal upwelling at present, indicating that the monsoon-induced seasonal upwelling may not be the main driver of opal and organic matter accumulation in this area. Low opal and TOC values during the glacial period than the deglacial and Holocene intervals were however consistent with high productivity during the warm interglacials. Our records show increased and decreased diatom productivity during Last Glacial Maximum (LGM) and deglacial intervals, respectively, suggesting a strong sea level control over the preservation of opal and organic matter in the study area. Consistently, atomic Si/C ratios were more or less similar in sediments accumulated during glacial and Holocene intervals in both cores, but these ratios were relatively higher in sediments deposited during the LGM and deglacial intervals, especially at the non-upwelling location, implying a better preservation and/or weaker dissolution of opal when the core location became an enclosed basin during these intervals due to low and increased sea level. Overall, opal accumulation rates were higher than TOC since the LGM at the non-upwelling site, whereas an opposite trend between their accumulation rates was mostly evident at the upwelling site for the last ~40 kyr. This study will therefore address the mechanisms for the differential burial and behavior of opal and organic carbon on glacial-interglacial timescales between these two hydrographically dissimilar sites. |
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