Effect of Sea-ice Drift on the Onset of Snowball Climate on Rapidly Rotating Aqua-planets

Previous studies have shown that sea-ice drift effectively promotes the onset of a globally ice-covered snowball climate for paleo Earth and for tidally locked planets around low-mass stars. Here, we investigate whether sea-ice drift can influence the stellar flux threshold for a snowball climate on...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2020-07, Vol.898 (1), p.L19
Main Authors: Yue, Wenshuo, Yang, Jun
Format: Article
Language:English
Subjects:
Astrobiology
Circular orbits
Climate
Computational methods
Eccentric orbits
Equator
Extrasolar rocky planets
Fluctuations
Flux
Habitable planets
Heat transport
Hydrodynamics
Ice cover
Ice drift
Low mass stars
Ocean dynamics
Perihelions
Planetary rotation
Planets
Sea ice
Sea ice dynamics
Sea ice models
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Summary:Previous studies have shown that sea-ice drift effectively promotes the onset of a globally ice-covered snowball climate for paleo Earth and for tidally locked planets around low-mass stars. Here, we investigate whether sea-ice drift can influence the stellar flux threshold for a snowball climate onset on rapidly rotating aqua-planets around a Sun-like star. Using a fully coupled atmosphere-land-ocean-sea-ice model and turning sea-ice drift on or off, circular orbits with no eccentricity (e = 0) and an eccentric orbit (e = 0.2) are examined. When sea-ice drift is turned off, the stellar flux threshold for the snowball onset is 1250-1275 and 1173-1199 W m−2 for e = 0 and 0.2, respectively. The difference is mainly due to the poleward retreat of sea ice and snow edges when the planet is close to the perihelion in the eccentric orbit. When sea-ice drift is turned on, the respective stellar flux threshold is 1335-1350 and 1250-1276 W m−2. This means that sea-ice drift increases the snowball onset threshold by 80 W m−2 for both e = 0 and 0.2, promoting the formation of a snowball climate state. We further show that oceanic dynamics have a small effect, ≤26 W m−2, on the snowball onset threshold. This is because oceanic heat transport becomes weaker and weaker as the sea-ice edge is approaching the equator. These results imply that sea-ice dynamics are important for the climate of planets close to the outer edge of the habitable zone, but oceanic heat transport is less important.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/aba264