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Marine Carbon Sequestration (MARCO): Multiscale Regulation and Response to Global Change
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Carbon burial in the northern South China Sea in response to climate change and ocean acidification since the last 2 ka
P-SPS5-13 Gangjian Wei* , Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Zhonghui Liu, Department of Earth Science, the University of Hong Kong Wenfeng Deng, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Feng Ye, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Presenter Email: gjwei@gig.ac.cn |
Our researches focus on reconstructions of the high-resolution records of paleoclimate (such as temperature, pH) and carbon burial in the northern South China Sea over the last 2 millennia based on multiple geochemical proxies, aiming to elucidate the response of carbon burial to climate change and ocean acidification. The main findings are as follows: (1) Our paired Sr/Ca and δ18O records in the corals from the northern SCS revealed that the climate of the Medieval Climate Anomaly (AD 900-1300) was similar to that of the Current Warm Period (AD 1850-present), suggesting that anthropogenic influences on SST warming are not significant in tropical marine systems (Deng et al., 2017; Xiao et al., 2017). Meanwhile, the long-chain alkenones records in the high-resolution offshore sediment cores showed that the SST variation in the marginal seas over the last 2 millennia matches or opposites to that of the global/northern hemisphere temperature changes, which is governed by changes in the Asian summer/winter monsoon and oceanic circulation (Kong et al., 2017; Liu et al., 2018). (2) The coral δ13C and δ11B records in the northern SCS indicated that the carbon source utilized for calcification is strongly influenced by atmospheric CO2 while pH in calcification fluid began to decrease since the Industrial Era (Deng et al., 2017), demonstrating a very important role of anthropogenic factors on calcification or inorganic carbon burial on coral reefs. In addition, more metabolic carbon with more negative δ13C was preferentially utilized for coral calcification after three super El Niños (Wang et al., 2018). On the basis of a series of coral records in the SCS, we found that coral calcification generally showed an increasing trend over the past 200 years, which is probably due to the gradual rising of the SST after the Industrial Era, and the negative effect on coral calcification by ocean acidification induced by rising atmospheric CO2 appear to be concealed by SST rising. (3) Based on a more comprehensive suite of proxies such as GDGTs, the sources and compositions of surface sedimentary organic carbon (OC) are better constraint in the coastal systems of the northern SCS (Liao et al., 2018a, 2018b), which is crucial to more accurately describe how the carbon burial in response to changing climate. Multiple geochemical records in the coastal SCS demonstrated that organic carbon burial rates increased remarkably over the last millennium, as a result of the enhanced human activities (Huang et al., 2018). |
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