Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Climate instability on tidally locked exoplanets   Feedbacks that can destabilize the climates of synchronously-rotating rocky
planets may arise on planets with strong day-night surface temperature
contrasts. Earth-like habitable-zone (HZ) planets maintain stable surface
liquid water over geological time. This requires equilibrium between the
temperature-dependent rate of greenhouse-gas consumption by weathering,and
greenhouse-gas resupply by other processes. Detected small-radius exoplanets,
and anticipated M-dwarf HZ rocky planets, are expected to be tidally locked. We
investigate two feedbacks that can destabilize climate on tidally-locked
planets. (1) If small changes in pressure alter the temperature distribution
across a planet's surface such that the weathering rate increases when the
pressure decreases, a positive feedback occurs involving increasing weathering
rate near the substellar point, decreasing pressure, and increasing substellar
surface temperature. (2) When decreases in pressure increase the surface area
above the melting point (through reduced advective cooling of the substellar
point), and the corresponding increase in volume of liquid causes net
dissolution of the atmosphere, a further decrease in pressure occurs. We use an
idealized energy balance model to map out the conditions under which these
instabilities may occur. The weathering runaway can shrink the habitable zone,
and cause geologically rapid 10^3-fold pressure shifts within the HZ. Mars may
have undergone a weathering runaway in the past. Substellar dissolution is
usually a negative feedback or weak positive feedback on changes in pressure.
Both instabilities are suppressed if the atmosphere has a high radiative
efficiency. Our results are most relevant for atmospheres that are thin and
have low greenhouse-gas radiative efficiency. These results identify a new
pathway by which HZ planets can undergo rapid climate shifts and become
uninhabitable.

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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph