Evidence for solar cycles in a late Holocene speleothem record from Dongge Cave, China

Abstract

The association between solar activity and Asian monsoon (AM) remains unclear. Here we evaluate the possible connection between them based on a precisely-dated, high-resolution speleothem oxygen isotope record from Dongge Cave, southwest China during the past 4.2 thousand years (ka). Without being adjusted chronologically to the solar signal, our record shows a distinct peak-to-peak correlation with cosmogenic nuclide 14C, total solar irradiance (TSI), and sunspot number (SN) at multi-decadal to centennial timescales. Further cross-wavelet analyses between our calcite δ18O and atmospheric 14C show statistically strong coherence at three typical periodicities of ~80, 200 and 340 years, suggesting important roles of solar activities in modulating AM changes at those timescales. Our result has further indicated a better correlation between our calcite δ18O record and atmospheric 14C than between our record and TSI. This better correlation may imply that the Sun–monsoon connection is dominated most likely by cosmic rays and oceanic circulation (both associated to atmospheric 14C), instead of the direct solar heating (TSI).

Cyclic changes of Asian monsoon intensity during the early mid-Holocene from annually-laminated stalagmites, central China

“…This approach might result in a less strict constraint on the climate dynamics regardless of the statistically improved correlation between the solar and climate indicators (Haam and Huybers, 2010). Several factors might plague the assessment of the suneclimate relationship, including age uncertainties and the signal/noise ratio of the record, the accuracy of the solar proxies, and the strength of climate backgrounds as discussed in Duan et al (2014). In the late Holocene, compelling evidence of a direct, oneto-one link between the Asian monsoon (AM) and solar output has been recently presented by a chronologically-untuned speleothem record (Duan et al, 2014).…”

“…Several factors might plague the assessment of the suneclimate relationship, including age uncertainties and the signal/noise ratio of the record, the accuracy of the solar proxies, and the strength of climate backgrounds as discussed in Duan et al (2014). In the late Holocene, compelling evidence of a direct, oneto-one link between the Asian monsoon (AM) and solar output has been recently presented by a chronologically-untuned speleothem record (Duan et al, 2014). However, the boundary conditions in the early Holocene were strikingly different from those in the late Holocene, when the continental ice-sheets exerted an appreciable impact on the AM (Fleitmann et al, 2003).…”

Decadal resolution record of Oman upwelling indicates solar forcing of the Indian summer monsoon (9–6 ka)

“…However, within the limits of our age model, comparison of the amplitude variations in the filter outputs from both SST time series and the TSI record of Steinhilber et al (2012), filtered on the ∼ 85-year Gleissberg bandwidth, apparently indicates synchrony of our SST records and TSI with maximum amplitude modulations of all three records centred at ∼ 7.4 ka BP. Our new high-resolution record of summer and upwelling SST therefore provides further strong evidence that solar forcing persistently modulated ISM variability during the early to mid-Holocene after the summer insolation maximum, previously found from speleothem (Neff et al, 2001;Burns et al, 2002;Fleitmann et al, 2003;Dykoski et al, 2005;Wang et al, 2005;Duan et al, 2014) and marine records (von Rad et al, 1999;Wang et al, 1999;Gupta et al, 2005).…”

“…In fact, the overall error of the reservoir correction of ±31 years is close to the observed periodicities, which might give an indication of why we found the Gleissberg cycle but not the longer-period (∼ 200-210 years) de Vries solar cycle. However, Duan et al (2014) showed with a speleothem record from Dongge Cave (China), that coherency of eastern Asian monsoon precipitation and the solar Gleissberg cycle is persistent over the last 4 kyr, whereas coherency with the de Vries cycle was only observed over a short 1 kyr long period. Other Holocene Asian monsoon records also showed periodicities similar to the Gleissberg cycle, while lacking the longer de Vries cycle (e.g.…”

Speleothem stable isotope records for east-central Europe: resampling sedimentary proxy records to obtain evenly spaced time series with spectral guidance

“…However, a problem remains: the transformation of unevenly spaced data to a temporally equidistant time series is required in order for it to be suitable for the application of, for example, wavelet spectrum, multitaper analysis, and simple smoothers (Hammer, 2017). In the case of unevenly spaced sedimentary records, the required preprocessing step is most commonly performed using linear (e.g., Holmgren et al, 2003, Lachniet et al, 2004, or nonlinear interpolation techniques (e.g., Ersek et al, 2012), rescaling of the data (e.g., Deininger et al, 2017), or by insufficiently documented methods (e.g., McCabe-Glynn et al, 2013;Duan et al, 2014). A more complex approach combining spline smoothing and linear interpolation has been presented in a multi-paleoproxy study, where in addition the spectral characteristics of the data were assessed using multiple methods as well (Cosford et al, 2008).…”