用南海沉积物中长链烯酮重建中新世大气二氧化碳浓度变化

本项目将以中新世大气二氧化碳浓度变化为核心内容与科学问题，以南海大洋钻探IODP368航次U1501站中新世沉积样品为研究材料，以长链烯酮碳同位素分析为主要方法，重建中新世连续的、较高分辨率的南海海水及大气二氧化碳浓度变化。同时，对南海中新世古海洋、古气候变化如表层海水古温度、古生产力、碳循环和海平面变化进行研究。在此基础上，结合已有全球中新世古气候变化资料，探索二氧化碳在中新世古气候演变中的作用，并特别关注中新世13.9Ma大洋碳储库改组事件与大气二氧化碳之间的关系。此外，本项目还通过颗石形态测量等方法对南海中新世颗石藻钙化作用进行研究，并与海水二氧化碳浓度及其它海水碳酸盐系统参数相联系，探讨颗石藻钙化作用对海水碳酸盐系统的响应。

This project aims to reconstruct the Miocene atmospheric CO2 concentrations based on the carbon isotope of alkenone from the sediments of IODP Site U1501 of the South China Sea. The Miocene palaeoceanography and palaeoclimatology such as SST, palaeoprodutivity, carbon cycle and sea level will be also studied by quantitative coccolith analysis, coccolith and foramiferal carbon and oxygem analysis and TEX 86. And then, we will explore the relationship between the atmospheric CO2 concentrations and the climatology,especially on the 13.9Ma Middle Miocene climatic transition event. The Miocene coccolithophre calcification and their respnse to ocean carbonate chemistry will be studied by measuring the coccolith size,thickness,mass, calcification rate, cell-specific calcification rate etc. In this project, we try to introduce a new method, using coccolithophore physiology to calibrate the b value. Coccolithophore physiology (calcification and photosynthesis) can be represented by coccolith isotopes and morphology, which can be used to constrain b value directly. This new method can make the CO2 paleobarometer tool more reliable, and provide powerful proofs in exploring the CO2 variation during the Miocene in the South China Sea.