DOI: 10.1007/s00382-015-2501-9
Scopus记录号: 2-s2.0-84946478388
论文题名: The middle Pleistocene transition as a generic bifurcation on a slow manifold
作者: Ashwin P. ; Ditlevsen P.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2015
卷: 45, 期: 2017-09-10 起始页码: 2683
结束页码: 2695
语种: 英语
英文关键词: Bifurcation
; Ice age
; Middle Pleistocene transition
; Nonlinear oscillation
; Slow manifold
英文摘要: The Quaternary period has been characterised by a cyclical series of glaciations, which are attributed to the change in the insolation (incoming solar radiation) from changes in the Earth’s orbit around the Sun. The spectral power in the climate record is very different from that of the orbital forcing: prior to 1000 kyr before present most of the spectral power is in the 41 kyr band while since then the power has been in the 100 kyr band. The change defines the middle Pleistocene transition (MPT). The MPT does not indicate any noticeable difference in the orbital forcing. The climate response to the insolation is thus far from linear, and appears to be structurally different before and after the MPT. This paper presents a low order conceptual model for the oscillatory dynamics of the ice sheets in terms of a relaxation oscillator with multiple levels subject to the Milankovitch forcing. The model exhibits smooth transitions between three different climate states; an interglacial (i), a mild glacial (g) and a deep glacial (G) as proposed by Paillard (Nature 391:378–381, 1998). The model suggests a dynamical explanation in terms of the structure of a slow manifold for the observed allowed and “forbidden” transitions between the three climate states. With the model, the pacing of the climate oscillations by the astronomical forcing is through the mechanism of phase-resetting of relaxation oscillations in which the internal phase of the oscillation is affected by the forcing. In spite of its simplicity as a forced ODE, the model is able to reproduce not only general features but also many of the details of oscillations observed in the climate record. A particular novelty is that it includes a slow drift in the form of the slow manifold that reproduces the observed dynamical change at the MPT. We explain this change in terms of a transcritical bifurcation in the fast dynamics on varying the slow variable; this bifurcation can induce a sudden change in periodicity and amplitude of the cycle and we suggest that this is associated with a branch of “canard oscillations” that appear for a small range of parameters. The model is remarkably robust at simulating the climate record before, during and after the MPT. Even though the conceptual model does not point to specific mechanisms, the physical implication is that the major reorganisation of the climate response to the orbital forcing does not necessarily imply that there was a big change in the environmental conditions. © 2015, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/54139
Appears in Collections: 过去全球变化的重建
There are no files associated with this item.
作者单位: Centre for Systems, Dynamics and Control, Harrison Building, University of Exeter, Exeter, United Kingdom; Centre for Ice and Climate, Niels Bohr Institute, Juliane Maries Vej 30, Copenhagen, Denmark
Recommended Citation:
Ashwin P.,Ditlevsen P.. The middle Pleistocene transition as a generic bifurcation on a slow manifold[J]. Climate Dynamics,2015-01-01,45(2017-09-10)