Surface exposure constraints on the mantle water budget

Abstract

Abstract Mantle water content estimates range from 0.5 to 15 oceans of water. Its evolution is even more unclear. Rapid degassing during mantle solidification likely released much of the water to the surface, initially flooding Earth. However, evidence for subaerial land from at least 3.5 Ga means that much of this water must have been rapidly cycled back into the mantle. Here, we used a parameterized convection model and hypsometric curve to assess how much water could have been taken into the mantle and still satisfy evidence for subaerial land. Even if only the highest peaks were exposed, the initial ocean must have been less than 1.5 current oceans to explain subaerial exposure throughout most of Earth history. Today, this implies any water in the mantle >0.5 oceans must be primordial and has been isolated from the convecting mantle for most of Earth’s history.