Methyl chloride and methyl bromide in Antarctic ice cores

该奖项支持在南极冰芯中对臭氧消耗物质甲基溴（CH3Br）和甲基氯（CH3Cl）以及含硫气体羰基硫化物（OCS）的分析。广泛的科学目标是评估这些气体在工业化前大气中的水平和变化。这一信息将有助于测试目前的大气中这些气体源和汇模式，并间接评估人为活动对其生物地球化学循环的影响。长期记录将揭示这些气体对大气负荷的气候敏感性，并最终揭示控制它们的生物地球化学过程。这些气体以万亿分之一的水平存在于冰中，而目前的数据库完全是由从南极洲simple Dome的一个浅冰核中获得的少量测量数据组成的。该项目将包括对三个南极地点的冰芯样本的研究：simple Station， simple Dome和South Pole。该采样策略旨在实现以下几个目标：1)验证先前在浅层简单圆顶冰中观测到的OCS、CH3Br和CH3Cl在不同积累速率和表面温度下的大气混合比；2)从高富集率站点（simple Station）获得年代准确、分辨率高的记录，该记录可提供与南极大气样品在平均气体年龄上的重叠；3)探索全新世微量气体混合比的变化；4)首次测量南极冰川中的微量气体。就对社会的广泛影响而言，这项研究将有助于为调节臭氧消耗气体和气候活性气体的生产和使用的政策决策提供更强有力的科学依据。具体而言，甲基溴的研究结果将有助于目前关于最近的管制（通过《蒙特利尔议定书》及其修正案）对大气水平的影响的辩论。确定工业化前消耗臭氧物质的大气变率将有助于对未来用于预测平流层臭氧及其气候影响的各种情景施加更现实的限制。这项研究将涉及研究生和本科生的参与。

This award supports the analysis, in Antarctic ice cores, of the ozone depleting substances methyl bromide (CH3Br) and methyl chloride (CH3Cl), and the sulfur-containing gas, carbonyl sulfide (OCS). The broad scientific goal is to assess the level and variability of these gases in the preindustrial atmosphere. This information will allow testing of current models for sources and sinks of these gases from the atmosphere, and to indirectly assess the impact of anthropogenic activities on their biogeochemical cycles. Longer-term records will shed light on the climatic sensitivity of the atmospheric burden of these gases, and ultimately on the biogeochemical processes controlling them. These gases are present in ice at parts per trillion levels, and the current database consists entirely of a small number of measurements made in from a shallow ice core from Siple Dome, Antarctica. This project will involve studies of ice core samples from three Antarctic sites: Siple Station, Siple Dome, and South Pole. The sampling strategy is designed to accomplish several objectives: 1) to verify the atmospheric mixing ratios previously observed in shallow Siple Dome ice for OCS, CH3Br, and CH3Cl at sites with very different accumulation rates and surface temperatures; 2) to obtain a well-dated, high resolution record from a high accumulation rate site (Siple Station), that can provide overlap in mean gas age with Antarctic firn air samples; 3) explore Holocene variability in trace gas mixing ratios; and 4) to make the first measurements of these trace gases in Antarctic glacial ice. In terms of broader impact on society, this research will help to provide a stronger scientific basis for policy decisions regulating the production and use of ozone-depleting and climate-active gases. Specifically, the methyl bromide results will contribute to the current debate on the impact of recent regulation (via the Montreal Protocol and its Amendments) on atmospheric levels. Determination of pre-industrial atmospheric variability of ozone-depleting substances will help place more realistic constraints on scenarios used for future projections of stratospheric ozone and its climatic impacts. This research will involve the participation of both graduate and undergraduate students.