Temperature-Dependent Ocean-Atmosphere Equilibration of Carbon Isotopes in Atlantic Thermocline and Surface Waters

碳的稳定同位素可以提供碳在地球系统中移动的过程的线索。佐治亚理工学院的研究人员将使用上层海洋中的碳同位素和营养物质重建，结合现有的从冰芯重建的大气碳同位素，以更好地了解上一个冰河时代结束时大气二氧化碳上升的原因和方式。这项工作将有助于进一步了解大气二氧化碳浓度的控制和反馈。还将探索从海-气碳同位素差异恢复过去表面海洋温度的可能性。研究人员将评估在北大西洋冰川消融期间看到的上层海洋碳同位素变化是否主要反映了生物循环或海气交换过程。从海底有孔虫的Cd/Ca测量中，将建立海水镉(Cd，与今天海洋中的营养磷酸盐有关)的详细记录。这些测量将有助于查明是什么机制导致了冰川消融期间向效率较低的生物碳泵的过渡。研究人员还将通过对大型浮游有孔虫的碳同位素测量，重建北大西洋平衡良好、低营养的地表水的碳同位素组成。这些水域的碳同位素比率将反映大气比率和平衡温度的变化，可能提供有关过去表层海洋温度变化的信息。除了更好地了解二氧化碳和气候之间的关系的社会相关性外，这笔赠款还将支持对来自代表性不足群体的几名学生的培训。这些数据将提供给社区，并将为合成和解释冰川消融期间的碳同位素记录的国际努力做出贡献。

The stable isotopes of carbon can provide clues about the processes by which carbon moves through the earth system. Researchers at Georgia Institute of Technology will use carbon isotope and nutrient reconstructions in the upper ocean, in combination with existing atmospheric carbon isotope reconstructions from ice cores, to better understand why and how atmospheric carbon dioxide rose at the end of the last ice age. This work will help further the understanding of the controls and feedbacks on atmospheric carbon dioxide concentrations. The possibility of reconstructing past surface ocean temperatures from the air-sea carbon isotope difference will also be explored. The investigators will assess whether the upper ocean carbon isotope changes seen over the deglaciation in the North Atlantic primarily reflect biological cycling or air sea exchange processes. A detailed record of seawater cadmium (Cd, related to the nutrient phosphate in today's ocean) from Cd/Ca measurements in benthic foraminifera will be constructed. These measurements will help to pinpoint what mechanism was responsible for the transition to a less efficient biological carbon pump over the deglaciation. The investigators will also reconstruct the carbon isotopic composition of well equilibrated, low nutrient surface waters in the North Atlantic using carbon isotopic measurements on large planktonic foraminifera. The carbon isotope ratio in these waters will reflect the changes in the atmospheric ratio and the temperature of equilibration, potentially providing information on past surface ocean temperature changes. In addition to the societal relevance of better understanding the relationship between carbon dioxide and climate, this grant will support the training of several students from under-represented groups. The data will be made available to the community and will be contributed to an international effort to synthesize and interpret carbon isotope records over the deglaciation.