Numerical modeling on global-scale mantle water cycle and its impact on the sea-level change

Abstract

Using numerical modeling of the global-scale mantle water cycle, I have clarified the mechanisms governing the deep Earth water content variations and evaluated their effects on sea-level changes. The following points are found: 1. The temporal variations of water content in the deep Earth are mainly determined by a balance between the ingassing flux from the ocean and the dehydration flux in the mantle wedge. 2. The primary control of ingassing flux comes from the water content of oceanic crust, rather than the style of plate subduction promoted by the free surface boundary condition. 3. The water content of oceanic crust ranges from 0.1 to 1 wt. percent to match the ingassing flux with the inferred one from the geological analysis.Based on the best-fit scenario for the ingassing flux from the ocean to the deep interior, I obtain an average rate of sea-level change of −1 to −1.5 m/Myrs over 1 billion year, which is nearly consistent with the long-term trend of sea-level change estimated from geological and paleontological data (∼−1 m/Myr). Note, however, that the detailed profile of sea-level change in the numerical modeling is difficult to explain the observation one. This underlines the importance of dehydration process in the mantle wedge in understanding the sea-level change resulting from the water budget in the Earth's deep interior over the Earth's history.