Atmospheric H2 in the Northern Hemisphere over the past Millennium

该项目将分析格陵兰岛顶峰冰芯中的分子氢(H2)，以重建过去一千年来H2的大气变化。这将是工业时代开始之前对过去大气H2的第一次记录。这些结果将揭示古大气H2的自然变异性及其与气候变化的关系。由此产生的数据将为评估自前工业时代以来人类活动如何影响大气H2提供基线。这项研究的结果将为全球评估未来的氢经济将如何影响大气成分和气候提供参考。该项目将为博士后学者和本科生提供培训。研究包括在顶峰钻取一个新的冰芯，从现场样品中提取空气，然后分析氢气、Ne和甲烷。从观测到的H2/Ne比值将推断出古大气中的H2水平，以解释在冷空气捕获过程中的气孔闭合分馏以及在钻井/取样过程中可能的气体损失。这项研究将生成第一个千年尺度的H2大气历史，并检验与中世纪气候异常和小冰期有关的百年尺度变率。预计氢的变化与气候有关，因为主要的损失机制是土壤中的微生物吸收，这是一个对水文条件高度敏感的过程。因此，峰会古大气氢气记录将为我们对全球氢气生物地球化学循环的理解提供新的限制，并对用于评估未来氢气排放的气候敏感性的全球模型进行重要测试。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will analyze molecular hydrogen (H2) in an ice core from Summit, Greenland to reconstruct atmospheric changes in H2 over the past millennium. This will be the first record of past atmospheric H2 prior to the onset of the industrial era. The results will reveal the natural variability in paleo-atmospheric H2 and how it relates to climate change. The resulting data will provide a baseline for assessing how human activities have influenced atmospheric H2 since the preindustrial era. The results of this study will inform global assessments of how the future hydrogen economy will affect atmospheric composition and climate. The project will provide training for a postdoctoral scholar and undergraduate students.The research involves drilling a new ice core at Summit, extracting air from the samples in the field, with subsequent analysis for H2, Ne, and CH4. Paleo-atmospheric levels of H2 will be inferred from the observed H2/Ne ratio to account for pore close-off fractionation during firn air entrapment and possible gas loss during drilling/sampling. This study will generate the first millennial scale atmospheric history of H2 and examine centennial scale variability associated with the Medieval Climate Anomaly and Little Ice Age. Climate-related variability in H2 is expected because the major loss mechanism is microbial uptake in soil, a process that is highly sensitive to hydrological conditions. The Summit paleo-atmospheric H2 record will therefore provide new constraints on our understanding of the global biogeochemical cycling of H2 and an important test for global models used to assess the climate sensitivity of future H2 emissions.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.