Generating an Isotopic Record of Atmospheric Methane and Nitrous Oxide Over the Last Century from South Pole Firn Air

该奖项支持一个项目，该项目旨在构建上个世纪南极降雪空气中大气甲烷和一氧化二氮的同位素记录。在过去的150年里，大气中甲烷和一氧化二氮的浓度随着各种人类活动排放的增加而上升。由于这一趋势可能在可预见的未来继续下去，重要的是要了解造成这两种温室气体排放的生物地球化学过程。在这方面，在冰盖(冰雪空气)表面附近的冰芯和雪层间隙中发现的微量气体的大气负荷变化的记录，为恢复历史排放记录提供了基本的边界条件。提高我们对生物活性痕量气体循环及其排放记录的理解的一种方法是使用稳定的同位素示踪剂，这种示踪剂已被记录在冰芯和冰雪空气中。该项目将记录2001年1月在南极采集的空气样本中甲烷的碳-13和氢同位素比率，以及氮-15、氧-18和一氧化二氮的同位素组成。这些测量将使这些大气气体的同位素记录能够在整个20世纪重建。这类记录将有助于确定个别来源的相对贡献，其可信度比目前更高。

0125981SowersThis award supports a project to construct an isotopic record of atmospheric methane and nitrous oxide over the last century from South Pole firn air. Over the last 150 years, atmospheric methane and nitrous oxide concentrations have risen in response to increased emissions from various anthropogenic activities. As this trend is liable to continue in the foreseeable future, it is important to understand the biogeochemical processes that contribute to the emissions of these two greenhouse gases. In this context, records of the variations in the atmospheric loading of trace gases found in ice cores and interstitial spaces in the snow near the surface of the ice sheet (firn air) provide fundamental boundary conditions for reconstructing historical emission records. One way to improve our understanding of the cycling of bioactive trace gases and their emission records is to use stable isotope tracers, which have been recorded in the ice cores and firn air. This project will develop records of carbon-13 and deuterium isotope ratios of methane, as well as the nitrogen-15, oxygen-18 and the isotopomer composition of nitrous oxide trapped in firn air samples collected in January 2001 at the South Pole. These measurements will allow isotopic records of these atmospheric gases to be reconstructed throughout the 20th century. Such records will help to establish the relative contribution of individual sources with a higher degree of confidence than is currently available.