24 Aug 2022
24 Aug 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

Short-term variability of atmospheric helium revealed through a cryo-enrichment method

Benjamin Birner, Eric Morgan, and Ralph F. Keeling Benjamin Birner et al.
  • Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA

Abstract. Tropospheric helium variations are tightly linked to CO2 due to the co-emission of He and CO2 from natural gas burning. Recently Birner et al. (2022) showed that the global consumption of natural gas has measurably increased the He content of the atmosphere. Like CO2, He is also predicted to exhibit complex spatial and temporal variability on shorter time scales, but measurements of these short-term variations are lacking. Here we present the development of an improved gas delivery and purification system for the semi-continuous mass spectrometric measurement of the atmospheric He-to-nitrogen ratio (He/N2). The method replaces the chemical getter used previously by Birner et al. (2021, 2022) to preconcentrate He in an air stream with a cryogenic trap which can be more simply regenerated by heating and which improves the precision of the measurement to 22 per meg in 10 minutes (1σ). Using this “cryo-enrichment” method, we measured the He/N2 ratios in ambient air at La Jolla (California, USA) over 5 weeks in 2022. During this period, He/N2 was strongly correlated with atmospheric CO2 concentrations, as expected from anthropogenic emissions, with a diurnal cycle of 450–500 per meg (max-min) caused by the sea/land breeze pattern of local winds, which modulates the influence of local pollution sources.

Benjamin Birner et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-242', Anonymous Referee #1, 12 Sep 2022
    • AC1: 'Response to reviewers', Benjamin Birner, 10 Jan 2023
  • RC2: 'Comment on amt-2022-242', Anonymous Referee #2, 25 Nov 2022
    • AC1: 'Response to reviewers', Benjamin Birner, 10 Jan 2023

Benjamin Birner et al.

Benjamin Birner et al.


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Short summary
Atmospheric variations of helium (He) and CO2 are strongly linked due to the co-released of both gases from natural gas burning. This implies atmospheric He measurements may be a potentially powerful tool for verifying reported anthropogenic natural gas usage. Here we present the development and initial results of a novel measurement system of atmospheric He that paves the way for establishing a global monitoring network in the future.