Talk by Michel Crucifix – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2011 > Talk by Michel Crucifix

Talk by Michel Crucifix

Talk by Michel Crucifix, Georges Lemaitre Centre for Earth and Climate Research Université catholique de Louvain 


The climatic fluctuations that characterized the Pleistocene (last 3 Myr) may be reconstructed from numerous natural archives, including marine, continental and ice core records. These archives reveal complex climate history. Ice sheets appeared in the northern hemisphere around 3 million years ago. Glacial-interglacial cycles paced Earth's climate, first according to a 40-kyr long cycle, which lengthened markedly 800,000 years ago.

Superimposed to these long glacial cycles comes an intricate pattern of millennial and sub-millennial variability. For example, the Greenland record features at least 20 events of abrupt rise and slower decline in oxygen isotopic ratio (a proxy for temperature) and methane during the last glacial epoch. These events are known as Dansgaard-Oeschger events, well-known at the ice and climate Centre in Copenhague.

 This presentation reviews attempts to explain these fluctuations with concepts that originate in dynamical system theory. These are the concepts of limit cycle, synchronisation and excitability. The central message  is that current theories on ice ages and rapid events may often be interpreted in terms of generic models, which are also used in other areas of sciences like biology and ecology. The effects of stochastic fluctuations are also reviewed. The presentation is concluded with more personal considerations on the about the potential for inference with simple stochastic dynamical systems in palaeoclimate science.