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| Titel |
Transitions between multiple equilibria of paleo climate: a glimpse in to the dynamics of abrupt climate change |
| VerfasserIn |
David Ferreira, John Marshall, Takamitsu Ito, David McGee, Eduardo Moreno-Chamarro |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148175
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| Publikation (Nr.) |
 EGU/EGU2017-12409.pdf |
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| Zusammenfassung |
| The dynamics regulating large climatic transitions such as glacial-interglacial cycles or DO
events remains a puzzle. Forcings behind these transitions are not robustly identified and
potential candidates (e.g. Milankovitch cycles, freshwater perturbations) often appear too
weak to explain such dramatic transitions. A potential solution to this long-standing puzzle is
that Earth’s climate is endowed with multiple equilibrium states of global extent. Such states
are commonly found in low-order or conceptual climate models, but it is unclear
whether a system as complex as Earth’s climate can sustain multiple equilibrium
states.
Here we report that multiple equilibrium states of the climate system are also possible in a
complex, fully dynamical coupled ocean-atmosphere-sea ice GCM with idealized Earth-like
geometry, resolved weather systems and a hydrological cycle. In our model, two equilibrium
states coexist for the same parameters and external forcings: a Warm climate with a small
Northern hemisphere sea ice cap and a large southern one and a Cold climate with large ice
caps at both poles. The dynamical states of the Warm and Cold solutions exhibit striking
similarities with our present-day climate and the climate of the Last Glacial Maximum,
respectively. A carbon cycle model driven by the two dynamical states produces an
atmospheric pCO2 draw-down of about 110 pm between the Warm and Cold states, close
to Glacial-Interglacial differences found in ice cores. Mechanism controlling the
existence of the multiple states and changes in the atmospheric CO2 will be briefly
presented.
Finally we willdescribe transition experiments from the Cold to the Warm state, focusing
on the lead-lags in the system, notably between the Northern and Southern Hemispheres
climates. |
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