OXY-MOBILE: a mobile atmospheric O2 and CO2 community asset for carbon cycle research

The 2020s and 2030s are critical decades for reducing carbon emissions and mitigating the effects of climate change. As societies move towards net-zero emissions, it has never been more important to understand and monitor how carbon dioxide (CO2) enters and leaves the atmosphere, and to understand how different aspects of the carbon cycle, such as land plants, are responding to climate change.

Precise and accurate measurements of atmospheric oxygen (O2), combined with concurrent atmospheric measurements of CO2, are a proven tool for studying and quantifying carbon cycle processes, with a range of emerging science applications that have strong societal relevance, including:

1. Independent verification of CO2 emissions from the combustion of fossil fuels on policy relevant scales.

2. Detecting leaks from carbon capture and storage sites, and verification of atmospheric CO2 removal by carbon capture and storage processing plants.

3. Providing carbon uptake data for natural and managed carbon sinks, such as urban parks and green spaces, so that their natural capital value can be quantified.

4. Separately quantifying CO2 emissions from plant respiration and CO2 uptake by plant photosynthesis, to improve understanding of how respiration and photosynthesis are likely to respond to climate change in different regions and for different types of plants.

With these emerging applications, demand for atmospheric O2 measurements is increasing, but there are significant barriers of access to new users wanting to make these measurements. First, it is much harder to measure atmospheric O2 precisely than most other gases, such as CO2, because O2 is very abundant in the atmosphere (~21% or ~210,000 parts per million), while typical variations are very small (only 1-2 parts per million), so a relatively very high level of precision is required. And second, although commercial O2 analysers are available to purchase, in order to collect atmospheric O2 data at the required...