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Documents  76E20 | enregistrements trouvés : 3

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For a wide range of values of the incoming solar radiation, the Earth features at least two attracting states, which correspond to competing climates. The warm climate is analogous to the present one, the snowball climate features global glaciation and conditions that can hardly support life forms. Paleoclimatic evidences suggest that in past our planet flipped between these two states. The main physical mechanism responsible for such instability is the ice-albedo feedback. In a previous work, we defined the Melancholia states that sit between the two climates. Such states are embedded in the boundaries between the two basins of attraction and feature extensive glaciation down to relatively low latitudes. Here, we explore the global stability properties of the system by introducing random perturbations as modulations to the intensity of the incoming solar radiation. We observe noise-induced transitions between the competing basins of attractions. In the weak noise limit, large deviation laws define the invariant measure and the statistics of escape times. By empirically constructing the instantons, we show that the Melancholia states are the gateways for the noise-induced transitions. In the region of multistability, in the zero-noise limit, the measure is supported only on one of the competing attractors. For low (high) values of the solar irradiance, the limit measure is the snowball (warm) climate. The changeover between the two regimes corresponds to a first order phase transition in the system. The framework we propose seems of general relevance for the study of complex multistable systems. At this regard, we relate our results to the debate around the prominence of contigency vs. convergence in biological evolution. Finally, we propose a new method for constructing Melancholia states from direct numerical simulations, thus bypassing the need to use the edge-tracking algorithm. For a wide range of values of the incoming solar radiation, the Earth features at least two attracting states, which correspond to competing climates. The warm climate is analogous to the present one, the snowball climate features global glaciation and conditions that can hardly support life forms. Paleoclimatic evidences suggest that in past our planet flipped between these two states. The main physical mechanism responsible for such i...

82C26 ; 60Gxx ; 37D45 ; 85A20 ; 76E20

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- 182 p.
ISBN 978-2-8031-0146-7

Publication de la classe des sciences Série 3 , 0002

Localisation : Ouvrage RdC (PIRO)

aspect numérique dans le cas unidimensionnel # barrage de la Vesdre à Eupen # bassin du blanc gravier # cas quasi- tridimensionnel # généralisation aux terrains naturels # modélisation d'écoulement transitoire en cours d'eau # modélisation de crue # modélisation du ruissellement hydrologique # propagation sur fond sec ou humide # ressaut # écoulement consécutif à une rupture de barrage

73M25 ; 76-05 ; 76E20 ; 86A05

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ISBN 978-0-8218-9133-9

Memoirs of the american mathematical society , 1073

Localisation : Collection 1er étage

stabilité des couches limites d'Ekman # spirale d'Ekman # stabilité asymptotique # solutions faibles # solutions fortes # inégalité forte d'énergie # égalité forte d'énergie # unicité de solutions faibles # douceur et régularité # vraie théorie d'interpolation # calcul des perturbations # force de Coriolis # effet de stratification # système de Boussinesq

76E20 ; 35B35 ; 35B40 ; 35B65 ; 76D03 ; 76D05

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