Ocean Tides on Planets Orbiting Low-mass Stars

Abstract Planets in the liquid-water habitable zone of low-mass stars experience large tidal forces, 103 to 104 times those on Earth, due to the small distance between the habitable zone and the host star. Here, for the first time, we perform global ocean tide simulations and show that ocean tides on the planets with large eccentricities can reach 100-1000 m in height and ~10 m s-1 in flow speed. Interactions between tide and bottom topography can induce large energy dissipation, 10-100 W m-2 in global mean. This tidal energy dissipation can strongly accelerate orbital evolution by 1-2 orders, from ~1010 to 109 or 108 Earth years. Through global climate simulations, we further show that this level of tidal dissipation can strongly warm the surface, melt sea ice, and even push the system into a catastrophic runaway greenhouse state, within which the existence of life is impossible. For planets with small eccentricities, the ocean tides are much weaker.