Ocean Carbon Cycle and Biogeochemistry

The ocean is a very important sink for the anthropogenic CO2 that is emitted into the atmosphere as a result of human activities. Over the last 250 years, the ocean has taken up, on average, about a quarter to a third of the total emissions (Gruber et al., 2023). Anthropogenic CO2 uptake occurs superimposed to a very vigorous exchange of natural CO2 across the air-sea interface, with both natural and anthropogenic CO2 components exhibiting substantial year-to-year to decadal variations. This uptake, while being hugely beneficial for humans, leads to ocean acidification, posing a threat to ocean life, along with other major stressors such as ocean warming and the loss of oxygen.

To study the role of the ocean as a sink for atmospheric CO2 and the associated consequences, we use a range of models and data-driven approaches, including advanced machine learning techniques. We are also leaders in an effort to harmonize model outputs and observational syntheses, through the community-wide RECCAP2 project.

The ocean carbon cycle is intrinsically linked to the cycling of many other biologically relevant elements, primarily orchestrated by phytoplankton. Our studies embrace the full complexity of these intertwined cycles but one of our major foci is nitrogen. The nitrogen cycle sets itself apart through it having strong biologically driven sources and sinks within the ocean, driven by biological nitrogen fixation and a suite of denitrification reactions. Additionally, the nitrogen cycle itself is currently being perturbed by human activities as a result of the massive introduction of industrially fixed nitrogen into the environment.

People involved:

Jens Müller
Luke Gregor
Aline Schneuwly
Nicolas Gruber
Domitille Louchard
Jana Härri