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

羟基自由基负责去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“大气中的清洁剂”。未来可能发生的活性痕量气体排放的巨大变化对羟基自由基浓度的变化做出反应是不确定的。该项目旨在提供自公元1880年左右以来大气中羟基自由基可变性的第一次估计，当时人为排放的反应性痕量气体很少。这将提高对它们在应对排放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的过去变化。这些风是全球气候系统的关键组成部分，对海洋环流和大气二氧化碳浓度都有重要影响。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、研究生和本科生，与资深科学家和澳大利亚合作者合作。冰雪空气和约233米深的浅冰将在南极洲东部的洛多姆高堆积沿海地点进行采样。钻井结束后，被困的空气将立即从现场的冰芯中提取出来。碳-14一氧化碳(14CO)将在降雪和冰芯空气样本中进行分析。将对冰中的原地宇宙成因14CO组分进行修正，以便重建大气14CO的历史。这段~(14)CO的历史将借助于化学传输模型来解释，以在大约公元1880年之后对南半球羟基自由基浓度的变异性施加第一个观测约束。该项目的另一个组成部分将分析空气和冰芯样品中的氪-86。这些测量将探索冰芯氪-86是否可以作为气压变化的替代品，以及这个替代品是否可以用于南极冰芯来推断南半球西风的过去移动。这一奖项反映了美国国家科学基金会的法定任务，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。

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.