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| Titel |
A simple conceptual model of abrupt glacial climate events |
| VerfasserIn |
H. Braun, A. Ganopolski, M. Christl, D. R. Chialvo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 14, no. 6 ; Nr. 14, no. 6 (2007-11-23), S.709-721 |
| Datensatznummer |
250012307
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| Publikation (Nr.) |
 copernicus.org/npg-14-709-2007.pdf |
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| Zusammenfassung |
| Here we use a very simple conceptual model in an attempt to reduce essential
parts of the complex nonlinearity of abrupt glacial climate changes (the
so-called Dansgaard-Oeschger events) to a few simple principles, namely (i)
the existence of two different climate states, (ii) a threshold process and
(iii) an overshooting in the stability of the system at the start and the end
of the events, which is followed by a millennial-scale relaxation.
By comparison with a so-called Earth
system model of intermediate complexity (CLIMBER-2), in which the events represent
oscillations between two climate states corresponding to two fundamentally
different modes of deep-water formation in the North Atlantic, we demonstrate
that the conceptual model captures fundamental aspects of the nonlinearity of
the events in that model. We use the conceptual model in order to reproduce
and reanalyse nonlinear resonance mechanisms that were already suggested in
order to explain the characteristic time scale of Dansgaard-Oeschger
events. In doing so we identify a new form of stochastic resonance (i.e. an
overshooting stochastic resonance) and provide the first explicitly
reported manifestation of ghost resonance in a geosystem, i.e. of a
mechanism which could be relevant for other systems with thresholds and with
multiple states of operation. Our work enables us to explicitly simulate
realistic probability measures of Dansgaard-Oeschger events (e.g. waiting
time distributions, which are a prerequisite for statistical analyses
on the regularity of the events by means of Monte-Carlo
simulations). We thus think that our study is an important advance in
order to develop more adequate methods to test the statistical
significance and the origin of the proposed glacial 1470-year climate cycle. |
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