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. 2012 Apr 17;109(16):5967-71.
doi: 10.1073/pnas.1118965109. Epub 2012 Apr 2.

9,400 years of cosmic radiation and solar activity from ice cores and tree rings

Friedhelm Steinhilber  1 , Jose A Abreu, Jürg Beer, Irene Brunner, Marcus Christl, Hubertus Fischer, Ulla Heikkilä, Peter W Kubik, Mathias Mann, Ken G McCracken, Heinrich Miller, Hiroko Miyahara, Hans Oerter, Frank Wilhelms
Affiliations

9,400 years of cosmic radiation and solar activity from ice cores and tree rings

Friedhelm Steinhilber et al. Proc Natl Acad Sci U S A. .

Abstract

Understanding the temporal variation of cosmic radiation and solar activity during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such as (10)Be and (14)C which are stored in polar ice cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar activity over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different (10)Be ice core records from Greenland and Antarctica with the global (14)C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution (10)Be record from Dronning Maud Land obtained within the European Project for Ice Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Cartoon illustrating some basics of the radionuclides 14C and 10Be in the Earth’s system. Both radionuclides are produced in a very similar way by nuclear reactions of cosmic ray particles with the atmospheric gases (3). After production, their fate is very different (system effects). 10Be attaches to aerosols and is transported within a few years to ground (34). 14C oxidizes to CO2 and enters the global carbon cycle, exchanging between atmosphere, biosphere, and the oceans (4).
Fig. 2.
Fig. 2.
Radionuclide records used for this study. 10Be concentration records are green (Greenland) and red (Antarctica) and 14C is black. Time is given as year before present (BP where present refers to 1950 AD). All records are mean normalized (divided by the mean) 22-year averages. (A) New 10Be record from the EDML ice core (red) and of the existing 10Be record from the GRIP (GR) ice core (green). The data are plotted on the time scales EDML1 (35) for EDML and GICC05 (36, 37) for GRIP. (B) Δ14C, the deviation of the atmospheric 14C/12C ratio from a standard value, measured in tree rings (14) and (C) 14C production rate p14C (PC), calculated with a box-diffusion carbon cycle model (4) from Δ14C (14) over the last 9,400 y. (D) 14C production rate p14C (PC) and 10Be concentrations for several available ice cores (GR: GRIP; D3: Dye-3; NG: NorthGRIP; MI: Milcent; SP: South Pole; DF: Dome Fuji) over the last 1,200 y. Grand solar minima are marked by yellow bands and capital letters: O: Oort, W: Wolf, S: Spörer, M: Maunder, D: Dalton, G: Gleissberg.
Fig. 3.
Fig. 3.
(A) Geomagnetic dipole field strength relative to today (21). (B) Cosmic radiation based on the first principal component of several radionuclide records, 22-year averages, over the last 8,000 y. Time is given as year BP. The gray band represents the standard deviation of the individual radionuclide records without applying PCA (SI Appendix, Section S8). The black dashed line represents the average cosmic ray intensity for 1944–1988 AD. (C) Same as (B), but zoom-in of the past millennium. Capital letters mark grand solar minima: O: Oort, W: Wolf, S: Spörer, M: Maunder, D: Dalton, G: Gleissberg. (D) Same as (C), but zoom-in of the past 350 y. Time is given as year AD. Red circles and green curve are 22-year averages and yearly averages of cosmic ray intensity calculated with (3) using the solar modulation potential (38) obtained from neutron monitor and ionization chamber data (SI Appendix, Section S9). At the bottom the annual sunspot number is plotted (39).
Fig. 4.
Fig. 4.
Comparison of solar activity (total solar irradiance [TSI]) in blue and δ18O from Dongge cave, China, in green representing changes of the Asian climate. possibly the Asian monsoon (AM) (low δ18O corresponds to strong AM monsoon and vice versa). TSI has been reconstructed from the cosmic ray intensity reconstruction (SI Appendix, Section S10). Both records have been normalized (subtraction of mean value and division by the standard deviation), linearly detrended and high-pass filtered with 2,000 y. (A) Time series of solar activity (TSI) and δ18O. Solar activity (TSI) is plotted on a reversed scale. (B) Wavelet of solar activity (TSI). De Vries cycle at approximately 210 y and Eddy cycle at approximately 1,000 y are marked with horizontal, gray dashed lines. Black boundaries mark 95% significance level. (C) Wavelet coherence of solar activity (TSI) and δ18O. De Vries cycle at approximately 210 y and Eddy cycle at approximately 1,000 y are marked with horizontal, gray dashed lines. Arrows pointing to the right indicate that the records are in phase. Black boundaries mark the 95% significance level.
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References

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