Collaborative Research: Taking the reliability of Cenozoic boron isotope pH and pCO2 reconstructions to the next level

合作研究：将新生代硼同位素 pH 和 pCO2 重建的可靠性提升到新的水平

• 批准号: 1658024
• 负责人: Andrew Ridgwell
• 金额: $ 17.9万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2021-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658024&HistoricalAwards=false
• 关键词: Collaborative; Research; Taking; reliability; Cenozoic

If anthropogenic carbon dioxide (CO2) emissions continue to increase unabated, the continued accumulation of this gas in the atmosphere will warm Earth's climate via the greenhouse effect, while the dissolution of CO2 in the surface ocean makes seawater more acidic. Although historical CO2 levels and global warming are reasonably well documented for the past few decades, scientists' understanding of climate and particularly ecosystem sensitivity to much higher CO2 levels is limited and greatly impedes accurate projections of future changes. Earth history can aide scientists in improving their understanding, by providing much longer geological records of variations in past seawater chemistry and their associated ecological responses, if any. This research aims to provide fundamental constraints on surface ocean acidity and atmospheric CO2 levels throughout the past 65 million years, when a number of climate shifts containing important information about oceanic and atmospheric chemical changes occurred. The research will combine surface ocean acidity reconstructions from geochemical information stored in the fossil shells of plankton organisms, as well as computer model simulations of ocean carbon chemistry. In addition to informing scientists and policy makers about the impact of rising atmospheric CO2 levels on global climate, the outcomes of this study are also of great value to paleoecologists, who want to understand the effect of ocean acidification on marine life. The study will support the research of two graduate students at Columbia University and University of California at Riverside, and will provide training in carbon cycle modeling to interested researchers .Specifically, the project will measure the boron isotopic composition (delta11B) recorded in fossil foraminifera shells to reconstruct past seawater-pH and, by inference, atmospheric CO2 levels. Earlier studies using this approach have only been able to reconstruct relative shifts in seawater-pH and atmospheric CO2, because slight differences in the delta11B recorded by individual foraminifera species complicate the application of this proxy to the distant past, as most ancient foraminifera species are now extinct. In addition, a second parameter (e.g., alkalinity) of the marine carbonate system is needed to accurately calculate atmospheric CO2 levels from surface ocean chemistry records, but researchers have not yet found a reliable geochemical indicator for alkalinity in ocean sediments. This research aims to overcome these limitations, by (1) cross-calibrating modern and extinct planktic foraminifera species, (2) refining Earth system model estimates of surface ocean alkalinity, and (3) deriving a refined and self-consistent reconstruction of Cenozoic pCO2 from boron isotopes and modeled alkalinity. In addition to the low resolution 65-million year paleoreconstruction anticipated by this study, the cross-calibration of vital effects on foraminiferal delta11B and improved alkalinity estimates from geochemical modeling will facilitate future studies of absolute rather than relative pH and pCO2 in the past.

如果人为二氧化碳（CO2）的排放量继续增加，则这种气体在大气中的持续积累将通过温室效应加热地球的气候，而二氧化碳在地面海洋中的溶解使海水更具酸性。尽管在过去的几十年中，历史二氧化碳水平和全球变暖已经得到充分记录，但科学家对气候，尤其是对更高二氧化碳水平的生态系统敏感性的理解是有限的，并且极大地阻碍了未来变化的准确预测。地球历史可以通过为过去的海水化学及其相关的生态反应（如果有）提供更长的地质记录来帮助提高他们的理解。这项研究旨在在过去6500万年中对表面海洋酸度和大气二氧化碳水平的基本限制，当时发生了许多气候变化，其中包含有关海洋和大气化学变化的重要信息。该研究将从浮游生物的化石壳中存储的地球化学信息以及海洋碳化学模型模拟结合表面海洋酸度重建。除了向科学家和决策者告知大气二氧化碳水平上升对全球气候的影响外，这项研究的结果对古生物学家也具有巨大的价值，他们想了解海洋酸化对海洋生物的影响。该研究将支持哥伦比亚大学和加利福尼亚大学河滨分校的两名研究生的研究，并将为感兴趣的研究人员提供碳循环建模的培训。特别是，该项目将测量在化石有孔虫壳中记录的硼同位素组合（Delta11b），以重建过去的Seawater-Pher-Pher-ph和Bycernperconternecrencect，Airmentercy Co2级别。使用这种方法的早期研究仅能够重建海水和大气二氧化碳的相对变化，因为单个有孔虫物种记录的三角洲11b的微微差异使该代理在遥远的过去的应用变得复杂，因为大多数古老的有孔虫物种现在都是灭绝的。此外，需要使用海洋碳酸盐系统的第二个参数（例如，碱度）来准确地从表面海洋化学记录中计算大气中的二氧化碳水平，但是研究人员尚未发现海洋沉积物中碱度的可靠地球化学指标。这项研究旨在通过（1）跨校准现代和灭绝的浮游有孔虫物种来克服这些局限性，（2）改进地球系统模型的表面海洋碱度的估计以及（3）从Boron isotopes和模型的烷气中得出了精致且自持式PCO2的精致且自持一致的重建。除了这项研究预期的6500万年的古分辨率低分子外，对有孔虫的三角洲12B的重要影响以及地球化学建模的碱度估计值的改进还将促进过去的绝对性研究，而不是过去的相对pH和PCO2。

项目成果

A 35-million-year record of seawater stable Sr isotopes reveals a fluctuating global carbon cycle

• DOI: 10.1126/science.aaz9266
• 发表时间: 2021-03
• 期刊: Science
• 影响因子: 56.9
• 作者: A. Paytan;E. Griffith;A. Eisenhauer;M. Hain;K. Wallmann;A. Ridgwell

Early Cenozoic Decoupling of Climate and Carbonate Compensation Depth Trends

• DOI: 10.1029/2019pa003601
• 发表时间: 2019-06-01
• 期刊: PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
• 影响因子: 3.5
• 作者: Greene, S. E.;Ridgwell, A.;Hoogakker, A. A.
• 通讯作者: Hoogakker, A. A.

Inclusion of a suite of weathering tracers in the cGENIE Earth system model – muffin release v.0.9.23

• DOI: 10.5194/gmd-14-4187-2021
• 发表时间: 2021-07
• 期刊: Geoscientific Model Development
• 影响因子: 5.1
• 作者: Markus Adloff;A. Ridgwell;F. Monteiro;I. Parkinson;A. Dickson;Philip A. E. Pogge von Strandmann;M. Fantle;S. Greene

Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record

了解与岩石记录中海洋酸化和碱度超调相关的 Ca 同位素信号

• DOI: 10.1016/j.chemgeo.2020.119672
• 发表时间: 2020
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Fantle, Matthew S.;Ridgwell, Andy
• 通讯作者: Ridgwell, Andy