The birth of new ocean crust along the mid-ocean ridge system releases a significant amount of carbon dioxide (CO2) gas as part of the global carbon cycle. By integrating models of mantle convection with petrologic data for carbonate melting, Clerc et al.  predict pervasive carbonate melting beneath old oceanic crust across the ocean basins. Including carbonate melting, the study correctly predicts the thickness of ocean crust produced at ridge axes and suggests that off-axis melting generates an additional volume of melt that is greater than the global volume of all seamounts found away from hot spots. Carbonate melting away from the mid-ocean ridges may contribute an additional flux of CO2 from the mantle comparable to the flux produced by ridge volcanism, suggesting a previously overlooked source of CO2 in the global carbon cycle.
Citation: Clerc, F., Behn, M. D., Parmentier, E. M., & Hirth, G. . Predicting rates and distribution of carbonate melting in oceanic upper mantle: Implications for seismic structure and global carbon cycling. Geophysical Research Letters, 45. https://doi.org/10.1029/2018GL078142
—Steven D. Jacobsen, Editor, Geophysical Research Letters