Exo-Milankovitch Cycles. II. Climates of G-dwarf Planets in Dynamically Hot Systems

Deitrick, Russell; Barnes, Rory; Bitz, Cecilia; Fleming, David; Charnay, Benjamin; Meadows, Victoria; Wilhelm, Caitlyn; Armstrong, John; Quinn, Thomas R. (2018). Exo-Milankovitch Cycles. II. Climates of G-dwarf Planets in Dynamically Hot Systems. The astronomical journal, 155(6), p. 266. American Astronomical Society 10.3847/1538-3881/aac214

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Using an energy balance model with ice sheets, we examine the climate response of an Earth-like planet orbiting a G-dwarf star and experiencing large orbital and obliquity variations. We find that ice caps couple strongly to the orbital forcing, leading to extreme ice ages. In contrast with previous studies, we find that such exo-Milankovitch cycles tend to impair habitability by inducing snowball states within the habitable zone. The large amplitude changes in obliquity and eccentricity cause the ice edge, the lowest latitude extent of the ice caps, to become unstable and grow to the equator. We apply an analytical theory of the ice edge latitude to show that obliquity is the primary driver of the instability. The thermal inertia of the ice sheets and the spectral energy distribution of the G-dwarf star increase the sensitivity of the model to triggering runaway glaciation. Finally, we apply a machine learning algorithm to demonstrate how this technique can be used to extend the power of climate models. This work illustrates the importance of orbital evolution for habitability in dynamically rich planetary systems. We emphasize that as potentially habitable planets are discovered around G-dwarfs, we need to consider orbital dynamics.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Deitrick, Russell


500 Science > 520 Astronomy
500 Science > 530 Physics




American Astronomical Society




Danielle Zemp

Date Deposited:

29 May 2019 16:37

Last Modified:

25 Oct 2019 16:19

Publisher DOI:






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