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: 1443710
• 负责人: Jeffrey Severinghaus
• 金额: $ 41.15万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 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 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443710&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.

被困在冰芯中的气体揭示了关于过去气氛的温室气体成分令人惊讶的事情，其中​​包括二氧化碳浓度在过去的80万年中从未超过每百万分之300份。 这使当今的浓度为每百万分之400份的鲜明对比。 此外，这些天然气记录表明，温室气体（例如海洋和生态系统）的天然来源通过在较温暖时期内增加气体排放来充当气候变化的放大器。 预计将来会发生这种扩增，从而增加了人类产生的气体负担。 南极冰芯将通过扩大气体套件来建立在这些先前发现的基础上，以首次包括在过去40，000年中捕获热量和耗尽臭氧的那些有效的痕量气体。 目前关于南极冰芯中惰性气体和甲烷的项目将改善这种关键记录的日期，以实现前所未有的精度，以便可以使用事件的相对时机来了解痕量气体产生和破坏的机理，并导致气候变化的扩增。 最终，在我们快速变化的大气中，这些信息将为未来大气化学清洁机制和气候的预测提供信息。 该奖项还吸引了年轻人的发现和极地研究的兴奋，有助于吸引下一代的科学家和教育工作者。 研究生的教育，年轻的研究人员（Buizert）以及对技术人员的培训，将增加国家的人力资源基础。 该奖项使用测量的惰性气（分别为D15N和D40AR-氮和氩同位素比）和甲烷结合了下一代FIRN致密模型，从而为南极1500m冰芯的气体年代学提供了资金。 该项目解决了科学理解中的基本差距，这些差距限制了气体年代的准确性，特别是对冰核D15N的控制的知识不足以及分层和杂质在FIRN致密化中的可能作用。 这些差距将通过研究深层核心地点现代FIRN的气体外壳过程来解决。 这项工作将构成有史以来的第一个FIRN空气抽水实验，该实验对从同一钻孔采集的核心的FIRN结构特性进行了严格的测量。该项目将检验以下假设：FIRN AIR D15N，CO2，CO2和甲烷的结构控制的lifn Air D15N，CO2和甲烷在不可能的层面上构成了较高的层面，该层是在该层中所产生的，该层是较高的范围，该层是在较高的范围内，该层是在较高的范围内，该层是在较高的范围内，该层是在该层面上构成的。 将使用惰性气体测量值来寻求热信号，从而改善温度记录，并获得FIRN致密化建模的好处。 霓虹灯，氩气和氧气将在FIRN空气中测量，并测量有限数量的深核样品，以测试冰川周期分层是否增强，这可以解释在最后一个冰川时期观察到的D15N低。 利用单独的火山和甲烷同步到年代良好的冰芯以创建独立的冰和气结点，将对气体年龄 - 冰年龄差的独立经验估计来检查FIRN致密启动气体方法的有效性，以计算气体年龄冰年龄的年龄差异。 这些点还将用于测试在南极冰芯的最后一个冰川时期看到的异常低D15N是由于FIRN中的深空对流引起的，还是FIRN致密化模型中缺失的杂质依赖性。 从这些研究中获得的物理理解增强，再加上新的高精度测量结果，将提高南极冰核的气体年表的准确性，这将增强从这种面向气体的核心的整体科学回报。 这将导致澄清大气气体变化和温度的时机，并有助于了解痕量气体之间的生物地球化学反馈。 这些反馈意见了地球系统对人为强迫的未来响应。 臭氧耗尽物质将在南极冰核心记录中测量，并且精确的气体年表将增加价值。 最后，通过寻求更好地了解气体夹带的物理学，该项目旨在对一般的冰核科学产生影响。