3D climate modeling of close-in land planets: Circulation patterns, climate moist bistability and habitability

By J. Leconte, Francois Forget, B. Charnay, R. Wordsworth, F. Selsis, Ehouarn Millour. 2013

227 citations recorded by the source corpus.

The inner edge of the classical habitable zone is often defined by the critical flux needed to trigger the runaway greenhouse instability. This 1D notion of a critical flux, however, may not be so relevant for inhomogeneously irradiated planets, or when the water content is limited (land planets). Here, based on results from our 3D global climate model, we find that the circulation pattern can shift from super-rotation to stellar/anti stellar circulation when the equatorial Rossby deformation radius significantly exceeds the planetary radius. Using analytical and numerical arguments, we also demonstrate the presence of systematic biases between mean surface temperatures or temperature profiles predicted from either 1D or 3D simulations. Including a complete modeling of the water cycle, we further demonstrate that for land planets closer than the inner edge of the classical habitable zone, two stable climate regimes can exist. One is the classical runaway state, and the other is a collapsed state where water is captured in permanent cold traps. We identify this "moist" bistability as the result of a competition between the greenhouse effect of water vapor and its condensation. We also present synthetic spectra showing the observable signature of these two states. Taking the example of two prototype planets in this regime, namely Gl581c and HD85512b, we argue that they could accumulate a significant amount of water ice at their surface. If such a thick ice cap is present, gravity driven ice flows and geothermal flux should come into play to produce long-lived liquid water at the edge and/or bottom of the ice cap. Consequently, the habitability of planets at smaller orbital distance than the inner edge of the classical habitable zone cannot be ruled out. Transiting planets in this regime represent promising targets for upcoming observatories like EChO and JWST.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, background): “Differences among climate models exist, particularly for exoplanetary problems that push the boundaries of these originally Earth-centric codes (e.g., Leconte et al. 2013b; Wolf & Toon 2015; Popp et al. 2016).”
Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets (2017, background): “…= 2000 J m−2 K−1 s− 1 2 ) or an ocean (Iocean = 20000 J m−2 K−1 s− 1 2 to take into account the Article number, page 2 of 23 efficient vertical mixing in the first tens of meter of the ocean, as previously done in Leconte et al. (2013a) and Charnay et al. (2013)) depending on the assumed surface.”
STABILIZING CLOUD FEEDBACK DRAMATICALLY EXPANDS THE HABITABLE ZONE OF TIDALLY LOCKED PLANETS (2013, background): “…planetary radius is very large, then the Rossby deformation radius is smaller than the planetary radius and the atmospheric circulation is in the rapidly-rotating regime (Edson et al. 2011; Showman et al. 2013; Leconte et al. 2013), which results in concentrated convection and fewer dayside clouds.”
Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1 (2016, background): “However, this can be avoided if the atmosphere is dense enough to efficient redistribute heat (e.g., Leconte et al. 2013).”
The habitability of Proxima Centauri b II. Possible climates and Observability (2016, methodology): “= 0.123 M ), defined as the range of orbital distances within which a planet can possibly maintain liquid water on its surface (Kasting et al. 1993; Kopparapu et al. 2013; Leconte et al. 2013a; Yang et al. 2013; Kopparapu et al. 2014, 2016).”
The Cosmic Shoreline: The Evidence that Escape Determines which Planets Have Atmospheres, and what this May Mean for Proxima Centauri B (2017, background): “GCM-based estimates of the onset of the runaway range between 1.1 to 1.7 solar constants, with details of cloud structure and cloud physics and planetary rotation responsible for much of the variance (Abe et al. 2011; Yang et al. 2013; Leconte et al. 2013a,b; Wolf and Toon 2015; Way et al. 2016).”
Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs (2017, background): “Furthermore, Wolf & Toon (2015) found comparable stratospheric temperatures (always 150 K) to Leconte et al. (2013b) at low surface temperatures, but at high surface temperatures they found much warmer (up to ∼210 K) stratospheric temperatures and correspondingly higher stratospheric H O2 mixing…”
STRONG DEPENDENCE OF THE INNER EDGE OF THE HABITABLE ZONE ON PLANETARY ROTATION RATE (2014, methodology): “Another interesting difference is that the cloud feedback near the runaway greenhouse threshold appears to be negative for tidally locked planets (Yang et al. 2013) and positive for rapidly rotating planets (Leconte et al. 2013b; Wolf & Toon 2014)2.”
WATER LOSS FROM TERRESTRIAL PLANETS WITH CO2-RICH ATMOSPHERES (2013, unknown): “…et al. (2013) did perform some calculations where the stratospheric temperature was varied, but only in the limited context of investigating the habitability of dry “Dune” planets with low H 2 O inventories orbiting close to their host stars, following Abe et al. (2011) and Leconte et al. (2013).”
How to Characterize Habitable Worlds and Signs of Life (2017, methodology): “Table 2 shows the constants to derive the stellar flux at the HZ limits valid for Teff between 2,600 and 10,000 K: The inner boundaries of the empirical HZ (recent Venus, or RV) as well as an alternative inner edge limit for 3D GCMs (Leconte et al. 2013a) and the outer limits (early Mars).”