PP024-0005
Energy budget constraints on the runoff and silicate weathering response to changing atmospheric CO2

Thursday, 10 December 2020
Poster
Tyler Kukla, Stanford University, Geological Sciences Department, Stanford, CA, United States, Daniel Enrique Ibarra, University of California Berkeley, Berkeley, CA, United States; Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI, United States, Jeremy K Caves Rugenstein, Max Planck Institute for Meteorology, The Land in the Earth System, Hamburg, Germany; Colorado State University, Geosciences, Fort Collins, United States and Kimberly V Lau, Pennsylvania State University Main Campus, University Park, PA, United States
Abstract:
The silicate weathering feedback—a negative feedback that regulates atmospheric CO2 levels over geologic timescales—is a fundamental control on global climate throughout Earth history. The strength of this feedback is partly determined by how the water cycle responds to changing atmospheric pCO2. Silicate weathering is thought to more tightly control climate when terrestrial runoff (and rock weathering) is more sensitive to changes in pCO2. However, the radiative feedbacks that determine the hydrologic response to pCO2 are not commonly considered in carbon cycle models of the geologic past. Here, we combine a 1-D moist energy balance model of zonal-mean climate with a model of the exogenic carbon cycle and run a series of sensitivity tests to characterize how radiative feedbacks and the silicate weathering feedback are linked. We find that positive radiative feedbacks generally strengthen the silicate weathering feedback, but this effect varies spatially depending on the distribution of continents and the spatial pattern of radiative feedbacks. Our results demonstrate that radiative feedbacks may have played a critical role in long-term climate stability throughout Earth history via their influence over the strength of the silicate weathering feedback.
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