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

Jun Yang; Weiwen Ji; Yaoxuan Zeng

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arXiv · 1912.11377

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

Jun Yang·Weiwen Ji·Yaoxuan Zeng

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Abstract

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.

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Jun Yang, Weiwen Ji, Yaoxuan Zeng. 2019-12-24. Transition from eyeball to snowball driven by sea-ice drift on tidally locked terrestrial planets. https://arxiv.org/abs/1912.11377

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