Investigation of Past Atmospheric Methane Variability with Stable Isotopes in Antarctic Ice Cores

用南极冰芯稳定同位素研究过去大气甲烷变化

• 批准号: 2324307
• 负责人: Edward Brook
• 金额: $ 53.24万
• 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: 2023
• 资助国家: 美国
• 起止时间: 2023-10-01 至 2026-09-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2324307&HistoricalAwards=false
• 关键词: Investigation; Past; Atmospheric; Methane; Variability

Atmospheric methane contributes to the greenhouse effect and therefore Earth’s temperature. Humans have caused an almost three-fold increase in methane since the industrial revolution. As the planet warms, changes on the Earth surface and in the atmosphere will further change methane levels. How these feedbacks will change over time is not well known. Studies of past variations in methane, by measuring ancient air trapped in ice, provide examples of these changes and help build better predictions of future change. In this project researchers will use measurements of different chemical forms of the carbon and hydrogen in methane to better understand reasons for past changes. The proposed research will develop laboratory measurement methods for hydrogen isotopes, use the different chemical forms of methane to understand the changes in atmospheric methane that happened when past ice ages ended and the Earth warmed, and use unique, very old ice samples ( 1 million years) from Antarctica to understand what controls methane levels in the atmosphere when climate was as warm or warmer than today. Developing new methods involves testing an existing system for purifying methane for measurements of hydrogen isotopes by mass spectrometry. The system is already operational and calibrated for carbon isotopes in methane. Next, the researchers will measure hydrogen isotopes in methane from samples from Taylor Glacier and Allan Hills, Antarctica, that cover two transitions from ice ages to interglacial warm periods. These data will be used to constrain where the methane increase that happened at these times originated, because hydrogen isotope ratios are sensitive to the latitude of the methane source. Finally, the researchers will measure both carbon and hydrogen isotopes in samples from 1 to 3 million years in age from the Allan Hills Blue Ice Area in Antarctica. Comparisons between these measurements and existing data for younger samples may reveal important differences between the mixture of source types that make up the methane budget in these different time periods. For example, prior to 1 million years ago, the apparent lack of large Northern Hemisphere ice sheets during glacial periods, and resulting higher glacial sea levels, would have had impacts on the global wetland methane source. Additionally, warmer temperatures might have increased CH4 emissions from wetlands but also increased production of the hydroxyl radical and methane destruction in the stratosphere. The project will support a post-doctoral researcher who will collaborate with the Ice Drilling Program at Dartmouth College to create virtual field labs used in high school and college classes.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.

大气甲烷有助于温室效应，因此有助于地球的温度。自工业革命以来，人类已导致甲烷增加了近三倍。随着行星的变暖，地球表面和大气中的变化将进一步改变甲烷水平。这些反馈会随着时间的流逝而改变。通过测量被困在冰中的古代空气中，对甲烷过去变化的研究提供了这些变化的例子，并有助于更好地预测未来变化的预测。在这个项目中，研究人员将使用甲烷中碳和氢的不同化学形式的测量，以更好地理解过去变化的原因。拟议的研究将开发用于氢同位素的实验室测量方法，使用不同的化学形式的甲烷来了解过去冰老龄结束时发生的大气甲烷的变化，地球变暖，并使用南极的独特，非常古老的冰（100万年）来了解什么是在气候温暖或温暖的情况下控制大气层的甲烷水平。开发新方法涉及测试现有的系统，用于通过质谱法测量氢同位素的测量。该系统已经在甲烷中的碳同位素进行校准。接下来，研究人员将测量来自泰勒冰川和南极洲的艾伦山的样品中甲烷中的氢同位素，这些氢涵盖了从冰年到冰期间温暖时期的两个过渡。这些数据将用于约束这些时间在这些时间发生的甲烷增加的位置，因为氢同位素比对甲烷源的纬度敏感。最后，研究人员将在南极洲的Allan Hills Blue Ice地区从1到300万年的样品中测量碳和氢同位素。这些测量结果与年轻样品的现有数据之间的比较可能会揭示构成这些不同时间段构成甲烷预算的源类型的混合物之间的重要差异。例如，在一百万年前，在冰川期间，明显缺乏北半球冰盖，并导致更高的冰川海平面会对全球湿地甲烷源产生影响。此外，较高的温度可能增加了湿地的CH4排放，但同时增加了平流层中羟基自由基和甲基乙烷破坏的产生。该项目将支持一名博士后研究人员，他将与达特茅斯学院的冰钻计划合作，创建在高中和大学课程中使用的虚拟现场实验室。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准通过评估来评估的。