Evidence of Suess solar-cycle bursts in subtropical Holocene speleothem δ18O records

Several studies indicate that changes in solar activity may have driven Holocene subtropical monsoon variability on decadal and centennial timescales, but the strength and nature of this link remains debated. In this study, we combine a recent mapping of the Holocene solar-cycle activity with four subtropical speleothem delta O-18 records, which allows a strong test of the link between solar activity, monsoon activity (or intensity), and the hydrological cycle. This is possible because the speleothem delta O-18 records mainly reflect changes in local rainfall composition, which is controlled by changes in total moisture loss along the atmospheric transport path and monsoon intensity. We find that the spectral density distributions of the speleothem records exhibit particularly significant similar to 210 yr cyclicities that tend to coincide in time with the three Suess solar-cycle bursts, i.e. intervals around 1850-3200 BP, 4500-5700 BP, and 7750-8850 BP when the similar to 210 yr solar cycle was particularly strong. The speleothems from Dongge Cave (China) and Sofular Cave (Turkey) appear to have recorded all three Suess bursts, whereas the speleothems from Heshang Cave (China) and Pink Panther Cave (southwestern USA) only recorded the first and last Suess bursts, and the middle Suess burst, respectively. The temporal relationship between the Suess solar cycle and particularly significant 210 yr oscillations in the speleothem delta O-18 records therefore supports the notion that solar variability played a significant role in driving centennial-scale changes in the hydrological cycle in the subtropics during the Holocene.