Stable Equatorial Ice Belts at High Obliquity in a Coupled Atmosphere–Ocean Model

Kilic, Cevahir; Lunkeit, Frank; Raible, Christoph C.; Stocker, Thomas F.

doi:10.3847/1538-4357/aad5eb

Cited by 26 publications

(30 citation statements)

References 23 publications

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“…Previous research has found that planets with obliquity ε  54°m ay form an equatorial ice belt since the orbit-averaged instellation is lower at the equator than the poles (Williams & Pollard 2003). That study and others (Kilic et al 2017(Kilic et al , 2018 found that ice belts can form and persist with 3D GCMs, but Ferreira et al (2014) found that ocean heat transport could prevent the formation of an ice belt. Rose et al (2017) used an EBM to map the stable regions of ice formation at different obliquities, assuming a planet on a circular orbit around a Sunlike star.…”

Section: Introductionmentioning

confidence: 78%

The Ice Coverage of Earth-like Planets Orbiting FGK Stars

et al. 2022

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The photometric and spectroscopic signatures of habitable planets orbiting FGK stars may be modulated by surface ice coverage. To estimate its frequency and locations, we simulated the climates of hypothetical planets with a 1D energy balance model and assumed that the planets possess properties similar to modern Earth (mass, geography, atmosphere). We first simulated planets with fixed rotational axes and circular orbits, finding that the vast majority (≳ 90%) of planets with habitable surfaces are free of ice. For planets with partial ice coverage, the parameter space for ice caps (interannual ice located at the poles) is about as large as that for “ice belts” (interannual ice located at the equator), but belts only persist on land. We then performed simulations that mimicked perturbations from other planets by forcing sinusoidal orbital and rotational oscillations over a range of frequencies and amplitudes. We assume initially ice-free surfaces and set the initial eccentricity distribution to mirror known exoplanets, while the initial obliquity distribution matches planet formation predictions, i.e., favoring 90°. For these dynamic cases, we find again that ∼90% of habitable planets are free of surface ice for a range of assumptions for ice’s albedo. Planets orbiting F dwarfs are three times as likely to have ice caps than belts, but for planets orbiting K and G dwarfs ice belts are twice as likely as caps. In some cases, a planet’s surface ice can cycle between the equatorial and polar regions. Future direct imaging surveys of habitable planets may be able to test these predictions.

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Section: Introductionmentioning

confidence: 78%

The Ice Coverage of Earth-like Planets Orbiting FGK Stars

et al. 2022

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“…15c), but the diminished magnitude of the maximum eccentricity reduces its influence upon the Milankovitch cycles. Figure 15b shows the planetary obliquity rises above 55 • for a significant portion of its cycle, which leads to the formation of an ice belt instead of an ice cap (Kilic et al 2018). Figure 15d illustrates this transition, where the equatorial latitudes have a much higher surface temperature for low obliquity and drop to freezing temperatures once the obliquity increases enough.…”

Section: Factors Affecting Milankovitch Cyclesmentioning

confidence: 98%

“…For 𝜖 𝑜 > 60 • , each model produce an ice free planet, which is due to the weak planetary spin-orbit coupling that induces up to a 20 • variation in obliquity on a ∼10,000 year timescale (i.e., secular orbital eccentricity variations). One might expect an ice belt to form if a planet begins at high obliquity (Kilic et al 2018), but the planet's obliquity evolves quickly (within ∼5,000 years) to lower values such that the ice ablation rate matches the accumulation and no significant growth in ice sheets can occur.…”

Section: Ice Fraction and Surface Distributionmentioning

confidence: 99%

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Milankovitch Cycles for a Circumstellar Earth-analog within $α$ Centauri-like Binaries

Quarles,

Li,

Lissauer

2021

Preprint

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An Earth-analog orbiting within the habitable zone of 𝛼 Centauri B was shown to undergo large variations in its obliquity, or axial tilt, which affects the planetary climate by altering the radiative flux for a given latitude (Quarles et al. 2019). We examine the potential implications of these obliquity variations for climate through Milankovitch cycles using an energy balance model with ice sheets. Similar to previous studies, the largest amplitude obliquity variations from spin-orbit resonances induce snowball states within the habitable zone, while moderate variations can allow for persistent ice caps or an ice belt. Particular outcomes for the global ice distribution can depend on the planetary orbit, obliquity, spin precession, binary orbit, and which star the Earth-analog orbits. An Earth-analog with an inclined orbits relative to the binary orbit can periodically transition through several global ice distribution states and risk runaway glaciation when periods of ice caps and an ice belt overlap. When determining the potential habitability for planets in stellar binaries, more care must be taken due to the orbital and spin dynamics.

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“…Silva et al 2017;Wolf et al 2017;Jansen et al 2019). Numerous studies have examined the effects of obliquity on the latitudinal distribution of above-freezing conditions, including how this differs for all-land and all-ocean planets (Abe & Abe-Ouchi 2003;Kilic et al 2018;Colose et al 2019). Heller & Armstrong (2014) discussed properties that might make a planet "superhabitable," i.e., having a greater habitable surface area than Earth: A planet area (volume) greater than Earth's, an optimal distribution of land and ocean, a stellar habitable zone wider than Earth's, or a longer duration of the continuous habitable zone associated with prolonged plate tectonics, other greenhouse gas recycling mechanisms, and magnetic shielding.…”

Section: Introductionmentioning

confidence: 99%

Climates of Warm Earth-like Planets. III. Fractional Habitability from a Water Cycle Perspective

Genio

Way

Kiang

et al. 2019

ApJ

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The habitable fraction of a planet's surface is important for the detectability of surface biosignatures. The extent and distribution of habitable areas is influenced by external parameters that control the planet's climate, atmospheric circulation, and hydrological cycle. We explore these issues using the ROCKE-3D General Circulation Model, focusing on terrestrial water fluxes and thus the potential for the existence of complex life on land. Habitability is examined as a function of insolation and planet rotation for an Earth-like world with zero obliquity and eccentricity orbiting the Sun. We assess fractional habitability using an aridity index that measures the net supply of water to the land. Earth-like planets become "superhabitable" (a larger habitable surface area than Earth) as insolation and day-length increase because their climates become more equable, reminiscent of past warm periods on Earth when complex life was abundant and widespread. The most slowly rotating, most highly irradiated planets, though, occupy a hydrological regime unlike any on Earth, with extremely warm, humid conditions at high latitudes but little rain and subsurface water storage. Clouds increasingly obscure the surface as insolation increases, but visibility improves for modest increases in rotation period. Thus, moderately slowly rotating rocky planets with insolation near or somewhat greater than modern Earth's appear to be promising targets for surface characterization by a future direct imaging mission.

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Stable Equatorial Ice Belts at High Obliquity in a Coupled Atmosphere–Ocean Model

Cited by 26 publications

References 23 publications

The Ice Coverage of Earth-like Planets Orbiting FGK Stars

The Ice Coverage of Earth-like Planets Orbiting FGK Stars

Milankovitch Cycles for a Circumstellar Earth-analog within $α$ Centauri-like Binaries

Climates of Warm Earth-like Planets. III. Fractional Habitability from a Water Cycle Perspective

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