Deciphering Changes in Atmospheric Nitrous Oxide Concentration During the Last Ice Age Using the Intramolecular Site-Preference of Nitrogen Isotopes

利用氮同位素的分子内位点偏好破译最后一个冰河时期大气一氧化二氮浓度的变化

• 批准号: 1903681
• 负责人: Edward Brook
• 金额: $ 40万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-15 至 2024-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1903681&HistoricalAwards=false
• 关键词: Deciphering; Changes; Atmospheric; Nitrous; Oxide

The objective of this project is to understand why the nitrous oxide (N2O) content of the atmosphere was lower during the last ice age (about 20,000-100,000 years ago) than in the subsequent warm period (10,000 years ago to present) and why it fluctuated during climate changes within the ice age. Nitrous oxide is a greenhouse gas that contributes to modern global warming. It is thought that modern warming will in turn cause increases in natural sources of nitrous oxide from bacteria in soils and the ocean, creating a "positive feedback." However, the amount these sources will increase is uncertain because the different ways that nitrous oxide are produced, and how sensitive they are to warmer climate, are not well known. This project will measure a unique property of the nitrous oxide molecule in very large ancient air samples from a glacier in Antarctica. This method can distinguish between different microbial processes that produce nitrous oxide but it has not been applied yet to the time periods in question. The data will provide information about how natural climate changes affect nitrous oxide production. This, in turn, will be useful for predicting future changes and for understanding why the Earth's climate shifts from ice ages to warm periods and back again. Ice-core records of greenhouse gas isotopic composition are useful for determining past changes in natural source and sink strengths and for understanding how natural emissions are linked to climate change. This project will develop two records of the intramolecular site preference of Nitrogen-15 in N2O. One record spans the last deglaciation (10,000-21,000 years ago) when atmospheric N2O concentration rose by 30 percent, and the other record spans millennial-scale climate changes during the last ice age when N2O varied by smaller amounts (Heinrich Stadial 4 and Dansgaard Oeschger 8, 35,000-41,000 years ago). The records will be used to understand what changes in the nitrogen cycle caused atmospheric N2O concentration to vary and what mechanisms link the N2O emissions to climate change. Ideally, studying the two different time periods will isolate the millennial climate responses entangled with the full deglacial sequence, creating a clearer picture of how N2O biogeochemistry responds to climate change. This work will also allow exploration of an isotopic tracer for in situ production of N2O that contaminates the atmospheric signal in particularly dusty ice. The project will use a unique, well-dated suite of ice samples from Taylor Glacier, Antarctica and continuous flow isotope ratio mass spectrometry on a custom gas extraction line operated in the Oregon State University laboratory.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.

该项目的目的是了解为什么大气中的一氧化二氮（N2O）含量在最后一个冰河期（大约2万至10万年前）比随后的温暖期（1万年前至今）要低，以及为什么它在冰河期的气候变化期间波动。一氧化二氮是导致现代全球变暖的温室气体。据认为，现代气候变暖反过来又会导致土壤和海洋中细菌产生的氧化亚氮的自然来源增加，从而产生“正反馈”。然而，这些来源增加的数量尚不确定，因为产生一氧化二氮的不同方式以及它们对气候变暖的敏感程度尚不为人所知。这个项目将测量一氧化二氮分子的独特性质，这些氧化二氮分子来自南极洲冰川的非常大的古代空气样本。这种方法可以区分产生氧化亚氮的不同微生物过程，但尚未应用于所讨论的时间段。这些数据将提供有关自然气候变化如何影响一氧化二氮生产的信息。反过来，这将有助于预测未来的变化，并有助于理解地球气候为什么会从冰河期转变为温暖期，然后又转变为温暖期。温室气体同位素组成的冰芯记录有助于确定过去自然源和汇强度的变化，并有助于了解自然排放与气候变化之间的关系。本项目将建立n2 -15在N2O中的分子内位点偏好的两个记录。一个记录跨越了最后一次冰期（10,000-21,000年前），当时大气中N2O浓度上升了30%，另一个记录跨越了最后一个冰期的千年尺度气候变化，当时N2O的变化幅度较小（Heinrich Stadial 4和Dansgaard Oeschger 8, 35,000-41,000年前）。这些记录将用于了解氮循环中的哪些变化导致了大气中一氧化二氮浓度的变化，以及将二氧化二氮排放与气候变化联系起来的机制。理想情况下，研究这两个不同的时间段将把千年气候反应与整个冰川消融序列相分离，从而更清楚地了解N2O生物地球化学如何响应气候变化。这项工作还将允许探索一种同位素示踪剂，用于现场生产N2O，这种N2O会污染特别是多尘冰中的大气信号。该项目将使用来自南极洲泰勒冰川的一套独特的、年代准确的冰样本，并在俄勒冈州立大学实验室的定制气体提取线上使用连续流同位素比质谱法。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。

项目成果

Millennial‐Scale Changes in Terrestrial and Marine Nitrous Oxide Emissions at the Onset and Termination of Marine Isotope Stage 4

海洋同位素第四阶段开始和结束时陆地和海洋一氧化二氮排放的千禧年规模变化

• DOI: 10.1029/2020gl089110
• 发表时间: 2020
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Menking, J. A.;Brook, E. J.;Schilt, A.;Shackleton, S.;Dyonisius, M.;Severinghaus, J. P.;Petrenko, V. V.
• 通讯作者: Petrenko, V. V.