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| Titel |
An explanation of the 100 kyr ice age cycle using a simple box model |
| VerfasserIn |
A. C. Fowler, R. E. M. Rickaby, E. W. Wolff |
| 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 |
250069126
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| Zusammenfassung |
| We have developed a conceptually simple box model, similar in philosophy to those of
Saltzman, with a view to explaining the 100 kyr period of the most recent ice age signals.
Here we explain in detail how and why the various components of the model have been
constructed, and we show how the model can be analysed in order to explain its
behaviour. We find that the model can explain the 100 kyr cycles as a self-sustaining
oscillation, and in addition we can explain the 40 kyr –100 kyr transition, and indeed
the post-Eocene cooling, through the variation of weathering rate over geologic
time.
The central component of the model is an ocean carbon balance, which receives input
from the weathering of silicates and carbonates, and loses CaCO3 by the burial of calcareous
biomass. It is therefore necessary to also balance calcium and biomass, and thence
phosphorus, which we take to be rate limiting. Charge balance is effected through estimates
of the conservative ions Na+, Cl-, etc. To this ocean chemistry model we add a simple ice
sheet model of the Weertman/Oerlemans/Ghil type, and we allow for rapid deglaciation
through an enhanced wastage rate associated with the growth of proglacial lakes like
Agassiz.
The oscillations which result are due to the interaction of the hysteretic ice sheet growth
(allowing for the elevation-accumulation feedback), and a similar hysteresis in the
proglacial lake volume. The effect of this on the atmospheric carbon is controlled by the
lowering of the carbonate ion which results when the ice sheet meltwater flows into the
ocean. |
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