The persistence of oceans on Earth-like planets: insights from the deep-water cycle

TL;DR

This study models the deep water cycle on super-Earths with plate tectonics, revealing how different convection processes influence surface water retention and planetary habitability over time.

Contribution

It introduces coupled convection and volatile recycling models to analyze water cycle variations on super-Earths, highlighting the impact of convection modes on surface water and habitability.

Findings

Surface oceans are more persistent with single-layer convection.

Smaller planets initially have larger oceans but lose water faster.

Super-Earths may be less habitable early but remain habitable longer.

Abstract

In this paper we present a series of models for the deep water cycle on super-Earths experiencing plate tectonics. The deep water cycle can be modeled through parameterized convection models coupled with a volatile recycling model. The convection of the silicate mantle is linked to the volatile cycle through the water-dependent viscosity. Important differences in surface water content are found for different parameterizations of convection. Surface oceans are smaller and more persistent for single layer convection, rather than convection by boundary layer instability. Smaller planets have initially larger oceans but also return that water to the mantle more rapidly than larger planets. Super-Earths may therefore be less habitable in their early years than smaller planets, but their habitability (assuming stable surface conditions), will persist much longer.