COSMOGENIC¹⁴CO FOR ASSESSING THE OH-BASED SELF-CLEANING CAPACITY OF THE TROPOSPHERE

Abstract

An application of radiocarbon (14C) in atmospheric chemistry is reviewed. 14C produced by cosmic neutrons immediately forms 14CO, which reacts with hydroxyl radicals (OH) to 14CO2. By this the distribution and seasonality (the lifetime of 14CO is ∼1 month) of the pivotal atmospheric oxidant OH can be established. 14CO measurement is a complex but unique application which benefitted enormously from the realization of AMS, bearing in mind that 14CO abundance is of the order of merely 10 molecules per cm3 not only provides 14CO an independent measure for the OH based self-cleansing capacity of the troposphere, but also enabled detection of 14C production due to high energy solar protons in 1989. Although its production takes place throughout the atmosphere and does not have the character of a point source, transport processes in the atmosphere affect the distribution of 14CO. Vertical mixing in the troposphere renders gradients in its production rate less critical, but considerable meridional gradients exist. One question has remained open, namely confirmation of calculated 14C production by direct measurement. A new sampling method is proposed. The conclusions are a guide to future work on 14CO in relation to OH and atmospheric transport.

Preindustrial to present-day changes in atmospheric carbon monoxide: agreements and gaps between ice archives and global model reconstructions

“…On the other hand, new measurement-derived CO datasets from high-resolution glacial archives would enable to characterize decadal variations in atmospheric CO, and potentially contribute in constraining further CO evolution of emissions and sinks during the industrial period. Improvement in the assessment of past OH trends (e.g., using innovative proxies such as 14 CO, Brenninkmeijer et al, 2022) would also provide powerful constraints on the past evolution of the main CO sink.…”

Comment on egusphere-2024-653

“…On the other hand, new measurement-derived CO datasets from high-resolution glacial archives would enable to characterize decadal variations in atmospheric CO, and potentially contribute in constraining further CO evolution of emissions and sinks during the industrial period. Improvement in the assessment of past OH trends (e.g., using innovative proxies such as 14 CO, Brenninkmeijer et al, 2022) would also provide powerful constraints on the past evolution of the main CO sink.…”