Tracing Past Methane Variations with Stable Isotopes in Antarctic Ice Cores

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。 一旦分析方法被开发出来，测量结果将被用来研究为什么甲烷在过去突然变化，无论是在最后一个冰河时期，还是在以前的温暖时期。 这些数据将用于了解野火、甲烷水合物和湿地等甲烷源如何应对气候变化。需要这些信息来了解随着地球变暖，大气中甲烷的大变化的未来风险。该项目涉及两项任务。 首先，研究人员将建立和测试一个气体提取系统，使用连续流动方法进行甲烷同位素测量，目标是达到或提高其他几个进行这些测量的实验室所达到的精度。 该系统将与俄勒冈州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陷阱，纯化柱和熔炉组成，这些陷阱，纯化柱和熔炉将甲烷与其他气体分离并将其转化为二氧化碳或氢气用于质谱分析。 其次，研究小组将测量甲烷的同位素组成，这些甲烷的同位素组成与过去两个间冰期的浓度变化有关，以及在最后一个冰河时期的甲烷突然变化期间。 这些测量结果将用于了解这些浓度变化的主要原因是气候驱动的湿地排放变化，还是其他来源，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。

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.