Interactive comment on “ Does Belgian Holocene speleothem records solar forcing and cold events ? ” by Mohammed

Abstract. We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65 cm stalagmite ( Pere Noel ) from Belgian Pere Noel cave. Pere Noel (PN) stalagmite covers the last 12.7 ka according to U/Th dating. High spatial resolution measurements of trace elements (Sr, Ba, Mg and Al) were done by Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Trace elements profiles were interpreted as environmental and climate changes in the Han-sur-Lesse region. Power spectrum estimators and continuous wavelet transform were applied on trace elements time series to detect any statistically signiﬁcant periodicities in the PN stalagmite. Spectral analyses reveal decadal to millennial periodicities (i.e., 68–75, 133–136, 198–209, 291–358, 404–602, 912–1029 and 2365–2670 yr) in the speleothem record. Results were compared to reconstructed sunspot number data to determine whether solar signal is presents in PN speleothem. The occurrence of signiﬁcant solar periodicities (i.e., cycles of Gleissberg, de Vries, unnamed 500 years, Eddy and Hallstat) supports for an impact of solar forcing on PN speleothem trace elements contents. Moreover, several intervals of significant rapid climate change were detected during the Holocene at 10.3, 9.3–9.5, around 8.2, 6.4–6.2, 4.7–4.5, and around 2.7 ka BP. Those intervals are similar to the cold events evidenced in different natural paleoclimate archivers, suggesting common climate forcing mechanisms related to changes in solar irradiance.


Introduction
The Holocene period appears as a relatively stable climatic period compared to Quaternary glacial/interglacial variations.However several high-resolution studies have emphasized many climatic oscillations over the last 11500 yr 30 (e.g.Mayewski et al., 2004;Wanner et al., 2008Wanner et al., , 2011)).The Holocene climate variability was tentatively attributed to orbital forcing, volcanic, and/or solar activity (Wanner et al., 2008).Many climatic proxies (e.g.,  18 O,  13 C,  14 C, 10 Be, REE content, pollen, dust, humification, element traces) have been measured in different geological Moreover, the sunspot reconstruction of Solanki et al., (2004) was compared with the PN times series to identify eventual solar cycles in the PN proxies and as such determine the possibilities for the study of solar activity changes over the Holocene.

The state of the art of trace elements in speleothems
To understand the significance of the elemental variations in speleothems (i.e., Ba, Sr, Al and Mg), it is necessary to investigate the potential sources of the chemical elements and their transfer through the karst system.Then, the relations between stable isotopes and trace elements are characterized and may be related to paleoclimate changes.
They may also derive from the host rocks and adjacent soil cover (Tooth and Fairchild, 2003;Hartland et al., 2012;Treble et al., 2016).The trace elements could be transported along the soil profile by colloids or in dissolved forms depending on the element.The trace elements might show different forms of mobility (in dissolved and particulate form) and speed of migration in soils, depending on soil characteristics and processes (e.g., pH, organic acid content, 85 redox conditions, leaching, ion exchange, temperature).Finally, the karst hydrology may also play a role in the speleothem trace element content (Fairchild et al., 2000;Tooth and Fairchild, 2003).Karstic processes include organic matter decomposition, dissolution, desorption and adsorption of colloids, Prior Calcite Precipitation (PCP), incorporation into carbonate minerals (e.g., Fairchild and treble, 2009).
Previous studies have shown that the variations of trace element contents in a speleothem may provide information 90 about changes in soil condition, water temperature, paleorainfall and hydrological conditions (e.g., Roberts et al., 1999, Fairchild et al., 2000;Fairchild and Treble, 2009).In temperate regions, trace element such as Ba, Sr and Mg tend to increase during drier periods when residence times are longer (Huang et al., 2001;Verheyden et al., 2000).
Many studies performed on speleothems from different environmental settings reveal that both hydrological (e.g., amount of precipitation, groundwater residence time, rock-water interaction) and/or growth-related processes can 95 affect trace element concentrations (e.g., Verheyden et al., 2000;Treble et al., 2003;Tremaine and Froelich, 2013).
However, the link between trace element content in speleothems and climatic conditions can vary between caves settings due to differences in chemical composition of bedrock, groundwater movement, soil thickness and/or climatic conditions.Consequently, a thorough comparison between speleothem trace element content and another proxy (e.g., combining stable isotopes with trace elements and/or petrographic information and/or growth-rate) is important in 100 order to minimize the uncertainties associated with stable isotope data interpretation (Fairchild et al., 2006;McDermott, 2004;and Verheyden et al., 2001).

Material and methods
PN stalagmite, 65 cm long, was taken in 2000 from the Belgian Père Noël cave (50.0°N, 5.2°E, 230 masl) in the 105 Ardenne massif (Fig. 1).The cave located about 200 km inland in a temperate maritime climate.The cave opened in the Devonian (Givetian) Fromelenne Formation with subvertical limestone beds (Delvaux de Fenffe, 1985) that reach a thickness of 70 m above the cave (Deflandre, 1986).The water entering the cave consists of local rain only, seeping wichcorresponds to the mean annual temperature of the air (9.2°C) at the nearby Lessive.A detailed description of climate, geology, and hydrological conditions were published in Verheyden et al. (2000Verheyden et al. ( , 2008Verheyden et al. ( , 2012)).
The PN stalagmite was dated by TIMS U-series dating (10 dates) at the Department of Earth Sciences at Open University, UK.Other dates (6 dates) were done by NEPTUNE Multi-Collector Inductively Coupled Plasma Mass 115 Spectrometry (MC-ICP-MS) at the Laboratoire Géosciences Environnement Toulouse (GET) in France and one date was obtained in the Earth Science Department of the University of Minnesota on a Thermo-Scientific Neptune-Plus multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS).The procedures that were followed for uranium and thorium chemical separation and purification described in Edwards et al. (1987) and Cheng et al. (2009aCheng et al. ( , 2009b)).Dating results are summarized in Table 1, with ages given in years before 1950.Errors given in the table (2) 120 depend on the U and Th content and age of the sample.The elementary geochemical composition (Ba, Sr, Mg and Al) of PN stalagmite was determined by Laser Ablation Inductively Coupled Plasma-Mass Spectrometer (LA-ICP-MS) mounted with an ESI New Wave UP-193FX Fast Excimer ArF laser of 193 nm at the Royal Museum for Central Africa (Tervuren, Belgium).Spots were made of 50 µm in diameter and spaced at 300-1000 µm intervals.The age model reveals a growth rate varied between 0.02 and 0.65 mm.yr -1 .I calculted consequently the analysis of 50 125 micrometers each 300-1000 micrometers interval corresponds to a sample of 1 to 3 years every 0.5 to 50 years.
Detection limits are calculated from the intensity and standard deviation measurements of the blank.The limits of quantification range between 0.1µg g -1 for Sr, Al and Ba, and 2.5µg g -1 for Mg.Certified reference materials (NIST 610, NIST 612, NIST 614, MACS-1, and MACS-3) were analyzed with each series of samples, in order to determine the precision and accuracy of analytical procedures.Comparison between reference values and measured values were 130 satisfactory (Table 2) within 65-98 %.For Ba, Sr, and Mg, the reproducibility was higher than 76%.The lowest value was observed for Al (65% for MACS-1 standard).To investigate the solar forcing controls on trace elements content in the PN stalagmite, we compared the concentrations of Ba, Sr, Mg with sunspot number (solar activity- Solanki et al., 2004) and the temperature recorded from Mekelermeer core in Netherlands (Bohncke P., 1991).Continuous wavelet transform was applied on the trace element time-series data to detect any significant periodicities.These were obtained as the local maxima of the wavelet spectrum (see supplementary data).
Stable isotopes data ( 18 O) from PN stalagmite reported in Verheyden et al. (2008).The  18 O composition of PN varies between − 4 .3 and − 6 .4 ‰ (VPDB) with a mean of -5.4‰ (Fig. 4).It displays a long term increasing trend 160 from lower values (-6‰) between 12.7 and 10.7 ka BP to -5.3 ‰ between 10.7 and 7.5 ka BP and to higher values (>-5.0‰) between 6.3 and 1.8 ka BP.Lower values are observed at 10.7, between 9.5 and 9, between 8.3 and 6.2, at 5.5 ka BP and between 4.3 and 3.4 ka BP with a general increase until the end of speleothem deposition.The  18 O isotopic composition of the calcite in the Père Noël cave is largely controlled by water availability (drip rate) in the cave.
Changes in isotopic equilibrium conditions are driven by the changes in cave humidity and linked to changes in 165 precipitation and evapo-transpiration (Verheyden et al., 2008).

Processes controlling trace element contents
In previous studies, Verheyden et al., (2000Verheyden et al., ( , 2008Verheyden et al., ( , 2012) ) interpreted changes in the different PN cave parameters 170 and speleothem proxy-data in terms of changes in environment and/or climate.Higher Mg/Ca and Sr/Ca ratios were previously observed during the summer season, characterized by longer water residence times (Verheyden et al., 2008) and associated to lower water availability.Since water residence time is related with water availability, trace elements in PN speleothem probably register changes in effective precipitation, i.e., precipitation minus evapotranspiration.In this study, statistically significant positive correlations (r(Sr, Ba)=0.77,r(Mg, Sr)=0.72,r(Mg, Ba)=0.48) are found between Sr, 175 Ba and Mg over the Holocene period suggesting either a common or strongly related controlling process.Aluminum can be used to determine the variations in the detrital (non-carbonate) content in speleothems; these particles may be transported during periods of intense precipitation, which results in high drip rates (White, 1997;Schimpf et al., 2011).
In PN stalagmite, Al concentration was higher than the detection limit and its maximum values coincide with maxima in the other investigated trace elements investigated (Fig. 4).The positive correlations of Al with Mg, Ba and Sr (r = 180 0.45) suggest that Al content is controlled by the same process than the other trace elements.The δ 18 O profile has a

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Second trace element PN time-series are compared with available temperature record from Mekelermeer core in the Netherlands (Bohncke J., 1991) in order to evidence a regional temperature influence on the PN record.Both records reveal significant correlations.

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Soon et al., 2014; Chapman and Shackleton, 2000).The 960-1029 yr cycle of the speleothem could match the Eddy cycle (1000 yr) as recognized in both ice cores (Stuiver et al., 1995) and marine sediments (e.g., Chapman and Shackleton, 2000).The trace elements PN records show small peaks between 1280 and 1533 yr (Fig. 5).This periodicity is identical to the Bond cycle (1470 ± 500 yrs) detected from ice rafted debris in North Atlantic sediment cores (Bond et al., 2001).Finally the 2245-2670 yr cycle, could be related to the Bray or Halstatt cycle (2200-2400 yr) 210 that is recognized in other palaeoclimatic records (e.g., kern et al., 2012).The significant common periodicities between trace elements PN records and Solar records suggest that solar variability influenced PN trace elements content on decadal to millennial time scales.Since the changes of trace elements in the PN speleothem were formerly demonstrated as due to changes in recharge, i.e. effective precipitation, the study suggests that variations in solar activity may be a significant forcing on either the precipitation or on the soil activity or vegetational activity intensity.

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This does not necessarily mean that solar forcing was the main source of all Holocene climate variability since different dynamical processes, such as explosive volcanic eruptions, fluctuations of the ocean thermohaline circulation or internal feedbacks, might also have played an important role (Wanner et al., 2008).

Relation between trace element records and known Holocene climate events
The PN records indicate that the maxima of trace elements concentrations coincide with the cold events (Fig. 4) defined in Wanner et al. (2011), which partly coincide with the events of Bond et al. (2001).The higher positive correlations between trace elements concentrations (r=0.5-0.9)observed during cold periods which also suggest common control factors.In marine sediments Bond et al., (1997Bond et al., ( , 2001) ) revealed 1470 yrs± 500 Holocene cycles.Nine Bond cycles were detected over the Holocene and peaked around 0.4, 1.4, 2.8, 4.3, 5.9, 8.1, 9.4, 10.3 and 11.1 ka BP (Bond et al., 1997(Bond et al., , 2001;;Wanner and Bütikofer, 2008b).These events, attributed to lower solar activity, most probably triggered the slowdown of the thermohaline ocean circulation over the North Atlantic and European regions (Renssen et al., 2007).Figure 7 shows a comparison of the trace elements concentrations in the PN stalagmite and the frequency of warm/cold and wet/dry events in the Northern Hemisphere (Wanner et al., 2014).In the PN stalagmite, we identify several periods of dry climate, these are centered at 10.5, 9.3, 8.2, 6.3, 5.4, 4.6 and around 2.7 ka BP, and their duration ranges from 100 to 400 yr (Fig. 7).These intervals characterized by higher trace elements contents in PN record were interpreted as dryer periods.

Younger Dryas and Early Holocene
The PN stalagmite starts its growth on the underlying limestone block at 12.7 ka BP, indicating favorable climatic and environmental conditions for stalagmite growth.The oldest part of the PN stalagmite, from 12.7 to about 12.1 ka BP, is characterized by the lowest contents of trace elements and low  18 O, suggesting wet conditions (Fig. 4).The larger diameter of the stalagmite compared to its mean diameter suggests that there is enough water to flow down on the flank of the stalagmite and to precipitate calcite.The inception of speleothem growth is in agreement with the beginning of the cold Younger Dryas (YD) event (12.9-11.7 ka BP).All proxies measured in the PN stalagmite suggest that a humid period occurred between 12.7 and 12.1 ka BP.This is in agreement with the warm climate during the early YD (12.9-12.15ka BP) found in lake sediments from Northern Spain, Norway and Western Germany (Baldini et al., 2015;Bakke et al., 2009;Brauer et al., 2008).The high-resolution records from those three lakes suggested that warming climate associated with the early YD may be related to local climate change (Lane et al., 2013;Baldini et al., 2015).Our high-resolution trace elements from PN stalagmite consolidate the concept that the early YD (12.9-12.15ka BP) was warm in SW and NW Europe.The period, from 12.1 to about 11.7 ka BP, is characterized by a gradual increase of trace element concentrations, suggesting a climate change from wet to dry conditions (Fig. 4, 7).
The δ 18 O values increase from -6.3 to -5.5 ‰ suggests relatively dry conditions in agreement with trace element concentrations (Fig. 4).European archives (lake and speleothem records) indicate that a cooler and/or drier climate characterized the YD termination (12.1-11.7 ka BP) (e.g., Genty et al., 2006;Von Grafenstein et al., 1999).This rapid climate shift attests for the major influence of the North Atlantic Ocean circulation on the YD/Holocene climate transition (Pearce et al., 2013;Baldini et al., 2015).During the Early Holocene, i.e. before 7 ka BP, the amplitude of the frequency of warm/cold or dry/ wet events was from the rapidly melting ice sheets of the Northern Hemisphere (Carlson et al., 2014).The Holocene started about 11.7 ka BP with a transition from a cool YD to a wet and/or warm climate state.In the PN stalagmite, low trace element contents suggest that wet conditions persisted at the beginning of the Holocene (Fig. 4).The δ 18 O values decrease from -5.5 to -6 ‰ suggests relatively wet conditions in agreement with trace elements concentrations.PN speleothem suggests a wet Early Holocene with dryer conditions from 10.7 to 10.3, at 10.0, at 9.7, at 9.2 and from 8.5 to 8.2 ka BP (Verheyden et al., 2014).Trace element contents in the PN stalagmite display significant variability during the Early Holocene, with three maxima observed around 10.5, from 9.5 to 9.2 and around 8.2 ka BP (Fig. 4, 7).The positive correlations (r=0.47-0.98)were observed between trace elements concentrations during those periods which confirms common control factors.The covariance between geochemical proxies support, as explained in Verheyden et al.

260
(2008), their interpretation in terms of dry-wet changes with higher trace elements and higher δ 18 O values linked to drier conditions.The drying is in agreement with a decrease in speleothem growth rate and diameter.Moreover, a denser calcite is deposited at 10.4 ka, between 9.5 and 9.2 and between 8.4 and 8.2 ka BP (Fig. 4).The highest concentrations of trace elements in PN correspond to low sunspot numbers and to cold periods (Fig. 4), as defined in Bond et al., (2001).During the three intervals (i.e., around 10.5, between 9.5 and 9.2 and between 8.4 and 8.2 ka BP),

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the wavelet spectrum of trace elements shows that the solar imprint is well present in the PN stalagmite records during the Early Holocene (Fig. 6).Those three intervals may correspond to Bond cycles that caused by the lower solar activity additionally triggered slowdown of the thermohaline ocean circulation in the North Atlantic and European regions (Renssen et al., 2007).Continuous cyclic periods of around 500 and 1000 yrs are presented during the interval 10.7-10.3ka BP.For the intervals from 9.5 to 9.2 and between 8.4 and 8.2 ka BP, continuous cyclic periods of around 270 80, 130, 500, 1000, 1300-1500 yr are present.Ice, speleothems and sediment records from the North Atlantic region demonstrate that the Early Holocene period was relatively stable and interrupted by periods of short-lived cooling such as: 10.3 ka (Bjorck et al., 2001), 9.3 ka (e.g., Boch et al., 2009;Rasmussen et al., 2007;von Grafenstein et al., 1999) and 8.2 ka event (e.g., Alley et al., 1997;Ellison et al., 2006).Solar variability and/or changes in Atlantic Meridional Overturning Circulation have been proposed as causes of climate changes in the Early Holocene (Björck et al., 2001; 275 Marshall et al., 2007;Plunkett and Swindles, 2008).A cold event around 8.2 ka BP has been recorded in the North Atlantic and Northern Europe (Alley et al., 1997;Barber et al., 1999;Clark et al., 2001).This event has been well recorded in PN stalagmite and discussed in detail in Verheyden et al., (2014).The correlation between trace elements and sunspot number suggests that periods of lower intensity of solar irradiation were probably accompanied by drier climate in NW Europe.However, solar forcing cannot alone explain the variability of the Early Holocene signal.

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Previous studies in ice cores (e.g.Alley et al., 1997) or lake sediments (e.g., Prasad et al., 2006), demonstrated that the climate changes in Western Europe and Greenland are similar during the Early Holocene and may be caused by changes in solar activity, and changes in North Atlantic thermohaline circulation.

Mid and Late Holocene
The interval from 8.1 to about 7 ka BP is characterized by low contents of trace elements and low δ 18 O values 285 suggesting relatively wet conditions.This phase coincides with the interval of maximum frequency period of warm and wet events detected in the Northern Hemisphere (Wanner et al., 2014) (Fig. 7).The interval between about 7 and 4.2 ka BP "called Holocene Climate Optimum" is characterized by higher summer temperatures in the Northern Hemisphere (e.g., Alverson et al., 2003).High trace elements values were detected in PN stalagmite during three intervals, from 6.4 to 6.2, 5.55 to 5.4 and from 4.7 to 4.5 ka BP (Fig. 4).The period between 7.3 and 6.0 ka BP 290 corresponds to the warmest period of the Holocene in Greenland (Jonhsen et al., 2001).From 6.4 to 6.2 ka BP a high positive correlation (r=0.45-0.95) was observed between element trace concentrations confirming dryer conditions.
The drying is in agreement with a decrease in the speleothem growth rate and diameter.The high concentrations of trace elements in PN correspond to low temperature and sunspot number (Fig. 4).This phase coincides with the period of maximum frequency of dry events detected in the Northern Hemisphere (Wanner et al., 2014) and with a cold event 295 as defined in Wanner et al., (2011).Between 5.5 and 5.4 ka BP, the trace elements (high values) display an anticorrelation with temperature and sunspot number (low values) suggesting relatively dry conditions (Fig. 4).During this period, trace elements present frequencies corresponding to the Gleissberg cycle (70-100 yr), Hale cycle (130 yr), de Vries cycle (200-210 yr), 500 unnamed cycle and Eddy cycles (1000 yr) (Fig. 6).
High trace elements and δ 18 O values were detected in the PN stalagmite from 4.7 to 4.5 ka BP corresponding to a dry 300 period.The highest positive correlation (r=0.78-0.97)observed between trace element concentrations during this period confirms dry conditions.The period between 4.7 and 4.5 ka BP corresponds to the cold event (4.6-4.8)defined by Wanner et al., (2011) and coincides roughly with Bond events.This phase coincides with the period of decrease in frequency of wet events and increased of dry events detected in the Northern Hemisphere (Fig. 7).In addition, our spectral analysis shows the prominence of 63-80, 133-140, 198-220, 514-561, and 912-1029 year periodicities in the 305 PN stalagmite (Fig. 6).The periodicities found here suggests evidence for solar-forced climate change because they match the ranges of cycles in solar reconstructions.General dry conditions as suggested by PN proxies were observed from 3 ka BP to the end of the speleothem 310 deposition at 1.8 ka.The final dry phase may be related to the cool event showed by Wanner et al. (2011) that occurred between 3.3 and 2.5 ka BP and corresponds with Bond event (Fig. 4).This dry period also coincides with low temperature and solar activity (Fig. 4).This period was caused by an abrupt decrease of solar activity and has been reported from different proxies in Greenland and Europe (e.g., van Geel et al., 1996;Blaauw et al., 2004;Plunkett and Swindles, 2008;O'Brien et al, 1995).The overall good agreement of the timing of the dry/wet or cold phases recorded 315 in the PN stalagmite with the timing of the Wanner and Bond events (Wanner et al., 2001(Wanner et al., , 2014;;Bond et al., 1997Bond et al., , 2001) ) confirms the potential of the PN speleothem to reconstruct the Holocene paleoclimate.

Conclusion 320
We have shown that the high-resolution trace element records obtained by LA-ICP-MS from the PN stalagmite provide a detailed paleoclimate and/or paleoenvironment record of Northwestern Europe through the Holocene.The strong covariation of trace elements (Ba, Sr, Mg and Al), and with δ 18 O, confirms a common or strongly related controlling process.Based on trace element time-series we demonstrate that several events at 10. 3, 9.3-9.5, around 8.2, 6.4-6.2, 4.7-4.5, and around 2.7 ka BP alternate with periods of relatively stable and wet/warmer climate.These 325 intervals coincide with the cold events defined in marine and continental archives.The trace element time-series of the PN speleothem reveals a significant correlation with sunspot number records, suggesting some solar forcing in the PN trace elemental records.This observation is confirmed by wavelet analyses that reveal common solar periodicities (Gleissberg cycle, de Vries cycle, unnamed 500 year, Eddy cycles, and Hallstatt cycle) in agreement with those recognized in the North Atlantic marine cores and the Greenland ice cores, as well as some other terrestrial Holocene Clim.Past Discuss., https://doi.org/10.5194/cp-2017-91Manuscript under review for journal Clim.Past Discussion started: 11 July 2017 c Author(s) 2017.CC BY 4.0 License.trace elements time-series of the PN stalagmite to identify solar-type periodicities in the stalagmite record.
Clim.Past Discuss., https://doi.org/10.5194/cp-2017-91Manuscript under review for journal Clim.Past Discussion started: 11 July 2017 c Author(s) 2017.CC BY 4.0 License.directly through the overlying limestone.An approximately 40-cm-thick woodland soil covers the host rock limestone.The mean annual precipitation of the nearby meteorological station (Lessive, 3 km NE of the cave), measured over the 110 period 1980-1998, is 826 mm.The mean temperature inside the cave is 9 °C (varies between 8.5° and 9.2 °C) Clim.Past Discuss., https://doi.org/10.5194/cp-2017-91Manuscript under review for journal Clim.Past Discussion started: 11 July 2017 c Author(s) 2017.CC BY 4.0 License.The Ba, Sr, Mg, and Al records in PN are composed of nearly six-hundred independent points.Profiles of Mg, Sr, 145 Clim.Past Discuss., https://doi.org/10.5194/cp-2017-91Manuscript under review for journal Clim.Past Discussion started: 11 July 2017 c Author(s) 2017.CC BY 4.0 License.positive correlation with Sr, Ba, and Mg (r= 0.45-0.70),suggesting a common control.Changes in element traces content in PN stalagmite are interpreted as due to changes in water residence time linked to changes in water availability.This explains the covariation over much of the Holocene period of the geochemical parameters in the PN speleothem. 185 and are in agreement with decadalcentennial scale variability in Holocene climatic records from widely dispersed geographic regions.For example, the 63-80 yr interval is similar to the Gleissberg cycle (70-100 yr) whereas the 133-140 yr frequency interval corresponds 200 to the Hale cycle (130 yr).The 198-220 yr cycle of PN record is close to the de Vries (200-210 yr) solar cycle Clim.Past Discuss., https://doi.org/10.5194/cp-2017-91Manuscript under review for journal Clim.Past Discussion started: 11 July 2017 c Author(s) 2017.CC BY 4.0 License.
From 4.5 to 3.1 ka BP, general climatic conditions favor the speleothem deposition.Low values for trace elements and for δ 18 O indicate relatively wet and temperate/warm conditions.

Figure 2 :
Figure 2: Age versus depth plots and average growth rate of the PN stalagmite.The black line represents the age model.Grey lines indicate the age dating uncertainties.Red and black dots present the U/Th dates.

Figure 3 :
Figure 3: Stalagmite PN laser ablation Sr (red line), Ba (green line), Mg (black line) and Al (blue line) concentrations record for 64 cm-length.The measurement was made with 300-1000 µm intervals (light color).Dark line color presents mean of three measurements.

Figure 6 :
Figure 6: Continuous wavelet transform spectra for sunspot number, temperature, Ba, Sr, Mg, spectral power (variance) is shown by colors ranging from deep blue (weak) to deep red (strong).

Figure 7 :
Figure 7: A comparison between PN trace elements contents (Sr = red line; Ba = green line; Mg = black line; and Al = blue line), frequency of warm/cold and wet/dry events in the Northern Hemisphere as defined by Wanner et al. (2014).The blue horizontal bars mark cold events.

Table 1 :
Mass-spectrometric U/Th age data for the PN speleothem.

Table 2 :
Comparison between reference and measured values for five certified reference materials.