Oceanic Carbon Dynamics and Air-Sea CO2 Fluxes

The ocean is a major regulator of atmospheric carbon dioxide, absorbing roughly a quarter of global CO2 emissions each year. This uptake is governed by a complex interplay of physical and biological processes: the solubility pump, which relies on temperature‐ and pressure‐dependent gas exchange; and the biological pump, in which phytoplankton fix carbon that subsequently sinks into the deep ocean. Regional phenomena such as upwelling and riverine nutrient input further modulate surface carbon chemistry, with areas of intense circulation driving both sources and sinks of CO2. Understanding these dynamics is essential for predicting the ocean’s role in future climate change, informing mitigation strategies and guiding marine management.

Research from Nature Portfolio

Recent work has revealed the dual nature of upwelling systems as both CO2 sources and sinks. In a study of the Benguela Upwelling System, biologically unused preformed nutrients delivered from the Southern Ocean were shown to enhance local carbon uptake by up to 75 Tg C yr−1, compensating a significant fraction of Southern Ocean outgassing. Complementary research on coastal margins has demonstrated that the intensification of the coastal CO2 sink is dominated by biological carbon fixation, driven by climate‐induced changes in circulation (36 %) and increased riverine nutrient loads (23 %), surpassing the contribution of the solubility pump. These advances refine global carbon models and highlight the sensitivity of coastal and upwelling regions to climatic and biogeochemical shifts.

Oceanic Carbon Dynamics and Air-Sea CO2 Fluxes publication trend

The graph below shows the total number of articles in oceanic carbon dynamics and air-sea co2 fluxes across all publications each year (not limited to Nature Index journals).

Technical terms

Preformed nutrients: nutrients present in upwelled water that have not been utilised by local biota and can influence CO2 uptake.

pCO2: the partial pressure of carbon dioxide in seawater, indicating its concentration relative to the atmosphere.

Solubility pump: the physical process by which CO2 dissolves in seawater, with uptake increasing in colder, denser waters.

Biological pump: the biological sequestration of carbon through photosynthesis, followed by sinking and storage in the deep ocean.

Air‐sea CO2 flux: the net transfer of CO2 molecules between the atmosphere and the ocean surface, determining the ocean’s role as a sink or source.

References

1. Regional and global impact of CO2 uptake in the Benguela Upwelling System through preformed nutrients. Nature Communications (2023).
2. Enhanced CO2 uptake of the coastal ocean is dominated by biological carbon fixation. Nature Climate Change (2024).
3. Direct observational evidence of strong CO2 uptake in the Southern Ocean. Science Advances (2024).
4. Improved atmospheric constraints on Southern Ocean CO2 exchange. Proceedings of the National Academy of Sciences of the United States of America (2024).
5. The increasing importance of satellite observations to assess the ocean carbon sink and ocean acidification. Earth-Science Reviews (2024).