Methyl chloride and methyl bromide in Antarctic ice cores

该奖项支持在南极冰芯中分析臭氧消耗物质甲基溴（CH 3Br）和甲基氯（CH 3Cl）以及含硫气体羰基硫（OCS）。 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变化。 这些资料将有助于检验目前关于大气中这些气体的源和汇的模型，并间接评估人类活动对其地球化学循环的影响。 长期记录将有助于了解这些气体在大气中的含量对气候的敏感性，并最终了解控制这些气体的地球化学过程。 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来自南极洲Siple Dome的浅冰芯的少量测量组成。 该项目将涉及对南极三个地点的冰芯样本进行研究：西普尔站、西普尔圆顶和南极。 采样策略旨在实现以下几个目标：1）验证先前在具有非常不同的积累速率和表面温度的站点处的浅Siple Dome冰中观测到的OCS、CH 3Br和CH 3Cl的大气混合比; 2）从高积累率场地获得日期准确、分辨率高的记录（Siple站），这可以提供重叠的平均气体年龄与南极积雪空气样品; 3）探索全新世变化的微量气体混合比;和4）使这些微量气体在南极冰川冰的第一次测量。 就对社会的更广泛影响而言，这项研究将有助于为管理消耗臭氧层气体和气候活性气体的生产和使用的政策决定提供更有力的科学依据。具体而言，甲基溴的结果将有助于目前关于最近的条例（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。 确定工业化前大气层中臭氧消耗物质的变异性将有助于对未来预测平流层臭氧及其气候影响所采用的设想方案施加更现实的限制。 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.