CLIMATE VARIABILITY DURING THE LITTLE ICE AGE CHARACTERIZED BY A HIGH-RESOLUTION STALAGMITE RECORD FROM DONGGE CAVE, GUIZHOU

High-resolution and precisely dated climate records are important to further investigate the climate variability during the Little Ice Age(LIA). On the basis of 24 ²³⁰Th dates and 1165 oxygen and carbon isotope data obtained from stalagmite D41(sample length for 11.7 mm) from Dongge Cave(25°17'50.5“N, 108°02'67“E), Libo, Guizhou, we present here a high-resolution(average resolution better than 0.5 year) δ¹⁸O and δ¹³C record across a large portion of the LIA(1400~1880 A.D.). The δ¹⁸O values in the D41 record vary from -8.19 % to -6.64 % with the average value of -7.52 %. There exists a significant positive correlation between the δ¹⁸O and δ¹³C(Pearson linear correlation coefficient r=0.7882, n=1165, p < 0.001). The δ¹⁸O record shows low excursions during the periods of 1450~1555 A.D. and 1630~1780 A.D., and high excursions during 1400~1450 A.D. and 1555~1630 A.D., with interannual-decadal fluctuations between throughout the record. Power spectrum analysis of the D41 δ¹⁸O revealed periodicities of 160, 11.5 and 9 years similar to solar radiation cycles, as well as periodicity of 4~7 years similar to the ENSO cycle. Additionally, a 14~16-year periodicity appears to be prominent, which may reflect the influence of sea-air circulations and other interaction between different Earth’s climate systems. In principle, the lower δ¹⁸O in the D41 record may mainly reflect larger spatially integrated rainfall between the cave site and moisture source along water vapor transmission path. The secondary fluctuations of the D41 δ¹⁸O variance may response to large-scale volcanic and drought events. A close look at different stalagmite δ¹⁸O records during the Chongzhen Drought(1628~1643 A.D.) reveals a drought/wet boundary in line with the historical documents. We suggest that the significant differences of δ¹⁸O in stalagmites could be explained by the change of spatial integrated rainfall between the cave site and its upstream rainfall along the moisture transmission path. As such, the high excursions observed in cave δ¹⁸O records from northern China, compared with the absence of the equivalent events in cave δ¹⁸O records from southern China during the Chongzhen Drought event, suggest that the rainfall reduce during the event occurred mainly between the northern and southern cave sites, broadly consistent with the historical documents. Moreover, observations of the temporal and spatial difference between different stalagmite δ¹⁸O records call for a caution to use a single stalagmite δ¹⁸O record as an indicator of Asian Monsoon intensity on annual to decadal timescales.