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: 1443472
• 负责人: Edward Brook
• 金额: $ 15.01万
• 依托单位: Oregon State University
• 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 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443472&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过去大气中温室气体成分的惊人变化，包括二氧化碳浓度在过去80万年中从未超过百万分之300。 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温暖时期增加了气体排放，从而放大了气候变化。 预计这种放大将在未来发生，增加人类产生的气体负担。 南极冰芯将在这些先前发现的基础上，通过扩大气体套件，首次包括那些在过去40，000年中捕获热量和消耗臭氧的强效痕量气体。 目前关于南极冰芯中惰性气体和甲烷的项目将改进这一关键记录的年代测定，使之达到前所未有的精确度，以便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，这些信息将在我们迅速变化的大气层背景下为未来大气化学清洁机制和气候的预测提供信息。 该奖项还让年轻人参与发现和极地研究的兴奋，帮助吸引下一代科学家和教育家。 研究生的教育，一个年轻的研究员（Buizert），和技术人员的培训，将增加国家？的人力资源基础。 该奖项为南极1500米冰芯的气体年表的建设提供资金，使用测量的惰性气体（d15 N和d40 Ar-氮和氩同位素比，分别）和甲烷结合下一代积雪致密化模型，处理空气捕获的随机性和杂质对致密化的作用。 该项目解决了科学认识上的根本差距，限制了气体年表的准确性，特别是对冰芯d15 N的控制以及分层和杂质在积雪致密化中的可能作用的了解不足。 这些差距将通过研究在深核心站点的现代积雪中的气体封闭过程来解决。 这项工作将包括有史以来第一次的积雪空气泵实验，该实验对取自同一钻孔的岩芯上的积雪结构特性进行了紧密的共位测量。该项目将测试以下假设：由积雪空气d15 N、CO2和甲烷定义的锁定层位在结构上受不渗透层控制，而不渗透层位又由高杂质含量的层位产生，在不渗透层位中，致密化得到增强。 将使用惰性气体测量来寻求热信号，这改善了温度记录，有利于积雪致密化建模。 氖，氩和氧将被测量在积雪空气和数量有限的深芯样品，以测试是否冰川期分层增强，这可以解释低观察到的d15 N在末次冰期。 利用独立的火山和甲烷同步到日期明确的冰芯来创建独立的冰和气联系点，将对气体年龄-冰期差异进行独立的经验估计，以检查用于计算气体年龄-冰期差异的积雪致密化模型-惰性气体方法的有效性。 这些点也将被用来测试是否异常低d15 N看到在末次冰期在南极洲东部冰芯是由于深层空气对流的积雪，或在积雪致密化模型中缺少杂质的依赖。 从这些研究中获得的更多的物理认识，加上新的高精度测量，将导致提高南极冰芯气体年表的准确性，这将提高这一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间，并帮助努力了解痕量气体之间的地球化学反馈。 这些反馈关系到地球系统对人类强迫的未来响应。 臭氧消耗物质将在南极冰芯记录中进行测量，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截留的物理学，该项目旨在对冰芯科学产生影响。