Collaborative Research: P2C2--Drivers for Past Variability in Tropospheric Reactive Halogens: Implications for Climate and Evaluation of Ice Core Proxies

该项目旨在研究活性卤素及其对对流层和平流层化学的影响，特别是对气候的影响。反应性卤素影响大气的氧化能力，从而影响甲烷CH4等微量气体浓度的降低以及大气中臭氧（O3）和气溶胶等短寿命气候强迫因子的丰度。对流层中反应性卤素的前体和/或汇的冰芯观测表明，对流层中反应性卤素的丰度存在人为和气候引起的变化。到目前为止，这对冰芯中的几个古气候代用物产生了无法量化的影响。研究人员计划在全球模型中调查活性卤素丰度对人为排放和气候变化的敏感性，并检查其对气候的潜在反馈。因此，该项目将重点关注以下两个研究问题：(1)在工业前-工业和冰期-间冰期时间尺度上，反应性卤素丰度变化的最大驱动因素是什么；(2)大气和短期气候强迫因子CH4、对流层O3和气溶胶的氧化能力的潜在影响。潜在的更广泛的影响包括，通过具有交互碳模拟的全球气候系统模式中反应化学表征的潜在改进，有可能推进大气化学、气候和古气候学方面的知识和理解。本项目支持研究生在大气化学数值模拟、推广和教育方面的培训。它还通过研讨会和会议，以及研究人员在公众和K12的外展和教育工作，向更广泛的社区传播GEOS-CHEM模型开发的研究成果。

This project aims to examine reactive halogens and their impacts on the chemistry of the troposphere and stratosphere especially with regards to climate. Reactive halogens impact the oxidative capacity of the atmosphere thereby influencing reduced concentrations of trace gases such as methane CH4 and the abundance of short lived climate forcing agents such as ozone (O3) and aerosols in the atmosphere. Ice-core observations of the precursors and/or sinks of reactive halogens in the troposphere suggest both anthropogenic- and climate-induced changes in the abundance of reactive halogens in the troposphere. This has an, as of yet, unquantified impact on several paleoclimate proxies in ice cores.The researchers plan to investigate the sensitivity of reactive halogen abundance to anthropogenic emissions and to climate change in a global model and examine its potential feedbacks on climate. As such, the project will focus on the following two research questions: (1) What are the biggest drivers for changes in the abundance of reactive halogens over the preindustrial-industrial and glacial-interglacial timescales; and (2) What are the potential implications for the oxidizing capacity of the atmosphere and short-lived climate forcing agents CH4, tropospheric O3, and aerosols.The potential broader impacts include the potential to advance knowledge and understanding within atmospheric chemistry and climate and paleoclimatology, via potential improvement of the representation of reactive chemistry in global climate system models with interactive carbon simulation. The project supports the training graduate students in numerical modeling of atmospheric chemistry, outreach and education. It also provides for the wider community dissemination of research results of GEOS-CHEM model development through workshops and meeting sessions and public and K12 outreach and education efforts by the researchers.