Collaborative Research: Investigating the Rate of Potential Biological in Situ Gas Production of CO and CH4 in Arctic Ice

从极地冰芯中得到的大气气体记录是气候变化科学的基石。该项目的首要目标是开发和应用对北极甲烷和一氧化碳高时间分辨率记录的新理解。甲烷是一种强大的温室气体，一氧化碳与包括二氧化碳在内的其他温室气体的大气寿命有关。因此，发展这两种气体的可靠记录对于了解过去和未来的大气化学和辐射强迫是重要的。北极冰芯中一氧化碳的高深度分辨率记录，以及较小程度上的甲烷，显示了人们知之甚少的非大气异常的证据。这种异常现象的一个潜在来源是冰内的生物活动。微生物可以在远低于冰点的温度下活跃，冰芯在测量前储存或运输时，从冰川和冰盖中提取冰后，会受到相对温暖的温度。特殊的样品处理方案将用于评估收集后冰温度对甲烷和一氧化碳产生的影响，并有可能开发近几个世纪以来没有任何人工制品的甲烷和一氧化碳记录。资金将支持早期职业研究者、研究生和本科生，他们将参与实地工作、实验室分析和数据解释。研究人员将包括来自代表性不足群体的本科生，以促进地球科学的多样性。公众宣传将通过公开讲座、实验室参观和媒体互动来实现。该项目的具体目标是：(1)调查北极冰芯中温度依赖的一氧化碳和甲烷原位生物生产的速率和时间；(2)在没有原位生产人工制品的情况下，开发近几个世纪以来大气一氧化碳和甲烷的记录；(3)确定冰杂质浓度和微生物群落结构在原位天然气生产中的作用。为了实现这些目标，将使用大直径蓝冰钻在格陵兰的Summit收集150米的冰芯。为了实现目标(1)，将在野外对来自12米长的岩心剖面的八个平行纵向样本进行一氧化碳和甲烷的连续测量，不同的样本将在远低于-31°C的峰顶冰盖温度到远高于-26°C的细胞玻璃化温度的温度范围内持续储存和监测。对于目标(2)，这两种气体的测量将在提取后一直保持在-40°C的冰面上进行。为了实现目标(3)，整个冰芯的一部分将被送回美国进行微生物分析，使用一个完善的、由美国国家科学基金会资助的连续冰芯分析系统对一系列元素和化学物质进行测量，并对一氧化碳和甲烷进行连续测量，以补充现场测量。微生物学分析将对具有高和低原位气体异常特征的冰样品进行分析，以确定存在哪些微生物可能负责产生观察到的气体伪像。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Atmospheric gas records developed from polar ice cores are cornerstones of climate change science. The overarching goal of this project is to develop and apply new understanding of high-time-resolution Arctic records of methane and carbon monoxide. Methane is a powerful greenhouse gas and carbon monoxide is linked to the atmospheric lifetime of other greenhouse gases including carbon dioxide. Thus, developing reliable records of both gases is important for understanding past and future atmospheric chemistry and radiative forcing. High-depth-resolution records of carbon monoxide, and to a lesser extent methane, in Arctic ice cores show evidence of non-atmospheric anomalies that are poorly understood. One potential source of such anomalies is biological activity within the ice. Microbes can be active at temperatures well below freezing, and ice cores are subjected to relatively warm temperatures after the ice is extracted from glaciers and ice sheets while they are stored or transported prior to measurement. Special sample handling protocols will be used to evaluate the effects of post-collection ice temperature on methane and carbon monoxide production, and potentially allow development of methane and carbon monoxide records over recent centuries that are free from any artifacts. Funding will support early career investigators, graduate students and undergraduate students who will be involved in field work, laboratory analysis, and data interpretation. The investigators will involve undergraduates from underrepresented groups to foster diversity in earth sciences. Public outreach will be achieved through public lectures, lab tours, and media interactions. The specific goals of this project are to (1) investigate the rate and timing of temperature-dependent in situ biological production of carbon monoxide and methane in an Arctic ice core, (2) develop records of atmospheric carbon monoxide and methane spanning recent centuries that are free of in situ production artifacts, and (3) determine the roles that ice impurity concentration and microbial community structure play in situ gas production. To accomplish these goals, a 150-meter ice core will be collected at Summit, Greenland using the large-diameter Blue Ice Drill. To address goal (1), successive measurements of carbon monoxide and methane will be made in the field on eight parallel longitudinal samples from a 12 meter-long section of the core, with the different samples consistently stored and monitored at temperatures ranging from well below the -31 °C ice sheet temperature at Summit to well above the -26 °C cell vitrification temperature where cellular metabolism is possible. For goal (2), measurements of these two gases will be made in the field on ice that has been kept consistently at -40 °C after extraction. For goal (3), a portion of the entire ice core will be returned to the U.S. for microbial analyses, measurements of a range of elements and chemical species using a well-established, NSF-funded continuous ice core analytical system, and continuous carbon monoxide and methane measurements to complement the field measurements. Microbiological analysis will be conducted on ice samples characterized by high and low in situ gas anomalies to determine what microbes are present that may be responsible for creating the observed gas artifacts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.