Huybers, Peter and Aharonson, Oded (2010) Orbital tuning, eccentricity, and the frequency modulation of climatic precession. Paleoceanography, 25 . Art. no. PA4228. ISSN 0883-8305 http://resolver.caltech.edu/CaltechAUTHORS:20110131-102315353
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The accuracy of geologic chronologies can, in principle, be improved through orbital tuning, the systematic adjustment of a chronology to bring the associated record into greater alignment with an orbitally derived signal. It would be useful to have a general test for the success of orbital tuning, and one proposal has been that eccentricity ought to covary with the amplitude envelope associated with precession variability recorded in tuned geologic records. A common procedure is to filter a tuned geologic record so as to pass precession period variability and compare the amplitude modulation of the resulting signal against eccentricity. There is a reasonable expectation for such a relationship to be found in paleoclimate records because the amplitude of precession forcing depends upon eccentricity. However, there also exists a relationship between eccentricity and the frequency of precession such that orbital tuning generates eccentricity-like amplitude modulation in filtered signals, regardless of the accuracy of the chronology or the actual presence of precession. This relationship results from the celestial mechanics governing eccentricity and precession and from the interaction between frequency modulation and amplitude modulation caused by filtering. When the eccentricity of Earth's orbit is small, the frequency of climatic precession undergoes large variations and less precession energy is passed through a narrow-band filter. Furthermore, eccentricity-like amplitude modulation is routinely obtained from pure noise records that are orbitally tuned to precession and then filtered. We conclude that the presence of eccentricity-like amplitude modulation in precession-filtered records does not support the accuracy of orbitally tuned time scales.
|Additional Information:||© 2010 American Geophysical Union. Received 23 February 2010; accepted 23 September 2010; published 23 December 2010. R. Sari (Hebrew University of Jerusalem) provided helpful discussion regarding orbital mechanics; C. Wunsch (MIT) and B. Bills (JPL) gave useful feedback on earlier drafts of this paper; and insightful reviews were provided by L. Lourens (Utrecht University), M. Crucifix (Université catholique de Louvain), and an anonymous reviewer.|
|Subject Keywords:||orbital tuning; precession; eccentricity|
|Official Citation:||Huybers, P., and O. Aharonson (2010), Orbital tuning, eccentricity, and the frequency modulation of climatic precession, Paleoceanography, 25, PA4228, doi:10.1029/2010PA001952|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||11 Feb 2011 19:11|
|Last Modified:||26 Dec 2012 12:53|
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