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

被困在冰芯中的气体揭示了过去大气中温室气体组成的惊人事情，包括在过去80万年里，二氧化碳浓度从未超过百万分之300。这与今天的百万分之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变暖期间增加了气体的排放，从而成为气候变化的放大因素。这种放大预计将在未来发生，增加人类产生的气体负担。南极冰核将在这些先前发现的基础上，通过扩大气体系列，首次包括那些在过去40,000年里既收集热量又消耗臭氧的有效痕量气体。目前关于南极冰芯中的惰性气体和甲烷的项目将以前所未有的精度改进这一关键记录的年代测定，以便可以利用事件的相对时间来了解微量气体的产生和破坏以及由此产生的气候变化放大的机制。最终，这些信息将为在我们快速变化的大气背景下对未来大气化学净化机制和气候的预测提供信息。该奖项还让年轻人对发现和极地研究感到兴奋，有助于培养下一代科学家和教育工作者。培养研究生、青年研究员(比泽特)，培养技师，将为国家增添S的人力资源基础。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Ar同位素比率)和甲烷，并结合下一代FIRN致密模型，该模型处理空气滞留的随机性质和杂质对致密化的作用。该项目解决了限制气体年代学准确性的科学理解上的根本差距，特别是对冰芯d15N的控制以及分层和杂质在降雪致密化中可能发挥的作用缺乏了解。这些差距将通过研究深核地点现代降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降雪空气泵实验，该实验紧密地将从同一钻孔获得的降雪结构特性的测量放在一起。该项目将测试由降雪空气d15N、二氧化碳和甲烷定义的锁定层在结构上受不渗透层控制的假设，而不渗透层又由高杂质含量层产生，在这些层中致密化增强。将使用惰性气体测量来寻找热信号，这将改善温度记录，从而有利于FIRN致密化建模。将测量降雪空气和有限数量的深部岩心样品中的霓虹气、Ar和氧气，以测试冰期分层是否增强，这可以解释上一次冰期观测到的低d15N。利用独立的火山和甲烷与定年冰芯的同步性来创建独立的冰和气体连接点，将对气体年龄-冰期差进行独立的经验估计，以检验积雪致密模型-惰性气体方法计算气体年龄-冰期差的有效性。这些点也将被用来测试南极东部冰芯在最后一次冰川时期出现的异常低的d15N是由于降雪中的深层空气对流，还是由于降雪致密化模型中缺失的杂质相关性。从这些研究中获得的更多的物理认识，再加上新的高精度测量，将导致南极冰芯气体年代学的准确性提高，这将增强这一以气体为导向的冰芯的整体科学回报。这将有助于澄清大气气体变化和温度变化的时间，并有助于了解痕量气体之间的生物地球化学反馈。这些反馈关系到地球系统未来对人为强迫的反应。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，通过寻求更好地理解气体捕获的物理学，该项目旨在对整个冰芯科学产生影响。

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.