Publications

Publications (Foto: J.-R. Lippels / Hereon)

Following publication has been announced by our department Coastal Productivity. For further information please contact Dr Vlad-Alexandru Macovei, author of the publication:

Macovei, V.A., Petersen, W., Brix, H., & Voynova, Y.G. (2021): Reduced ocean carbon sink in the south and central North Sea (2014–2018) revealed from FerryBox observations. Geophysical Research Letters, 48, e2021GL092645, doi:10.1029/2021GL092645

Abstract:

Surface seawater carbon dioxide partial pressure (pCO₂) in the south-central North Sea was measured between 2014 and 2018 using FerryBox-integrated membrane sensors on ships-of-opportunity. Average annual pCO₂ variability was biologically controlled, with thermal effects modulating its amplitude. Deseasonalized winter trends of seawater pCO₂ were positive (4.4 ± 2.0–8.4 ± 2.9 µatm yr⁻¹), biogeochemically driven, stronger than the atmospheric pCO₂ trend, and more pronounced than previous analyses. The trends calculated including all deseasonalized monthly averages were even higher (9.7 ± 2.8–12.2 ± 1.4 µatm yr⁻¹). During our investigation, the southern study area became a stronger source and the northern part became a weaker sink for atmospheric carbon. Overall, average sea-air CO₂ flux in our study area, from the Skagerrak to the Southern Bight (53°N), changed from −0.75 ± 0.61 mmol m⁻² day⁻¹ in 2014 to +0.20 ± 0.96 mmol m⁻² day⁻¹ in 2018.

Plain Language Summary:

Oceans and seas take up one fourth of the carbon dioxide (CO₂) produced by industrial and agricultural activities, and thus lower the amount left in the atmosphere that can contribute to climate change. This uptake of man-made CO₂ can only be understood by taking the natural carbon cycle into account, which is subject to distinct variability. The ability of seawater to remove carbon from the atmosphere can be limited if too much CO₂ is absorbed by the oceans and coastal seas. In this study, we show that between 2014 and 2018, the levels of carbon dioxide have increased faster in the North Sea surface waters than in the atmosphere. As a consequence, regions where atmospheric CO₂ is taken up (carbon sinks) have become less effective and regions where CO₂ is normally released back into the atmosphere (carbon sources) have become more effective. These findings help us understand how carbon cycling in the North Sea works in the context of still increasing atmospheric CO₂ concentrations. It also highlights the importance of sustained observations in dynamic coastal environments such as the North Sea.