DEUTSCH

Ocean CO2 measurements: a single sailboat yacht makes a difference

Climate variability Observations Publication

Have you ever wondered how much a single measurement campaign matters when estimating the ocean's carbon sink? In a study published recently in Scientific Reports, Jaqueline Behncke and Peter Landschützer from the Max Planck Institute for Meteorology together with Toste Tanhua from GEOMAR show that data from a single sailboat have a significant impact on estimates of the ocean carbon sink. In the South Polar Ocean, where few measurement campaigns take place, CO2 measurements from a single sailboat make a big difference.

To quantify the ocean's carbon sink, we rely on observations of pCO2, which is the partial pressure of dissolved carbon dioxide in the ocean. These observations are collected from a variety of platforms including ships, buoys, Argo floats and saildrones. However, these platforms cover only a fraction of the remote Antarctic Ocean, leading to large uncertainties in the reconstruction of the CO2 flux between the atmosphere and the ocean.

Since 2018, the sailboat "Seaexplorer - Yacht Club de Monaco" has collected more than 250,000 pCO2 measurements in 129 days (2018-2021), including a circumnavigation of Antarctica (November 2020 - January 2021). Behncke et al. illustrate how much estimates of the marine carbon sink in the North Atlantic and South Polar Oceans can change based on these data. The new observations from the sailboat significantly increase the estimate of regional carbon uptake in the North Atlantic and decrease it in the South Polar Ocean. These changes in the two ocean basins balance each other out, limiting the global effect. In particular, the South Polar Ocean between 40°S and 60°S shows the largest changes in CO2 flux, averaging 20% of the regional mean.
The effect is greatest in the summer. This is when most of the data from the Antarctic circumnavigation (Nov 2020 - Jan 2021) are available. In addition, the effect is strongest in the areas where the yacht crossed the frontal zones of the South Polar Ocean - regions known for their complex biogeochemical processes.

The results remain robust when a potential measurement uncertainty of ± 5 μatm is taken into account. However, when an offset of 5 µatm is considered, the effect is no longer detectable.

Behncke et al. conclude that sailboats fill important gaps in remote ocean regions and should be used as a complementary observation platform to research vessels and Argo floats. They have the potential to improve the reconstruction of the atmosphere-ocean CO2 flux on a larger scale in the future.

Graphic: Difference between the reconstructed CO2 fluxes and the route of the sailing yacht
Figure: Difference between the air-sea CO2 flux estimates based on pCO2 observations in SOCATv2022 including sailboat data and excluding sailboat data between November 2020 and January 2021. The black line represents the sailboat tracks. Credit: Behncke

Original publication

Behncke, J., Landschützer, P., Tanhua, T. (2024). A detectable change in the air-sea CO2 flux estimate from sailboat measurements. Scientific Reports, 14, 3345 (2024). https://www.nature.com/articles/s41598-024-53159-0

Contact

Jacqueline Behncke
Max Planck Institute for Meteorology
jacqueline.behncke@we dont want spammpimet.mpg.de

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