Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 2; pp. 629 - 634
• Main Authors: Hu, Yongyun, Yang, Jun
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 14.01.2014; National Acad Sciences
• Subjects: Atmosphere; Atmospheric circulation; Atmospherics; Climate; Climate models; Computer Simulation; Extrasolar planets; Heat transfer; Hot Temperature; Marine; Models, Theoretical; Ocean currents; Ocean temperature; Oceanic climates; Oceanography; Oceans; Oceans and Seas; Physical Sciences; Planets; Radio astronomy; Sea transportation; Sea water; Simulation; Stars, Celestial; planetary climate; exoplanet habitability; superEarth
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1315215111

The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere–ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an “eyeball.” For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs’ habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets.