Linking Glacial-Interglacial cycles to multiple equilibria of climate
David Ferreira
(Université de Reading, Grande Bretagne)
| Quand ? |
Le 21/06/2016, de 15:00 à 16:00 |
|---|---|
| Où ? | Centre Blaise Pascal |
| Participants |
David Ferreira |
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The existence of multiple equilibrium states in Earth’s climate would profoundly impact our interpretation of the paleoclimate record and our perspective on future climate change.
Multiple equilibria are often found in non-linear low-order models of climate. Here I show that multiple stable climate states (of global extent) can be observed in a complex fully dynamical ocean-atmosphere-sea ice General Circulation Model. The model uses idealized configurations including an Earth-like configuration.
Two or three equilibrium states can coexist: a “Warm” climate with a southern hemisphere ice cap, a “Cold” climate with large ice caps at both poles, and a fully glaciated (Snowball) state. Dynamically, the multiple sea ice states owe their existence to a fundamental and robust feature of the ocean circulation: a large divergence/convergence of the ocean heat transport at the Equator/mid-latitudes.
The Warm and Cold climates exhibit striking similarities with our present-day climate and the climate of the Last Glacial Maximum, respectively, suggesting that their physics could be part of the Glacial oscillations of the last 3 million years. Implications for our understanding of the Glacial-Interglacial cycles, and their relationship to Milankovitch's orbital cycles (e.g. stochastic resonance) will be discussed.