∆′17O of Atmospheric CO2 as a tracer for gross fluxes of terrestrial carbon cycle

The amount of CO₂ taken up by plants (gross primary production) is the largest flux in the terrestrial carbon cycle. However, the uncertainty in how much CO₂ plants absorb is larger than annual anthropogenic CO₂ emissions. This means that small changes in plant uptake could drastically alter the carbon balance, making climate predictions more challenging. A better understanding of the terrestrial carbon cycle is essential for predicting future climate conditions and atmospheric CO₂ mole fractions. Stable isotope measurements of CO₂ (δ¹³C and δ¹⁸O) provide valuable insights into the magnitude of CO₂ fluxes between the atmosphere and biosphere.

Recent advancements in measurement techniques have made it possible to measure ∆^′17O in atmospheric CO₂ with high precision. These high-precision measurements provide valuable constraints on terrestrial carbon fluxes that δ¹³C and δ¹⁸O alone could not achieve. This is because ∆^′17O(CO₂) has a known stratospheric source, its variations are much smaller than those of δ¹⁸O, and conventional biogeochemical processes follow a well-defined three-isotope fractionation slope. Additionally, the triple oxygen isotope fractionation slopes for specific processes are independent of source water isotope composition, insensitive to temperature, and process specific.

In this talk, I will discuss the broader applications of ∆^′17O in atmospheric CO₂ research, the challenges associated with high precision ∆^′17O measurements, the latest advancements in measurement techniques, and future implications for studying the terrestrial carbon cycle.