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| Titel |
Insensitivity of weathering behavior to planetary land fraction and effect on habitability |
| VerfasserIn |
D. S. Abbot, D. Archer, R. T. Pierrehumbert, F. J. Ciesla, J. L. Bean |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058396
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| Zusammenfassung |
| It is likely that an increasing number of terrestrial planets of unknown water content
will soon be discovered in the habitable zone of their stars. Planetary surface land
fraction may, however, influence the functioning of the silicate weathering feedback,
which buffers planetary surface climate against changes in stellar luminosity over
a star’s lifetime. It is therefore worthwhile to consider the effect of land fraction
on the planetary carbon cycle and weathering behavior in a general sense. Here a
low-order model of weathering and climate is developed that includes both continental
silicate weathering and seafloor weathering. This model can be used to gain an
intuitive sense of the behavior of terrestrial planets with different land fractions in
the habitable zone of main-sequence stars as their star’s insolation changes with
time.
It is found that, as long as seafloor weathering is independent of surface temperature,
there can be no weathering feedback on a waterworld. This means that the tenure of a
waterworld in the habitable zone (before it undergoes a moist greenhouse) is likely to be
much shorter than that of a planet with some land fraction. The silicate weathering
feedback, however, is effective even at very low land fractions. A planet with a
land fraction of 0.01 should remain in the habitable zone nearly as long as a planet
with a land fraction of 0.3. Finally, by comparing the timescale for water loss to
space to the weathering timescale, it is found that it is possible for a waterworld to
draw down atmospheric CO2 quickly enough as a moist greenhouse is in progress
to prevent complete loss of all water. This would imply that waterworlds in the
habitable zone of main sequence stars can go through a moist greenhouse stage
and end up as planets like Earth with only partial ocean coverage and a habitable
climate. |
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