Transition from eyeball to snowball driven by sea-ice drift on tidally locked terrestrial planets

• Main Authors: Yang, Jun, Ji, Weiwen, Zeng, Yaoxuan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: arXiv 2019
• Subjects: Earth and Planetary Astrophysics astro-ph.EP; Atmospheric and Oceanic Physics physics.ao-ph; FOS Physical sciences; Sea ice
• Online Access: https://dx.doi.org/10.48550/arxiv.1912.11377; https://arxiv.org/abs/1912.11377

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. : 52 pages, 4 figure in main text, 19 figures and 1 video in SI