We have studied solar variations during the Holocene (i.e., last ~ 11,700 yr) by combining a new model of the Earth's dipóle moment with 14C data from die IntCal04 record and 10Be data from the GRIP ice core. Joint spectral analysis of the two nuclide records suggests that die periodic behavior of the Sun was particularly pronounced between 6000-4500 yr BP and 3000-2000 yr BP, with dominating periodicities of ~88, ~150, ~220, and ~400 years, while this rhythmic behavior faded during other time intervals. The fact that the two reconstructions, based on radionuclides with distinct geochemical properties, agree with respect to both the frequency and timing of the periodic behavior, strongly suggests that they reflect the actual behavior of die Sun. Subtle but systematic differences between die amplitude spectra may point to an interplay between the climate system and the ~220- and ~400-year solar cycles during intervals when diese were particularly prominent.
- Programområde 5: Natur og klima