Controls on Variations in Atmospheric Carbon Dioxide and Nitrous Oxide During the Last 10,000 years

The temperature of the earth is controlled, in part, by heat trapping gases that include carbon dioxide, methane, and nitrous oxide. Despite their importance to climate, direct measurements of these gases in the atmosphere are limited to the last 50 years at best. Air trapped in ice cores extends those data back hundreds of millennia, and measurements of greenhouse gases in ice cores underpin much of our understanding of global chemical cycles relevant to modern climate change. Existing records vary in quality and detail. The proposed work fills gaps in our knowledge of nitrous oxide and carbon dioxide over the last 10,000 years. New measurements from an ice core from the South Pole will be used to determine what role changes in ocean and land based processes played in controlling these gases, which decreased during the first 2,000 years of this time period, then gradually increased toward the present. The work will address a major controversy over whether early human activities could have impacted the atmosphere, and provide data to improve mathematical models of the land-ocean-atmosphere system that predict how future climate change will impact the composition of the atmosphere and climate.

For nitrous oxide the work will improve on existing concentration records It will also develop measurement of the isotopomers of nitrous oxide and explore their utility for understanding aspects of the Holocene nitrous oxide budget. The primary goal is to determine if marine and/or terrestrial emissions of nitrous oxide change in response to changes in Holocene climate. A new Holocene isotopic record for carbon dioxide (stable carbon and oxygen isotopes), will improve the precision of existing records by a factor 5 and increase the temporal resolution. These data will be used to evaluate controversial hypotheses about why carbon dioxide concentrations changed in the Holocene and provide insight into millennial scale processes in the carbon cycle, which are not resolved by current isotopic data. A graduate student and post doc will receive advanced training during and the student and principle investigator will conduct outreach efforts targeted at local middle school students. The proposed work will also contribute to teaching efforts by the PI and to public lectures on climate and climate change. The results will be disseminated through publications, data archive, and the OSU Ice Core Lab web site. New analytical methods of wide utility will also be developed and documented.

地球气温在一定程度上受温室气体（greenhouse gases）调控，这类气体包括二氧化碳（carbon dioxide）、甲烷（methane）以及一氧化二氮（nitrous oxide）。尽管这些气体对气候至关重要，但目前对大气中这些气体的直接观测记录，最长仅能追溯至过去50年。封存在冰芯（ice cores）中的空气则可将此类观测数据回溯至数十万年前，而冰芯温室气体测量结果为我们理解与现代气候变化相关的全球化学循环提供了核心支撑。现有记录的质量与细节程度参差不齐。本拟开展的研究将填补过去1万年间人们对一氧化二氮与二氧化碳认知的空白。研究将基于南极冰芯的全新测量数据，解析海洋与陆地过程变化在调控这类气体浓度中的作用——该类气体在本次时段的前2000年呈下降趋势，随后逐渐回升至现代水平。本研究将解决一项核心争议：早期人类活动是否曾对大气产生影响；同时将为改进陆-海-气系统数学模型提供数据支撑，这类模型可用于预测未来气候变化对大气成分与气候的影响。
针对一氧化二氮，本研究将优化现有浓度记录；同时将建立一氧化二氮同位素异构体（isotopomers）的测量方法，并探索其在解析全新世（Holocene）一氧化二氮收支相关问题中的应用价值。本研究的核心目标是明确：一氧化二氮的海洋与/或陆地排放是否会随全新世气候变迁发生变化。全新世二氧化碳的全新同位素记录（涵盖稳定碳、氧同位素（stable carbon and oxygen isotopes））将使现有记录的精度提升5倍，并提高其时间分辨率。这些数据将用于验证关于全新世二氧化碳浓度变化成因的争议性假说，并为解析当前同位素数据尚未厘清的千年尺度碳循环过程提供新视角。本研究将为一名研究生与一名博士后研究员提供高级培训；研究生与首席研究员（Principal Investigator，PI）还将面向当地中学生开展科普推广活动。本研究还将助力PI的教学工作，以及相关气候与气候变化主题的公众讲座。研究成果将通过学术期刊发表、数据归档以及OSU冰芯实验室（OSU Ice Core Lab）官网进行传播。本研究还将开发并记录一批具有广泛应用价值的新型分析方法。