Stabilization of dayside surface liquid water via tropopause cold trapping on arid slowly rotating tidally locked planets

Abstract

Terrestrial-type exoplanets orbiting nearby red dwarf stars (M-dwarfs) are among the best targets for atmospheric characterization and biosignature searches in the near future. Recent evolutionary studies have suggested that terrestrial planets in the habitable zone of M-dwarfs are probably tidally locked and have limited surface water inventories as a result of their host stars' high early luminosities. Several previous climate simulations of such planets have indicated that their remaining water would be transported to the planet's permanent nightside and become trapped as surface ice, leaving the dayside devoid of water. Here we use a three-dimensional general circulation model with a water cycle and accurate radiative transfer scheme to investigate the surface water evolution on slowly rotating tidally locked terrestrial planets with limited surface water inventories. We show that there is a competition for water trapping between the nightside surface and the substellar tropopause in this type of climate system. Although under some conditions the surface water remains trapped on the nightside as an ice sheet, in other cases liquid water stabilizes in a circular area in the substellar region as a wetland. Planets with 1 bar N${}_2$ and atmospheric CO${}_2$ levels greater than 0.1 bar retain stable dayside liquid water, even with very small surface water inventories. Our results reveal the diversity of possible climate states on terrestrial-type exoplanets and highlight the importance of surface liquid water detection techniques for future characterization efforts.

accepted for publication in ApJL

References in corpus (12)

• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• Global modelling of the early Martian climate under a denser CO2 atmosphere: Water cycle and ice evolution
• Inevitability of Plate Tectonics on Super-Earths
• Tidal Locking of Habitable Exoplanets
• Atmospheric dynamics of Earth-like tidally locked aquaplanets
• The Habitable Zones of Pre-Main-Sequence Stars
• Deciphering thermal phase curves of dry, tidally locked terrestrial planets
• Water Trapping on Tidally Locked Terrestrial Planets Requires Special Conditions
• Convection in Condensible-rich Atmospheres
• Dynamics of atmospheres with a non-dilute condensible component
• Sulfate Aerosol Hazes and SO2 Gas as Constraints on Rocky Exoplanets' Surface Liquid Water
• A New Line-By-Line General Circulation Model for Simulations of Diverse Planetary Atmospheres: Initial Validation and Application to the Exoplanet GJ 1132b

Cited by in corpus (14)

• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Atmospheres of Rocky Exoplanets
• Water Condensation Zones around Main Sequence Stars
• Terminator Habitability: the Case for Limited Water Availability on M-dwarf Planets
• Atmospheric Dynamics of a Near Tidally Locked Earth-Size Planet
• Prospects for water vapor detection in the atmospheres of temperate and arid rocky exoplanets around M-dwarf stars
• Multiple moist climate equilibrium states on arid rocky M-dwarf planets: A last-saturation tracer analysis
• Carbon cycle instability for high-$\mathrm{C}{\mathrm{O}}_2$ exoplanets: Implications for habitability
• Lorenz Energy Cycle: Another Way to Understand the Atmospheric Circulation on Tidally Locked Terrestrial Planets
• Potential Surface Ice Distribution on Close-in Terrestrial Exoplanets around M dwarfs
• Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
• An Evolving Cosmic Shoreline and Sandbar Bounding the Rocky Airless Valley
• Retention of surface water on tidally locked rocky planets in the Venus zone around M dwarfs
• Climate uncertainties caused by unknown land distribution on habitable M-Earths