Habitable Zones & Global Climate

Transition From Eyeball To Snowball Driven By Sea-ice Drift On Tidally Locked Terrestrial Planets

By Keith Cowing
Press Release
January 3, 2020
Filed under
Transition From Eyeball To Snowball Driven By Sea-ice Drift On Tidally Locked Terrestrial Planets
Snapshots of ice concentrations in 3:2 resonance orbits

Tidally locked terrestrial planets around low-mass stars are the prime targets for future atmospheric characterizations of potentially habitable systems, especially the three nearby ones–Proxima b, TRAPPIST-1e, and LHS 1140b.

Previous studies suggest that if these planets have surface ocean they would be in an eyeball-like climate state: ice-free in the vicinity of the substellar point and ice-covered in the rest regions. However, an important component of the climate system–sea ice dynamics has not been well studied in previous studies. A fundamental question is: would the open ocean be stable against a globally ice-covered snowball state? Here we show that sea-ice drift cools the ocean’s surface when the ice flows to the warmer substellar region and melts through absorbing heat from the ocean and the overlying air.

As a result, the open ocean shrinks and can even disappear when atmospheric greenhouse gases are not much more abundant than on Earth, turning the planet into a snowball state. This occurs for both synchronous rotation and spin-orbit resonances (such as 3 to 2). These results suggest that sea-ice drift strongly reduces the open ocean area and can significantly impact the habitability of tidally locked planets.

Jun Yang, Weiwen Ji, Yaoxuan Zeng
(Submitted on 24 Dec 2019)
Comments: 52 pages, 4 figure in main text, 19 figures and 1 video in SI
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Journal reference: Nature Astronomy 2019
Report number: https://www.nature.com/articles/s41550-019-0883-z
Cite as: arXiv:1912.11377 [astro-ph.EP] (or arXiv:1912.11377v1 [astro-ph.EP] for this version)
Submission history
From: Jun Yang
[v1] Tue, 24 Dec 2019 14:23:40 UTC (7,938 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) πŸ––πŸ»