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Title: Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback

Abstract

Planetary obliquity determines the meridional distribution of the annual mean insolation. For obliquity exceeding 55°, the weakest insolation occurs at the equator. Stable partial snow and ice cover on such a planet would be in the form of a belt about the equator rather than polar caps. An analytical model of planetary climate is used to investigate the stability of ice caps and ice belts over the widest possible range of parameters. The model is a non-dimensional diffusive Energy Balance Model, representing insolation, heat transport, and ice−albedo feedback on a spherical planet. A complete analytical solution for any obliquity is given and validated against numerical solutions of a seasonal model in the “deep-water” regime of weak seasonal ice line migration. Multiple equilibria and unstable transitions between climate states (ice-free, Snowball, or ice cap/belt) are found over wide swaths of parameter space, including a “Large Ice-Belt Instability” and “Small Ice-Belt Instability” at high obliquity. The Snowball catastrophe is avoided at weak radiative forcing in two different scenarios: weak albedo feedback and inefficient heat transport (favoring stable partial ice cover), or efficient transport at high obliquity (favoring ice-free conditions). From speculative assumptions about distributions of planetary parameters, three-fourths to four-fifths of allmore » planets with stable partial ice cover should be in the form of Earth-like polar caps.« less

Authors:
 [1];  [2];  [3]
  1. Department of Atmospheric and Environmental Sciences, University at Albany (State University of New York), 1400 Washington Avenue, Albany, NY 12222 (United States)
  2. Program in Atmospheres, Oceans, and Climate, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
  3. Department of Atmospheric Sciences, MS 351640, University of Washington, Seattle, WA 98195-1640 (United States)
Publication Date:
OSTI Identifier:
22663185
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALBEDO; ANALYTICAL SOLUTION; DISTRIBUTION; ENERGY BALANCE; EQUATOR; EQUILIBRIUM; FEEDBACK; INSOLATION; INSTABILITY; NUMERICAL SOLUTION; PLANETS; RADIANT HEAT TRANSFER; RADIATIVE FORCING; SPACE; STABILITY; WATER

Citation Formats

Rose, Brian E. J., Cronin, Timothy W., and Bitz, Cecilia M., E-mail: brose@albany.edu. Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8306.
Rose, Brian E. J., Cronin, Timothy W., & Bitz, Cecilia M., E-mail: brose@albany.edu. Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback. United States. doi:10.3847/1538-4357/AA8306.
Rose, Brian E. J., Cronin, Timothy W., and Bitz, Cecilia M., E-mail: brose@albany.edu. Fri . "Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback". United States. doi:10.3847/1538-4357/AA8306.
@article{osti_22663185,
title = {Ice Caps and Ice Belts: The Effects of Obliquity on Ice−Albedo Feedback},
author = {Rose, Brian E. J. and Cronin, Timothy W. and Bitz, Cecilia M., E-mail: brose@albany.edu},
abstractNote = {Planetary obliquity determines the meridional distribution of the annual mean insolation. For obliquity exceeding 55°, the weakest insolation occurs at the equator. Stable partial snow and ice cover on such a planet would be in the form of a belt about the equator rather than polar caps. An analytical model of planetary climate is used to investigate the stability of ice caps and ice belts over the widest possible range of parameters. The model is a non-dimensional diffusive Energy Balance Model, representing insolation, heat transport, and ice−albedo feedback on a spherical planet. A complete analytical solution for any obliquity is given and validated against numerical solutions of a seasonal model in the “deep-water” regime of weak seasonal ice line migration. Multiple equilibria and unstable transitions between climate states (ice-free, Snowball, or ice cap/belt) are found over wide swaths of parameter space, including a “Large Ice-Belt Instability” and “Small Ice-Belt Instability” at high obliquity. The Snowball catastrophe is avoided at weak radiative forcing in two different scenarios: weak albedo feedback and inefficient heat transport (favoring stable partial ice cover), or efficient transport at high obliquity (favoring ice-free conditions). From speculative assumptions about distributions of planetary parameters, three-fourths to four-fifths of all planets with stable partial ice cover should be in the form of Earth-like polar caps.},
doi = {10.3847/1538-4357/AA8306},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 846,
place = {United States},
year = {2017},
month = {9}
}