Exploring the ocean and land carbon sinks from Jungfraujoch's carbon dioxide and oxygen observational record

The global carbon budget is a critical system to understand with respect to global temperature change. An accurate carbon budget correctly allocates carbon among Earth's four key reservoirs: fossil fuel reserves, the atmosphere, the ocean, and terrestrial ecosystems. Such budgets allow for the monitoring of the health of the natural global carbon sinks. Both the ocean and land sinks have demonstrated high levels of resilience in the face of increasing anthropogenic carbon emissions and subsequent growth of carbon dioxide (CO₂) in the atmosphere. However, there are signals that these two critical carbon sinks' abilities to sequester carbon are declining.

Observations of CO₂ and oxygen (O₂; in the form of δ(O₂/N₂)) from both in situ analysers and flask sampling activities from the Jungfraujoch high-alpine observatory (3572 m above sea level) in the Swiss Alps will be used to constrain the carbon budget using the O₂-CO₂ partitioning method to illuminate the behaviour of the ocean and land sinks between 2005 and 2025. High-precision measurements of CO₂ and O₂ are useful for partitioning because these two species are intrinsically linked through photosynthesis, respiration, and combustion processes. However, the dissolution of CO₂ into the ocean does not involve O₂, thus allowing for the separation of the ocean and land sinks. The O₂-CO₂ partitioning, along with other observational-based analyses such as the exploration of seasonal amplitudes and potentially isotopic measurements, will be used to shed light on the behaviour of the ocean and land sinks over the past decade purely from observational records, thus offering a validation and verification process for other, generally modelling-based estimates. The possible downstream climate impacts will be discussed.