Correlation between oxygen and carbon isotopes of speleothems from Tian'e Cave, central China: Insights into the phase relationship between Asian summer and winter monsoons

摘要

The correlation of East Asian summer and winter monsoons (EASM and EAWM) is believed to be variable at various timescales and under different climate backgrounds. In order to address this issue, high-resolution delta O-18 (depleted values indicating a strong EASM) and delta C-13 records (depleted values representing a weak EAWM) from three stalagmites, covering Marine Isotope Stages (MIS) 4 and 3, are reconstructed from an alpine cave in central China During MIS 4, millennial-scale changes are clear in delta O-18 and delta C-13 records, while the delta C-13 is only characterized by centennial-scale variability across MIS 3. Changes in these speleothem delta C-13 records are supported by pollen records from the same area, which suggested millennial-scale alternations between conifer and deciduous broadleaf forests during MIS 4 and a stable C3-type vegetation in MIS 3. After detrended, delta O-18 changes are positively correlated with the delta C-13 record at a centennial scale, indicating an anti-phase of EASM and EAWM. In early MIS 4, however, an in-phase relationship of EASM and EAWM can be observed at a millennial scale. Thus, an anti-phased EASM/EAWM can be expected at a centennial scale, while a complicated correlation is seen at a millennial scale. These results imply a variable EASM/EAWM phase relationship under varying climatic conditions through the geological records and at different timescales.