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Information - CL22 Decadal to millennial scale variability during the Pleistocene and Holocene (co-listed in SSP)
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Event Information |
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High-resolution studies are providing increasing evidence of significant climatic instability through the Pleistocene, including the Holocene. Variability seems to occur on all resolved time scales, and links with solar variability have been inferred. Also, internal non-linear feedback mechanisms and stochastic resonance have been discussed as key to some of the variability observed. Particularly tantalising are the 'medium-period' cycles, around 1500 and 2500 years, for which no conclusive mechanisms have yet been identified. Evidence is increasing that the 'cold' phases, with glacier advances, were synchronous not only on the northern hemisphere, but even on the southern hemisphere. Shorter variability (around 11 yrs, 80 yrs, and 200 yrs) may be more readily ascribed to such processes as short- and long-term sun-spot cycles, as there have been historical observations of such cycles and accounts of 'grand minima' in sunspot numbers such as the Maunder minimum. There is an almost unsurmountable problem, however, in reliably correlating such very short cycles from site to site (new ideas are very welcome in this session!). Key issues on which presentations are invited concern: (a) the regional to global expressions of decadal to millennial-scale variability, in all media from ice-sheets to the deep ocean; (b) the mechanisms/ processes/ amplifications that determine how small changes in solar energy output become recorded in climate proxies; (c) the spatial 'pattern' of short-term variability between the various major climate systems (e.g., polar circulation and monsoons); (d) high-resolution dating/chronologies which can be used as one of the tools for correlation between sites/records; and of course (e) any possible alternative explanations.
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