Jun Yang1, Yonggang Liu2, Yongyun Hu3, and Dorian S. Abbot1
1 Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA
2 Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544, USA
3 Laboratory for Climate and Atmosphere–Ocean Studies, Department of Atmospheric and Oceanic Sciences, School of Physics,Peking University, Beijing, China
Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld, we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, nightside sea ice remains O(10 m) thick and nightside water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth’s or smaller. Planets with a water complement similar to Earth’s would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete dayside dessiccation. Only planets with a geothermal heat flux lower than Earth’s, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth’s would be susceptible to complete water trapping.
Citation: Yang, J., Y. Liu, Y. Hu, and D. S. Dorian, 2014: Water trapping on tidally locked terrestrial planets requires special conditions. ApJ. Lett., 796: L22. doi:10.1088/2041-8205/796/2/L22.