GENERALIZED MILANKOVITCH CYCLES AND LONG-TERM CLIMATIC HABITABILITY
- Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States)
- Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France)
- Columbia Astrobiology Center, Columbia Astrophysics Lab., Columbia University, 550 West 120th Street, New York, NY 10027 (United States)
Although Earth's orbit is never far from circular, terrestrial planets around other stars might experience substantial changes in eccentricity. Eccentricity variations could lead to climate changes, including possible 'phase transitions' such as the snowball transition (or its opposite). There is evidence that Earth has gone through at least one globally frozen, 'snowball' state in the last billion years, which it is thought to have exited after several million years because global ice-cover shut off the carbonate-silicate cycle, thereby allowing greenhouse gases to build up to sufficient concentration to melt the ice. Due to the positive feedback caused by the high albedo of snow and ice, susceptibility to falling into snowball states might be a generic feature of water-rich planets with the capacity to host life. This paper has two main thrusts. First, we revisit one-dimensional energy balance climate models as tools for probing possible climates of exoplanets, investigate the dimensional scaling of such models, and introduce a simple algorithm to treat the melting of the ice layer on a globally frozen planet. We show that if a terrestrial planet undergoes Milankovitch-like oscillations of eccentricity that are of great enough magnitude, it could melt out of a snowball state. Second, we examine the kinds of variations of eccentricity that a terrestrial planet might experience due to the gravitational influence of a giant companion. We show that a giant planet on a sufficiently eccentric orbit can excite extreme eccentricity oscillations in the orbit of a habitable terrestrial planet. More generally, these two results demonstrate that the long-term habitability (and astronomical observables) of a terrestrial planet can depend on the detailed architecture of the planetary system in which it resides.
- OSTI ID:
- 21464717
- Journal Information:
- Astrophysical Journal, Vol. 721, Issue 2; Other Information: DOI: 10.1088/0004-637X/721/2/1308; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALBEDO
ALGORITHMS
CARBONATES
CLIMATE MODELS
CLIMATES
CLIMATIC CHANGE
ENERGY BALANCE
GREENHOUSE GASES
ICE
ONE-DIMENSIONAL CALCULATIONS
ORBITS
PLANETS
SILICATES
SNOW
ATMOSPHERIC PRECIPITATIONS
CARBON COMPOUNDS
MATHEMATICAL LOGIC
MATHEMATICAL MODELS
OXYGEN COMPOUNDS
SILICON COMPOUNDS