Simulated changes in the carbon cycle using the BICYCLE model due to volcanic outgassing of CO2

Paleo-climate records and geodynamic modelling indicate the existence of complex interactions between glacial sea level changes, volcanic degassing, and atmospheric CO2, which may have modulated the climate system's descent into the last ice age. Between ~85-70 ka, during an interval of decreasing axial tilt, the orbital component in global temperature records gradually declined, while atmospheric CO2, instead of continuing is long-term correlation with Antarctic temperature, remained relatively stable. Based on novel global geodynamic models and the joint interpretation of paleo-proxy data as well as biogeochemical simulations, we show that a sea level fall in this interval caused enhanced pressure-release melting in the uppermost mantle, which may have induced a surge in magma and CO2 fluxes from mid-ocean ridges and oceanic hotspot volcanoes. Our results reveal a hitherto unrecognised negative feedback between glaciation and atmospheric CO2 predominantly controlled by marine volcanism on multi-millennial (suborbital) timescales of ~ 5,000-15,000 years.