Feedback Between Climate and Geodynamics Leads to Bistability in Conceptual Models

<title>Abstract</title> <p>Low friction at subduction zones is essential for modern-style plate tectonics, and sediments are widely discussed to help keep this friction low by lubricating the plate interface. This mechanism allows the climate to exert an influence on geodynamics via erosion and sediment flux to subduction zones. Conversely, geodynamics affects climate via carbon outgassing and weathering. However, the resulting feedbacks between climate and geodynamics and their effects on the Earth system remain poorly understood. Here, we present a conceptual model developed to quantify these mechanisms, revealing two stable states: a state with fast tectonic plates and well-lubricated subduction zones and a "slow" state with sediment-depleted subduction zones. We find that supercontinent assembly can lead to bifurcation tipping from the fast into the slow state. Conversely, Snowball Earth events act as a large sediment source, pushing the model from the slow into the fast state. These mechanisms offer plausible mechanisms for the beginning and end of the mid Proterozoic "Boring Billion" period. We furthermore show that the climate of the slow state is likely warmer than that of the fast state, in line with the absence of glaciations during the Boring Billion.</p>