Carbonyl Sulfide, Methyl Chloride, and Methyl Bromide Measurements in the New Intermediate-depth South Pole Ice Core

过去，地球气候经历了巨大的变化，影响了全球范围内的物理、化学、地质和生物过程。这些变化在地球大气中留下了印记，二氧化碳和甲烷等微量气体丰度的变化就表明了这一点。作为回报，大气微量气体成分的变化影响了地球的气候。研究过去大气的成分变化有助于我们了解全球生物地球化学循环与地球气候之间相互作用的历史。关于过去大气成分的最可靠信息来自对极地冰芯中截留空气的分析。该项目旨在生成寿命相对较短、丰度极低的痕量气体的冰芯记录，以确定其大气水平过去的变化范围，并调查导致这种变化的全球生物地球化学循环的变化。该项目测量三种此类气体：硫化碳、氯甲烷和溴甲烷。 硫化羰的变化可以表明初级生产力和二氧化碳光合作用更新的变化。 氯甲烷和溴甲烷的变化显着影响平流层臭氧的自然变化。 此外，控制大气中氯甲烷和溴甲烷水平的过程与控制大气甲烷水平的过程是共享的。 这些测量将在南极的新冰芯中进行，预计将提供 40,000 年的记录。该项目的主要重点是开发整个全新世时期（过去 11,000 年）的高质量微量气体记录，并对末次冰期（包括 29,000 至 36,000 年前大气甲烷发生巨大变化的时期）进行额外的、更具探索性的测量。由于南极冰的温度较低，拟议的硫化羰测量预计将直接测量该气体过去的大气变化，而无需进行大的水解校正，而水解校正是解释较温暖环境中冰芯测量值所必需的。 此外，我们将测试南极西部冰盖深处冰盖冰芯末次冰河期的同期测量结果不需要水解损失校正的预期。 对于氯甲烷，我们的目标是验证和改善南极洲泰勒穹顶冰芯现有的全新世大气历史。与泰勒穹顶的测量相比，我们的测量分辨率更高，这将使我们能够得出氯甲烷和甲烷之间在统计上更显着的关系。关于甲基溴，我们计划将现有的2000年数据库扩展到11000年。甲基溴和甲基氯记录一起将为全新世期间平流层卤素的自然变化提供基于测量的强有力的限制。此外，甲基溴记录将有助于深入了解全新世时期甲基氯和甲烷之间由于共同源和汇而存在的相关性。

In the past, Earth's climate underwent dramatic changes that influenced physical, chemical, geological, and biological processes on a global scale. Such changes left an imprint in Earth's atmosphere, as shown by the variability in abundances of trace gases like carbon dioxide and methane. In return, changes in the atmospheric trace gas composition affected Earth's climate. Studying compositional variations of the past atmosphere helps us understand the history of interactions between global biogeochemical cycles and Earth?s climate. The most reliable information on past atmospheric composition comes from analysis of air entrapped in polar ice cores. This project aims to generate ice-core records of relatively short-lived, very-low-abundance trace gases to determine the range of past variability in their atmospheric levels and investigate the changes in global biogeochemical cycles that caused this variability. This project measures three such gases: carbonyl sulfide, methyl chloride, and methyl bromide. Changes in carbonyl sulfide can indicate changes in primary productivity and photosynthetic update of carbon dioxide. Changes in methyl chloride and methyl bromide significantly impact natural variability in stratospheric ozone. In addition, the processes that control atmospheric levels of methyl chloride and methyl bromide are shared with those controlling levels of atmospheric methane. The measurements will be made in the new ice core from the South Pole, which is expected to provide a 40,000-year record.The primary focus of this project is to develop high-quality trace gas records for the entire Holocene period (the past 11,000 years), with additional, more exploratory measurements from the last glacial period including the period from 29,000-36,000 years ago when there were large changes in atmospheric methane. Due to the cold temperatures of the South Pole ice, the proposed carbonyl sulfide measurements are expected to provide a direct measure of the past atmospheric variability of this gas without the large hydrolysis corrections that are necessary for interpretation of measurements from ice cores in warmer settings. Furthermore, we will test the expectation that contemporaneous measurements from the last glacial period in the deep West Antarctic Ice Sheet Divide ice core will not require hydrolysis loss corrections. With respect to methyl chloride, we aim to verify and improve the existing Holocene atmospheric history from the Taylor Dome ice core in Antarctica. The higher resolution of our measurements compared with those from Taylor Dome will allow us to derive a more statistically significant relationship between methyl chloride and methane. With respect to methyl bromide, we plan to extend the existing 2,000-year database to 11,000 years. Together, the methyl bromide and methyl chloride records will provide strong measurement-based constraints on the natural variability of stratospheric halogens during the Holocene period. In addition, the methyl bromide record will provide insight into the correlation between methyl chloride and methane during the Holocene period due to common sources and sinks.