FP 08: Evaluation of the Ca Isotope System in Carbonate Polymorphs as a new Proxy for Seawater Temperature and Secular Variations of Ca Conventration and Fractionation throughout Earth History

我们建议研究碳酸钙生物矿化和无机沉淀过程中钙（Ca）同位素分馏（<$44Ca）的热力学和古海洋学原理。这一点很重要，因为最近的研究结果表明，钙同位素系统代表了重建过去海水温度和地球历史上钙海水浓度变化的新代理。这两个方面对于古海洋学和气候学都是至关重要的，因为它们干扰了全球碳循环，影响了重要的温室气体如CO2的浓度。验证钙同位素作为古代用指标的概念是测试其温度校准的灵敏度，原始同位素信号的保存，种间差异和过去的初始同位素比值的知识。这些要求将在实验室和培养实验中对无机沉淀的CaCO 3和以前用作代理档案的海洋钙化生物的主要群体进行研究。建议的实验交叉校准的钙同位素系统的温度敏感的金属钙比…和其他同位素系统将通过现场和地下实验来完成，提供独特的机会来完善其作为多代理方法中的古代理的应用。

We propose the investigation of the thermodynamic and paleooceanographic principles of calcium (Ca) isotope fractionation (¿ 44Ca) during biomineralization and inorganic preciptation of calcium carbonate... This is important because recent findings indicate that the Ca isotope system represents a new proxy for the reconstruction of past seawater temperatures and for variations of the Ca seawater concentrations throughout Earth¿s history. Both aspects are crucial for paleooceanography and -climatology because they interfere with the global carbon cycle influencing the concentration of important greenhouse gases likes C02 throughout time. The concept to validate the Ca isotopes as a paleo-proxy is to test its sensitivity of temperature calibration, the preservation of primary isotope signals, the knowledge of inter-specific differences and of past initial isotope ratios. These requirements will be investigated in laboratory and culturing experiments on inorganically precipitaled CaC03 and on major groups of marine calcifying organisms previously used as proxy archives... The proposed experimental cross-calibration of the Ca isotope system to temperature sensitive metal to calcium ratios... and other isotope systems... will be completed by field and down-core experiments offering the unique opportunity to refine their application as paleo-proxies in a multi-proxy approach.