Collaborative Research: A "Horizontal Ice Core" for Large-Volume Samples of the Past Atmosphere, Taylor Glacier, Antarctica

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该奖项支持一个项目，为古代大气的大量样本档案开发精确的基于气体的年表，这将使超微量气体测量成为可能，目前由于冰芯的样本大小限制而无法进行测量。这项工作的学术价值在于，它将为“包合物假说”提供一个关键的检验，该假说认为甲烷包合物导致了15年前和11年前最后一次冰期期间大气甲烷浓度的两次突然增加。这种方法使用大量的冰（1吨）来测量突发性事件中过去大气中甲烷的碳-14含量。碳-14是大气中甲烷化石来源的理想鉴别指标，因为大多数甲烷来源（如湿地、白蚁、生物质燃烧）富含碳-14，而笼形物和其他化石来源缺乏碳-14。这项拟议的工作是对南极洲泰勒冰川的合理延伸，这是过去7年来在格陵兰冰盖边缘开创的一种方法。格陵兰岛的研究发现碳-14值高于预期，部分原因可能是格陵兰冰的高杂质含量和冰与冰川床沉积物的相互作用所产生的污染物。这些数据还指出了一个以前未知的过程的可能性，即冰基质中碳-14甲烷（放射性甲烷）的原位宇宙成因生产。南极泰勒冰川的冰比格陵兰岛的冰干净几个数量级，而且更冷，地层扰动也更少，这为明确解决这一难题提供了可能，并为宇宙形成辐射甲烷假说提供了明确的检验。即使在冰中发现了宇宙形成的放射性甲烷，通过对这一过程的详细了解，仍然有可能重建大气中的放射性甲烷，这将通过共同测量一氧化碳和二氧化碳中的碳-14来寻求。拟议工作的更广泛影响是，包合物测试可能揭示包合物库的稳定性及其在人为变暖下气候反馈的潜力。Taylor冰川作为“水平冰芯”的发展将为其他研究人员提供社区资源。培养一名博士后、一名研究生和一名本科生，将增加人力资源。这个奖项在南极洲进行实地考察。

Severinghaus/0839031 This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This award supports a project to develop a precise gas-based chronology for an archive of large-volume samples of the ancient atmosphere, which would enable ultra-trace gas measurements that are currently precluded by sample size limitations of ice cores. The intellectual merit of the proposed work is that it will provide a critical test of the "clathrate hypothesis" that methane clathrates contributed to the two abrupt atmospheric methane concentration increases during the last deglaciation 15 and 11 kyr ago. This approach employs large volumes of ice (1 ton) to measure carbon-14 on past atmospheric methane across the abrupt events. Carbon-14 is an ideal discriminator of fossil sources of methane to the atmosphere, because most methane sources (e.g., wetlands, termites, biomass burning) are rich in carbon-14, whereas clathrates and other fossil sources are devoid of carbon-14. The proposed work is a logical extension to Taylor Glacier, Antarctica, of an approach pioneered at the margin of the Greenland ice sheet over the past 7 years. The Greenland work found higher-than-expected carbon-14 values, likely due in part to contaminants stemming from the high impurity content of Greenland ice and the interaction of the ice with sediments from the glacier bed. The data also pointed to the possibility of a previously unknown process, in-situ cosmogenic production of carbon-14 methane (radiomethane) in the ice matrix. Antarctic ice in Taylor Glacier is orders of magnitude cleaner than the ice at the Greenland site, and is much colder and less stratigraphically disturbed, offering the potential for a clear resolution of this puzzle and a definitive test of the cosmogenic radiomethane hypothesis. Even if cosmogenic radiomethane in ice is found, it still may be possible to reconstruct atmospheric radiomethane with a correction enabled by a detailed understanding of the process, which will be sought by co-measuring carbon-14 in carbon monoxide and carbon dioxide. The broader impacts of the proposed work are that the clathrate test may shed light on the stability of the clathrate reservoir and its potential for climate feedbacks under human-induced warming. Development of Taylor Glacier as a "horizontal ice core" would provide a community resource for other researchers. Education of one postdoc, one graduate student, and one undergraduate, would add to human resources. This award has field work in Antarctica.