Effects of ocean tidal mixing on exoplanet climates and habitability

Abstract: Due to their abundance and their observational advantages, red dwarfs offer the best chance of finding habitable planets through sheer numbers. Potentially habitable planets in these systems orbit close to their host star and are therefore subjected to strong tidal forcings. Oceans have an important impact on planetary climate, so understanding their effects is a necessary part of modelling terrestrial exoplanets in order to understand future observations. Taking into account the impact of ocean tides can lead to significant effects on planetary climate.

We have conducted studies with an intermediate complexity coupled atmosphere-ocean general circulation model (FORTE2.0). We investigated the case of non synchronous terrestrial planets in close orbits in the habitable zone of their red host star. By considering scenarios in which the magnitude of tidal forcings varies over a range of values, we were able to determine that key quantities such as temperature and overturning circulation strength are affected by tidal strength.

We examined how climates corresponding to different ocean tidal mixing respond to a decrease of the incoming stellar flux. We found that the outcome of these simulations is highly dependent on the ocean tidal mixing: for a fixed value of stellar flux, a different magnitude of tidally driven mixing can lead to either snowball planets or to temperate worlds.

Earth sciencesMathematics

Audience: researchers in the topic

Fluids and Structures Seminar @ UEA