The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

Paris, Philip von; Selsis, F.; Kitzmann, Daniel; Rauer, H.

doi:10.1089/ast.2013.0993

Cited by 29 publications

(31 citation statements)

References 46 publications

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“…Low mass stars have a redder spectrum and this changes the albedo of the ice and snow (Joshi & Haberle 2012;von Paris et al 2013). Taking this phenomenon into account would radically change the ice-albedo feedback, so that for redder objects it would not be able to drive the planets into a glaciation state (as we showed here for planets with high eccentricities around a L = 10 −2 L star).…”

Section: Discussionmentioning

confidence: 78%

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Bolmont

Libert

Leconte

et al. 2016

A&A

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Unlike the Earth, which has a small orbital eccentricity, some exoplanets discovered in the insolation habitable zone (HZ) have high orbital eccentricities (e.g., up to an eccentricity of ∼0.97 for HD 20782 b). This raises the question of whether these planets have surface conditions favorable to liquid water. In order to assess the habitability of an eccentric planet, the mean flux approximation is often used. It states that a planet on an eccentric orbit is called habitable if it receives on average a flux compatible with the presence of surface liquid water. However, because the planets experience important insolation variations over one orbit and even spend some time outside the HZ for high eccentricities, the question of their habitability might not be as straightforward. We performed a set of simulations using the global climate model LMDZ to explore the limits of the mean flux approximation when varying the luminosity of the host star and the eccentricity of the planet. We computed the climate of tidally locked ocean covered planets with orbital eccentricity from 0 to 0.9 receiving a mean flux equal to Earth's. These planets are found around stars of luminosity ranging from 1 L to 10 −4 L . We use a definition of habitability based on the presence of surface liquid water, and find that most of the planets considered can sustain surface liquid water on the dayside with an ice cap on the nightside. However, for high eccentricity and high luminosity, planets cannot sustain surface liquid water during the whole orbital period. They completely freeze at apoastron and when approaching periastron an ocean appears around the substellar point. We conclude that the higher the eccentricity and the higher the luminosity of the star, the less reliable the mean flux approximation.

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Section: Discussionmentioning

confidence: 78%

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Bolmont

Libert

Leconte

et al. 2016

A&A

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“…This would lead to low water vapor saturation pressures, regardless of which relative humidity profile is assumed (see below). Furthermore, for the variation in surface albedo we expect a smaller impact as for the scenarios discussed here, since, to reach habitable surface temperatures at the outer edge of the habitable zone, high amounts of CO 2 are required that mask the surface albedo, as shown by Shields et al (2013) and von Paris et al (2013). As expected, the largest orbital distances for habitable surface conditions are found for the Earthlike planet when assuming the lowest surface albedo of 0.07 and a high relative humidity (fully saturated atmosphere, corresponding to the highest amount of greenhouse gases in the considered scenarios).…”

Section: Resultsmentioning

confidence: 89%

Assessing the habitability of planets with Earth-like atmospheres with 1D and 3D climate modeling

Godolt

Grenfell

Kitzmann³

et al. 2016

A&A

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Context. The habitable zone (HZ) describes the range of orbital distances around a star where the existence of liquid water on the surface of an Earth-like planet is in principle possible. The applicability of one-dimensional (1D) climate models for the estimation of the HZ boundaries has been questioned by recent three-dimensional (3D) climate studies. While 3D studies can calculate the water vapor, ice albedo, and cloud feedback self-consistently and therefore allow for a deeper understanding and the identification of relevant climate processes, 1D model studies rely on fewer model assumptions and can be more easily applied to the large parameter space possible for extrasolar planets. Aims. We evaluate the applicability of 1D climate models to estimate the potential habitability of Earth-like extrasolar planets by comparing our 1D model results to those of 3D climate studies in the literature. We vary the two important planetary properties, surface albedo and relative humidity, in the 1D model. These depend on climate feedbacks that are not treated self-consistently in most 1D models.Methods. We applied a cloud-free 1D radiative-convective climate model to calculate the climate of Earth-like planets around different types of main-sequence stars with varying surface albedo and relative humidity profile. We compared the results to those of 3D model calculations available in the literature and investigated to what extent the 1D model can approximate the surface temperatures calculated by the 3D models. Results. The 1D parameter study results in a large range of climates possible for an Earth-sized planet with an Earth-like atmosphere and water reservoir at a certain stellar insolation. At some stellar insolations the full spectrum of climate states could be realized, i.e., uninhabitable conditions due to surface temperatures that are too high or too low as well as habitable surface conditions, depending only on the relative humidity and surface albedo assumed. When treating the surface albedo and the relative humidity profile as parameters in 1D model studies and using the habitability constraints found by recent 3D modeling studies, the same conclusions about the potential habitability of a planet can be drawn as from 3D model calculations.

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“…The warming caused by atmospheric CO 2 and water vapor absorbing strongly in the near-IR, where M dwarfs emit strongly, has been established for some time, based on earlier work (Kasting et al, 1993;Selsis et al, 2007). And recent studies have continued to explore the effect of stellar SED on the vertical temperature structure of an orbiting planet's atmosphere, and its resulting climate (Shields et al, 2013;von Paris et al, 2013;Godolt et al, 2015). What has only recently emerged is an understanding of the influence on climate of the interaction between the SED of an M-dwarf host star and the icy and snowy surfaces of an orbiting planet.…”

Section: Radiative Effectsmentioning

confidence: 99%

“…As a result, the ice-Albedo feedback mechanism, which is largely cooling on the Earth, may be suppressed on M-dwarf planets (Joshi & Haberle, 2012). Comprehensive follow-up studies of this phenomenon carried out with a hierarchy of radiative transfer and climate models found that lower-mass planets exhibit warmer climates than planets orbiting hotter, more luminous stars at equivalent stellar flux distances (Shields et al, 2013;von Paris et al, 2013). M-dwarf planets appear less susceptible to snowball states, requiring a larger decrease in instellation for global glaciation (Shields et al, 2013).…”

Section: Radiative Effectsmentioning

confidence: 99%

“…However, if an active carbonate-silicate cycle exists on these planets, where CO 2 increases in the atmosphere as the silicate weathering rate decreases due to lower temperatures (Walker et al, 1981), high CO 2 would be expected to build up in a planet's atmosphere at farther distances from its star. Additional work done with computer models found that a planet's sensitivity to the ice-Albedo effect depends on atmospheric composition and surface pressure, and that for dense CO 2 atmospheres, atmospheric properties rather than surface properties dominate the planetary energy balance and radiation budget (Shields et al, 2013;von Paris et al, 2013). Ultimately, the outer edge of the habitable zone for M dwarfs largely remains unaffected by the spectral dependence of snow and ice Albedo, as high atmospheric CO 2 would likely mask the planet's climate sensitivity to the surface, and to the ice-Albedo effect.…”

Section: Radiative Effectsmentioning

confidence: 99%

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The habitability of planets orbiting M-dwarf stars

2016

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The prospects for the habitability of M-dwarf planets have long been debated, due to key differences between the unique stellar and planetary environments around these low-mass stars, as compared to hotter, more luminous Sunlike stars. Over the past decade, significant progress has been made by both space-and ground-based observatories to measure the likelihood of small planets to orbit in the habitable zones of M-dwarf stars. We now know that most M dwarfs are hosts to closely-packed planetary systems characterized by a paucity of Jupiter-mass planets and the presence of multiple rocky planets, with roughly a third of these rocky M-dwarf planets orbiting within the habitable zone, where they have the potential to support liquid water on their surfaces. Theoretical studies have also quantified the effect on climate and habitability of the interaction between the spectral energy distribution of M-dwarf stars and the atmospheres and surfaces of their planets. These and other recent results fill in knowledge gaps that existed at the time of the previous overview papers published nearly a decade ago by Tarter et al. (2007) and Scalo et al. (2007). In this review we provide a comprehensive picture of the current knowledge of M-dwarf planet occurrence and habitability based on work done in this area over the past decade, and summarize future directions planned in this quickly evolving field.

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The Dependence of the Ice-Albedo Feedback on Atmospheric Properties

Cited by 29 publications

References 46 publications

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Habitability of planets on eccentric orbits: Limits of the mean flux approximation

Assessing the habitability of planets with Earth-like atmospheres with 1D and 3D climate modeling

The habitability of planets orbiting M-dwarf stars

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