A groundbreaking community effort led by researchers from Peking University and Université Libre de Bruxelles has revealed that rivers play a much more significant role in the global carbon cycle than previously understood. Using advanced multi-model analysis and an extensive database of river carbon measurements, the research demonstrates that the amount of carbon transported from land to ocean via rivers is 20% higher than reported in the 2021 Intergovernmental Panel on Climate Change (IPCC) assessment.
This increase in carbon flux is critical, as accurate estimates of land-to-ocean carbon transfer are essential for assessing the Earth’s carbon budget and predicting climate change. Rivers, a major conduit for terrestrial carbon, contribute significantly to the carbon cycle by transporting dissolved and particulate organic and inorganic carbon. The new findings offer improved estimates of these transfers, drawing on observations and model data.
The study’s analysis, which included nine models, revealed significant inter-model variability. To address this, the team combined existing model predictions with observational data, applying machine-learning techniques to refine the accuracy. This innovative approach led to a more reliable estimate of global riverine carbon exports, now at 1 PgC per year.
These revised estimates underscore the importance of considering riverine carbon fluxes in models of global carbon uptake and the ocean’s role as a carbon sink. In particular, this revised estimate will allow to better constrain the ocean anthropogenic carbon sink from observations, because they require a correction for the natural CO2 outgassing induced by the land-derived C inputs. The researchers stress that understanding the complex interactions between land, river, and ocean carbon cycles is essential for improving predictions of climate change impacts and shaping future environmental policy.
However, limitations remain, particularly due to observational data’s uneven quality and coverage, especially in regions like Africa and Southeast Asia. The researchers call for more comprehensive data collection in these areas to further enhance the accuracy of carbon flux estimates.
The research, published in Nature Geoscience, represents a significant step forward in refining our understanding of how carbon moves from land to ocean and its implications for the global carbon cycle.
Research Article
Liu, M., Raymond, P.A., Lauerwald, R. ... & Regnier, P. Global riverine land-to-ocean carbon export constrained by observations and multi-model assessment. Nat. Geosci. (2024). https://doi.org/10.1038/s41561-024-01524-z
Research Briefing
An ensemble assessment to improve estimates of land-to-ocean carbon fluxes. Nat. Geosci. (2024). https://doi.org/10.1038/s41561-024-01526-x
More about the land-to-ocean carbon transfer
Mariana Rocha, & Pierre Regnier. (2023). ESM2025 Research Highlight - Modelling carbon fluxes from the land to the open ocean: a journey along inland waters, estuaries, tidal wetlands and the coastal ocean. Zenodo. https://doi.org/10.5281/zenodo.7671172
About the authors
Pierre Regnier and part of his team at the Université Libre de Bruxelle work in our Work package 6/7 (which Pierre co-leads) on the modelling of land-ocean interactions and their integration in Earth system models.
