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Taking the Sun’s Pulse
There’s a new GRL ‘paper in press’ entitled: ‘Taking the pulse of the Sun during the Holocene by joint analysis of 14C and 10Be’ by Knudsen, M. F., P. Riisager, B. H. Jacobsen, R. Muscheler, I. Snowball, and M.-S. Seidenkrantz (2009), Geophys. Res. Lett., doi:10.1029/2009GL039439
The Abstract states:
We have studied solar variations during the Holocene (i.e. last ~11,700 yr) by combining a new model of the Earth’s dipole moment with 14C data from the IntCal04 record and 10Be data from the GRIP ice core. Joint spectral analysis of the two nuclide records suggests that the 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 the Sun. Subtle but systematic differences between the amplitude spectra may point to an interplay between the climate system and the ~220- and ~400-year solar cycles during intervals when these were particularly prominent.
In the results and Discussion the authors state:
The dominant periodicities observed in this study are ~88, ~150, ~220, ~400 years, which generally agrees with previous studies of 14C records [Stuiver and Braziunas, 1989; 1993; Damon and Sonnett, 1991]. The combined power spectrum also suggests that periodicities longer than ~1000 years exist, in particular around 3000 and 7500 yr BP (Fig. 2c), but, because the FFT (solar magnetic field: spectral analysis) approach used here is designed to localize the solar cycles in time, we cannot also discriminate reliably between solar cycles of ~1500 and ~2200 years (somewhat analogous to Heisenberg’s uncertainty principle). The most likely cause for the periodicities <500 years is the varying Sun because geomagnetic field intensity variations would have been unrealistically large to cause similar high-frequency, large-amplitude changes in radionuclide production [Snowball and Muscheler, 2007]. Most interestingly, both reconstructions indicate that the amplitudes of the solar periodicities varied significantly in time. The solar cycles were particularly prominent during the time intervals 6000-4500 yr BP and 3000-2000 yr BP, whereas this periodic behavior faded during other time intervals. The Gleissberg cycle, however, which was most prominent between 4000 and 6000 yr BP, was surprisingly vague from ~3500 yr BP onwards. Hence, although it remains complicated to reconstruct the long-term Holocene solar variability (Fig. 1), our analysis of spectral power through time robustly demonstrates that the behavior of the Sun did vary on these timescales.
and:
Nevertheless, in the light of the paleoevidence for a solar influence on climate, it seems possible that the ~220- and ~400-year solar cycles influenced the climate system in particular between 6000 and 4500 yr BP and between 3000 and 2000 yr BP, but it remains difficult to resolve whether it was the 14C signal, the 10Be signal, or both, that reflect the climate response. Interestingly, both these intervals coincide with periods of significant reorganization of the ocean and atmosphere circulation in the North Atlantic region [Kaplan and Wollfe, 2006; Seidenkrantz et al., 2007].