East Asian monsoon variability since the Mid-Holocene recorded in a high-resolution, absolute-dated aragonite speleothem from eastern China

Paleoclimatic conditions associated with the East Asian monsoon are reconstructed for the Mid- to Late-Holocene using δ¹⁸O values (819 measurements) from a precisely dated (10 ²³⁰Th dates) aragonite stalagmite from Lianhua Cave, Hunan Province, China. δ¹⁸O values (- 1.6‰ to - 7.0‰) are interpreted to reflect the precipitation amount effect related to the strength of summer monsoonal circulation. Throughout this period, the intensity of East Asian summer monsoonal circulation declined in response to changes in insolation and a southward shift in the Intertropical Convergence Zone (ITCZ). Punctuating this first-order trend are abrupt millennial- to decadal-scale fluctuations, the most prominent of which occurred around 3337 ± 5 yr BP and records a dramatic weakening in summer monsoonal circulation that coincides with the beginning of Neoglacial conditions. Comparisons between the δ¹⁸O values of stalagmite A1 and previously published data from stalagmite HS-4 from Heshang Cave and stalagmites D4 and DA from Dongge Cave, China, demonstrate a similar regional response to changes in East Asian monsoonal circulation. Several spectral analysis techniques and wavelet analysis were applied to these stalagmite records to evaluate the nature and character of cyclicity in the East Asian monsoon during the Holocene. Multi-Taper Method (MTM), Lomb-Scargle, and Single Spectrum Analysis (SSA) results reveal common periodicities that are unlikely to be artifacts of any single technique. The periodicities expressed in the stalagmite δ¹⁸O records occur at both solar and non-solar frequencies and support previous interpretations that variability in monsoonal circulation responds to both solar forcing and internal climatic mechanisms. Wavelet analysis demonstrates that some of these frequencies are intermittent and recur at semi-regular intervals, which may indicate long-term cyclicity that is unconstrained by the chronology of the record.