Tracing Past Methane Variations with Stable Isotopes in Antarctic Ice Cores

用南极冰芯中的稳定同位素追踪过去的甲烷变化

• 批准号: 1745078
• 负责人: Edward Brook
• 金额: $ 48.94万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2023-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1745078&HistoricalAwards=false
• 关键词: Tracing; Past; Methane; Variations; Stable

This project will develop methods to measure the ratios of carbon-13 to carbon-12, and heavy to light hydrogen in methane in air trapped in ice cores. The ratios of the different forms of carbon and hydrogen are "fingerprints" of different sources of this gas in the past--for example wetlands in the tropics versus methane frozen in the sea floor. Once the analysis method is developed, the measurements will be used to examine why methane changed abruptly in the past, both during the last ice age, and during previous warm periods. The data will be used to understand how methane sources like wildfires, methane hydrates, and wetlands respond to climate change. This information is needed to understand future risks of large changes in methane in the atmosphere as Earth warms. The project involves two tasks. First, the investigators will build and test a gas extraction system for methane isotopic measurements using continuous flow methods, with the goal of equaling or bettering the precision attained by the few other laboratories that make these measurements. The system will be interfaced with existing mass spectrometers at Oregon State University. The system consists of a vacuum chamber and sequence of traps, purification columns, and furnaces that separate methane from other gases and convert it to carbon dioxide or hydrogen for mass spectrometry. Second, the team will measure the isotopic composition of methane across large changes in concentration associated with two past interglacial periods and during abrupt methane changes of the last ice age. These measurements will be used to understand if the main reason for these concentration changes is climate-driven changes in emissions from wetlands, or whether other sources are involved, for example methane hydrates or wildfires.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.

该项目将开发测量冰芯中空气中甲烷中碳13与碳12的比率以及重氢与轻氢的比率的方法。 不同形式的碳和氢的比例是过去这种气体不同来源的“指纹”——例如热带湿地与海底冻结的甲烷。 一旦开发出分析方法，测量结果将用于研究过去冰河时期和之前温暖时期甲烷突然变化的原因。 这些数据将用于了解野火、甲烷水合物和湿地等甲烷来源如何应对气候变化。需要这些信息来了解随着地球变暖，大气中甲烷发生巨大变化的未来风险。该项目涉及两项任务。 首先，研究人员将使用连续流方法构建和测试用于甲烷同位素测量的气体提取系统，其目标是等于或提高进行这些测量的其他少数实验室所达到的精度。 该系统将与俄勒冈州立大学现有的质谱仪连接。该系统由一个真空室和一系列捕集器、纯化柱和熔炉组成，用于将甲烷与其他气体分离并将其转化为二氧化碳或氢气以进行质谱分析。 其次，该团队将测量与过去两个间冰期相关的浓度大幅变化以及最后一个冰河时期甲烷突然变化期间的甲烷同位素组成。 这些测量结果将用于了解这些浓度变化的主要原因是否是气候驱动的湿地排放变化，或者是否涉及其他来源，例如甲烷水合物或野火。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。

项目成果

Methane, ethane, and propane production in Greenland ice core samples and a first isotopic characterization of excess methane

• DOI: 10.5194/cp-19-999-2023
• 发表时间: 2023-05
• 期刊: Climate of the Past
• 影响因子: 4.3
• 作者: Michaela Mühl;J. Schmitt;B. Seth;James E. Lee;J. Edwards;E. Brook;T. Blunier;H. Fischer