Ghil is a founder of theoretical climate dynamics, as well as of advanced data assimilation methodology. He has applied systematically dynamical systems theory to planetary-scale flows, atmospheric and oceanic. Ghil has used these methods to proceed from simple flows with high temporal regularity and spatial symmetry to the observed flows, with their complex behavior in space and time. His studies of climate variability on many time scales have used a full hierarchy of models, from the simplest ‘toy’ models all the way to atmospheric, oceanic and coupled general circulation models. Recently, Ghil has also worked on modeling and data analysis in population dynamics, macroeconomics, and the climate–economy–biosphere system.
The oceans are an inseparable part of the Earth’s climate system but are often considered as a separate subsystem that is subject to mass, momentum and energy fluxes from the atmosphere. The proper mathematical setting for this point of view is that of nonautonomous and random dynamical systems (NDS and RDS) as opposed to the more classical framework of autonomous ones, usually just referred to as differentiable dynamical systems (DDS).
An essential aspect of the difference is replacing the classical fixed points, limit cycles and strange attractors by pullback or random attractors (PBAs or RAs). We will show how to carry out these generalizations with respect to the oceans’ wind-driven circulation in mid- and high latitudes. The work that will be presented was carried out jointly with M.D. Chekroun, J.D. Neelin, S. Pierini, E. Simonnet, S. Vannitsem and I. Zaliapin.
Arranged date for the seminar talk: Jun 12, 2019