The Snowball Bifurcation on Tidally Locked Planets

The ice-albedo feedback on rapidly-rotating terrestrial planets in the habitable zone can lead to abrupt transitions(bifurcations) between a warm and a snowball (ice-covered) state, bistability between these states, and hysteresis in planetary climate.This is important for planetary habitability because snowball events may trigger rises in the complexity of life, but could also endangercomplex life that already exists. This raises the question of how the Snowball Bifurcation might work on tidally influenced planets in thehabitable zone orbiting M and K dwarf stars. We investigate this question using analytical theory, an ocean-atmosphere global climatemodel, and an intermediate complexity global climate model coupled to an active carbon cycle. We findthat planets locked in a 1:1 synchronous rotation state are likely to experience a smooth transition to global glaciation rather than abifurcation. This is important because it means that tidally locked planets with an active silicate-weathering feedback loop should nottend to stay in the snowball state (they would just pop out of it if they ever entered it because weathering would go to near zero whileCO2 outgassing would continue).

Speaker: 
Prof. Dorian Abbot (University of Chicago)
Location: 
KIAA 1st meeting room
Time: 
Wed, 2019-05-22 12:00 to 13:00