Dissolved rock affects CO2 storage in the ocean
The so-called alkalinity, i.e. the acid binding capacity, is created by the weathering of rocks and their entry into the ocean. Increased erosion on land causes an increase in weathering of silicates and carbonates. The researchers identified the factors for more alkalinity using the model: Degree of erosion, area fraction of carbonate, temperatures, catchment size, and soil thickness.
If climate change causes more rain, this promotes the weathering of rocks and thus the erosion of the soil. The dissolved substances reach the sea via rivers. A new model from Helmholtz-Zentrum Hereon shows: The process has an impact on CO2 storage there. If global emissions of greenhouse gases increase sharply, as they have in the past, this increases the ability to bind them. When emissions are low, the opposite happens. The study looked at the factors that favor sequestration capacity and their effects.
“The model we used is a statistical, not a mechanistic model. We applied it to identify the factors influencing alkalinity based on our compiled data set and to describe their interdependencies,” says Nele Lehmann of the Hereon Institute for Carbon Cycles, lead author of the study, which was an international collaboration with the Alfred Wegener Institute Helmholtz-Zentrum für Polar- und Meeresforschung (AWI) and funding from the Deutscher Akademischer Austauschdienst (DAAD). (Source: Hereon Press Release)
Read the complete Hereon Press Release:
==> Stones for the climate
Lehmann, N., Stacke, T., Lehmann, S., Lantuit, H., Gosse, J., Mears, C., Hartmann, J., & Thomas, H. (2023): Alkalinity responses to climate warming destabilise the Earth’s thermostat. Nat Commun 14, 1648 (2023), doi:10.1038/s41467-023-37165-w
Abstract:
Alkalinity generation from rock weathering modulates Earth’s climate at geological time scales. Although lithology is thought to dominantly control alkalinity generation globally, the role of other first-order controls appears elusive. Particularly challenging remains the discrimination of climatic and erosional influences. Based on global observations, here we uncover the role of erosion rate in governing riverine alkalinity, accompanied by areal proportion of carbonate, mean annual temperature, catchment area, and soil regolith thickness. We show that the weathering flux to the ocean will be significantly altered by climate warming as early as 2100, by up to 68% depending on the environmental conditions, constituting a sudden feedback of ocean CO2 sequestration to climate. Interestingly, warming under a low-emissions scenario will reduce terrestrial alkalinity flux from mid-latitudes (–1.6 t(bicarbonate) a−1 km−2) until the end of the century, resulting in a reduction in CO2 sequestration, but an increase (+0.5 t(bicarbonate) a−1 km−2) from mid-latitudes is likely under a high-emissions scenario, yielding an additional CO2 sink.
