Geochemistry, Mineralogy, Volcanology Editors' Highlights

Watering Down the Mantle

The cooling of planet Earth over time increased the water carrying capacity of the mantle and could have shrunk the oceans.

Source: AGU Advances


By Vincent Salters

Water is an important ingredient that makes our planet habitable, but how much of the Earth’s water resides on or near its surface is a subject of debate. Dong et al. [2021] use present-day ocean volume and the dependence of the water solubility in the mantle minerals on temperature to argue that the present-day ocean volume is likely smaller than it was before.

They used existing experiments to parametrize the amount of water that could be contained in the mantle’s main minerals – bridgmanite, ringwoodite, and wadsleyite. In Earth’s early history mantle temperatures were higher and water was less soluble, thus over time the capacity of the mantle to carry water has increased. Although there are relatively large uncertainties the median estimate for water storage capacity of the mantle in its early history was approximately 0.7 present-day ocean volumes and has increased with a factor of three through time.

Most studies on the flooded portion of the Earth’s surface do not consider the changing water carrying capacity of the mantle. This study suggests that surface ocean volume is not necessarily constant through time and might affect our inferences on crustal growth rates.

Citation: Dong, J., Fischer, R., Stixrude, L., & Lithgow-Bertelloni, C. [2021]. Constraining the volume of Earth’s early oceans with a temperature-dependent 2 mantle water storage capacity model. AGU Advances, 1, e2020AV000323. https://doi.org/10.1029/2020AV000323

—Vincent Salters, Editor, AGU Advances

Text © 2021. The authors. CC BY-NC-ND 3.0
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