HR: 09:00h
AN: PP41A-05    [PDF]
TI: Glacial-Interglacial Contrast in Climate Variability at Centennial-to-Millennial Timescales: Observations and Conceptual Model
AU: * Schulz, M
EM: mschulz@palmod.uni-bremen.de
AF: Dept. of Geosciences and DFG Research Center Ocean Margins, University of Bremen, PO Box 330440, Bremen, 28334 Germany
AU: Paul, A
EM: apau@palmod.uni-bremen.de
AF: Dept. of Geosciences and DFG Research Center Ocean Margins, University of Bremen, PO Box 330440, Bremen, 28334 Germany
AB: A set of published paleoclimatic proxy records from the northern hemisphere is used to assess glacial-interglacial differences in climate variability at centennial-to-millennial time scales during the past fifty thousand years. The employed proxy data represent a range of climate subsystems (taken as the smallest units capable of coherent climate variations). Glacial climate variability is dominated by the Dansgaard-Oeschger cycles and appears highly coherent between the involved climate subsystems, implying frequency locking to a {\it fundamental} 1470-year pacing signal. In contrast, there is no compelling evidence for a dominant and persistent centennial-to-millennial climate cycle during the Holocene. Interglacial climate variations seem to be less coherent than those of the last glacial period, suggesting that the climate subsystems were able to vary at their natural periods. A conceptual model is introduced to interpret this contrast in coherency at glacial-interglacial timescales. In the model, climate subsystems are represented by relaxation oscillators with different frequencies in the centennial-to-millennial band. Allowing for interaction between the free running oscillators can lead to a synchronization of the oscillators and the development of a frequency of the synchronized oscillators that differs from any frequency of the free oscillations. We suggest that the coupled/synchronized system resembles the glacial mode of climate variability whereas the decoupled state is reminiscent of an interglacial with its non-coherent climate variations over a wide frequency range.
DE: 1620 Climate dynamics (3309)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting