Collaborative Research: Reconstructing Carbon-14 of Atmospheric Carbon Monoxide from Law Dome, Antarctica to Constrain Long-Term Hydroxyl Radical Variability

羟基自由基负责清除大多数大气痕量气体，包括污染物和重要的温室气体。 它们被称为“大气的清洁剂”。未来可能发生的反应性痕量气体排放量的巨大变化引起的羟基自由基浓度的变化是不确定的。该项目旨在提供自公元1880年以来大气羟基自由基变化的第一次估计，当时活性痕量气体的人为排放量很小。 这将提高对它们在应对排放量大幅变化时的稳定性的理解。该项目还将调查冰芯是否记录了南半球西风过去的变化。这些风是全球气候系统的一个关键组成部分，对海洋环流和可能对大气二氧化碳浓度有重要影响。 该项目团队将包括三名早期职业科学家，一名博士后研究员，以及研究生和本科生，与资深科学家和澳大利亚合作者合作。 将在东南极洲的Law Dome高堆积沿海地点对约233米深的雪气和浅冰进行取样。在钻探后，将立即从现场的冰芯中提取被困的空气。一氧化碳（14 CO）中的碳-14将在积雪和冰芯空气样本中进行分析。将对冰中的原位宇宙成因14 CO组分进行校正，以重建大气14 CO历史。 这14 CO的历史将被解释与援助的化学运输模型放置在南半球羟基自由基浓度的变化约1880 AD后的第一个观测约束。该项目的另一个组成部分将分析积雪空气和冰芯样本中的氪-86。这些测量将探索冰核氪-86是否作为大气压力变化的代理，以及该代理是否可以用于南极冰核来推断南半球西风的过去运动。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Hydroxyl radicals are responsible for removal of most atmospheric trace gases, including pollutants and important greenhouse gases. They have been called the "detergent of the atmosphere". Changes in hydroxyl radical concentration in response to large changes in reactive trace gas emissions, which may happen in the future, are uncertain. This project aims to provide the first estimates of the variability of atmospheric hydroxyl radicals since about 1880 AD when anthropogenic emissions of reactive trace gases were minimal. This will improve understanding of their stability in response to large changes in emissions. The project will also investigate whether ice cores record past changes in Southern Hemisphere westerly winds. These winds are a key component of the global climate system, and have an important influence on ocean circulation and possibly on atmospheric carbon dioxide concentrations. The project team will include three early career scientists, a postdoctoral researcher, and graduate and undergraduate students, working in collaboration with senior scientists and Australian collaborators. Firn air and shallow ice to a depth of about 233 m will be sampled at the Law Dome high-accumulation coastal site in East Antarctica. Trapped air will be extracted from the ice cores on site immediately after drilling. Carbon-14 of carbon monoxide (14CO) will be analyzed in firn and ice-core air samples. Corrections will be made for the in situ cosmogenic 14CO component in the ice, allowing for the atmospheric 14CO history to be reconstructed. This 14CO history will be interpreted with the aid of a chemistry-transport model to place the first observational constraints on the variability of Southern Hemisphere hydroxyl radical concentration after about 1880 AD. An additional component of the project will analyze Krypton-86 in the firn-air and ice-core samples. These measurements will explore whether ice-core Krypton-86 acts as a proxy for barometric pressure variability, and whether this proxy can be used in Antarctic ice cores to infer past movement of the Southern Hemisphere westerly winds.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.