On the evolution of the water ocean in the plate-mantle system.

Here, we investigate a possible scenario of surface seawater evolution in the numerical simulations of surface plate motion driven by mantle dynamics, including thermo-chemical convection and water migration, from the early to present-day Earth to constrain the total amount of water in the planetary system. To assess the validity of two hypotheses of the total amount of water inferred from early planetary formation processes and mineral physics, we examine the model sensitivity to the total water in the planetary system (both surface and deep interior) up to 15 ocean masses. To explain the current size of the reservoir of surface seawater, the predictions based on the numerical simulations of hydrous mantle convection suggest that the total amount of water should range from 9 to 12 ocean masses. Incorporating the dense hydrous magnesium silicate (DHMS) with a recently discovered hydrous mineral at lower mantle pressures (phase H) indicates that the physical mechanism of the mantle water cycle would not be significantly influenced, but the water storage region would be expanded in addition to the mantle transition zone. The DHMS solubility field may have a limited impact on the partitioning of water in the Earth’s deep mantle.<graphic></graphic> [ABSTRACT FROM AUTHOR]