Collaborative Research: Deep ocean temperature and continental ice volume from benthic foraminiferal test composition, 77Ma to Present

合作研究：来自底栖有孔虫测试组合物的深海温度和大陆冰量，77Ma 至今

• 批准号: 2148461
• 负责人: Chiara Borrelli
• 金额: $ 38.46万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2148461&HistoricalAwards=false
• 关键词: Collaborative; Research; Deep; ocean; temperature

Sea floor sediments record the natural variability of the Earth’s climate system. Studying sediment records can improve our ability to predict how the climate system will respond to human activities. This project will produce records of deep-sea temperatures, continental ice volume, and atmospheric carbon dioxide. The records will document changes in the climate system over the last 77 million years. Those data will improve our understanding of processes such as polar amplification and the ability of the Earth’s system to adjust to different atmospheric carbon dioxide concentrations. This study will also improve our knowledge of long-term changes in deep ocean temperatures and ice-sheet volume variability and their connection to changes in atmospheric carbon dioxide. The project will be carried out by two female scientists, one of whom is an early career researcher. Several undergraduate and graduate students will participate to the proposed research activities. The outreach program will involve Earth/Environmental Science teachers from middle and high schools. Benthic foraminifera are excellent recorders of past environmental conditions. In particular, the benthic foraminiferal (bf) magnesium/calcium ratio (Mg/Ca) is used as a temperature proxy, making it possible to separate temperature from ice volume effects on the widely used bf oxygen isotope proxy (d18O). However, the bf Mg/Ca signal is complicated by a dependency on carbonate saturation state (“omega”) in addition to temperature. Benthic foraminiferal lithium, boron and strontium to calcium ratios (Li-B-Sr/Ca) show promise in separating the temperature and omega contributions to bf Mg/Ca. The proposed research will: 1) construct robust temperature and ice volume histories during the late Cretaceous and Cenozoic (~77-0 Ma) using bf d18O in conjunction with bf Mg-Li-B-Sr/Ca; and 2) calibrate offsets in bf Mg-Li-B-Sr/Ca for multiple species across paleodepth transects to encompass a range of omega. Different species’ physiological response to variations in temperature, omega, and seawater element/Ca ratios will be addressed using a multivariate model. One-Myr sample spacing will be used for the calibrations, whereas a new higher-resolution (~200 Kyr) record will provide a robust dataset of bf Mg/Ca variations since 77 Ma. This dataset will be used, together with bf d18O data, to test the hypothesis that deep ocean temperature and continental ice volume covary from the Late Cretaceous to the Cenozoic. The connections among changes in deep ocean temperature (and chemistry), continental ice volume, and atmospheric carbon dioxide concentration will be investigated using a numerical box model of the ocean carbon cycle.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.

海底沉积物记录了地球气候系统的自然变化。研究沉积物记录可以提高我们预测气候系统如何响应人类活动的能力。该项目将记录深海温度、大陆冰量和大气二氧化碳。这些记录将记录过去 7700 万年气候系统的变化。这些数据将提高我们对极性放大等过程的理解，以及地球系统适应不同大气二氧化碳浓度的能力。这项研究还将提高我们对深海温度和冰盖体积变化的长期变化及其与大气二氧化碳变化的关系的了解。该项目将由两名女科学家执行，其中一名是早期职业研究员。一些本科生和研究生将参加拟议的研究活动。外展计划将涉及初中和高中的地球/环境科学教师。底栖有孔虫是过去环境条件的优秀记录者。特别是，底栖有孔虫 (bf) 镁/钙比 (Mg/Ca) 用作温度代理，使得可以将温度与冰体积对广泛使用的 bf 氧同位素代理 (d18O) 的影响分开。然而，bf Mg/Ca 信号由于除了温度之外还依赖于碳酸盐饱和状态（“omega”）而变得复杂。底栖有孔虫锂、硼和锶与钙的比率 (Li-B-Sr/Ca) 在分离温度和 omega 对 bf Mg/Ca 的贡献方面表现出良好的前景。拟议的研究将：1）使用bf d18O与bf Mg-Li-B-Sr/Ca结合构建白垩纪晚期和新生代（~77-0 Ma）期间稳健的温度和冰体积历史； 2) 校准古深度断面多个物种的 bf Mg-Li-B-Sr/Ca 偏移量，以涵盖一系列 omega。不同物种对温度、欧米伽和海水元素/钙比率变化的生理反应将使用多元模型来解决。校准将使用 1 Myr 样本间距，而新的更高分辨率（~200 Kyr）记录将提供自 77 Ma 以来 bf Mg/Ca 变化的可靠数据集。该数据集将与 bf d18O 数据一起用于检验深海温度和大陆冰体积从白垩纪晚期到新生代共变的假设。将使用海洋碳循环的数值盒模型来研究深海温度（和化学）、大陆冰量和大气二氧化碳浓度变化之间的联系。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。