Ocean Dynamics and the Inner Edge of the Habitable Zone for Tidally Locked Terrestrial Planets

Abstract

Recent studies have shown that ocean dynamics can have a significant warming effect on the permanent night sides of 1 to 1 tidally locked terrestrial exoplanets with Earth-like atmospheres and oceans in the middle of the habitable zone. However, the impact of ocean dynamics on the habitable zone's boundaries (inner edge and outer edge) is still unknown and represents a major gap in our understanding of this type of planets. Here we use a coupled atmosphere-ocean global climate model to show that planetary heat transport from the day to night side is dominated by the ocean at lower stellar fluxes and by the atmosphere near the inner edge of the habitable zone. This decrease in oceanic heat transport (OHT) at high stellar fluxes is mainly due to weakening of surface wind stress and a decrease in surface shortwave energy deposition. We further show that ocean dynamics have almost no effect on the observational thermal phase curves of planets near the inner edge of the habitable zone. For planets in the habitable zone's middle range, ocean dynamics moves the hottest spot on the surface eastward from the substellar point. These results suggest that future studies of the inner edge may devote computational resources to atmosphere-only processes such as clouds and radiation. For studies of the middle range and outer edge of the habitable zone, however, fully coupled ocean-atmosphere modeling will be necessary. Note that due to computational resource limitations, only one rotation period (60 Earth days) has been systematically examined in this study; future work varying rotation period as well as other parameters such as atmospheric mass and composition is required.

34 pages, 13 figures, and 1 table

References in corpus (11)

• Was Venus the First Habitable World of our Solar System?
• The habitability of Proxima Centauri b II. Possible climates and Observability
• Alien Maps of an Ocean-Bearing World
• Inverting Phase Functions to Map Exoplanets
• Atmospheric dynamics of Earth-like tidally locked aquaplanets
• Transition to a Moist Greenhouse with CO${}_2$ and solar forcing
• Constraints on Climate and Habitability for Earth-like Exoplanets Determined from a General Circulation Model
• Deciphering thermal phase curves of dry, tidally locked terrestrial planets
• Water Trapping on Tidally Locked Terrestrial Planets Requires Special Conditions
• The formation rate of short gamma-ray bursts and gravitational waves
• A Low-order Model of Water Vapor, Clouds, and Thermal Emission for Tidally Locked Terrestrial Planets

Cited by in corpus (9)

• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• No Snowball on Habitable Tidally Locked Planets with a Dynamic Ocean
• The Effect of Substellar Continent Size on Ocean Dynamics of Proxima Centauri b
• Simulated Phase-dependent Spectra of Terrestrial Aquaplanets in M Dwarf Systems
• Implications of different stellar spectra for the climate of tidally-locked Earth-like exoplanets
• Effects of Radius and Gravity on the Inner Edge of the Habitable Zone
• How does Background Air Pressure Influence the Inner Edge of the Habitable Zone for Tidally Locked Planets in a 3D View?
• Sensitivity of the Atmospheric Water Cycle within the Habitable Zone of a Tidally-Locked, Earth-like Exoplanet
• Effect of Sea-ice Drift on the Onset of Snowball Climate on Rapidly Rotating Aqua-planets