Monterey Bay Aquarium Research Institute

Cycles in climate records

W. H. Berger, Ph.D.
 California Space Institute,
 University of California, San Diego

Wednesday, August 18, 2004
Pacific Forum 3:00 p.m.

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Records from ice cores, tree-rings, and marine sediments contain cycles, with energy concentrated in certain seemingly narrow frequency bands. For some such cycles, in the Milankovitch band, the forcing is reasonably well understood, although room for discussion remains. For other cycles, in the range between 10 to 100 years, and the cycle close to 1500 years, possible forcings are a matter of speculation, including the influence of a variable sun, and of lunisolar tides. A comparison of different types of records will show which of the periods are of a general nature, and which are bound to local conditions of the recording device. Surprises are bound to emerge when combining internal oscillations with mild outside forcing. The presence of tidal information in coral records and varved sediments should not be surprising, however. They do depend on processes in shallow waters affected by tides.