Investigating links between atmospheric chemistry and climate using oxygen isotope measurements of sulfate and nitrate from Greenland ice cores

从冰芯记录中观察到的温室气体浓度与温度指标之间的密切相关性，对我们理解温室气体与气候之间的关系产生了深远的影响。然而，尽管进行了几十年的研究，我们仍然没有对温室气体浓度变化的原因有确切的了解。羟基自由基（OH）在决定对气候变化（如CH 4）和人类健康（如CO）都很重要的大气痕量气体的寿命方面起着重要作用，并在很大程度上决定了大气的氧化能力。氧同位素组成（∆从冰芯中提取的硝酸盐和硫酸盐气溶胶（17 O）提供了有关过去大气化学的信息，并可以作为评估古大气化学模型模拟的工具。硫酸盐和硝酸盐的初始测量∆南极洲东方冰芯的~（17）O表明，与前工业全新世相比，末次冰期对流层极区O_3浓度较高，中高纬度地区OH浓度较高。这些数据集的定量解释正在进行中，使用全球化学气候模型包含同位素示踪剂，并证明了硝酸盐和硫酸盐#8710; 17 O氧化剂浓度的敏感性。目前，在北方半球的冰川-间冰期时间尺度上还没有硫酸盐和硝酸盐的测量结果。在这里，我们的目标是扩大现有的观测数据集的冰川间冰期时间尺度的北方半球，以测试的假设，甲烷浓度的变化在很大程度上（50%），由于对流层OH浓度的变化，陆地植被建模。我们还将提供第一次研究OH的变化是否可以部分解释甲烷在两次突发气候事件中的变化。有关甲烷汇强度的定量信息将改变我们将甲烷记录定量解释为陆地气候条件代理的能力，并因此提高我们对气候变化与甲烷源和汇之间的机械反馈的理解。了解气候变化对大气化学和大气氧化能力的影响，对于预测未来气候变化对当地和区域空气污染和人类健康的影响至关重要。该项目将涉及在跨学科和国际范围内培训两名研究生（一名美国和一名法国）使用地球化学分析工具。

Observation of the tight correlation between greenhouse gas concentrations and indicators of temperature from the ice core record has had a profound impact on our understanding of the relationship between greenhouse gases and climate. However, despite many decades of research, we still do not have a firm understanding of the causes of the variability in greenhouse gas concentrations. The hydroxyl radical (OH) plays a major role in determining the lifetimes of atmospheric trace gases important to both climate change (e.g. CH4) and human health (e.g. CO), and largely determines the oxidative capacity of the atmosphere. The oxygen isotopic composition (∆17O) of nitrate and sulfate aerosols extracted from ice cores provides information about the chemistry of past atmospheres, and can serve as a tool for evaluating model simulations of paleo atmospheric chemistry. Initial measurements of sulfate and nitrate ∆17O from the Vostok, Antarctica ice core suggest higher tropospheric O3 concentrations in polar-regions and higher OH concentrations in the mid- to high-latitudes during the last glacial period relative to the preindustrial Holocene. Quantitative interpretation of these data sets is ongoing using a global chemistry-climate model containing the isotopic tracers, and demonstrates the sensitivity of nitrate and sulfate ∆17O to oxidant concentrations. Currently, no measurements of sulfate and nitrate ∆17O exist on the glacial-interglacial timescale in the Northern Hemisphere. Our goal here is to expand the existing observational data set on the glacial-interglacial timescale to the Northern Hemisphere in order to test the hypothesis that variability in methane concentrations on the on this timescale is largely (50%) due to changes in tropospheric OH concentrations, as has been suggested by terrestrial vegetation modeling. We also will provide a first look into whether changes in OH may partially explain variability of methane during two abrupt climate events. Quantitative information about the sink strength of methane will transform our ability to quantitatively interpret the methane record as a proxy for terrestrial climate conditions, and as such improve our understanding of the mechanistic feedbacks between climate change and the sources and sinks of methane. Understanding the affects of a changing climate on atmospheric chemistry and the oxidizing capacity of the atmosphere is crucial for predicting the impacts of future climate change on local and regional air pollution and human health. The project will involve training two graduate students (one US and one French) in the tools of geochemical analysis in an interdisciplinary and international context.