Collaborative Research: Uncovering marine carbon chemistry dynamics during the deglaciation with boron isotopes and radiocarbon

合作研究：用硼同位素和放射性碳揭示冰消过程中的海洋碳化学动力学

• 批准号: 2032340
• 负责人: Patrick Rafter
• 金额: $ 8万
• 依托单位: University of California-Irvine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2032340&HistoricalAwards=false
• 关键词: Collaborative; Research; Uncovering; marine; carbon

The global carbon cycle underwent a major transition at the end of the last ice age ~12,000 years ago – atmospheric carbon dioxide levels rose abruptly at that time. This project will use naturally-occurring “radiocarbon” (the radioactive carbon isotope 14C) to study how global carbon pools changed during that deglacial transition. The project will test previous radiocarbon evidence for a pulse of carbon release from seafloor volcanoes in the eastern Pacific Ocean at that time. That result challenges the idea that carbon release from the solid Earth is relatively slow and steady. Chemical and isotope measurements on fossil shells from deep-sea sediment cores will show whether the carbon pulse came in the form of acid or base. This will help pin down the source of the carbon. Carbon cycle models will be used to estimate the scale of these carbon pulses and their impact on ocean acidity and atmospheric carbon dioxide levels. Preliminary data and initial model results suggest that the carbon source was acid/base neutral. If so, then enormous quantities of carbon could have been released without causing strong ocean acidification or a strong atmospheric carbon dioxide rise. Carbon dioxide is a greenhouse gas and human activities are responsible for a large release of carbon dioxide today. Documenting the scale and nature of the natural carbon release at the end of the last ice age will help predict the environmental consequences of human carbon release. It will also help predict whether the human carbon release may be neutralized by natural processes.The Gulf of California study site was selected because it contains: (1) a high-quality wood fragment-based chronology, (2) abundant and well-preserved benthic foraminifera for boron and carbon isotope analysis, (3) replicated evidence for regionally and temporally coherent 14C anomalies, and (4) known local sources of geologic carbon associated with the East Pacific Rise. The main thrust of the proposed work comes from d11B and B/Ca measurements to establish if there was any seawater carbonate chemistry and/or pH change associated with the 14C anomalies, but the proposed work also includes a wider set of complementary isotope geochemical measurements (14C/C, d13C) to enhance the value of the database as a constraint on the possible explanations for the regional 14C anomalies. The project also includes regional and global carbon cycle modeling to assimilate the multi-proxy constraints and quantitatively assess the implied effects on global seawater carbon chemistry and atmospheric CO2. This work will inform the active debate about the contribution of deglacial carbon release to deglacial CO2 rise. The working hypothesis is that significant pulses of geologic carbon releases explain the observed 14C anomalies but would not significantly contribute to CO2 change because that carbon came in neutralized bicarbonate ion form. Overall, the study will take on a significant gap in understanding natural carbon cycle change on human-relevant timescales by collaboratively integrating novel multi-proxy measurements with carbon cycle modeling. Both PIs are early career scientists with demonstrated domain expertise and track record.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.

在最后一个冰河时代结束时，全球碳循环大约12，000年前 - 当时大气中的二氧化碳水平突然上升。该项目将使用自然存在的“放射性碳”（放射性碳同位素14C）来研究全球碳池在该冰冰过渡过程中的变化。该项目将测试先前的放射性碳证据，以证明当时东太平洋从海底火山从海底火山释放碳脉冲。这一结果挑战了从固体地球释放碳相对较慢和稳定的观念。深海沉积物芯上的化石壳上的化学和同位素测量将显示碳脉冲是以酸还是碱的形式出现。这将有助于固定碳的来源。碳循环模型将用于估计这些碳脉冲的规模及其对海洋酸度和大气二氧化碳水平的影响。初步数据和初始模型结果表明碳源是酸/碱中性的。如果是这样，则可以释放出增强的碳，而不会引起强大的海洋酸化或强烈的大气二氧化碳升高。二氧化碳是一种温室气体，人类活动负责今天大量二氧化碳释放。记录上一个冰河时代结束时天然碳释放的规模和性质将有助于预测人类碳释放的环境后果。它还将有助于预测人类碳释放是否可能被自然过程中和。选择加利福尼亚研究地点，因为它包含：（1）基于木材碎片的高质量碎片年表，（2）丰富且保存良好的底栖有孔虫，用于硼龙和碳同位素分析和碳同位素分析，（3）的区域性循环（3），（3）是一个已知的CORISICES和PEREMISISINIS CORISEIS（4）。与东太平洋崛起有关的碳。拟议工作的主要力量来自D11B和B/CA测量值，以确定是否存在与14C异常相关的任何海水碳酸盐化学和/或pH变化，但是拟议的工作还包括一组更广泛的同位素地球地球化学测量值（14c/c，d13c），以增强该数据的价值，以增强该数据的构成，以示例为一定的数据汇总。该项目还包括区域和全球碳循环建模，以吸收多核约束，并定量评估对全球海水碳化学和大气二氧化碳的隐含影响。这项工作将为关于冰流碳释放对冰流二氧化碳升高的贡献的积极辩论提供信息。工作假设是，地质碳释放的显着脉冲解释了观察到的14C异常，但不会显着导致二氧化碳变化，因为该碳是中和碳酸氢盐离子形式的。总体而言，这项研究将通过将新型的多核测量结果与碳循环建模相结合，从而在理解人类相关时间表的自然碳循环变化方面存在很大的差距。这两个PI都是具有展示领域专业知识和往绩记录的早期职业科学家。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响评估标准来评估值得支持。

项目成果

Constraining Earth’s geologic influence on the global carbon cycle during the last ice age from the planetary radiocarbon budget

从行星放射性碳预算中限制上一个冰河时期地球地质对全球碳循环的影响

• DOI: 10.7185/gold2021.8208
• 发表时间: 2021
• 期刊: Constraining Earth’s geologic influence on the global carbon cycle during the last ice age from the planetary radiocarbon budget
• 作者: Green, Ryan;Hain, Mathis;Rafter, Patrick
• 通讯作者: Rafter, Patrick

OS13A-04 - Interconnected global deep-sea circulation changes over the past 25,000 years

OS13A-04 - 过去 25,000 年来相互关联的全球深海环流变化

• 发表时间: 2021
• 期刊: AGU Fall Meeting
• 作者: Rafter, Gray

OS33A-04 - Global reorganization of deep-sea circulation and carbon storage after the last ice age

OS33A-04 - 最后一个冰河时代后全球深海循环和碳储存的重组

• 发表时间: 2022
• 期刊: AGU Fall Meeting
• 作者: PA Rafter, WR Gray

New measurements and compilation provide a 25,000 year view of global deep-sea radiocarbon

新的测量和汇编提供了 25,000 年全球深海放射性碳的视图

• DOI: 10.7185/gold2021.6487
• 发表时间: 2021
• 期刊: New measurements and compilation provide a 25,000 year view of global deep-sea radiocarbon
• 作者: Rafter, Patrick;Costa, Kassandra;Hines, Sophia;Devries, Timothy;Rae, James;Gray, William;Burke, Andrea;Southon, John;Gottschalk, Julia;Hain, Mathis
• 通讯作者: Hain, Mathis

PP12B-05 and CO2 14C - Constraints on the Deglacial Release of Geologic Carbon Using Atmospheric Records

PP12B-05 和 CO2 14C - 使用大气记录限制冰期地质碳释放

• 发表时间: 2021
• 期刊: AGU Fall Meeting
• 作者: RYAN GREEN, MATHIS HAIN