Seawater Calcium Isotopes and the Oceanic Ca Cycle

钙是海水中主要的溶解物质，在海水中的停留时间约为一百万年。它的来源包括河流和热液流体，以及少量的沉积成岩作用。钙还通过海洋中的碳酸盐沉淀与碳循环联系在一起。该项目提出，对当今钙源和钙汇中钙同位素变化的详细测量，将有助于揭示海洋钙循环的细节。这样的数据可以用来解释过去钙同位素丰度的变化，这最终将与气候变率和全球碳酸盐保存和温度波动的变化有关。PI已经证明了以研究钙循环所必需的高精度进行这些独特测量的能力，他建议在现有的河水、热液流体、海洋沉积物和玄武岩样品中进行新的测量。这些数据与现有的海水结果一起，将为我们对海洋钙循环的理解提供重大进展。

Calcium is a major dissolved species in seawater with a residence time of about a million years. Its sources include rivers and hydrothermal fluids, as well as small amounts via sediment diagenesis. Ca is also tied to the carbon cycle via carbonate precipitation in the oceans. The PI proposes that detailed measurements of Ca isotopic variations in present day Ca sources and sinks will shed light on the details of the oceanic Ca cycle. Such data could then be used to interpret past changes in Ca isotopic abundances, which would ultimately be related to climatic variability and changes in global carbonate preservation and temperature fluctuations. The PI has demonstrated the ability to make these unique measurements with the high precision necessary to study Ca cycling, and he proposes to make new measurements in existing samples of river water, hydrothermal fluids and marine sediments and basalts. These data, together with existing seawater results, would provide a signifcant advance in our understanding of the oceanic Ca cycle.