The influence of a sub-stellar continent on the climate of a tidally-locked exoplanet

TL;DR

This study uses climate modeling to show that a continent at the sub-stellar point on a tidally-locked exoplanet causes global cooling, increases temperature contrasts, and alters atmospheric circulation patterns, affecting habitability.

Contribution

It is the first to analyze the climate impact of a sub-stellar continent on a tidally-locked exoplanet using coupled climate and land surface models.

Findings

Sub-stellar land causes global cooling.

It increases day-night temperature contrasts.

It can induce regime changes in atmospheric circulation.

Abstract

Previous studies have demonstrated that continental carbon-silicate weathering is important to the continued habitability of a terrestrial planet. Despite this, few studies have considered the influence of land on the climate of a tidally-locked planet. In this work we use the Met Office Unified Model, coupled to a land surface model, to investigate the climate effects of a continent located at the sub-stellar point. We choose to use the orbital and planetary parameters of Proxima Centauri B as a template, to allow comparison with the work of others. A region of the surface where $T_{\text{s}} > 273.15\,\text{K}$ is always retained, and previous conclusions on the habitability of Proxima Centauri B remain intact. We find that sub-stellar land causes global cooling, and increases day-night temperature contrasts by limiting heat redistribution. Furthermore, we find that sub-stellar land is able to introduce a regime change in the atmospheric circulation. Specifically, when a continent offset to the east of the sub-stellar point is introduced, we observe the formation of two mid-latitude counterrotating jets, and a substantially weakened equatorial superrotating jet.