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

在过去，地球的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。这种变化在地球大气层中留下了印记，如二氧化碳和甲烷等微量气体丰度的变化所示。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地球化学循环与地球相互作用的历史。的气候。关于过去大气成分的最可靠信息来自对极地冰芯中空气的分析。该项目的目的是生成相对短暂、丰度极低的痕量气体的冰芯记录，以确定其大气水平过去变化的范围，并调查造成这种变化的全球地球化学循环的变化。该项目测量三种此类气体：硫化羰、氯甲烷和溴甲烷。 羰基硫的变化可以指示初级生产力和二氧化碳的光合更新的变化。 甲基氯和甲基溴的变化对平流层臭氧的自然变异性产生重大影响。 此外，控制大气中甲基氯和甲基溴含量的工艺与控制大气中甲烷含量的工艺相同。 这些测量将在来自南极的新冰芯中进行，预计将提供4万年的记录，这一项目的首要重点是开发整个全新世时期的高质量示踪气体记录（过去的11,000年），以及从末次冰期（包括29000 -36年）开始的更多探索性测量，2000年前，大气中的甲烷发生了巨大的变化。由于南极冰的低温，拟议的羰基硫化物测量预计将提供一个直接的测量过去的大气变化的这种气体没有大的水解校正，这是必要的解释从冰芯在温暖的设置。 此外，我们将测试的期望，从最后一个冰期在南极西部冰盖划分冰芯深处的同期测量将不需要水解损失校正。 关于氯甲烷，我们的目标是验证和改善现有的全新世大气历史从泰勒圆顶冰芯在南极洲。我们的测量结果与Taylor Dome的测量结果相比具有更高的分辨率，这将使我们能够得出氯甲烷和甲烷之间更具统计学意义的关系。关于甲基溴，我们计划将现有的2 000年数据库扩大到11 000年。甲基溴和甲基氯的记录将共同为全新世期间平流层卤素的自然变化提供强有力的基于测量的制约因素。此外，甲基溴记录将有助于深入了解全新世时期由于共同的源和汇而导致的甲基氯和甲烷之间的相互关系。

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.