Evolution of South Pacific Oxygen and Preformed Nutrient Changes over the Deglaciation

深海中的氧气浓度，结合对营养物质和海水温度的测量，为了解海洋中碳的循环和大气中二氧化碳的含量提供了强有力的约束。这项研究使用深海沉积物岩心作为自上一个冰河时代以来这些关键环境变量变化的记录者，这一时期包含了地球气候系统的根本转变。资金支持培训一名研究生，以及一名K-12教师和她的两名高中生。培训活动还将包括代表人数不足但对海洋科学表现出兴趣的群体成员的参与。这些数据将提供给社区，并将对那些寻求了解海洋中碳循环的人产生广泛的兴趣。更具体地说，本研究将进一步发展一种有前景的深海氧气定量重建方法——底栖生物和深海有孔虫（Dd13C）碳同位素值的差异。利用这项技术，研究小组将生成过去25000年来南太平洋氧气浓度的记录。这一时期涵盖了一个主要的气候转变，即大气二氧化碳浓度从冰河时期的低水平上升到工业化前的较高水平。将使用相同的沉积物岩心估算底水磷酸盐（使用底栖有孔虫中的Cd/Ca）和底水温度（使用底栖有孔虫中的Mg/Ca和Li/Ca）。结合氧重建，磷酸盐和温度信息将用于估计深水离开地表区域的营养成分（预形成的营养成分）。氧气和预成型营养物质变化的时间和幅度将有助于了解海洋生物和环流的变化是如何促成上一个冰河期二氧化碳含量的降低的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Oxygen concentrations in the deep ocean, in combination with measurements of nutrients and seawater temperature, provide a powerful constraint for the understanding cycling of carbon in the ocean and the amount of atmospheric carbon dioxide. This research uses deep sea sediment cores as recorders of changes in these key environmental variables since the peak of the last ice age, a period encompassing a fundamental shift in the Earth's climate system. Funding supports training of a graduate student, along with a K-12 teacher and two of her high school students. The training activities will also include the participation of members of under-represented groups who have demonstrated interest in the Ocean Sciences. The data will be made available to the community and will be of broad interest to those seeking to understand the cycling of carbon in the ocean.More specifically, this research will further develop a promising method for the quantitative reconstruction of oxygen in the deep ocean-- the difference between carbon isotope values of epibenthic and deep infaunal foraminifera (Dd13C). Using this technique, the research team will generate records of oxygen concentrations in the South Pacific over the last 25,000 years. This time period covers a major climatic transition when atmospheric carbon dioxide concentrations rose from the low levels of glacial times to the higher values of the pre-industrial present. Estimates bottom water phosphate (using Cd/Ca in benthic foraminifera) and bottom water temperature (using Mg/Ca and Li/Ca in benthic foraminifera) will be made using in the same sediment cores. Combined with the oxygen reconstructions, phosphate and temperature information will be used to estimate the nutrient content in the regions where the deep water left the surface (preformed nutrients). The timing and magnitude of the changes in oxygen and preformed nutrients will help to understand how changes in ocean biology and circulation contributed to the lowering in carbon dioxide during the last ice age.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.