Nonlinear Sciences
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmpp31c1645d&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #PP31C-1645
Nonlinear Sciences
[4901] Paleoceanography / Abrupt/Rapid Climate Change, [4910] Paleoceanography / Astronomical Forcing, [4934] Paleoceanography / Insolation Forcing, [4946] Paleoceanography / Milankovitch Theory
Scientific paper
Paleoclimatic records have shown evidence of glacial/interglacial asymmetric cycles over the last millions years of the Plio/Pleistocene. The fact that deglaciations occur much more rapidly than glaciations indicates that the underlying dynamics is very likely to be a slow-fast dynamics, like the one of relaxation oscillators; hence this model will be used here. Several hypotheses on the origin of these glacial cycles were made, among which a wide community of supporters of the Milankovitch theory, and further refinements by his successors; the idea being that the incoming solar radiation drives climate, hence the long-term variations of the former, induced by a varying Sun-Earth astronomical configuration, paces these ice ages. This so-called astronomical forcing is related to the universal concept of synchronization in nonlinear sciences. We go a step further by investigating the robustness of such a synchronization. For doing this, we combine local and global views of the dynamics, given by 2 indicators: the local largest Lyapunov exponent, and the evolving geometry of the basins of attraction due to the aperiodic insolation. We find that even if the attracting trajectories are Lyapunov-stable on a long term, there exist positive values of the local Lyapunov exponent, so that climatic orbits could diverge for some period of time (50 kyr typically), due to a small perturbation. Moreover, as the attracting trajectories can sometimes lie quite close to the boundary of their basins of attraction, a small perturbation could cause a phase slip, reducing predictability. We show an example where the noise makes the Climate jump from one to another climatic trajectory. We also compare the real complex insolation forcing to the case of a smooth periodic forcing, and study the effect of the insolation amplitude through bifurcation diagrams. The climate could jump between these 3 attracting trajectories.
Crucifix Michel
de Saedeleer Bernard
Wieczorek Sebastian M.
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