The Coupled Impacts of Atmospheric Composition and Obliquity on the Climate Dynamics of TRAPPIST-1e

Abstract

Planets in multi-planet systems are expected to migrate inward as near-resonant chains, thus allowing them to undergo gravitational planet-planet interactions and possibly maintain a non-zero obliquity. The TRAPPIST-1 system is in such a near-resonant configuration, making it plausible that TRAPPIST-1e has a non-zero obliquity. In this work, we use the ExoCAM GCM to study the possible climates of TRAPPIST-1e at varying obliquities and atmospheric compositions. We vary obliquity from 0$^\circ$ to 90$^\circ$ and the partial pressure of carbon dioxide from 0.0004 bars (modern Earth-like) to 1 bar. We find that models with a higher obliquity are hotter overall and have a smaller day-night temperature contrast than the lower obliquity models, which is consistent with previous studies. Most significantly, the super-rotating high-altitude jet becomes sub-rotating at high obliquity, thus impacting cloud and surface temperature patterns. As the amount of carbon dioxide increases, the climate of TRAPPIST-1e becomes hotter, cloudier, and less variable. From modeled thermal phase curves, we find that the impact of obliquity could potentially have observable consequences due to the effect of cloud coverage on the outgoing longwave radiation.