Global ice sheets during the last two climatic cycles, with an emphasis on entering into glaciation

Informations projet

N° de convention de subvention: INTAS-93-0979

Projet clôturé

Date de début 1 Avril 1995

Date de fin 31 Mars 1996

Financé au titre de

• International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993-

Coût total

Aucune donnée

Contribution de l’UE

€ 30 000,00

Coordonné par

Université Catholique de Louvain
Belgium

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Résultats exploitables

Global ice sheets during the last two climatic cycles, with an emphasis on entering into glaciation

The project was aimed at the investigation of the last two glacial cycles. The specific goals of Russian participants during the project were collecting of data on Eurasian glaciation and analysis of stochastic features of the glaciation-deglaciation process. Analysis of palaeo-reconstructed proxies and experiments ondynamic-stochastic models of glacial cycles demonstrate a very important role of stochastic processes. It is shown that changes in glacial volume and global meansea level during the last several hundred Kyrs are adequately described by the threshold Wiener or first order Markov process model with changing variances of random component. Experiments without external astronomic periodic forcing on dynamic-stochasticmodels, which take into account only few fundamental, well-established features of processes of the above type (i.e. without deterministic feedback's or deterministic non-linear processes within the system) show that they can generate one or two isolated glaciation cycles of magnitudes comparable to the observed ones.Imposition of even weak astronomic periodic forcing with 100 Kyrs period creates stable periodic oscillations in mean values and standards (variances) of global glacial volume. It is hypothesises that changing, with volume of glaciation, variability(standards of variances) of random component is the key factor of both generating isolated glacial cycles without external forcing and of amplifying astronomic periodic forcing. In the last case stochastic mechanism can amplify the periodical oscillations of mean ice volume by the order of magnitude, and that standard oscillations by two orders of magnitude. Some important, more detailed features of glacial dynamics are described by dynamic-stochastic models as well. For instance, models reproduce the asymmetric form and phase lags of changes in standards of glacial volumes. In accordance with the data of palaeo-reconstruction's, model variability of ice volume is higher at the stage of deglaciation than at the stage of entering into glaciation.Models do not amplify external 100 Kyrs periodic forcing but also internally reproduce peaks of glacial changes at periods close to 41 Kyrs and 23 Kyrs.General pattern of the possible future natural evolution of the climate-glacial system was established on the basis of the above results.