Collaborative Research: Inert Gas and Methane Based Climate Records throughout the South Pole Deep Ice Core

合作研究：整个南极深冰芯基于惰性气体和甲烷的气候记录

• 批准号: 1443464
• 负责人: Todd Sowers
• 金额: $ 41.22万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443464&HistoricalAwards=false
• 关键词: Collaborative; Research; Inert; Gas; Methane

Gases trapped in ice cores have revealed astonishing things about the greenhouse gas composition of the past atmosphere, including the fact that carbon dioxide concentrations never rose above 300 parts per million during the last 800,000 years. This places today's concentration of 400 parts per million in stark contrast. Furthermore, these gas records show that natural sources of greenhouse gas such as oceans and ecosystems act as amplifiers of climate change by increasing emissions of gases during warmer periods. Such amplification is expected to occur in the future, adding to the human-produced gas burden. The South Pole ice core will build upon these prior findings by expanding the suite of gases to include, for the first time, those potent trace gases that both trapped heat and depleted ozone during the past 40,000 years. The present project on inert gases and methane in the South Pole ice core will improve the dating of this crucial record, to unprecedented precision, so that the relative timing of events can be used to learn about the mechanism of trace gas production and destruction, and consequent climate change amplification. Ultimately, this information will inform predictions of future atmospheric chemical cleansing mechanisms and climate in the context of our rapidly changing atmosphere. This award also engages young people in the excitement of discovery and polar research, helping to entrain the next generations of scientists and educators. Education of graduate students, a young researcher (Buizert), and training of technicians, will add to the nation?s human resource base. This award funds the construction of the gas chronology for the South Pole 1500m ice core, using measured inert gases (d15N and d40Ar--Nitrogen and Argon isotope ratios, respectively) and methane in combination with a next-generation firn densification model that treats the stochastic nature of air trapping and the role of impurities on densification. The project addresses fundamental gaps in scientific understanding that limit the accuracy of gas chronologies, specifically a poor knowledge of the controls on ice-core d15N and the possible role of layering and impurities in firn densification. These gaps will be addressed by studying the gas enclosure process in modern firn at the deep core site. The work will comprise the first-ever firn air pumping experiment that has tightly co-located measurements of firn structural properties on the core taken from the same borehole.The project will test the hypothesis that the lock-in horizon as defined by firn air d15N, CO2, and methane is structurally controlled by impermeable layers, which are in turn created by high-impurity content horizons in which densification is enhanced. Thermal signals will be sought using the inert gas measurements, which improve the temperature record with benefits to the firn densification modeling. Neon, argon, and oxygen will be measured in firn air and a limited number of deep core samples to test whether glacial period layering was enhanced, which could explain low observed d15N in the last glacial period. Drawing on separate volcanic and methane synchronization to well-dated ice cores to create independent ice and gas tie points, independent empirical estimates of the gas age-ice age difference will be made to check the validity of the firn densification model-inert gas approach to calculating the gas age-ice age difference. These points will also be used to test whether the anomalously low d15N seen during the last glacial period in east Antarctic ice cores is due to deep air convection in the firn, or a missing impurity dependence in the firn densification models. The increased physical understanding gained from these studies, combined with new high-precision measurements, will lead to improved accuracy of the gas chronology of the South Pole ice core, which will enhance the overall science return from this gas-oriented core. This will lead to clarification of timing of atmospheric gas variations and temperature, and aid in efforts to understand the biogeochemical feedbacks among trace gases. These feedbacks bear on the future response of the Earth System to anthropogenic forcing. Ozone-depleting substances will be measured in the South Pole ice core record, and a precise gas chronology will add value. Lastly, by seeking a better understanding of the physics of gas entrapment, the project aims to have an impact on ice-core science in general.

封存在冰芯中的气体揭示了过去大气中温室气体组成的惊人情况，包括在过去80万年中二氧化碳浓度从未超过百万分之300的事实。这与今天百万分之400的浓度形成了鲜明的对比。此外，这些气体记录表明，海洋和生态系统等温室气体的自然来源在较暖时期增加了气体排放，从而放大了气候变化。这种放大预计将在未来发生，增加人为产生的气体负担。南极冰芯将以这些先前的发现为基础，扩大气体的种类，首次包括那些在过去4万年中既能留住热量又能消耗臭氧的强效微量气体。目前关于南极冰芯中惰性气体和甲烷的项目将提高这一重要记录的定年精度，达到前所未有的精度，从而可以利用事件的相对时间来了解微量气体产生和破坏的机制，以及随之而来的气候变化放大。最终，这些信息将为在我们快速变化的大气背景下预测未来的大气化学净化机制和气候提供信息。该奖项还吸引年轻人参与发现和极地研究的兴奋，帮助培养下一代科学家和教育工作者。研究生的教育、年轻的研究员（Buizert）和技术人员的培养将使国家受益。人力资源基础。该奖项资助建立南极1500米冰芯的气体年表，使用测量的惰性气体（分别为d15N和d40Ar-氮和氩同位素比率）和甲烷，结合下一代固体致密化模型，该模型处理空气捕获的随机性和杂质在致密化中的作用。该项目解决了科学认识上的基本空白，这些空白限制了气体年表的准确性，特别是对冰芯d15N控制的认识不足，以及层状和杂质在固体致密化中的可能作用。这些空白将通过研究现代公司在深岩心现场的气体封闭过程来解决。这项工作将包括有史以来第一次铁石气泵实验，该实验将从同一钻孔中对岩心的铁石结构特性进行紧密的同步测量。该项目将测试一个假设，即由固定空气（氮、二氧化碳和甲烷）定义的锁定层在结构上由不透水层控制，而不透水层又由高杂质含量层形成，其致密性增强。将使用惰性气体测量来寻找热信号，这将改善温度记录，有利于公司的致密化建模。我们将在坚硬的空气和有限数量的深部岩心样品中测量氖、氩和氧，以测试冰期分层是否增强，这可以解释末次冰期观测到的低d15N。利用分离的火山和甲烷同步到年代确定的冰芯来创建独立的冰和气体结合点，对气体年龄-冰河年龄差异进行独立的经验估计，以检验固体致密化模型-惰性气体方法计算气体年龄-冰河年龄差异的有效性。这些点还将用于检验末次冰期在南极东部冰芯中观测到的异常低d15N是由于冰芯中的深层空气对流，还是由于冰芯致密化模型中缺失的杂质依赖。从这些研究中获得的更多物理认识，结合新的高精度测量，将提高南极冰芯气体年代学的准确性，这将提高该气体导向岩芯的整体科学回报。这将有助于澄清大气气体变化和温度的时间，并有助于理解微量气体之间的生物地球化学反馈。这些反馈关系到地球系统未来对人为强迫的反应。消耗臭氧层的物质将在南极冰芯记录中进行测量，而精确的气体年表将增加价值。最后，通过更好地了解气体夹持的物理学，该项目旨在对冰芯科学产生总体影响。