Carbon Fluxes in the North Western European Shelf: Trends, Variability and Drivers

Shelf seas play an important role on the global ocean carbon cycle: despite covering only 7% of the global ocean, they are responsible for more than 11% of the uptake of atmospheric CO₂ by the global ocean. Furthermore, they can promote the subduction of carbon in the deeper ocean (the so called continental shelf pump) or the permanent sequestration of carbon in the deep sediments.

They are also an extremely dynamic environment, where local characteristic and variability have a strong impact in determining the intensity (and direction) of the carbon fluxes. On top of all the natural variability, shelf seas are highly impacted by a series of human activities, either by a direct pressure (e.g. trawling) or indirectly through rivers discharge (e.g. eutrophication). All these activities further affect the carbon cycle in shelf seas, although it is not yet understood the direction and the intensity of this impact. Disentangling the effect of human activities from that of global changes is crucial to assess how much of the marine carbon cycle is actually manageable with short term changes in policies.

To address these issues, we implemented the coupled biogeochemical model NEMO-ERSEM to the North Western European Shelf under present day condition, future climate change scenarios and different level of anthropogenic activity.

Our findings highlight how in the long term global changes like warming, increased atmospheric CO₂ and circulation patterns have a much bigger impact on the evolution of the carbon sink than the directly manageable activities like eutrophication and trawling. Furthermore, spatial and temporal variability significantly increased with time becoming even a more critical factor in determining the total carbon uptake from Shelf Sea.