Methyl chloride and methyl bromide in Antarctic ice cores

该奖项支持在南极冰芯对臭氧消耗物质甲基溴(CH3Br2)和甲基氯(CH3Cl2)以及含硫气体--羰基硫化物(OCS)进行分析。广泛的科学目标是评估工业化前大气中这些气体的水平和可变性。这些信息将使我们能够测试目前大气中这些气体的源和汇的模型，并间接评估人为活动对其生物地球化学循环的影响。更长期的记录将揭示这些气体大气负担的气候敏感性，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，目前的数据库完全由南极洲Siple Dome的一个浅冰芯进行的少量测量组成。该项目将对三个南极站点的冰芯样本进行研究：Siple站、Siple Dome和南极。采样战略旨在实现几个目标：1)验证先前在浅Siple Dome冰层中观测到的OCS、CH3Br1和CH3Cl3种气体在积累速度和表面温度非常不同的地点的大气混合比率；2)从高积累速率站点(Siple Station)获得日期准确、高分辨率的记录，这可以提供与南极冰雪空气样本的平均气体年龄重叠；3)探索全新世痕量气体混合比率的变异性；以及4)首次测量南极冰川冰中的这些微量气体。就更广泛的社会影响而言，这项研究将有助于为规范臭氧消耗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。具体地说，甲基溴的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。确定臭氧消耗物质在工业化前的大气可变性将有助于对平流层臭氧及其气候影响的未来预测所使用的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.