Habitable Zones & Global Climate

Stable Equatorial Ice Belts at High Obliquity in a Coupled Ocean-atmosphere Model

By Keith Cowing
Press Release
March 28, 2018
Filed under
Stable Equatorial Ice Belts at High Obliquity in a Coupled Ocean-atmosphere Model
Extrasolar planet

Various climate states at high obliquity are realized for a range of stellar irradiance using a dynamical atmosphere-ocean-sea ice climate model in an aquaplanet configuration.

Three stable climate states are obtained that differ in the extent of the sea ice cover. For low values of irradiation the model simulates a Cryoplanet which has a perennial global sea ice cover. By increasing stellar irradiance, transitions occur to an Uncapped Cryoplanet with a perennial equatorial sea ice belt, and eventually to an Aquaplanet with no ice. Using an emulator model we show that the Uncapped Cryoplanet is a robust stable state for a range of irradiation and high obliquities and correct earlier contentions that high-obliquity climate states with an equatorial ice belt are unsustainable.

When the meridional ocean heat flux is strengthened, the parameter range permitting a stable Uncapped Cryoplanet decreases due to melting of equatorial sea ice. Beyond a critical threshold of meridional ocean heat flux, the equatorial ice belt disappears completely. Our results show that perennial equatorial ice cover is a viable climate state of a high-obliquity exoplanet, but a vigorous ocean circulation may render it unstable.

Cevahir Kilic, Frank Lunkeit, Christoph C. Raible, Thomas F. Stocker
(Submitted on 28 Mar 2018)

Comments: 7 pages, 4 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Cite as: arXiv:1803.10751 [astro-ph.EP] (or arXiv:1803.10751v1 [astro-ph.EP] for this version)
Submission history
From: Cevahir Kilic
[v1] Wed, 28 Mar 2018 17:38:30 GMT (869kb,D)

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