In order to understand the origin of the Suess wiggles, present in the tree ring 14C record, we have studied the thermoluminescence (TL) of a shallow-water Ionian sea core, in an attempt to provide a record of an indicator

responding to the solar output more promptly than 14C in tree rings. The spectral content of the TL and radiocarbon records is very similar; neverthless, in addition to the 207 y Suess wave (A43.6% ), the TL record shows the second harmonic (103.5 y; A42.4% ), in phase with the envelope of the 11 y solar cycles. This result, obtained by different spectral methods, in particular by Superposition of Epochs (SE) and by Singular Spectrum Analysis (SSA), strongly supports the solar origin of the 200 y Suess wiggles

Bonino, G.

Cini Castagnoli, G.

Della Monica, P.

Procopio, S.

Taricco, C.

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IL NUOVO CIMENTO Marzo-Aprile 1998VOL. 21 C, N. 2On the solar origin of the 200 y Suess wiggles:Evidence from thermoluminescence in sea sedimentsG. CINI CASTAGNOLI, G. BONINO, P. DELLA MONICA, S. PROCOPIO and C. TARICCODipartimento di Fisica Generale, Università di Torinoand Istituto di Cosmogeofisica del CNR - C.so Fiume 4, I-10133 Torino, Italy(ricevuto il 10 Dicembre 1997; approvato il 22 Dicembre 1997)Summary. — In order to understand the origin of the Suess wiggles, present inthe tree ring 14C record, we have studied the thermoluminescence (TL) of ashallow-water Ionian sea core, in an attempt to provide a record of an indicatorresponding to the solar output more promptly than 14C in tree rings. The spectralcontent of the TL and radiocarbon records is very similar; neverthless, in addition tothe 207 y Suess wave (A43.6% ), the TL record shows the second harmonic (103.5 y;A42.4% ), in phase with the envelope of the 11 y solar cycles. This result, obtained bydifferent spectral methods, in particular by Superposition of Epochs (SE) and bySingular Spectrum Analysis (SSA), strongly supports the solar origin of the 200 ySuess wiggles.PACS 91.50 – Marine geology and geophysics.PACS 96.40 – Cosmic rays.1. – IntroductionThe solar origin of the 207 y periodicity present in the 14C tree ring record, resultingfrom repeated Maunder-like maxima, was proposed by Suess, but up to now it remainsconjectural; in fact, a) it is not possible to find a mechanism to force the Sun at suchlong periods and b) there is no direct evidence for a A 200 y signal from the Sun asmonitored by sunspots (the record is too short) nor from historical aurorae. Moreover,the solar imprint in the radiocarbon record is very faint [1] because the transportmechanism of 14C (as CO2 ) from the atmosphere into the trees acts like a filter for thehigh frequencies, which could be compared to the observed solar-activity variations.We consider here the thermoluminescence (TL) profile of a shallow-water coretaken from the Ionian Sea (Gallipoli Terrace) in an attempt to provide a record of anindicator responding promptly to the solar output, i.e. able to identify centennial andalso decadal periodicities, as those which appear in the solar-activity record of thesunspots. We have proposed this possibility in previous papers, using the TL profilemeasured in two cores (GT14 and GT89-3), at sampling intervals of 2.5 mm and 2 mm,respectively, covering the last 1800 years: the great accuracy reached in the core datingG Società Italiana di Fisica 237G. CINI CASTAGNOLI, G. BONINO, P. DELLA MONICA, ETC.238up to two millennia BP allowed us to detect in the TL record an 11 y cycle using bothclassical methods of time series analysis and Singular Spectrum Analysis (MC-SSAsignificance level of 95%) [2]. The success in detecting the Schwabe solar cycle in thistype of archive gives us the confidence that this indicator may be used to reveal longerperiodicities also forced by the solar output.2. – Analysis of the TL profileWe present here the TL profile of the GT89-3 core (180 m water depth; 397 458 439N,177 538559E) sampled at consecutive intervals of 2 mm, corresponding to a time step of3.096 y; in fact we have measured a sedimentation rate s4 (0.06456 0.0007) cm y21 ,constant on the average along the core [3, 4]. For this analysis we consider 167 cm (834samples) of the core covering the last A 2600 y (from 2605 AD). The experimentalprocedure to measure the TL signal is the “disk technique” described in [5], where wehave discussed the TL measurements of the uppermost part of the core.The TL time profile, centered (mean value 83 a.u.) and detrended by SSA [6] (fromPCs 1-2, M4180), is shown in fig. 1 (red curve). The decadal data of D 14C (‰) in treerings, after removal of the long-term trend [7], starting at the same date of the TLrecord, is also shown in fig. 1 (blue curve).To search for periodicities in the two time series, we use the method ofSuperposition of Epochs (SE). In this approach, the time series are partitioned intoconsecutive segments of fixed length T which are then superposed and averaged on nsub-intervals. By least-square–fitting a sinusoid with period T to the superposedexperimental data, we have determined amplitude and phase (with respect to 247 AD)-500 0 500 1000 1500 2000year (A.D.)-80-60-40-2002040TL GT89-3 (a.u.)-500 0 500 1000 1500 2000-10010203040delta C-14Fig. 1. – The red curve shows the TL time series of the GT89-3 core, detrended by SSA (PCs 1-2)and the blue curve the D 14C decadal tree ring record [7]. Superposed to the data are shown the207 y waves, estimated by the method of SE.ON THE SOLAR ORIGIN OF THE 200 y SUESS WIGGLES: ETC. 2390 50 100 150 200 250 300period (yr)0.00.51.01.52.02.53.03.54.0amplitude0 50 100 150 200 250 3000.00.51.01.52.02.53.03.54.0TL14 C80103207Fig. 2. – Amplitude of the least-square–fit sinusoids to the superposed data as obtained by themethod of SE (“stacking”) for the radiocarbon record (blue curve) and for the TL series (redcurve) as a function of period T .of the waves, for T varying up to 300 y, in steps of 1 y. In fig. 2 we show the amplitude ofthe best-fit sinusoid as a function of T for TL (in red) and for D 14C (in blue). The closesimilarity in the behaviour of the two records is evident. In particular, we note thatthe strongest amplitude in the radiocarbon record is around T4207 y (AA3‰ ,f41.13 rad). This result is in agreement with the presence of the well-known Suesswiggles. The 207 y periodicity is present also in the TL record with an amplitude of3.6% (AA3 a.u., f42.82 rad). We note that the phase difference between the radio-carbon and the TL 207 y waves is p/2 with TL leading radiocarbon.In addition, in the same fig. 2 we note that the TL record shows the secondharmonic T4103 y with an amplitude of 2.4% (A42 a.u., f44.27 rad). It appears inthe region were the D 14C power is damped by the effect of the CO2 reservoir. We notealso the presence of the Gleissberg solar cycle at A 80 y.The presence of the 103 y periodicity in the TL record is very important, because itrepresents a possible way to link the Suess wiggles to the solar-sunspot record.Therefore, we were induced to confirm its presence using different spectral methods;here in particular we show the result obtained by SSA. Adopting a window width t M4Mt s`295 y, where M495 and t s43.096 y is the sampling interval, we found that PCs8-9 carry the centennial periodicity. The robustness of this result was confirmed usinga large interval of M-values (80EME180). The reconstructed time series from PCs8-9 (green curve) is shown in fig. 3, together with the wave obtained by the SE method(red curve); we notice the agreement between the results obtained by the two differentmethods. In order to test the connection of the 103 y signal and the solar activity, weshow in the same figure the sunspot number series (yellow curve). We note the overallG. CINI CASTAGNOLI, G. BONINO, P. DELLA MONICA, ETC.2401700 1750 1800 1850 1900 1950 2000years050100150200sunspot number1700 1750 1800 1850 1900 1950 2000-4-20246TL intensity (a.u.)207 y103.5 yFig. 3. – 103.5 y and 207 y sinusoidal TL waves (red curves by SE and green curve by SSA) withthe sunspot number series (yellow area).similarity of the two TL signals to the amplitude modulation of the 11 y solar cycle. Inthe same figure, the TL wave with period 207 y is also shown (red dash-dotted curve).We notice that the 207 y and 103 y waves are in phase, suggesting that the TL indexrecords the A 100 y modulation envelope of the 11 y solar cycles with higher and loweramplitude alternatively.3. – Discussion and conclusionWhen crystalline minerals are exposed to ionizing radiation in their naturalenvironment, free electrons and holes are produced. A small fraction of the formerbecomes trapped at defects in the crystals and these trapped charges are released andare able to recombine giving rise to the TL signal in a radiative process during theheating of the samples. The recombination comes also as a consequence of the exposureof the material to light. There is an equilibrium level of TL in the crystals at the time ofsettling which is preserved after deposition. The balance between formation andrecombination will vary in time. Under the hypothesis that the material does notchange, we may be able to trace the level of illumination-irradiation of the mud for thelast millennia.The competition of the two mechanisms determines the TL level stored in thesamples. In particular, the sum of the 207 y and 103.5 y waves, which are in phase,suggests that the TL index records the envelope of the Schwabe cycles, with higherand lower amplitude alternatively.ON THE SOLAR ORIGIN OF THE 200 y SUESS WIGGLES: ETC. 241The 11 y and the 103.5 y periodicities found in the TL record suggest a strongconnection between the TL signal and the solar output. Moreover, the presence inthe TL time series of the A 207 y cycle and of its second harmonic (enveloping thesunspot number record) gives a convincing argument in favour of the solar origin of theA 200 y ubiquitous signal observed in terrestrial archives, in particular in the tree ringradiocarbon.* * *We are grateful to Prof. C. CASTAGNOLI for helpful discussions and support and toMr. A. ROMERO for careful technical assistance.R E F E R E N C E S[1] STUIVER M. and BRAZIUNAS T. F., The Holocene, 3 (1993) 289.[2] CINI CASTAGNOLI G., BONINO G., DELLA MONICA P. and TARICCO C., in Past and PresentVariability of the Solar-Terrestrial System: Measurements, Data Analysis and TheoreticalModels, Procedings of the International School of Physics Enrico Fermi, Course CXXXIII,edited by G. CINI CASTAGNOLI (IOS Press, Amsterdam) 1997, p. 59.[3] CINI CASTAGNOLI G., BONINO G., CAPRIOGLIO F., PROVENZALE A., SERIO M. and ZHU G. M.,Geophys. Res. Lett., 17 (1990) 1937.[4] BONINO G., CINI CASTAGNOLI G., CALLEGARI E. and ZHU G.M., Nuovo Cimento C, 16 (1993)155.[5] CINI CASTAGNOLI G., BONINO G., DELLA MONICA P. and TARICCO C., Nuovo Cimento C, 20(1997) 1.[6] DETTINGER M. D., GHIL M., STRONG C. M., WEIBEL W. and YIOU P., EOS, Trans. AGU, 76(1995) 12.[7] STUIVER M. and BRAZIUNAS T. F., in Secular, Solar and Geomagnetic Variations in the Last10,000 Years, edited by F. R. STEPHENSON and A. W. WOLFENDALE (Kluwer, Dordrecht) 1988,p. 245.

On the solar origin of the 200 y Suess wiggles: Evidence from thermoluminescence in sea sediments

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On the solar origin of the 200 y Suess wiggles: Evidence from thermoluminescence in sea sediments

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