The role of sea-ice albedo in the climate of slowly rotating aquaplanets

Salameh, Josiane; Popp, Max; Marotzke, Jochem

doi:10.1007/s00382-017-3548-6

Cited by 20 publications

(25 citation statements)

References 42 publications

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“…It is important to note that diurnal cycle effects are neglected, and although they might become important for short orbital periods, they are out of the scope of this study. Salameh et al (2018) showed that diurnal effects on the surface temperature become important when the ratio between the orbital period (ω) and the rotation period (P Ω ) is ω/P Ω ≈ 10. In this case, ω/P Ω = 45, so neglecting diurnal effects is justified.…”

Section: Surface Temperature Responsementioning

confidence: 99%

Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to Changes in Orbital, Rotational, and Radiative Timescales

Guendelman

Kaspi

2019

ApJ

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Thousands of exoplanets have been detected to date, and with future planned missions this tally will increase. Understanding the climate dependence on the planetary parameters is vital for the study of terrestrial exoplanet habitability. Using an idealized general circulation model with a seasonal cycle, we study the seasonal response of the surface temperature and Hadley circulation to changes in the orbital, rotational and radiative timescales. Analyzing the climate's seasonal response to variations in these timescales, we find a regime transition between planets controlled by the annual mean insolation to planets controlled by the seasonal variability depending on the relation between the length of the orbital period, obliquity and radiative timescale. Consequently, planets with obliquity greater than 54 • and short orbital period will have a minimum surface temperature at the equator. We also show that in specific configurations, mainly high atmospheric mass and short orbital periods, high obliquity planets can still have an equable climate. Based on the model results, we suggest an empirical power law for the ascending and descending branches of the Hadley circulation and its strength. These power laws show that the Hadley circulation becomes wider and stronger by increasing the obliquity and orbital period or by decreasing the atmospheric mass and rotation rate. Consistent with previous studies, we show that the rotation rate plays an essential role in dictating the width of the Hadley circulation.

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Section: Surface Temperature Responsementioning

confidence: 99%

Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to Changes in Orbital, Rotational, and Radiative Timescales

Guendelman

Kaspi

2019

ApJ

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“…Second, it shows that if the top-of-atmosphere ice/ocean albedo contrast is smaller, a planet is less likely to experience a snowball bifurcation (C * increases). This is important because tidally locked terrestrial planets should have massive cloud decks on their day sides (Yang et al 2013;Way et al 2015;Kopparapu et al 2016;Salameh et al 2017). This should tend to increase the top-ofatmosphere albedo over open ocean regions, making the effective albedo contrast between ocean and ice/snow smaller.…”

Section: Tidally Locked Planetmentioning

confidence: 99%

No Snowball on Habitable Tidally Locked Planets

Checlair

Menou

Abbot

2017

ApJ

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The TRAPPIST-1, Proxima Centauri, and LHS 1140 systems are the most exciting prospects for future follow-up observations of potentially inhabited planets. All orbit nearby M-stars and are likely tidally locked in 1:1 spinorbit states, which motivates the consideration of the effects that tidal locking might have on planetary habitability. On Earth, periods of global glaciation (snowballs) may have been essential for habitability and remote signs of life (biosignatures) because they are correlated with increases in the complexity of life and in the atmospheric oxygen concentration. In this paper we investigate the snowball bifurcation (sudden onset of global glaciation) on tidally locked planets using both an energy balance model and an intermediate-complexity global climate model. We show that tidally locked planets are unlikely to exhibit a snowball bifurcation as a direct result of the spatial pattern of insolation they receive. Instead they will smoothly transition from partial to complete ice coverage and back. A major implication of this work is that tidally locked planets with an active carbon cycle should not be found in a snowball state. Moreover, this work implies that tidally locked planets near the outer edge of the habitable zone with low CO 2 outgassing fluxes will equilibrate with a small unglaciated substellar region rather than cycling between warm and snowball states. More work is needed to determine how the lack of a snowball bifurcation might affect the development of life on a tidally locked planet.

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“…It is also useful in determining the occurrence of potentially habitable planets in our galaxy, as was done with Kepler data. Several groups have studied the limits of the mainsequence HZ (Kasting et al 1993;Pierrehumbert & Gaidos 2011;Kopparapu et al 2013;Leconte et al 2013a;Yang et al 2013;Barnes et al 2013;Zsom et al 2013;Kopparapu et al 2014;Wolf & Toon 2014;Yang et al 2014a;Way et al 2015;Wolf & Toon 2015;Leconte et al 2015;Godolt et al 2015;Kopparapu et al 2016;Haqq-Misra et al 2016;Ramirez & Kaltenegger 2017;Salameh et al 2017) using both 1-D and 3-D climate models, and corresponding climate transitions that planets undergo at these limits. Many of these models assume water-rich (∼ 1 Earth ocean) planets, which is reasonable if one wants to study the surface habitability of a planet.…”

Section: Introductionmentioning

confidence: 99%

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

Kopparapu

Wolf

Arney

et al. 2017

ApJ

186

269

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Terrestrial planets in the habitable zones (HZs) of low-mass stars and cool dwarfs have received significant scrutiny recently Transit spectroscopy of such planets with JWST represents our best shot at obtaining the spectrum of a habitable planet within the next decade. As these planets are likely tidal-locked, improved 3D numerical simulations of such planetary atmospheres are needed to guide target selection. Here we use a 3-D climate system model, updated with new water-vapor absorption coefficients derived from the HITRAN 2012 database, to study ocean covered planets at the inner edge of the HZ around late-M to mid-K stars (2600K ≤ T ef f ≤ 4500K). Our results indicate that these updated water-vapor coefficients result in significant warming compared to previous studies, so the inner HZ around M-dwarfs is not as close as suggested by earlier work. Assuming synchronously rotating Earth-sized and Earth-massed planets with background 1 bar N 2 atmospheres, we find that planets at the inner -2 -HZ of stars with T ef f > 3000K undergo the classical "moist-greenhouse" (H 2 O mixing ratio > 10 −3 in the stratosphere) at significantly lower surface temperature (∼ 280K) in our 3-D model compared with 1-D climate models (∼ 340K). This implies that some planets around low mass stars can simultaneously undergo water-loss and remain habitable. However, for star with T ef f ≤ 3000K, planets at the inner HZ may directly transition to a runaway state, while bypassing the moist greenhouse water-loss entirely. We analyze transmission spectra of planets in a moist greenhouse regime, and find that there are several prominent H 2 O features, including a broad feature between 5-8 microns, within JWST MIRI instrument range. Thus, relying only upon standard Earth-analog spectra with 24-hour rotation period around M-dwarfs for habitability studies will miss the strong H 2 O features that one would expect to see on synchronously rotating planets around M-dwarf stars, with JWST.

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The role of sea-ice albedo in the climate of slowly rotating aquaplanets

Cited by 20 publications

References 42 publications

Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to Changes in Orbital, Rotational, and Radiative Timescales

Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to Changes in Orbital, Rotational, and Radiative Timescales

No Snowball on Habitable Tidally Locked Planets

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

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