Affiliation:
1. Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China
2. CAS Center for Excellence in Life and Paleoenvironment Beijing China
3. Key Laboratory for Humid Subtropical Eco‐geographical Processes of the Ministry of Education Fujian Normal University Fuzhou China
4. Institute of Geomechanics Chinese Academy of Geological Sciences Beijing China
5. National Museum of China Beijing China
Abstract
AbstractThe reasons for covariations of speleothem δ13C and δ18O remain controversial, primarily due to the limited high‐resolution stalagmite records that can be compared with meteorological data. This study presents δ13C and δ18O records of two coeval, annually laminated stalagmites (TS9701 and TS9501) spanning the past ∼2000 years from Shihua cave, Beijing, northern China. The low correlation between stalagmite TS9701 records, with annual resolution, and local annual precipitation as well as mean annual temperature on interannual to decadal scales indicates that the positive covariations of δ18O and δ13C in TS9701 are partly attributed to kinetic isotope effects caused by rapid CO2 degassing. Isotopic disequilibrium between HCO3−(aq) and drip water, induced by prior calcite precipitation on cave ceiling and stalactite surface, is another potential contributing factor. δ18O and δ13C exhibits distinct patterns on multidecadal to millennial timescales. δ18O records show notable centennial variability, aligning with El Niño‐Southern Oscillation cycles. In contrast, δ13C profiles reveal a decreasing trend during the first ∼750 years, followed by an increasing trend. Prior to 1588 AD, variations in δ13C broadly correspond to changes in warm season temperature and/or moisture on centennial scale. Both δ13C records show an abrupt enrichment between 1588 and 1654 AD. Historical documents indicate that this anomaly is likely attributed to coal mining and resultant deforestation around Shihua cave during late‐Ming and early‐Qing Dynasties. In summary, while isotopic disequilibrium can cause high‐frequency covariations of speleothem δ18O and δ13C, it does not erase the imprints of climate changes and human activities on multidecadal to millennial timescales.
Funder
National Natural Science Foundation of China
Publisher
American Geophysical Union (AGU)
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Atmospheric Science,Geophysics